Reinforced Cement Concrete (RCC) is one of the most widely used construction materials because of its strength, durability, and cost-effectiveness. However, exposure to elevated temperatures during fire and other extreme thermal events significantly degrades its structural performance. This review presents a comprehensive assessment of the thermo-structural behaviour and mechanical property degradation of RCC under high-temperature conditions. It discusses the thermal properties of concrete and reinforcing steel, mechanisms of heat transfer, and the development of thermal stresses affecting structural stability. The review examines the deterioration of compressive, tensile, flexural, and bond strengths of concrete, along with reductions in the mechanical properties of reinforcing steel at elevated temperatures. It also analyses the behaviour of RCC beams, columns, slabs, and walls, considering factors such as concrete composition, aggregate type, moisture content, heating conditions, reinforcement ratio, and fibre incorporation. Advanced microstructural characterization techniques, are reviewed to explain the relationship between microstructural damage and mechanical degradation. Furthermore, the paper evaluates experimental methods, numerical modelling approaches, and international fire design standards. Finally, key research gaps and future directions are identified to improve fire-resistant design, post-fire assessment, and the development of durable and sustainable RCC structures under elevated temperature conditions.

Keywords— Reinforced Cement Concrete (RCC); Elevated Temperature; Thermo-Structural Response; Mechanical Property Degradation; Fire Resistance; Residual Strength; Thermal Damage; Structural Fire Engineering