Exploring the Application Potential and Performance of SiO2 Aerogel Mortar in Various Tunnel High-Temperature Environments

Abstract

SiO2 aerogel is a super-insulating material that can be used for tunnel fireproofing to eliminate high-temperature spalling and extend the safe evacuation time of personnel. This study aimed to replace traditional aggregates with SiO2 aerogel in mortar preparation and evaluate its mechanical properties, thermal conductivity, and durability (freeze–thaw, water, and moisture resistance). Furthermore, the high-temperature characteristics of SiO2 aerogel and the damage evolution pattern of SiO2 aerogel mortar were investigated with varying fire durations (0.5, 1, 1.5, 2, 2.5, and 3 h) and fire temperatures (1000, 1100, and 1200 °C) as environmental variables. The results revealed that the critical temperature and critical time of SiO2 aerogel particles from amorphous to crystalline structures were about 1100 °C and 1.5 h, respectively. SiO2 aerogel mortar exhibited a compressive strength of 3.5 MPa, a bond strength of 0.36 MPa, and a thermal conductivity of 0.165 W/m·K. The residual mass ratio and residual compressive strength of SiO2 aerogel mortar were 81% and 1.8 MPa after 1100 °C for 2.5 h. The incorporation of SiO2 aerogel significantly improved the fire resistance of the mortar. Therefore, SiO2 aerogel mortar has the potential to be used as a fireproof coating and can be applied in tunnels to reduce high-temperature spalling and extend the safe evacuation time for personnel.