STRENGTH AND DURABILITY OF CONCRETE INCORPORATING METAKAOLIN AND FLY ASH

This paper examines the strength and durability of concrete made with ternary metakaolin (MK) - fly ash (FA) - Portland cement (PC) binders. A range of water to binder ratios was employed and the properties reported in this paper were compressive strength development, and chloride ingress. This paper presents strength development, particularly at early curing ages, to evaluate the effectiveness of MK as an accelerating admixture. The Portland cement concrete covering five different addition levels of MK (1%, 2%, 3%, 4% and 5%) to binder and with water to cement ratios of 0.5 were cured in water up to 28 days. The compressive strengths were evaluated at 1, 3, 7, 14 and 28 days. The compressive strength development of the concrete at various curing times is compared with control concrete (PC only). It is found that MK contributes significantly to early strength development for PC concrete. It is found that the contrasting influences on the strength, particularly at early curing times, affected by FA and MK, when used in isolation as blends for cement, can be combined effectively by the employment of various compositions of MK and FA. The results establish that improved performance can be achieved by using particular combinations of the different binders. Tentative guidelines for PC-MK-FA mix design are recommended. In ternary PC-FA-MK blends, MK has a significant beneficial effect on both the chloride concentration and the penetration depth.