Accueil > A la une > Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

Since Le Chatelier, it is well understood that Portland cement hydration is initiated by the dissolution of calcium silicate monomers in water, followed by the precipitation of less soluble layered calcium-silicate-hydrates (C-S-H), in which silicate ions condense to form short chains. However, despite two centuries of widespread applications and a century of detailed study, the molecular mechanisms behind the kinetic stages of hydration (that is, induction, acceleration and deceleration) are still debated.
 
We used state-of-the-art time-resolved solid-state NMR to follow the hydration of 29Si-enriched Ca3SiO5 , the main constituent of cement, and to determine the transient molecular-level compositions at silicate surfaces and the interactions between silicate species, hydroxyl groups and water molecules, which influence the rates of hydration reactions.
 
The relations directly observed here for the first time between surface passivation and etching phenomena on the one hand and the succession of the induction, acceleration and deceleration stages of hydration of Ca3SiO5 on the other hand, provide new understanding for the occurrence of this complex kinetic behaviour actually observed in a variety of silicate systems. Ca3SiO5, because of its high reactivity, constitutes an interesting model for understanding long term silicate hydration processes occurring during geochemical weathering or hydrothermal synthesis.

Elizaveta Pustovgar, Rahul P. Sangodkar, Andrey S. Andreev, Marta Palacios, Bradley F. Chmelka, Robert J. Flatt & Jean-Baptiste d’Espinose de Lacaillerie
Nature Communications 7, Article number : 10952 doi:10.1038/ncomms10952