冻结作用下复合填料水分迁移与冻胀特性研究

Abstract

A laboratory study was carried out to investigate the heat-moisture transfer and frost heave characteristics of a composite geofoam under artificial frost action. The geofoam was composed of expanded polystyrene (EPS) beads, waste foundry sand, water and cement in proportions. Thermal gradients were loaded through the geofoam by maintaining the temperature of -5 ⁰C, -10 ⁰C or -15 ⁰C at the top and 10 ⁰C at the bottom of cylindrical samples. Test results showed that, with the increase of EPS beads, the thermo-physical properties of the geofoam were favorably improved, i.e., thermal resistance increased, freezing rate and depth decreased. The addition of EPS bead also led to the reduction of frost heave, which helped mitigate freeze-thaw impact on the geofoam. EPS bead content of 0.5%-1.0% was considered as a favorable range, which enhanced the anti-frost performance of the composite geofoam. The anti-frost performance of the geofoam was related to the thermal isolation, hydrophobic and mechanical buffering behavior of the EPS beads. = 在补水条件下,对4种聚苯乙烯(EPS)颗粒掺量的复合填料试样施加3种冷端温度(-5,-10,-15℃)冻结,开展水分迁移及冻胀特性测试与分析.研究了冻结作用下复合填料温度分布特征、水分迁移规律和冻胀变形特性,基于温度场和水分场的相关性分析了复合填料抗冻胀破坏机理.结果表明,一定程度地增加EPS颗粒含量,会使复合填料冻结温度与热阻提高,温度传导、冻结锋面移动速率以及冻结深度递减,已冻区含水率增量变小,冻结锋面和未冻区含水率增量变大,冻胀量减少,有助于缓解冻胀破坏.EPS颗粒掺量为0.5％～1.0％(质量分数)时,复合填料抗冻胀性能较好.抗冻胀机制与EPS颗粒的隔热、阻水和吸纳作用有关.