Experimental study and thermodynamic modelling of the temperature effect on the hydration of belite-ye’elimite-ferrite cements
Maruša Mrak, Frank Winnefeld, Barbara Lothenbach, Andraž Legat, Matej Dolenec
Abstract
This study focuses on the kinetics of hydration, phase assemblage, microstructure and mechanical properties after various hydration times of two different BCSA cements at 5, 20, 40 and 60 °C and compares experimental data with thermodynamic modelling. Different curing temperatures change the type of hydrates and their amounts. Ye’elimite and gypsum in belite-ye’elimite-ferrite cements are almost fully reacted after 24 h of hydration at 20, 40 and 60 °C, while not at 5 °C. The hydration of belite is slower than the one of ye'elimite, but reaches a high degree of hydration after 150 days which is increasing with temperature. Less ettringite is present at elevated temperatures due to its increasing solubility, while more monosulfate is observed. Furthermore, with increasing temperature siliceous hydrogarnet forms at the expenses of strätlingite as well as more C−S−H is found as more belite reacts resulting in higher compressive strength. Dense and homogenous microstructure is observed at 5 °C, while it is more heterogeneous at higher temperatures. The presence of more ye'elimite resulted in higher ettringite and strätlingite formation and a higher compressive strength, while more belite yields more C−S−H in the hydrates and lower compressive strength.