溶液浓度与组成成分对氯离子在裂缝中传输速率的影响

Effects of Solution Concentration and Composition on the Transport Rate of Chloride Ions in Cracks

裂缝作为氯离子在混凝土中快速传输的渠道,对混凝土耐久性影响显著,裂缝中溶液性质是影响氯离子传输速率的主要因素之一。为排除裂缝形貌的影响,本工作预制了有机玻璃和水泥净浆平直裂缝,设计了氯离子在裂缝中稳态扩散的实验方法,研究了溶液浓度(2%、3.5%、5%、7.5%、10%NaCl溶液(质量分数))和组成成分(3.5%NaCl溶液(质量分数)、人工海水、真实海水)对氯离子在裂缝中传输速率的影响。结果表明:相同裂缝宽度下,氯离子在有机玻璃和水泥净浆平直裂缝中的传输速率相近。当裂缝宽度增大时,裂缝中氯离子扩散系数随之提高;当裂缝宽度从30μm增大至300μm时,氯离子扩散系数有较明显的提高,当裂缝宽度更大时,裂缝中氯离子的扩散系数的增长趋势减缓;随着NaCl溶液浓度的提高,裂缝中氯离子扩散系数逐渐提高,裂缝宽度越大,NaCl溶液溶度的影响越显著。当裂缝宽度不大于115μm时,3.5%NaCl溶液和人工海水的测试结果与真实海水测试结果相近;当裂缝宽度大于115μm时,3.5%NaCl溶液测得的结果偏大,而人工海水测试结果与真实海水相近。

Cracks are channels for the rapid transport of chloride ions in concrete,which have significant influences on concrete durability.The nature of the solution in crack is one of the main factors affecting the transport rate of chloride ions.In order to exclude the influence of the crack morphology,this study prefabricated plexiglass and cement paste straight cracks,and designed the steady-state chloride transport test in cracks.The effects of solution concentration(2%,3.5%,5%,7.5%,10%NaCl solution)and composition(3.5%NaCl solution,artificial seawater and real seawater)on chloride transport rate in cracks were studied.The results showed that the chloride transport rate in plexiglass and cement paste straight cracks with same crack width were similar.As the crack width increased,the chloride ion diffusion coefficient in crack increased.When the crack width increased from 30μm to 300μm,the chloride ion diffusion coefficient in crack increased significantly.When the crack width was larger,the chloride ion diffusion coefficient increased relatively slowly;with the increase of NaCl solution concentration,the chloride ion diffusion coefficient in cracks gradually increased,and the larger the crack width,the more significant the influence of NaCl solution concentration.When the crack width was smaller than 115μm,the results of tests performed with 3.5%NaCl solution and artificial seawater were similar to that with the real seawater;when the crack width was greater than 115μm,the results of tests with 3.5%NaCl solution were relatively higher,while the results of the tests with artificial seawater were similar to those with real seawater.