Influence of heat treatment on the mechanical properties of alkali-activated fly ash-based binders with marble dust substitution

Abstract

Marble waste contains a high level of calcium, which is obtained from the cutting process in marble production. The properties of geopolymer binders are influenced not only by the amount of alkali activators, their ratio, the molarity used, and the Si and Al content of the mineral additives used in the mixture, but also by the duration of the heat treatment and the heat treatment temperature. This study aimed to produce alkali-activated geopolymer binders based on fly ash and marble dust. Alkali-activated geopolymer pastes were made both with heat treatment for 24h at 70°C and without heat treatment at (23±2) °C. Structural analysis by optical microscopy revealed, in the case of heat-treated samples, the formation of pores with an average size of 1÷1.5 mm, much larger than in the case of samples without heat treatment.