Durability of Reinforced Concrete Structure Repaired by Desalination

海水淡化是一种电化学方法，目的是去除钢筋混凝土结构中的氯化物。本文研究了海水淡化处理对钢筋混凝土结构耐久性和承载能力的影响，主要研究结果如下：(1)在拉拔试验中，处理试件的最大粘结应力小于未处理试件。随着预混氯化物用量的增加或总电流密度的增加，海水淡化的降幅变大，这是因为电流传递在钢筋周围形成了软化层。(2)根据含氯量为8.0 kg/m~3的梁的抗弯试验结果，处理8周时极限荷载变化不大，挠曲能力增加。(3)对于受弯破坏型梁，处理4周的试件钢筋水平上的最大裂缝宽度小于未处理的试件。然而，在一些处理了8周的试件中，钢筋水平上的最大裂缝宽度大于允许的裂缝宽度。经过脱盐处理的PC棱镜试件的慢应变速率拉伸试验表明，PC棱镜试件的弹性行为和强度相关性能没有改变，但其断裂行为被吸附的氢改变了。例如，与未处理的试件相比，应力-应变曲线上的下降分支缩短，断裂钢材的收缩速率降低。(5)经过处理的PC梁的弯曲加载试验结果表明，与未处理的试件相比，未观察到预应力钢材的氢脆断裂，两者的荷载-位移性能都没有降低。

Desalination is an electrochemical method aimed at removing chlorides from reinforced concrete structures. In this study, influences of applying desalination on durability and load-carrying capacity of RC structures were investigated.The results obtained in this study can be summarized as follows.(1) As results of the pull-out test, maximum bond stress of treated specimens was found to be smaller than that of non-treated specimens. The decrease due to desalination became larger with an increase in the amount of premixed chlorides or an increase in the total current density, because soft layers were formed around the steel bars due to passing of electric current.(2) According to the results of flexural test of beams containing 8.0 kg/m3 of C1, the change in the ultimate load was slight and the capacity of deflection increased at 8 weeks treatment.(3) In the case of flexural failure type beams, maximum crack width at the reinforcing steel level of specimens receiving 4 weeks treatment was less than that of non-treated ones. However, in some specimens treated for 8 weeks, maximum crack width at the reinforcing steel level was greater than the permissible crack width. Moreover, by applying desalination, the number of cracks was decreased and crack distribution became deteriorated.(4) Slow strain rate tensile tests on prestressing steel removed from treated PC prism specimens indicated no change in elastic behavior nor strength-related properties but the fracture behavior was altered by the absorbed hydrogen. For example, the falling branch in stress-strain curves was shortened and the contraction rate of fractured steel section decreased as compared with non-treated specimens.(5) As results of flexural loading tests on treated PC beams, the rupture of prestressing steel due to hydrogen embrittlement were not observed, and both load-displacement performance was not reduced by desalination, compared with the non-treated specimens.