Accelerating Early Strength Development of Concrete Using Metakaolin as an Admixture

Abstract

A study of metakaolin (MK) as an early strength accelerator for Portland cement (PC) and Portland Cement-Pulverised Fuel Ash (PFA) concrete (PC-PFA) has been carried out. This paper reports strength development, particularly at early curing ages, to evaluate the effectiveness of MK as an accelerating admixture. This is supported by analysis of the heat evolution using a calorimeter. The Portland cement concrete covering five different addition levels of MK (1 % – 5 %) to binder and with four water to cement ratios of 0.3, 0.4, 0.5 and 0.6 (0.4 and 0.5 for PC 60 % – PFA 40 % concrete) 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 as an accelerating admixture for PC and PC-PFA concrete.