本研究主要為探討影響水泥中氯離子析出之因素，包括水泥本身含氯離子量、外加氯離子量、養護及碳化等，期間計算水泥漿體中游離氯離子析出比例和氫氧根離子濃度之比值。首先，針對國內市面上各廠牌水泥取樣進行成分分析並選擇Cl-/C3A比值高、中和低者進行後續試驗。試驗結果發現，氯離子析出量主要隨著水泥本身氯離子含量增加而增加，水灰比較低時析出量較高。水化或碳化皆減少水泥粉末的氯離子析出比例。就水泥漿體而言，養護可減少氯離子析出比例。相反地，受到碳化則增加氯離子析出比例，與水泥粉末受到碳化的趨勢相反。就氯離子濃度與氫氧根離子濃度比值變化而言，主要受到氫氧根離子濃度高低影響。微觀分析發現外加氯離子透過化學鍵結反應生成Friedel’s salt，受到碳化時，Friedel’s salt解離並釋放出游離氯離子，此時游離氯離子持續增加且pH值下降至9，而游離氯離子濃度與氫氧根離子濃度之比值遠大於0.6，可能提高鋼筋腐蝕的機率。

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.

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