SELF -COMPACTING CONCRETE (SCC)&

LIGHT-WEIGHT CONCRETE (LWG)

Group Members:

-Ayushi Mehrotra-Richa Shukla

-Warepam Bishworjit Mangang

SELF COMPACTING/CONSOLIDAT

ING CONCRETE Self-compacting concrete (SCC) has been described as "the most revolutionary development in concrete construction for several decades“.

Properties, Benefits & Advantages over conventional concrete• Faster construction• Reduction in site manpower, equipments and

onsite repairs.• Improved quality of concrete and its durability ,

reliability of structure .• Greater freedom in design• Thinner concrete sections• Reduced noise levels, absence of voids.• Safer working environment.• Lower overall cost.• Possibilities for utilization of “dusts“ which are

currently waste products and costly to dispose.

Concrete that is able to flow under its own weight and completely fill the formwork, even in the presence of dense reinforcement, without the need of any vibration, whilst maintaining homogeneity.

• Segregation resistance (stability)• The ability of SCC to remain homogeneous

in composition during transport and placing.

• Moderate viscosity.• Mixture self compacting ability allow the

elimination of macro-defects , air bubbles & honey combs responsible for penalizing mechanical performance and structure durability.

• Workability: A measure of the ease by which fresh concrete can be placed and compacted: it is a complex combination of aspects of fluidity, cohesiveness, transportability, compactability and stickiness.

• Unconfined flow ability (Filling ability, extremely flowing material).

• Passing ability , close to self-levelling & Low yield stress.

• High deformability .• Better surface finishes.• Easier placing .• Contains less water than standard

concrete .

Instead SCC gains its fluid properties from an unusually high proportion of fine aggregate , such as sand ( typically 50%) combined with superplasticizers & viscosity-enhancing-admixtures (VEA).

DISADVANTAGES• SCC requires high fluidity in tight joints

formworks , which slow downs the casting rate.

• Due to low water cement ratio , plastic shrinkage cracks may 0ccur , but this can be avoided by curing properly .

• Highly skilled and experienced workers are required for the production.

• More costly than other conventional concrete.

Selection of Mix Proportions 1. Air content (by volume)2. Coarse aggregate content (by volume)3. Paste content (by volume)4. Binder (cementitious) content (by weight)5. Replacement of mineral admixture by percentage binder weight6. Water/ binder ratio (by weight)7. Volume of fine aggregate/ volume of mortar8. SP dosage by percentage cementitious (binder) weight9. VMA dosage by percentage cementitious (binder) weight

Picture showing Slump test of SCC v/s Conventional

Concrete

REQUIREMENTS FOR CONSTITUENT MATERIALS Cement• General suitability is established for

cement 43 grade ordinary Portland cement (OPC) conforming to IS :383-1970(6) .

• Selection of the type of cement depends on the overall requirements for the concrete such as strength , durability etc.

• It should be fresh and without any lumps.

Constituents of SCC

Sand and fine aggregates• confirms to grading Zone II as per IS: 383-

1970 (Reaffirmed 1997).• The sand passing through 4.75 mm size

sieve is used in the preparation of concrete mix.

• The properties of sand such as fineness modulus and specific gravity as per IS: 2386-1963.

• water absorption is 1.5%. • bulk density of fine aggregate :- 1768 kg/m3.• All normal concreting sand are suitable for

SCC (either crushed or rounded) .• Particles smaller than 0.125 mm contribute

to the powder content.• A min amount of fines must be achieved to

avoid segregation .

Aggregate• The coarse aggregate 12.5 mm down size

graded confirm to IS 383-1970 (Reaffirmed 1997) locally available crushed stone obtained from local quarries.

• specific gravity of coarse aggregate is found to be 2.65.

• The water absorption is 0.3%.• The bulk density of coarse aggregate in

compact state is 1584kg/m3.• Well all type of aggregate are suitable. Size

varies 16 mm to 20 mm .however particle size up to 40 mm more have been used in SCC.

• Consistency of grading is of vital importance .• Gap graded aggregates better than those

continuously graded , which might experience greater internal friction and give reduced flow.

• The moisture content should be closely monitored and must be taken into account in order to produce SCC of constant quality .

• Crushed aggregates tend to improve the strength because of the angular particles , whilst rounded aggregates improve the flow because of lower internal friction .

Aggregates: Rounded & Angular

Water

• Potable water and it should be free from organic content , turbidity and salts confirms to IS 456-2000 .

