Durability of Reinforced Concrete Structure Repaired by Desalination

海水淡化是一种旨在从钢筋混凝土结构中去除氯化物的电化学方法。本文研究了海水淡化对钢筋混凝土结构耐久性和承载能力的影响。本研究得到的结果可以总结如下。(1)拉拔试验结果表明，处理后试件的最大粘结应力小于未处理试件。随着氯化物预混量的增加或总电流密度的增加，由于电流的通过在钢筋周围形成了软层，海水淡化造成的减少变得更大。(2)根据含8.0 kg/m3 C1的梁的抗弯试验结果，在处理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，经过4周处理的试件在钢筋水平处的最大裂缝宽度小于未处理的试件。但部分试件处理8周后，钢筋水平的最大裂缝宽度大于允许裂缝宽度。此外，海水淡化使裂缝数量减少，裂缝分布恶化。(4)对处理后的预应力钢进行慢应变速率拉伸试验，结果表明，预应力钢的弹性性能和强度相关性能均未发生变化，但其断裂行为受到氢吸收的影响。例如，与未处理的试样相比，应力-应变曲线的下降分支缩短，断裂钢截面的收缩率降低。(5)经处理的PC梁受弯加载试验结果表明，与未经处理的试件相比，未观察到预应力钢因氢脆而破裂，且两种荷载-位移性能均未因脱盐而降低。

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.