Enhancing the performance of concrete after exposure to high temperature by coarse and fine waste fire brick: An experimental study

Exposure to high temperatures is one of the most important processes of deterioration in concrete structures during their service life. Because high temperatures cause adverse effects on the mechanical and physical properties of concrete, it is necessary to improve these properties when concrete is exposed to high temperatures. Thus, this study implemented an experimental program to assess the effect of coarse and fine recycled Fire Brick Aggregate (FBA) on the physical and mechanical properties of concrete subjected to high temperature. In this context, Fire Brick Concrete (FBC) mixtures with three water/cement ratios (w/c of 0.59, 0.48 and 0.38) made by replacing 20 % of coarse and fine Natural Aggregates (NA) by FBA were subjected to different temperatures: 20 degrees C (room temperature), 150 degrees C, 250 degrees C, 400 degrees C, 600 degrees C and 800 degrees C. After cooling down to room temperature, FBC produced were compared with conventional concretes made with 100 % of coarse and fine NA (with an equal w/c ratio) in terms of physical and mechanical properties including mass loss, water absorption, porosity, density, Ultrasonic Pulse Velocity (UPV), damage degree, change of volume, compressive strength and dynamic modulus of elasticity. Furthermore, the evolution of crack width of concrete specimens after exposure to high temperatures was investigated by microscopic. Based on the experimental work undertaken, the following conclusion are drawn: (1) the incorporation of FBA at 20 % to replace coarse and fine NA is recommended for use in concrete production at ambient temperature;(2) coarse and fine FBA were more efficient for improving the mechanical and physical properties of concrete after exposure to high temperatures.