弯曲应力作用下喷射混凝土氯离子扩散研究

采用弹簧四点弯曲加载法，对弯曲应力作用下喷射混凝土受拉区和受压区氯离子扩散性能进行了研究。以Fick第二定律为基准，对氯离子含量分布进行了拟合，分析弯曲应力作用下喷射混凝土氯离子扩散系数的变化规律。通过对比分析同配合比模筑混凝土、喷射混凝土和钢纤维喷射混凝土中氯离子含量分布规律，研究钢纤维和混凝土的成型方式对氯离子扩散性能的影响。结果表明：弯曲应力对喷射混凝土氯离子扩散影响大。应力改变喷射混凝土孔结构分布和微裂缝的数量及深度，对氯离子扩散速率产生影响。受拉区侧，氯离子含量随弯曲应力比增大而增大；受压区侧，氯离子含量随弯曲应力比增大而减小。氯离子扩散系数变化规律与氯离子含量变化规律相同。同应力比时，喷射混凝土氯离子扩散系数最大，钢纤维喷射混凝土和模筑混凝土氯离子扩散系数关系与受力方式、应力比大小、钢纤维和成型方式等有关。

Investigation of chloride ion diffusion in shotcrete under bending loading

By using spring four-point bending loading method, the chloride ion diffusion in shotcrete under the bending loading was studied. Based on the Fick′s second law, the variation law of chloride ion diffusion coefficient of shotcrete was analyzed. By comparing the distributions of chloride ion in molded concrete, in shotcrete and in steel fiber reinforced shotcrete (SFRS), the effects of steel fibers and molding method on chloride ion diffusion were investigated. The results show that the bending stress has an important influence on the chloride ion diffusion in shotcrete. Due to the bending stress, the distribution of pore structure and the number and depth of microcracks can be changed, which may affect the chloride ion diffusion rate in shotcrete. On the side of tension zone, the content of chloride ion may increase with the increase of bending stress ratio. However, the rule is opposite on the side of compression zone. At the same stress ratio, shotcrete has the largest diffusion coefficient, and the relationship between molded concrete and SFRS is related to the stress state, stress ratio, steel fiber and molding method.