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Structural Connections for Precast Concrete Buildings - Review of Seismic and Other Design Provisions in Various International Codes - An Overview

Precast concrete is significantly being used in earth-quake resisting structures in many parts of the world. Due to the lack of understanding of the basic nature

of seismic behavior, the precast concrete structures were viewed with scepticism in seismic regions. Some countries considered the use of precast concrete in earthquake re-sisting structures with suspicion because of their bad per-formance in major earthquakes. Examples of poor behav-ior of precast concrete building structures are during 1976 Tangshan (China), 1985 Michoacan (Mexico), 1988 Armenian, 1994 Northridge and 1999 Kocalli earthquakes due to im-proper design and detailing of ductile element, inadequate diaphragm action, poor joint and connection details, inadequate separation of non-structural elements and inadequate sepa-ration between structures. These are presented in the state-of- the-art report by Park and co-workers (fib, 2003).

Countries like Japan, Canada, Italy, Chile, Mexico, New Zealand and USA, which are well known for high seismici-ty, adopt precast concrete construction practices. In these countries, the design and construction practices are usually supported by the results from experimental investigations.

Recent experimental investigations have mainly focussed on developing techniques to reduce damage in structures using precast elements. For example, with reference to New Zealand, University of Canterbury conducted tests to design connection details between hollow-core floors with beams and walls that could sustain up to 6% of inter-storey-drift.

Perspective of the past:

The evolution of the precast industry in seismically active regions of the United States and other parts of the world, with an emphasis on the need to develop technology compatible with precast concrete construction, are discussed and pre-sented by Englekirk21. It was reported that precast concrete construction is extensively used and is being promoted in Japan on high rise buildings even though Japan is not hav-ing a specific national design standard on precast concrete structures. The technical justification for precast systems in Japan is provided by experimental studies. Further research

on the behavior of precast concrete elements and structures under seismic loading is reported in references 15-19.

To limit the possibility of progressive collapse and to obtain a monolithic action, structural integrity is taken care of in precast concrete structures by means of longitudinal and transverse ties connecting members to a lateral load re-sisting system. Forces shall be permitted to be transferred between members by grouted joints, shear keys, mechan-ical connectors, reinforcing steel connections, reinforcing topping, or a combination of these means. The adequacy of connections to transfer forces between members is deter-mined by analysis or by test. In designing a connection using materials with different structural properties, their relative stiffnesses, strengths, and ductilities are considered.

Provisions related to seismic design considerations are continuously being improved and incorporated in different international standards. Development in the codal provisions and guidelines of American and New Zealand construction practice is discussed.

A brief history of building code provisions for precast / prestressed concrete in the United States was presented by D’Arcy, et al.22, in which it was reported that the first set of specific design provisions ever developed in the United States for precast concrete structures in regions of high seismicity appeared in NEHRP17 Recommended Provisions. The NEH-RP provisions presented two alternatives for the design of precast lateral-force-resisting systems: one, emulation (same as) of monolithic reinforced concrete connection and the other, use of the unique properties of precast concrete el-ements interconnected predominantly by dry connections (jointed precast). For emulation of the behavior of monolithic reinforced construction, two alternatives were provided: struc-tural systems with “wet” (ductile) connections and those with “strong” (elastic) connections. The design provisions for precast structures in high seismic regions were expanded in NEHRP (FEMA, 2001) Provisions19. The seismic-force re-sisting system for high seismic regions suggested in NEH-RP (FEMA, 2001) provisions19 are special moment resisting frames and special structural walls with superior type dry

C.A Prasad1, Pavan Patchigolla2

1Director, METEY Engineering & Consultancy Pvt. Ltd.2Structural Engineer, METEY Engineering & Consultancy Pvt. Ltd.

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connections. The ACI 318-02, introduced design provisions for precast concrete structures located in regions of moderate to high seismic risk or assigned to intermediate or high seis-mic design categories. Provisions for non-emulative (jointed precast) design of precast wall systems were not included in ACI318-02.

A perspective on the seismic design of precast concrete structures in New Zealand is presented by Park14. Trends and developments in the use of precast reinforced concrete in New Zealand for floors, moment resisting frames and struc-tural walls of buildings with aspects of design and construc-tion, particularly the means of forming connections between precast concrete elements were discussed and presented by Park14.

Seismic performance of precast concrete systems-Codal provisions

Failure of precast concrete buildings in 1964 Alaska, 1976 Tangshan (China), 1988 Armenia, 1994 Northridge, 2001 Bhuj and 2008 Wenchan (China) earthquake was mainly due to collapse of floors for some or other reasons.

One of the main reasons of collapse of floors were loss of seat due to failure of support system, poor connections, excessive deformation of support system (beam elongation) and deformation incompatibility between the support and the floor. A possible solution to avoid these failures can be by providing the sufficient seating incorporating the effect of all possible movements into account.

Fig. 1 shows such detail of required bearing length at the support suggested by NZS 3101: 2006.

Fig. 2 and Fig.3 show the alternative special reinforcing to transfer the shear force and support precast concrete floor units in the event of loss of bearing. Continuous beam rein-forcement will transfer shear force to column in case of loss

of seating, the other alternative with hanger stirrups in the vicinity of support can also help in the transfer of shear force.

Fig. 1Required bearing length at the support of a member in relation to its clear span

Fig. 3 Alternate continuous reinforcement through the beam at the level of bottom of floor and in the topping of slab floor to support precast concrete floor units.

Fig. 2 Alternate continuous reinforcement through the beam at the level of bottom of floor to support precast concrete floor units.

Connections and Bearing

The codes permit a variety of methods for connecting members in plane and out of plane. These are grouted joints, shear keys, mechanical connectors, reinforcing steel con-nections, reinforced topping, or a combination of these. Codes suggest a minimum bearing length after considering for tol-erances, as the clear span/180 from the edge of the support to the end of the precast member. However it should not be less than 50mm for solid or hollow core slabs and 75mm for beams or stemmed members as per ACI 318-0832. NZS 3101 provides bearing width for hollow core slab as 75mm. Codes have suggested to have a clear distance of 15mm from the unarmored edges and make allowances for concrete cover. Required length of bearing at the support of a member in relation to its clear span is illustrated in Fig. 3. Connections that rely solely on friction caused by gravity forces are not permitted by codes. For hollow-core slabs, the floor should be mounted on low friction bearing strips with a coefficient of friction less than 0.7 and a minimum width of 50mm, as per NZS 3101.

Structural Integrity

Structural integrity is necessary to improve the redun-dancy and ductility in structures. This also helps to avoid col-lapse of the structures in the event of damage to major sup-porting element or an abnormal loading event by maintaining overall stability. Codes suggest provisions for precast concrete structures to achieve structural integrity to the same extent as of monolithic structures. Tension ties are provided in the transverse, longitudinal and vertical directions and around the perimeter of the structure to effectively tie precast concrete elements together. This will also achieve the diaphragm ac-tion of the floor and a seismic load path in the structure.

Diaphragm Action

Precast concrete floor could not transmit in plane force induced by earthquakes to lateral load resisting system ad-equately and failed during past earthquakes. Codes have dealt with the design of precast concrete diaphragms similar to the cast-in-place diaphragms. Design and detailing pro-visions for both un-topped and composite diaphragms with topping are given in the codes. Codes have suggested the minimum thickness of topping to be 50mm for 20mm cover and 25MPa strength of concrete. It is further needed to be increased depending on the size of reinforcement and clear cover to be used.

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ACI 318-08 recommends minimum thickness of topping to be provided on precast concrete or roof elements, acting as structural elements and not relying on composite action to be 67.5mm.

NZS 3105 relates the minimum thickness of topping with the diameter of bars used. Minimum thickness of topping for 6, 10, 12 and 16 mm stirrups, ties or spirals used is 50, 75, 90 and 105 mm respectively. It is also suggested that if the cover is greater than 20mm then the thickness of topping should be increased by the amount of additional cover.

Deformation compatibility of flooring systems

Elongation of plastic hinge regions in beams result in the deformation incompatibility of floors with the support sys-tem. This phenomena is much observed in the collapse of hollow-core floors in 1988 Armenian and 1994 Northridge earthquakes. To overcome this incompatibility issue and avoid the brittle failure, NZS3101 have suggested for the pre-cast floor systems to be designed to have adequate ductili-ty. The code has suggested the connection details that have performed well in analytical and experimental investigations.

Precast Concrete Frame and Wall Systems

Codes have suggested the design and detailing of these systems to be same as cast-in-place system with taking particular care in designing the connection to emulate sim-ilar behavior. Precast concrete frame systems composed of concrete elements with ductile connections are expected to experience flexural yielding in connection regions. ACI /318-08 has recommended the reinforcement provisions and type of mechanical splices to achieve the monolithic behavior of connections.

Design for the structural purpose:

The main purpose of the structural connections is to transfer forces between the precast concrete elements in order to obtain a structural interaction when the system is load-ed. By the ability to transfer forces, the connections should secure the intended structural behavior of the superstruc-ture and the precast subsystems that are integrated into it. This could for instance be to establish diaphragm action in precast floors and walls, or cantilever action in precast shafts. For this reason, the structural connections should be regarded as essential and integrated parts of the structural system should be designed accordingly and with the same care as for the precast concrete elements. It is insufficient just to consider the connections as details for site erection. The advantages that normally are obtainable with prefabri-cation can be lost with an inappropriate design and detailing of the structural connections.

Ductility

Connections should preferably behave in a ductile man-ner. Ductility can be defined as the ability to have large plastic deformations before failure. In structural materials, ductility is measured as the magnitude of the deformation that occurs between yielding and ultimate failure. Ductility in building frames is usually associated with moment resistance. In concrete members with moment-resisting connections, the

flexural tension is normally resisted by reinforcing bars. Ductile joints can be achieved by giving the brittle parts of the joint an extra capacity, for example by calculating with re-duced allowable stress in these components. Typical brittle components are welds, short bolts in tension, bolts subject-ed to shear, reinforcement anchorage zones, etc.

Tests are conducted at department of civil engineering, University of Manitoba on precast concrete shear wall con-nections. The observations / conclusions thereon are as fol-lows:1) All connections tested were capable to withstand large

nonlinear deformations well beyond first yield with very good energy absorption. Connections with bonded mild reinforcement had ductility around 5. Post-tensioned connections had ductility of 6.

2) Debonding of continuity element across the connection significantly enhanced the response of the connection in terms of energy dissipation and ductility.

3) Presence of shear keys across joint interface limited the slip mechanism which is desirable in the overall precast wall connection response.

4) Seismic response up to a ductility of three could be re-sisted by all the tested configurations without any appar-ent damage to the precast wall connection. This level represents typical seismic demand for low to moderate seismicity.

Movements

Connections must not hamper necessary movements in the structure. Necessary movements will in most cases be the deformation of beams and slabs due to loads and/or pre-stressing forces. Typically this problem arises when a verti-cal facade panel is connected to a beam or slab somewhere in the span (away from the support). If the connection detail makes the vertical movement of the beam or slab impossible, this may cause damage to the connection detail itself, or to the elements. Even if there is no damage, unwanted forces may be introduced in the elements, causing unwanted de-formations. The solution is to construct the connection detail with a sliding arrangement, or it can be made as a hinge.

Types of Joints

The most serious problem facing the precast industry is finding a reliable and economic method to join prefabricated members. Connections or locations of high stress concen-trations are weak points in the structural system; and they have to withstand high forces and displacements during strong earthquakes. Thus, to design and properly detail joints is the most important factor in achieving the safe and economical precast structures.

Three types of joints are distinguished viz.

1) Embedded steel shapes anchored to the precast members by studs or rods and the connection completed with site welding or bolting. They are known as dry connections.

Drawback is the failure of the connections by shearing of studs, pull out of the anchor rods, splitting of the con-crete, brittle failure of the welds and bolt threads during earthquakes indicate that dry or mechanical connections

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are points of high stress concentrations and represent weak points in the system which can jeopardize its struc-tural integrity and safety.

Workmanship in field is an important factor of uncertain-ty and it appears that site welding is very susceptible to brittle failure.

2) Poured in-situ reinforced concrete joints with dowels and reinforcement either spliced or lapped or welded, are known as wet connections. This type of connections show excellent performance during earthquakes. They tend to behave monolithically, provide continuity, higher redun-dancy and add to the structural integrity of the system.

3) Post tensioning the precast elements together with ten-dons crossing the joints.

Connections in framed structures

Beam column connections are classified as, Rigid, Semi rigid and Hinge.

Rigid connections are incorporated into framed struc-tures as moment resistant joints to provide resistance against the gravity and earthquake loads. They are capable of trans-mitting the moment, shear and axial forces.

Semi rigid connections are similar to rigid ones, except that they have lower yield moments and do not develop full continuity.

Simple supported and hinged joints are designed to re-sist gravity loads only and have no moment resistance.

Joint types of cast in place and post tensioned, are cur-rently the most reliable means of connecting precast mem-bers and are used in ductile moment resistant frames.

Research work in New Zealand indicates these joints and systems to have good energy dissipation capacity.

Wall panel structures:

Shear connections between floor and wall panels in precast box type structures may be dry, wet or may be con-nected by post tensioning. Dry joints are points of high stress concentrations, which may lead to progressive joint deterio-ration. Thus wet poured in-situ strips with over-lapped hooks or dowels are preferred over mechanical devices and they are more reliable and effective. Tests carried out in japan showed that precast panels connected by wet joints behave monolithically and those with dry joints tend to behave inde-pendently.

S.no Aspect Indian (Is 15916:2010) Recommendations To Indian (Stan-dard Is 15916:2010) For Adoption.

1 Force Transfer Mech-anism -

Forces may be transferred between members by grouted joints, shear keys, mechanical connectors, reinforcing bar connections, welded or bolted connections reinforced topping, or a combination of these means.

2 Design Considerations 9.1 - The considerations for design of joints are: a) Feasibility, b) Practicability, c) Serviceability, d) Fire rating, e) Apperance

To control cracking due to restraint of volume change, and differential temperature gradients.

To provide resistance against sliding, overturn-ing and rocking.

3 Joint/Connection Requirements

9.2 (a) - It shall be capable of being designed to transfer the imposed load and mo-ments with a known margin of safety.

9.2 (c) - It shall accept the loads without marked displacement or rotation and avoid high local stresses.

9.2 (e) - It shall require little temporary support, permit adjustment and demand only a few distinct operation to make.

9.2 (g) - It shall be reliable in service with other parts of the building.

9.2 (h) - It shall enable the structure to absorb sufficient energy during earthquakes so as to avoid sudden failure of the structure.

4 Type Of Joints In Structure 9.2.1 - Continuous or hinged under lateral loading.

5 Water Tightness Specifications - Water tightness provisions to be detailed.

6 Fire Resistance 9.1 (b) - The fire rating for joints of precast components shall be higher or atleast equal to connecting members.

7 Detailing Specifica-tions Dry or wet joints as specified in cl. 9.3

8 Jointing Systems -

New Zealand code NZS 3101 part 1 have given the definitions of equivalent monolithic systems and jointed systems in a detailed manner. These are recommended for adoption in to IS codes.

9 Seismic Provisions (Ductility)

IS 13920:1993 suggest that precast and / or prestressed concrete members may be used only if they can be provided with the same level of ductility, as that of a mono-lithic reinforced concrete construction during or after an earthquake.

The definitions given for connections of limited ductility, ductile jointed connections and ductile hybrid connections as mentioned in NZS 3101 is recommended for adoption in to IS code.

10 Progressive Collapse

8.2 - Details about the requirement of safety against progressive collapse. Tie provisions horizontally and vertically are detailed with a tensile force of Ft = 60 kN or (20+4N)kN whichever is less, where N is the number of storeys including basement. Key element identification is also indicated.

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In Quest of Quality Concrete

Traditionally, construction involving concrete had been a labour-intensive activity in India. The demand for higher speed of construction, especially for residential and

commercial housing, and infrastructure projects involving construction of flyovers, highways, roads, airports, etc. neces-sitated adoption of mechanized and semi-mechanized tech-niques of construction. The need for large volumes of concrete as well as faster speed of concrete construction was felt. This was conducive for the development of ready-mixed concrete (RMC) on commercial basis.

Use of batching and mixing plants for producing large volumes of concrete was in vogue in India for a long time. However, such use was minimal and restricted to construc-tion of big jobs like hydro-electric projects, large industrial complexes, major bridges, etc. It was only since early 1990s that witnessed the beginning of commercial RMC industry in India.

The growth of RMC commenced with metropolitan cities, and then spread to other major cities. No authentic data is available on the RMC industry in India. However, it is believed that currently the industry has spread its wings to more than 100 cities of India. Major corporate-sector companies such as ACC Ltd. Ultratech Cement Ltd, Lafarge Aggregates & Concrete (P) Ltd., RMC Readymix (India) - Prism Cement Ltd., Godrej, etc have set up a large number of RMC plants in different cities. Again, no authentic data is available on the number of commercial plants in India; however, the number is believed to be exceeding 1000. In addition equal number of plants (or even more) is being operated by construction com-panies in India for captive use.

Quality of Concrete

Quality of concrete being produced and used in construc-tions - especially those involving use of primitive labour-intensive site-mixed concrete - has remained one of the major concerns of owners and specifiers. Unfortunately, till very recently, no established framework was available to ensure quality.

The Ready Mixed Concrete Manufacturers’ Association (RMCMA) was the first to initiate efforts to evolve a frame-work for quality for ready mixed concrete. It was based on two strong pillars – best practices followed in advanced countries and adherence to provisions in the Indian standards – mainly IS 456 and IS 4926. Two Quality Manuals prepared by Experts Committee contain the details of the RMCMA Scheme1,2. This

plant audit-based scheme was launched in December 2008 and around 250 RMC facilities at 50-plus locations in India (mostly belonging to RMCMA member companies) were au-dited and certified by the RMCMA.

After operating this quality scheme successfully for near-ly four years, RMCMA decided to raise the quality scheme to a higher pedestal. For this purpose, RMCMA signed a Mem-orandum of Understanding (MoU) with the Quality Council of India (QCI) – a non-profit, national apex organization wedded to quality facilitation, accreditation and surveillance.

QCI Scheme

QCI took the initiative of setting up three committees, namely, the Steering Committee, Technical Committee and Certification Committee. Experts from key organizations (see box) from the government and private sectors and pro-fessional bodies were invited to be the members of these committees. The involvement of these organizations in the evolution of the scheme ensured that the ownership of the scheme is broad-based and views and concerns of major owners and specifiers in the country using large volumes of concrete are taken into account.

The evolution of QCI scheme took more than one-and-a-half year. Following painstakingly prepared Scheme Manuals were finalized by the expert committees after long delibera-tions.

Vijay KulkarniTechnical Adviser, Quality Council of India and Former President - ICI

RMC PLANT: CERTIFICATION

Fig 1 Three expert committees set up by QCI

- Criteria for Production Control of Ready Mixed Concrete3 - Certification Process for Ready Mixed Concrete Produc-

tion Control Scheme4- Provisional Approval for Certifying Bodies for RMCPCS5.

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Multi Stakeholder Committees

- Central Government Ministries, e.g. Ministry of Housing & Urban Poverty Allevation, Ministry of Road Transport and Highways, MES, etc.

- Key Specifier: Central Public Works Department (CPWD)- Central PSUs e.g. National Highway Authority of India,

Airport Authority of India, RITES- User bodies, e.g. Builders Association of India, Construction

Federation of India.- Professional bodies, e.g. Indian Concrete Institute (ICI),

Association of Consulting Civil Engineers (ACCE), CREDAI.- Manufacturers, e.g. Ready Mixed Concrete Manufacturers’

Association (RMCMA), Cement Manufacturers’ Association (CMA)

- Certifying bodies, e.g. Bureau Veritas Certification (I) Pvt Ltd., ICMQ India Pvt Ltd.While formulating the scheme it was ensured that the

QCI Scheme conforms to the requirements of the Bureau of Indian Standards (BIS), Indian Roads Congress (IRC), Indian Railway Standards (IRS), etc. The Scheme is also made ap-plicable for:

- RMC plants supplying concrete commercially- Plants supplying concrete for specific project (captive

plants)- Plants supplying concrete partly on commercial basis

and partly for captive consumption. Scheme excludes operations of placing, compaction, fin-

ishing and curing of concrete.The Scheme documents (Fig 2) are publically available and

can be down-loaded from http://qcin.org/CAS/RMCPC.

exercised on the quality of different concrete ingredients, mix design and the final product.

The production control criteria which can be considered to be heart of the scheme include the following six main fea-tures:

1. Resource management: It covers three main areas, name-ly, plant, equipment and other utilities, laboratory and key personnel. Main areas under resource management are diagrammatically presented in Fig 4. Provision of basic laboratory testing facility is made mandatory under the QCI Scheme. The minimum testing equipment for the lab-oratory and the calibration frequency of the equipment are also specified. Compressive check list items have been developed so that an auditor is able to have an in-depth understanding of all key aspects of resource management having bearing on quality.

2. Control on Quality of Incoming Materials: The ready-mixed concrete producer needs to verify quality of all ingre-dients on a regular basis. Various standards of the BIS have specified the tests to be performed on different ingre-dients and their frequencies of testing. The QCI scheme has made it mandatory to perform these tests at BIS specified frequencies. It is also specified that the physical and chemical properties of the basic ingredients should be tested in NABL-accredited laboratory, at least once in six months or when there is a change in the source of mate-rials. Such rigorous testing regime would certainly ensure that ingredients having good quality are used in produc-tion of ready-mixed concrete.

Fig 3 QCI Scheme: Two options

Criteria for Production Control of RMC

Fig 2 QCI Scheme Manuals prepared by multi-stakeholder Committees

Certification Process forRMCPCS

Provisional Approval forCBs for RMCPCS

Two Options

The QCI Scheme offers two options of certifications, namely

- RMC Production Control Capability Certification- RMC 9000+ Certification

The Scheme logos are shown in Fig 3.RMC Capability Certification is the crux of the QCI

Scheme. Comprehensive criterion has been developed by the Technical Committee which is documented under the Scheme Manual “Criteria for Production Control of Ready Mixed Concrete”, published by BMTPC, Ministry of Housing & Urban Poverty Alleviation, Govt. of India3. Besides the audit of the plant and machinery and the control mechanism adopted by the producer, the criteria also embody laboratory testing facilities, technical skills of the human resources, the controls

3. Concrete Design: The QCI scheme requires that the ready-mixed concrete producer should have in-house capabili-ty to carry out mix proportioning. Plant personnel should also have the ability to carry out adjustments in the mix to cater to the variability in the incoming materials – for

RMC PLANT: CERTIFICATION

Fig 4 Resource management under production control criteria

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example, the variations in the moisture contents in ag-gregates, grading, etc. The competence of the key per-sonnel who carry out mix design will be judged by the auditors by going through the old records, interviewing some key personnel and witnessing few tests in the lab-oratory.

4. Production and Delivery: The auditor has been given the freedom to choose any five orders received by the producer during the past six months and verify from the autographic records as to whether the supplies have been made ex-actly as per the orders of the customers. Incidentally, the tests to be conducted and their frequencies in controlling the quality of the final product have also been specified in the QCI Scheme.

5. Control on Process Control Equipment and Maintenance: Upkeep of plant and equipment, their calibration, etc. play an important role in determining the quality of the final concrete. The QCI scheme specifies the frequency of in-spection, calibration tolerances, etc.

6. Complaints and Feedback: The QCI Scheme has made it mandatory to have a Nodal Officer, who will be responsi-ble for complaints and feedback. The scheme also high-lights the importance of having established procedures to receive, resolve, review and find out the root causes of the complaints.

