Solubility and structure of calcium silicate hydrate

Abstract

C-S-H, the poorly crystalline calcium silicate hydrate formed in cement paste and aqueous suspension, is characterized by extensive disorder and structural variations at the nanometer scale. An analysis of new and published solubility data for C-S-H formed by different preparation methods and with a broad range of compositions illustrates a previously unrecognized family of solubility curves in the CaO-SiO 2 -H 2 O system at room temperature. As demonstrated by 29 Si magic-angle spinning (MAS) NMR data and by charge balance calculations, the observed differences in solubility arise from systematic variations in Ca/Si ratio, silicate structure, and Ca-OH content. Based on this evidence, the family of solubility curves are interpreted to represent a spectrum of metastable C-S-H phases whose structures range from purely tobermorite-like to largely jennite-like. These findings give an improved understanding of the structure of these phases and reconcile some of the discrepancies in the literature regarding the structure of C-S-H at high Ca/Si ratios.

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

“…The experimental data of (Greenberg and Chang, 1965) was used to calibrate the model, and the applicable range of C/S ratio is between 0 to 1.7. (Carey and Lichtner, 2006) proposed a non-ideal binary solid solution (S -CH) calibrated with the experimental data from (Chen et al, 2004). All these models above are able to reproduce the experimental results within the dispersion of experimental data (Soler, 2007).…”

“…It is theoretically a function of the C/S ratio, x, and the Water/Si ratio, z, as seen previously (V C-S-H is the partial derivative of g with respect to the pressure). The molar volume of C 1.7 SH 1.4 is approximately 64.5 cm 3 /mol, that of C 1.7 SH 2.1 is 78.8 cm 3 /mol and that of C 1.7 SH 4 is 113.6 cm 3 /mol (Chen et al, 2004). On the other hand that of amorphous silica un-hydrated (i.e.…”

“…The molar volume of C 1.7 SH 1.4 is approximately 64.5 cm 3 /mol, that of C 1.7 SH 2.1 is 78.8 cm 3 /mol and that of C 1.7 SH 4 is 113.6 cm 3 /mol (Chen et al, 2004). For amorphous silica gel, (Lothenbach et al, 2008) proposed t = 0 V SHt = 29 cm 3 /mol while experimental works of (Antoine Thiéry et al, 2011 suggested that t = 2 and V SHt = 43 cm 3 /mol.…”

“…Many research works have examined the structure and stoichiometry of C-S-H (Chen et al, 2004;Greenberg and Chang, 1965;Kalousek, 1952;Soler, 2007;Fujii and Kondo, 1981). The dashes in the notation¨C-S-H¨indicate that no specific composition is implied.…”

“…Thiery (Thiery, 2006) Comparing with the carbonation of portlandite, the carbonation of C-S-H is more complicated since it does not have any specific crystalline form. Many research works have examined the structure and stoichiometry of C-S-H (Chen et al, 2004;Greenberg and Chang, 1965;Kalousek, 1952;Soler, 2007;Fujii and Kondo, 1981).…”