Effect of silica fume on the fresh and hardened properties of high performance concrete

Abstract

The objective of this study is to investigate the effects of silica fume on the fresh and hardened properties of high performance concrete (HPC). To perform such a study several HPC mixtures are prepared with various silica fume percentages (0 to 15 % by weight of cement, as addition). Fresh properties such as unit weight, slump and air content and hardened properties such as compressive strength, splitting tensile strength, ultrasonic pulse velocity and schmidt hammer are determined by a standard laboratory testing program. The addition of 5 % silica fume to HPC mixes decreased the fresh unit weight when compared with the unit weight of the control mixes. Air content tests showed that the increased silica fume content causes an increase in the entrapped air of the concrete mixes in the fresh state. Silica fume addition improved the splitting tensile strength and compressive strength test results. The tests showed that ultrasonic pulse velocity may have a relationship with concrete density. Keywords: High performance concrete, silica fume, unit weight, Schmidt hammer, splitting tensile strength.