炎热海洋环境下混凝土桥梁抗氯离子侵蚀耐久性研究

Study on Durability of Concrete Bridge against Chloride Ion Erosion in Hot Marine Environment

为研究炎热海洋环境中配筋混凝土结构遭受氯离子侵蚀的耐久年限,在Fick第二定律基础上,进行了钢筋混凝土结构服役过程中氯离子扩散机理的研究。氯离子侵蚀钢筋混凝土主要表现在以下5个方面:破坏钢筋钝化膜、形成“腐蚀电池”、阳极去极化作用、导电作用、Fe^(3+)和Fe^(2+)离子化学反应。考虑钢筋混凝土结构中氯离子参与的物理或化学、电化学反应过程,以及混凝土材料的差异性对表观活化能的影响,建立了考虑环境温度影响的氯离子扩散模型。综合不同因素对氯离子扩散速率的影响,建立了考虑温度、水泥组分、时间、荷载、水灰比等因素的氯离子浓度数学模型。根据南方某沿海钢筋混凝土结构的长期暴露试验数据,拟合得到不同温度条件下的氯离子扩散系数,分析了服役一定年限后不同深度处的氯离子浓度,对比了不同温度对不同保护层厚度的混凝土结构在钢筋开始锈蚀时间的影响。计算结果表明:考虑温度对氯离子扩散速率的影响时,钢筋开始侵蚀时间随着温度的增加而缩短,并且随着时间的增加差异逐渐变大,能更好吻合现场实测数据,验证了提出的氯离子扩散计算模型的准确性,为炎热海洋环境中混凝土结构耐久性设计和寿命分析提供了技术支撑。

To study the durability period of reinforced concrete structures subjected to chloride ion erosion in hot marine environment,based on Fick’s Second Law,the mechanism of chloride diffusion during the service process of reinforced concrete structures is studied.Chloride ion erosion of reinforced concrete is mainly manifested in the following 5 aspects:the destruction of steel bar passive film,forming“corrosive cell”,anodic depolarization effect,conductive effect,Fe^(3+)and Fe^(2+)ion chemical reaction.Considering the physical or chemical and electrochemical reaction process of chloride ions in the reinforced concrete structure and the influence of difference in concrete material on the apparent activation energy,a chloride ion diffusion model considering the influence of ambient temperature is established.Synthesizing the influence of various factors on the chloride ion diffusion rate,a mathematical model of chloride ion concentration considering temperature,cement composition,time,load and the water-cement ratio is established.Based on the long-term exposure test data of a coastal RC structure in southern China,the diffusion coefficients of chloride ions at different temperatures are obtained by fitting,the chloride ion concentrations at different depths after a particular service life is analyzed,and the influences of different temperatures on the initial corrosion time of concrete structures with different protective layer thicknesses are compared.The calculation result shows that when considering the influence of temperature on the diffusion rate of chloride ions,the time of rebar erosion starts to shorten with the increase of temperature,and the difference becomes larger with the increase of time,which can better match the field measured data,it verified the accuracy of the proposed chloride ion diffusion calculation model,and provide technical support for durability design and life analysis of concrete structures in hot marine environment.