单轴压缩下冻结混凝土电阻率变化规律研究  

Study on the Change Law of Resistivity of Frozen Concrete under Uniaxial Compression

作　　者：温维康 付兴府 罗滔 WEN Wei-kang;FU Xing-fu;LUO Tao(Gansu Water Resources and Hydropower Engineering Bureau Co.,Ltd,Lanzhou 730000,Gansu Province,China;College of Water Resources and Architectural Engineering,Northwest A&F University,Yangling 712100,Shaanxi Province,China)

机构地区：[1]甘肃省水利水电工程局有限责任公司,甘肃兰州730000 [2]西北农林科技大学水利与建筑工程学院,陕西杨陵712100

出　　处：《中国农村水利水电》2024年第11期204-209,共6页China Rural Water and Hydropower

基　　金：陕西省青年科技新星项目(2022KJXX-85);陕西省教育厅重点科学研究计划项目(22JS041)。

摘　　要：电阻率是混凝土物理力学性能的重要表征指标。在低温条件下,混凝土的抗拉、抗压与弹性模量与常温环境差异明显,监测冻结混凝土受荷载作用过程电阻率变化,对于混凝土结构的工作状态进行预警和评价具有重要意义。选取饱和含水率混凝土试样在28、-5、-10、-15、-20℃五个温度下进行单轴压缩测试,同步监测试样相对电阻率变化,直至试样破坏。依据混凝土受力变形破坏过程分为压密阶段、弹性变形阶段及裂缝扩展3个阶段。结果表明:①与28℃条件对比,低温环境显著延缓了混凝土试样开裂后达到极限荷载的时间,试样温度为-15、-20℃的荷载-位移曲线后期,裂缝扩展延伸阶段的曲线变缓,试样断裂时加载点的位移增加,其他条件相同情况下,温度越低,试样最终破坏时间变长;②低温环境提高了饱和含水率混凝土试样的峰值强度和弹性模量。温度由-5℃降低至-15℃时,试样的峰值强度和弹性模量均逐渐增大;当温度为-15℃时,峰值强度和弹性模量达到峰值,且弹性模量的增幅高于峰值强度增幅;③单轴压缩情况下饱和含水率混凝土试样在不同阶段,相对电阻率变化各有差异;孔隙压实阶段,相对电阻率随着试验环境温度降低逐渐增大;弹性变形阶段,相对电阻率曲线逐渐由上凸形转为下凹形,其差值逐渐减小;裂缝扩展阶段,相对电阻率突然增大,直至混凝土试样形成贯穿性裂缝而破坏。因此,相对电阻率可作为低温条件下饱和含水率混凝土结构发生临界破坏的预警手段。Resistivity is an important characterization index of physical and mechanical properties of concrete.Under the condition of low temperature,the tensile strength,compressive strength and elastic modulus of concrete are obviously different from those in normal temperature environment.Monitoring the resistivity change of frozen concrete under load is of great significance for early warning and evaluation of the working state of concrete structure.In this paper,the saturated water content concrete samples were selected for uniaxial compression test at five temperatures of 28,-5,-10,-15 and-20℃,and the relative resistivity changes of the samples were monitored simultaneously until the samples were destroyed.According to the deformation and failure process of concrete,it is divided into three stages:compaction stage,elastic deformation stage and crack expansion stage.The results show that:①Compared with the condition of 28℃,the low temperature environment significantly delays the time for the concrete sample to reach the ultimate load after cracking.In the later stage of the load-displacement curve at the temperature of-15 and-20℃,the curve in the crack extension stage becomes slower,and the displacement of the loading point increases when the specimen breaks.Other conditions being the same,the lower the temperature,the longer the final failure time of the specimen.②The low temperature environment improves the peak strength and elastic modulus of saturated water content concrete samples.When the temperature decreases from-5 to-15℃,the peak strength and elastic modulus of the sample increase gradually.When the temperature is-15℃,the peak strength and elastic modulus reach the peak value,and the increase of elastic modulus is higher than that of peak strength.③Under the condition of uniaxial compression,the relative resistivity changes of saturated water content concrete samples at different stages are different.In the pore compaction stage,the relative resistivity gradually increases with the decrease of

关 键 词：单轴压缩 低温环境 相对电阻率 应力比 

分 类 号：TU528[建筑科学—建筑技术科学]