火灾环境下热-冷循环作用对混凝土性能的影响研究

为了研究混凝土材料的结构与力学特征受火灾热-冷作用的影响规律,通过测量不同热-冷作用次数下的试样质量和密度损失率定量表征了混凝土结构损伤程度;通过开展单轴压缩实验对热-冷作用对其力学行为的变化规律进行了研究;最后进行XRD衍射实验和SEM扫描电子显微镜对混凝土的成分与微观结构进行探测.实验结果表明:在火灾热-冷作用下,...

Influence of heat-cold cycling on concrete in fire environments

This work aimed to study the heat-cold cycling effects on the mechanical and damage characteristics of concrete materials. The damage degree of the concrete structure was investigated by measuring the sample mass under different heat-cold cycles. The mechanical behavior of heat-cold cycling effects was studied by an unconfined compression test. The XRD diffraction test and SEM scanning electron microscope were used to detect the mineral composition and microstructure of concrete. The results show that the process of heat-cold cycling deepens the erosion degree of concrete samples continuously. The mass-loss rate and density change rate of concrete increase due to the gradual peeling and reduction of cement gel. The strength indexes of concrete-uniaxial compressive strength and elastic modulus gradually attenuated with the increase of cycles, and the decay rate was first faster and then slower, while the curve of deformation performance indexes-peak strain and elastic modulus-cycles showed an anti-symmetric distribution. According to the results of XRD diffraction experiments, it is inferred that the heat-cold cycling effect on concrete is mainly due to the thermal expansion effects in the cement gel. It was observed by SEM tests that the cement gel of concrete was continuously lost in the process of thermal reactions, and the crack scale was continuously enlarged so that the structural integrity and mechanical properties of concrete were decaying in the heat-cold cycling process.