Phase Field Method For Concrete Cracking Induced By Chloride Erosion And Corrosion

With the widespread use of reinforced concrete,the deterioration of structural durability due to the corrosion of rebars in reinforced concrete is a prominent problem in the civil engineering of building construction,especially for the reinforced concrete facilities in marine or high salinity environments.Due to the process of concrete cracking involves the chloride penetration,the mechanism of corrosion,and the complex cracking process in cement,it is a big challenge to predict the concrete durability accurately.Therefore,developing an efficientand scientific approach to evaluating this process is of vital importance.To address this problem,a chemo-mechanically coupled analysis method is developed for analyzing the concrete cover cracking and the deterioration of durability induced by corrosion.The main work and results are as follows:(1)The unified phase field model for concrete failuer is established: In order to study the corrosion-induced concrete cracking problem,the unified phase field theory is introduced to describe the cracks of quasi-brittle materials such as concrete.Through a series of numerical simulations of benchmark tests,the applicability and superiority of the unified phase field theory in simulating the failure of concrete structures is demonstrated,and the robust of the staggered scheme is also verified.(2)A phase field analysis method coupled with chloride diffusion is proposed: Based on the unified phase-field theory,considering the chloride penetrating,corrosion and concrete cracking due to corrosion,an analysis method is proposed by coupling the phase field variable and the chloride diffusion coefficient.Also the developed method is introduced and implemented into Abaqus standard regime through UEL subroutine. By comparing numerical and experimental results,the accuracy and validity of this method is validated.Based on the method proposed previously,the numerical simulation of concrete cover cracking due to corrosion of single and multiple reinforcement in the macroscopic scale chloride environment is investigated. Furthermore,a parametric study is carried out to investigate the effects of cover thickness,location of reinforcement,reinforcement spacing,initial chloride content in the concrete on cover cracking and spalling.(3)The heterogeneous phase-field concrete model coupled with chloride diffusion is established: The meso-scale concrete model is implemented in Python.The coupling analysis method is applied to investigate the process of chloride ion erosion,the corrosion of single or multiple reinforcement,and concrete cracking under mesoscopic scale.Also,the effects of aggregate distribution,reinforcement location,and reinforcement spacing on concrete cracking patterns are investigated.Comparing the results to the experimental and maro-sacle results,it is concluded that the meso-scale analysis must be considered when predicting the durability and service life of concrete structures in marine or high salinity environments.A new marco/meso-scale numerical method for concrete cracking induced by chloride erosion and corrosion is proposed.Compared with the results based on traditional damage mechanics,it can be found that the adopted method here can well capture the complex crack behaviours like crack deflection,aggregate bridging,reveal the failure process induced by corrosion in chloride environment clearly,show the superiority of the unifiend phase field in simulating cracks of cement materials.This paper provides a refernece for further research on the durability of reinforced concrete.