铁路钢筋混凝土桥梁结构混凝土氯盐病害

基于严重病害的既有铁路钢筋混凝土桥梁的检测实践,通过对典型病害构件(桥面板、盖梁、梁体、墩等)混凝土的试验测试分析,研究了实际服役环境条件下铁路钢筋混凝土桥梁氯盐侵蚀破坏特征,调查了混凝土中氯离子迁移特性和分布,以及相应混凝土中的碱含量、pH值的变化规律.结合微观结构分析,进一步对铁路钢筋混凝土桥梁的氯盐破坏机理及其微观结构特征进行了深入探讨.研究结果表明:氯化钠盐溶液在该结构混凝土中的迁移速度非常快且发生了物理结晶作用;氯化钠盐溶液的侵入引起了混凝土中碱含量的明显增加和pH值的降低.混凝土内部孔结构发生了明显粗化.研究结果可为既有铁路钢筋混凝土桥梁氯盐病害的整治与修复提供科学依据和技术支持.

Deterioration of railway reinforced concrete bridge structure attacked by chloride salt

On basis of inspecting practice of deterioration of existing railway reinforced concrete bridge attacked by chloride salt, the migration characteristic of chloride ion in concrete and the corresponding deterioration characteristics of typical damaged bridge elements such as deck slab, bent cap, girder and pier are investigated in detail experimentally. The content of alkali and variation of pH value in corresponding concrete are also analyzed. Furthermore, the mechanism of deterioration of concrete and the microstructure of corresponding concrete are discussed. Results indicate that the migration velocity of chloride ion is rapid in corresponding concrete and also there exists physical crystallization action of sodium chloride solution. The ingress of sodium chloride salt into concrete results in an increase of alkali and a reduction of pH value. The pore structure of corresponding concrete is coarsened. This study benefits the renovation or repair of existing railway reinforced concrete bridge suffered from chloride salt action.