Geopolymer concrete prepared using fly ash is a unique environment friendly construction material. It is essential to know the hardened properties of geopolymer concrete (GPC) for design purpose. For better density well graded aggregate is needed. In most of the rivers, coarser sand is available which is less suitable as a fine aggregate for concrete. However, the fine sand is abundantly available in the creek, which is called sea sand. In this work the fly ash based GPC has been prepared with 45 % river sand plus 55 % treated sea sand as a fine aggregate. It is impossible to provide the hot air (temperature) curing to fly ash GPC structural elements. Push-off shear strength of GPC has been evaluated of four different mixes of fly ash with temperature curing and ambient curing. ordinary Portland cement (OPC) is added by 4 % in the mixes of ambient curing. For compressive strength 100 mm size cubes and for shear strength the push-off specimens (S-shaped) of 100 × 100 × 300 mm have been casted. Toughness for shear has been evaluated from load deflection curve. The results show the geopolymer concrete with temperature curing gives greater shear strength than that of geopolymer concrete with ambient curing. But geopolymer concrete with ambient curing gives the higher shear strength than the similar grade of cement concrete.