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PRESENTED BY ANIKET GHOSH DASTIDARCONSTRUCTION ENGG. 4TH YEARJADAVPUR UNIVERSITY

STUDY ON DURABILITY & PROPERTIES OF HIGH PERFORMANCECONCRETE WITH ALCCOFINE AND FLY ASH

High performance concrete refers to a mix of concrete that has the following properties:

High strengthHigh modulus of elasticityHigh abrasion resistanceHigh durabilityLow permeability and diffusionResistance to chemical attack and frostEase of placementCompaction without segregation

What is High Performance concrete (HPC) ?

Alccofine Micro Materials are a range of products of Counto Microfine Products Pvt. Ltd (CMPPL) a joint venture between ACL and the Goa-based, Alcon Group, launched in the year 2013.The two products that have been launched are Alccofine 1203 (a supplementary cementitious material suitably replaces Silica fume used in high performance concrete); and Alccofine 1101 (a micro-fine cement based product used for injection grout in underground tunnels and soil stabilization etc)It is a new-generation, ultrafine product whose basic raw material is slag of high glass content with high reactivity obtained through the process of controlled granulation. The raw materials are composed primarily of low calcium silicates. The processing with other select ingredients results in controlled particle size distribution (PSD). Due to its unique chemistry and ultra fine particle size, ALCCOFINE 1203 provides reduced water demand for a given workability, and can also be used as a high range water reducer to improve compressive strength or as a super workability aid to improve flow. What is Alccofine?

ALCCOFINE1203 performs in superior manner than all other mineral admixtures used in concrete within India. Due to its inbuilt CaO content, ALCCOFINE1203 triggers two way reactions during hydration Primary reaction of cement hydration.

Pozzolanic reaction: ALCCOFINE also consumes by product calcium hydroxide from the hydration of cement to form additional C-S-H gel, similar to pozzolans.

This results in denser pore structure and ultimately higher strength gain. This study presents the results of examination carried out on ALCCOFINE1203 in comparison with Silica Fume in concrete, and the effect it has on workability, water requirement, admixture requirement, strength and durabilityHow Alccofine works?

The chemical composition and the physical properties of Alccofine are as follows:

Properties of Alccofine 1203Chemical Analysis Mass % Physical analysis Range

CaO 62-64 Bulk Density700-900 kg/m3Al2O3 5-5.6 Surface Area 12000 cm2/gmFe2O3 3.8-4.4 Specific gravity2.9SO3 2-2.4Particle Size, d10< 2 MgO0.8-1.4 d50< 5SiO221-23d90< 9

Particle size distribution comparison

Following are the technical benefits of using Alccofine 1203Improved workability and cohesiveness and reduced shrinkage: Having better particle-size distribution compared to other supplementary cementitious materials (SCMs), which provide a dense matrix pore structure resulting in better workability, cohesiveness and superior volume stability (shrinkage).Better retention of workability: Offering better compatibility with cement and certain chemical admixtures, its physical/chemical structure on hydration improves the workability retention properties of fresh concrete.Reduced segregation: Ultrafine slag improves particle packing in the cementitious paste by filling cement particle voids by virtue of proper distribution of particles, whereby it reduces the bleed water and results in more homogeneous concrete with reduced segregation.Improved flow ability: The material has better particle packing, which results in improved rheology resulting in improved flowability.

Advantages

Improved durability: Resulting in a dense pore structure, which restricts the ingress of chloride and sulphate ions, this green material, unlike other equivalent material, makes concrete more alkaline, thereby protecting the reinforced steel in concrete and providing a durable structure.Improved strength gain: Ultrafine slag results in the formation of a dense pore structure, and in-built Ca(OH)2, due to cement hydration, provides an increased secondary hydrated product resulting in improved strength gain at early as well as later stages. It can be used to achieve strengths as high as M120 if mixed in proper proportions.Retention of alkalinity: Ultrafine slag has lime content of about 34 per cent that, during hydration, helps retain higher alkalinity in pore solution, thereby mitigating corrosion.Improves resistance to chemical attack: Because of its finer pore structure and chemical stability, ALCCOFINE 1203 in concrete is substantially more resistant to chloride diffusion. Thus, it reduces the penetration of chlorides in concrete and protects embedded steel from corrosion. CaO available in ALCCOFINE 1203 Contribute to maintain Ca(OH)2 as buffer in pore Solution, which helps to maintain pH of pore solution Reduces heat of hydration Lowers permeability

The effect of Alccofine on the workability of a concrete mix was checked by carrying out a slump test. The grade of concrete used was OPC 43.Two mixes were prepared one having Fly ash and silica fumes as additive to the cement, while the other having Alccofine 1203 and Fly ash as the additive.A new generation Poly-Carboxylic Ether (PCE) based super-plasticizer was used. This super-plasticizer is available as a medium brown coloured aqueous solution.The Slump was greater in the mix containing Alccofine rather than the one with Silica fumes

Effects on workability

Due to its unique particle size distribution and inbuilt CaO , ALCCOFINE 1203 results in to formation of dense pore structure, which results in improved workability and workability retention . The value of flow decreases in silica fume mix concrete and hence the optimum super plasticizer dosage increases, whichcan be attributed to high specific surface of silica fume

