Effects of Cooling Methods on the Properties of Concrete with Metakaolin after Thermal Exposure

Abstract

Abstract Metakaolin (MK) have been used in concrete as supplementary cementitious materials (SCMs) due to their economic and environmental benefits. Consequently, the use of MK in concrete production contributes to the overall reduction of CO2 release in the environment. However, for a sustainable built environment, material resistance to thermal exposure is of concern. Previous research have studied the performance of MK at elevated temperature, but there is little or no literature on the effect of cooling methods on concrete structures with MK subjected to varying temperature. Hence, this research investigates the effects of cooling methods on the properties of concrete incorporating MK after thermal treatment (fire). Raw MK was calcined, ground and analyzed using XRD and XRF. 15%MK were used to replace cement. Concrete properties (crushing resistance, density, compressive strength) for water and air cooling methods were determined and compared to a control pure concrete. The heating temperatures were 200°C, 350 °C, 550 °C and 750 °C respectively. The incorporation of MK improved properties of the hardened concrete. Charts and tables showing the effects of MK on the concrete properties investigated were presented. The minimum strength obtained was 28.09 N/mm2 during water cooling and maximum strength 35.20N/mm2 during air cooling. The most enhancing effect of Mk as a replacement material was observed in all the cooling methods considered. Water cooling method was found to have caused severe strength reduction in the concrete structure. MK concrete performs better than pure concrete under aircooling method after thermal exposure, hence, can be adopted for fire aggressive environment.