The hydration of nearly pure ye'elimite with a sulfate carrier in a stoichiometric ettringite binder system. Implications for the hydration process based on in-situ XRD, 1H-TD-NMR, pore solution analysis, and thermodynamic modeling

Abstract

The hydration of synthetic ye'elimite was studied with sulfate carriers in a stoichiometric ettringite binder system. Heat flow calorimetry, in-situ XRD, 1H-TD-NMR and pore solution analysis were applied in order to gain a deeper understanding of the hydration kinetics of the system. Additionally, thermodynamic modeling was used in order to show the evolution of the pore solution in the system Ca-Al-S-H2O. The experiments showed that a first ettringite generation might be formed in a regime where CAH10, monosulfate, ettringite and AHamorphous are stable while at later points in time the ettringite is formed in a regime where AHmicrocrystalline and ettringite is stable. The different shoulders in the heat flow curve seem to arise from the recrystallization of AHmicrocrystalline and the final adjustment of the water content of the aluminum hydroxide towards AH3.