摘要
氯离子扩散引起的钢筋腐蚀是海洋环境下混凝土失效的主要原因,而海水中硫酸盐、镁盐会对混凝土中氯离子扩散产生影响。将硅酸盐水泥砂浆暴露在具有相同氯离子浓度的不同模拟海水盐溶液中(NaCl、NaCl+MgCl_(2)、NaCl+Na_(2)SO_(4)和NaCl+Na_(2)SO_(4)+MgCl_(2))进行干湿循环试验,研究海洋环境下硫酸盐、镁盐对水泥砂浆中氯离子传输与扩散性能影响规律,利用XRD、TG-DSC、SEM-EDS和MIP等微观方法分析其机理。结果表明:相比于单一NaCl溶液,Mg^(2+)和Mg^(2+)+SO_(4)^(2-)加速氯离子侵入,增加氯离子表观扩散系数,而NaCl+Na_(2)SO_(4)溶液中氯离子扩散系数表现出先增大后降低,浸泡在NaCl+Na_(2)SO_(4)+MgCl_(2)溶液中的氯离子扩散系数最大,在干湿循环初期,SO_(4)^(2-)促进钙矾石形成,细化基体孔径,阻滞氯离子扩散,而在干湿循环后期,SO_(4)^(2-)增大基体微裂缝形成,使得氯离子扩散系数增加;而Mg^(2+)+SO_(4)^(2-)引起硬化体中C-S-H凝胶脱钙和钙矾石形成,增大砂浆的氯离子扩散系数。
The corrosion of reinforcement caused by chloride ions is the main reasons for the failure of concrete in marine environment,while the sulfate and magnesium salts in seawater will affect chloride ion diffusion in concrete.In this paper,portland cement mortar is exposed to four simulated seawater salt solutions with the same chloride ion concentration(NaCl,NaCl+MgCl_(2),NaCl+Na_(2)SO_(4) and NaCl+Na_(2)SO_(4)+MgCl_(2))for drying-wetting cycle test.The effects of sulfate and magnesium salts on chloride ion transport and diffusion in cement mortar under marine environment are investigated.The mechanism is analyzed by micro-methods such as XRD,TG-DSC,SEM-EDS and MIP,respectively.The results show that,compared with single NaCl solution,Mg^(2+)and Mg^(2+)+SO_(4)^(2-) accelerate the ingress of chloride ions and increase the apparent chloride diffusion coefficient,while the chloride diffusion coefficient of mortar exposed to the NaCl+Na_(2)SO_(4) solution first increases and then decreases,and the chloride diffusion coefficient of samples immersed in NaCl+Na_(2)SO_(4)+MgCl_(2) solution is the largest.At the beginning of drying-wetting cycle,SO_(4)^(2-) promotes the formation of ettringite,refines the matrix pore size and blocks the diffusion of chloride ions.At the later stage of dry wet cycle,SO_(4)^(2-) increases micro-cracks and chloride ion diffusion in matrix.The presence of Mg^(2+)+SO_(4)^(2-) causes the decalcification of C-S-H gel and formation of ettringite in hardened matrix,which increases the chloride diffusivity of mortar.
作者
李育林
LI Yulin(Guangxi Road Construction Engineering Group Co.,Ltd.,Nanning,Guangxi 530001,China)
出处
《公路工程》
2022年第5期150-155,共6页
Highway Engineering
基金
广西区交通厅重点科技项目(2021AB22176)。
关键词
海洋环境
氯离子传输
氯离子扩散系数
硫酸盐
镁盐
marine environment
chloride transport
chloride diffusion coefficient
sulfate salt
magnesium salt
