黏结长度对锈蚀钢筋与混凝土间黏结性能的影响

Impact of Anchorage Length on Bond Performance Between Corroded Reinforcing Steel Bars and Concrete

为研究黏结长度(L=2 d、5 d,d为钢筋直径)对锈蚀钢筋与混凝土间黏结性能的影响,通过电化学加速锈蚀方法,获得六组不同钢筋锈蚀率(0.0%、1.0%、2.0%、5.0%、8.0%、10.0%)的中心拉拔试件,并使用裂缝测宽仪记录试件锈蚀后的最大裂缝宽度。通过中心拔出试验,分析了在黏结长度、锈蚀率等影响因子的作用下钢筋与混凝土间黏结性能的退化规律。结果表明,随着锈蚀率的增加,黏结长度较长的试件(L=5 d)锈胀裂纹出现越早,且最大锈胀裂纹越宽。各试件的黏结强度、黏结刚度均随混凝土的劣化及锈蚀率的增加呈现先增长后逐渐下降的趋势,黏结能量则随锈蚀率的增加而逐渐减小。相比于L=2 d的试件,L=5 d试件的黏结强度、黏结刚度更低。基于试验结果,建立了最大锈胀裂缝宽度、黏结强度与锈蚀率的关系式。

A iming at digging out the impact of anchorage length ( L ) of steel bar on bond performance between corroded reinforcing steel bars and concrete, two kinds of cube specimens with different anchorage length ( L =2 d and L =5 d , d is the diameter of rebar) were cast. Six groups of pull-out specimens with rebar mass loss percentage of 0.0%, 1.0%, 2.0%, 5.0%, 8.0%, 10.0% were prepared by means of current accele-rated method, and the maximum width of corrosion-induced cracking on these specimens was measured by fracture width gauge. According to the pull-out tests, the degradation laws of bonding performance between the corroded reinforcing steel bar and concrete were analyzed, conside-ring the influence of anchorage length and reinforcement corrosion rate. The experimental results showed that the expansive cracks in the specimen with longer anchorage length appeared earlier and the maximum crack width became larger because of the increased reinforcement corrosion level. The deterioration of concrete and the increase of corrosion rate would bring about an increase and then gradual decrease in bonding strength and initial bonding stiffness of specimens with diverse anchorage length. Additionally, the growing mass loss of rebars also leaded to the decline of bonding energy. The specimens with longer anchorage length ( L =5 d ) held lower bond strength and bond stiffness than the specimens with shorter anchorage length ( L =2 d ). Finally, an empirical model for predicting corrosion-induced cracking width based on reinforcement corrosion level was proposed, and the relationship between bond strength and corrosion level based on the tested results of previous studies was established, which can evaluate the residual bond strength with different corrosion levels.