Certification Process

Detailed procedures for carrying out certification under the QCI Scheme have been evolved and are explained in the Certification Manual4. The broad aspects covered under the procedures are as below:

1. Application for certification: It includes application form, registration of applicant and the information to be furnished by the applicant to the certifying body.

2. Audit program: The audit program is divided into Stage 1, Stage 2 and Surveillance audits. While each plant needs to be audited under RMCPCS, the ISO 9001 audits can be carried out on sampling basis as allowed under ISO 9001 certification.

3. Audit man-days: Audit man-days under certification and surveillance audits for both schemes have been fixed by the Certification Committee.

4. Audit planning: This includes the information to be provided to the certifying body, constitution of audit team and audit plan.

5. Certification audit: It provides guidance on how RMC 9001+ QMS based certification and RMC capability certification audits should be performed. Safety measures to be ad-opted during the audit are also highlighted.

6. Non-conformities: Three types of Non Conformity (NC) have been specified, namely, Critical, Major and Minor. The detailed descriptions of each of the NCs and the time for closure have also been specified (see Table 1). The CBs need to send the audit report within 7 days from the date of the completion of the audit.

7. Certification decision: Certificate will be issued by the CB, only when all raised NCs are closed (critical and major after on-site verification and minor after off-site verification).

8. Surveillance: Surveillance audits shall be carried out by the CB every six months, with at least one surprise audit in a year. The surprise audit will be conducted with a short notice of 3 days.

9. Complaints: This section covers the complaint handling process. The need to have a documented process to re-ceive, evaluate and make decisions on complaints is highlighted. The CB should audit the complaints received by the plant from its customers. The manner in which a complaint received about a certified plant should be han-dled is described.

Table 1: Non Conformities – Description, classification and time frame for closure

Non con-formity Description Classification Time frame for closure

Critical

Non compliance with a requirement which indicates serious failure of the plant’s ca-pability to produce and deliver RMC to meet the customer requirements

Check List items:3.2.1.1 Storage –Cement only3.2.1.2 Batching and Mixing3.3 Laboratory5. Concrete Mix design6. Production and delivery6.1 Identification and traceability7. Control of process control equipment and measurements

Within 15 days. Corrective ac-tions shall be submitted to CB within 10 days. Onsite verifica-tion to be undertaken within 5 days and decision taken either to close the NCs or suspend certification

Major

Non conformity regarding a Management system requirement which does not allow the production and delivery process to meet the customer requirements (applicable to ISO 9001 requirements only as defined by CB) or as given in the Criteria for the classi-fication in column 3

3.2.1.1 Storage –other than cement3.2.1.3 Delivery fleet3.4 Key personnel4. control of incoming materials8. Complaints

Within 1 month. Evidences of closure shall be provided to the CB; verification to be done on site

Minor

Non compliance with a requirement which does not compromise either the overall management system effectiveness or the production and delivery process

6.2 Control of non-conforming products9. Feedback.

Within 3 months. Evidences of closure shall be provided to the CB; verification to be done in the following surveillance audit

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10. Certificate: The information to be included in the certificate as well as its validity are described.

11. Suspension and withdrawal of certificate: It provides de-tailed guidance when the certificate will be suspended and withdrawn and the suspension will be revoked.

12. Change of location/ownership/name: The certified plant needs to inform the CB changes in location, ownership and name of company. With the change in location, audit of the new facility becomes essential. In case there is a change in the name of the company or its ownership, ap-propriate documents need to be submitted to the CB.

13. Fees: the fee structure of the CB shall be publically ac-cessible and also provided on request.

Approval System for Certification Bodies

The Certification Bodies (CBs) which would be auditing and certifying the ready-mixed concrete plants under the RMCPCS need to primarily comply with the requirements specified in ISO 17065 and additional requirements specified by the Quality Council of India. With a view to commence the operation of the scheme immediately, a Provisional System for Approval of the CBs was evolved, documented and approved by the Certification Committee5. Stringent requirements have been specified the committee for the CBs operating the scheme. The Minimum Competence Requirements of Auditors audit-ing the RMCPCS have been specified (see box). Further, the CBs will be subjected to a through yearly audit. They need to obtain accreditation from National Accreditation Board for Certification Bodies (NABCB) under the QCI.

Conclusion

The QCI Quality Scheme provides a comprehensive framework of controlling quality of concrete from ready-mixed concrete plants. The Key Benefits of the Scheme to owners/specifiers, RMC producers, small customers and concrete industry are highlighted below.

Key Benefits of QCI Scheme

- For Owners and Specifiers (architects, consultants)- Third-party quality assurance from an independenta-

gency, based on well-defined quality norms evolved by experts

- Reliable Tool for short-listing of concrete producers- For RMC/Concrete Producers- Competitive advantage over non-certified producers- Top management gets audited data on their plants- Small Customer (e.g. individual house builder)- Assurance on QA&QC of concrete, without employing

experts- Concrete Industry- Raise the industry standard and bring it on par with those

from advanced countries.

Epilogue

The QCI Scheme is voluntary. However, looking at the ad-vantages of the QCI Scheme, owners, specifiers, designers, etc. can make the scheme mandatory for jobs/projects undertaken by them. The scheme can also be used for short-listing of concrete supplier. Further, a six monthly third-party audit of the RMC facility provides crucial information to client/owner on actual performance.

Some government/semi-government organizations like the PWD-Pondicherry, BruhanMumbai Mahanagarpalika, Mumbai, CIDCO, Navi Mumbai, have already made the appli-cation of the Scheme mandatory for concretes procured for their projects (see enclosures).

References

1. Quality Manual Part – I Check List for Certification of Ready Mixed Concrete Production Facilities, Ready Mixed Con-crete Manufacturers’ Association, India, 2008.

2. Quality Manual Part – II Guidelines on Quality Control and Quality Assurance of Ready Mixed Concrete, Ready Mixed Concrete Manufacturers’ Association, India, 2008.

3. Criteria for Production Control of Ready Mixed Concrete under Ready Mixed Concrete Plant certification Scheme (QCI), Building Materials & Technology Promotion Coun-cil, Ministry of Housing & Urban Poverty Alleviation, Gov-ernment of India, New Delhi, 2013.

4. Ready Mixed Concrete Plant Certification Scheme (RMCPCS) – Certification Process, Quality Council of India, New Delhi, 2013.

5. Ready Mixed Concrete Plant Certification Scheme (RMCPCS) – Provisional Approval System for Certifica-tion Bodies, Quality Council of India, New Delhi, 2013. w

RMC PLANT: CERTIFICATION

Source: Websites of certifying bodiesLeading RMC producers in India - Current status of QCI Certifcation (July 2015)

Company No of Certified Plants

Plants under certification

ACC Ltd 10 3

Godrej & Boyce 7 0

IJM Concrete 6 0

Lafarge Aggregat & Concrete (I) Pvt Ltd. 18 11

RDC Concrete (I) Pvt Ltd 11 0

RMC Readymix (I) - a Div of Prism Cement Ltd.

18 14

UltraTech Cement Ltd. 39 0

Minimum Competence Requirement of Auditors

- Minimum Bachelor’s degree in engineering in related field(s) with at least 5 years of relevant experience in RMC/Batching plant; or Diploma in engineering in relat-ed field(s) with 7 years of relevant working experience in RMC/batching Plants

- Experience in core technical processes like QA/QC or production and process control

- Training and experience in auditing.

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Potential Use of Recycled Coarse Aggregates in Concrete

Abstract: Concrete continues to be the most consumed con-struction material in the world, only next to water. This fact is due to its appealing properties of high compressive strength and the property of mould-ability to any conceivable shape. Due to rapid increase in construction activities, it is import-ant to assess the amount of construction and demolition waste being generated and analyse the practices needed to handle this waste from the point of waste management and disposal and also with regard to waste utilization in concrete from the sustainability aspects. Construction and Demolition (C&D) waste constitutes a major portion of total solid waste production in the world, and most of it is used in landfills. Research by concrete engineers has clearly suggested the possibility of appropriately treating and reusing such waste as aggregate once again in concrete, especially in applica-tions such as bed concrete and in road beds for pavement i.e. where works are of less importance as regards to the strength. The use of such waste as recycled aggregate in concrete can be useful for both environmental and economic aspects in the construction industry. This study reports some interesting results of the utilization of recycled coarse aggregates in concrete from construction and demolished waste.

Due to high demand for construction activities in re-cent years in India and all over the world, the natural ag-gregates resources are remarkably waning day by day. On the other hand, millions of tonnes of C&D residues are gener-ated. Natural resources are dwindling day by day due to their extensive use to cope with the increasing demand of Civil Engineering Projects. Therefore, the use of C&D waste as an alternative aggregates for new concrete production gains importance to preserve natural resources and reduc-ing the need for disposal, (S Manzi et al. 2013). The amount of construction and demolition waste has increased enor-mously over the last decade in the entire world, (Sami W. Tabsh et al 2009). Disposal of construction and demolition waste has also emerged as a problem in India. Therefore, recycling of waste concrete is beneficial and necessary for the environmental preservation and effective utilization of natural resources, (Ashraf M. Wagih et al. 2013). The use of recycled coarse aggregate obtained from construction and demolition waste in new concrete is a solution for effective waste utilization, (M. Chakradhara Rao et al.2011).

The management of construction and demolition waste is a major concern due to increased quantity of demolition rubble, shortage of dumping sites, increase in cost of dis-posal and transportation and above all the concern about environment degradation. Although a substantial portion of

construction materials could be substituted by re-processed construction waste material, these options are not exercised in developing countries due to lack of knowledge and insuffi-cient regulatory frameworks resulting in waste getting piled up causing disposal problems, (R.V.Silva et al. 2014). The in-creasing problems associated with construction and demo-lition waste, have led to a rethinking in developed countries and many of these countries have started viewing this waste as a resource and presently have fulfilled a part of their de-mand for raw material, (Shi-Cong Kou et al. 2012).

Many developed countries have been recycling C&D waste and using it for construction works. In Scotland about 63% of the C&D waste was recycled in 2000. The Government there is working out specifications and code of practice for recycling of C&D waste. U.K uses 49-52% of the C&D wastes and Aus-tralia reuses 54% of the wastes generated. Belgium has a higher recycling rate (87%) and uses majority of C&D for re-cycling purposes. Japan is one of the pioneer countries that recycle C&D waste. 85 million tonnes of C&D waste was generated in 2000, of which 95% of concrete was crushed and reused, (Akash Rao et al. 2007).

Using recycled concrete aggregates, will require checking the quality of the aggregates, since they are col-lected from different sources, grades of concrete and age, (A.K.Padmini et al. 2009). Concrete workability is more influ-enced by the shape, texture and grain size distribution of the recycled aggregates than by their total amount, (S. Manzi et al. 2013). The compressive strength primarily depends upon adhered mortar, water absorption, Los Angeles abrasion, size of aggregates, strength of parent concrete, age of curing and ratio of replacement, interfacial transition zone, moisture state, impurities present and controlled environmental condition (Isabel Martínez-Lage et al. 2012). Absorption of RCA is one of the major contributing factors in the strength of concrete, (K C Panda and P K Bal 2013).

This study reports some important changes in properties such as compression strength and absorption of recycled aggregate concrete.

Materials

Ordinary Portland Cement (OPC) 43 grade was used and its properties are tabulated in Table 1. Coarse aggregate was crushed stone with a maximum size of 20 mm. Locally avail-able natural river sand conforming to zone III (IS 383-1970 grading requirements) was used as fine aggregate. Physical properties of fine and coarse aggregates are presented in Tables 2 and 3 respectively. Potable quality water is used.

Subhash C. Yaragal , Vivek V B , M Padmini , M Jacob, J Niveditha1, Anil Kumar Pillai2

1National Institute of Technology Karnataka, Surathkal 2The Ramco Cements Limited

CONCRETE: RECYCLED AGGREGATES

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Recycled aggregates were obtained from demolished con-crete made in the laboratory with maximum size of 20 mm.

Table 4 shows the properties of recycled coarse ag-gregates and Table 5 gives mix proportions for OPC based concrete. The sieve analysis results of natural and recycled aggregates are shown in Table 6.

Sources and processing of RCA

In order to obtain correct assessment of strength of RCA based concrete, it was thought necessary to produce con-struction and demolished waste from same quarry virgin coarse aggregates. To achieve C & D waste, about 30 Nos. of 150 mm concrete cubes were cast and cured for a period of 28 days. Later all these were compressed to failure, to produce C & D waste.

A common procedure adopted to recover the coarse ag-gregates from C & D wastes is as follows. The C & D waste, was fragmented manually further, and then 10 Kg of C & D waste was placed in Los Angeles aggregates testing machine with constant charge and the apparatus was run for 5 min-utes.

Later this processed material is removed, and sieve analysis was carried out. After sieve analysis, the obtained

No. Property Result ob-tained

Requirements as per IS code

1 Specific gravity 3.12 -

2 Normal con-sistency 29% -

3 Setting times, minutes

Initial 65Final 270

Not less than 30Not more than

600

4 Fineness,m2/Kg 330 Not less than

300

5 Soundness, mm 2.50 Not more than

10 mm

6 Comp. strength,Mpa

3d 7d 28d 3d 7d 28d

34 51 61 22 33 43

Table 1 Physical properties of Ordinary Portland Cement

(NCA-Natural Coarse Aggregates, RCA-Recycled Coarse Aggregates)

Table 6 Sieve analysis results of natural and recycled coarse aggregates

Table 2 Properties of fine aggregates

Table 3 Properties of coarse aggregates

Table 4 Properties of recycled coarse aggregates

Fig. 1 Compressive strength variation of OPC based concrete with RCA (Mean data)

Fig. 2 Compressive strength variation of OPC based concrete with RCA (Full data)Table 5 Composition of various mixes for OPC blended concrete

(RCA-Recycled Coarse Aggregate, C-Cement, FA- Fine Aggregates, CA-Coarse Aggregates, W- Water)

Property Result

Specific gravity 2.62

Bulk density Loose: 1463 Kg/m3

Compact: 1661 Kg/m3

Moisture content Nil

Property Result

Specific gravity 2.73

Bulk density Loose: 1360 kg/m3

Compact: 1527 kg/m3

Moisture content Nil

Sl. No. Property Results

1 Specific gravity 2.59

2 Water absorption 2.69%

3 Fineness modulus 6.96

MixRCA C FA CA RCA W

(%) (kg) (kg) (kg) (kg) (kg)

Mix 1 0 400 600 1200 - 200

Mix 2 20 400 600 960 240 200

Mix 3 40 400 600 720 480 200

Mix 4 60 400 600 480 720 200

Mix 5 80 400 600 240 960 200

Mix 6 100 400 600 0 1200 200

Sieve size (mm)% Finer

NCA RCA

20 100 100

16 68.5 71.5

12.5 32.1 27.7

10 0.7 0.5

CONCRETE: RECYCLED AGGREGATES

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RCA, was agitated and washed in a water tank to remove surface crushed rock fines (dust) and sun dried before their being used as RCA to cast specimen.

Experimental Methodology

The obtained aggregates are mixed in proportions of 0%

(no RCA), 20%, 40%, 60%, 80% and 100% (all RCA) by weight of the total natural coarse aggregates in concrete. So for each mix 3 Nos. of 150 mm cubes concrete cubes as stipulated by the code were cast. 18 Nos. of 150 mm cubes were cast and 28 days water cured before testing them for compressive strengths. Experiments were aimed for achieving workable slump between 50-75mm without using super plasticizers. Standard slump cone apparatus is used for measuring the value of slump. During the slump tests it was found that the workability of fresh concrete made with 100% replacement of RCA had slump value close to zero mm. With increase in percentage of RCA in concrete the workability was getting lower and lower. This was mainly due to the high absorp-tion rate (2.69%) of the RCA as compared to the fresh coarse aggregate (0.2%). Adding water to compensate for this ab-sorption was not a good option as exact amount could not be ascertained. So it was decided to soak the RCA for 24 hours before use, so that it does not absorb water during the process of mixing (M. Etxeberria et al. 2007), this method of soaking helped to attain moderate workability of concrete without use of plasticizers. The test matrix for compression test is shown in Table 7.

The concrete samples with RCA are tested for 28 day strengths and compared with the results of the strengths of concrete made with virgin natural aggregates.

Results and Discussion

Compressive Strength

Table 8 presents the results of the compressive strength tests for OPC based concrete specimen. It can be noticed that the compressive strength of the cubes goes on decreasing as the percentage of the RCA replacement gets increased from 42.1 MPa for the control mix to 30.8 MPa in the fully RCA replaced cubes. The drop in strength with increase in RCA proportion is attributed to the bond strength becoming weaker and weaker with RCA increase.

From Table 8, it is observed that there is a decrease in strength from 7% to 27%, when 20% of virgin aggregates is replaced by RCA, to the case when 100% of virgin aggregates is replaced by RCA. These findings are in agreement with other investigators. S.C.Kou et al. (2012) reports a fall in the compressive strength. Sami W. Tabsh and Akmal S. Abdel-fatah (2009) have reported that the decrease in strength is by about 10-25%. Sumaiya Binte Huda and M. Shahria Alam (2014) have got a decrease in 15-20% when aggregates were replaced. Figure 1 shows the normalized compressive strength variation, with increase in RCA. These findings are

RCA (%) No. of cubes

0 3

20 3

40 3

60 3

80 3

100 3

Total 18

Table 7 Test matrix for compression on 150 mm cubes

Table 8 Compressive strength of cubes for OPC based concrete specimen

Table 9 Water absorption results for OPC based concrete

Fig. 3 Variation of percentage of absorption for OPC, with RCA

RCA (%)Comp.

Strength (N/mm2)

Average Comp.

Strength (N/mm2)

Relative Comp.

Strength

Average Relative Comp.

Strength

Control 40.44

42.1

0.96

1.000 43.11 1.02

42.67 1.01

20

39.11

39.3

0.93

0.9340.89 0.97

37.78 0.90

40

37.78

37.5

0.90

0.8937.33 0.89

37.33 0.89

60

34.22

34.4

0.81

0.8134.22 0.81

34.67 0.82

80

33.77

33.5

0.80

0.7934.67 0.82

32.00 0.76

100

30.22

30.8

0.72

0.7331.11 0.74

31.11 0.74

RCA (%) Dry weight (kg)

Wet weight (kg)

Absorption (%)

0 8.232 8.579 4.22

20 8.080 8.470 4.83

40 7.844 8.256 5.23

60 8.093 8.485 4.84

80 7.956 8.371 5.22

100 7.963 8.36 4.99

CONCRETE: RECYCLED AGGREGATES

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similar to the results of Wai Hoe Kwan et. al (2012). Shi-Cong Kou and Chi-Sun Poon (2013) have also reported a decline in their compressive strength. K.K.Sagoe-Crentsil et al (2001) have similar results with recycled aggregates replaced con-crete. According to the studies by Isabel Martínez-Lage et al. (2012) the estimated loss for concrete with 100% recycled aggregate was 23%, with values ranging from 20% to 31%.

There is a reduction from normalized strength factor of 1.00 to 0.73, when the natural aggregate was completely replaced with recycled aggregate. Hisham Qasrawi (2014) has also reported a reduction in concrete strength when re-placed with RCA. K C Panda and P K Bal (2013) have reported that compressive strength, flexural strength and split tensile strength of concrete decreases with increase in the amount of RCA.

Figure 2 shows the best fit line, showing the drop in strength of concrete with increase in percentage of RCA. The proposed equation can be used to predict the normal-ized strength of concrete as a function of RCA, with maxi-mum error in prediction of less than 2.5%.

Normalized Strength = 0.9848-[0.0026Xrca(%)] ..(1)

Water Absorption Test

Water absorption was used to determine the amount of water absorbed under specified conditions that indicates the degree of porosity of a material. The results of the water ab-sorption tests are as shown in Table 9. The results indicate that the water absorption was higher in all the cases when there is a replacement by recycled aggregate. The percent-age of absorption varied from 4.22% to 5.23%. It is clear that the concrete with RCA has more absorption rate than that of the control mix. This is mainly due to the high absorption of the recycled aggregate compared to the natural aggregate (Isabel Martínez-Lage et al 2012). The residual mortar at-tached to recycled concrete particles serves as a potential conduit for moisture transport. Figure 3 shows water ab-sorption in a graphical form. Hence we can say that the RAC has more porosity when compared to the normal concrete. Though this may not have a direct relation with the durability of the concrete, it is affecting the strength of the concrete.

K.K.Sagoe-Crentsil et al (2001) have got absorption rates ranging between 5-7%. The absorption rate of this investiga-tion ranges between 4-6%.

Conclusions

(1) RCA exhibits similar behaviour like fresh aggregate in concrete; therefore, RCA could be incorporated into many concrete structures. However, RCA that has an unknown origin should be tested to ensure that the RCA was not from a structure that was suffering from alka-li-silica reaction, alkali-aggregate reaction, sulphate at-tack, or some other harmful reaction. Such RCA could affect adversely the strength and durability of the con-crete and may be harmful.

(2) A maximum reduction of about 27% was noticed in com-pressive strength when the entire coarse natural aggre-gate was replaced with RCA. Moreover, environmental benefits may be able to compensate for the negative effect of loss in strength to some extent due to the use

of recycled coarse aggregate in concrete leading us to sustainable development.

(3) Absorption for RCA concrete was more than that for con-trol mix. This may affect the durability of the concrete.

(4) As the degree of processing gets higher the RA tends to be more similar to NA. Hence RA after processing shows better results than unprocessed RA.

References

[1] A.K.Padmini, K.Ramamurthy, M.S.Mathews (2009), Influence of parent concrete on the properties of recycled aggregate concrete. Construction and Building Materials, 23, 829-836.

[2] Akash Rao, Kumar N. Jha, Sudhir Misra, (2007), Use of aggregate from recycled construction and demolition waste in concrete, Re-sources Conservation and Recycling, 50, 71-81.

[3] Ashraf M. Wagih , Hossam Z. El-Karmoty , Magda Ebid , Samir H. Okba (2013), Recycled construction and demolition concrete waste as aggregate for structural concrete, HBRC Journal , 9, 193–200.

[4] Hisham Qasrawi (2014), The use of steel slag aggregate to enhance the mechanical properties of recycled aggregate concrete and re-tain the environment, Construction and Building Materials, 54, 298–304.

[5] Isabel Martínez-Lage, Fernando Martínez-Abella, Cristina Vázquez-Her-rero, Juan Luis Pérez-Ordóñez (2012), Properties of plain concrete made with mixed recycled coarse aggregate , Construction and Building Materials ,37 ,171–176.

[6] K C Panda, P K Bal (2013), Properties of self-compacting concrete using recycled coarse aggregate, Procedia Engineering, 51, 159 – 164.

[7] K.K.Sagoe-Crentsil, T.Brown, A.H.Taylor (2001), Performance of concrete made with commercially produced coarse recycled con-crete aggregate, Cement and Concrete Research, 31 , 707-712.

[8] M. Chakradhara Rao , S.K. Bhattacharyya , S.V. Barai (2011), Be-haviour of recycled aggregate concrete under drop weight impact load, Construction and Building Materials, 25 ,69–80.

[9] M. Etxeberria , E. Vázquez, A. Marí, M. Barra (2007), Influence of amount of recycled coarse aggregates and production process on properties of recycled aggregate concrete, Cement and Concrete Research, 37, 735–742.

