Degradation Mechanism And Laws Of Bond Properties Of Reinforced Concrete Under Current Accelerated Corrosion

At Present,Corrosion has brought enormous ecomomic losses to our country.Because of its universality,concealment,gradual and sudden characteristics,it not only consumes resources and pollutes the environment,but also causes related engineering accidents,which brings huge potential safety hazards to the society.Accelerated corrosion of reinforced concrete members is commonly used in labaratories.However,due to the de-normalization of corrosion method,larger average current density is often chosen to accelerate the corrosion of reinforced concrete members in order to shorten the test cycle.At the same time,corrosion directly damages the interface between steel and concrete,which leads to the degradation of bond properties of reinforced concrete members.However,little attention has been paid to the effect of current densities on the bond properties in the accelerated corrosion method.Therefore,in this paper,four different average current densities,namely 200?A/cm~2,400?A/cm~2,600?A/cm~2 and 1000?A/cm~2,are used to accelerate corroison of reinforced concrete.The evolution laws of reinforced concrete in the process of static current accelerated corrosion and change and degadation rules of bond properties are studied.Besides,the quantitative anaysis methods of corroded steel/concrete interface are given from the aspect of mico level.Firstly,four different current densities have been applied to the reinforced concrete in the accelerated corrosion method,and the crack propogation in the cross section is recorded to study the law of maximum crack width along with time and the law of maximum crack width along with electric quantity under different current densities.The results show that the maximum crack width of cross section is affected by the average current density in the process of accelerated corrosion.The larger the current,the larger the crack width,but the maximum crack width is still mainly affected by the actual corrosion level.Secondly,through central pull-out tests,the effects of current on the bond failure modes and bond strength of corroded reinforced concrete are studied,and the influence of current density on the relationship between the corrosion level and normalizde bond strength is analyzed.The results show that the higher the current,the smaller the critical corrosion level,and the more severe degradation of the normalizde bond strength with the corrosion level.At the same time,the relationship between normalized bond strength and longitudinal crack width under different current densities is explored.The results indicate that both the average crack width and maximum crack width can to what extent characterize the bond strength of the corroded reinforced concrete,and the characterization is still affected by the magnitude of current densities in the accelerated corrosion method.Finally,the preperation method for the samples used to oberve the corroded steel/concrete interface under SEM is detailed given.Meanwhile,the methods and limitations of quantitative analysis of every part of the corroded steel/concrete interface are summarized.On this basis,a gray-scale analysis method is proposed.A pratical example is given to prove that this mehod can solve the problems in existing methods.