Investigation on effect of fly ash content on strength and microstructure of geopolymer concrete in chloride-rich environment

Abstract

This paper investigates the significance of fly ash content on compressive strength and microstructure development of geopolymer concrete (GPC) in a chloride-rich environment. In the present study, geopolymer concrete was prepared with different fly ash contents i.e. 425 kg/m3 and 450 kg/m3. To evaluate GPC in chloride-rich environment, sodium chloride of different concentrations were added to the alkaline solution during the time of casting of GPC mixtures. The testing of compressive strength was conducted on cube specimens at different testing ages. The analyses of XRD and FESEM were performed on GPC to analyze the microstructure. The results indicated that compressive strength of GPC reduced considerably with an increase in amount of fly ash for NaCl concentration up to 3%, including the control GPC. The compressive strength of chloride admixed GPC mostly decreased with an increase in the concentration of NaCl at both fly ash contents. The obtained XRD patterns and FESEM images of GPC showed the formation of sodium alumino-silicate hydrate (N-A-S-H) gel that contributed to the strength development of GPC.