Chloride binding behaviors and early age hydration of tricalcium aluminate in chloride-containing solutions.

Understanding the hydration kinetics and interactions of hydration products of cement components with chlorides is crucial for designing durable cement-based materials. The most reactive component of ordinary Portland cement (OPC), tricalcium aluminate (C 3 A), was investigated on its hydration kinetics, chloride binding behaviors and hydrated phase assemblages through multiple ex-situ and in-situ methods. The hydrated phases of C 3 A demonstrated different chloride binding isotherms in NaCl and CaCl 2 solutions at different ages. Chloride ions can suppress the formation of calcium aluminate hydrates (OH-AFm and C 3 AH 6) while calcium ions were favorable to increase the content of hydrocalumite (Cl-AFm) and regulate its crystal structure. The carbonation process deteriorated the chloride binding capacity of C 3 A pastes through producing more calcium mono/hemi-carboaluminate phases (Mc/Hc) or forming a solid solution between Mc and Cl-AFm. These findings can be used as a guide for corrosion protection design of cement-based materials. [ABSTRACT FROM AUTHOR]