Experimental Analysis of Cooling Effects on Mechanical Properties of Steel for Reinforced Concrete After High-Temperature Exposure

Abstract

This article examines the mechanical properties of hot rolled FeE500-3 steels, used for reinforced concrete, with a nominal yield strength of 500 MPa. These steels are intended for the manufacture of beams, columns, and composite slabs made of reinforced concrete. This analysis is centered on small diameter ribbed bars (6 mm, 8 mm, and 10 mm) massively used for residential construction projects. It includes tensile tests carried out on specimens cooled to ambient temperature after a heating cycle at several temperature levels from 300 °C to 900 °C. Two cooling methods are studied to assess their influence on the residual mechanical properties of the steel material (elastic strength, ultimate strength, Young's modulus, strain at yield point, strain at the ultimate point, and strain at failure). The results have showed that the reinforcements cooled by air lose approximately 30% of their resistance from 700 °C and 20% in the case of cooling by water. The type of cooling has a negligible effect on the Young module. Ductility is the most impacted mechanical property. Significant degradation of ultimate strain and strain at failure has been noted for bars heated beyond 600 °C and cooled by water. However, ductility has improved for natural air cooling. Curves and predicted equations of the main residual mechanical properties of hot-rolled FeE500-3 steel are presented in this study. They can be used to rehabilitate damaged buildings and improve their safety.