For carrying out tests on compressive strength , the grade of cement used was OPC 53.Two ternary blend of concrete were prepared , one containing Fly ash and Alccofine (Type I) and the other containing Fly ash and Silica Fumes (Type II).For each mix of concrete, three concrete cube specimens were cast each of size 150mm x 150mm x 150mm. To obtain a homogeneous mix, aggregates were mixed and binders (cement, FA and AL) were added to the system. After remixing, water was added to the dry mix. Finally, super plasticizer was introduced to the wet mixture.The cubes were cast in three equal layers and each layer was compacted by using a vibrating table and for beam specimen (for calculating flexural strength) needle vibrator was used.The optimum doses of Fly ash and Alccofine in Type I mix were varied by trial and error till the optimum dose, corresponding to which the highest compressive strength is obtained, was achieved. This was found to be 20% (Fly ash) and 8% (Alccofine) by weight of cement.Effect on compressive strength

Similarly for Type II mix, the doses were varied by trial and error and the optimum doses achieved were 25% (Fly ash) and 10% (Silica fume) by weight of cement.Water-cement ratio used was 0.4 for both mixes. Mix proportion used for the blends were

ItemQuantity (Kg/m^3)Cement (72%)310.25Alccofine (8%)34Fly ash (20%)85Coarse aggregate1096Fine aggregate838Water170Admixture4

Type I mixItemQuantity (Kg/m^3)Cement (65%)276.25Silica Fume (10%)42.5Fly ash (25%)106.25Coarse aggregate1096Fine aggregate838Water170Admixture6

Type II mix

The results were as follows

Compressive StrengthFlexural Strength

The test was used to measure the impermeability of concrete. According to this test the cubes were initially water-cured for 28 days, and then exposed to water pressure of 5 bars for 72 hours after which the cube was divided and the depth of water penetration measured. Penetration of less than 25 mm is generally considered to be impermeable concrete.The cubes were made from the Type I and Type II mixes that were cast for the compressive strength test.The permeability results obtained were(i) Alcofine mix : 13 mm(ii) Silica Fume mix : 18 mmAs per the results described above we can see that the water permeability in case of ALCCOFINE 1203 is less than that of Silica Fume. Presence of ultra fine Cementitious / pozzolanic materials allows denser packing between cement particles and reduces the wall effect in transition zone between the paste and the aggregate. This refines the concrete microstructure and enhances the degree of impermeability and the strength characteristics of concrete.

Water permeability

The chloride penetration test was compared between ALCCOFINE 1203 and OPC. The ASTM C 1543 test measures the penetration of chloride ion into concrete. Three slabs of concrete measuring 90mm thick and 300mm square surface area. The slabs used were water cured for 28 days.After the conditioning period 3% NaCl solution was ponded on a top surface for 90 days, while the bottom face was left exposed to drying environment.At the end of this time powdered samples by rotary impact hammer are obtained at various depths (10-20, 25-35, 40-50, 55-65mm). Chloride content of the sample from each depth were determined and reported . Chloride Permeability

Results obtained were as follows

Because of its finer pore structure and chemical stability, ALCCOFINE 1203 in concrete is substantially more resistant to chloride diffusion. Thus, it reduces the penetration of chlorides in concrete and protects embedded steel from corrosion. CaO available in ALCCOFINE 1203 Contribute to maintain Ca(OH)2 as buffer in pore Solution, which helps to maintain pH of pore solution. Denser pore matrix restricts chloride penetration and alkalinity forms passive layer on steel and protect it from corrosion

ConclusionIn this study, the effect of local Alccofine as supplementary cementing materials and filling materials on the strength and durability of concretes was investigated. It is apparent that ternary cementitious blends of Portland cement, alccofine, and fly ash offer significant advantages over binary blends and even greater enhancements over plain Portland cement. The combination of alccofine and class F fly ash is complementary: the alccofine improves the early age performance of concrete with the fly ash continuously refining the properties of the hardened concrete as it matures. In terms of durability, such blends are vastly superior to plain Portland cement concrete.

From the results obtained in this study, the following conclusion can be drawn :

Very high workability can be obtained by using mixes containing Alccofine rather than only OPC.

(ii) The minimum loss of weight and loss of compressive strength of concrete in Chloride Resistance test and Sea water test due to addition of Alccofine. Due to its more compactness and less permeability of concrete effect of Chloride Attack is reducing. This is converts leachable calcium hydroxide into insoluble non- leachable cementanious product. This pozzolanic action is responsible for impermeability of concrete. Secondly, the removal of calcium hydroxide reduces the susceptibility of concrete to attack by Chloride.

(iii) Alccofine increases the particle packing and it increases the strength of concrete.(iv) Very high resistance to chloride ion penetration can be obtained with ternary blends.(v) We concluded that compressive strength achieved by using Alccofine (8%) + Fly Ash (20%) is 54.89Mpa and 72.97 Mpa at 28 and 56 days respectively using OPC grade 53.

IS: 10262-1982, Recommended Guidelines for Concrete Mix Design, Fifth Reprint March-1998, Bureau of Indian Standards, New DelhiStudy on durability of high performance concrete with industrial wastes By Pazhani.K, Jeyaraj.R,ATI Volume 2, Issue 2, August 2010, pp. 19-28 M. Vijaya Sekhar Reddy, I.V. Ramana Reddy, 3 N.Krishna Murthy , Predicting the Strength Properties of High Performance Concrete using Mineral and Chemical Admixtures , VOL. 3, NO. 1, Jan 2013 ISSN 2225-7217References

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