Long term durability properties of concrete modified with metakaolin and polymer admixture

•A review on the principles using metakaolin and polymer to improve concrete properties.•Long-term mechanical and durable properties of concrete using both metakaolin and polymer.•The optimum mix and the complement mechanisms using both metakaolin and polymer.•A guidance for concrete design for the application in severe environmental conditions. Previous studies show that both metakaolin (MK) and polymer can respectively improve certain mechanical and durability properties of concrete. Also, recent studies show that a combination of MK and polymer further enhances the mechanical properties by complement of each other. However, the knowledge of the effect on durability, a critical governing factor of concrete for the applications in extreme environments such as sewage, off-shore and bridge structures, has not been well established yet. This paper reports on a comprehensive study of the effect of metakaolin as a supplementary cementitious material together with polymer as admixture on the durability of concrete at relatively old ages. The results confirm that replacing Portland cement with 15% metakaolin and an additional 5% polymer (by weight) provide the optimum improvement for Portland cement concrete on both mechanical properties and durability.