Analysis of C-S-H growth rates in supersaturated conditions

The growth rate of calcium-silicate-hydrate (C-S-H) was analyzed by following the evolution of calcium and silicon concentrations in supersaturated solutions. In these experiments, the supersaturated solution was produced by mixing a saturated calcium hydroxide solution and a solution obtained from the hydration of tricalcium silicate. A continuous decrease of the silicon concentration over time was observed during the experiments and the C-S-H formation rate was calculated from the amount of silicon that was precipitated between two consecutive analyses. The data obtained in this study demonstrate that the interfacial growth rate of C-S-H depends mainly on the supersaturation with respect to this phase, the availability of calcite as a substrate for heterogeneous nucleation and the calcium concentration in solution. A mean value of approximately 10 nmol of C-S-H per m² per second was obtained for the interfacial growth rate of C-S-H in conditions that are relevant for the hydration of tricalcium silicate.