Abstract:Corrosion of steel in concrete structures remains a major problem worldwide, and surfaces periodically wetted with chloride solution are particularly vulnerable. BS 8500-1 cover requirements have been calculated using the error function solution to Fick's second law of diffusion. However, the values of surface chloride content (Cs) assessed via the diffusion coefficient are rather low, suggesting the cover thicknesses may have been underestimated, which could account for the high incidence of reinforcement cor… Show more
“…The peak phenomenon of chloride profile in concretes was often attributed to effect of drying-wetting cycles on pore solution in some literatures [45][46][47]. However, we strongly believe that both carbonation and calcium redistribution or leaching play a critical role in the chloride binding behavior of pastes.…”
Section: Further Modification Of Clinconc Modelmentioning
“…The peak phenomenon of chloride profile in concretes was often attributed to effect of drying-wetting cycles on pore solution in some literatures [45][46][47]. However, we strongly believe that both carbonation and calcium redistribution or leaching play a critical role in the chloride binding behavior of pastes.…”
Section: Further Modification Of Clinconc Modelmentioning
“…Chloride distribution in concrete is very complex under cyclic wetting-drying conditions. Instead of chloride content decreasing monotonously with increasing distance from the exposed surface, a maximum phenomenon [10][11][12] has been reported by many studies [13][14][15][16][17][18], that is, chloride content first increases, reaches a climax, and then decreases. Affecting the accuracy of the service life prediction of concrete, the maximum phenomenon has gained increasing attention [19][20][21][22][23][24][25].…”
The combined action of chloride and carbonation generally accelerates chloride penetration in concrete. Plenty of studies have revealed a chloride maximum phenomenon in the chloride profiles of concrete under wetting and drying cycles, which affects the accuracy of the service life prediction of concrete structures. Carbonation is probably one of crucial factors inducing chloride maximum phenomena. To investigate the influence of carbonation on chloride distribution of concrete subjected to cyclic wetting–drying conditions, this study established a numerical model coupling carbonation effect, simulated chloride distribution at different carbonation degrees, and verified the simulation results with experimental results. The results show that a chloride peak appears in all predicted chloride profiles when carbonation effect is taken into account, and the higher the carbonation degree is, the more significant the chloride peak is. This demonstrates that carbonation can enhance the forming of chloride maximum phenomenon under cyclic wetting and drying. Moreover, the calculated results are highly consistent with the experimental results under different carbonation conditions, especially in terms of the peak chloride concentration and the corresponding depth. Furthermore, the significance degree of the chloride maximum phenomenon is closely related to some key parameters, such as CO2 concentration, environmental humidity, and temperature.
“…For example, Stewart [23] assumed that the diffusion coeffi-time to initiation of corrosion and the rate of corrosion of prestressing steel, with the crack width kept unchanged during the experiments [e.g. [11][12][13][14]. In reality, however, cracks will frequently open and close depending on the loads, and therefore it is necessary to consider this opening and closing effect.…”
There are several methods available to decide on appropriate design recommendations against corrosion of reinforcing steel in prestressed concrete bridge girders. With respect to chloride-induced corrosion, in the present study two methods are considered. The first one is based on the target probability of corrosion initiation and the initial cost. The other method is based on the life cycle cost that includes the initial cost, maintenance cost, and expected failure cost. This paper deals with the development of recommendations for durability design of structures in marine environments from the reliability point of view, taking into consideration of the life cycle cost of a structure. In order to approach the problem, the chloride diffusion coefficient of a cracked area under service load is obtained considering opening and closing motion of cracks. Utilizing the diffusion coefficient of a cracked area, the development over time of the chloride concentration at the surface of reinforcement can be predicted. This information is used to quantify probability of initiation of corrosion of prestressing steel as well as the distribution of life cycle cost.Based on the findings recommendations for durability design in various exposure environments are developed.
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