Reactivity of Different Crystalline Surfaces of C₃S During Early Hydration by the Atomistic Approach

Early hydration of tricalcium silicate (C₃S) has received great attention over the years due to the increased use of composite cement with a reduced number of clinker phases, especially the addition of what should be very reactive C₃S to guarantee early strength. Although many mechanisms have been proposed, the dissolution of polygonal C₃S at the material interface is not yet fully understood. Over the last decade, computational methods have been developed to describe the reaction in the cementitious system. This paper proposes an atomistic insight into the early hydration and the dissolution mechanism of calcium from different crystalline planes of C₃S using reactive force field (ReaxFF) combined with metadynamics (metaD). The reactivity and thermodynamic stability of different crystal planes were calculated from the dissolution profile of calcium during hydration at 298 K. The simulation results, clearly describe the higher reactivity of ( 0 1 ¯ 1 ¯ ), (011), (100), and ( 1 ¯ 00 ) surfaces of C₃S due to the strong interaction with the water, whereas, the dissolution profile explains the lower reactivity of ( 1 ¯ 1 ¯ 0 ), (110), ( 0 1 ¯ 0 ) and the effect of water tessellation on the (001), (010) planes.