The global scientific research circle and government agencies face a number of serious environmental challenges, one of which is the recycling of “End of Life Tires” (ELT). An estimation of one billion tires is expected to end their useful life annually, of which only roughly 50% are recycled at the moment, with the remainder ending up in landfills. Consequently, to solve this gap in the ELT's utilization rate, it is imperative to enhance the current application and furthermore create new applications for recycled tire materials. One of such areas that is currently being investigated is the introduction of waste tire into concrete as partial replacement of natural aggregates in concrete production. This experimental study investigated the influence of elevated temperatures on the mechanical properties of M25 grade concrete, specifically its compressive strength, split tensile strength, and flexural strength. The study focused on the effect of incorporating crumb rubber as a partial replacement of fine aggregate at varying percentages 5%, 10%, 15%, and 20% along with a constant 2% of corrugated round steel fibers. After a standard 28 days water curing period, concrete specimens were subjected to a range of elevated temperatures 2000C, 4000C, 6000C, and 8000C, to simulate fire-like conditions. The results of the study revealed a significant and consistent reduction in all three mechanical properties as the exposure temperature increased, which is a common characteristic of concrete under thermal stress. However, the performance varied notably among the different mixes. For compressive and flexural strength, the concrete mix with 10% crumb rubber (CR) demonstrated superior performance, consistently retaining the highest residual strengths at higher temperatures compared to all other mixes. This finding suggests that a 10% replacement level strikes an optimal balance, where the crumb rubber helps to relieve internal thermal stresses through its melting and decomposition, while the steel fibers provide crucial internal reinforcement to prevent catastrophic failure. In contrast, the split tensile strength tests showed a different trend. The mix with 5% crumb rubber exhibited the best performance at all temperatures. This indicates that while the steel fibers effectively bridged cracks and enhanced tensile properties, higher percentages of crumb rubber led to a greater number of weak bonds within the concrete matrix, which negatively impacted its tensile strength. The study concludes that the strategic incorporation of crumb rubber and steel fibers can enhance the thermal performance of concrete, but the optimal percentage of crumb rubber is dependent on the specific mechanical property being optimized. The findings also led to recommendations for preventive measures against fire damage in concrete, such as the use of fire-resistant mixes, application of protective coatings, and ensuring adequate concrete cover over reinforcement.
Jadhav Amol Shivaji (Thu,) studied this question.