A review on mechanical properties and durability of recycled coarse aggregate concrete exposed to elevated temperatures

Replacing natural aggregates with recycled concrete aggregates in concrete provides a dual benefit by reducing natural resource consumption and minimizing land use for waste disposal. Research has shown that recycled aggregate concrete (RAC) with optimized mix proportions can perform comparably to natural aggregate concrete (NAC) at ambient temperature and is already used in various applications. However, its broader adoption may be limited by uncertainties surrounding its performance under extreme conditions, particularly fire or high temperatures. This paper provides a comprehensive review of studies on the behavior of coarse RCA concrete exposed to elevated temperatures. It examines the degradation mechanisms of concrete exposed to elevated temperatures, presents experimental findings on the mechanical properties and durability of coarse RCA concrete, analyzes the influence of internal material and external environmental factors on its fire behavior, and discusses potential strategies to enhance its fire performance. Additionally, the paper identifies key knowledge gaps and suggests directions for future research. The review concludes that RAC generally deteriorates with increasing temperatures, while inconsistent findings regarding the effects of influencing factors on the fire performance and contradictory results on relative compressive strength at and after fire exposure persist. This study offers valuable insights for researchers and practitioners, promoting a deeper understanding of fire behavior in RAC and paving the way for the development of fire-resistant RCA concrete to safeguard lives and property.