Performance of Pozzolanic Concrete Using Different Mineral Admixtures

Concrete is probably the most extensively used construction material in the world. However, environmental concerns regarding rapid consumption of natural resources and CO2 emission during cement manufacturing process have brought pressure to reduce cement consumption by the use of cement replacement materials (CRMs). The utilization of calcined clay (metakaolin) and silica fume in concrete has received considerable attention in recent years. Brick powder has not got much popularity with respect to strength enhancement but it is effective to reduce drying shrinkage. The following study has been focused to determine the performance of locally available metakaolin, silica fume and brick powder as CRMs in concrete. This study focuses on compressive strength, drying shrinkage and sulfate attack properties of the concrete. Concrete cubes were used for compressive strength determination and mortar prisms for determination of drying-shrinkage and sulfate attack. 5%, 10% and 15% replacement of cement was used for all these three CRMs. Three mixtures with water-binder ratios of 0.63, 0.54 and 0.47 were prepared with a slump of 75-100mm. The sulfate attack was determined by immersing mortar prisms in 2, 5 and 10% solution of magnesium sulfate. The results revealed that silica fume concrete at optimum replacement level of 15% gave highest compressive strength. The lowest drying shrinkage was experienced in case of mortar prisms constituting brick powder. However, very low expansion was observed in SF and MK pastes and also found mutually comparable to each other.