Study On The Interface Between The Corroded Reinforcement And Concrete

During the whole life of reinforced concrete structures, the period from depassivation of steel bar to concrete surface cracking is very important. This period influence the behaviour of structures and their service lives. However, the mechanical of this process has not been clearly revealed yet, the time of concrete cover cracking can not be predicted accurately either. This paper focus on the mechanical of the crack process caused by corroded reinforcement by experimental studies and numerical simulations. This project focus on micro structural analysis of Corroded Steel-Concrete Interface (CSCI).The output of this paper will not only contribute to the theory system of durability of concrete structures, but also practically foresee the behavior of cracking in concrete cover due to corrosion for real structures. The main work in this paper can be summarized as follows:(1) An electrochemical accelerated method was used during corrosion of reinforced concrete torsion component. The hoop shear constraint lying between concrete and rust layer was investigated in the torsion test. The relationship between hoop bond shear strength and corrosion level was established.(2) A reinforced concrete specimen which has deteriorated in artificial environment for two years was investigated in this study. The reinforced part of the specimen was cut into a series of 10 mm-thick cross-section slices, and the thickness of rusted layers at the interface of reinforcement and concrete was observed by digital microscope. The non-uniform corrosion front was presented by a Gaussian function in polar coordinate system, the parameters in the model, including spreading coefficient, uniformity coefficient and non-uniformity coefficient of rust layer, were studied to describe the non-uniform distribute characters of rust layer based on the measured data. The location of rust peak along the perimeter of steel bar was also discussed.(3) The stress filed, the distribution and development of cracks, the distribution of interfacial pressure between the concrete and steel bars are very difficult to be tested during the experiments. However, these lacked information in experimental studies can be obtained by FE analysis method. In this paper, to simulate the expansive formation of corrosion products, nodal displacements are imposed at the steel-concrete interface in the finite element model. Three separate corrosion schemes are considered, one representing uniform corrosion and the remaining two non-uniform corrosion. The FE analysis has shown that uneven thickness of the rust layer predicted by the analytical mode was demonstrated ideally suited by the FE results. Meanwhile, utilizing FEA to simulate the expansion of rust is feasible. The FEA result also shown that the strain field and cracking due to rebar corrosion only related to the final distribution of rust layer but not loading ways. This FE study demonstrates the high possibility of obtaining the reliable predictions of concrete surface cracking due to reinforcement corrosion.