Adsorption and Desorption of Chloride Ion in Carbonated Portland Cement Powder and Pastes

• Main Authors: Zhen-Zhi Li, 李振誌
• Other Authors: Chun-Tao Chen
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/yev95p

碩士 === 國立臺灣科技大學 === 營建工程系 === 107 === This study explores the factors influencing the release of the chloride ion in the Portland cement, including the chloride content in cement, amount of foreign chloride ion, hydration, carbonation and so on. The ratios of the released chloride ion and the ratio of the free chloride ion concentration to the hydroxyl ion concentration in the pastes were calculated. During the study, the domestic commercial Portland cements were collected and their compositions were determined. The ones with high, medium, and low Cl-/C3A ratios were selected. Results showed that the release of the chloride ion was increased with the chloride contents in the cements. The release was high when the w/c was reduced. For the cement powders, both the hydration and carbonation reduced the release. For the cement pastes, the curing reduced the release, but the carbonation increased the release, in contrast to the release in the cement powders. The ratio of the chloride ion concentration to the hydroxyl ion concentration was found mostly influenced by hydroxyl ion concentration. The microstructural analyses showed that the Friedel’s salt was formed by the chemical bonding of the chloride ions. The salt was decomposed and released the bound chloride under carbonation. At this time, the free chloride ions were increased, the pH was reduced and lower than 9, and the ratio of the chloride ion concentration to the hydroxyl ion concentration was much more than 0.6, thereby possibly inducing reinforcement corrosion.