Tunnel fire resistance of self-compacting concrete coated with SiO2 aerogel cement paste under 2.5 h HC fire loading

Abstract

Self-compacting concrete (SCC) widely used in tunnel structure is prone to spalling when it is subjected to the fire disaster. The fire-resistant materials coated on the surface of concrete are considered as an effective way to prevent concrete from being destroyed in a fire accident. However, current these coatings are difficult to withstand a high temperature, for example, tunnel fire temperature, and a longer-term fire. In this paper, a 40 mm thickness of SiO2 aerogel cement paste (ACP) coating was prepared to investigate the protective effect for SCC in a simulated tunnel fire with the maximum temperature of 1100 °C for 2.5 h. The mechanical properties, thermal conductivity and fire resistance of SiO2 ACP, and the compressive strength of SCC with or without ACP coating in the simulated tunnel fire were tested. The results showed that ACP exhibited excellent mechanical and durable performances and low thermal conductivity. The 40 mm thickness of ACP has a strong thermal insulation capacity and can effectively withstand tunnel fire up to 2.5 h. The SCC samples under the protection of ACP did not undergo compressive strength degradation and destruction of microstructure. The interfacial temperature of ACP and SCC was much lower than the critical value (380 °C) in a 2.5 h tunnel fire. Therefore, ACP can provide a good choice for protection of SCC in a tunnel fire with a high temperature and long time.