Measurement and simulation of the dissolution rate at room temperature in conditions close to a cement paste: from gypsum to tricalcium silicate

Abstract

Measurement and simulation of the dissolution rate at room temperature in conditions close to a cement paste: from gypsum to tricalcium silicateThe measurement of the dissolution rate was performed in conditions close to a cement paste; thanks to a specifically designed experimental device that was calibrated with gypsum. For tricalcium silicate (C 3 S) dissolved in several electrolytes at room temperature, it appeared that the average dissolution rate of C 3 S was modified with some relatively small concentrations of electrolytes. The strongest effects corresponded to the inhibiting effects of hydroxide and calcium ions that were taken into account to simulate the dissolution rate of C 3 S using Lasaga's equation. Compared to dissolution experiments in saturated portlandite solution during which hardly any dissolution of C 3 S occurred for several hours, the reported simulations tend to be an indirect proof in favor of the existence of an additional mechanism that restricted further the dissolution of C 3 S. This mechanism is expected to be related to the very rapid formation of thin layer composed of intermediate phase around C 3 S grains.

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“…13), as linked to the undersaturation and [H + ] abundance in solution which steps as 10 À4 < 10 À7 < 10 À10 for pHs ranging from 4 (acidic) to 7 (neutral) to 10 (caustic). Interestingly, the measured dissolution rates of alite at different pHs levels are of the same order of magnitude and in reasonable agreement with those measured by Damidot et al, Nicoleau et al, and those estimated by Juilland et al 36,[49][50][51] for both the triclinic and monoclinic polymorphs. While it must be clarified that each of the prior efforts measured dissolution using methods which are distinct from each other, and this study, and are thus not "perfectly comparable"-each of the prior determinations present a means of deriving dissolution rates of C 3 S polymorphs on contact with an aqueous phase.…”

“…), as linked to the undersaturation and [H + ] abundance in solution which steps as 10 −4 < 10 −7 < 10 −10 for pHs ranging from 4 (acidic) to 7 (neutral) to 10 (caustic). Interestingly, the measured dissolution rates of alite at different pHs levels are of the same order of magnitude and in reasonable agreement with those measured by Damidot et al ., Nicoleau et al ., and those estimated by Juilland et al . for both the triclinic and monoclinic polymorphs.…”

“…In addition to procedural, instrumental differences, and also synthesis-based differences, it should be noted that the composition of the solvent used (i.e., the types and concentrations of ions) may lead to ion specific interactions. [50][51][52] These interactions can influence phase dissolution such that some level of difference in phase dissolution rates is expected for solvents having equivalent pH but different compositions, as reported in elsewhere. 50 Broadly, the first-order effect which influences undersaturations (and phase dissolution) is the solution pH.…”

“…though less than perfect, are a reasonable means of comparing the dissolution response of the different C 3 S polymorphs obtained using different techniques. In addition to procedural, instrumental differences, and also synthesis‐based differences, it should be noted that the composition of the solvent used (i.e., the types and concentrations of ions) may lead to ion specific interactions . These interactions can influence phase dissolution such that some level of difference in phase dissolution rates is expected for solvents having equivalent pH but different compositions, as reported in elsewhere …”

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“…Equation 11) but once obtained, it is possible to estimate the dissolution rate depending on the different properties of the system. The equation of tricalcium silicate dissolution at 258C and 1 Atm can be written as (Damidot and Bellmann, 2008) dC 3 S dt (mmol:L À1 :s À1 :m À2 )…”