Influence of crumbed rubber inclusion on spalling, microstructure, and mechanical behaviour of UHPC exposed to elevated temperatures

In recent years, the spalling behaviour of ultra-high-performance concrete (UHPC) under elevated temperature conditions has garnered significant attention from researchers worldwide. As a result, various methods have been proposed to mitigate spalling in UHPC under such conditions, including incorporating polymer and steel fibres. Another approach involves using crumb rubber (CR) as a fine aggregate in concrete, which may eliminate spalling when exposed to high temperatures during a fire. However, a systematic study addressing the behaviour of UHPC incorporating CR exposed to high temperatures needs to be included in the literature. To address this gap, this research investigates the spalling behaviour, microstructure, and mechanical properties of UHPC incorporating CR and steel fibres under high elevated temperatures. The findings indicate that CR can effectively reduce the risk of spalling in UHPC. Additionally, the compressive strength of all the five mixes prepared in this study increased when the temperature in the furnace reached 300 °C but decreased when it went to 600 °C. Finally, microstructure analyses were conducted to understand the mixes' spalling and mechanical behaviours with or without CR. This study introduces a new and excellent way of reusing CR from car tyre waste in green construction. By using CR as a fine aggregate in UHPC, spalling can be mitigated, and waste can be effectively reused, contributing to sustainable development. Overall, this research provides valuable insights into the behaviour of UHPC incorporating CR under high elevated temperatures and paves the way for future studies in this area.