Study On Carbonation And Chloride Ion Penetration Of Concrete With Cracks

Carbonation and chloride ion erosion are the main reasons for the premature end of the reinforced concrete structure,and the concrete cracking caused by the external causes has a significant effect on the carbonation process of concrete and chloride ion penetration process.The study of the influence of cracks on concrete carbonation and chloride ion penetration,especially with the change of the position in the cracked concrete and using time,which lays the foundation for the life prediction of reinforced concrete structures.The effects of cracks on concrete carbonation and chloride ion penetration with or without wetting-drying cycles are studied in this paper.The main work is as follows:1.Based on the principle of CO₂ diffusion in concrete,the paper deduces the equation of carbonation process.As ANSYS heat conduction equation is similar to the carbonation equation of ANSYS,a two dimensional model of CO₂ diffusion in concrete established in the paper.The influence of the width,depth and space of the cracks on the concrete carbonation process is analyzed,and the numerical simulation results are verified by the rapid carbonation test.2.Based on the microstructure of concrete,the concrete is considered as a three-phase composite material,which is composed of coarse aggregate,fine aggregate and its interface.According to the Fick second law,the numerical model of the diffusion coefficient of chloride ion in cracked concrete is proposed by using the finite element analysis software--ANSYS,and the reliability and applicability of the model are verified by comparing with the experimental results of Yang et al.3.The transmission process of chloride ion in cracked concrete is simulated,and the influence of different depth and width of slot on the distribution of chloride concentration in concrete is considered.Compared with the soaking test of cracked concrete block,the finite element model is verified.4.Experimental study on the distribution of chloride ions in concrete under dry and wet conditions was carried out.The distribution of chloride ion concentration in concrete was measured by drilling hole,and the chloride ion transport model in concrete under dry wet cycle was established based on the experimental conditions and experimental conditions.