The Cracking Study Due To Chloride-induced Corrosion Expansion For Stressed Reinforced Concrete Members

The durability study of reinforced concrete structure is an important and difficult task,and chloride ion penetration usually is the precondition of durability damage about reinforced concrete structure in marine environment.As for the corrosion of real concrete engineering,it is the result of load and environment effect.Thus the cracking study due to chloride-induced corrosion expansion for stressed reinforced concrete members is meant for durability design and optimization of concrete structures.This thesis used the method of combining theoretical analysis and numerical modeling and took marine reinforced concrete members as the research object.At the same time,the corrosion character of stressed concrete component and unstressed concrete component was studied,and combining cathodic protection the electrochemical mechanism was analyzed and compared based on COMSOL and ABAQUS finite element software.Details are as follows:1.Establishing the unstressed reinforced concrete beam numerical model based on related electrochemical corrosion mechanism,studying the effect of reinforcement position and cover thickness on concrete corrosion character and contrasting the electrochemical reaction between different kinds of steel.Also,the cracking figures under different rebar spacing were discussed.2.Establishing the reinforced concrete beam numerical model under the coupling of load and environment,considering the correction of load damage for temperature transit,water transport and chloride ion transport model and studying the related factors affecting damage coefficient of beam pure bending section.At the same time,the chloride ion diffusion and depassivation behavior were analyzed.Also,the corrosion current changing,corrosion product accumulation and corrosive crack generation process under different damage levels were studied.3.Establishing the numerical model of cathodic protection for concrete cross section and longitudinal section and studying current and potential distribution under macrocell corrosion.Thus we could optimize the structure and theoretical model by comparing the modeling result with the related design standard.Finally,it can work on preventing and controlling concrete cracking.The result showed that:In the case of no loading,the erosion efficiency of corner steel is evidently higher than that of middle steel;The change of cover thickness heavily influences the accumulation of corrosion current;The electrochemical corrosion of ribbed bar is faster and its corrosion rate is bigger than those of plain round bar,and rib spacing and max rib width can affect the corrosion current;Cracking degree and damage is minimum when steel spacing is 2.3 times the steel diameter.In the case of loading,damage correction coefficient is related to load intensity and concrete strength;The relation between crack width and max corrosive displacement is described as w=0.3937-0.3796cos(9.292S_max)-0.07293sin(9.292S_max);The crack influenced area caused by high level damage can't be neglected.In the electrochemical protection,the protective current tends to flow into cathode space and if the impressed current can suppress macrocell corrosion the protective current can flow into anode space;Macrocell corrosion evidently improves the heterogeneity of cathodic protection and protective current can effectively control the macrocell corrosion for electrochemical incompatibility.