高温后长龄期在役混凝土抗压强度研究及微观分析

摘要

In order to study the damage and microscopic variation characteristics of multi‐aged existing concrete after high temperature ,the experiment study on the existing concrete after high temperature was conducted by drill concrete specimens in reinforced concrete (RC) structures with more than twenty years'age .Based on the experiments ,the variation regularities of residual compressive strength of existing concrete after high temperature were proposed and the empirical regression formula was established between residual compressive strength of existing concrete and different temperatures . By using thermogravimetry and stereo scan test , the lithofacies and microstructure of existing concrete after high temperature were analyzed .The study results show that the change of residual compressive strength of existing concrete under different temperatures is similar to the change of fresh placing concrete in laboratory .While the temperature T≤300 ℃ , the residual compressive strength of existing concrete is relative low ;while the temperature T>700 ℃ , the values are higher . The obtained results can provide a referenced basis for appraisement of multi‐aged existing concrete structure after high temperature .%为了研究高温后长龄期在役混凝土损伤及微观变化特征，通过对龄期在20年以上的钢筋混凝土结构取样，进行在役混凝土高温试验，提出高温后在役混凝土残余抗压强度变化规律，建立在役混凝土残余抗压强度与不同温度之间的拟合回归公式，利用热重（T G ）及扫描电镜观察，分析了高温后在役混凝土物相及微观形貌随受火温度的变化情况。研究结果表明：高温后在役混凝土残余抗压强度变化规律与实验室新浇筑混凝土类似，相比而言，当受火温度 T≤300℃时，在役混凝土相对残余抗压强度略低；当 T＞700℃时，在役混凝土相对残余抗压强度较高，所得结论可为实际工程中长龄期在役混凝土结构高温后的损伤评估提供参考依据。