Characterisation of One-Part Geopolymer Binders Made from Fly Ash

Abstract

The kinetics of one-part “just add water” geopolymerisation reaction is studied in the system of fly ash as an aluminosilicate precursor and solid sodium silicate as alkali activator. The rates of the release of Si and Al nutrients from source materials can significantly affect their availability for reaction and their extent of participation in geopolymer gel structure. The crystalline phases that usually appear in fly ash geopolymers are missing in the one-part mix binders studied here, and by increasing the Si/Al ratio the amount of Si contribution in the final geopolymer gel is decreased. The sample with lower water content sees the participation of more Si in both stages of gel formation. Adjusting the composition of raw materials can improve the mechanical properties of the final one-part mix binder. Reasonable mechanical strength with the maximum strength of 65 MPa is achieved.