From waste product to metakaolin : beneficial impact on performance parameters

Abstract

Both extensive literature and practical experience have shown that a partial replacement of Portland cement with pozzolanic additions may substantially improve the general durability properties of concrete, while simultaneously contribute to the sustainability of construction industry. The possibility of producing concrete with enhanced durability performance, including locally produced materials such as metakaolin is studied. The effect that metakaolin has is assessed by comparing the mechanical and durability performance of a concrete with metakaolin additions with without. The total binder used (300 kg/m3) is composed of metakaolin and fly ash in percentages up to 30%, resulting in concrete with significant compressive strength and enhanced durability performance. The durability of the studied compositions was evaluated by the absorption of water into concrete under capillary and under immersion action, the non steady state chloride migration tests and four-point electrode resistivity measurements. Based on the test results obtained, of the various concretes tested, the results demonstrate the beneficial effect of metakaolin addition to improve the concrete durability, namely the resistance against chloride penetration. Test results demonstrate that the use of metakaolin does not seem to affect long term strength gain when compared to ordinary Portland cement.