气凝胶复合SCC隧道火灾剥落与强度退化研究

Spalling and Strength Degradation of Aerogel Mortar Protected Self-Compacting Concrete Exposed to Tunnel Fire

开发了硅气凝胶砂浆,用以保护和防止自密实混凝土(SCC)在模拟隧道火灾条件下(1 200℃)发生爆裂剥落。首先在气凝胶体积掺量为骨料(气凝胶+砂)体积的60%条件下制备出具有防火涂层潜力的砂浆,然后采用Eurocodes HC火灾升温曲线(目标温度1 200℃)和喷淋与自然冷却2种灭火方式,对C40复合(涂层厚度为1~15mm)与非复合自密实混凝土(未涂层)火灾爆裂剥落与强度退化性能进行对比研究,建立了爆裂剥落时长、强度折减系数与气凝胶涂层厚度之间的关系。结果表明,隧道火灾下,非复合自密实混凝土爆裂剥落时长为107min,而复合自密实混凝土爆裂剥落时长均延长13~93min,爆裂剥落时长与气凝胶涂层厚度呈二次抛物线关系;自然冷却与喷淋冷却灭火方式下,非复合自密实混凝土强度折减系数为47.7%与29.3%,当涂层厚度为15mm时,复合自密实混凝土强度折减系数为96.5%与82.6%,随涂层厚度增大,强度折减系数分别呈二次抛物线与线性增长。

Silica aerogel based mortar was developed with a purpose to protect self-compacting concrete（SCC）from an explosion to high temperature atmosphere（1 200℃）,which was experimentally simulated to a tunnel fire condition.With a protection of such silica aerogel motar,the explosive spalling and strength degradation of self-compacting concrete（SCC）were systematically evaluated.For the preparation of aerogel mortar,the granular silica aerogel was regarded as one portion of aggregates,which is about 60% of the total aggregate volume（aerogel＋sand）,the mortar was then used as insulation layer and decorated on the surface of C40 self-compacting concrete with the thickness of 1-15 mm.The specimens with or without aerogel mortar protection were heated up to 1 200℃ following the Eurocodes HC time-temperature curve until an explosively spalling occurred,and then the samples were cooled down in following 2 routes：natural cooling and spray cooling.The results show that the spalling happened at 107 min for SCC specimen without any protection.In contrast,with an aerogel mortar protection,the spalling was extended by 13 to 93 min,the thickness of the mortar and the spalling time follows a quadratic parabolic equation.Cooling under natural or spray forced conditions,the compressive strength reduction coefficients of the non-composite SCC specimen are 47.7% and 29.3% while the one with 15 mm mortar protection are 96.5% and 82.6%.With an increase of coating thickness,the compressive strength reduction coefficients of the SCC specimen under natural cooling and spray forced cooling follow quadratic parabola and linear relations respectively.