快速冷却引起的热冲击对纤维混凝土高温残余力学性能的影响

【作者】 朋改非； 边松华； 杨学超； 陈茜；

【机构】 北京交通大学土建学院；

【摘要】 本文对纤维混凝土高温后残余力学性能如何受到冷却制度引起的热冲击影响进行了试验研究。混凝土加热到200～800℃的高温,然后经历不同的冷却处理如自然冷却、洒水5～60min 冷却或水中浸泡.温度测定结果表明,水中浸泡或洒水时间不少于30min,将导致混凝土受热冲击作用,其特征是快速冷却,降温速率介于25～44℃/min。与自然冷却相比,这种热冲击作用引起更加严重的混凝土损伤,其残余抗压强度、劈裂抗拉强度和断裂能都有较大降低。洒水时间不短于30min 对混凝土力学性能的影响幅度与水中浸泡相似, 这说明洒水时间不短于30min 与水中浸泡可引起相同程度的热冲击,这与温度测定结果也是完全一致的。当混凝土从800℃高温快速冷却到室温时,混杂纤维(钢纤维和聚丙烯纤维)可提高其残余强度和断裂能。更多还原

【Abstract】 An experimental investigation was conducted on the effect of thermal shock during cooling on residual mechanical properties of fiber concrete exposed to elevated temperatures from 200 ℃ to 800 ℃.Various cooling regimes were used including natural cooling,spraying water for a series of durations from 5 min to 60 min,and quenching in water.The temperature determination results prove that the rapid cooling regimes such as quenching in water,or water spraying for 30 min or more,caused an action of "thermal shock" to concrete under elevated temperature,characterized by a high temperature decreasing rate ranged from 25 min/℃ to 44 min/℃.The experimental results indicate that, compared with natural cooling,thermal shock induced by water quenching and spraying water caused more severe damage to concrete,in terms of greater losses in compressive strength,tensile splitting strength,and fracture energy.The fact that the impact of spraying water for 30 min or more on mechanical properties was almost the same as that of water quenching,indicates that spraying water for 30 min or more could cause thermal shock to a similar degree to water quenching,which is in good agreement with the results of the temperature determination.Hybrid fiber (steel fiber and polypropylene fiber) can enhance residual strength and fracture energy of concrete subjected to thermal shock induced by rapid cooling from high temperatures up to 800 ℃ to room temperature.更多还原