The effect of cement composition and pH of environment on sulfate resistance of Portland cements and blended cements

Abstract

This paper presents an investigation into the sulfate resistance of Portland cements and blended cements. Four Portland cements of different characteristics and blended cements containing fly ash, ground granulated blast furnace slag and silica fume were used in this work. The performances of binders were evaluated in sulfate solutions maintained at different pH levels ranging from 3 to 12 using expansion of mortar prisms (ASTM C 1012) and strength development of mortar cubes. The results indicate that sulfate resistance of cementitious materials is dependent on its composition and on the pH of the environment. Portland cement with low C 3A and low C 3S performed well in all sulfate solutions. Blended cements containing silica fume and fly ash (particularly at 40% replacement) showed a more superior performance than any of the Portland cements used. For slag blended cement, this can be achieved when the replacement percentage is higher than 60%.