Effect of sand content on engineering properties of fly ash-slag based strain hardening geopolymer composites

Abstract

Strain hardening geopolymer composite (SHGC) is a tailored group of sustainable high-performance fibre reinforced geopolymer composites with strain hardening behaviour and ultra-high ductility. This paper experimentally investigates the effect of fine silica sand content (0–40% by weight of the geopolymer binder) on engineering properties of fly ash-slag based SHGC cured at ambient temperature, including workability, setting time, drying shrinkage, compressive strength, and flexural strength as well as deflection hardening behaviour that is particularly emphasised. The results indicate that all SHGC specimens exhibit deflection hardening characteristics along with large deflection and multiple microcracks distributed over the tensile side of the specimens. The widths of microcracks are within 300 μm and mostly smaller than 45 μm. The flowability, setting time, drying shrinkage and compressive strength of SHGC reduce with the increase of sand content at early ages up to 28 d. However, at 28 d, the incorporation of sand up to 20 wt% increases the flexural strength and toughness of SHGC, but the further increase of sand content up to 40 wt% results in a decrease in flexural strength and toughness.