Study On Durability Failure Index And Failure Probability Of Concrete Under Sulfate Attack

There are abundant sulfates in coastal areas and inland lake areas in th e west of China.In these areas,sulfate ions directly contact with concrete structure,which causes serious durability degradation of structure.Sulfate attack is one of the main durability problems of concrete,but at present,there is no systematic stud y on the failure criterion of durability under this environment,and the failure index is only a few macroscopic mechanical properties.Because the current established models are all deterministic models,and the concentration distribution is also determin istic,so it is impossible to analyze the failure probability of the model results,and there are few studies on the uncertainty of the model results.Therefore,this paper starts from the materials,mainly tests,to study the durability failure index and failure probability of sulfate attack concrete,and as a durability evaluation method,based on the sulfate attack concrete model to evaluate the failure probability.The main research contents are as follows:The durability failure index based on critical and cracking concentration is established.The macroscopic mechanical experiment and sulfate ion concentration titration experiment are carried out on the concrete under the sulfate attack and dry wet cycle,and the macroscopic degradation will be analyzed.According to the erosion mechanism and expansion mechanism of sulfate attack concrete,the critical and cracking concentration are calculated,and the critical and cracking thickness are obtained by the distribution curve of sulfate ion concentration.In this study,these two thicknesses are considered as the failure index for analysis.The correlation between the failure index and the macro performance data is analyzed.Finally,the rationality of failure index is analyzed.The durability failure criterion of failure probability is established.The macro performance test,the time-varying curve of the distribution of the mean and standard deviation of the sulfate ion concentration in the concrete under different working conditions are carried out.Based on the normal test of failure thickness,the durability failure criterion and target reliability index related to thickness under sulfate environment are established.The failure probability of concrete durability is solved,and the correlation between the failure probability and macro performance data is analyzed.Finally,the failure probability deterioration model of concrete durability is established.Based on the model of sulfate attack on concrete,the failure probability is evaluated.The theory of sulfate ion concentration distribution of concrete attacked by sulfate is analyzed,and the uncertain parameter of calculation model is considered.The model is calculated by Comsol software,and the results and test data are analyzed.According to the results,the failure thickness is calculated,the thickness is assumed to be uncertain,the failure probability is calculated,and compared with the failure probability calculated by the experimental results.Finally,the concrete under the actual engineering environment is analyzed,and the durability failure life of concrete under different thickness of protective layer and different types of concrete is calculated.