Fracture Energy and Mechanical Properties of Concrete Incorporated with Recycled Coarse Concrete Aggregate Exposed to High Temperatures

Little research studied using recycled aggregate from demolished burned structures or buildings exposed to fire effect after the liberation war of Mosul city in Iraq. This research examined the concrete made from recycled concrete aggregate subjected to two intense heating temperatures (250 and 500)degrees C to investigate the influence of heated recycled aggregate on concrete's performance and fracture energy. Two replacement levels of heated recycled aggregate (35 and 75)% by the volume of the normal aggregate were selected to carry out the tests. The study found that the heated recycled aggregate negatively affected concrete's fresh and hardened properties. With the increase of the aggregate replacement ratios and heating temperature, concrete's compressive and splitting tensile test responses showed a high reduction compared to the reference. Promisingly, the results show a slight effect on the fracture energy of concrete for varying replacement and heating levels. For a 35% replacement at 250 degrees C, the reduction was 12%, while for higher replacement levels (M3, M4, and M5), the reduction ranged from 25% to 28%. This indicates the dependence of the concrete crack propagation on the bond strength at the interface between aggregate particles and cement paste.