Effects of Metakaolin as a Pozzolanic Material on Chloride Ingress in Concrete

Abstract

The use of supplementary cementitious materials as cement partial replacement has emerged as a successful strategy in producing green, less energy-intensive and environmentally friendly concrete. This study investigates the effects of metakaolin as a pozzolanic material on chloride ingress in concrete. Cement was partially replaced with metakaolin at 5, 10, 15 and 20%, using a mix ratio of 1:2:4 and a water-cement ratio of 0.5. Density, Compressive strength, flexural strength, water absorption and abrasion resistance tests were carried out. Metakaolin is a filler material in concrete and improves concrete's strength and functional performance. The maximum compressive strength at 28 days was the control, which achieved 28.9, 27.6 and 26.6 N/mm²; and that of flexural strength achieved 4.37, 4.22 and 3.97 N/mm² for concrete cured in H₂O, NaCl and HCl medium respectively. At later stages of 56 and 90 days, concrete produced with metakaolin at 5 and 10% cement replacement gave better strength. The findings show that metakaolin improves concrete's water absorption and abrasion resistance. Chloride significantly affects the performance of concrete. HCl is more deleterious to concrete than NaCl. In conclusion, metakaolin is suitable as a pozzolan in the production of concrete; its usage at a lower volume of cement replacement will help reduce cement utilization in concrete production, thereby reducing the global warming contributed by the exploration and production of cement. 10% Metakaolin (MTK) is the optimum percentage in concrete which is recommended to produce strong, dense, and durable concrete.