Improving the structural consistency of C-S-H solid solution thermodynamic models

Simple aqueous-solid solution models of C-S-H (calcium silicate hydrate) are widely used in studies of cement hydration and waste-cement interactions. Even without a clear structural/mechanistic basis, such thermodynamic models yield a good description of solubility data in [Ca]-C/S space, while only satisfactory in [Si]-C/S, H2O-C/S, [Ca]-[Si] spaces and in the 0.1 1.5, CSHQ end members were downscaled to one tetrahedral site and used within the simple mixing model. Despite some loss of structural consistency, the solubility and mean silicate chain length data can be reproduced well with this downscaled CSHQ model, capable of temperature corrections and dependencies of density and water content in fully-hydrated C-S-H on C/S ratio. Most literature solubility data sets can be modeled at the cost of moderate adjustments of CSHQ end-member solubility products within 0.2 to 0.6 pK units. (C) 2011 Elsevier Ltd. All rights reserved.