Fracture properties of geopolymer concrete cured in ambient temperature

Geopolymer concrete (GPC) is a promising alternative of ordinary Portland cement (OPC) concrete. Recent studies indicate potential benefit of heat cured geopolymer concrete in structural applications. This study aimed at the fracture behavior of fly ash based geopolymer concrete cured in ambient temperature. Geopolymer concretes were prepared with mainly fly ash as the binder which was activated by a mixture of sodium hydroxide and sodium silicate solutions. Ground granulated blast furnace slag (GGBFS) was added up to 20% of total binder and amount of alkaline solution was varied to determine the effect on concretes subjected to ambient curing. Notched beam specimens were cast and cured in air at 16-22 oC and 70 ± 10% relative humidity. Three-point bending test was conducted using a closed-loop universal testing machine. The fracture energy values were calculated from the load-deflection curves of the test specimens by using the work of fracture method. The critical stress intensity factors of the specimens were also calculated. The load-deflection curves and the fracture behavior of different geopolymer concretes were compared. Generally, the fracture energy varied with the strength of the concrete. The fracture energy of concrete having slag in addition to fly ash was higher than that having only fly ash. Geopolymer concretes achieved higher fracture energy values as compared to OPC concrete of similar compressive strength