Properties of slag geopolymer concrete modified with fly ash and silica fume

Abstract

This research focused on the role of fly ash and silica fume on slag geopolymer concrete through investigating workability (slump, and slump loss), initial setting time, final setting time, and mechanical properties of slag geopolymer concrete (S-GPC) (compressive strength, splitting tensile strength, modulus of elasticity) in addition to scanning electron microscope (SEM) and X-ray analysis. The considered variables included fly ash content as a replacement of ground granulated blast furnace slag (GS) (0%, 10%, 20%, 30%, and 40%), presence of silica fume as a replacement for slag, concentration of sodium hydroxide, NaOH, (molarity: 10, 16, and 18 mol/L), additional water content (7.5%, 11%, 14%, and 20%), and curing type (thermal, air, and water curing). S-GPC yielded rapid stiffening and high slump loss with high mechanical properties. The use of silica fume or fly ash or a mix of both enhanced workability, decreased rate of slump loss, and delayed setting time. The ACI 318 equation overestimates splitting tensile strength of FS-GPC.