[10] R.V. Silva, J. de Brito, R.K. Dhir (2014), Properties and composition of recycled aggregates from construction and demolition waste suit-able for concrete production, Construction and building materials, 65, 201-217

[11] S. Manzi , C. Mazzotti, M.C. Bignozzi (2013), Short and long-term behavior of structural concrete with recycled concrete aggregate, Cement & Concrete Composites , 37 , 312–318

[12] S.C. Kou, C.S. Poon (2012), Enhancing the durability properties of concrete prepared with coarse recycled aggregate, Construction and Building Materials, 35, 69–76.

[13] Sami W. Tabsh ,Akmal S. Abdelfatah (2009), Influence of recycled aggregate concreteon strength properties of concrete, Construction and Building Materials ,23, 1163–1167.

[14] Shi-Cong Kou, Chi-Sun Poon (2013), Long-term mechanical and du-rability properties of recycled aggregate concrete prepared with the incorporation of fly ash, Cement & Concrete Composites, 37, 12–19.

[15] Shi-Cong Kou, Chi-Sun Poon, Hui-Wen Wan (2012), Properties of concrete prepared with low-grade recycled aggregates, Construc-tion and Building Materials, 36, 881–889.

[16] Sumaiya Binte Huda, M. Shahria Alam (2014), Mechanical behavior of three generations of 100% repeated recycled coarse aggregate, Construction and Building Materials, 65, 574-582.

[17] Wai Hoe Kwan , Mahyuddin Ramli, Kenn Jhun Kam, Mohd Zailan Sulieman (2012), Influence of the amount of recycled coarse aggre-gate in concrete design and durability properties, Construction and Building Materials, 26, 565-573. w

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Performance of Calcium Silicate-Based Carbonated Concretes vs. Hydrated Concretes under Freeze-Thaw Environments

Abstract: Solidia Technologies® has developed a calcium sili-cate-based cement (CSC), which emits less CO2 during its pro-duction as compared to Ordinary Portland cement (OPC). This CSC is hereafter referred to as Solidia Cement™. Additionally, Solidia Concrete™ made using Solidia Cement cures and hard-ens through a carbonation process and consumes CO2 during this process. The total CO2 footprint associated with cement manufacturing and use can be reduced by up to 70% when Solidia Cement replaces OPC. Although Solidia Concrete can achieve compressive strengths over 10,000 psi, the effect of freezing and thawing exposure and surface scaling in presence of salts need to evaluated. This paper presents results for two types of Solidia Concrete and a reference concrete tested as per ASTM C666 procedure A. The scaling resistance is evaluated as per ASTM C672 for air entrained Solidia Concrete and reference concrete. RDME values for both Solidia Concrete and reference concrete after 300 FT cycles were about 88%. After extended FT exposure (~800 cycles) concrete specimens performed well as RDME values did not reduce further. The scaling resistance after 50 FT cycles was very good for Solidia Concrete and reference concrete.

The Cement Sustainability Initiative of the World Business Council for Sustainable Development set 2050 CO2 reduction targets for the global cement industry. To accomplish this goal, the use of alternative cementitious materials is becoming more prevalent. Solidia Technologies® has addressed this challenge through the development of a calcium silicate-based cement (CSC), which emits less CO2 during its production as compared to Ordinary Portland cement (OPC). This CSC is hereafter re-ferred to as Solidia Cement™. Additionally, Solidia Concrete™ made using Solidia Cement cures and hardens through a car-bonation process and consumes CO2 during this process. The total CO2 footprint associated with cement manufacturing and use can be reduced by up to 70% when Solidia Cement replaces OPC.

Before Solidia Concrete can be used in widespread appli-cations, its durability must be demonstrated. The durability of concrete is generally defined as the ability to withstand damaging effects of the environment without deterioration for a designed

duration. The durability of concrete involves resistance to freeze-thaw, corrosion, carbonation, alkali-silica reaction (ASR) and chemical attack from sulfates and chlorides, and many more.

Concrete has the potential to be damaged if it is subjected to freeze-thaw cycles as water expands during freezing. Frost damage-a progressive deterioration process that starts with the surface separation (or scaling) and ends up with extensive cracking of the interior of the element-is a major concern when concrete is used in cold regions. The deterioration proceeds as freezing and thawing cycles are repeated, and the material gradually loses its stiffness and strength. In addition, increas-ingly irreversible expansion is induced.

Air-entraining agents are recommended for most of the concretes, principally to improve resistance to freeze-thaw cy-cles when exposed to water and deicing chemicals in cold re-gions. This paper reports RDME and mass change for Solidia Concrete and reference concretes after 300, and 800 freeze-thaw cycles. Scaling resistance is reported after 50 and 100 cycles for Solidia Concrete.

Materials, Mixture Proportions and Experiments

Materials, Mixture Proportions and Mixing Procedure

Solidia Cement, sand, coarse aggregates and water were weighed as per proportions in Table 1. Coarse aggregates were loaded to the mixer, followed by Solidia Cement and then by sand. The aggregates, cement and sand were mixed for 1 min-ute to produce a dry mix. While the mixer was rotating, 50% of the water was added to the dry mix to produce a wet mix. All water-reducing admixture was then added to the wet mix, followed by the remaining amount of water. Finally, all air-en-training admixture (AEA) was added to the wet mix. This wet mix was mixed for an additional 3 minutes. The mixer was stopped for one minute to settle the wet mix. Wet mix was mixed for an additional 30 seconds and unloaded into a pan.

The air content and the unit weight of fresh concrete were measured as per ASTM C231. Rectangular concrete beams with the dimensions of 3 in x 4 in x16 in (75 mm x 100 mm x 405 mm) and 4 in x 8 in (100 mm diameter x 200 mm length) cylinders

Jitendra Jain, Ph.D.,1, Vahit Atakan, Ph.D.,2, Nicholas DeCristofaro, Ph.D.,3, HyunGu Jeong4, Jan Olek, Ph.D.,51Sr. Research Scientist, 2Director, Research and Development, 3Chief Technology Officer, Solidia Technologies®, 4Graduate Student, 5Professor, Purdue University, West Lafayette, Ind.

CEMENT: CSB

First of a Three-Part Series Exploring the Durability of Solidia Concrete™ in a Variety of Testing Environments

3

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were cast in metallic molds in three layers. For the scaling test, concrete slabs of 12 in x 6 in x 3 in (302 mm x 151 mm x 76 mm) were cast in mold in two layers. With the addition of each layer, the mold was vibrated on a table vibrator for 30 seconds. All Solidia Concrete specimens were demolded after 4-5 hours. The demolded concrete specimens were placed in a chamber for CO2-curing. The CO2-curing parameters to achieve the de-signed compressive strength were 60oC and 98% inlet CO2 con-centration for 65 hours.

Comparable reference-concrete specimens were demold-ed after 24 hours and submerged in lime-saturated water for 28 days to achieve designed compressive strength. Reference concrete contained 20% fly ash as cement replacement which is typical in pavement concretes in Indiana. The water to cement ratio for Solidia Concrete was selected such as to obtain similar porosity and compressive strength as that of reference concrete.

Solidia Concrete specimens were produced at Solidia Tech-nologies’ facility in Piscataway, N.J. The freeze thaw resistance test as per ASTM C666 (Procedure A – freezing and thawing in water) and scaling resistance test as per ASTM C672 were per-formed at Purdue University, West Layette, Ind. The results of these tests were already presented at ACI Fall Convention in 2014.

Procedure to Determine Freeze-Thaw Resistance

Prior to initiating the FT testing both, the CO2-cured Solid-ia Concrete specimens and water-cured reference concrete specimens were preconditioned by saturating them in tap water for 48 hours. Initial mass and fundamental transverse frequen-cies were measured for saturated specimens. Each specimen was then placed in a container with water surrounding it. The containers were placed in the freeze-thaw apparatus. Each freeze-thaw cycle consisted of lowering the specimen tem-perature from 40o to 0oF and then increasing the temperature back to 40oF over a time duration of about 5 hours. The mass and resonant frequencies were measured for each specimen after the completion of each 30 freeze-thaw cycles. Measure-

ments were done immediately after the completion of the thawing cycle.

Freeze-thaw durability was calculated using the following equations:

(1)

According to ASTM C666, the freeze-thaw test process is continued to 300 cycles or to the point when Durability Factor (DF) drops below 60%, whichever occurs first. As the number of FT cycles are 300, RDME is equal to DF. As Solidia Concrete is a novel concrete, no long-term durability information under FT exposure is available. Therefore, while ASTM C666 requires testing up to 300 cycles, this testing was continued beyond 700 cycles to evaluate the freeze-thaw potential of Solidia Concrete.

Procedure to Determine Scaling Resistance

CO2-cured Solidia Concrete and water-cured reference concrete specimens were preconditioned in air (23°C, 50% RH) for 14 days. A dam was installed using a waterproof material around the perimeter of the specimens. This dam was designed to expose the top surface area of the specimen to a salt solution consisting of 4% calcium chloride.

For the scaling resistance measurement, the specimen was at freezing temperature (-18°C) for 11 hours and at thawing temperature (23°C) for 11 hours. Water was added to the sur-face if the solution level dropped below 6 mm during the exper-iment. After every freeze-thaw cycle, the solution was changed. During measurements, the calcium chloride solution was re-moved. The surface was flushed with water, pictures were tak-en to record changes due to exposure to FT action in presence of salt solution, and the mass of each specimen was recorded.

Results and Discussions

Freeze-Thaw Test Results

Mass Changes: The changes in mass and resonant fre-quencies of all specimens were measured after every 30FT cy-cles. Figure1 shows the normalized mass (with respect to the initial mass) for Solidia concrete specimens (both air entrained and non-air entrained) and for the reference concrete (air en-trained). Values higher than 1.00 indicate mass gain whereas values lower that 1.00 indicate mass loss. For Solidia Concrete, the increase in mass is attributed to water absorption during the test as most of the mixing water is removed from Solidia Concrete during CO2 curing. Although specimens were soaked in water for 48 hours before the commencement of test, the smaller size pores present in Solidia concrete are not expected to saturate within this time period. It can also be observed from Figure 1 that the mass gain is greater for air-entrained speci-men due to the presence of large air voids. For the reference concrete, continuous mass loss is observed after exposure to FT cycles. After 500 cycles, air entrained Solidia Concrete has about 1% mass gain, while air entrained reference concrete lost about 6% of its mass. Non-air entrained Solidia Concrete lost less than 0.1% mass. This behavior can also be seen in Figure 2, which shows photographs of Solidia concrete and reference concrete specimens after exposure to 300 FT cycles. In Figure 2, aggregates are clearly visible on the surface of reference concrete specimens. This is the result of scaling of the OPC-

Ingredients Solidia Concrete Reference Concrete

Ordinary Portland Cement 325

Solidia Cement 400 -

Fly ash 0 81

Sand 689 765

Coarse Aggre-gates 1134 1032

Water 116 170

AEA, ml/kg of cement 3 3

Water reducer, ml/kg of cement 10 0

Water to cement-ing materials 0.30 0.42

Air Content, % 5.5 6.7

Table 1: The proportions of raw materials for concrete mixtures, kg per cubic meter

CEMENT: CSB

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based concrete surface. In contrast, the Solidia Concrete spec-imens do not show that much scaling and thus do not experi-ence significant mass loss.

Scaling resistance test results

Specimens from the Solidia Concrete and reference con-crete scaling tests are shown in Figure 4A and 4B respectively before and after different number of FT cycles. The tests were performed as per ASTM C672, which is described in section 2.3.

Figure 4A shows no surface scaling for Solidia Concrete after 50 FT cycles in the presence of calcium chloride solution, which indicates good scaling resistance. The test was contin-ued further to evaluate long-term performance for Solidia Con-crete, which shows no visible scaling after completion of 100 cycles.

Figure 4B shows reference concrete specimens after dif-ferent numbers of FT cycles. After exposure for 50 cycles, the reference concrete specimen does not show any visible scaling and, thus can also be considered having good scaling perfor-mance.

Conclusions

In this study, the freeze-thaw and scaling resistance was evaluated as per ASTM procedures for Solidia Concrete and reference concretes. The following can be concluded form the data collected from the study:

1) Air entrained Solidia Concrete performed extremely satis-factorily in freeze-thaw testing, retaining 88% of the original dynamic modulus even after 500 FT cycles and displaying essentially no mass loss. Even without air entraining, the performance of Solidia Concrete was judged to be reason-ably satisfactorily-essentially zero mass loss being record-ed even after 500 cycles, while the relative dynamic mod-ulus at 300 cycles (the standard duration of testing) was reduced to about 60% of the original value.

2) Air entrained Solidia Concrete showed no visible deteri-oration in the standard scaling test, even after 100 cycles, i.e. twice the number of cycles usually administered in this form of testing.

3) Despite the relatively satisfactory performance displayed by non-air entrained Solidia Concrete, normal air entraining is recommended where freezing and thawing are anticipated.

(B) Initial

(A) Initial

10 cycles

5 cycles

15 cycles

50 cycles

50 cycles

100 cycles

Figure 4: Solidia Concrete (A) and reference concrete (B) scaling spec-imens before and after completion of different number of FT exposure cycles

Figure 1: Mass change for reference concrete and Solidia Concrete over the duration freeze thaw test up to 800 FT cycles

(A) Solidia Concrete (B) Reference Concrete

Figure 2: Concrete specimens made with (A) Solidia Cement and (B) OPC cement after completion of the FT test (350 cycles)

Relative Dynamic Modulus of Elasticity: The relative dynamic modulus of elasticity was calculated for all concrete specimens exposed to freezing and thawing after every 30 cycles using Equation 1. Figure 3 shows RDME values for Solidia Concrete (air entrained and non-air entrained) and reference concrete (air entrained) after exposure to different number of FT cycles.

Figure 3: Relative Dynamic Modulus of Elasticity for Reference and Solidia Concretes over the duration freeze thaw test up to 800 FT cycles

The RDME values decrease due to the formation of mi-cro-cracks in concrete specimens when exposed to FT action. After first measurement, the RDME values were reduced for all specimens and remained at about 90% or more after 300 cycles for both air entrained Solidia Concrete and reference concrete. For non-air entrained Solidia Concrete, RDME values decreased to about 80% after 100 FT cycles and to about 58% after 300 FT cycles. These values of RDME indicate very good FT resistance for air entrained Solidia Concrete but marginal performance for non-air entrained concrete.

CEMENT: CSB

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78ROLLER COMPACTED CONCRETE

Construction of Roller Compacted Concrete Dam: A Case Study at Batu Hampar Dam

Abstract: Rapid and economical construction are among nu-merous advantages of the construction of roller compacted concrete (RCC) dam compared to conventional dam. However, the complex process of RCC dam construction is facing diffi-culties due to lack of understanding and involvement from the local construction industry player since this type of construction in Malaysia is still new. Therefore, this paper presents the pro-cess of RCC dam construction in Malaysia. Site observation and the review on literature of RCC dam construction was conduct-ed to get the real view on the construction process of such proj-ect. The expert panel interview was conducted to get the view on RCC dam construction. Panel interview result was analysed and supported with the literature to gather the process of RCC dam construction. From the result analysis, the construction processes which consist of determination of mix design, RCC production and RCC placement is presented.

The new technology is adopted for the construction of gravity dam and the technology is known as roller compacted concrete (RCC). Reference [1] stated that RCC has been rapidly developing over the past 40 years and now is commonly used for gravity dam application. Recently, Malaysia started adopting RCC technology to the gravity dam construction. With the fact that the construction of RCC dam is still new in Malaysia, the understanding on such construction is very limited among local construction industry player. The first RCC dam in Malaysia is Kinta dam which is situated in Ipoh and constructed by Japa-nese contractor (Hazama Corporation). It was completed in 2007. In 2008, the construction of Batu Hampar dam is started which is the second RCC dam project in Malaysia. Dekon Sdn. Bhd, the local contractor who had no previous experience of RCC dams was selected to construct the dam. The government intention to develop local knowledge or expertise of RCC in-stead of recourse to international contractor is the main rea-son why Dekon was selected [2].

The understanding and involvement from the local con-struction player is still at the early stage. Therefore, the construction personnel such as engineer, the supervisor, the technician, until the general workers has very limited knowledge on the RCC dam project that leads to difficulties. Hence, there is a need to capture the knowledge of RCC dam construction.

This study will serve as an avenue for further under-

standing the construction of RCC dam among the local con-struction industries player.

This paper presents the process of the construction of Roller Compacted Concrete Dam in Malaysia with Batu Hampar dam in Rembau, Negeri Sembilan as the case study since Malaysia has just started to adopt the RCC dam tech-nology in the construction of the Dam project. The scope of this study is focused on construction stage of RCC dam proj-ect. This study involves interview sessions with the profes-sional and semi-professional construction personnel who were involved in RCC dam project in Malaysia. Roller Com-pacted Concrete Dam

Roller Compacted Concrete Dam

Concrete in general are defined as a composite construc-tion material composed primarily of aggregates, cement and water. According to America Concrete Institute (ACI), Roller compacted concrete (RCC) is defines as concrete compact-ed by roller compaction [3]. RCC is considered for application where no slump concrete that can be transported, placed and compacted by using the normal construction equipment that being used in earthfill and rockfill works [3]. Parallel to this, [4] defines RCC as no slump consistency concrete that is placed in a thin horizontal lifts and compacted by vibratory rollers. The application of RCC is considered when it is eco-nomical competitive with other construction method and in this case is the application of RCC method for construction of a gravity type of dam [4].

RCC dam construction requires four basic component which includes ingredient for the concrete, production of the concrete, transportation and placement of the concrete to the dam [5].

RCC Mix Design

The typical RCC mix design contains approximately 5-6 percent water, 5-10 percent cement and flyash, 30-35 per-cent fine aggregates and 60-65 percent coarse aggregates. This design possesses the characteristic required by the gravity dam which is strength and permeability properties [4]. RCC mixture proportioning procedure is very similar to conventional concrete. According to [6] the general method-

Assrul Reedza Zulkifli1, Abdul Rahim Abdul Hamid2, Mohd Fadhil Arshad3, Juhaizad Ahmad4

1Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam Selangor, Malaysia2Faculty of Civil Engineering, Universiti Teknologi Malaysia Johor Bahru, Malaysia3Institute Infrastructure Engineering and Sustainable Management (IIESM), Universiti Teknologi MARA, Shah Alam Selangor, Malaysia4Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam Selangor, Malaysia

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ology of RCC mixes proportion by used soils approach is:

1) Selection of suitable aggregate.2) Select range of trial mixes which consist of various ce-

ment and fly ash content.3) Determine desirable moisture content.4) Prepare RCC cylinder and specimen for strength testing

and durability testing.5) Select mix proportion based on laboratory result

RCC Placement

According to [7] the machineries used to construct RCC dam are similar to the construction of earth embankment which is dozer, dump truck and roller compactor. Dump truck used to transport the RCC mixture to the dam site, and dozer used to spread the RCC material at certain thickness, then the roller compacter required to compact the RCC ma-terial [7].

According to [3] RCC lift minimum thickness is ranging from 150 mm to 1m but in normal practice in United State is rarely exceeded 0.6m and the thickness is depending on mixture proportions, plant and transport capability, place-ment rates, spreading and compacting procedure, and the size of placement area.

Methodology

The overall view of the RCC dam construction was cap-tured from the literature review and interview questions were drafted based on site observation. Interview sessions were conducted and the statement given by the respondent was recorded. The interview was recorded using a digital recorder to record opinions provided by the interviewee and were converted into a written form. Furthermore, content

analysis was done on the answer and statement given by ev-ery respondent during the interview.

Result and Discussion

From the analysis, the processes of RCC construction works as shown in Figure 1 are listed below:

1) Determination of RCC mix (RCC design mix)2) Aggregates production3) Foundation preparation and treatment4) Diversion culvert and river diversion works5) RCC mix production6) RCC placement works7) Instrumentation works

A. Determination of RCC Mix

Three combined mix aggregates grading namely T1(63-25)mm size, T2(25-5)mm size and T3(5-0.75)mm size which is coarse, medium and fine size of aggregates are adopted. This mix aggregates grading meets the specified grading en-velope as in specification. Cement with low heat of hydration is the ideal cement to prevent temperature rise in concrete. To lower the heat of hydration of RCC, less amount of ce-ment is used and type F Flyash is used to replace the quan-tity of cement. It was finalized and approved by RCC dam specialist as follows: 1) T1-28%, T2-34%, and T3- 38%2) Cement- 65kg/m3 and Flyash-105kg/m3

3) Moisture content between 4.5% and 5.4% 4) Vebe time with a 12.5kg surcharge was 15 to 30 second5) Retarder is used to increase the initial setting time, there

by maintaining fresh lift joint6) Bedding mortar used to treat the cold joint for RCC lift

Fig. 1: Works Breakdown Structure of RCC Dam Construction

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B. Aggregates Production

Three types of aggregates produced based on specifi-cation namely T1 (63-25)mm, T2 (25-5)mm and T3 (5-0.75)mm which is coarse, medium and fine size of aggregates. Before RCC placement take place, the aggregates needs to be stockpiled at least 80% of total amount of aggregates re-quired to complete the project.

C. Foundation Preparation and Treatment

Site clearing and removing overburden are the first step in preparing the RCC dam foundation. After site clearing and removing the soil or overburden was done, rock scal-ing works are the next step that to be done. Rock scaling works are to determine the type of rock where the spec-ification state that, dam are to be sit on grade 2 or better rock. Foundation grouting are carried out is to strengthen the foundation and to ensure permeability of the foundation is high. The concept is to seal of the void, crack and fracture inside the rock that will strengthen the foundation for the dam to sit. The granite rock is permeable and as a result, fewer amounts (volume) of grouting are needed.

D. Diversion Culvert and River Diversion

Diversion culvert is a reinforced concrete structure with 15m diameter x 60 m long, complement with upstream and a downstream cofferdam. This is to allow the river flow trough cofferdam into the diversion tunnel and flow to downstream of the river.

E. RCC Mix Production

Continuous pugmill type of production plant is used for RCC production which is able to produce maximum capacity of 400 m3/hour [2]. This plant control proportion of aggre-gates component by volumetric, and cement and flyash by weight control. Due to weather condition in Malaysia, chill water is used to lower the temperature of RCC mix.

F. RCC Placement Works

At the beginning stage of RCC placement, RCC is to be placed at a series of 15 meter wide strips from downstream to upstream in 6 meter section. The thickness of placement is 300 millimeter and compacted by vibratory roller com-pacter. The time allowed from mixing of RCC, transport, spreading and compaction is 45 minute. Immediately after RCC has compacted, the field density test (FDT) was carried out using nuclear density meter to measure the density of RCC. Then, if the compaction achieved 98% above, the next layer is continued with the same method and routine. Figure 2 shows the routine of RCC placement works.

of upstream RCC dam where the erection of formworks was made as the level of RCC increases. Every increasing level of RCC, system formworks is lifted up using a mobile crane and carpenters tied bolt and nut of the formwork. Figure 3 shows the formworks at upstream of Batu Hampar dam. The precast concrete blocks embedded with steel plate are arranged by using mobile crane along the area where RCC is to be placed that form a downstream step as shown in Figure 4 which is the same method used in China 131 meter high Jiangya Dam, precast concrete block were used to form the step in downstream face of the dam [8].

