碳化对氯离子和硫酸根离子在混凝土中扩散规律影响研究

Influence of carbonation on diffusion of chloride ions and sulfate ions in concrete

隧道混凝土与空气接触的一边受到碳化作用,同时另一边受到来自土壤水环境中腐蚀离子的侵蚀,因此研究碳化作用下腐蚀离子扩散规律具有一定工程意义。模拟了碳化作用后隧道混凝土在硫酸盐与氯盐复合作用下定向腐蚀的过程,将碳化后的混凝土试块(100 mm×100 mm×300 mm)做半密封处理,分别放在质量分数为10%Na 2SO 4溶液、5%NaCl+10%Na 2SO 4复合溶液、10%NaCl+10%Na 2SO 4复合溶液中长期浸泡,研究了双因素腐蚀环境混凝土在碳化作用下离子传输规律及碳化作用对SO^2-4传输规律的影响。结果表明:①混凝土不同深度SO^2-4含量与腐蚀龄期成正比,先碳化再浸泡腐蚀工况下混凝土SO^2-4侵蚀深度远远大于直接浸泡腐蚀工况;②在碳化、Cl^-、SO^2-4多因素作用下,SO^2-4的扩散速度会被Cl^-较大程度地抑制,同时被碳化作用极大地加快;③在碳化、Cl^-、SO^2-4共同作用下,氯盐﹑碳化作用两者的强弱共同决定SO^2-4扩散的速度。

Concrete in the tunnel is not only eroded by the carbon dioxide from the air,but also by the sulfate and chloride ions from soils.Therefore,it is very significant to study the diffusion of chloride and sulfate ions in carbonated concrete.In this study,the directional corrosion process of chloride and sulfate ions was simulated in the carbonated concrete.First,concrete blocks(100 mm×100 mm×300 mm)were carbonated to the specified degree.And then these blocks were treated to become semi-sealing carbonated concrete blocks using vaseline.In the end,in order to research the influence of chloride and sulfate ions to carbonated concrete,these semi-sealing carbonated concreted blocks were divided into 3 groups,the first group was dipped in 10%of Na 2SO 4 solution,the second group was dipped in 5%of NaCl and 10%of Na 2SO 4 composite solution,the last group was dipped in 10%of NaCl and 10%of Na 2SO 4 composite solution respectively.As the results,the content of sulfate iron in concrete increased with the increasing of corrosion age,the corrosion depth of sulfate iron of carbonated concrete blocks was much deeper than the one of concrete blocks without carbonation process.Under the interaction of carbonation,Cl^-and SO^2-4,the rate of SO^2-4 diffusion was inhibited severely because of the existing of Cl^-and promoted because of the carbonation process simultaneously.In conclusion,the diffusion rate of SO^2-4depended on both chlorination and carbonization.