Influence of Fire on the Component and Performance for the Concrete of Reinforced Concrete Beams

This paper adopts experimental methods to investigate the component and microstructure of the concrete slab in reinforced concrete (RC) bridges after fire hazards, and the obtained results show that the com ponent and microstructure of concrete slabs will change significantly after fire hazards. Specifically, after the RC beams undergo a fire in low temperature (lower than 400°C), since the structure of cement stone in concrete is relatively compact, the fire product transforms from compact hydrated calcium silicate to island-like calcium silicate, leading the structure to become loose. After the RC beams undergo a fire in high temperature (higher than 400°C), the decomposition of the crystal inside the concrete causes large number of cracks and voids inside the structure, leading to the microscopic damage and decrease in strength of concrete. This paper preliminarily reveals the damage mechanism of RC bridges after fire hazards through the experimental study. It lays a theoretical foundation for the research of bridges’ performance deterioration.