Fig. 2: Routine of RCC Placement

Fig. 3: Carpenter Fixing the Formworks at Upstream of the Dam

Fig. 4: Concrete Block are Arrange to form a 600 m Downstream Step

1) RCC Placement Preparation

System formworks were used to form 65 m vertical wall

2) RCC Surface Preparation

When the RCC surface are left more than 8 hour, normal-ly due to plant breakdown or other issues that RCC place-ment are needed to be stopped, lift joint treatment needs to be performed before continuing a new layer of RCC. On the surface of old RCC layer, roughening was performed by using high pressure water jet blasting and the time to im-plement it is determined by hardening time which is 8 hours after compaction. Immediately after green cutting was done, bedding mortar is spread and the new layer of RCC place-ment is continued. This method was carried out to ensure the good bonding between joint lift which is between the lay-ers of RCC.

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3) Transporting, Spreading and Compacting

In the early stage of RCC placement works, RCC was transported by dump truck directly from the RCC mixing plant. The usage of dump truck was recognized as inefficient due to the site was at narrow steep side that lead to frequent needs to change and erect the temporary access for place-ment works. Therefore, the conveyor system is essential to transport RCC directly to dam site.

Conveyor system is required to transport RCC. However, due to the unavailability of technology in Malaysia, cost and other management issues, the conveyor system was not ap-plied at the beginning of the placement works. The convey-or system was used only when the RCC reached level 95 m (lowest level was RL 75m). Figure 6 shows conveyor system that has been apply at Batu Hampar dam.

RCC that was deposited from dump truck at the dam site was spread with 300 mm thickness by tracked dozer. Single drum vibratory roller compacter was used to compact the RCC. Single Vibratory rollers compacter makes one round trip over the concrete without vibration and continued with at least three round trips with vibration. Practically five (5) to seven (7) passes with vibration is enough to achieve the 98% compaction density. This method is fast and sufficiently accurate which contributes to uniformly compacted RCC [9].

Immediately after compaction was sufficiently carried out, density of the RCC or field density test was tested us-ing nuclear density meter. Figure 5 shows RCC Transporting and spreading and compacting process.

4) GERCC Application

Grout enriched RCC (GERCC) is produced by adding 3:1 or 4:1 water-cement ratio grout to the uncompacted RCC and then concrete vibrator used to compact the concrete. Grout was mixed using mixer and spread manually using bucket that as shown in Figure 4.7. The concept of using GERCC in RCC dam is to be applied at location of RCC place-ment where difficult to access by vibratory roller compacter. By applying GERCC it fills the void in RCC and create the smooth surface especially for upstream and downstream portion where it can be seen clearly after formworks have been dismantled. According to [10] at Kinta dam, GERCC are applied at the entire upstream and downstream faces (in-cluding the stepped spillway), the transition zone between RCC and rock abutments, drainage gallery walls, as well as encasement of waterstops, drains, and reinforcing steel.

5) Transverse Joint, Drainage Hole and Water Stop

At the upstream and downstream edges of the dam, galvanized steel plates were installed in advance as a con-traction joint at 15 m spacing. Then, water-stop and drainage holes were set in the upstream face of the dam. The drain-age hole and water stop were set at the upstream face of the dam prior the increase of RCC. Drainage hole function is to collect and convey the water that seep thru the dam and the water are drain out from drainage gallery to downstream river.

Transverse joints are installed to prevent temperature cracks in the concrete [11]. The installation took place after the completion of RCC placement layer and before it hard-

ens, and prior to the placement of the next layer. Transverse joint were cut by a vibratory blade machine and galvanized thin plates were installed in the cutting plane to prevent closing that has shown in Figure 7. Figure 8 shows the loca-tion of water stop, drainage hole and transverse joint.

6) RCC Curing

After placement, if the commencement of next layer of RCC is more than 24 hour, the concrete is cured by water ponding.

7) Laboratory Testing and Quality Control of the RCC Dam

Various quality control measures were executed at RCC dams so that the quality of materials is monitored carefully. Quality control methods that were applied at Batu Hampar dam is as below:

Fig. 5: RCC Transporting, Spreading, and Compacting, Nuclear Density Meter used to Check the Density Every Layer of RCC Placement Completed

Fig. 6: Conveyor System Apply at Batu Hampar Dam when the RCC Level Reach Higher Level

Fig. 7: Transverse Joint were Cut and Installed a Galvanize thin Plate at Batu Hampar Dam

Fig. 8: Water Stop, Drainage Hole and Transverse joint Location, from left, Workers apply GERCC at Upstream Face of the Dam

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1) Concrete Strength

Concrete strength is being monitored according to date the cylinder sample was taken and compressive strength test is conducted 7, 14, 28, 56, 96 and 180 day. It was carried out from the determination of RCC mix process until RCC placement works are completed. To monitor the compres-sive strength of RCC, compressive strength test and indirect tensile strength test is carried out at the stated days.

2) Density of RCC

Nuclear density meter is used to check the density of the RCC after compaction is carried out. The number of passes of the vibratory roller is manually counted to ensure the ad-equate compaction of RCC layer.

3) Vebe Consistency Test of RCC Mix

RCC concrete is dry and lean, the slump test cannot be used to measure its consistency [12]. The Vebe test with the standard container is conducted to monitor the consistency and workability of RCC mix. The test is conducted once every batch of RCC production. Optimum Vebe time is between 15 to 25 second, where it is the optimum in workability of RCC.

4) RCC Material Testing

RCC material testing is carried out in the early stage of RCC construction until the end of RCC construction works. The RCC material are tested to ensure the consistency of the RCC material. Table 1 shows the major material testing for Batu Hampar dam project.

Conclusions

The process of RCC dam construction in Malaysia start-ed from determination of RCC mix until RCC placement works. Before RCC placement started, it requires the prepa-ration process which involves the preparation of RCC mix, foundation preparation, and diversion works. Preparation of RCC mix includes finalizing the RCC mix and production of RCC. Further to RCC placement works, it requires the complex of construction method in order to place a large amount of mass concrete to form a gravity type of dam. The instrumentation is installed at the dam during construction stage to monitor overall performance of the dam structure to ensure dam safety.

References

[1] Warren, T., Denoyer, A., and Ulas, A., (2011). Taking advantage of RCC: Ted Warren discusses the history of roller compacted concrete (RCC) dam construction and its various applications and advantages to gravity dam design and construction. International Water Power and Dam Con-struction, 63(7), 20-23.

[2] Wagner, C. (2011). Batu Hampar dam - design and construction of an RCC dam. Dams and Reservoirs, 21(2), 77-90.

[3] Department of The Army, U. S. A. C. o. E. W., DC. (2000). Engineer Man-ual-Engineering and Design Roller-Compacted Concrete. [Engineer Manual]. EM 1110-2-2006

[4] Bass, R. P. (1991). Alternative Dam Construction Techniques. Proceed-ings of the 1991 Georgia Water Resources Conference, March 19-20, 1991, Athens, Georgia.

[5] Uribe, L., & Bosshart, D. (2002). Challenging RCC dam construction for the Ralco project in Chile. International Journal on Hydropower and Dams, 9(4), 95-99.

[6] Choi, Y., & Groom, J. (2001). RCC Mix Design—Soils Approach. Journal of Materials in Civil Engineering, 13(1), 71-76.

[7] Bass, R. P. (2003b). Rehabilitating Dams with Roller Compacted Con-crete Bridging the Gap (pp. 1-9)

[8] Forbes, B. A (2003), Using Sloped Layers to Improve RCC Dam Con-struction. Civil structures, Hydro Review Worldwide (HRW). Vol 11: Number 3.

[9] Nawy, E. G. (2008). Concrete construction engineering handbook Sec-ond Edition: Chapter 20 Roller Compacted Concrete, Salem USA: CRC LLC. Chapter 20 page 1-72

[10] Forbes, B. A, Hansen, Kenneth, D., Kitzgerald, Thomas, J. (2008) State of the Practice – Grout Enriched RCC in Dams.United States Society on Dams Annual Conference. April/May 2008. Portland Oregon, 1-17

[11] Shaw, Q. H. W. (2011). Chapter 2 : RCC Construction, RCC Mixes, RCC Instrumentation & RCC Dams Study. University of Pretoria: Ph.D. Thesis

[12] Nagataki, S., Fujisawa, T., & Kawasaki, H. (2008). State of art of RCD dams in Japan. Paper presented at the 50º Congresso brasileiro do con-creto, Salvado (1st Brazilian RCC Symposium september 2008)w

Table 1: Material Testing at Batu Hampar Dam

Table 2: Instrument Installed at Batu Hampar Dam

Material Test Frequency

CementChemical composition,

moisture content, specific gravity, finess, temperature

Every delivery to site

Flyash Same with cement testing Every delivery to site

Aggregates

Flakiness test, sieve analy-sis, specific gravity, sound-

ness, and others testing that related to aggregates.

Instructed by engineer

1 per day and every new

production of aggregates stockpile

E. Instrumentation

According to [11], the instrumentations installed in dams are for the purpose of:

1) Monitoring overall performance of the dam structure to ensure dam safety.

2) Monitoring the behaviour of the RCC dam.

Different instrumentation, monitors different character or behavior of the dam. The instrument that has been in-stalled at Batu Hampar dam are as stated in Table 4.2 below:

Every 10 m height of RCC dam, the instrumentation was installed by slotting the instrument in the RCC lift and the cable was laid inside the RCC by trenching it to cable riser pipe, before continuing RCC placement as usual.

Instrument Type Application

Vibrating wire piezometer Measure the pore water pressure

Combine biaxialInclinometer/magnetic extensometer

Ground lateral movement & settlement

Thermocouple Temperature of the dam

Vibrating wire strain gauge Measuring strain in mass of RCC dam

Vibrating wire pressure cell Measure the internal stress of RCC

Surface settlement/ deflec-tion point

Vertical and horizontal dis-placement of the dam

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Study on Mechanical Properties of Concrete with Various Slags as Replacement to Fine Aggregate

Abstract: An experimental programme is planned to study the effect of using copper slag (CS), granulated blast furnace slag (GBFS) and silicomanganese slag (SiMn) as fine aggregate on the properties of concrete. Sixteen concrete mixtures are pre-pared with different proportions of CS, GBFS respectively rang-ing from 0% to 100% and SiMn ranging from 0% to 50%. These sixteen concrete mixes are evaluated for mechanical proper-ties and durability. Addition of 60% CS and GBFS respectively as sand replacement yielded comparable or higher strength than control concrete and there is reduction in strength at all replacement levels of SiMn.

India, in recent years is witnessing a rapid growth and inno-vative development in construction industry. The extended use of concrete and its materials involve use of available natural re-sources. Natural resources in India are depleting, contrasting-ly, there is substantial increase in generation of wastes from the industries. The sustainable development in concrete technol-ogy and construction involves the use of waste and innovative materials in order to replace the depletion of natural resources and find alternative ways for conserving the environment. The materials like - slags, quarry dust, manufactured sand, munic-ipal incineration waste ash, bottom ash, recycled sands from construction and demolished waste, etc are used as alternative materials for replacement or full substitution of sand.

Aggregates are considered as one of the main filler con-stituents of concrete as they occupy 50 – 80% of concrete vol-ume. The concrete industry globally consume over 8-12 billion tonnes of natural aggregates annually. 1Recently natural sand is becoming scarce in availability and costly, because of its de-mand by the construction industries. In this context, construc-tion industry and researchers are looking for easily available, cheap and sustainable alternative materials to natural sand. Latest trends and growth in concrete technologies are focusing on sustainable development by using industrial by-products as ecological raw materials in concrete.

Various types of industrial slags, such as CS, GBFS are ex-tensively used in concrete as fine aggregate. In duration about 33 million tonnes of copper slag is being generated annually worldwide, among which, India is contributing 6 – 6.5 million tonnes. Replacement with copper slag may result 20% high-er strength to that of control concrete for 50% replacement. Around 10 million tonnes of GBFS is currently being generated

in the country from iron and steel industries.2 Silicomangane-seis smelted in electric or a blast furnace, the process creates ferromanganese and silicomanganese. The slag is then fur-ther processed by crushing and washing to remove as much of the remaining metal as possible. The remaining ore is then screened and sold for use in cement manufacture as an ingre-dient, and concrete production as a cementitious, reactive ag-gregate. SiMn often contains 15% manganese oxide that is the most common by-product of the process.

The objective of this research program is to identify the al-ternative sustainable materials which replace the natural riv-er sand without morphing its strength and durability aspects of concrete and this investigation presents the results from planned experimental tests conducted on concrete replacing CS, GBFS and SiMn as fine aggregate at constant w/c ratio.

Materials

Cement: The cement used in this study is Ordinary Portland Cement (OPC), 53 grade.

Fine aggregate :The fine aggregate used in this investiga-tion is clean river sand, from Srikakulam.

Copper slag :Copper slag used in this project is from Hin-dustan Copper Limited, Kolkata.

Granulated blast furnace slag: Granulated blast furnace slag used in this project is from Vizag Steel Plant, Visakhapa-tnam.

Silicomanganese slag: In this project Silicomanganese slag is from Vizag Steel Plant, Visakhapatnam.

Ramagiri Anudeep1, K.Venkata Ramesh2, V. SowjanyaVani3

1Post Graduation Student, Master of Technology (Structural Engineering and Natural Disaster Management), GITAM University, Visakhapatnam2Professor, Department of Civil Engineering, GITAM University, Visakhapatnam3Assistant Professor, Department of Civil Engineering, GITAM University, Visakhapatnam

Major Com-ponents CS GBFS SiMn

SiO2 (Com-bined as Silicate)

33 – 35% 36.67% 43.49%

FeO 40 – 44% 2.2% 0.61%

Al2O3 4.0 – 6.0% 15.36% 18.50%

CaO 0.8 – 1.5% 37.08% 17.61%

MgO 1.0 – 2.0% 9.21% 6.49%

MnO - - 11.52%

Cu 0.6 – 0.9% - -

CONCRETE: AGGREGATE REPLACEMENT

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test results showed that there is comparable particle size dis-tribution with the gradation requirements for concrete sand as shown in Fig. 1. CS, GBFS and SiMn have comparable grada-tions.

Coarse aggregate: In this present investigation, locally available crushed stone aggregate of size 20mm and down are used.

Water: In this investigation, potable water is used.

Experimental Programme

The mix proportion chosen for this study is shown in Table 3. Sixteen concrete mixtures with different proportions of CS, GBFS ranging from 0% to 100% and SiMn ranging from 0% to 50% are considered as shown in Table 3. The effect of slags as replacement to sand on workability is studied. The specimens are demoulded after 24 hours and cured in water for 7 and 28 days.

Testing Procedure:

After curing the concrete samples, the following tests are conducted:- 7 and 28 day cube compression strength test, accordance

with IS: 516-1959 using a loading rate of 400 Kg/min.- 7 and 28 day cube split tensile strength test, accordance

with IS: 5816-1999 using a loading rate of loading 2.4 N/min.

S 0.8 – 1.2% - -

Free Silica < 0.5% - -

Ni 0.01- 0.03% - -

Pb 0.01 - 0.03% - -

Zn 0.2 – 0.3% - -

Bi 0.01 - 0.02% - -

Co 0.04 - 0.13% - -

Others - - 1.78%

Table 1 – Chemical composition of slags

Table 2 – Physical properties of slags

Major Com-ponents CS GBFS SiMn

Particle size, Shape

Glassy, Mul-tifaceted

Angular, Roughly Cubical

Angular, Medium rough

Appearance Blackish gray, Glassy Gray, Glassy Light green-

ish gray

Hardness> 5-7 Mohr’s scale

> 5-6 Mohr’s scale

-

Bulk density at 250C (gm/

cm3)1.8-2.2 1.2 – 1.5 Approx 3

pH 6.5 8 – 10 8.80

Conductivity Nil Nil Nil

Weight loss on ignition

(%)

1.75-2.0at 9000C 1.8 1.8

Moisture content (%) < 0.1 6% -

Specific gravity 2.78 2.15 1.57

Grading limit Zone I Zone II Zone I

Table 3 - Concrete design mix proportions

Cement(kg/m3)

Sand(kg/m3)

Coarse aggre-

gate(kg/m3)

Water(kg/m3) w/c ratio

400 667 1140 180 0.45

Results and Discussion

Effect of CS, GBFS and Simn Substitution as Fine Aggregate on Concrete Properties

Workability

From Table 4, the workability of concrete increases signifi-cantly with the increase in CS content as sand replacement. The considerable increase in the workability with the increase of CS quantity is attributed to the low water absorption charac-teristics of CS and its smooth, glassy surface. There is surplus quantity of free water even after the absorption for hydration process when compared to sand. The increase in the workabil-ity may have a beneficial effect on concrete where the concrete mixes with low water-to-cement ratios are considered, such that concrete can improve workability, greater strength and improve durability than the conventional concrete mix.

The workability of concrete decreases remarkably with the increase in GBFS and SiMn content in the concrete mixes indi-vidually. The considerable decrease in the workability with the increase of GBFS and SiMn respectively quantity can be accred-ited to the high water absorption and its high surface area.

Compressive Strength

From Table 4, the compressive strength of concrete in-creased as CS replaced to sand increased up to 60%. Beyond

CONCRETE: AGGREGATE REPLACEMENT

The chemical composition and physical properties of CS, GBFS and SiMn are presented in Table 1 and Table 2.

Gradation test is conducted in accordance with IS: 383 – 1970 on all the samples -CS, GBFS and SiMn and sand. The

Fig 1: Particle size distributions of CS, GBFS, SiMn and sand

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that the compressive strength reduced noticeably due to in-crease in the excess free water in the mix. The optimum com-pressive strength is achieved at 60% replacement level of CS.

The compressive strength of concrete increased as GBFS reached 60% replacement level. Beyond that the compressive strength reduced considerably due to the increase in water ab-sorption characteristics of slag and its high surface area since finer than sand and the compressive strength of concrete de-creased for all replacement levels of SiMn. The compressive strength reduced significantly due to the increase in water absorption characteristics of GBFS and SiMn individually. The water absorption of GBFS and SiMn at higher replacement lev-els made the water content of the mix crouched than actually required. This reduced the binding of the constituents, thereby, reducing the strength characteristic within hardened concrete.

Split Tensile Strength

From Table 4, the split tensile strength of concrete in-creased as CS replacement to sand increased up to 60%. Be-yond that the split tensile strength reduced prominently due to the increase in the free water which is excess in the mix. The op-timum split tensile strength is achieved at 60% replacement of

CS, which is 19.86% compared to the control mix. The split ten-sile strength of concrete increased as GBFS quantity increased up to 100%. The highest split tensile strength achieved by 100% replacement of GBFS; there is an increase in the strength to 35.30% when compared to control mix. Split tensile strength of concrete decreased for all replacement levels of SiMn. The split tensile strength reduced due to the increase in water absorp-tion characteristics of slag and its high surface area.

Effect of slag substitution as fine aggregate on carbonation of concrete

The effect of CS, GBFS and SiMn replacement as fine ag-gregates on the CO2 effect is presented in Table 4, The Ca(OH)2 of concrete is unaffected by CO2 penetration and the colour turned out to be purple for all the sixteen mixes adopted.

Table 4 – Average strength results of concrete at 7 and 28 days of curing.

Cost Comparison of Fine Aggregate

Many cities in India are experiencing scarcity in the supply of sand for the constructional use. For instance in a place like Visakhapatnam, (A.P) one cubic meter of sand costs ̀1200.

Mix no. Mix type Mix Nota-tion

Slump(mm)

Density(kg/m3)

Average strength (kN/m2)

(fcu)a (fcu)b (fcs)a (fcs)b

1 Control (100% S) Control 50 2517.03 35.62 47.84 2.80 3.20

2 20% CS + 80% S CS20 20 2569.18 31.84 45.18 2.73 2.89

3 40% CS + 60% S CS40 30 2575.40 33.92 45.62 2.80 3.46

4 50% CS + 50% S CS50 30 2592.59 35.55 48.74 3.18 3.53

5 60% CS + 40% S CS60 50 2652.74 39.40 53.77 3.41 3.84

6 80% CS + 20% S CS80 Collapse 2734.81 37.77 51.99 3.53 3.77

7 100% CS CS100 Collapse 2798.81 34.14 47.84 3.25 3.65

8 20% GBFS + 80% S GBFS20 30 2478.22 28.88 45.77 2.85 3.20

9 40% GBFS + 60% S GBFS40 20 2471.11 29.47 46.66 2.99 3.58

10 50% GBFS + 50% S GBFS50 15 2427.85 31.84 53.62 3.08 3.72

11 60% GBFS + 40% S GBFS60 5 2409.77 32.29 55.11 2.82 3.72

12 80% GBFS + 20% S GBFS80 0 2370.07 33.17 43.55 2.85 3.84

13 100% GBFS GBFS100 0 2362.96 37.10 43.69 2.66 4.33

14 20% SiMn + 80% S SiMn20 35 2434.96 27.25 36.63 3.01 3.30

15 40% SiMn + 60% S SiMn40 10 2295.70 19.84 28.51 2.31 2.54

16 50% SiMn + 50% S SiMn50 0 2283.55 17.47 27.03 2.02 2.54

S – Sand, CS – copper slag, GBFS – granulated blast furnace slag, SiMn – silicomanganese slag.(fcu)a – Average cube compressive strength at 7 days, (fcu)b – Average cube compressive strength at 28 days(fcs)a – Average tensile strength at 7 days, (fcs)b – Average tensile strength at 28 days

Table 4 – Average strength results of concrete at 7 and 28 days of curing.

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Due to the existence of steel plant this place has availability of different slags in abundance. One cubic meter of granulated blast furnace slag costs about ̀400 – 500, one cubic meter of silicomanganese slag costs about ̀250 – 350. Copper slag be-ing imported from Kolkata the slag costs about ̀1700 – 1800. At other places, where sand is available at reasonable costs, slag is availableat cheaper rates or at comparatively lower pric-es. Using of slag in constructions can minimise the depletion of natural sand resources and can improve concrete properties.

Conclusions

Based on the literature review and the results from the experimental work the following conclusions can be made. Aggregate replacements have a significant effect on the per-formance of the fresh concrete mix and also the strength char-acteristics. One of the objectives of aggregate replacement is to produce sustainable concrete which is economical, needs relatively low amount of natural resources and makes use of the industrial by-products.

- The workability improved with increase in the replacement of CS percentage due to smooth nature, there isadecrease in the workability to higher GBFS replacement due to its an-gular nature, fineness and high water absorption property. For SiMn replacement the workability decreased with the increase in the replacement levels.This is due to angular nature and high water absorption property.

- The density of the concrete incorporating sand with the CS

increased with increase in the replacement due to high CS density.The density of concrete incorporating GBFS decreased with increase in replacement levels due to low GBFS density. Replacing sand with SiMn in concrete ob-served reduction in the density since SiMnhas low density.

- There is more than 12% improvement in the compressive strength of concrete with 60% replacement of CS in con-crete. It is observed, about 15% improvement in the com-pressive strength of concrete with 60% replacement of GBFS in concrete. Thus 60% replacement of CS, GBFS re-spectively is optimum to improve strength characteristics. There is a reduction in strength of concrete at all replace-ment levels with SiMn to sand.

- Split tensile strength of concrete is increased by 20% at 60% CS replacement and 35% at 100% GBFS replacement. There is reduction in split tensile strength of concrete re-placed with SiMn at all replacement levels.

- Replacing sand with CS, GBFS and SiMn in concrete has no effect towards CO2.

Comparative Discussion

GBFS may be adopted as replacement to fine aggregate compared to CS and SiMn to enhance the concrete strength, durability and iseconomical.CS can be adopted where the con-crete mix has low water-to-cement ratio. Considering cost fac-tor CS is not economical compared to GBFS and SiMn.

