Synergetic Effect of Met kaolin for Developing Fast Setting Early Strength Self-Compacting Concrete

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Pavan Kumar Diddi, Pushpendra K Sharma, Amit Srivastava

Abstract

One of the chief apprehensions in the construction industry is utilisation of industrial waste by-products which are mostly industrial waste by-products like fly ash(FA), ground granulated blast furnace slag(GGBFS), micro silica(MS), etc, having potential pozzolanic nature in concrete as supplementary cementitious materials(SCMs)for attaining the sustainability in concrete construction and also improving structural properties of concrete. The addition of various types of SCMs in concrete enhances the performance, decreases the calcium hydroxide quantity by ingesting it through a pozzolanic reaction. SCMs are vital constituents of self-compacting concrete(SCC) mixes which are characterised by free-flowing, high workable nature producing a pleasing surface finish. It is well established that with the addition of SCMs, in concrete, enormous nucleation locations are formed owing to the dissipation of fine pozzolana particles in the paste causing compact filling of the pores formed within the cement and thereby diminishing the barrier effect in the transition zone between the paste and aggregate thereby enhancing uniformity of mix. Previous studies directed towards the effects of SCMs particularly metakaolin(MK) in concrete where a significant augmentation of the mechanical characteristics and durability properties of the hardened concrete specimens was observed, providing sound opinions regarding the need for further investigation of the effects of MK and its resourcefulness as a promising SCM for increased future use. MK is slowly gaining its place as an extremely resourceful pozzolanic material, through its high pozzolanic response, to yield calcium silicate hydrates(CSH) and stratlingate(C2ASH8) and hydro garnet(C3AH6) thereby enhancing the early strength and durability of concrete. In this experimental investigation two types of ternary blended sustainable early strength M50 grade SCC mixes were formulated one with part replacement OPC with MK, in various proportions ranging from 2.5% to 20%, and with 25% FA (designated as FMK0,2.5,5 …20 series mix). Another SCC mix was with similar OPC+MK combinations as above but with 25% GGBFS (designated as GMK0,2.5,5 …20 series mix). A comparative analysis was made for the synergetic effect of MK in FMK series mix and GMK series mix with reference to controlled mixes in the fresh and hardened state, and analyzed by a comprehensive set of rheological parameters like flow, flow time, L box flow, segregation resistance, initial setting and final setting time in a fresh state of concrete; mechanical properties, durability characteristics in the hardened state in order to optimize the combinations for establishing the suitability of blends for developing fast setting early strength SCCs

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