摘要
混凝土试件成型后分别标养3、7 d,然后从养护室取出置于-20℃环境中至28 d以产生不同程度的低温初始缺陷,采用弹性波波速对混凝土低温初始缺陷进行定量判别,并应用压汞试验、核磁共振与扫描电镜对混凝土砂浆基体进行微观分析。结果表明:基于弹性波波速计算得到的初始损伤度可用于定量判别混凝土低温初始缺陷,仅标养3 d(LD-3)、7 d(LD-7)混凝土试件的初始损伤度分别为0.22与0.12;压汞试验显示,LD-3与LD-7系列试件有害多害孔含量分别为92.7%与87.2%,临界孔径分别为0.8μm与0.9μm,明显高于标养28 d混凝土试件(有害多害孔含量、临界孔径分别为83.8%与0.18μm),核磁共振得出的混凝土临界孔径与压汞试验类似。扫描电镜图像显示,含低温初始缺陷混凝土的水化程度较低,基体结构松散。混凝土低温初始缺陷可以由初始损伤度(弹性波波速)、有害多害孔含量与临界孔径进行定量判别。
Initial defects of different extends are generated by storing concrete specimens under-20 ℃ to age 28 d after being standardly cured for 3 d(LD-3)/7 d(LD-7),respectively. Elastic wave velocity was used to quantify the low temperature initial defects. Furthermore,microstructural analysis was carried out by mercury intrusion porosimeter(MIP),nuclear magnetic resonance(NMR) and scanning electron microscopy(SEM). Results show that the initial damage extent calculated by elastic wave velocity can be used to quantify the initial defects caused by low temperature and the initial damage extents in the concrete specimens LD-3 and LD-7 are 0.22 and 0.12,respectively. The MIP results show that the volume content of the harmful pores and more harmful pores in LD-3 and LD-7 series are 87.2% and 92.7%,and the critical pore diameters are 0.9 μm and 0.8 μm,respectively,while the content of the harmful pores and more harmful pores and the critical pore diameter of concrete specimens standardly cured for 28 d are 83.8% and 0.18 μm. Furthermore,the critical pore diameters of the three series of concrete specimens obtained from NMR are similar to those from MIP. SEM microscopic images indicate that exposed to low temperature at early age,the microstructure in concrete is porous and the hydration extent of the cementations materials is low. Initial defects caused by low temperature curing can be quantified by initial damage extent(elastic wave velocity),volume content of the harmful pores and more harmful pores as well as critical pore diameter.
作者
郝伟男
李曙光
计涛
陈改新
卿龙邦
HAO Weinan;LI Shuguang;JI Tao;CHEN Gaixin;QING Longbang(School Civil Engineering and Transportation,Hebei University of Technology,Tianjin 300401,China;State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin,China Institute of Water Resources and Hydropower Research,Beijing 100038,China)
出处
《中国水利水电科学研究院学报》
北大核心
2019年第5期394-399,共6页
Journal of China Institute of Water Resources and Hydropower Research
基金
国家重点研发计划项目(2016YFB0303601)
国家自然科学基金项目(51409284)
流域水循环模拟与调控国家重点实验室课题(2016TS10,SKL2017CG05)
中国水科院课题(SM0145B842017)
关键词
混凝土
初始低温
初始缺陷
定量判别
微观分析
concrete
low temperature
initial defect
quantitative analysis
microstructural