【作者】 马旭； 王新祥； 李建新；

【Author】 Ma Xu;Wang Xinxiang;Li Jianxin;Guangdong Provincial Academy of Building Research Group Co.,Ltd.;

【机构】 广东省建筑科学研究院集团股份有限公司；

【摘要】 硫酸盐侵蚀是影响水泥基材料耐久性的重要因素之一,纯浸泡环境下的外部硫酸盐侵蚀是一个复杂而缓慢的化学、物理和力学过程,包括离子传输、膨胀反应和力学损伤,最终导致宏观膨胀量的增长、材料强度的降低以及渗透性的增加。为了消除材料异质性和尺寸效应的影响,本研究采用了壁厚仅为2.5mm的水泥净浆管。为了探究约束对侵蚀的影响,本研究采用了三种不同约束的应力自施加装置,通过弹簧、3mm直径钢筋棒和7mm直径钢筋棒实现,并通过应变片和CompactDAQ测试系统实现了试验结果的不间断测量。本研究获得了两种浓度(1.5g/L和30g/L硫酸钠溶液)和三种约束下试样膨胀量的长期试验结果,以及硫酸盐侵蚀下试样膨胀应力的长期试验结果(810天),研究发现试样产生的膨胀应力可达13.4MPa。通过MIP试验研究了硫酸盐侵蚀对试样孔尺寸分布的影响,试验结果支持了结晶压理论解释破坏机理。通过SEM-EDS微量分析、X-CT图像分析结合图像处理技术,研究了试样裂缝发展过程及最终裂缝形态。最后,本研究基于Delft Lattice Fracture Model,结合试验结果,模拟分析了约束情况下试样受硫酸盐侵蚀的断裂破坏情况。更多还原

【Abstract】 Sulfate attack is one of the important factors affecting the durability of cementitious materials.External sulfate attack under immersed condition is a complex and slow chemical,physical and mechanical process,in which ionic transport expansive reactions and mechanical damage interact with each other,and finally leads to a growing macroscopic expansion,a total strength loss and an increased permeability.In order to eliminate the influences of material heterogeneity and size effects,the cement paste pipe with a wall thickness of only 2.5 mm was chosen in this research.In order to study the influence of restraint,three types of self-stress-applying restraint were applied,which were realized by a spring,a steel bar with a diameter of 3 mm and a steel bar with a diameter of 7 mm.The strain gauges and CompactDAQ test system were used to obtain the continuous experimental results.For two types of sulfate concentration(1.5 g/L and 30 g/L sodium sulfate solution) and three types of restraint,the long-term experimental results of specimen expansion and specimen expansive pressure(810 days) were obtained.The study shows that the specimen can generate the expansive pressure as high as 13.4 Mpa.The effect on pore size distribution caused by external sulfate attack was studied through MIP,and the experimental results support the crystallization pressure theory to explain the damage mechanism.The crack development and crack pattern were studied through SEM-EDS microanalysis and X-CT image analysis combined with Image processing technique.At the end,based on Delft Lattice Fracture Model and the obtained experimental results,the fracture process of the restrained specimen under external sulfate attack was simulated.更多还原