Mechanical and Durability Properties of Fly Ash Geopolymer Concrete with Silica Fume

Contribution of cement manufacturing industries to global warming by emission of carbon dioxide gas has raised global concerns. In that case, geopolymer concrete (GPC) can act as an alternative to cement concrete. This paper presents mechanical and durability properties of GPC using 14 M sodium hydroxide solution. Optimum molarity is achieved replacing fly ash by silica fume by mass fractions of 5%, 10% and 15%. The mechanical properties of the concrete are obtained by conducting compressive, split tensile and flexural strength test. The durability properties are investigated by exposing the concrete specimens to aggressive chemical solutions of 2% sulphuric acid, 2% magnesium sulphate and 5% sodium chloride. The compressive strength of fly ash-based GPC at the age of 28 days varies from 16 to 38.5 MPa, whereas those of silica fume-blended GPC achieved up to 42.6 MPa. Further, the silica fume-blended GPC is found excellent resistance to chemical attack. It is observed that blending of silica fume with fly ash in GPC improves strength as well as exhibits satisfactory behaviour in aggressive environment, i.e. curing temperature of 70 °C. The concrete matrix is also investigated by conducting ultrasonic pulse velocity test and observing scanning electron microscopic images.