【作者】 张国栋；

【导师】 唐聿明；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2012， 硕士

【摘要】 碳纤维增强钢筋混凝土作为新型的建筑结构材料，拥有非常好的挠曲强度、抗压强度、耐磨性能和抗渗性能，且碳纤维加入后混凝土结构还能够展现出新的电学性能，是一种比传统钢筋混凝土结构更加优秀的结构材料。然而由于碳纤维是良导体，若与混凝土中钢筋接触而发生电偶作用，则可能影响钢筋混凝土结构的耐久性。在混凝土环境中通过分析碳纤维和钢筋之间的电偶作用来评价碳纤维对混凝土中钢筋电化学腐蚀行为的影响，前人没有做过系统的研究，故本文围绕碳纤维和碳钢的电偶作用，利用电化学手段和腐蚀失重实验研究了碳纤维、混凝土模拟孔隙液的pH值以及氯离子对模拟混凝土环境中钢筋的电化学腐蚀行为的影响，并利用XPS分析了碳纤维的偶接对钢筋表面钝化膜的影响。在pH为12.5的模拟混凝土孔隙液中，电化学测试和腐蚀失重实验结果表明，碳纤维与碳钢偶接后，碳钢表面双电层电容Cdl增大，电荷转移电阻Rct减小，钝化膜的厚度发生减薄，表面钝化膜对碳钢的保护性能降低；同时偶接碳纤维后碳钢的腐蚀电位升高，腐蚀电流密度增大，碳钢的腐蚀速率加快。XPS测试佐证了电化学实验结果，偶接碳纤维后，碳钢表面三价铁元素和二价铁元素的比值(Fe³⁺/Fe²⁺)降低，碳钢表面钝化膜的稳定性降低。虽然碳纤维的偶接对碳钢的钝化产生了消极的影响，但是在无氯离子的模拟孔隙液环境中碳钢表面仍然能够保持较好的钝态。研究了pH12.5的孔隙液中碳纤维偶接体积对碳钢腐蚀行为的影响，结果显示，随着偶接碳纤维体积的增加，碳钢表面电荷转移电阻Rct呈现下降趋势，双电层电容Cdl呈上升趋势，膜层厚度变薄；其表面Fe3+/Fe2+比值减小，表明碳钢表面钝化膜的保护性能下降，同时碳钢的腐蚀速率呈现增大的趋势。孔隙液pH的变化是影响钢筋电化学行为重要的因素，故研究了不同pH孔隙液中（13.3、12.5和11.6）偶接碳纤维对碳钢电化学行为的影响。在pH较高的孔隙液（13.3）中，碳钢能够保持很好的钝性，随着孔隙液pH值的降低，碳钢在孔隙液中形成的钝化膜的稳定性有所下降，但仍具一定的保护作用；偶接碳纤维后，碳钢表面钝化膜的稳定性也降低，当pH值和偶接碳纤维两个因素同时作用时，碳钢的腐蚀速率会较大程度地增加，在较低pH值孔隙液（11.6）中，偶接碳纤维体积增大时碳钢很容易发生腐蚀。氯离子是引发混凝土中钢筋锈蚀的主要原因，研究了三种孔隙液中（13.3、12.5和11.6）氯离子对偶接碳纤维碳钢电化学行为的影响。研究发现，孔隙液中氯离子浓度增加，碳钢表面电荷转移Rct略微减小，碳钢表面钝化膜的保护性能下降，碳钢的腐蚀速率随氯离子浓度的增大呈现增大的趋势。在pH为13.3的孔隙液中，在氯离子浓度很高时（2.65%）碳钢也能保持良好的钝性；而在pH为12.5孔隙液中，在较高氯离子浓度（0.7%和1.39%），碳钢就易发生孔蚀；pH值降至11.6，碳钢在较低浓度（0.3%）氯离子环境中就易发生孔蚀；碳纤维的偶接能够增大碳钢在氯离子环境中发生腐蚀的风险，使碳钢在较低的氯离子浓度即可发生腐蚀。研究了氯离子侵蚀作用下掺有碳纤维的水泥砂浆中钢筋的电化学行为。水泥砂浆中，随着碳纤维掺入量的增加（0.2%、0.5%和1%，占水泥质量百分比），钢筋的阻抗值呈现先增加后减小的趋势。在掺入量为0.2%时碳纤维能够提高水泥砂浆中钢筋的阻抗值；当掺入量增加至0.5%和1%，试样的阻抗值开始下降，并降至低于未掺碳纤维的砂浆试样的阻抗值，说明碳纤维掺入量过大时，不利水泥砂浆中碳钢的保护。更多还原

