Experimental investigations on mechanical properties of normal and high strength high calcium geopolymer concrete

Abstract

Alkali activated (Geopolymer) concrete is an excellent and viable alternative to Portland cement based concrete as it can be produced using industrial by-products such as Ground Granulated Blast Furnace Slag (GGBS) and fly ash (source of reactive alumino-silicates) along with less energy craving ingredients such as alkali activators. In this study, slag based geopolymeric concrete mixes of M40 and M80 grade were prepared using GGBS and fly ash in proportion of 70:30 by weight. Geopolymeric binder was activated using combination of Sodium hydroxide and Sodium Silicate. Activator modulus (i.e. SiO2 / Na2O) was maintained as 1 and Na2O was kept as 7% and 8% by weight of total binder respectively for M40 and M80 grade geopolymeric concrete mixes. Both the concrete mixes were evaluated for fresh properties of concrete (slump and air content) along with mechanical properties of hardened concrete. Performance of geopolymeric mixes was compared with two conventional concrete mixes of equivalent grade (i.e. M40 and M80) in terms of aforementioned mechanical properties. Study concludes that slag based geopolymer concrete mixes of a particular strength were developed at significantly lower total binder content in comparison to cementitious binder required for development of conventional Portland cement based concrete of equivalent strength. Early age compressive strength of normal strength geopolymeric concrete mixes is higher in comparison to conventional concrete mix. Modulus of elasticity and Poisson’s ratio of geopolymeric mixes of both normal and high grade are observed to be lower in comparison to their corresponding conventional concrete mixes of equivalent strength.