References

- Khalifa S. Al-Jabri, Makoto Hisada, Abdullah H. Al-Saidy, S.K. Al-Or-aimi.,Performance of high strength concrete made with copper slag as a fine aggregate,Construction and Building Materials, 2009,Vol. 23,pp. 2132–2140.

- Akshay C. Sankh, Praveen M. Biradar, Prof. S. J Naghathan, Man-junath B. Ishwargol., Recent trends in replacement of Natural Sand with Different Alternatives,International Conference on Advances in Engineering & Technology – 2014 (ICAET-2014).

- Dr. KodeVenkata Ramesh, D. SreeRamachandraMurty, P. Swarna Kumar., Appraisal of Crushed Stone Dust, as fine aggregate in struc-tural concrete,Concreting;CE&CR,July 2007.

- Khalifa S. Al-Jabri, Makoto Hisada, Salem K. Al-Oraimi, Abdullah H. Al-Saidy., Copper slag as sand replacement for high performance concrete,Cement& Concrete Composites, 2009,Vol. 31, pp. 483–488.

- Khalifa S. Al-Jabri, Abdullah H. Al-Saidy, RamziTaha., Effect of cop-per slag as a fine aggregate on the properties of cement mortars and concrete,Construction and Building Materials, 2011, Vol. 25, pp. 933–938.

- Bipra Gorai, R.K. Jana, Premchand., Characteristics and utilisation of copper slag - a review,Resources, Conservation and Recycling, 2003, Vol. 39, pp. 299-/313.

- Mostafa Khanzadi, Ali Behnood., Mechanical properties of high-strength concrete incorporating copper slag as coarse aggregate,-Construction and Building Materials, 2009,Vol. 23, pp. 2183–2188.

- Isa Yuksel, TurhanBilir., Usage of industrial by-products to produce plain concrete elements,Construction and Building Materials,2007, Vol. 21, pp. 686–694.

- Liu Chunlin, ZhaKunpeng, Chen Depeng., Possibility of concrete pre-pared with Steel Slag as Fine and Coarse Aggregates: A Preliminary Study,Procedia Engineering, 2011, Vol. 24, pp. 412 – 416.

- Omer Ozkan, Isa Yuksel, OzgurMuratoglu., Strength properties of concrete incorporating coal bottom ash and granulated blast fur-nace slag,Waste Management, 2007, Vol. 27, pp. 161–167.w

Fig 2: Compressive strength of concrete replacing different slags as fine aggregate at 7 days and 28 days

Fig 3: Split tensile strength of concrete replacing different slags as fine aggregate at 7 days and 28 days

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Influence of Ultrafine Natural Steatite Powder on Setting Time and Strength Development of Cement

Abstract: This paper deals with the setting time and pozzola-nic activity of cement when ultra fine natural steatite powder (UFNSP) is used as replacement for cement. Initial setting time, final setting time, and mortar cube strength were studied, due to the replacement of ultra fine natural steatite powder with cement at 5%, 10%, 15%, 20%, and 25% by mass of cement. The setting time of fresh cement-binder paste and compressive strength of mortar cubes are observed. Scanning electron mi-croscopy (SEM) and X-ray diffraction (XRD) were applied to in-vestigate the microstructural behaviour and chemical element distribution inside cement-binder matrix. Results indicate that the length of dormant period is shortened. The replacement of ultra fine natural steatite powder with cement reduces initial setting time, and final setting time and increases mortar cube compressive strength.

Steatite is a type of metamorphic rock, largely composed of talc ore, rich in magnesium. It is composed of hydrated mag-nesium silicate: Mg3Si4O10(OH)2. Steatite is the softest known mineral and listed as 1 on the Mohs hardness scale. It is already used in paint industry, particularly in marine paints and protec-tive coatings. This is used in ceramics due to its high resistivity, very low dielectric loss factor, and good mechanical strength. Addition of steatite powder increases the viscosity and mechan-ical properties of feed stock. The thermal properties of steatite are also good [1]. Massive steatite cut into panels is used for switchboards, for acid proof tabletops in laboratory, laundry, and kitchen sinks, and in tubs and tanks, as well as for lining alkali tanks in paper industry. Due to its high melting point (1630°C) [2], steatite can be used in refractory and fire places. It is also quite useful in sculpturing. When fabricated by a combined method of high energy ball milling, cold pressing, and sintering, it improves thermal properties of ceramics [3, 4]. Cement mor-tars prepared with steatite particles have been investigated for restoration of sculptures and other craftworks. It was observed that the highest compressive strength (43 MPa) and lowest ap-parent porosity (0.19%) are achieved when steatite particles are coarser (ranging from 1.41 mm to 0.42 mm), and 40% of poly-meric phase is employed [5]. A special cement-based mortar containing additions of fine powder waste from mineral ex-traction of steatite has been developed in Brazil, as a composite material for restoration of steatite elements [6]. The steatite is mostly used in electrotechnics. Stabilization of protoenstatite in

steatite body is achievable by the development of small crystals [7]. Improper selection of parameters led to undesired problems such as separation of the powder-binder mixture and formation of collapses and cracks on the structure of the moulded parts. The optimum moulding parameters of the feed stocks for the zigzag shaped mold are determined to be at an injection pres-sure of 80 to 140 MPa at barrel temperature of 190 to 230°C [8]. When a property of powder injection moulded steatites is inves-tigated, sintered at 1300°C for 4 hours, a theoretical density of 98%-99% is achieved. Three-point bending and tensile test was performed on the samples sintered at 1200°C to 1300°C. The maximum three-point bending and tensile strength values are found to be 154 MPa and 47 Mpa, respectively [9]. Indian steatite, mined in Rajasthan and Andhra Pradesh, is comparable with the best quality available in other countries. The steatite mined in India, with more than 92% brightness, less than 1% Fe2O3, and less than 1.5% CaCO3, is preferred for exports [2]. Indian steatite is considered to be the second best in the world next to “Italian steatite.” The UFSP used in this experiment develops M-S-H gel; hence the comparative study of C-S-H and M-S-H is vital. On account of the basic structural difference between the two gel types, M-S-H and C-S-H are essentially immiscible [10]. Magnesium hydroxide (Mg(OH)2 aka brucite) is a good starting point for the development of low pH cements. pH value of ex-cess brucite in equilibrium with water is calculated to be around pH 10.5 [11]. Hence, in principle, cement based on the hydration of MgO powder, calcined at low temperature to ensure fast hy-dration, should yield the desirable pH. According to Zhang et al. [11] high MgO contents do not affect the pH, whereas high silica fume content results in a pH closer to 9.5. Both MgO and silica fume composition have potential applications for the en-capsulation of wastes containing heavy metals [11]. In the pres-ent research work, effect of UFNSP powder on setting time and strength development on cement is investigated.

Materials and Experimental Methods

Raw MaterialsCement. Ordinary portland cement conforming to IS: 8112-

1989 (Indian Standard Designation, IS: 8112-1989) is used for mortar mixtures; the cement used in this study belongs to type I of ASTM. The physical and chemical properties are given in Table 1.

K. Sudalaimani1 & M. Shanmugasundaram2

1Department of Civil Engineering, Thiagarajar College of Engineering, Thiruparankundram, Madurai2Department of Civil Engineering, Kalasalingam University, Srivilliputhur

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Fine Aggregates. Standard natural sand having hard, clean, strong, durable, uncoated particles and meeting the require-ments of the specifications (ASTM C144-11) with specific gravity of 2.65 is used as fine aggregate.

Water. In the present investigation, potable water is used for mixing and curing.

Mineral Admixture. UFNSP obtained from UltraFine Miner-al Pvt. Ltd., India, is used as natural admixture. UFNSP is man-ufactured by using high quality crushers and superfine grind-ers. UFNSP is finer than cement. The physical and chemical properties are given in Table 1.

Consistency of Cement

The basic aim is to find out the water content required to produce a cement paste of standard consistency as specified by the IS: 4031 (Part 4)-1988. The principle is that standard consis-tency of cement is that consistency at which the Vicat plunger penetrates to a point 5–7 mm from the bottom of Vicat appara-tus, conforming to IS: 5513-1976. Approximately 400 g of cement is mixed with a weighed quantity of water. The time of gauging should be between 3 and 5 minutes. Fill the Vicat mould with paste and level it with a trowel. Lower the plunger gently till it touches the cement surface. Then release the plunger to sink into the paste. Note the reading on the gauge and repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 5 to 7 mm.

Initial and Final Setting Time (IST and FST)

How to calculate the initial and final setting time as per IS: 4031 (Part 5)-1988 by Vicat apparatus conforming to IS: 5513-1976? Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consisten-cy. Start a stopwatch the moment water is added to the cement. Fill the Vicat mould completely with the cement paste gauged as above. With the mould resting on a nonporous plate, smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared in the mould is the test block.

Determining Initial Setting Time (IST). Place the test block under the rod bearing the needle. Lower the needle gently in order to make contact with the surface of the cement paste. Release quickly, allowing it to penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a

point 5.0 0.5 mm measured from the bottom of the mould. Ini-tial setting time is the period elapsing when water is added to the cement and the needle fails to pierce the test block by 5.0 0.5 mm measured from the bottom of the mould.

Final Setting Time (FST). Replace the above needle by the one with an annular attachment. The cement is considered to finally set, when the gentle application of the needle makes an

Cement UFNSP

Physical properties

Blaine surface area (m2/Kg)

Particle mean dia. (μm)

Density

Loss of ignition

380

<32

3.1

2%

750

<5

2.7

3.33%

Chemical properties

SiO2

Al2O3

MgO

Fe2O3

CaO

23%

4.20%

0.20%

1.20%

63%

62.67%

0.24%

33.26%

0.30%

0.20%

Table 1: Physical and chemical properties of cement and UFNSP

Figure 1: Scatter plot on strength of mortar cubes with standarddeviation.

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impression therein, while the attachment fails to do so. Final setting time is the period elapsing when water is added and the needle makes an impression on the surface of the test block.

Compressive Strength on Mortar Cubes

Mortar cubes used in this investigation were 70.6 mm 70.6 mm 70.6 mm confirming to IS 10080-1982. The specimens were prepared in ratio of cement : sand as 1 : 3 and W/B ratio as 0.47. These specimens are cast in three layers, in accordance to IS 10080-1982. Each layer is well compacted by a tamping rod of 12 mm diameter. After the compaction the top surface is leveled using a trowel and left for 24 hours to dry in room tem-perature of 28°C with 60% humidity. On the next day, at room temperature of 29°C and 54% humidity, the mortar cubes are kept inside a curing tank filled with portable water. The speci-mens are tested with a 2000 kN capacity hydraulic compression testing machine, as per IS: 4031-1982 (Part 6). Altogether 108 mortar cubes (6 Mix IDs x 18 specimens) were cast and were tested for compressive strength.

Scanning Electron Microscopy and X-Ray Diffraction Studies

The specimen is studied by Scanning Electron Microscopy and XRD Patterns. Samples for scanning electron microsco-py (SEM) analysis are taken near the surface (0-1 mm depth) of specimens. Micro structural studies utilized SEM (HITACHI S-3000H, Japan) equipped with EDAX analyzer for micro struc-tural observations of the surfaces, which is coated with evapo-rated copper for examination. SEM analyses is done at a max-imum magnification of 20,000 x with energy 15 keV and a high resolution of 3.5 nm. For this analysis, samples of size 10 mm cubes are cut with a saw cutter on 28th day. The XRD analysis is carried out with a Siemens D-5000 X-ray diffractometer with Cu K-beta radiation and 2 scanning with a step size of 0.02° and a measuring time of 10.00 Deg/minute. A voltage of 40 kV and current of 15 Ma is used. Samples are collected from the cubes after 28 days of water curing and powdered in ball mills to pass through the sieve size of 90μ.

Table 2: Consistency, IST, and FST

Table 3: Compressive strength of mortar cubes

S.No Mix IDs % replacement of UFNSP

% consistency of water for binder IST in minutes FST in minutes

1 C0 0 24 30 360

2 C5 5 28 25 330

3 C10 10 29 20 300

4 C15 15 31 20 300

5 C20 20 34 25 330

6 C25 25 37 40 450

S.No Mix IDs3-day

strength inMPa

SD in MPa

CO-VARin %

7-daystrength in MPa

SD in MPa

CO-VARin %

28-daystrength in

MPa

SD in MPa

CO-VARin %

1 C0 29.00 2.39 8.23 37.00 2.19 5.29 45.00 2.00 4.44

2 C5 33.00 1.90 5.75 40.00 1.79 4.47 49.00 1.38 2.78

3 C10 42.00 1.10 2.61 47.00 1.10 2.33 52.00 1.10 2.11

4 C15 44.00 1.10 2.49 49.00 0.89 1.83 52.00 0.84 1.59

5 C20 37.00 2.37 6.40 45.00 1.79 3.98 48.00 1.67 3.49

6 C25 23.00 3.90 16.95 30.00 2.45 8.16 39.00 2.10 5.38

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Results and DiscussionsConsistency of Cement

From Table 2 the consistency of binder material is ob-served. The consistency is found to continuously increase as the percentage replacement of cement with UFNSP increases. The water consistency increases for C5, C10, C15, C20 and C25 at 4%, 5%, 7%, 10%, 13% when compared with C0. This may be due to higher fineness of UFNSP and higher water absorption property.

Setting Time

From the experimental design, the maximum, minimum and average values of IST and FST are shown in Table 2, togeth-er with the main effects and UFNSP interactions. The values are reported as relative values with respect to ordinary Portland cement paste, 30 and 360 minutes for IST and FST respectively. The IST for C5, C10, C15 and C20 decreases by 5minutes, 10 minutes, 10 minutes, and 5 minutes respectively and for C25 IST increases by 10 minutes when compared with C0 mix. Sim-ilarly the FST for C5, C10, C15 and C20 decreases by 30 min-utes, 60 minutes, 60 minutes, and 30 minutes respectively and for C25 FST increases by 90 minutes when compared with C0 mix. From the above results it is observed that IST and FST de-creases when percentage of UFNSP replacement increases up to 20%, but there is a sudden increase in IST and FST on C25 specimen which may be due to excess UFNSP.

Compressive Strength of Mortar Cubes

The strength attained during 3 days, 7 days and 28 days on mortar cubes are experimentally tested for 6 specimens on

Figure 2: SEMimages of specimens with 20000 x magnification: (a) C0 specimen, (b) C5 specimen, (c) C10 specimen, (d) C15 specimen, (e)C20 specimen, and (f) C25 specimen.

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each age and their average results are shown in Table 3 and Figure 1. The strength of mortar cubes of C5, C10, C15, C20 and C25 are compared with C0 mix. The compressive strength on 3 days for C5, C10, C15 and C20 increases by 13.8%, 44.8%, 51.7% and 27.5%. The strength of C25 decreases by 20.7%. On the 7th day for C5, C10, C15 and C20 increase by 8.1%, 27.02%, 32.43% and 21.6%. The strength of C25 decreases by 18.9% and on the 28th day for C5, C10, C15 and C20 increases by 10%, 15.6%, 16.7% and 6.7%. The strength of C25 decreases by 13.3%. Thus the above results show the Mix C5, C10, C15 has a considerable increase in terms of strength and also the strength is easily attained on its early ages like 3 days and 7 days. Data on the variation in compressive strength of mortar cubes is shown in Table 3 and Figure 1. The Standard Deviation (SD) and Coef-ficient of Variation (CO-VAR) of the compressive strength on 3 days, 7 days and 28 days shows decrease in SD and CO-VAR with increase in ages. The maximum SD is observed in C25, the lowest SD is observed at C10 and C15. The SD for C0 and C20 shows almost equal values. C5 shows lesser SD than C0 but more than C10 on all age. The CO-VAR fell from maximum val-ue on 3 days to the lowest on 28 days for all specimens. The data shows that C15 is the specimen having Lowest SD and CO-VAR, with maximum strength, which also ensures that C15 mix is the most reliable of all mix IDs. The C25 specimens have highest SD and CO-VAR and lowest strength and are identified as the inferior specimen of all other specimen.

Microstructural Analysis

The results obtained in SEM and XRD analysis are shown in Figures 2 and 3.

The analysis shows that the best results are obtained from adding 15% of UFNSP. The images obtained in SEM are shown in Figure 2. Figure 2(a) shows the micrograph of C0; it consists of fine particles, which appear to have agglomerated into larg-er groups of particles. Figure 2(b) shows the micrograph of C5 specimen; the extent of coverage is substantial but not enough material has formed to create a continuous film on the surface of the particle. Some regions show the traces of no hydration products and absence of deposition of hydration products. Fig-ures 2(c) and 2(d) show the micrograph of C10 and C15 speci-mens, respectively. This shows that due to the abundance of the hydration products the appearance has changed from small isolated particles to tangled web of flake-like crystals. The hy-dration products consist of a mixture of phases as is typical for portland cement. For example, portlandite is visible at some regions, intermixed with reticulated C-S-H (or) M-S-H gel. Figure 2(e) shows the micrograph of C20; it is similar to that of C0; but there are no empty regions without hydration products, and hence this C20 specimen mechanical behaviour is similar to that of C0. Figure 2(f) shows the micrograph of C25 speci-men; this shows that the flake-like crystals start disappearing and form into cloudy disintegrated form. This also confirms the loss in bonding effect. A study on microstructure of samples C0, C5, C10, C15, C20, and C25 is made. The results show that the UFNSP particles have been covered in a continuous pattern for C5, C10, and C15 specimens and pattern of very small parti-cles is identified for C20 and C25 specimens. The patterns for C20 specimen are similar to C0 specimen. The C25 specimen shows lack of bonding and formation of independent particles without bond, which may be the cause of reduction in strength.

Figure 3 shows the X-ray diffrograms of C0, C5, C10, C15, C20, and C25 mortars, respectively. The main compounds are quartz (SiO2), calcite (CaCO3), portlandite (Ca(OH)2), and bru-cite (Mg(OH)2). The X-ray diffrograms show increase in quartz when UFNSP is added. The calcite is similar in all specimens. The intensity of brucite increases as percentage replacement of UFNSP increases. The peaks for all specimens indicate the presence of quartz, calcite, and portlandite and very small quantity of brucite. The intensity of portlandite peak is slightly higher in C10 and C15 when compared to other specimens.

Figure 3: XRD patterns of C0, C5, C10, C15, C20, and C25 mortars. Q: quartz; C: calcite; P: portlandite; B: brucite.

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The increase in C15 strength is due to the right combination of portlandite, calcite, and brucite. The SEM image and X-ray diffrograms (Figures 2(d) and 3) of C15 show the wider pres-ence of dense portlandite and brucite which supports faster hydration reaction. The reduction in calcite leads to decrease in carbonation process. Hence maximum strength is attained in C15. Figure 3 shows that the intensity of portlandite is very low for C25. The increase of brucite (Mg(OH)2) in combination with reduction of portlandite leads to the conclusion that port-landite most probably reacted with magnesium. The very low solubility of brucite favours the consumption of calcium hydrox-ide (Ca(OH)2) [12]. The reduction in strength of C25 specimen is attributed to the pozzolanic activity and pore structure. Since replacement of UFNSP reduces the content of portlandite, the hydration reaction and pozzolanic activity decreases. Hence the strength contribution from this process is lower than C0.

Conclusion

From the present study it can be concluded that replace-ment of UFNSP with cement results in decrease of IST and FST, but the consistency of binding material increases. This shows the increase in requirement of water to produce cement paste. The compressive strength of mortar cube increases during its early stages. The maximum compressive strength in 3, 7, and 28 days is observed at C15. The improvement in strength in C5, C10, C15, and C20 is nominal at all stages and normalizes in 28 days. The C25 shows decrease in strength and increase in IST and FST. It is also observed that replacing UFNSP with cement results in improvement of microstructure of cement mortar. The C5, C10, and C15 specimens show denser microstructur-al bond when compared to other specimens. The availability of denser hydration product (portlandite) in C15 specimen is iden-tified. The C20 specimen shows micro structural similarity to control specimen. The reduction in strength of C25 specimen is attributed to the pozzolanic activity and pore structure. C25 shows disintegrated microstructure and very low intensity of portlandite. From all the above discussion it is concluded that the suitable UFNSP replacement percentage should not ex-ceed 20%.

Conflict of Interests

The authors declare that there is no conflict of interests re-garding the publication of this paper.

Acknowledgments

The authors of this paper express their gratitude to the management of Thiagarajar College of Engineering (TCE). The authors wish to express their thanks to the department for fa-cilitating this work.

Publishers Note: This paper was first published in - Advances in Materials Science and Engineering

References

1. C. Karatas, A. Kocer, H. I. Ünal, and S. Saritas, “Rheological properties of feedstocks prepared with steatite powder and polyethylene-based thermo-plastic binders,” Journal of Materials Processing Technology, vol. 152, no. 1, pp. 77–83, 2004.

2. Ministry of mines, Indian Bureau of Mines, Indian Mineral Year Book, 2011.

3. H. Gökçe, D. Agaogullari, M. L. Öveçoglu, I. Duman, and T. Boyraz, “Char-acterization of microstructural and thermal properties of steatite/cordierite ceramics prepared by using natural raw materials,” Journal of the European Ceramic Society, vol. 31, no. 14, pp. 2741–2747, 2011.

4. P. Rohan, K. Neufuss, J. Matejícek, J. Dubsky, L. Prchlík, and C. Holzgart-ner, “Thermal and mechanical properties of cordierite, mullite and steatite produced by plasma spraying,” Ceramics International, vol. 30, no. 4, pp. 597–603, 2004.

5. F. P. Cota, R. A. A. Alves, T. H. Panzera, K. Strecker, A. L. Christoforo, and P. H. R. Borges, “Physical properties and microstructure of ceramic-polymer composites for restoration works,”Materials Science and Engineering A, vol. 531, pp. 28–34, 2012.

6. T. H. Panzera, K. Strecker, J. D. S. Miranda, A. L. Christoforo, and P. H. R. Borges, “Cement—steatite composites reinforced with carbon fibres: an alternative for restoration of Brazilian historical buildings,” Materials Re-search, vol. 14, no. 1, pp. 118–123, 2011.

7. W. Mielcarek, D. Nowak-Wozny, and K. Prociów, “Correlation between Mg-SiO3 phases and mechanical durability of steatite ceramics,” Journal of the European Ceramic Society, vol. 24, no. 15-16, pp. 3817–3821, 2004.

8. S. Erguney, C. Karatas, H. I. Unal, and S. Saritas, “Investigation of the mold-ability parameters of PEG based steatite feedstocks by powder injection molding,” International Polymer Processing, vol. 26, no. 2, pp. 143–149, 2011.

9. L. Urtekin, I. Uslan, and B. Tuc, “Investigation of properties of powder injec-tion-molded steatites,”Journal of Materials Engineering and Performance, vol. 21, no. 3, pp. 358–365, 2012.

10. D. R. M. Brew and F. P. Glasser, “Synthesis and characterisation of magne-sium silicate hydrate gels,”Cement and Concrete Research, vol. 35, no. 1, pp. 85–98, 2005.

11. T. Zhang, C. R. Cheeseman, and L. J. Vandeperre, “Development of low pH cement systems forming magnesium silicate hydrate (M-S-H),” Cement and Concrete Research, vol. 41, no. 4, pp. 439–442, 2011.

