Behaviour of gneiss and basalt aggregate in normal concrete subjected to high temperatures

This work aims at analyzing the high temperature behaviour of normal concrete containing quarry aggregates commonly used in Cameroon. Gneiss aggregate concrete (C-SG-GG) and basalt aggregate concrete (C-SB-GB) were formulated. Specimens were subjected to different heating–cooling cycles of 150, 300, 450 and 600 °C at a low heating rate of 1 °C/min to obtain the residual properties; and a faster heating rate of 10 °C/min up to 600 °C to study the thermal sensitivity. The thermal expansion coefficient, physical (porosity and permeability) and residual mechanical (compressive strength, tensile strength and elastic modulus) properties of the concrete samples were analyzed. At room temperature, the concrete formulations studied showed comparable mechanical properties due to the similar fluid consistency and workability of their mixes. Gneiss aggregate concrete exhibited a permeability lower than that of basalt aggregate concretes. Measurements of the thermal expansion coefficients of gneiss and basalt aggregate concretes are 0.14.10−4/°C and 9.5.10−4/°C, respectively, suggesting that the pressure exerted by increasing temperature on basalt concretes is greater. The thermal expansion coefficient of basalt concrete is much lower than that of gneiss concrete. Compared to basalt concrete, the residual compressive strength of gneiss concrete increased when temperatures increased from 150 to 300 °C. This study showed the gneiss aggregate concrete had better residual mechanical properties than the basalt aggregate concrete.