Effect of moisture content on tunnel fire resistance of self-compacting concrete coated with aerogel mortar

Abstract

Self-compacting concrete (SCC) are widely used in tunnel linings that are subjected to the risks of fire accident. During tunnel fire, personnel and structural safety are commonly threatened by explosive spalling of SCC due to high strength and high moisture content of SCC. Recent studies have suggested that coating layer of fire-resistant material can efficiently prevent SCC from spalling in tunnel fire. In this study, SCC samples coated with 6 mm SiO₂ aerogel-cement mortar (SiO₂-ACM) were prepared in comparison with those without coating. The effects of different moisture contents (0%, 25%, 50%, 75%, and 100%) on the fire resistance of SCC were investigated. The results show that SiO₂-ACM exhibited excellent mechanical and durable performances and low thermal conductivity. During the exposure to the mimetic tunnel fire, the degree of spalling of SCC increased as moisture content increased. The SCC samples with SiO₂-ACM coating exhibited much less spalling than those without coating. After mimetic tunnel fire, bare SCC had almost completely failed in compressive strength, whereas residual compressive strength of SCC coated with SiO₂-ACM were more than 68.6% even SCC with 100% of moisture content. Therefore, SiO₂-ACM coating provides an attractive avenue to enhance the behavior of SCC in tunnel fire.