12. Y. Senhadji, M. Mouli, H. Khelafi, and A. S. Benosman, “Sulfate attack of Alge-rian cement-based material with crushed limestone filler cured at different temperatures,” Turkish Journal of Engineering and Environmental Scienc-

es, vol. 34, no. 2, pp. 131–143, 2010. w

CEMENT: UFNSP

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Manufactured Sand

River sand is a widely used construction material all over the world, especially in the production of concrete, cement-sand mortar and concrete blocks. Various Government, Non

Governmental Organisations and Research Institutes are striv-ing to identify alternative materials to supplement river sand. There is a strong need for research on river sand substitutes for concrete production and cement sand mortar production. The research should aim to identify suitable river sand substitutes for practical applications in the local construction industry and also focus on formulating practical solutions for using river sand substitutes. The development of standards / specifications and incorporating in the BIS codes will reduce the pressure on us-ing river sand. The standards and codal specifications will assist to select and use the alternatives by the various stake holders. Quality certification of the alternate aggregates and quality cer-tification of the concrete manufacturing process plays a vital role in ensuring the durability of the concrete.

Researchers are in continuous search for the alternatives to sand. Fine aggregate is one of the important constituents of concrete. River sand is becoming a scarce material. Sand mining from rivers has become objectionably excessive. It has reached a stage where it is killing all our rivers day by day. So sand mining has to be discouraged so as to save the rivers. As natural sand deposits become depleted near some areas of metropolitan growth, the use of alternatives to sands as a replacement fine aggregate in concrete is receiving increased attention. The National Green Tribunal also imposed ban and restrictions on the sand mining.

Some of the Alternatives to River Sand are

- Manufactured Sand- Fly Ash/ Bottom Ash/Pond Ash- Copper Slag - Filtered Sand- Sea Sand, Slag Sand - Crushed Waste Glass- Recycled Aggregate/C&D Waste Aggregate etc..

Manufactured Sand:

Manufactured sand is popularly known by several names such as Crushed sand, Rock sand, Green sand, UltraMod Sand, Robo sand, Poabs sand, Barmac sand, Pozzolan sand etc. IS 383-1970 (Reaffirmed 2007) recognizes manufacture sand as ‘Crushed Stone Sand’.

Crushed stone sand is produced by crushing boulders. Manufactured sand is produced by rock-on-rock or rock-on-metal Vertical Shaft Impactor (VSI) in which the process that

produced alluvial deposits is closely simulated. Particle size reduction and achieving equidimensional shape is critical to get desired properties. If rock is crushed in compression lot of inherent properties exhibited by natural river sand are lost. If proper technique of manufacturing is not adopted aggregates are bound to become flaky and elongated. Improvements to sand by way of washing, grading and blending may have to be done before use at the consumer end. In case of manufactured sand all the processes mentioned above can be done at manu-facturing plant itself and controls are much better in producing quality fine aggregates.

Fine aggregates manufactured sand proposed to be used shall be produced from a Vertical Shaft Impact (VSI) crushers and shall conform to the requirements of Zone-II (in most of the cases) as per IS 383-1970 (Reaffirmed in 2007) and particles fin-er than 75 µm shall not exceed 15 %. Special efforts on the part of M-sand manufacturers (such as washing of sand by water or dry washing by air) is required to restrict particles finer than 75 µm to 15%. The global trend is to utilize dry classification solutions to produce manufactured sand. The dry separation process separates fine and coarse particles. This allows a re-duced percentage of super fines in manufactured sand, thereby meeting specifications and achieving quality products.

M-sand can also be used for making masonry mortar and shall conform to the requirements of IS 2116-1980 (Reaffirmed 1998) - “Specification of sand for Masonry mortars”.

Issues and General Requirements of Manufactured Sand

The Civil engineers, Architects, Builders, and Contractors agree that the river sand, which is available today, is deficient in many respects. It does content very high silt fine particles (as in case of Filter sand).Presence of other impurities such as coal, bones, shells, mica and silt etc makes it inferior for the use in cement concrete. The decay of these materials, due to weathering effect, shortens the life of the concrete.

Now-a-days, the Government have put ban on lifting sand from River bed. Transportation of sand damages the roads. Re-moving sand from river bed impact the environment, as water table goes deeper & ultimately dry.

General Requirements:

1. All the sand particles should have higher crushing strength2. The surface texture of the particles should be smooth3. The edges of the particles should be grounded4. The ratio of fines below 600 microns in sand should not be

less than 30%

Dr. Aswath M UProfessor and Head Department of Civil Engineering, Bangalore Institute of Technology

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5. There should not be any organic impurities6. Silt in sand should not be more than 2%, for crushed sand7. In manufactured sand the permissible limit of fines below

75 microns shall not exceed 15%

Manufactured Sand Quality

Manufactured Sand should adhere to the highest standards and must undergo the following quality tests

1. Sieve analysis2. Optical Microscopic Study to check the particle shape3. Workability (slump test by slump cone method)4. Cube test for compressive strength5. Tests for Silt and clay

The artificial sand produced by proper machines can be a better substitute to river sand. The sand must be of proper gra-dation (it should have particles from 150 microns to 4.75 mm in proper proportion). When fine particles are in proper proportion, the sand will have fewer voids. The cement quantity required will be less. Such sand will be more economical. Demand for manufactured fine aggregates for making concrete is increas-ing day by day as river sand cannot meet the rising demand of construction sector. Natural river sand takes millions of years to form.

Technical Specifications for Sand as Per BIS:

The Indian Standard IS: 383; “Specification for Coarse and Fine Aggregates from Natural Sources for Concrete” covers the requirements for aggregates, crushed or uncrushed, derived from natural sources, such as river terraces and riverbeds, glacial deposits, rocks, boulders and gravels, for use in the production of concrete for normal structural purposes including mass concrete works.

Before choosing any alternative one should check the tech-nical specifications as per the BIS codes. Sand is mainly used for the preparation of mortar and concrete. It is also required to manufacture the building blocks. The standard terminology used

for sand is fine aggregate. We all know that sand is a natural-ly occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand is silica (silicon dioxide, or Si O2), usually in the form of quartz. Fine Aggregate( Sand and/or crushed stone) are less than 4.75 mm in size and F.A. content usually 35% to 45% by mass or volume of total aggregate.

Aggregates shall comply with the requirements of IS 383. As far as possible, preference shall be given to natural aggregates. Other types of aggregates such as slag and crushed over burnt brick or tile, which may be found suitable with regard to strength, durability of concrete and freedom from harmful effects may be used for plain concrete members, but such aggregates should not contain more than 0.5 percent of sulphates as SO, and should not absorb more than 10 percent of their own mass of water.

IS:383 classifies sand in to; Natural Sand - Fine aggregate resulting from the natural disintegration of rock and which has been deposited by streams or glacial agencies, Crushed Stone Sand - Fine aggregate produced by crushing hard stone; and Crushed Gravel Sand - Fine aggregate produced by crushing natural gravel.

Quality of Aggregates

Aggregates shall consist of naturally occurring (crushed or uncrushed) stones, gravel and sand or combination thereof. They shall be hard, strong, dense, durable, clear and free from veins and adherent coating; and free from injurious amounts of disin-tegrated pieces, alkali, vegetable matter and other deleterious substances. As far as possible, flaky, scoriaceous and elongat-ed pieces should be avoided.

Deleterious Materials -Aggregates shall not contain any harmful material such as pyrites, coal, lignite, mica, shale or similar laminated material, clay, alkali, soft fragments, sea shells and organic impurities in such quantity as to affect the strength or durability of the concrete.

Aggregates to be used for reinforced concrete shall not contain any material liable to attack the steel reinforcement.

Sl. No. Deleterious Substance Method of Test Fine Aggregate Percentage by Weight, Max

Coarse Aggregate Percentage by Weight, Max

Uncrushed Crushed Uncrushed Crushed

1 2 3 4 5 6 7

i Coal and Lignite IS: 2386 (Part II)-1963 1.00 1.00 1.00 1.00

ii Clay lumps IS: 2386 (Part II)-1963 1.00 1.00 1.00 1.00

iii Materials finer than 75-µ IS Sieve IS: 2386 (Part I)-1963 3.00 15.00 3.00 3.00

iv Soft fragments IS: 2386 (Part II)-1963 - - 3.00 -

v Shale IS: 2386 (Part II)-1963 1.00 - - -

vi

Total of percentages of all deleterious materials

(Except mica) including Sl. No. (i) to (v) for Col 4,6,7 and Sl. No. (i) and (ii) for

Col 5 only.

- 5.00 2.00 5.00 5.00

Table1: Limits of Deleterious Materials, IS:383-1970 Reaffirmed 2007 Clause 3.2.1[Note: Aggregates petrographically similar to known reactive types or aggregates which, on the basis of service history or laboratory experiments, are suspect-ed to have reactive tendency should be avoided or used only with cements of low alkalies {not more than 0.6 percent as sodium oxide (Na2O )} after detailed laboratory studies. use of pozzolanic cement and certain pozzolanic admixtures may be helpful in controlling alkali aggregate reaction.]

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Aggregates which are chemically reactive with alkalies of ce-ment are harmful as cracking of concrete may take place.

Limits of Deleterious Materials: The maximum quantity of deleterious materials shall not exceed the limits specified in Ta-ble 1 when tested in accordance with IS: 2386-1963. However, the engineer-in-charge at his discretion may relax some of the limits as a result of-some further tests and evidence of satisfac-tory performance of the aggregates.

Aggregate Crushing Value: The aggregate crushing value, when determined in accordance with IS: 2386 (Part IV)-1963 shall not exceed 45 percent for aggregate used for concrete other than for wearing surfaces, and 30 percent for concrete for wearing surfaces, such as runways, roads and pavements.

Aggregates Impact Value: As an alternative, the aggregate impact value may be determined in accordance with the meth-od specified in IS: 2386 (Part IV)-1963. The aggregate impact value shall not exceed 45 percent by weight for aggregates used for concrete other than for wearing surfaces and 30 percent by weight for concrete for wearing surfaces, such as runways, roads and pavements.

Aggregate Abrasion Value: Unless otherwise agreed to be-tween the purchaser and the supplier, the abrasion value of ag-gregates, when tested in accordance with the method specified in IS: 2386 (Part IV)-1963 using Los Angeles machine, shall not exceed the following values:

a) For aggregates to be used in concrete for wearing surfaces: 30 percent

b) For aggregates to be used in other concrete: 50 percent

Soundness of Aggregate: For concrete liable to be exposed, the action of frost, coarse and fine aggregates shall pass a sodium or magnesium sulphate accelerated soundness test specified in IS: 2386 (Part V)-1963, the limits being set by agreement be-tween the purchaser and the supplier, except that aggregates failing in the accelerated soundness test may be used if they pass a specified freezing and thawing test satisfactory to the user. [Note: - As a general guide, it may be taken that the average loss of weight after 5 cycles shall not exceed the following:

a) For fine aggregate: 10 percent when tested with sodium sulphate (Na2 SO4), and 15 percent when tested with mag-nesium sulphate (Mg SO4)

b) For coarse aggregate 12 percent when tested with sodium sulphate (Na2 SO4), and 18 percent when tested with mag-nesium sulphate (Mg SO4)NOTE 1 -The presence of mica in the fine aggregate has

been found to reduce considerably the durability and compres-sive strength of concrete and further investigations are underway to determine the extent of the deleterious effect of mica. It is ad-visable, therefore, to investigate the mica content of fine aggre-gate and make suitable allowances for the possible reduction in the strength of concrete or mortar.

NOTE 2- The aggregate shall not contain harmful organic impurities [tested in accordance with IS: 2386 (Part II) - I963] in sufficient quantities to affect adversely the strength or durabil-ity of concrete. A fine aggregate which fails in the test organic impurities may be used, provided that, when tested for the effect of organic impurities on the strength of mortar, the relative strength at 7 and 28 days, reported accordance with 7 of IS : 2386 (Part VI )-1963 is not less than 95 percent.

Size and Grading of Aggregates

IS 383 defines Fine Aggregates as aggregate most of which passes 4.75-mm IS Sieve and contains only so much coarser material as permitted in cl.4.3. [Cl. 4.3 Fine Aggregates -The grading of fine aggregates, when determined as described in IS: 2386 (Part I)-1963 shall be within the limits given in Table 4 and shall be described as fine aggregates, Grading Zones I, II, III and IV. Where the grading falls outside the limits of any particular grading zone of sieves other than 600-micron IS Sieve by a total amount not exceeding 5 percent, it shall be regarded as falling within that grading zone. This tolerance shall not be applied to percentage passing the 600-micron IS Sieve or to percentage passing any other sieve size on the coarse limit of Grading Zone I or the finer limit of Grading Zone IV.]

NOTE 1-For crushed stone sands, the permissible limit on 150-micron IS Sieve is increased to 20 percent. This does not affect the 5 percent allowance permitted in 4.3 applying to other sieve sizes.

Is SieveDesignation Percentage Passing for

Grading Zone 1

Grading Zone II

Grading Zone III

GradingZone IV

10 mm 100 100 100 100

4.75mm 90-100 90-100 90-100 95-100

2.36 mm 60-95 75-100 85-100 95-100

1.18mm 30-70 55-90 75-100 90-100

600 micron 15-34 35-59 60-79 80-100

300 micron 5-20 8-30 12-40 15-50

150 micron 0-10 0-10 0-10 0-15

Table 4: Fine Aggregates, IS:383-1970 Reaffirmed 1997 Clause 4.3)

NOTE 2 - Fine aggregate complying with the requirements of any grading zone in this table is suitable for concrete but the quality of concrete produced will depend upon a number of fac-tors including proportions.

NOTE 3 - Where concrete of high strength and good dura-bility is required, fine aggregate conforming to any one of the four grading zones may be used, but the concrete mix should be properly designed. As the fine aggregate grading becomes progressively finer, that is, from Grading Zones I to IV, the ratio of fine aggregate to coarse aggregate should be progressively reduced. The most suitable fine to coarse ratio to be used for any particular mix will, however, depend upon the actual grading, particle shape and surface texture of both fine and coarse ag-gregates.

NOTE 4- It is recommended that fine aggregate conforming to Grading Zone IV should not be used in reinforced concrete unless tests have been made to ascertain the suitability of pro-posed mix proportions.

The percentage passing 600μm sieve will decide the zone of the sand: Zone-I Coarse Sand; Zone-II; Zone-III and Zone-IV Fine Sand. Grading Limits can also be represented through a graph of sieve size on the x-axis and % passing on the Y-axis (Semi log sheet).

Fineness Modulus (FM): The result of aggregate sieve anal-ysis is expressed by a number called Fineness Modulus. It is

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obtained by adding the sum of the cumulative percentages by mass of a sample aggregate retained on each of a specified se-ries of sieves and dividing the sum by 100. The specified sieves are: 150 μm (No. 100), 300 μm (No. 50), 600 μm (No. 30), 1.18 mm (No. 16), 2.36 mm (No. 8), 4.75 mm (No. 4), 9.5 mm , 19.0 mm , 37.5 mm , 75 m , and 150 mm.

Fineness modulus = 283 ÷ 100 = 2.83

Is SieveDesignation Percentage Passing by Weight Grading

Zone-I (Coarse Sand)

Zone II Most Suitable/ Desirable

Zone-IIIZone-IV

(Fine Sand)

10 mm 100 100 100 100

4.75mm 90-100 90-100 90-100 95-100

2.36 mm 60-95 75-100 85-100 95-100

1.18mm 30-70 55-90 75-90 90-100

600µm 15-34 35-59 60-79 80-100

300µm 5-20 8-30 12-40 15-50

150µm 0-10 0-10 0-10 0-15

Fineness Modulus 4.0-2.71 3.37-2.10 2.78-

1.712.25-1.35

Table 6: Particle Shape, IS:383-1970 Reaffirmed 1997 Clause C-3.2

Figure1: Particle Shape:rounded

Fig.3 Particle Shape:Angular Fig.4 Particle Shape:flaky

Figure 2: Particle Shape:irregular

Fine-Aggregate Grading Limits

Significance of Grading

Classification Description Illustration Of Characteristic Specimens Example

1 2 3 4

Rounded Fully water worn or com-pletely shaped by attrition Fig. 1

River or seashore gravels; desert, seashore and wind-

blown sands

Irregularly or partly roundedNaturally irregular, or partly shaped by attrition, and hav-

ing round edgesFig. 2 Pit sands and gravels; land or

dug flints; cuboid rock

Angular

Possessing well- defined edges formed at the in-

ter-section of roughly planar faces

Fig. 3 Crushed rocks of all types; tullus; screes

Flaky

Material, usually angular, of which the thickness is small

relatively to width and/or length

Fig. 4 Laminated rocks

MANUFACTURED SAND

FM is an index of fineness of an aggregate. The fineness modulus of the fine aggregate is required for mix design since sand gradation has the largest effect on workability. Fine sand (low FM) has much higher effect paste requirements for good workability. It is computed by adding the cumulative percentages of aggregate retained on each of the specified series of sieves, and dividing the sum by 100 [smallest size sieve: No. 100 (150 μm)]. The higher the FM, the coarser is the aggregate.

Sampling and Testing

Sampling: The method of sampling shall be in accordance with IS: 2430-1969. The amount of material required for each test shall be as specified in the relevant method of test given in IS: 2386 (Part I)-1963 to IS: 2386 (Part VIII)-1963.

Testing: All tests shall be carried out as described in IS: 2386 (Part I)-1963 to IS: 2386 (Part VIII)-1963. Unless otherwise stated in the enquiry or order, duplicate tests shall be made in all cases and the results of both tests reported.

Information to be furnished by the Supplier:

Details of Information: When requested by the purchaser or his representative, the supplier shall provide the following particulars:

a) Source of supply, that is, precise location of source from where the materials were obtained

b) Trade group of principal rock type present c) Physical characteristics d) Presence of reactive mineralse) Service history, if any. Subject to prior agreement, the sup-

plier shall furnish such of the following additional informa-tion, when required by the purchaser:

f) Specific gravity, g) Bulk density, h) Moisture contenti) Absorption value j) Aggregate crushing value or aggregate impact valuek) Abrasion value, l) Flakiness-index, m) Elongation-index, n) 3 Presence of del-

eterious materialso) k) Potential reactivity of aggregatep) m) Soundness of aggregate

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Greater Durability

Manufactured sand has balanced physical and chemical properties that can withstand any aggressive environmental and climatic conditions as it has enhanced durability, greater strength and overall economy. Usage of manufactured sand can overcome the defects occurring in concrete such as honey combing, segregation, voids, capillary etc.

High Strength

The superior shape, proper gradation of fines, smooth surface texture and consistency in production parameter of

chemically stable sands provides greater durability and higher strength to concrete by overcoming deficiencies like segrega-tion, bleeding, honey combing, voids and capillary.

Greater Workability

The crusher dust is flaky and angular in shape which is trouble some in working. There is no plasticity in the mortar which makes it even difficult for the mason to work, whereas the cubical shape with grounded edge and superior gradation gives good plasticity to mortar providing excellent workability.

Offsets Construction Defects

Manufactured sand has optimum initial and final setting time as well as excellent fineness which will help to overcome the deficiencies of concrete such as segregation, bleeding, honey-combing, voids and capillary.

Economy

Usage of manufactured sand can drastically reduce the cost since like river sand, it does not contain impurities and wastage is NIL. In International Construction Scenario, no river sand is used at all, only sand is manufactured and used, which gives superior strength and its cubical shape ensures signifi-cant reduction in the cement used in the concrete

Eco-Friendly

Manufactured sand is the only alternative to river sand. Dredging of river beds to get river sand will lead to environmen-tal disaster like ground water depletion, water scarcity, threat to the safety of bridges, dams etc.

Beside with the Government contemplating ban on dredg-ing of River beds to quarry river sand, as part of the growing concern for environment protection, manufacturing sand will be the only available option.

Conclusion

Keeping the demand in mind and all the technical specifi-cations mentioned above, we need to use Manufactured Sand in all construction works. Many manufacturers are producing quality M Sand using latest technologies ensuring the quality

Sieve size

Percentage of individual frac-tion retained,

by mass

Percentage passing, by

mass

Cumulative Percentage retained by

mass

10 mm4.75 mm2.36 mm1.18 mm600 µm300 µm150 µm

PanTotal

0213202024183

100

100988565452130

021535557997-

283

Results of Sieve Analysis and calculation of FM of Sand

Fine Aggregate for Concrete: FM Range 2.3 to 3.1

Comparison And Advantages: (Source: Poabs M Sand & Besto)

Comparison between Manufactured Sand and Crusher Dust

Manufactured Sand Crusher Dust

ColourParticle Shape

ProductManufacturing

Process

GreyCubically Shaped

Manufactured as per IS, BS, ASTM Standards

International technology con-trolled manufacturing process

through imported machines

GreyFlaky

Elongated (Shapeless)a) It is fractured dust of jaw crusher

b) A waste product in production process of stone crusherNo controlled manufacturing process as it is the

by-product of stone crusher

Gradation As per IS 383 - 1970 Zone-II Does not adhere to IS 383 - 1970 or any other standards

Suitability for concreting

Recommended for usage in con-crete & masonry works worldwide

by the concrete technologists.Confirms international standards

Not recommended for use in concrete or masonry works. Does not have quality.

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as per BIS specifications at affordable costs compared to river sand. As natural sand deposits become depleted, the use of al-ternatives to sand as a replacement for fine aggregate such as Manufactured Sand is receiving increased attention.

Acknowledgement: The content of the paper is sourced from various organisations for knowledge dissemination. All logos and images are property of the respective owners listed in the references

References

1. Elavenil, S., Nagabhushana Rao, Bh., Radhakrishnan, R and Hariharan, K (2005)“Comparative Study of Steel and Polypropylene Fibre Concrete Plates for Bridges and Roads”, Journal of Current Science, Vol.7, No.1, pp. 19-24

2. Elavenil.S,Saravanan.S,Akarsh.M.R,(2012)‘Studies on Plastic mixed concrete with Conventional concrete’,i-managers Journal on Structural Engineer-ing,Vol.1,N0.2,pp- 11-17

3. Guide to the specification and use of manufactured sand in concrete CCAA – T60 (Cement Concrete and Aggregates AUSTRLIA).

4. Guide to the specification and use of manufactured sand in concrete CCAA – T60 (Cement Concrete and Aggregates AUSTRLIA).

5. Hudson BP – (Manufactured sand for concrete).

6. Hudson BP – (Manufactured sand for concrete).

7. ICOMAT Report

Courtesy:Besto

8. IS: 383-1970, [Reaffirmed 1997], Specification for coarse and fine aggregates from natural sources for concrete, Bureau of Indian Standards, New Delhi.

