临海既有混凝土氯离子侵蚀及钢筋初锈时间预测

Chloride Ion Erosion and Prediction of Initial Corrosion Time of Steel Bar in the Existing Coastal Concrete

临海混凝土结构承受着荷载和氯盐侵蚀等多种因素的共同作用，工作环境严酷.根据取得的温州市瓯江口一座既有水闸的闸墩混凝土芯样，推定了混凝土的实际配合比；测定了芯样中不同深度处的自由氯离子浓度，分析了在自然环境下该既有水闸闸墩混凝土的氯离子侵蚀规律；基于Fick第二定律和Monte Carlo法，计算了该闸墩混凝土的氯离子扩散系数及钢筋初始锈蚀时间.结果表明：使用5350d的临海水闸闸墩混凝土中存在明显的氯离子对流区，其厚度超过20mm；在多种因素作用下，临海水闸闸墩混凝土抗氯盐侵蚀的性能严重降低，钢筋初始锈蚀的临界氯离子浓度（质量分数）为0.12%-0.18%，其初始锈蚀时间约为3000d；采用Monte Carlo法预测自然氯盐环境下混凝土中钢筋初锈时间是可行的.

Coastal concrete structures have very tough working environment with combined action of loads, chloride ion erosion and so on. According to the cores drilled from the concrete of one existing sluice pier along Oujiang river estuary region in Wenzhou, the mix proportion of the concrete was determined. Based on measured results of chloride concentration, the erosion regularity of chloride ion in the existing coastal concrete was analyzed, and the diffusion coefficients of the existing concrete and initial corrosion time of steel bars in the concrete were calculated by Ficks second law and the Monte Carlo method. The results show that obviously there exist the convective zones of chloride ion erosion in the 5350d concrete with thicknesses of exceeding 20mm. Under the various actions, the resistance to chloride ion erosion in existing coastal concrete is reduced sharply, and the critical concentration range of chloride ion for steel bars corrosion is 0.12% to 0.18%, and the initial corrosion time is merely 3000 d. The results show also the Monte Carlo method is a feasible method for analysis of the initial corrosion time of steel bars in the concrete in the nature chloride ion environment.