冻融循环和氯盐腐蚀对钢筋与混凝土黏结性能的影响

Study on the bond behaviors of steel bars and concrete after freeze-thaw cycles and chloride corrosion

为了解不同环境对钢筋与混凝土黏结性能的影响,经冻融循环和氯盐腐蚀试验后,对试件进行了拔出测试.研究结果表明:钢筋与混凝土极限黏结强度和延性随冻融循环次数的增加而降低;钢筋腐蚀程度较低时,试件未产生锈胀裂缝,黏结强度较高,但延性较未腐蚀试件下降明显;试件腐蚀后,载荷-滑移曲线斜率增大,极限载荷对应的滑移减小;对于螺纹钢筋试件,当其冻融循环次数较少时,黏结性能无明显变化;光圆钢筋试件在冻融循环25次后,当加载到20kN时,钢筋能产生较大滑移,腐蚀后其黏结强度稍有提高,滑移减小,延性降低;钢筋应力经加载端向自由端逐渐降低,峰值靠近自由端,且随冻融次数的增加趋于平缓.根据试验实测结果并考虑黏结锚固位置,建立了冻融循环和腐蚀作用后钢筋与混凝土的黏结-滑移本构模型.

In order to study the affection of corrosion and freeze-thaw cycles on the bond behaviors between steel bars and concrete,26 specimens are made and the pull-out test after freeze-thaw cycles and chloride corrosion is made.The results show that ultimate bond strength and its ductility decrease with the increase of freeze-thaw cycles times.Bond strength increases and its ductility decreases(compared with unfrozen specimen)while corrosion is low and no corrosive cracks occurs.Slope of bond-slip curve increases and the slip in accordance with maximum bond strength decreases after steel bars corrosion.Bond behaviors of rebar specimens do not incur obvious change after less freeze-thaw cycles.Plain bar specimens occur larger slip while load is 20 kN after 25 times freezethaw cycles,and bond strength increase after corrosion while its slip and ductility decrease.Stress of steel bar decreases from load end to free end and its maximum is value near free end.Stress curves become flat with increasing freeze-thaw cycles.Based on the tested results,considering the position-function of steel bars and concrete,bond-slip model after freeze-thaw cycles and chloride corrosion is proposed.