Thermal conductivity and shrinkage properties of slag-based cement concretes

Abstract

The thermal conductivity, specific heat, and total drying shrinkage test of slag blended OPC cement is conducted by using a Hotdisk-2500S thermal conductivity, and non-contact shrinkage deformation measurement apparatus based on ISO 22007-2 and GB/T50082-2009 test standards, respectively. The influence of replacement rates of slag cement (0, 30, 50, and 70%) and high-temperature exposure (21, 200, 400, 600, and 800 °C) on the thermal properties of concrete is analysed. The results show that for all three concretes, the thermal conductivity initially decreases with increasing temperature up to 400 °C, then after it remains almost constant between 400 and 600 °C, and gradually begins to decrease again up to 800 °C. Furthermore, thermal diffusivity of concrete group G-70, shows 21.4, 21.6, and 37.6% increment in 21, 200, and 600 °C temperature exposure respectively compared to concrete group G-0. Though, as the exposure temperature keeps rise to 800 °C, its value starts to decrease. Furthermore, the results indicated that high volume slag cement content in the concrete mix lessen the drying shrinkage of the concrete at later age. Test data is used as a function of temperature and slag replacement to establish high temperature relations for thermal properties. The proposed thermal property relationships can be used as input data for validation in computer programs and to evaluate the response of OPC and slag blended Portland cement concrete structures subjected to fire.