Exploiting Synergistic Effect of Metakaolin and Silica Fume in Production of High Strength Mortar

Metakaolin (MK), which is of higher fineness than cement, is an emerging supplementary cementitious material for the production of high performance concrete. Silica fume (SF), which is of even higher fineness, has been used widely for the production of high strength concrete or ultra-high strength concrete. Very often, either MK or SF is being added to the concrete mix alone. Theoretically, they can also be added together but there are relatively few trials. In this study, the possible synergistic effect of MK and SF on strength of mortar phase of concrete was evaluated. For this purpose, mortar mixes containing varying MK and SF contents at four different water/cementitious materials (W/CM) ratios were prepared and tested. Experimental results show that both MK and SF can improve strength; moreover, the co-addition of MK and SF has synergistic effect in increasing strength over the sole addition of MK or SF at the same cement replacement ratio.