碳纤维布加固对腐蚀钢筋与混凝土粘结性能的影响

正确评估FRP(Fiber Reinforced Polymer)加固对腐蚀钢筋与混凝土粘结性能的影响是确定FRP加固效果的重要问题之一.本文采用外加电流加速腐蚀法对96个预埋钢筋的试件进行腐蚀,腐蚀完成后横向包裹2层单向碳纤维布;通过拉拔试验研究了碳纤维布加固、钢筋种类、保护层厚度及腐蚀率对腐蚀钢筋与混凝土粘结性能的影响规律,探讨了拉拔破坏机理.研究表明:(1)碳纤维布约束使螺纹钢筋试件破坏模式由混凝土劈裂破坏转变为钢筋拔出破坏;(2)钢筋种类、保护层厚度是影响钢筋峰值粘结强度的主要因素,螺纹钢筋试件的峰值粘结强度约为光圆钢筋的2倍;(3)当实际腐蚀率小于5%时,碳纤维布约束对提高钢筋峰值粘结强度作用较小,腐蚀试件峰值粘结强度与未腐蚀试件峰值粘结强度之比(简称比峰值粘结强度)提高约5%—7%,但碳纤维布约束使拉拔全曲线下降段变得平缓,粘结应力维持在较高的水平;(4)当实际腐蚀率大于5%时,腐蚀试件的峰值粘结强度随着腐蚀率增大逐步降低.

Bond Behavior of Corroded Reinforcement in Concrete Strengthened with Carbon Fiber Sheets

Right evaluation of the bond behavior between corroded reinforcement and concrete wrapped with FRP is a chief problem to confirm the effect of FRP confinement.96 test specimens with embedded reinforcing bars were strengthened by two layers of transverse CFRP after accelerated corrosion.The pullout tests on the test specimens were conducted to study the bond behavior between corroded reinforcing bars and concrete,considering the contribution of different elements including reinforcing bar types,cover depths,corrosion rates,and CFRP confinements.The failure mechanisms were studied.The test results showed that CFRP confinements can make the failure mode of deformed reinforcing bar specimens changed from concrete splitting to bar pull-out.The main influencing factors of the ultimate bond strength were reinforcing bar types and cover depths,and the ultimate bond strength of deformed reinforcing bar specimens was one time larger than that of plain reinforcing bar specimens.When the corrosion rate was less than 5%,CFRP confinement had less contribution on increasing the ultimate bond strength,but it was effective on slowing down the bond stress’s descending speed and maintaining the bond strength.When the corrosion rate was higher than 5%,the ultimate bond strength of corroded specimens drops gradually along with the rise of corrosion rate.