Influence of composition and concentration of alkaline activator on the properties of natural-pozzolan based green concrete

Abstract

The chemical constituents of precursor materials, the composition and concentration of alkaline activators, volume of free water, and curing conditions are some of the mix design variables that influence the fresh and hardened properties of alkali-activated binders (AABs). To achieve desirable engineering properties and long-term performance of an AAB under various exposure conditions, each of these variables has to be carefully controlled. The reported research focused on the influence of concentration and composition of alkaline activators on the properties of natural pozzolan (NP)-based AAB. Since the molarity of sodium hydroxide (SH) and the ratio of sodium silicate (SS) to sodium hydroxide (SH) influence the properties of an AAB, the NP-based AABs were prepared by varying the SS to SH ratio from 2.0 to 2.75, at an increment of 0.25, and the molarity of SH from 8 to 14. The developed AAC specimens were tested to evaluate the strength development and the binder was characterized using SEM, XRD and FTIR techniques. A SS/SH ratio of 2.5 and 14 M SH solution were required to obtain maximum strength and dense microstructure. In addition, it was established that there exists an optimum silica modulus of the combined activator that results in faster polymerization of the precursor material.