低温环境中新型水泥基材料抗拉性能和微结构的演化行为

Evolution Behavior of Tensile Properties and Microstructure of New Cementitious Materials at Cryogenic Temperatures

低温环境中混凝土的抗拉性能是影响"全混凝土"液化天然气储罐长期安全服役的重要因素。本文研发了一种新型耐低温高性能水泥基材料(CHC),利用拉伸试验机研究了低温循环(20~-165℃)前后CHC的抗拉性能,借助压汞孔隙率测试和核磁共振测试分析了CHC的孔结构特征。结果表明,相比于C60混凝土,CHC的总孔隙率较低,抗拉强度较大,峰后变形能力较强。低温循环后,微裂缝的出现和总孔隙率的增加导致CHC和C60混凝土的峰值应力下降。相比于C60混凝土,CHC中裂缝的宽度较小,总孔隙率的增加量较少,故CHC峰值应力的下降幅度较低。本研究证实低温循环前后CHC的抗拉性能均优于C60混凝土,这源于CHC优异的孔结构和钢纤维的掺入。

The tensile property of concrete at cryogenic temperatures is an important factor affecting the long-term safe service of "all-concrete" liquified natural gas storage tanks. A new type of cryogenic temperature resistant high-performance cementitious materials(CHC) was developed in this paper. The tensile properties of CHC before and after cryogenic temperature cycles(20 ℃ to-165 ℃) were studied using tensile testing machine. The pore structure characteristics of CHC were analyzed with mercury intrusion porosimetry test and nuclear magnetic resonance test. The results show that the total porosity of CHC is lower than that of C60 concrete, while the tensile strength and post-peak deformation ability of CHC are stronger than that of C60 concrete. After cryogenic temperature cycles, the appearance of microcracks and the increase of the total porosity lead to the decrease of the peak stress of CHC and C60 concrete. Moreover, the crack widths and the increase ratio of the total porosity of CHC are both smaller than that of C60 concrete. Thus the decrease of the peak stress of CHC is lower than that of C60 concrete. This study confirms that the tensile properties of CHC before and after cryogenic temperature cycles are both stronger than that of C60 concrete, which is due to the excellent pore structure and the incorporation of steel fibers in CHC.