Properties of low-calcium fly ash based geopolymer concrete incorporating OPC as partial replacement of fly ash

Results of an experimental investigation on the compressive strength and permeation properties of fly ash based geopolymer concrete are presented in this paper. Fly ash was partially replaced with 0, 10, 20 & 30% of ordinary Portland cement (OPC). Tests were conducted for compressive strength and permeation properties such as water absorption, porosity, sorptivity and rapid chloride permeability up to the age of 365 days. Findings from this investigation indicate that compressive strength increased with the increase in OPC content at all ages, with optimum being at 20%. The inclusion of OPC resulted in the reduction in water absorption, porosity, sorptivity, and chloride permeability of geopolymer concrete due to the improvement in microstructure caused by co-existence of hydrated products along with geo-polymeric alumina-silicate polymer structure. The results were also verified by the microstructural analysis, SEM, EDS, and XRD, which indicate better compacted and dense microstructure of geopolymer concrete with the addition of OPC.