海水干湿环境下荷载损伤钢筋混凝土梁的氯扩散性

Chloride diffusion of load damaged RC beams under environment of seawater wet dry cycles

钢筋腐蚀是影响钢筋混凝土结构耐久性的重要因素,而荷载水平与循环加载对混凝土结构的裂缝扩展及裂隙发展有着显著影响,进而影响氯离子在混凝土结构中的扩散性。模拟沿海环境下钢筋混凝土梁的工作状态,试验研究A、B两组钢筋混凝土梁试件考虑荷载水平和循环加载次数变化,在海水干湿环境下的氯氯离子含量变化。A组选择荷载水平分别为0P_u、0.3P_u、0.4P_u、0.5P_u、0.6P_u、0.7P_u(P_u为梁试件的极限荷载)且加载一次;B组选择荷载水平为0.5P_u且循环加载分别0、1、5、10、20次。然后两组荷载损伤RC梁试件经历240次海水干湿循环,最后测定RC梁中混凝土氯离子含量。试验结果表明,随着荷载水平或循环加载次数增加RC梁受拉钢筋附近混凝土氯离子含量增加,尤其是荷载水平达到0.6P_u或0.7P_u、循环加载10或20次时,受拉钢筋附近混凝土氯离子含量明显增加。试验还发现损伤RC梁受拉区0~10 mm深度内氯离子含量呈现先增大后减小有拐点,而在受压区则未发现此现象。上述试验结果将为沿海环境下RC梁结构的寿命预测提供技术依据。

Chloride corrosion is an important factor for durability of reinforced concrete （RC） structures, while the load level and num- bers of loading cycles have a significant influence on the crack propagation of concrete structure,so the chloride diffusion in damaged con- crete structures are impacted.The actual working conditions of RC beams in coastal environment are simulated in laboratory,and two groups of beam specimens （Group A and Group B ） were experimental investigated.The load level of Group A were selected as0P_u、0.3P_u、0.4P_u、0.5P_u、0.6P_u、0.7P_u（P_u is the ultimate load of RC beam specimen）, and loading once.The number of loading cycles for Group B were selsected as 0,1,5,10 and 20 and load level 0.5P_u.Two groups of RC beams specimens loading damaged suffered 240 cycles of sea-water wet-dry.After that,chlorine ion content in RC Beams were tested.Testing results showed that,as the load level or number of loading cycle increased,the chloride ion content on surface of tensile steel bar increased.Especially when the load level was 0.6P_u or 0.7P_u as well as the number of loading cycles was 10 or 20,the chloride ion content on surface of tensile steel bar increased rapidly.The experi- mental results will provide the technical refference to predict service-life of RC beams in coastal environment.