EXPERIMENTS ON CHLORIDE ION PENETRATION INTO HARDENED CEMENT MATRIX

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The transfer of chloride ion in hardened cement matrix is related not only to their diffusion due to the gradient of concentration but also to the fixation of ion to the micro structure of the hardened cement matrix.In this study cement paste specimens were immersed in salt water and the total chloride ion content of cement paste and the distribution of the chloride ions in the pore solution were measured in order to obtain the necessary data for establishing a numerical model representing the transfer of chloride ion in hardened cement matrix and the phenomena of concentration and fixation of chloride ion.The findings of the tests concerning the transfer of chloride ions in cement paste may be summarised as follows.1) The total chloride ion content increases as the water cement ratio decreases near the specimen surface, and increases as the water cement ratio increases in the inner sections.2) Thickening of the chloride solution is observed in pores, with the pore solution chloride ion content being higher than the salt water concentration in the surface layer of specimens with low water cement ratio immersed in 1 to 3% salt water. At a salt water concentration of 10%, on the other hand, the penetration of the chloride ions is checked, making the pore solution chloride content lower than the salt water concentration.3) When the water-cement ratio is high, the fixed chloride ion content tends to be smaller near the surface than inner sections.