Impacts of hexitols on the hydration of a tricalcium aluminate-calcium sulfate mixture

The effects of hexitols which are stereoisomers (d-glucitol, d-galactitol and d-mannitol) on the hydration of a tricalcium aluminate-calcium sulfate mixture with calcium hydroxide in paste were assessed and compared. The interactions of the molecules in solution and at the solid-liquid interface were studied by following the ionic and organic composition of the solution during the hydration of the mineral mixture in suspension in saturated calcium hydroxide solutions. The impact of the concentration of d-glucitol and d-galactitol on the precipitation rate of ettringite was found to be non-monotonic whereas d-mannitol always accelerates the formation of ettringite in the range of concentrations studied. Nevertheless, whatever the influence of these sugar alcohols on the precipitation rate of ettringite, they slow down the formation of AFm. Moreover, these organic molecules were found to complex with ions in solution and to adsorb on both ettringite and AFm but to different extent depending on their stereochemistry.