盐冻损伤喷射混凝土衬砌结构氯离子扩散及其模型

Chloride Diffusion and Its Model of Shotcrete Lining Structure with Salt-frost Degradation

以海洋环境喷射混凝土衬砌公路隧道为背景,采用快冻法,以3.5%(质量分数)NaCl溶液为冻融介质,开展隧道出入口盐冻损伤喷射混凝土衬砌结构氯离子扩散规律及模型研究。采用固液萃取法和电位法测试喷射混凝土中氯离子的含量,分析盐冻损伤、配合比参数及混凝土成型方式对氯离子扩散的影响。结果表明:盐冻损伤破坏了喷射混凝土表面的微观结构并增大了其孔隙率,增大了氯离子向混凝土内扩散的速率。低水胶比及低粉煤灰取代率的喷射混凝土氯离子含量及扩散系数较小,钢纤维对提升喷射混凝土抗盐冻性能的作用甚微,模筑混凝土氯离子含量及扩散系数明显大于喷射混凝土。盐冻损伤喷射混凝土氯离子含量分布符合Fick第二定律。以盐冻损伤喷射混凝土相对动弹性模量损失率为指标,建立了考虑环境温湿度、喷射混凝土配合比参数及盐冻损伤的氯离子扩散模型。

Chloride diffusion of shotcrete lining structure about highway tunnel in marine environment after salt-frost degradation(3.5wt%NaCl solution)were studied by using solid-liquid extraction and potential method.Meanwhile,the influence factors of chloride ion diffusion on salt-frost degradation,mixture parameter and formed method were analyzed.Then,the chloride ion diffusion model was established based on Fick second law.Salt-frost degradation accelerated chloride ion diffused into shotcrete.Shotcrete with small water-binder ratio and low fly ash replacement had lower chloride content and diffusion coefficient.Steel fiber had little effect on improving salt-frost resistance of shotcrete.Chloride content and ion diffusion coefficient of normal concrete were significantly higher than those of shotcrete.Finally,the chloride diffusion model of shotcrete was established,which considering the environmental temperature and capillary pores humidity,salt-frost damage degree and shotcrete mixture parameters.