混凝土中钢筋锈蚀过程非氧 扩散控制的试验研究

通过恒温干燥试验研究了钢筋锈蚀电流随混凝土孔隙饱和度PS的变化规律.通过未锈浸泡、锈蚀后浸泡、锈蚀后继续自然锈蚀的对比试验研究了3种不同条件下钢筋锈蚀速率变化过程,并进行了浸泡前后钢筋锈蚀产物物相变化的XRD分析.恒温干燥试验的研究结果表明,混凝土内钢筋的锈蚀速率随混凝土孔隙饱和度PS的增大而增大,和氧扩散速率的变化规律截然相反.对比试验研究表明,氯盐溶液长期浸泡下未锈试件即使活化也无法锈蚀,而锈蚀试件却可以继续高速锈蚀3个月以上,从而说明氧仅是混凝土内钢筋开始锈蚀的必备条件,而不是混凝土中钢筋锈蚀过程的控制因素.XRD分析表明,钢筋一旦已经开始锈蚀(即有锈蚀产物存在),锈蚀产物中FeOOH可以取代氧成为钢筋锈蚀过程阴极反应的新的去极化,即使在饱水条件下,钢筋的锈蚀仍然可以继续进行.

Experimental Study of the Process Control of Reinforcement Corrosion in Concrete

In order to prove the assumption that the corrosion rate of steel in concrete is controlled by the diffusion rate of oxygen,the effect of Icorr on the degree of the pore saturation in concrete at a given temperature was investigated by monitoring corrosion current.A comparison test of the corrosion rates of passive steel,active steel in completely water saturated concrete and active steel in atmosphere environment was conducted.The phase component of corrosion products of steel bars before and after the specimens were immersed into water was measured with the X-ray diffraction analysis technique.The research has indicated that the corrosion rate will decrease when concrete dries(the pores are more open and the pathway for oxygen is higher).After the corrosion starts,FeOOH in corrosion layer can act as depolarizer instead of oxygen,so the corrosion rate is still very high even if concrete is completely water saturated.The oxygen is one of the factors that influence the corrosion rate but is not the factor controlling the corrosion process of steel in concrete.Therefore,all predictions based on the diffusion rate of oxygen through concrete cover must be regarded as not reliable.