Molecular insight into the initial hydration of tricalcium aluminate

作者：Xing Ming, Wen Si, Qinglu Yu, Zhaoyang Sun, Guotao Qiu, Mingli Cao, Yunjian Li, Zongjin Li · 发表于：Nature Communications · 年份：2024 · DOI：10.1038/s41467-024-47164-0 · 被引用次数：45 · 研究领域：Concrete and Cement Materials Research、Calcium Carbonate Crystallization and Inhibition、Magnesium Oxide Properties and Applications

Abstract Portland cement (PC) is ubiquitously used in construction for centuries, yet the elucidation of its early-age hydration remains a challenge. Understanding the initial hydration progress of tricalcium aluminate (C 3 A) at molecular scale is thus crucial for tackling this challenge as it exhibits a proclivity for early-stage hydration and plays a pivotal role in structural build-up of cement colloids. Herein, we implement a series of ab-initio calculations to probe the intricate molecular interactions of C 3 A during its initial hydration process. The C 3 A surface exhibits remarkable chemical activity in promoting water dissociation, which in turn facilitates the gradual desorption of Ca ions through a metal-proton exchange reaction. The dissolution pathways and free energies of these Ca ions follow the ligand-exchange mechanism with multiple sequential reactions to form the ultimate products where Ca ions adopt fivefold or sixfold coordination. Finally, these Ca complexes reprecipitate on the remaining Al-rich layer through the interface-coupled dissolution-reprecipitation mechanism, demonstrating dynamically stable inner-sphere adsorption states. The above results are helpful in unmasking the early-age hydration of PC and advancing the rational design of cement-based materials through the bottom-up approach.