Abstract
Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth.
Highlights
Concrete material has been used as a major construction material for over one hundred years.It becomes increasingly important for the durability of reinforcement concrete (RC) structures.Both European and Italian Standards have recently renewed their attention on the durability of RC constructions [1,2,3,4,5]
The y-axis corresponds to the carbonation speed, which is defined as the ratio that the absorptive amount of carbon dioxide in ten minutes at different initial conditions divided by the absorptive amount of carbon dioxide in ten minutes induced by diffusion when the initial full carbonation depth is 0 mm
When the carbonation depth is larger than 30 mm, the influence of turbulence intensity on carbonation becomes slightly significant
Summary
Concrete material has been used as a major construction material for over one hundred years. RC structures, carbonation is one of the major factors to cause deterioration and is manifested by lowering the pH of concrete pore solutions from 12.6 to less than 9. This will lead to destroying the steel passive oxide film. The influence of heat, moisture, coatings, carbon dioxide concentration and admixtures on carbonation process has been studied and corresponding coupled models were constructed [10,11,12,13,14,15,16,17,18]. The influence of steady wind flow and fluctuating wind flow on carbonation was studied
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