Effect of high temperature on fly ash-based alkali activated concrete compared to Portland cement concrete

Sustainability and durability of concrete structures is an issue in today's world. This paper presents comparative study of effect of high temperature on fly ash-based alkali activated concrete, activated with sodium-based activators and ordinary Portland cement concrete for same grade. Residual compressive strength, split tensile strength, flexural strength, bond strength and modulus of elasticity were evaluated for both concretes at temperatures of 27°C, 500°C, 700°C and 900°C. It was found that alkali activated concrete with fly ash had 16% reduction in compressive strength as compared to 40% reduction in ordinary cement concrete. Similarly reduction in other mechanical properties like split tensile strength, flexural strength, bond strength and modulus of elasticity for fly ash-based alkali activated concrete was less compared to ordinary Portland cement concrete. This indicates that alkali activated concrete can be a viable alternative to ordinary Portland cement concrete during its exposure to high temperature. The highlights of the paper are: 1) mechanical properties of fly ash-based alkali activated concrete at elevated temperatures were evaluated; 2) effect of high temperature on fly ash-based alkali activated concrete and OPC concrete was compared and fly ash-based alkali activated concrete was found to be superior to ordinary cement concrete in all mechanical properties.