The Analysis Of The Numerical Model In Concrete Carbonation Depth

The phenomenon of concrete carbonation is widespread in concrete structures. Inducedcorrosion of reinforced in the concrete structures and causing cracking or spalling of concretecover, it is an important factor affecting the durability of concrete structures. Carbonationdepth is a quantitative targets to determine the degree of carbonation of concrete.The process of concrete carbonation is affected by the mechanism of physical andchemical. Through the carbon dioxide gas’s physical diffusion, Chemical reaction between analkaline substance and concrete in the liquid phase of concrete pore. At present, domestic andforeign scholars analyze the mechanism of carbonation of concrete in the different point ofviews. Proposing the forecasting carbonation depth model. Its basically the same conclusions:The square root of the depth of carbonation of concrete carbonation time. Diffusioncoefficient carbonization process can be measured by theoretical analysis or data fittingobtained. In the numerical model, theoretical models such as the use of the diffusioncoefficient, the diffusion coefficient is a constant, resulting in a larger prediction error. Takeappropriate fit of empirical models obtained by the lack of support for the theory. Therefore, itis necessary to establish a numerical model to explore the theoretical basis and adapt itsdiffusion coefficient calculated carbonization process.This paper summarizes the theory from the domestic concrete carbonation predictionmodel. Through the mechanism of carbonation of concrete analysis. It is determining to usethe equations of Fick’s second theorem in get the carbonization process numerical models.Adopt zoning and ordinary concrete surface layering method to determine the diffusioncoefficient, is about concrete hardened cement paste and aggregate into two parts, todetermine the diffusion coefficient from different levels in the depth direction. To solve theproblem of carbon dioxide diffusion in concrete provides a new approach. the followingconclusion can be get:(1) Establishing a process by analyzing existing carbonation depth prediction model todetermine the numerical equations carbonation model of this article. Because concretecarbonation physical chemistry together, but in terms of the occurrence rate of the chemicalreaction is much higher than the physical diffusion, so the equation is to consider only the physical diffusion, diffusion depth of carbon dioxide is determined to represent the overalldepth of carbonation. As the gas hole in the concrete structure, mostly in the form of Fick’sdiffusion-based, so the application Fick’s second law of diffusion equations to derivenumerical model.(2) To achieve the establishment of their numerical model to ordinary concrete, forexample, to determine the ordinary concrete carbonation model diffusion coefficient. Inordinary concrete can reflect the proliferation of the four indicators (water-cement ratio, theamount of cement, sand ratio and compressive strength), the use of mathematical statistics,path analysis to find the main factors for cement ratio.(3) The water-cement ratio as the main factors to consider in concrete aggregatedistribution, the proposed the method of partition and layered to determine the diffusioncoefficient, is that divide concrete into two parts, hardened cement paste and aggregate.Determining the diffusion coefficient in the depth direction from different level.(4) Binding assay for ordinary concrete numerical model established for verification.Since the analysis of transient heat conduction model with similar problems, so the use offinite element software ANSYS simulation. There are some relationship between simulationand test data, it confirmed the feasibility of this numerical model to some extent.