טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentChernin Leonid
SubjectEffect of Corrosion on the Concrete-Reinforcement
Interaction in Reinforced Concrete Beams
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Konstantin Volokh
Mr. Dimitry Val
Full Thesis textFull thesis text - English Version


Abstract

Reinforced-concrete (RC) is now widely used in the world as a building material. RC structures deteriorate with time due to a number of reasons, one of the main of which is corrosion of reinforcing steel. The corrosion-induced structural deterioration starts with corrosion initiation and the rate of damage accumulation increases with cracking and delamination of the concrete cover. Corrosion affects strength, stiffness and ductility of RC structures, and consequently, their safety and serviceability.


The main objective of this research is to develop tools for the prediction of damage caused by reinforcing-steel corrosion to RC structures. Initially, investigation of crack initiation in the concrete cover and its following development is carried out. A new analytical model based on solution of the partially anisotropic thick-walled double cylinder subjected to internal pressure is developed in order to account for the stage of partial cracking of the concrete cover. This model allows for full compatibility in displacement/strain and stress fields at the common boundary between the outer uniform and the inner anisotropic cylinders. Finite-element (FE) analysis is carried out in order to evaluate the range of applicability of the analytical models. Two models of rust production (linear and parabolic) were considered and calibrated using experimental data. The part of corrosion products diffusing into concrete voids at the time of concrete cover cracking is then evaluated using results of tests with accelerated and natural corrosion. A FE model is then developed to investigate the process of corrosion-induced crack widening. The part of corrosion products penetrating into concrete cracks is evaluated based on available experimental data. A relationship between the degree of rebar corrosion governing crack opening and the crack width is developed, and the restrictions on its use are established. A simple method for calculating the corrosion level in a RC element based on measured crack width is suggested. Further, the corrosion-induced strength degradation of bond between reinforcing steel and concrete is investigated. A new model describing the corroded steel-concrete interface is developed and calibrated. The model accounts for the influence of corrosion on friction and interfacial cohesion between reinforcing steel and concrete.


The tools developed in this research will contribute to understanding the process of deterioration of RC structures suffering from corrosion of reinforcing steel. The knowledge obtained can be used to predict the performance of corroding RC elements including the establishment of their condition on the basis of measurements of corrosion-induced crack widths.