The Study Of Adherence Layer Effect Of Sulfuric Corrosion To Concrete And Mortar

The main forms of expression of Sulfuric acid corrosion are the acid rain corrosion to buildings and biological sulfate corrosion to pipeline.It is a common problem which exist in the reinforcement concrete structure,and also an important part of the study of concrete durability.The study on the corrosion of sulfuric acid is meaningful to the improvement of the resistance of corrosion and the durability of concrete.Based on the theory of acid consumption rate of sulfuric acid erosion,we analyzes the result of corrosion of concrete and mortar by sulfuric acid in this paper.SEM scanning electron microscope(SEM)and XRD diffraction(XRD)were used to analysis the qualitative and quantitative of the surface layer in the concrete and mortar specimens during the erosion process?The main work of this paper is as follows:(1)According to the theoretical formula of acid consumption changes with time,which deducted by erosion of sulfate acid consumption rate,we assume that the influence of the boundary layer effect at the initial stage of the reaction is negligible.We substitute the constant reaction rate at the maximum apparent diffusion of hydrogen ion dissolution into the theoretical formula in order to obtain the quantitative value of sulfuric acid consumption in the process of erosion without adherence layer effect.Based on the result that mentioned before,a comparison of the actual acid consumption obtained by the test of sulfuric acid and concrete mortar and the quantitative acid consumption has been conducted in order to analyze the effect of sulfuric acid erosion process in the boundary layer effect on the acid consumption.In addition,based on the acid consumption test value curves of bifurcation points with the quantitative values curves,the start time point of the adherence layer effect could be conducted.(2)The concrete samples with the same water-cement ratio were tested in sulfuric acid solution with different acidity ratio and different water-cement ratio mortar samples in the same acidity sulfuric acid solution,and in the mortar test under the same conditions to add a set of periodic replacement of the soaking solution.The apparent characteristics of the test were analyzed,and the acid consumption rate and total acid consumption during the test were determined by the amount of dilute sulfuric acid titration recorded.As the amount of acid consumption changes with time formula for data fitting,get the reaction rate constant did not occur in the adherence layer and the effect of corrosion effect is the biggest moment.And then substituted that value into the formula of acid consumption varies with time,obtain the quantitative acid consumption at the same time,According to the relationship between the experimental value and the quantitative value,It is proved that the effect of adherence layer effect is more significant than the effect of hydrogen ion,meanwhile,the approximate start time point of the influence of the adherence layer effect and the influence of acid consumption on erosion process efficiency is given.(3)By scanning electron microscope and X ray diffraction technology and combining the solubility of each component,the qualitative and quantitative analysis was carried out from the surface of the specimen after the test.It is proved that the effect of the adherence layer is mainly due to the corrosion of the calcium sulfate in the product and the adhesion of C-S-H gel after the reaction with the remaining silica.