Density Dependence of Tunnel Fire Resistance for Aerogel-Cement Mortar Coatings

Five kinds of mortars with density grades of 500, 600, 700, 800, and 900 kg/m 3 were prepared. Their thermal conductivity and compressive strength were measured, and the morphological changes before and after simulated tunnel fire were observed. To investigate the fire resistance, the interfacial temperature of a 30 mm thick aerogel-cement mortar and self-compacting concrete (SCC) in a simulated tunnel fire with the maximum temperature of 1 100 °C for 2.5 h was tested and recorded. The results showed that as the density decreased, both compressive strength and thermal conductivity of the aerogel-cement mortar exhibited an exponential decrease. The effective fire resistance time of the mortar with 500, 600, 700, 800, and 900 kg/m 3 for protecting SCC from tunnel fire were 97 min, 114 min, 144 min, > 150 min, 136 min, respectively. 700–800 kg/m 3 was the optimum density for engineering application of tunnel concrete fireproof coating.