氯盐-冻融耦合作用下GFRP筋与纤维自密实混凝土粘结耐久性能

Bond durability between GFRP rebars and fiber reinforced self-compacting concrete under coupled chloride salt and freeze-thaw cycles

  • 摘要: 为了研究不同纤维对玻璃纤维增强聚合物(Glass Fiber Reinforced Polymer, GFRP)筋与混凝土在氯盐-冻融耦合作用下粘结性能的影响,对90个中心拉拔试件进行测试,主要变化参数为冻融循环次数、纤维种类和纤维掺量。试验结果表明:在氯盐-冻融循环作用下,聚丙烯短纤维(PPFA)的掺入可以改善混凝土的抗冻性能,降低钢纤维混凝土与GFRP筋之间粘结强度的损失率。单掺聚丙烯长纤维(PPFB)和钢纤维(SF)均对氯盐-冻融循环作用后GFRP筋与混凝土之间的粘结强度有较大提升。混掺40 kg/m3的SF和2 kg/m3的PPFB后对混凝土力学性能的提升效果最为显著。与未掺纤维的混凝土试件相比,混掺纤维使氯盐-冻融循环作用后混凝土与GFRP筋之间的粘结强度提高了39.4%。基于本文试验结果,考虑氯盐-冻融循环作用的影响,拟合得出粘结-滑移曲线上升段的模型参数,预测结果与试验结果吻合较好。

     

    Abstract: To investigate the influence of various fibers on the bond performance between Glass Fiber Reinforced Polymer (GFRP) bars and concrete under the combined effects of chloride salt and freeze-thaw cycles, pull-out tests were conducted on 90 specimens. The main variables were the number of freeze-thaw cycles, fiber types, and fiber content. The results demonstrate that the addition of polypropylene short fibers (PPFA) enhances the frost resistance of concrete and mitigated bond strength degradation between steel fiber-reinforced concrete and GFRP bars under chloride salt-freeze-thaw conditions. When added individually, both polypropylene long fibers (PPFB) and steel fibers (SF) significantly improve the bond strength between GFRP bars and concrete after exposure to chloride salt-freeze-thaw cycles. The combination of 40 kg/m3 SF and 2 kg/m3 PPFB results in the most notable improvements in the mechanical properties of concrete. Compared to specimens without fibers, the inclusion of fibers increases the bond strength between concrete and GFRP bars by 39.4% after exposure to chloride salt and freeze-thaw cycles. Based on the experimental results in the present study, the ascending branch is established accounting for the effects of chloride salt and freeze-thaw cycles, and the predicted model corresponds well with the testing curve.

     

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