Experimental investigation on the microstructure and physical properties of natural, recycled fire brick and lightweight aggregates after exposure to high temperature

The performance of concrete at elevated temperatures is strongly influenced by the nature of the aggregates used. For this reason, it is advantageous to identify the evolution of physical properties of aggregates from room temperature to high temperature. In this experimental research, the effect of elevated temperature on the physical properties of different aggregates nature used to produce concrete was studied. Nine aggregate types with different natures were studied in three separate groups: natural aggregates, fire brick aggregates and lightweight aggregates. All studied aggregate samples were heated to different temperatures from 100 to 900 °C with a heating rate of 10 °C/min. The aggregate characteristics; namely mass loss, water absorption coefficient, water porosity and density were investigated before and after exposure to high temperatures. Furthermore, the aggregates microstructure after exposure to high temperatures was studied by scanning electron microscopy. The obtained results show that, exposed to high temperature, the fire brick and lightweight aggregates perform better compared to natural aggregates.