9. Nichols, F.P (Manufactured sand and crushed sand in Portland cement concrete INTERNATIONAL, NO. 8, PP 56-63, 1982).

10. POBAS MSAND-http://www.msand.in/poabsmsand.php11. Reference manual for field engineers on building construction, Task Force for

Quality Assurance in Public Constructions, Govt. of Karnataka12. Research on River Sand Substitutes for Concrete Production and Cement Sand

Mortar Production by Professor Albert K.H. Kwan, Department of Civil Engineer-ing, The University of Hong Kong

13. Sand matter the sand saga… an overview of sand scenario- Built Expressions Vol:2 Issue:9 September 2013

14. Singapore’s sand shortage “The hourglass effect”- Oct 8th 2009 | SINGAPORE 15. Technical data and potential use of fly ash, bottom ash and pond ash of APNRL

Plant 201216. Use of Manufactured Sand in Concrete and Construction an Alternate to River

Sand by G. Sreenivasa, General Manager (Business Development), UltraTech Ce-ment Limited, Bangalore

17. VTU e-learning Notes for UNIT-II (Aggregates used for concrete making)18. RoboSand The perfect substitute for river sand-http://www.robo.co.in/home.htm19. www.robosilicon.com 20. www.vsicrushers.com 21. http://en.wikipedia.org/wiki/Sand22. http://www.artificialsand.com/faqs.html23. http://www.msand.in/ 24. http://www.msand.in/25. http://www.oregrinder.com/ w

Sieve Analysis River Sand Vs M-Sand

Is Sieve River Sand % Age Passing M-Sand % Age Passing % Age passing for single sized aggregates of Normal Sand (IS 383 - 1970) Zone II

4.75 mm 99.25 99.75 90 to 100

2.36 mm 93.50 78.25 75 to 100

1.18 mm 48.00 52.00 55 to 90

600 Microns 21.00 38.00 35 to 59

300 Microns 04.00 21.00 08 to 30

150 Microns 0.05 5.00 0 to 10

Comparison of Impurities - River Sand Vs M-Sand

River Sand M-Sand

Marine Products 2 - 4 % Nil

Oversized Materials 6 - 10 % Nil

Clay & Silt 5 - 20 % Nil

Natural Sand Manufactured Sand

- Excessive and illegal quarrying of Natural sand at river beds , resulting into soil erosion and danger to the reservoir structures

- Scarcity due to ban on quarrying activities near the river bed by the Govt. to prevent depleting of natural resource

- No control on silt content - Very long distance transportation resulting into vol-

ume loss on the quantity of sand received at site. - Adulteration with filter sand (Unfit to be used in con-

crete) - No guarantee on gradation - Huge inventory cost during monsoon for non avail-

ability - Fear of not getting sand, if rejected for quality - Additional manpower for removal of pebbles & boul-

ders while loading into batching plant to avoid pump choke ups

- No mechanism on pricing

- 100% replacement to Natural sand & It is One of the bi-product of aggregates

- No scarcity , as the Govt. is encouraging the business to garner un-tapped revenue

- Govt. has identified the places and accorded the sanction for carrying out quarrying and crushing activities without compromising on any environmental issues

- Sand washing machine to ensure 0% silt content, benefiting best economized concrete with possibilities of reduction in cement content.

- Uninterrupted supply even during rainy season, which in turn facili-tating timely completion of the project.

- No adulteration - World class Machine is employed to get the Top-Quality-Graded ag-

gregates meeting both BIS and Customer requirement, the Consis-tency on the required gradation is guaranteed.

- No fear, the quality is the main focus.- No additional manpower is required to remove boulders or pebbles,

which is again cost saving - Transparency in pricing , as the manufacturing facility is legal and

ethical

MANUFACTURED SAND

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Creating Durable Concrete with Admixtures

As we move into an uncertain future wrought with en-vironmental concerns and the call to build more re-sponsibly not because it is good to do, but more be-

cause it is a must. In order to do so we must build wisely. This is especially true in countries like India that are looking at a growth and development spurt. With the government opening up the floodgates for foreign investment and work-ing closely with international firms to set up manufacturing hubs in India, the country is realizing the need for responsi-ble and durable construction.

Concrete is the most used man-made material in the world, used twice as much as all other materials combine, including steel, wood, and aluminum. Taking a look at our major cities and the buildings and infrastructure that en-compasses them you will see just how much concrete is used. In fact, according to a 2007 United States Geological Survey, ‘Minerals Commodity Summary – Cement’, over 3,000 kg’s of concrete is used annually for each man, woman, and child on the planet. In India alone the cement industry grew by 12% in 2014 and is expected to grow 8% until 2016, to under-stand the extent of concrete consumption in India and the subcontinent alone.

Ensuring the environmental and sustainable factors are accounted for is vital to the preservation of our societies and for future generations. To do so, we must use innovative ma-terials that can stand up to the rigors of Mother Nature, whilst also limiting the harm to the environment. In countries with vast and dynamic environmental and population differences, these materials can make a sea of change in living conditions.

For concrete, the best and most efficient method in en-suring this is to create sustainable structures by using the most durable concrete possible. In most cases, the reason behind concrete deterioration is the ingress of water. Water breaks into the concrete moisture through cracks and pores, infiltrating the matrix and effectively limiting the durability of the structure. When concrete durability is compromised, the sustainability and resilience of the structure is also

Concrete Durability

The reason concrete is used so readily is that no other building material can match it in terms of effectiveness, price, and performance for most purposes. Furthermore, concrete can be durable, is rather easy to ‘install’, but first and fore-most, it limits the negative environmental effects further

than other major building materials. Concrete is also easy to procure, as in its simplest form is made of three main in-gredients: water, Portland cement and aggregates. Water is all-around us, coarse and fine aggregate can be found in numerous locations and cement is easy to come by as well.

Concrete is also known as a durable material; meaning its qualities can resist whether action, chemical attack while maintaining its desired engineering properties. However, as evidenced by deteriorating buildings across the world and repairs becoming common practice, concrete structures are not living up to their desired lifespans, which is to say; our structures are not durable enough.

Concrete can deteriorate under certain circumstances, such as:

- Chloride attack/Corrosion of steel reinforcement;- Sulfate attack;- Alkali Aggregate Reaction (AAR); and- Freeze/thaw cycles.

However, without question the greatest cause of con-crete deterioration is the ingress of water and water borne chemicals. Water, one of the essential components of a con-crete mix design is the biggest issue facing the durability of concrete today.

Concrete Admixtures

Methods to protect concrete from water without surface applied barriers have been evolving for several decades. To-

Anandita Kakkar DGM, Marketing & Advertising, Kryton Buildmat Co. Pvt. Ltd.

PRAs are chemical admixtures used to protect concrete from the damaging effects of water and water borne chemicals.

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day, there are several approaches to designing and installing durable, water resistant concrete, such as proper mix pro-portioning; minimizing the water-cement ratio; ensuring the concrete is well consolidated, and employing good wet cur-ing practices to maximize the concrete’s properties, as well as using concrete admixtures.

Additionally, Supplementary Cementitious Materials (SCMs) such as fly ash, ground granulated blast furnace slag and silica fume have become common for the range of ben-efits those materials provide.

Permeability Reducing Admixtures

Increasingly, Permeability Reducing Admixtures (PRAs) are being used to provide an additional level of protection from within. PRAs are chemical admixtures used to protect con-crete from the damaging effects of water and water borne chemicals. These particular kinds of admixtures are distinct tools for making durable concrete, and compliment rather than replace other tools such as the previously mentioned SCMs.

With proper selection and use, PRAs (Often referred to as “integral systems”) have been used to replace surface applied sealers, water repellents and membranes. They provide in-tegral protection against water and chemicals throughout the full depth of a concrete element, and can eliminate the labor needed to apply surface protective systems.

Further to these advantages, PRAs are not vulnerable to surface damage, and the installation of these integral sys-tems is less affected by environmental factors (particularly rain). Altogether, these advantages bring a concrete structure the best of both worlds: Being cost efficient and saving time during construction; and providing quality, lasting support against water damage to enhance the entire structures du-rability.

PRAN/PRAH

The selection of an appropriate PRA depends on the service conditions, and how water is expected to enter the concrete. A document from The American Concrete Insti-tute (ACI), ACI 212.3R-10 Report on Chemical Admixtures for Concrete, subdivides PRAs into two categories based their performance properties:

- PRAN (Permeability Reducing Admixture for Non-Hy-drostatic Conditions) admixtures are intended for appli-cations that are not subject to hydrostatic water pressure and are sometimes called damp roofing admixtures. Most PRAN’s contain water repellant chemicals that shed wa-ter and reduce water absorption into the concrete.

- PRAH (Permeability Reducing Admixture for Hydrostat-ic Conditions) are primarily intended for use in concrete that is exposed to water under pressure and are some-times called waterproofing admixtures. They are able to withstand the high hydrostatic pressure for applications such as basements, tunnels and water containment structures. A comprehensive educational document has been re-

cently published by ACI. ACI’s Educational Bulletin, E4-12 – Chemical Admixtures, describes the basic types and uses of these admixtures, and works as a valuable introduction to this complex topic. E4-12 is a free resource and can be found on ACI’s website www.concrete.org. (Source: E4-12 Chemi-cal Admixtures for Concrete)

Conclusion

Resilient and durable structures are a result of effec-tive construction practices, efficient minds and innovative product technology. Moreover, it requires finding solutions to problems faced in the construction industry. The world is moving away from traditional and sometimes ineffective methodologies and accepting thoroughly tested and proven technologies that have a track record of success.

PRAH, crystalline technology is one example. This ad-mixture drastically reduces the ingress of water by using the concrete itself as a water barrier, thereby increasing the du-rability of the completed structure. It’s easy to apply, saves on time and money and also has no negative impact on the environment, while providing quality, lasting support against water damage to enhance a structures durability. wSame as above – side by side

The ICW admixture starts crystallization and develops its needle like crystals in concrete as defense against water damage.

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Development of Retrofit Scheme for Deficient Post Tensioned Flat Slab by Using Post Tensioned Carbon Laminates for Large Commercial Premises

Abstract: Post tension flat slab construc-tion is very popular to cover large areas with economy and speed, especially for commercial type of buildings like IT Parks. Even though post tension slab is popular system if proper quality is not maintained during execution it may lead to major structural stability issue. This case study presents one such typical ex-ample attributed to poor workmanship at site and bad quality control at site. When this particular building was given for long term lease, just before fit out large de-flections were observed in slab panels. On closer look and after cleaning through cracks were observed from top around the column capital. Prime reason for this was the bad quality at site and wrong profile placement of post tension tendons inside the slab. Because of this slab was behaving like a regular RCC flat slab, leading to excessive sagging and cracks on top. Sanrachana Structural Strength-ening Pvt. Ltd. (SSSPL) team was roped in to provide most efficient solution in terms of both time and cost as structure was to be handed over to tenants. After weigh-ing all the available options it was decided to make use of high strength pre-cured carbon fiber reinforced polymer (CFRP) laminate system with anchor plate by us-ing both post tensioned and non-postten-sioned CFRP Laminates. The material systems was provided by Specialty Rein-forced Polymer Composite Pvt. Ltd. After successful completion of the work, full scale load test conforming to IS 456 was conducted at site before handover. The load testing was carried out by Vijna Con-

sulting Engineers Pvt. Ltd. The structural performance of the particular strength-ened structure was satisfactory under the actual load test and it successfully met all the structural requirements with gener-ous safety margin. Over 1.00 lac sq.ft of area was successfully retrofitted by using 12000 RMT (12KM) CFRP laminates in 30 days. The paper presents the evolution of the structural strengthening system, its application at site and details of load test conducted. Pre-cured Carbon fiber laminate have emerged as very efficient construction material systems, especial-ly in the field of structural strengthening/retrofitting of existing structures. While there are many reasons why structures need strengthening/retrofitting, change in use, poor workmanship at site, errors during design or subsequent increase in imposed load demand is one of the ma-jor reasons for structural strengthening/retrofitting.

Introduction

Number of new building structures are deficient because of poor workman-ship at site, bad quality or because of er-ror in the design. This paper present one such case study.

Post tension flat slab construction is very popular to cover large areas with economy and speed, especially for com-mercial type of buildings like IT Parks. Even though post tension slab is popular system if proper quality is not maintained during execution it may lead to major structural stability issue. When this par-ticular building was given for long term

lease, just before fit out large deflections were observed in slab panels. On closer look and after cleaning through cracks were observed from top around the col-umn capital. Prime reason for this was the bad quality at site and wrong profile placement of post tension tendons inside the slab. Because of this slab was behav-ing like a regular RCC flat slab, leading to excessive sagging and cracks on top. It was observe that major cracks are at top of the slab along the periphery of the column capital and also the same cracks are propagating between columns in lon-gitudinal as well as in transfer direction. It was also observe that there is a per-manent sag in the slab which is around 40mm (minimum) to 120mm (Maximum). This was the alarming signal to the client.

This type of cracks were observed over on 2 floors having area of around 50000.00 sq.ft each. So it was decided to retrofit total area of 1 lac sq.ft. As the property was to be given on lease and fit out period was of 60 days, the biggest challenge was to complete the project in 30 days and handed over to client. This would avoid loss of revenue to the client.

Different options for retrofitting like addition of structural steel, span short-ening and stiffening were considered. However, it would have reduced the head room in addition to adding extra dead load on already weak structure and time required for completion was very high. Considering these limitation of traditional system it was decided to use CFRP Lami-nates for structural retrofitting by passive as well as active systems. CFRP systems

Dr. Mangesh Joshi1, Sagar Patil2, Manish Yadav3

1CEO2Structural Design Engineer3Project In-charge(Execution)1,2,3Sanrachana Structural Strengthening Pvt. Ltd.(SSSPL), Thane, India

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are light weight, its profiles are thin so there is no loss of head room and its ap-plication is fast. Use of CFRP is now well establish in various field in construction it

plication of CFRP laminates all crackes were opened with V-Cut and are grouted with low viscosity monomer by gravity pouring at many locations grout could be seen dropping from bottopm of the slab. After this slab was supported from bottom to release the load partially and in that state laminate application was done. The pannels where excessive deflection was there were strengthened usning post-tenstioned laminate sysytem and balance with regular anchoring.

The strengthening system was de-signed in reference to ACI 440.2R-08. Pre-cured CFRP laminates being pro-duced in the factory under stringent qual-ity norms, consistent and relatively higher mechanical properties are ensured. Ends were fixed in position by MS plate to avoid peeling.

Defficient Top Reinforcement / Steel

As per input data provided by client, a model is prepared on FEM based soft-ware.

Input Data

Grade of slab= M35 N/mm2

Grade of Steel = Fe 415 N/mm2

Depth of slab = 230 mmLoad considerations on the slabSelf-weight of Slab = 5.75 KN/m2

Floor Finish = 2KN/m2

Imposed Load = 5KN/m2

Figure 1: Use of composite in con-struction

Figure 2: (a)-Initial condition

Figure 2: (b)-Initial condition3d Model

Slab Bending Moment At Column Drop In X Di-rection

Deformed Shape

can be used by different methods as de-scribed in figure 1

Initail Condition of Slab

As discussed above post tensioning cable placement was wrong so although slab was designed as Post tensioned slab it was behaving as regular RCC flat slab. And in absense of lesser top reinforce-ment cracking was obsered around the column capital and parallel to column strip. This is can be more clearly seen in Figure 2 a and 2b.

Rerofitting Approch

First slab was analysed by using FEM based sofwares for its designed load and to find the forces on section. It was found that if we don’t consider contribution of post tension forces there was defficien-cy of top steel. The same diffiecincy was compensated by applying CFRP lami-nates at deisgned spacing and loaction the details of the same are given in fol-lowing section and figures. Prior to ap-

Slab Bending Moment At Column Drop In Y Di-rectionFigure 3: FEA Analysis of flat slab

Slab bending moment contourat column drop in x direction

Slab bending moment contour at column drop in y directionFigure 4: FEA analysis results and proposed loca-tion of CFRP Laminates

Figure 5: Strengthening with cfrp plate at deficient area

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FEM Analysis Results and Proposd

Strengthening Scheme

Actual Site Photograph of Execution

Material Specification used in Project STR Strong Lam 100X1.4

Tensile Strength: 2800 MPaTensile Modulus: 165 GpaElongation: 1.7 %Width 100mmThickness 1.4 mm

Full Scale Load Testing

Upon completion of the strengthen-ing work, as per the project specifications, full scale load test was carried as per the details below-

Objective of the Test

The objective of the load test was to verify the structural performance of ret-rofitted slab, which was strengthened us-ing pre-cured carbon laminate strength-ening system as per the approved design. Thus, with the load test, the structural performance of the strengthened slab was thoroughly verified as per Clause No. 17.6 of IS:456 2000.

Test Parameters

The test parameters were set as per the input data received from consultants as follows:

Design imposed load of 500 kg/m2.Note: Since the displacements to be

measured in the proposed load tests, the test conformed to limit state of service-ability. The imposed test load considered as per IS456 clause 17.6 as follows.

Dead Load + 1.25 times imposed load Therefore actual imposed test load = 200+ (1.25 x 500) = 825 kg/m2.

Test Specimen

Load test was carried out on the strengthened slab panel of typical 10.8 m wide x 10.8 m long patch, which was mu-tually selected by the consultants as per the test arrangement described herewith.

To apply design imposed load a water tank was constructed with brick block. The height of water level is fill upto 825mm (0.825m) to get the imposed load of 825Kg/m2

Test Equipments

The test facility consists of the following:Test specimen 10.8 m wide x 10.8 m

long patch of slab clearly demarcated.And specially devised data acquisition

system- TC-1600 FD in order remotely acquire the test reading with the help of 6 numbers of LSC 100 mm range linear displacement sensors.

Test Schedule

Following are the steps to be followed for load testing.

1. Initially a tank had been made with brick block so that water can be stored over the selected slab panel and a measuring scale was fixed at center of the slab as shown in fig. no.

2. Load increment will be 25%, 50%, 75% and 100% of the calculated im-posed load.

3. First a water level is fill till 150mm

Figure 6: Floor plate showing location of laminates

Monopol Leakage through Slab

Surface Preparation

Primer Application

Laminate Fixing

Fixing of MS Plate

Crack along The Periphery of Column Cap

Crack after Opening

Grout Leaked through Slab

Crack filling with Monomer (By Gravity

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and reading was recorded4. Water level is filled till 400mm and

reading was recorded5. Water level is filled till 600mm and

reading was recorded6. And at last water level is filled till

825mm and reading was recorded.

Experimental Setup

in 24 hours of removal of the imposed load, much more than 75% of the re-covery observed in the structure as described in the graphs presented above.

- As per the Indian standard IS456: clause 17.6.3.1 If the maximum de-flection in mm, shown during 24hr under load is less than 40l2/D, where is the effective span in m and D the overall depth of the section in mm, it is not necessary for the recovery to be measured and the recovery provi-sions of clause 17.6.3 shall not apply. In the load test, the recovery of the structure took place with the gener-ous margin as mentioned above. The maximum deflection observed in the slab panel = 22.1 mm, The test slab was subjected to a load equal to full dead load of it plus 1.25 times the imposed load for a period of 24 hours and then the imposed load were re-moved. It was found that the maxi-mum deflection during 24 hour load period is 22.1 mm which is greater than the limit value of 40l2/D i.e. 20.28 mm. The recovery observed in the load test is 75% after unloading.Thus, the strengthened structure

suitably met the IS code requirements as per clause 17.6.3 of IS 456:2000.

Concluding Remark:

Over 1.00 lac sq.ft of area was suc-cessfully retrofitted by using 12000 RMT (12KM) CFRP laminates in 30 days. Pre-cured Carbon fiber laminate have emerged as very efficient construction material systems, especially in the field

of structural strengthening/retrofitting of existing structures.

Acknowledgements:

Specialized Retrofit Designer & Con-tractor –Sanrachana Structural Strengt-neing Pvt. Ltd.

Material Supplier- Specialty Rein-forced Matrix Pvt. Ltd.

Load Testing Agency- Vijna Consult-ing Engineers Pvt. Ltd.

Third Party Consultant- IIT Bombay

References

1. KATSUMATA, H., KOBAYASHI, K., MORITA, S. and MATSUZA, Y. Japanese state of the art on seismic retrofit by fibre wrapping for building structures: Technologies and research development activities, Fourth in-ternational symposium on fibre reinforced polymer reinforcement for reinforced con-crete structures, ACI International, SP 188-74, 1999, pp. 865-878.

2. MANCARTI, G. D. Strengthening of Califor-nia steel bridges by pre-stressing, Trans-portation Research Record No.950, Trans-portation Research Board,1984, 3-187.

3. DUNKER, K. F., KLAIBER, F. W., BECK, B. L. and SANDERS, W. W. Jr. Strengthen-ing of existing single span steel beam and concrete deck bridges, Report No. ISUERI- Ames-85231, Civil Eng, Iowa State Univer-sity, Ames, 1984, pp.102.

4. SWAMY, R. S., JONES, R. and BLOXHAM, J. W. Structural behavior of reinforced con-crete beams strengthened by epoxy bond-ed steel plates, The Structural Engineer, 65A(2), 1987, pp. 59-68.

5. MEIER, U. Carbon fibre-reinforced poly-mers: Modern material in bridge engineer-ing, Structural Engineering International, 1, 1992, pp. 7-11.

6. MUKHERJEE A. Repair and rehabilitation of structures- Strategies with nonmetal-lic fibres. Proceedings of the 1st National workshop on ageing and restoration of structures, IIT Kharagpur, 2001,13, pp. 1-12.

7. GIBSON, R. F. Principles of composite ma-terial mechanics. McGraw Hill Internation-al edition, engineering mechanics series, 1994.

8. Maitra, S. R. -2001 ‘‘Fiber-reinforced poly-mer composites in the rehabilitation and strengthening of reinforced concrete col-umns.’’ M.Tech. thesis, Dept. of Civil Engi-neering, Indian Institute of Technology, Bom-bay, Mumbai, India.

9. Manfredi, G., and Realfonzo, R. - 2001 ‘‘Models of concrete confined by fiber com-posites.’’ Proc., 5th Int. Symp. on Fiber-Re-inforced Polymer Reinforcement for Con-crete Structures (FRPRCS–5), C. Burgoyne, ed., Thomas Telford, London, 865–874w

System Arrangement

Load-deflection curve for Sensor 1

Load-deflection curve for Sensor 2

Sensor Location

Water Level in tank = 825mm

Position of sensor at Site

Structural Performance Test

a) Displacement sensors were placed on the soffit of the slab panel to mea-sure the displacements at predeter-mined locations. Each sensor was checked and initial reading was noted.

b) Load was applied gradually. c) Displacement and residual dis-

placements at the predetermined locations were captured by the data acquisition system and the deflection values were calculated by using in-house software.

d) The test specimen was loaded to 100% design load in specific intervals. Each load interval was maintained for specific time interval.

Results of Load Testing

- In the load test, it was found that with-

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Fiber Reinforced Polymers

Advancements in Inorganic Systems

Fiber Reinforced Polymers (FRP) is an evolving type of ex-ternal reinforcement widely used in the construction industry. FRP systems create a high-strength composite that consists of using high-strength fibers in conjunction with polymer resin to attach the fibers to the applicable surface. There are many different types of FRP systems, depending on the type of fibers and type of polymer resin being utilized.

Carbon fibers are the most commonly used for strengthen-ing concrete structures, typically as a woven fabric, due to their high tensile strength. Additionally glass fibers and basalt fibers can also be used for various FRP applications as well. When evaluating polymers resins they fall into two distinct categories: organic polymers and inorganic polymers. Organic polymers are currently the industry standard for FRP systems, while inor-ganic polymers are moving from the development phase into de-ployment for construction. Inorganic polymers offer some dis-tinct advantages based on their unique properties, including fire resistance, utilization of industrial byproducts, and resistance to UV degradation. The most important advantage that inorganic FRP systems offer, specifically when applied to concrete, is that it will from both a chemical bond in addition to the mechanical bond formed with organic polymers. This dual bonding virtually eliminates the interface between the inorganic FRP and con-crete, creating a permanently reinforced structure.

Fiber Reinforced Polymers can be used for many different applications. This article focuses on three areas: strengthening, crack repair, and confinement.

