Research On Damage Deterioration Mechanism Of Concrete Under Chloride-sulfate Attack

With the construction of coastal infrastructure and ports as well as the development of ocean engineering industry,improving the durability of concrete in marine environment has a very important practical significance to ameliorate the quality and service life of the project.The damage mechanism of concrete under chloride-sulfate attack is the basis to solve the durability problem of concrete in marine environment.In this paper,C45 ordinary portland cement concrete was selected as the research object.By using experimental research and theoretical analysis as research methods,the diffusion rules of chloride and sulfate ion,as well as the mechanical properties and damage deterioration law of concrete were studied systematically.The main research findings achieved are as follows:(1)Chloride ion content and sulfate ion content at different depths from the surface of specimens were measured.The change of the content of chloride ion and sulfate ion in the concrete with the ion concentration in the corrosion solution and the mutual influence between the two kinds of ion diffusion were studied.Based on Fick diffusion law,the diffusion coefficient of chloride ion and sulfate ion was calculated.diffusion influence equations of chloride and sulfate were fitted and given respectively.(2)Stress-strain curves of concrete were drawed under the different concentration conditions of corrosion solution.The change of the compressive strength,elastic modulus and peak strain of concrete with the ion concentration in the corrosion solution were studied,which reveals the deterioration characteristics of concrete under chloride-sulfate attack.(3)On the basis of damage mechanics and the mechanical testing data of concrete under the different concentration conditions of corrosion solution,with elastic modulus and secant modulus defined as the damage variables,erosion damage evolution equation,uniaxial compression elastoplastic damage evolution equation and damage constitutive equation of concrete were established.the fitting parameters were confirmed by the experimental curves.The theoretical model fit well with the experimental results.