Effects of hexitols on the hydration of tricalcium silicate

The hydration of tricalcium silicate (C3S) in presence of hexitols (n-glucitol, D-galactitol and D-mannitol) which only differ by their stereochemistry was followed by using calorimetric and conductometric measurements of the pastes and of the diluted suspensions respectively. Hexitols delay the acceleration of the growth of C-S-H and enhance the quantity of C-S-H when the maximum rate of C3S hydration is reached in relation to the stereo chemistry of their hydroxyl groups: D-glucitol > D-galactitol > D-mannitol. Their relative retarding effect is shown to change depending on their sensitivity to calcium ions at pH found in cement paste. In diluted suspension in solutions representative to a cement paste, alditols are shown to retard C3S hydration whereas its dissolution is not limited suggesting an impact of the molecules on the precipitation of C-S-H. (C) 2016 Elsevier Ltd. All rights reserved.