Influence of Fineness of High Calcium Fly ash on Properties of Geopolymer Paste

Abstract

This article presents the influence of fineness of high calcium fly ash (FA) on properties of geopolymer paste. The high calcium fly ash was classified according to its fineness, namely, original fly ash (OFA), classified medium fly ash (MFA) and fine fly ash (FFA). Sodium silicate (Na2SiO3) and 10-molar sodium hydroxide (NaOH) solutions were used as the alkaline solutions in the reaction. The Na₂SiO₃/NaOH ratio of 2.0 and the liquid/binder (L/B) ratio of 0.60 and curing at ambient temperature were used for in all cases. The results showed that the setting time decreased while the compressive strength increased with an increase in the fly ash fineness. In addition, the microstructure of MFA and FFA was denser than that of OFA. However, comparison between MFA and FFA indicated that the their mechanical properties and microstructure were quite close. The compressive strength at 28 days of MFA and FFA geopolymer pastes were 56.2 and 56.9 MPa, respectively