Systematic review of physical, mechanical and durability performances of metakaolin concrete

The growing emphasis on environmental sustainability has significantly boosted research into metakaolin (MK)-based concrete as a viable alternative to traditional cement. The incorporation of MK enhances the mechanical and microstructural properties of concrete. Furthermore, it improves specific durability aspects, including chloride resistance, reduced permeability, and increased resistance to acid and alkali attacks. The overall enhancements arise from the small particle size's fill effect, improving packing density, and the pozzolanic reaction that produces additional gels, resulting in stronger and more durable concrete. However, the literature reveals mixed results concerning other durability factors, particularly carbonation resistance, water absorption, and shrinkage behaviour. Previous studies have indicated that a 10 % replacement reduced carbonation depth, and a 15 % MK dosage decreased capillary water absorption. In contrast, other investigations have highlighted potential drawbacks, including an increase in carbonation depth at 10–15 % MK replacement, a substantial dry shrinkage beyond 15 %, and greater water absorption at higher replacement levels. This review paper identifies and outlines research gaps in understanding how the structure of raw kaolinite influences its pozzolanic reactivity, mechanical performance, and durability properties in green concrete. The review paper consolidates key research findings on metakaolin, highlighting its durability properties as a partial replacement for cement, with an optimal level of 10–15 % MK in concrete. • Metakaolin enhances concrete durability, improving chloride resistance and reducing permeability. • Optimal MK replacement (10–15 %) yields better performance, but higher levels may reduce strength. • MK refines concrete microstructure, decreasing pore size and improving ITZ quality. • Conflicting studies on MK effects require further research into long-term durability.