混凝土在硫酸盐、氯盐复合溶液定向腐蚀下劣化规律研究

Study on the deterioration process of directional corrosion of concrete in sulfate and chloride solution

在隧道环境中混凝土一面与空气接触,另一面与土壤接触,因此普遍存在混凝土单面定向环境水腐蚀现象.文中模拟了隧道混凝土在硫酸盐与氯盐复合作用下定向腐蚀的过程,将普通混凝土试块做半密封处理,放在3种溶液(质量分数为10%的Na_2SO_4溶液、5%NaCl+10%Na_2SO_4复合溶液、10%NaCl+10%Na_2SO_4溶液)中长期浸泡,研究混凝土中不同氯离子情况下硫酸根离子传输规律;通过超声声速计算混凝土的相对动弹性模量(Erd),探究混凝土在复杂腐蚀环境中损伤失效规律;最后通过微观检测研究腐蚀规律的微观机理.结果表明:在腐蚀溶液中氯离子的存在降低了硫酸根离子的扩散能力,明显降低了混凝土的硫酸盐腐蚀程度,并且氯离子浓度对硫酸根离子扩散抑制作用成正相关;受硫腐蚀混凝土相对动弹模经历了先增加,后降低的过程;受混合溶液腐蚀混凝土相对动弹模量降低程度明显低于受单一硫酸盐腐蚀后的混凝土.

In the tunnel environment,concrete is exposed to the air,the other side is contacted with the soil,so the concrete single directional environment of water corrosion is common. This paper simulates the tunnel concrete under the action of sulfate and chloride salt compound directional corrosion process. Ordinary concrete blocks are half sealed and immersed in three kinds of solutions（mass fraction of 10 % Na_2SO_4 solution,5 % NaCl＋ 10 % Na_2SO_4 complex solution,10 % NaCl ＋ 10 % Na_2SO_4 solution）,the law of sulfate ion transport in different chloride ions in concrete is studied; the ultrasonic velocity of concrete and relative dynamic elastic modulus（ERD） are calculated,the damage process of concrete is explored in complex corrosion environments,and the microscopic mechanism of corrosion law is studied by microscopic examination. The results show that： in the corrosion solution in the presence of chloride ion the sulfate,ion diffusion capacity is decreases,the degree of the sulfate corrosion of concrete is significantly reduced,and the chloride ion concentration and the sulfate ion diffusion inhibition is positive correlated; the relative dynamic elastic modulus of the corroded concrete is increased first and then decreased; the relative dynamic elastic modulus of concrete corroded by mixed solution is significantly lower than by the single sulfate corrosion of concrete.