Effect of Sodium Sulphate on Rheological Behaviour of Alkali Activated Slag Binders

Abstract

Alkali-activated binders (AABs) are alternative binders to OPC which can reduce carbon emissions. AABs use a precursor (mostly a by-product) and alkaline activator that produces a binder having cementitious properties. However, a few drawbacks like faster setting time and high drying shrinkage hinders their application on a larger scale. The time available to work at ease with these materials depends on the kinetics of the reaction and rate of flocculation; which in turn is dependent on composition of the precursor, solid content, type of activator and activator dosage. The amount of calcium present in the precursor is one of the factors that govern the early reaction kinetics. Similarly, the concentration and type of alkali ions in the system have a significant effect on rheological behavior. In order to use AABs in large scale applications, it is essential to understand the effect of various parameters on the workability of mixtures. The objective of this study is to evaluate the effect of sulphate content on the rheological behavior of alkali-activated slag binders and it was found to have a significant effect on the evolution of yield stress and apparent viscosity.