Selected engineering properties of concrete incorporating slag and metakaolin

The influence of incorporating ground granulated blastfurnace slag (GGBS) and metakaolin (MK) on concrete strength is investigated. Portland cement was partially replaced with 0-80% GGBS and 0-20% MK. The water to cementitious materials ratio was maintained at 0.5 for all mixes. The incorporation of MK causes an increase in strength, especially during the early ages of curing. However, the use of GGBS in concrete reduces the strength during the first 28 days. Beyond 28 days, the strength increases with the presence of GGBS up to 60% replacement. The decrease in compressive strength during the early ages of curing of GGBS concrete is compensated by the inclusion of MK. The presence of MK in concrete containing GGBS does not cause a decrease in the long-term strength.