Studying the effect of low reactivity metakaolin on free and restrained shrinkage of high performance concrete

Abstract

Producing high performance concrete with a low reactivity pozzolan such as metakaolin is challenging. On the other hand, high performance concretes could be more prone to shrinkage cracking due to their higher cement content. No consensus exists in the literature on how metakaolin affects concrete's shrinkage. In this study, the possibility of making high performance concrete with a low reactivity metakaolin was assessed. Moreover, the effect of using a low reactivity metakaolin on the mechanical properties, durability, and free and restrained shrinkage of high performance concrete was evaluated. The results showed that increase in the percentage of metakaolin replacement led to reduction in the mechanical properties and durability of high performance concrete. The effect of metakaolin on shrinkage of high performance concrete was observed to be dependent on the water to cement ratio. Overall, it is possible to produce high performance concrete with a low reactivity metakaolin (up to 20% replacement level) only at low water to cement ratios.