Study On The Deterioration Law And Uniaxial Compressive Constitutive Relationship Of Concrete Under Sulfate Attack

Sulfate attack is mainly concentrated in the coastal areas of southeast China,the saline soil areas and salt lake in northwest China.For the concrete structure in the water level change area,the degradation damage is more severe due to the sulfate erosion enhanced by the influence of wet and dry cycle.Sulfate erosion will bring serious damage to the structure and greatly reduce the service life of the structure.At present,the evaluation indexes of sulfate erosion mainly adopt the mass loss ratio and expansion rate,but the reported research results cannot provide the constitutive relation of sulfate erosion concrete and the useful evaluation indexes for structure safety evaluation.Therefore,in this paper,it has been carried out the study on the degradation law and uniaxial compression constitutive relationship of concrete under the combined action of sulfate erosion and wet and dry cycle.The aim of this paper is to propose an evaluation standard and deterioration prediction model of sulfate erosion concrete which can be applied to the real structural safety evaluation,and t o deepen the understanding of the existing research on uniaxial compression constitutive relation of erosion concrete.The main research is as follows:(1)SEM,TG and XRD were adopted as the main microcosmic experimental means,the changes of the internal microstructure of concrete under the action of dry-wet cycle and sulfate attack were analyzed,and the influence rules of different water-binder ratio and concentration of erosion solution on sulfate attack were revealed through the qualitative and quantit ative analysis of ettringite and gypsum.(2)Dynamic elastic modulus,static elastic modulus,compressive strength and mass change rate were considered as the main macro indicators,the influences of different water-binder ratio and concentration of erosion solution on sulfate erosion damage were analyzed.The degradation models of dynamic elastic modulus,static elastic modulus and prismatic compressive strength of concrete were established considering the influence of water-binder ratio,concentration of erosion solution and erosion age.The inte gral area of sulfate ion distribution was considered as the main index to describe the process of sulfate attack.The influence of different water-binder ratio and concentration of sulfate solution were analyzed qualitatively and quantitatively by using th e integral area of sulfate ion distribution.The macroscopic mechanical index deterioration model and prediction model of erosion area were established by using the integral area of sulfate ion distribution.(3)The uniaxial compression constitutive relationship of concrete under dry-wet cycle and sulfate attack was studied and the relationship between key parameters of uniaxial compression stress-strain curve of eroded concrete and erosion age was established.Based on the homogenization theory of composite materials,the constitutive relationship of the erosion region of sulphate-eroded concrete was set up.