受氯盐侵蚀的LNG储罐混凝土外罐耐久性研究

Durability research of the concrete outside of a LNG storage tank subjected to chloride ion attack

对于大型LNG储罐,处于沿海地区,其预应力钢筋混凝土外罐容易遭受氯离子侵蚀,导致内部钢筋锈蚀,引发锈胀开裂,严重影响储罐耐久性能。以某大型LNG储罐混凝土外罐为研究对象,采用COMSOL有限元软件建立LNG储罐模型并进行数值计算。通过数值算例,分析了外部环境和荷载引起的储罐外罐混凝土内的氯离子分布特征,确定了储罐外罐耐久性设计和维护的关键部位,并探讨了水灰比、保护层厚度、养护龄期对诱导期长短的影响规律。结果表明:LNG储罐的第一浇筑带处,钢筋更容易发生锈蚀;如不做特殊处理,最先开始去钝化的位置高程约为0.27 m,去钝化时间为19.7年;建议第一浇筑带采用增加保护层厚度的方式提高储罐整体耐久性,保护层厚度最佳为55 mm。

Large LNG storage tanks are easily deteriorated due to corrosion of steel bars caused by chloride ion attack,which seriously affect the durability of storage tanks.An improved finite element model for a large-scale LNG storage tank was established using the finite element program COMSOL.Numerical simulation is utilized to analyze the distribution of chloride ion inside the concrete outside of a storage tank and confirm the key region of durability design and maintenance.What′s more,it studied the influence law of water cement ratio,the cover thickness,the curing age on the induction period length.The result show the damage of the first pouring is greater than others.The first depassivation of region for a bare concrete storage tank may occur in the place about 0.27 m after in service for 19.7 a.In order to improve the durability of the storage tank,it is suggested that the cover thickness be set to 55 mm.