【Abstract】 Carbon fiber reinforced concrete is a new-type building structural materialwith excellent performances such as good flexural stress, good compresivestress, strong wearability and high impermeability property. Besides, carbonfiber reinforced concrete has new electrical property compared with thetraditional concrete material. However, because carbon fiber is a goodelectrical conductor, galvanic corrosion might happen if carbon fiber andsteels contact in concrete, which might have adverse effect on steel, so as tocause the durability of concrete structures reduce. So far, few researchers havestudied the influence of carbon fiber on electrochemical corrosion behavior ofsteel in simulated concrete environment because of the galvanic couplebetween carbon fiber and steel. So this thesis was aimed at the influences ofcarbon fiber, Cl-and pH values on electrochemical behavior of carbon steel insimulated concrete environment by electrochemical tests, weight-loss test. Also, the effect of carbon fiber coupling on the protective property of passivefilm on steel surface was analyzed by XPS.In pH12.5simulated concrete pore solution, electrochemical tests andweight-loss tests results show that after carbon fiber coupling, double layercapacity (C_dl) of steel surface is significantly increased, meanwhile chargetransfer resistance (R_ct) decrease. The changes of Cdland Rctparametersindicate that the passive film formed on steel surface in pore solution becomesthiner when steel is coupled with carbon fiber, and the protective property ofthe steel surface film get weak. Meanwhile, after carbon fiber coupling, thecorrosion potential of steel shifts positively, and corrosion current densityincreases, thus the corrosion rate of steel is accelerated. The results of XPSsupports the conclusion from electrochemical and weight-loss tests: after steelcoupling with carbon fiber, the ratio of Fe³⁺to Fe²⁺on steel surface decreases,which indicates the stability of passive film on steel gets decreased. Althoughcarbon fiber coupling has a negative effect on steel passivation, carbon steelstill could keep good passivation in12.5pH concrete pore solution withoutCl-.The influence of carbon fiber volumes on electrochemical behavior of steelwas studied. With volume amounts increasing, Rctof steel descends,meanwhile C_dlascends, and theFe³⁺ Fe²⁺to Feratio in the passive film on steelsurface decreases. These suggests that with the volume of carbon fibercoupling increasing, the protective property of passive film on steel surface descends, also the film thickness reduces. The corrosion rate of steel showsincreasing tendency when the volumes of carbon fiber coupling increases.The pH value of pore solution is a very significant influence factor on theelectromechanical behavior of steel, so some investigations were focused onthe influence of pH values （13.3,12.5and11.6） on the electrochemicalbehavior of steel coupling with carbon fiber. In the higher pH value poresolutions （pH13.3）, the passivation of steel surface is very good; as the pHvalue decreases （12.5and11.6）, good passivation gets a little weaker. Whensteel coupled with carbon fiber in lower pH pore solution （pH11.6）, thecorrosion susceptibility of steel increases apparently and the corrosion rate ofsteel accelerates.Cl-is the most important factor to induce initiation of corrosion on steelin concrete, so experiments were carried out to study the influence of Cl^-onthe corrosion behavior of steel coupling carbon fiber in various pH value poresolutions （pH13.3,12.5and11.6）. With the concentration of Cl-increases, Rctof steel decreases slightly, the protective property of passive film decends,meanwhile the corrosion rate of steel ascends. In pH13.3pore solution,passivation of steel still maintained even when the Cl-concentration is veryhigh （2.65%）. As pH value of pore solution is decreased to12.5, corrosionoccurrs when the Cl^-concentration is0.7%and1.39%. As pH value falls to11.6, corrosion of steel initiates when the concentration of Cl^-is in acomparatively low level （0.3%）. When coupling with carbon fiber, carbon still is sensitive to corrosion in low pH value pore solutions （pH11.6） evencontaining low content of Cl-.The electrochemical behavior of steel in cement mortar mixed withcarbon fiber has been studied. In cement mortar, as the mixing mass of carbonfiber increases （0.2%,0.5%and1%, the mass ratio of carbon fiber andcement）, impedance of steel firstly increases and then decreases. When thecarbon fiber mass is0.2%, impedance of rebar ascends, which means steel isbetter protected. When the mass of carbon fiber increases to0.5%and1%, theimpedance decreases, which is even lower than the impedance of carbon steelin cement mortar without cabon fiber. So, when mixing mass of carbon fiber isexcessive, it is adverse to the protection of steel rabar in cement mortar.更多还原