Model Of Carbonation Depth Prediction For Fly Ash Concrete

In the general air environment, concrete carbonation is the precondition of the reinforcement corrosion. Concrete carbonation is one of main factors affecting the durability of reinforced concrete structure. The existing model of concrete carbonation is based on the theory of steady-state diffusion. The results show that the actual condition of concentration of CO₂ is declined non-homogeneously with the increase of depth. Concentration of carbon dioxide is controlled by the related to formulations of concrete porosity and the mechanism of carbonated reaction. The influence coefficients of the existing model of concrete carbonation is mainly experimental, but for no definite theoretical guidance. More studies are needed to confirm its influence coefficients.The new existing model of concrete carbonation is based on the theory of unsteady-state diffusion. The main parameter of the new model is apparent diffusion coefficient. The essence of concrete carbonation is diffusion-reaction processes. The existing model of concrete carbonation only reflects the diffusion state in the carbonated zone of concrete. Apparent diffusion coefficient can reflect not only the diffusion state in the carbonated zone of concrete and partial carbonation zone, but also carbonation reaction. According to the practical reactive conditions, the model is more convenient and useful.A lot of test data were collected and transformed under the same conditions. Study on apparent diffusion coefficient was carried out by changing only one of reaction conditions. Multi-coefficient formula for carbonation of fly ash content concrete is determined based on above methods. Through carbonization predicting on practical engineering, proving to use actually to worthy of in carbonization predicting: this model adjusts ability adaptively strongly, consider being overall in influence factors, and have good popularization using value.