Admixtures• Superplasticizers are an essential component of

SCC to provide the necessary workability. • Super plasticizer- PCE ,• AUROMIX 400 Commercially available

polycarboxylic ether based super plasticizer. It is an admixture of a new generation based on modified polycarboxylic ether. Its use enhances the workability of the mix and strength aspect, helps in producing a better compaction and finishing. It also permits reduction in water content .

• Air entraining admixtures (AEA) to improve freeze-thaw resistance, retarders for control of setting, etc.

• • High range water reducing admixtures - HRWRA Application of HRWRA provides fluidity of fresh concrete and reduces the required water quantity.

• • Viscosity modifying admixtures-VMA increase the cohesion of fresh concrete and can replace a part of mineral additions. They have the effect of cement paste densifying and keeping fine particles within the matrix.

• • Special admixtures for SCC –combined HRWRA + VMA: The majority of admixture manufacturers produce special admixtures for SCC which include both HRWRA and VMA within them. By application of these special admixtures, possible incompatibility inapplication of separate admixtures is avoided and desired viscosity of fluid mix is obtained.

.Additions (including mineral fillers and pigments) • Cement is replaced by 35% of fly ash by weight of

cementitious material. The specific gravity of fly ash is 2.12.• Filler ( Fly ash)- Filler Materials such as fly

ash, blast furnace slag, etc. • An extremely important aspect of the

durability of concrete is its permeability. • Fly ash concrete is less permeable because

fly ash reduces the amount of water needed to produce a given slump, and through pozzolanic activity, creates more durable CSH as it fills capillaries and bleed water channels occupied by water Soluble lime.

• Improves corrosion protection by decreasing concrete permeability.

• It can reduce corrosive chemicals and oxygen• Increase sulfate resistance and reduces

alkali-silica reactivity .

Blast furnace slag

Constituents of Fly Ash concrete

Typical additions are:Stone powder.• Finely crushed limestone, dolomite or granite may be

used to increase the amount of powder: the fraction less than 0.125 mm will be of most benefit.

Note: dolomite may present a durability risk due to alkali- carbonate reactionSilica Fume: • Silica fume gives very good improvement of the

rheological as well as the mechanical and chemical properties.

• Improves also the durability of the concrete.Ground (Granulated) Blast Furnace Slag: • GGBS is a fine granular mostly latent hydraulic binding

material, which can also be added to SCC to improve the rheological properties.

Ground Glass Filler:• usually obtained by finely grinding recycled glass. • The particle size should be less than 0,1 mm and the

specific surface area should be > 2500 cm2/g.• Larger particle sizes may cause Alkali-Silica reaction.Pigments

Silica Fume

Ground Granulated blast furnace slag

Fibers• Commonly used types of fibers are steel

or polymer.• Fibers may be used to enhance the

properties of SCC in the same way as for normal concrete.

• Steel fibers are used normally to enhance the mechanical characteristics of the concrete such as flexural strength and toughness.

• Polymer fibers may be used to reduce segregation and plastic shrinkage, or to increase the fire resistance.

• Ease of mixing and the placing processes proposed, shall be demonstrated by site trials to the approval of the engineer.

Steel fibers

Polymer fibers

REQUIREMENTS FOR SELF-COMPACTING CONCRETE Application area• SCC may be used in pre-cast applications or for concrete placed on

site.• It can be manufactured in a site batching plant or in a ready mix

concrete plant and delivered to site by truck.• It can then be placed either by pumping or pouring into horizontal or

vertical structures.• In designing the mix, the size and the form of the structure, the

dimension and density of reinforcement and cover should be taken in consideration.

• Due to the flowing characteristics of SCC it may be difficult to cast to a fall unless contained in a form.

• SCC has made it possible to cast concrete structures of a quality that was not possible with the existing concrete technology.

EXAMPLES OF STRUCTURES BUILTOF SELF-COMPACTING CONCRETBurj DubaiArlanda Airport Control Tower, Stockholm, Sweden.National Museum of 21st Century Arts(MAXXI) in Rome, Italy

Burj, Dubai

Arlanda airport control tower, Sweden

National museum of 21st century art, Rome

LIGHT- WEIGHT CONCRETE

(LWC)

LIGHT WEIGHT CONCRETE • Lightweight concrete is concrete with a

dense microstructure containing porous aggregates bonded any room temperature.

• Can be defined as a type of concrete which includes an expanding agent that increases the volume of the mixture while giving additional qualities.

• considered to be lightweight if the density is not more than 2200kg/m3 (the density of normal weight concrete is assumed to be between 2300kg/m3 and 2400kg/m3) and a proportion of the aggregate should have a density of less than 2000kg/m3. 

