Study On Experiment For The Influence Of Environmental Factors And Bending Load On Anti-Corrosion Performance Of Concrete

The durability is the major issue of concrete structures design. The carbonization and erosion of chloride ions are the main factors of insufficient durability of concrete, which will damage the re-bar in concrete and induce re-bar corrosion, and reduce carrying capacity of RC members to short structural life.The background engineering in this paper was the existing concrete structures under the natural tidal environment. Based on the former studies, a series of erosion tests of RC girders under different environmental factors and flexural loading had been carried out. The influence of loading factors on distribution of free chloride concentration and diffusion ability, concrete carbonation depth and influences of carbon dioxide on distribution of free chloride concentration under designed artificial climate environment had been analyzed. Diffusion properties of concrete under artificial climate, artificial climate environment interaction with the carbonation, standard curing conditions were also analyzed contrastively.Based on the corrosion test on RC member and conclusion analysis, the main studies conclusions in this paper are in the following:(1) The bending load has an obvious effect on concentration distribution of chloride ions and chloride diffusion coefficient in tensile zones in concrete of testing girders. In all the corrosion girders, there were obvious convection zones, which were similar to the concrete members exposed to the natural eroding environment, thickness of convection zone were4mm-8mm.(2) The water-cement ratio, corrosion and curing time has the obvious influence on the free chloride diffusions of the concrete, but the effect of curing time is lower than the water-cement ratio and corrosion.(3) The influence of bending loads on chloride diffusion coefficient is not obvious when the load level is low, but when the level increase to certain extent, the effect of bending load to chloride erosion is particularly obvious. As the bending load reaches30%Fmax-45%Fmax, the diffusion coefficients is2-3times to that without loading.(4) The bonding load and water-cement ratio are the main factors of influencing concrete carbonation depth under artificial climate environment interaction with the carbonation. Either in tensile or compression zones, the depths of carbonation are deeper as the water-cement ratio increased. carbonation depth in tensile zones increased with the increase of load level, the compression zone is opposite. Concrete carbonation depth can be expressed as function of load level η (%) or Do when there’s no load.(5) The results of NEL method test validated the theory that chloride diffusion coefficient reduces gradually along with the standard curing time’s extension. Chloride diffusion coefficient decreases slowed after250days’standard curing. According to available literature, the diffusion coefficient change with time and there is a good linear correlation between empirical constant m and water-cement ratio. Presumption of30day-long concretes diffusion coefficient was16%～35%value of reference expect.(6) According to experiment results, under standard curing condition, the concrete diffusion coefficient tested by NEL method is50%to the artificial climate environment interaction with chloride ions and the carbonation after30years. The influence of CO2on concrete diffusion properties is not obvious under artificial environment.