Evolution of thermal conductivity on CAC concrete at high temperatures and during thermal fatigue tests

Abstract

Heat transfer plays an important role when concrete works at high temperatures. For many applications, it is important to evaluate the effect of heat transfer on concrete to predict the thermo-mechanical response. Inside concrete, the dominant mechanism of heat transfer is conduction, and the main parameter involved is thermal conductivity. Heat transfer may play also a relevant role when spalling occurs. In this paper, the evolution of thermal conductivity of concrete with temperature has been studied for different concrete types up to 600ºC. The effect of cooling and thermal gradients are followed. Results indicate that during the first heating, thermal conductivity decreases in several steps with temperature, first due to pore free water loss and second after dehydration up to 300ºC. The mass loss and the temperature gradients are also affected. Thermal gradients play a role in the risk of concrete spalling. When cooling, thermal conductivity recovered almost the same value at 300°C. Repetitive thermal cycles do not modify the thermal performance of concrete.