受氯盐侵蚀的LNG储罐混凝土外罐耐久性研究
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摘要
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.
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.
引文
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[9]杜修力,金浏.压缩荷载作用下混凝土中氯离子扩散行为细观模拟[J].建筑材料学报,2016,19(1):65-71.
[10]程旭东,孙连方.沿海钢筋混凝土结构Cl-侵蚀数值模拟方法研究[J].中国腐蚀与防护学报,2015,35(2).144-150.
[11]刘军,邢峰.环境参数对大气氯离子作用的影响[J].低温建筑技术,2008(6):4-6.
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[13]ALONSO C,CASTELLOTE M.Chloride threshold dependence of pitting potential of reinforcements[J].Electrochim.Acta,2002,47(21):3469-2476.
[2]徐洁,李少龙,等.海洋大气区预应力混凝土结构氯离子侵蚀模型分析[J].混凝土,2014(12):7-10.
[3]陈素碧,刘荣桂,等.海洋大气区预应力混凝土氯离子传输时间相似关系研究[J].硅酸盐通报,2015,34(11):3338-3344.
[4]程旭东,韩明一,等.LNG储罐外罐施工期间温度应力及裂缝分布[J].天然气工业,2014,34(9):107-112.
[5]CHO S W,YANG C C.Influence of aggregate content on the transport properties of mortar using accelerated chloride migration teset[J].Concr Sci Eng,2002,4(14):84-90.
[6]金浏.细观混凝土分析模型与方法研究[D].北京:北京工业大学,2014.
[7]ZHENG J J.Analytical solution for the chloride diffusivity of hardened cement paste[J].Journal of Materials in Civil Engineering,2008,20(5):384-391.
[8]HANSEN T C.Physical structure of hardened cement paste:a classical approach[J].Materials in Civil Engineering,2008,20(5);384-391.
[9]杜修力,金浏.压缩荷载作用下混凝土中氯离子扩散行为细观模拟[J].建筑材料学报,2016,19(1):65-71.
[10]程旭东,孙连方.沿海钢筋混凝土结构Cl-侵蚀数值模拟方法研究[J].中国腐蚀与防护学报,2015,35(2).144-150.
[11]刘军,邢峰.环境参数对大气氯离子作用的影响[J].低温建筑技术,2008(6):4-6.
[12]建筑结构荷载规范:GB 50009-2012[S].
[13]ALONSO C,CASTELLOTE M.Chloride threshold dependence of pitting potential of reinforcements[J].Electrochim.Acta,2002,47(21):3469-2476.