【摘要】 综合考虑混凝土氯离子扩散系数的影响因素和混凝土内凝胶体吸附氯离子的能力,根据Fick第二定律建立描述混凝土内氯离子扩散的有限元模型,侧重研究截面形状(矩形、圆形截面)及钢筋阻滞作用对混凝土内自由氯离子浓度演化及钢筋初始锈蚀时间的影响。研究表明:混凝土凝胶体对氯离子的吸附作用可以延缓钢筋初始锈蚀时间,矩形截面角部区域受到两个方向氯离子扩散的影响,该处自由氯离子浓度显著增加,该处钢筋率先锈蚀并发生顺筋裂缝。当混凝土保护层厚度较大或边界浓度较小时,圆形截面对钢筋初锈时间影响更显著。考虑阻滞作用更加真实地反映实际情况,阻滞作用导致钢筋前沿自由氯离子浓度增加,边界浓度较小或保护层厚度较小时阻滞作用对钢筋初锈时间影响更明显。更多还原

【Abstract】 Chloride-induced corrosion of reinforcing steel can cause the performance deterioration of reinforced concrete structures in marine environment. In this paper, the Fick’s second law is used to describe the free chloride concentration evolution in concrete considering the effect factors of chloride diffusion coefficient and chloride binding isotherms caused by cementitious materials. The effects of cross-section shape and obstruction on corrosion initiation time were discussed thoroughly. The corrosion initiation time can be prolonged for some chlorides bound by physical and chemical adsorption. The free chloride concentration at corner of square cross-section is much larger because it is influenced by chlorides from two directions. The corrosion initiation of reinforcing steel at corner becomes shorter and the longitudinal cracks along bars arise early. The influence on corrosion initiation of reinforcing steel is significant in circular cross-section,especially when concrete cover is thicker or boundary chloride concentration is lower. Free chloride concentrations increase at the frontier of rebar considering the obstruction of rebar. The obstruction gives much influence on corrosion initiation,especially when concrete cover is thinner or boundary chloride concentration is lower.更多还原