Development of Fly Ash Based Geopolymer Concrete for Ambient Curing Condition

Fly ash based geopolymer is a prospective construction material for its environmental and functional benefits over ordinary Portland cement concrete. However the necessity of heat curing is one of the major drawbacks that hinder its application in cast-in-situ concreting. The main focus of this study is to develop fly ash-based geopolymer concretes suitable for ambient curing condition. Geopolymer mortar was prepared with Class F fly ash and ordinary Portland cement (OPC) was added as an additive in different proportions with fly ash to enhance the early age properties of concrete. Fly ash was activated by a mixture of sodium hydroxide and sodium silicate solutions. Samples were cured in ambient condition (about 23oC and RH 65±10%) until tested. The workability in terms of flow, setting time and compressive strength of mixtures blended with OPC were compared with those of the control geopolymer mixture having fly ash only as the binder. In ambient temperature, the geopolymer pastes using fly ash only may take more than 24 hours to set. Inclusion of OPC reduced the setting time to acceptable limits. The early-age compressive strength improved significantly by the inclusion of OPC as compared to that of control geopolymer concrete cured at ambient condition