钢筋混凝土在重盐渍土通电环境中基于Wiener随机过程可靠性分析

Reliability analysis of reinforced concrete based onWiener stochastic process in heavy salt soil electrified environment

为探究服役环境中腐蚀离子和电流对钢筋混凝土耐久性能的影响,以3种不同强度等级的钢筋混凝土为研究对象,将钢筋混凝土棱柱体试件置于重盐渍土中进行恒电流通电加速试验。定期利用电化学工作站和裂缝观测仪进行无损检测,通过极化曲线和交流阻抗图谱分析钢筋混凝土耐久性退化过程。选择非单调Wiener随机退化过程建模,利用极大似然法进行参数估计,根据混凝土裂缝宽度,结合裂缝破坏准则,得到腐蚀电流密度在盐渍土通电加速环境中的失效阈值,并建立通电时间与可靠度的关系曲线。研究结果表明:盐渍土通电环境下,腐蚀性离子通过扩散、渗透及电场吸附进入混凝土内部,并向钢筋表面迁移,混凝土内部pH降低,导电性增强,极化曲向负电位方向发生较大移动,腐蚀发生的概率及速率均增加,交流阻抗图谱呈现出双容抗弧;通电开始后,低频容抗弧半径锐减,并向阻抗实部收缩。混凝土裂缝宽度为0.2 mm时,C35,C40和C45钢筋混凝土腐蚀电流密度失效阈值分别为2.353,1.817和1.187μA/cm2。混凝土强度等级越高,可靠度保持在1.0时的持续时间越长,抗侵蚀能力越强。在腐蚀离子与电流耦合作用下,C35,C40和C45这3类试件分别在160,240和430 h时可靠度降低至1.0以下,通电时间越长,钢筋混凝土可靠度越低。

In order to explore the influence of corrosion ion and current on the durability of reinforced concrete in the service environment,reinforced concrete prismatic specimens of three strength grades were placed in the heavy saline soil for constant current acceleration test.The electrochemical workstation and crack detector were used for nondestructive testing regularly.The degradation process of reinforced concrete durability was analyzed by polarization curve and alternating current impedance graph.Non-monotone Wiener stochastic degradation process was selected for modeling and maximum likelihood method was used for parameter estimation.According to the crack width of concrete and crack failure criterion,the failure threshold of corrosion current density in the electrified accelerated environment of saline soil was obtained,and the relationship curve between electrified time and reliability was established.The results show that in the electrified environment of saline soil,corrosive ions enter into the concrete through diffusion,infiltration and electric field adsorption,and then migrate to the surface of reinforcement.pH value of the concrete decreases and the conductivity increases.The polarization curve moves toward the negative potential.The probability and rate of corrosion increase,and the alternating current impedance spectrum shows double capacitive reactance arc.At the beginning of power on,the arc radius of low frequency capacitive reactance decreases sharply and shrinks to the real part of impedance.When the crack width is 0.2 mm,the failure thresholds of corrosion current density of reinforced concrete for C35,C40 and C45 are 2.353,1.817 and 1.187μA/cm2,respectively.The higher the strength grade of concrete is,the longer the reliability is maintained at 1.0,and the stronger the anti erosion ability is.Under the coupling action of corrosive ions and current,the degree of reliability for C35,C40 and C45 specimens decrease to below 1.0 at 160,240 and 430 h,respectively.The longer the time of power on is,the lower the reliability of reinforced concrete is.