多因素耦合作用下混凝土内氯离子传输试验研究

Experimental study on chloride ion transport in concrete under the coupling effect of multi-factor

海水中氯离子、硫酸根离子和镁离子是海工钢筋混凝土结构的主要侵蚀性离子,硫酸根离子和镁离子侵蚀使混凝土物理力学性能和渗透性发生变化,氯离子侵蚀是造成钢筋锈蚀的主要因素。在海洋潮汐循环下,硫酸根离子和镁离子侵蚀对氯离子传输的影响是有待研究的课题。为此设计单一氯离子、氯离子+硫酸根离子和氯离子+硫酸根+镁离子3种侵蚀溶液,利用潮汐循环系统模拟水位变动,开展混凝土自然暴露试验。在不同暴露时间测定混凝土相对动弹性模量、氯离子浓度分布、孔隙率和孔径分布,同时分析腐蚀产物微观形貌,探究硫酸根离子、镁离子和干湿比对氯离子传输的影响。结果表明:在200d暴露时间内,硫酸根离子和镁离子的存在提高了混凝土相对动弹性模量,降低了氯离子浓度,减小了孔隙率和最可几孔径。相较于单一硫酸根离子,镁离子和硫酸根离子耦合时对氯离子传输的抑制作用更显著。

Chloride ions,sulfate ions and magnesium ions in seawater are the main corrosive ions in marine reinforced concrete structures.Sulfate ion and magnesium ion erosion cause changes in properties and permeability of physical mechanics of concrete,and chloride ion corrosion is the main factor of steel bar corrosion.The effect of sulfate ion and magnesium ion corrosion on chloride ion transport under the marine tidal cycle is a subject to be studied.To this end,three corrosive solutions,namely single chloride ion,chloride ion+sulfate ion and chloride ion+sulfate ion+magnesium ion,were designed to simulate water level changes using the tidal cycle system to carry out natural exposure tests on concrete.Relative dynamic module of elasticity,chloride ion concentration distribution,porosity and pore diameter distribution of concrete are measured at different exposure times,and the microscopic morphology of corrosion products are also analyzed to probe into the effects of sulfate ions,magnesium ions and wet-dry ratio on chloride ion transport.The results indicate that the existence of sulfate ions and magnesium ions increase the relative dynamic module of elasticity of concrete,decrease the chloride ion concentration,and reduce the porosity and the most available pore diameter during the 2o0 d exposure time.Compared with sulfate ions,the inhibition of chloride ion transport is more transparent when magnesium ions and sulfate ions are coupled.