Hydration Characteristics of High Chloride Cement

Abstract

High-chloride cement, enriched with calcium chloro aluminate (CCA), a compound of CaO-Al<sub>2</sub>O<sub>3</sub>-CaCl<sub>2</sub>, displays a higher Cl content than ordinatry portland cement. This specialized cement, incorporating limestone, clay, siliceous materials, and Cl-abundant cement kiln dust, is known for its superior early strength, making it an attractive option for resource recycling. However, the excessive Cl content can lead to reinforcement corrosion and a decrease in the durability of the hardened cement paste. Current research has primarily focused on its manufacturing characteristics, with studies on hydration reactions for practical application remaining limited. This study aims to explore the hydration reactions of high-chloride cement to determine its practicality. The experimental results reveal that high-chloride cement with abundant CCA significantly promotes the formation of ettringite, an Al-based hydrate, in the initial hydration stages. This process results in the binding of leached Cl ions with monosulfate, forming Friedel’s salt. Although the early formation of expansive hydrates might negatively affect long-term durability, mixing this cement with ordinary Portland cement in appropriate amounts can improve workability and enhance early strength and setting. Furthermore, the transformation of Cl ions into a crystallographically stable form like Friedel’s salt indicates a potential for safer usage, especially in reducing risks such as reinforcement corrosion.