Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

Abstract

Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

Molecular and submolecular scale effects of comb‐copolymers on tri‐calcium silicate reactivity: Toward molecular design

“…41,48,[81][82][83][84][85][86] However, it is also necessary to study the interaction between the different phases that might induce other reactions or kinetics as in pure phases systems. Lerch 87 and later Tenoutasse 30 illustrated in particular the importance of the balance between the silicates, the aluminates and the sulfates ( Figure SB3.2).…”

Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

“…The literature includes descriptions of slightly different hydration reactions for alite, which lead to calcium silicate hydrate gels with slightly different densities and compositions [5][6][7][8]. Here, we have chosen the Ca-to-Si average ratio of 1.8, because it is compatible with many previous reports, which gave values ranging from 1.7-2.0.…”

Advances in dissolution understanding and their implications for cement hydration

“…Advances in geochemistry helped support the notion that typical pore solutions are indeed close to the apparent experimental solubility of alite, explaining why its dissolution rate drastically decreases few seconds/minutes after the first contact with water. In parallel, it was observed that protonation of silicate monomers and free oxygen atoms strongly stabilize alite surface and reduce its solubility [30,50]. As mentioned earlier, the surface bonding of ions [33,51] or the adsorption of polymers [42] also stabilize the alite surface and in turn extend the dormant period.…”