Numerical Simulation Of Sulfate Corrosion Concrete Under Alternation Loading

Sulfate attack is one of the main reasons to the damage of concrete structure and memberunder the marine or salty area, especially the concrete materials under the practical servicecondition which suffer the erosion of salt solution and bear the dynamic loading. Anddynamic loading greatly influences the process of the erosion of salt solution and internalmechanical response. It was insufficient, however, for the research of transfer law of salterosion， expansion internal stress and erosion life prediction, which were exploredinnovatively in this paper.Based on the detailed analysis of erosion mechanism of sulfate attack to the concrete, itwas concluded that the calcium aluminates crystallization expansion destruction is the mainreason of sulfate attack to the concrete. Through the process of diffusion approach division，the characterization of diffusion coefficient and micro-crack homogenization, effectivediffusion coefficient(Dt) was proposed, which effectively characterizes the parameters ofstress level of alternating load，loading frequency，concentration of external sulfate andoriginal porosity. On the basis of the Fick second law in unsteady state diffusion, thediffusion-reaction model was built and the finite difference method was used to realizenumerical solution. Based on the corrosion fatigue experiments, the concentration of sulfate(SO24) of the fatigue specimen at the fixed position in different ages was titrated by chemicalanalysis, and the results were contrasted with the calculated values. Based on an overallconsideration of the parameters of stress level of alternating load, loading frequency,concentration of external sulfate and original porosity, the influence of these factors to themigration law and rate of sulfate attack to the concrete were analyzed. On the basis ofchemical reaction equations of calcium aluminates crystallization expansion destruction, thecalculation process of volume expansion ratio, swelling strain and internal mechanicalresponse were deduced. This paper analyzed expansion internal stress of different parameterscondition of the concrete under corrosion and fatigue environment, and sensitivity analysiswas carried out with the grey incidence analysis. The chemical-stress damage constitutive model for the concrete under corrosion and fatigue environment was built. Finally, numericalsolution of uniform design experiment and the fitting regression of life prediction equationwere conducted. This paper will be used to provide theoretical guides for structural design andconstruction of the concrete under corrosion fatigue.