Mechanical properties and microstructures of steel-reinforced rebar exposed to heat

Abstract. Reinforced steel rebars are well known for their unique properties that give the concrete its strength and durability. Concrete is one of the most composite materials that have been used in the world. Most of the buildings in the Middle East are made using reinforced concrete. The harsh, dry, and hot weather conditions in the region might cause incidents such as fire. To understand the effect of elevated temperature on the building structure and integrity, it is essential to study the impact of heat on the properties of reinforced steel rebars. Fire can effectively change the properties of steel rebars in many ways. Moreover, the cooling process of the fire is important to recognize due to the effect of cooling on the microstructural modification of the steel rebars. In the big picture, each cooling process scenario must be designed and explored. For this study, the focus is to investigate the effect of heat on the reinforced steel rebar once it has been cooled naturally. Besides the control sample, four different heat scenarios were studied. Namely, the as-received rebars have experienced heat values of 300℃, 500℃, 700℃, and 900℃ by employing a muffle furnace. The selected heat profile was chosen to simulate scenarios with low, moderate, and high temperatures. The tensile properties of the reinforced rebars subjected to heat have changed dramatically. The yield stress and the ultimate tensile strength decreased with the increment of the temperature, whereas the elongation increased, reaching almost double the value of the control sample. Likewise, the microstructures of those steel rebars have been altered as a result of heat exposure.