Abstract
Copious studies have discovered a phenomenon that a chloride concentration peak appears on the surface of concrete under cyclic drying-wetting environments. In such cases, the chloride diffusion coefficient (D) obtained through directly fitting the standard error function of Fick’s second law is no longer accurate. The more reliable D obtained by the method proposed by Andrade is employed in this research to investigate the influence of pore structure on chloride penetration rate of pastes. The results show that both the effective coefficient (Deff) and the apparent coefficient (Dapp) increase with total porosity, the most probable pore size, and water absorption porosity, suggesting that the increase of the three pore structure parameters accelerates chloride penetration rate under cyclic wetting-drying condition. The increase of the three parameters makes more room available and eases the difficulty for salt solution to enter the matrix and thus leads to the augmentation of chloride transporting in matrix.
Highlights
Steel corrosion induced by chloride attack is a major causation for the deterioration of concrete structures.erefore, the exploration of chloride penetration rate is of great significance for the safety and durability of concrete structures. e chloride penetration rate of concrete can be represented by the chloride diffusion coefficient, which is usually obtained through fitting the chloride profile
Erefore, the exploration of chloride penetration rate is of great significance for the safety and durability of concrete structures. e chloride penetration rate of concrete can be represented by the chloride diffusion coefficient, which is usually obtained through fitting the chloride profile
The diffusion coefficient (D) obtained through directly fitting standard error function solution of Fick’s second law (equation (1)) is no longer accurate after chloride concentration peak appears since the phase of chloride content increasing with depth (0∼Δx, shown in Figure 1) does not conform to the diffusion law
Summary
Steel corrosion induced by chloride attack is a major causation for the deterioration of concrete structures. Is will allow development of technology to control that peak through manipulation of the pore structure with some specific products and to obtain more reliable service life prediction models To look for such a pore structure, it is necessary to reproduce the situation at laboratory and at a basic level (i.e., cement pastes) but to follow a reliable procedure to make reasonable calculations. Few researches have investigated the influence of pore structure on the chloride penetration rate using this method when a chloride concentration peak occurs under cyclic wet-dry condition. To investigate the influence of pore structure on the chloride penetration rate in cases that chloride concentration peaks appear, paste specimens with different water-tocement ratio (w/c) were exposed to cyclic wetting and drying conditions. Pore structure and moisture distribution of different specimens were tested, and their influence on chloride diffusion coefficient was explored
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