INVESTIGATING THE RELATIONSHIP BETWEEN HEAT OF HYDRATION AND PHYSICO-MECHANICAL PROPERTIES OF CALCIUM SULFATE HEMIHYDRATE IN THE PRESENCE OF ADDITIVES

This article addresses the interplay between heat of hydration and physico-mechanical properties of calcium sulfate hemi-hydrate in the presence of retarding additives such as citric and malic acids and sodium citrate. The heat of hydration was measured using a semi-isothermal calorimeter. Results proved that citric and malic acids had superior impact on hydration and mechanical properties. While the concentration of additives was increasing, the maximum heat of hydration was decreasing from ۵۶.۱۵ cal/g.min for blank sample to ۳۳ cal/g.min for high concentrations of citric and malic acids. Consequently, the measured time to this maximum heat of hydration and thus the induction period were increased significantly from ۵ to ۱۰۵ min. Mechanical results indicated that the increase in the amounts of additive led to the reduction of the compressive strength from ۱۶.۲۵ MPa in the blank sample up to ۷۴% for the highest concentration of malic acid

کلیدواژه ها:

Calcium sulfate ، Additive ، Setting time ، Isothermal calorimeter ، Compressive strength