摘要
为探讨高强高性能混凝土高温爆裂机制,对掺与不掺聚丙烯纤维的C80高性能混凝土在20~800℃温度段内的线膨胀系数、热膨胀率和微分线膨胀系数进行研究,基于CT扫描技术,分析不同温度下C80高性能混凝土微结构变化,研究热膨胀性能变化规律机理。结果表明:随着温度升高,混凝土线膨胀系数和热膨胀率总体呈上升趋势,微分线膨胀系数在560℃之前小幅波动;降温过程中,混凝土线膨胀系数总体呈上升趋势,热膨胀率总体呈下降趋势,除个别温度点外微分线膨胀系数较为稳定;掺0.2%聚丙烯纤维混凝土的线膨胀系数、热膨胀率和微分线膨胀系数总体均较素混凝土小,表明掺入聚丙烯纤维可以减小混凝土的热膨胀。CT试验表明,掺0.2%聚丙烯纤维混凝土的内部缺陷率均小于素混凝土,相对缺陷率均大于素混凝土,说明掺聚丙烯纤维增加了高温下孔隙连通性和内部蒸汽压逃逸的途径,可有效改善高强高性能混凝土的高温性能。
In order to study the mechanism bursting of high strength and high performance concrete at high temperature, the line-ar expansion coefficient, expansion rate and differential linear expansion coefficient of C80 high performance concrete mixed with and without polypropylene fiber at 20-800 °C were evaluated. Based on the CT technique, the microstructural changes of C80 high performance concrete at different temperatures were analyzed, and the mechanism of thermal expansion performance was dis-cussed. The results showed that the linear expansion coefficient and expansion rate of concrete tend to increase with the increase of temperature and the differential linear expansion coefficient would slightly fluctuate before 560℃. With the decrease of temper-ature, the linear expansion coefficient of concrete increases and the expansion coefficient decreases. In addition to the individual temperature point, the line expansion coefficient was stable. The linear expansion coefficient, the expansion rate and differential linear expansion coefficient of concrete mixed with 0. 2 % polypropylene fiber were relatively low. The results also indicated that the incorporation of polypropylene fibers can reduce the thermal expansion of concrete. CT test showed that the internal defect rate of C80 concrete mixed with 0. 2% polypropylene fiber was lower, while the relative defect rate was higher. It was shown that the incorporation of polypropylene fibers increaseed the pore connectivity and the internal vapor pressure escaping route, which can effectively improve the performance of high strength and high performance concrete at high temperature.
出处
《中国科技论文》
北大核心
2017年第13期1477-1481,共5页
China Sciencepaper
基金
国家自然科学基金资助项目(51478290)
关键词
C80高性能混凝土
聚丙烯纤维
线膨胀系数
热膨胀率
微分线膨胀系数
CT
C80 high performance concrete
polypropylene fiber
the linear expansion coefficient
the expansion rate
the differential linear expansion coefficient
CT
