海水干湿循环下裂缝宽度对钢筋混凝土柱耐久性的影响  

Effect of crack widths on durability of reinforced concrete columns under seawater wet-dry cycles

作　　者：雷奕玮 叶英华[1,2] 沈孛[1] 刁波[1,2] 

机构地区：[1]北京航空航天大学土木工程系,北京100191 [2]华南理工大学亚热带建筑科学国家重点实验室,广东广州510640

出　　处：《混凝土》2015年第5期18-22,共5页Concrete

基　　金：国家自然科学基金(51178020;51108015);亚热带建筑科学国家重点实验室开放课题(2013KA03)

摘　　要：正常使用条件下，裂缝在钢筋混凝土（RC）结构中不可避免，沿海地区的 RC 结构裂缝使氯离子更容易浸入混凝土腐蚀钢筋，严重影响结构耐久性。在试验室模拟沿海地区环境，对不同宽度的初始裂缝（裂缝宽度 w 分别为0、0．07、0．1、0．14 mm）的RC 柱试件进行100次海水干湿循环侵蚀后，测试其受拉侧保护层混凝土不同深度范围（0～10、10～20、20～30 mm）的氯离子含量，计算出表观扩散系数（Dw ），并对构件寿命进行了预测。结果表明：与无裂缝柱相比，当裂缝宽度 w ﹤0．1 mm 时，氯离子含量差别不大；当0．1 mm≤w≤0．14 mm 时，0～10 mm 深的氯离子含量略有增加，10～30 mm 深的氯离子含量明显增大，达到无裂缝柱的1．79～3．12倍。当 w ﹤0．1 mm 时，Dw 随 w 增大缓慢增长；当0．1 mm≤w≤0．14 mm 时，Dw 增长迅速，达到无裂缝柱的3～5倍。提出基于裂缝宽度 w 的修正表观扩散系数 Dw 及其计算式，计算式计算结果与试验结果吻合良好。随 w 增大，计算寿命明显缩短，当裂缝宽度 w≥0．13 mm 时，较无裂缝区缩短80％以上。It is inevitable that cracks exist in reinforced concrete structures under service load.Cracks can make coastal reinforced con-crete structures vulnerable to chloride ion,which significantly lower their durability.The coastal environment was simulated in the labo-ratory.Reinforced concrete columns were with different initial cracks（widths of 0,0.07,0.1,0.14 mm,respectively）.After 100 wet - dry cycles,the chloride content in concrete cover in depths of 0～10,10～20,20～30 mm was tested,respectively.Then the chloride diffusion coefficients（Dw ）and service life were calculated.As a result,firstly,when w ﹤ 0.1 mm,chloride content changes little.When 0.1 mm≤w≤0.14 mm,the chloride content in depth of 0～10 mm increases slightly,while chloride content in depth of 10～30 mm increases sig-nificantly,which is 1.79～3.12 times that of column without cracks.Secondly,when w ﹤ 0.1 mm,Dw increases slightly as crack width in-creases.When 0.1 mm≤w≤0.14 mm,Dw increases significantly and it′s 3～5 times that of column without cracks.A formula is pro-posed to consider the effect of w on Dw ,which agrees well with the experiment results.Finally,it shows that service life significantly re-duces when crack width increases.When w≥0.13 mm,the reduction can be more than 80%,compared to area of no crack.

关 键 词：钢筋混凝土偏压柱 氯离子 干湿交替 裂缝 扩散系数 寿命预测 

分 类 号：TU528.01[建筑科学—建筑技术科学]