Strengthening

Concrete is an excellent building material for its versatili-ty and longevity. However just like any building material it will deteriorate over time due to do corrosion, overloading, weath-ering, and external damage. There are essentially two ways to deal with these issues: replace the structural elements that have deteriorated, or repair them to their original strength. Replacing the structural elements is an expensive and time consuming option and depending on the structure may not even be feasible. In these cases Fiber Reinforced Polymer repair is typically the best option for cost effective and rapid repair. Structures that typically need repair over time include bridges and parking decks.

Bridges consist of several important structural elements that wear out over time and lose strength due to various fac-tors, including corrosion, overloading, and vehicular damage. Possibly the most important parts of a bridge are the support beams, which allow for large spans and have to endure through

millions of loading and deflection cycles. These support beams, typically constructed from concrete or steel, must be kept in good condition to ensure the bridge does not fail. The most economical and time efficient way to perform repairs on these beams is to perform FRP repairs. These repairs entail bonding high tensile strength fabric to the face of the beam that expe-riences tension forces. With proper bonding the fabric can in-crease the strength of the beam back to its original condition, preventing bridge failure.

Parking garages are another structure that often needs repair due to exposure to the elements and normal use wear-ing. These structures are almost exclusively made of reinforced concrete or pre-stressed concrete and contain large spans to allow for easy traffic flow. Due to these large spans the concrete experiences relatively large deflection loading that the con-crete must compensate for. Similar to the way FRP is used for beams, FRP can be adhered to the tension side of these con-crete spans to increase their strength. This type of repair can greatly increase the lifespan for a structure, negating the need for costly construction and replacement.

Crack Repair

Cracks occur in concrete structures for many different reasons, including structural cracking due to the corrosion of steel reinforcement, settlement cracks, and cracks caused by structural movement such as earthquakes. When these cracks occur they must be filled to prevent more serious deterioration from occurring due to water intrusion. To fill these cracks the most commonly used repair system is to seal the surface with an epoxy adhesive and then inject the crack with an organic polymer. This repair does a good job of sealing the crack and preventing further deterioration at the crack interface. Howev-er these organic polymers do not “re-join” the concrete from a structural standpoint. This is an application where inorganic polymers can provide superior performance because they not only fill the crack but also create a linked system. Inorganic polymers have a chemistry very similar to that of concrete, so using them as a crack filler essentially fixes the wall back to its original strength and load transfer characteristics. This is es-pecially important for load bearing concrete elements, such as concrete walls.

One of the main causes of cracks to concrete walls are earthquakes. During earthquakes the foundations of concrete structures move rapidly and erratically, putting large strain on the concrete elements. Once these cracks occur in load bearing elements they can have dangerous consequences by compro-mising the structural integrity of the entire structure. By using

Muralee BalaguruPresident, Green NanoFinish LLC

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an inorganic polymer to fill concrete cracks these structural concerns can mitigated by returning the structure to its original load bearing capacity.

Another aspect of crack repair, particularly in cracks that are anticipated to continually move, is adhering a high strength fab-ric over the crack surface. This fabric is used to seal the surface, and even more importantly to “bridge” the crack to prevent further movement. Again this is very important for structur-al elements that have been damaged by earthquakes. These structures that are located in “earthquake zones” will continue to experience aftershocks and foundation movement even after the initial earthquake event. Using a Fiber Reinforced Polymer repair to bridge these cracks will work to prevent these cracks from becoming larger and more damaging to the structural in-tegrity of the concrete.

structure would be extremely difficult if not impossible without replacing the entire structure. FRP confinement is an econom-ical and timely repair method that can be used to enhance load carry capacity as well as increase shear capacity. This is partic-ularly important for structures that are expected to experience earthquake damage. FRP confinement can be used on columns as a seismic retrofit by increasing their loading capacity and ductility for lateral forces to ensure these structures can better withstand an earthquake.

Milled Crack in Concrete (left) that has been Bridged with Inorganic FRP (right)

Before (left) and After (right) Pictures of Concrete Bridge Column Wrapped in Carbon Fabric Impregnated with Inorganic Polymer FRP

Confinement

Confinement is an increasingly used Fiber Reinforced Polymer method and entails wrapping a concrete element in high-strength fabric impregnated with polymer to adhere it to the concrete surface creating a durable shell. Confinement is a useful for both repairing concrete elements, as well as retro-fitting structures for seismic events. Typical concrete elements that have utilized FRP confinement include utility poles, load bearing columns, and concrete piles.

Concrete utility poles used for electrical wires, phone wires, and lights are often damaged due to corrosion, extreme weather events, overloading, and vehicular traffic collisions. Replacing these poles would not only be costly but would also disrupt the services associated with the wires attached to the pole. The best alternative to replacing these poles is to repair them using FRP confinement. For this type of repair high strength fabrics are adhered to the concrete surface using an epoxy resin and are wrapped around the entirety of the pole, either in sections or a continuous loop to form a protective shell. By using FRP confinement the concrete utility pole is protected from further deterioration due to weathering. This is particularly important for concrete poles that have exposed reinforcement rebar with significant corrosion. By wrapping the column fully a water bar-rier is created that will inhibit further corrosion from occurring. Additionally for concrete poles that have experienced significant reinforcement corrosion there may also be loss of structural strength. Using FRP repair can increase the structural strength and return it to its original state.

Fiber Reinforced Polymer column confinement is an ex-cellent way to repair load bearing concrete columns. Replacing a concrete column, whether it is on a bridge, building, or other

Concrete piles tend to experience significant deterioration because of their constant exposure to water. This exposure to water, especially salt water, accelerates the corrosion that the steel reinforcement experiences. When this steel reinforcement corrodes it begins to expand causing the concrete around it to expand laterally, which in turn causes the concrete to crack in tension. Once the concrete cracks the corrosion process accel-erates even more as the reinforcement is fully exposed to the elements. FRP confinement is an excellent repair method for these piles by creating a shell around the piles, shielding them from the elements. To further improve the repair, this shell cre-ates a cast-in-place form that can be filled with grout to recreate the concrete cover for the reinforcement that has disappeared. Additionally this type of repair benefits greatly from the use of inorganic Fiber Reinforced Polymer. Inorganic materials will not degrade from exposure to water, even saltwater, and will last longer than conventional organic polymers. Inorganic polymers will also form a chemical bond with the concrete piles ensuring that they will not delaminate over time and will remain in place to protect the pile.

Fiber Reinforced Polymer repairs are increasingly being used for concrete structures as they can be rapidly applied and are more economically feasible than alternative systems or struc-ture replacement. This increase in use has made them a more widely accepted for repairing a wide variety of concrete struc-tures. Furthermore their increased use has unearthed the lim-itations that conventional organic FRP systems have based on their chemistry and durability. These shortcomings create an opening for better products, specifically inorganic polymer FRP repair systems. Inorganic polymers offer superior bonding to concrete and steel by creating both chemical and mechanical bonds, ensuring the FRP does not de-bond from the surface they are repairing. Furthermore inorganic systems offer supe-rior durability compared to any other system available on the market. The merging market for Inorganic Fiber Reinforced Polymers will continue to grow as structures continue to age and durable repairs become increasingly necessary around the world. w

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Waterproofing as a System - Practical Considerations and Waterproofing with Cementitious Systems

In today’s construction scenario, due to extreme require-ments, we put tremendous stress on speed, economy and construction practices. A combination of these factors affects

the durability of concrete in several ways. In Indian conditions, where waterproofing is very important more often than not. It is not executed in a technically correct manner. Due to these construction and/or material problems, structures both above and below the ground are susceptible to waterproofing prob-lems. Dampness entering the living space (especially through ceilings and walls) is an indication that the structure has failed in durability and that structural elements have already begun deteriorating.

Waterproofing is important in protecting the structure and ensuring that it is usable over its service life. The forces exerted by water are enormous and its effects are unpredictable. Water enters the structure through the weakest route. Therefore the best possible way to ensure waterproofing is to place “multiple barriers” between water and the living space. A reliable water-proofing system installed by professionals is essential to achieve lasting protection from water damage. Much is demanded here from both the material and its applicators.

The most important aspect for any waterproofing treatment is its performance. Materials and systems should be tested for capillary absorption as well as penetration under hydrostatic pressure. Such tests are available internationally and materials can be tested anywhere in the world to adhere to ASTM/EN standards. In India IS 3085 can be used to test water penetration under pressure.

Why Waterproofing?

Concrete is a wet table material and has affinity to water. Water enters the body of concrete through hydrostatic pressure or capillary action or both. The capillary suction of dry or par-tially dry concrete can be equivalent to a hydrostatic pressure through cracks and crevices. Water passes end to end through concrete, either in the liquid or vapor phase, through intercon-nected voids. In the concrete, there are gel pores, capillary pores and entrapped air. Permeability is a function of capillary poros-ity and water-cement ratio. Permeability of concrete to liquids, ions and gases is of direct relevance to both its durability and to it sleak - resistance. The basis of waterproofing is thus, to mini-

mize permeability and / or wet table characteristics of concrete.Concrete by and large offers good resistance to moisture

penetration if recommended procedures were followed in mix design, workmanship, mixing, transporting, placing, vibration, and curing. However, conditions may nevertheless, develop where concrete may further need protection against water in-gress.

Consequences of Dampness / Leakage

There are several harmful or undesirable effects of leakage in a building. When water penetrates the structure, corrosion begins in the reinforcement and cracks develop in the con-crete. This may cause structural failure later in the life of the structure. Dampness in floors also leads to health and safety problems. Unsightly marks appear on the walls due to dampness and seepage causing discoloration, shedding of plasters and efflorescence. Dampness attracts and breeds termites or oth-er biological organisms. With deterioration of concrete and the reinforcement, the durability of the structure is endangered. Dampness causes short circuits from electrical installations, which may act as possible fire hazards. Dampness in labo-ratories or technical workshop may cause failures or damage sophisticated equipment.

Waterproofing Principles

Waterproofing is the treatment of a surface or structure to prevent passage of water into it or out of it. There are various forces that can act alone or in combination, to force water into concrete. These forces include hydrostatic pressure, capillary action, wind-driven rain, difference between vapor pressure between two sides of concrete or some combination of these. Waterproofing differs from damp proofing in that the former consists in the positive prevention of movement of water under pressure. Water enters the concrete structure through inter-connected voids and pores, cracks, structural defects or through faulty joints.

Here it is important to consider, in many projects damp proofing is expected of the waterproofing system. There is a clear difference between the two. As per ACI Committee 515 report, waterproofing is a treatment of a surface or structure to prevent the passage of water under hydrostatic pressure while

Sunny SurlakerHead - Admixtures DivisionMC-Bauchemie India Pvt. Ltd.

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damp proofing is a treatment of surface or structure to resist the passage of water in the absence of hydrostatic pressure. While designing the waterproofing system, actual service con-ditions are to be borne in mind and the material to be selected accordingly.

Requirements of a Good Waterproofing System

The latest trend in waterproofing will be “Prevention is bet-ter than cure”. With high demands on durability, the thought process should turn to preventing water ingress through the concrete, either by provision of an external membrane or by manipulating the properties of concrete itself. This method en-sures that the concrete is protected against water and aggres-sive media and the structure is protected from failure through its design life.

This approach also follows the logic that “Waterproofing can only be as good as the Base Concrete”. Therefore, for new con-structions, this entails making good watertight concrete and for restoration projects, the substrate should be brought back to its initial state. This methodology also follows the Diktat “Put Mul-tiple Barriers” between the water and the living space / structural elements for best protection against water. This can be done by:

- Use of Watertight concrete- Liquid Applied Membranes

Though waterproofing problems are serious and at times look unsolvable, it has never been a difficult task to ascertain the reasons for waterproofing failures. Once the investigation is complete and after proper diagnosis, the waterproofing treat-ment passes through three distinct phases:

a. Selection of waterproofing systems and materials.b. Repairs to the existing structure and surface and surface

preparations.c. Application of specified waterproofing systems or treatments

The steps are intentionally formulated to include repairs and surface preparation as independent operations, as it has been observed that this very important step does not receive the attention it deserves. Many systems involving proper specifi-cations and proper selection of materials have failed only on account of improper pretreatment repairs and negligence of prop-er surface preparation. It is unlikely any waterproofing system properly applied under efficient supervision cannot guarantee the desired performance.

The dampness and water seepages are mostly from the following weak spots and zones:

a. Concrete or masonry constructions of high permeability.b. Weak spots on account of honeycombing and segregation

in concrete.c. Cold joints and construction joints.d. Improper pointing of brickwork or block work.e. Not providing water stops, water bars etc., wherever necessaryf. Not providing or improper sealing of expansion joints.g. Cracks during construction due to faculty concreting, faulty

design or natural settlements.h. Improper bonding at the interface of two different materials

of construction.i. Non-provision or failure of Damp proofing courses.

j. Improper surface treatment and wrong selection of coating materials.

k. Improper provisions of slopes and drainage.l. Improper sealing of plumbing and sanitary joints.

To address these weak spots, waterproofing materials should possess following basic requirements:

a. The material should provide water tightness(a combination of hydrophobicity and impermeability) to the system.

b. The material should have flexibility and elasticity to combat thermal and other stresses.

c. The material should have excellent bonding and adhesion properties both to the substrate as well as to ensuing treat-ments.

d. The material, as far as possible, should retain the breathing properties of concrete.

e. The material should have abrasion resistance if used as a topcoat.

f. The material should be easy to apply, preferably free from solvents, etc.

g. The material should be cost effective.h. The material should be resistant to algae, fungus and other

microbial attacks.

However, in the actual practice it is quite difficult to locate a material possessing all above requirements. The fact therefore becomes quite evident that there can be no universal material to solve all the problems and only a combination of materials can be fruitful. Judicial compromises are necessary but the problems become simpler when the waterproofing treatment is viewed as system and not as a material.

Stages of Waterproofing

There are four major components to the waterproofing system:

a. Impermeable Baseb. Treatment of Jointsc. Repairs and Surface Preparationd. Application of Surface Barrier (Cementitious Systems)

a. Impermeable Base

For any kind of structure and especially for structural ele-ments like foundations, slabs and shear walls, the main aim of waterproofing is to prevent the passage of water through the con-crete. Waterproofing can only be as good as the base. If the base itself is of very poor quality, no matter what treatment or the most modern material is applied, the waterproofing is bound to fail. Quite simply this can be achieved by good concrete technology and blocking the capillaries in concrete, using the following thought process:

- Having a dense aggregate gradation using available mate-rials

- Using high performance PCE polymers, to reduce permea-bility and Capillarity

- Use of materials like Silica-fume or Aluminosilicate slurries in concrete

- Use of highly specialized latest generation Integral water-proofing compounds that work on process of Dynamic Syn-Crystallization® (DySC) technology

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b. Treatment of Joints

A major impediment to water tightness of concrete is the drying shrinkage cracks developed if control joints are not pro-vided. Also there would be random cracking in concrete due to temperature contractions. If waterproofing is done at very early stages the cracks will be transferred to rigid surface barriers and would be major conduits for leakage. Therefore control joints should be well designed in addition to the unavoidable construction and expansion joints. Principally each joint is to be sealed by suitable joint sealants in addition to providing the wa-ter stops or water bars. Passage of water through joints can only be arrested by preventing migration or by forming water seals.

The joints should be properly prepared and the opposite faces should be parallel. Joint sealing material should be able to resist the joint movement. Joint covers are usually neoprene or silicone and should be installed giving due weight age to in-tersections. It should be remembered that in case of negative side waterproofing, the water stops and joint sealants are pri-mary defenses to water tightness.

c. Repairs and Surface Preparation

The surface to be coated must comply with the principles of building construction and should fulfill the structural require-ments, including properly designed slopes and drainage system to avoid stagnation of water. Before carrying out any repairs the basic principles of civil and structural engineering should be thoroughly adhered to.

Cracks: First it should be ascertained whether the cracks are structural or non structural. Secondly it should be estab-lished whether there is moisture ingress through the cracks and whether the cracks are moving or non-moving type. The width and depth of the crack plays a major role in deciding the material for repairing the cracks. Wider cracks can be cut open and filled with non-shrink materials having bonding properties. For finer cracks, injecting and grouting techniques with ep-oxies, polyurethanes and ready to use polymer grouts can be used. For leaking cracks, the Primary injection is carried out with foaming polyurethane resins and the secondary injection is carried out by low viscosity and flexible polyurethane resin. Figure 1 shows addressing Cracks by Injections (cementitious or resin-based)

Grouting: As a precautionary measure, low permeability concrete can be cast with low water cement ratios. Cement grouting techniques can be resorted to densify the concrete. It is advisable to use a non-shrink admixture in conventional cement grouts to impart the grout non-shrink characteristics. Ready to use, polymer modified grouts which are workable at low water cement ratios develop strengths of about 35 N/mm2 are very suitable for grouting even where the strengths are the criteria. All joints / voids should be neatly grouted.

Honeycombing: The techniques adopted for repairs of hon-eycombed patches will depend upon the extent of honeycomb-ing. If the areas are large, the concrete of same grade as of base concrete is fully suitable, when the concrete is still green. The aim should be to make the concrete or mortars non shrink and incorporate a bonding agent in the system for effective bonding of old substrate to new repair material. Prepacked, polymer modified repair compounds, which combine non-shrink, bond-ing as well as high strength characteristics are more suitable on account of price considerations as compared to epoxy mor-tars. Figure 2 shows Filling of afftected / honeycombed areas.

Figure 1: Injections

Figure 2 - Repairing Voids

Figure 3: Quick setting plugging mortar

Leakage and seepage spots and zones: Using polymer modified Quick Setting Plugging mortars can stop leakages. If water is leaking through cracks, releasing the pressure and re-routing of water is required before using quick setting plugs might be necessary. Figure 3 shows application of Quick-Set-ting Plugging Mortars.

These measures should stop the leakages completely before application of surface barriers. If leakages are still observed, PU injections should be resorted to. Water compatible PU in-jections can also be undertaken as Grid Injections if larger ar-

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Figure 4: Equivalent cover Figure 5: Bathroom Detail

eas show leakage due to bad and porous concrete. Only after the leakages are controlled, surface barriers can be applied. In case of negative waterproofing the repairs should be total. The repairs should be followed with proper surface preparation de-pending upon the type of treatment foreseen.

The surface preparation plays a key role in success of any waterproofing system, whether the materials are conventional or new generation. Prior to waterproofing it should be ensured that the surfaces are totally free from remnants of form oils or curing compounds. The surfaces should be totally free from loose materials, dust, oil, grease and other contaminations. Bonding of surface barrier materials has to be ensured. De-pending upon selected barrier materials, degree of surface water / moisture content of the substrate is to be checked.

d. Surface Barrier Materials

One of the major parts of waterproofing is the selection and application of surface waterproofing barriers. The main function of these barriers is to arrest the passage of water through the body of concrete either by capillary action or hydrostatic pres-sures. The surface applied barrier materials are not a substitute to joint sealants, which are to be applied in the third dimension. Only few of these materials can be applied both for Positive side and Negative side waterproofing. The performance of barrier materials for Waterproofing and Damp proofing should also be checked for exposure to aggressive soil contaminants.

Though several materials are available as surface protec-tive systems, the concept of waterproofing has remained the same, which is the tanking system. Waterproofing acts as pro-tective envelope to arrest entry of water into the concrete. Built up bituminous waterproofing membranes were very popular few years back and they were bonded to the surface either by self-adhesion cold application or heat welding. Major difficulty in the application of bituminous or polymeric bituminous mem-branes was covering the geometry of the structure, overlap-ping joints and use of moisture sensitive adhesives to bond the membrane to the substrate.

Liquid Applied Membranes became more popular in the last decade on account of their ease of application and mould-ability to form seamless membranes over any curvature. Some Liquid Applied Membranes are of the non-breathable type and this would give rise to blisters and craters, which would eventu-ally affect the barrier performance.

Waterproofing by cementitious slurries is becoming more popular on account of ease of application, compatibility with substrate as well as competitive pricing. The slurries are avail-able in rigid and flexible types. Cementitious slurries are man-

ufactured by incorporating acrylic polymers either in powder or liquid form depending upon flexibility required. Old generation Waterproofing slurries were rigid and therefore were not suit-able for Waterproofing because of transference of cracks from base concrete to the Waterproofing system. Availability of new acrylic raw materials made the formulations of flexible water-proofing slurries possible to counteract the rigidity factor.

Crack bridging characteristics is one of the most important criterions for the flexible slurries as well as chloride diffusion is an added feature for underground structures. These slurries are of breathable type, which contribute to better waterproofing on account of no blistering and bubbles. There are other properties imparted to waterproofing slurries like crystallization. However, some data of testing available concludes that this property is not established with respect to permeability testing. The crystalline and chemical coatings react chemically with the free lime in ce-ment in presence of moisture and provide capillary repellency. Small shrinkage cracks are also autogenously healed. Careful surface preparation is the key to success of these cementitious waterproofing slurries. The biggest advantage of waterproofing slurries is its ability to adhere to damp, wet or moist surfaces. Another benefit, these waterproofing membranes provide is equivalent cover to concrete. For e.g. MC’s 2-Component Flex-ible Cementitious Elastic Material at 2mm thickness provides a cover equivalent to 72 cm of well-compacted M30 Concrete. This feature allows these materials to be used in repair and protec-tion projects apart from waterproofing applications.

Some Additional properties / advantages of 2 component cementitious Liquid applied Membrane Forming Systems include:

- Crack bridging- Breathable- Thermal resistance- Water tight- Easy application to both dry and moist surfaces- Good bonding to the substrate- Resistant to aggressive waters, chlorides, sulphates, etc.

One disadvantage of this material is resistance to abrasion, which can be very easily addressed by means of a waterproof plaster, screed or tiling system.

Applications for these kind of membranes are multifold, in basements, wet areas, swimming pools, tanks, dead walls, ter-races, terrace-gardens, structural elements and so on. The main point to remember while using a slurry-applied membrane is the correct detailing of joints, water stops and interfaces (cov-ings) between horizontal and vertical surfaces.

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Figure 7: Swimming pool detail

Figure 6: Basement detail

Figure 8: Importance of WP detailing

Flexible 2 component cementitious systems, when used in conjunction with injection grouting, crystallization based water-proofing slurries, waterproof plasters, tile adhesives, etc. and applied over good concrete fortified with a Dynamic SynCrys-tallization Based Integral Waterproofing Additive, has shown tremendous success over the last decades. As always, detailing is the key to successful application. Figures 4, 5 and 6 show in-depth detailing for basement structures, wet area bathrooms and swimming pools. Using the same material systems with varied detailing can help enhance durability of waterproofing on key-projects.

Conclusion

Today’s specifier or constructor has innumerable materi-als at his disposal, each claiming to be the best. Most of these materials are characterized by generic properties. These prop-erties are suitable for Quality Control to produce batch certifi-cates, but do not address the waterproofing system as a whole. The best waterproofing system is made of Good Base, Good Material and Good Application.

The success of waterproofing system depends not only on the materials alone, but also more on application and under-standing limitations of the materials in question. Rather than asking for Guarantees from applicators, which has not stopped failures, the adherence to Quality Assurance systems should be reverted to. Guarantees can only be asked from bonafide, qual-ified and authorized applicators. There are quasi-governmen-tal institutions abroad, e.g. BZB in Germany, which issues IRP certificates to trained, qualified applicators. Such qualifications should form a part of specifications. Under most circumstanc-es the concrete cast should be Waterproof High Performance Concrete, keeping in mind the “prevention is better than cure” motto. Even for such materials test certificates conforming to international codes and certified by bonafide agencies must be procured.

Finally, it is the best practices to be followed in construction, which will ensure that the longevity of the structure is main-tained and the structure is cost effective over its design life. w

CONCRETE: WATERPROOFING