Residual strength of steel fibre reinforced rubberised UHPC under elevated temperatures

Ultra-high-performance concrete (UHPC), known for its exceptional mechanical properties, sustainability, and durability, has carved a niche for itself in the construction industry. However, its performance under elevated temperatures is a major concern due to its compact microstructure and low permeability. A promising resolution emerges in the form of crumb rubber (CR), which, when utilised as a fine aggregate, can reduce the issue of explosive spalling under rapid temperature elevation. Nevertheless, the strength of concrete could be compromised when CR substitutes traditional aggregates. To offset this, steel fibres can be added, contributing significantly to tensile and flexural strength, toughness, and ductility. Addressing the dearth of research in this area, an experimental investigation was undertaken to illuminate the effectiveness of using steel fibres and CR to enhance UHPC's spalling resistance and mechanical properties at high temperatures. Through various tests conducted on UHPC specimens, with and without CR and steel fibres, at elevated temperatures and various exposure times, this study has evidenced a notable reduction in spalling risk and complexity in mechanical property evolution with temperature and heating duration. Ultimately, this research highlights the potential of rubberised, steel fibrereinforced UHPC to improve spalling resistance and residual mechanical properties significantly, broadening its scope in construction applications.