• Bulk density 5-18 KN/M3.• -Light weight Aggregate Concrete

-No Fines Concrete-Foamed Concrete-AAC (Autoclaved Aerated Concrete)

LIGHT WEIGHT AGGREGATECONCRETE Lightweight aggregate concrete can be

produced using a variety of lightweight aggregates. Lightweight aggregates originate from either:• Natural materials, like volcanic pumice.• The thermal treatment of natural raw

materials like clay, slate or shale i.e. Leca.• Manufacture from industrial by-products

such as fly ash, i.e. Lytag.• Processing of industrial by-products such

as pelletised expanded slab, i.e. Pellite.• The required properties of the lightweight

concrete will have a bearing on the best type of lightweight aggregate to use. If little structural requirement, but high thermal insulation properties, are needed then a light, weak aggregate can be used. This will result in relatively low strength concrete.

Pumice stone

Leca block

FOAMED CONCRETE• Foamed concrete is a highly workable,

low-density material in which air contained is maintained up to 40% - 80% of the total volume.

• The size of air bubbles: 0.1mm- 1.5mm.

• The main raw material for Foaming is Genfil & its organic substance.

• It is generally self-levelling, self-compacting and may be pumped.

• Foamed concrete is ideal for filling redundant voids such as disused fuel tanks, sewer systems, pipelines, and culverts - particularly where access is difficult.

• It is a recognised medium for the reinstatement of temporary road trenches.

• Good thermal insulation properties make foamed concrete also suitable for sub-screeds and filling under-floor voids.

NO FINES CONCRETE

• By omitting the fine aggregate from the mix so that a large number of internal voids are present; normal weight coarse aggregate is generally used. This concrete is no-fines concrete.

• There exist, therefore, large pores within the body of the concrete which are responsible for its low strength, but their large size means that no capillary movement of water can take place.

• Although the strength of no-fines concrete is considerably lower than that of normal-weight concrete, this strength, coupled with the lower dead load of the structure, is sufficient in buildings up to about 20 storeys high and in many other applications.

Typical Roof deck detail of Light weight concrete

AAC (AUTOCLAVED AERATED CONCRETE)

• AAC is well suited for high rise buildings and those with high temperature variations.

• AAC construction systems such as masonry units, reinforced floor/roof and wall panels and lintels are being used.

• It can also be sculpted and penetrated by nails, screws and fixings.

• It is a highly thermally insulating concrete-based material used for both internal and external construction & has lower environmental compact.

• AAC products include blocks, wall panels, floor and roof panels, cladding (facade) panels and lintels.

• Improved thermal efficiency reduces the heating and cooling load in buildings.

• Porous structure allows for superior fire resistance.• Larger size blocks leads to faster masonry work.• Workability allows accurate cutting, which

minimizes the generation of solid waste during use.

• Light weight saves cost & energy in transportation, labour expenses, and increases chances of survival during seismic activity.

Advantages • Rapid and relatively simple construction.• Economical in terms of transportation as well as

reduction in manpower.• Significant reduction of overall weight results in

saving structural frames, footing or piles.• Most of lightweight concrete have better nailing

and sawing properties than heavier.• Stronger conventional concrete.Disadvantages• The mixtures are very sensitive to water

content.• Difficult to place and finish because of the

porosity and angularity of the aggregate. I• In some mixes, the cement mortar may

separate the aggregate and float towards the surface.

• Mixing time is longer than conventional concrete to assure proper mixing.

ADVANTAGES &

DISADVANTAGES

OF

LIGHT WEIGHTCONCRETE

AGGREGATES USED TO PRODUCE

LIGHT WEIGHT CONCRETE

• Natural aggregates:• Inorganic Natural Aggregates: Diatomite,

pumice, scoria and volcanic cinders are natural, porous volcanic rocks with a bulk density of 500 – 800 kg/m3 which make a good insulating concrete.

• Organic Natural Aggregates: Wood chips and straw can be mixed with a binder to provide a lightweight natural aggregate. These are cellular materials which have air trapped within their structures once they have low moisture content.

• Manufactured aggregates: 1. Bloated clay, sintered fly ash and foamed blast furnace slag.2. Lightweight expanded clay aggregate: This is produced by heating clay to a temperature of 1000 – 1200 oC, which causes it to expand due to the internal generation of gases that are trapped inside. The porous structure which forms is retained on cooling so that the specific gravity is much lower than what was before heating it.

Shale Slate

Fly Ash

Thank you.