The recent technology of geopolymer concrete is a substitute material for ordinary portland cement concrete which is produced from the polycondensation reaction of aluminosilicate materials with alkaline activator solutions. The cost of river sand is high since the demand for the same is also high. Manufactured sand is used as a replacement material for river sand in geopolymer concrete. This paper mainly focuses to find the properties of fly ash (FA) – based geopolymer concrete under ambient cured temperature like compressive strength, stress strain behaviour, modulus of elasticity, Poission’s ratio and impact resistance. The result of geopolymer concrete is compared with ordinary portland cement concrete. The elasticity modulus and Poission’s ratio of geopolymer concrete are lower than conventional concrete. The Stress-strain behaviour of geopolymer concrete is similar to conventional concrete. The impact resistance of geopolymer concrete is very good when compared with conventional concrete. © 2020 De Gruyter. All rights reserved.