INFLUENCE OF ETIDRONIC ACID AND ITS SALTS ON THE CURING GYPSUM PROCESS
The influence 1-Hydroxyethane 1,1-diphosphonic acid (etidronic acid) and its disodium and tetrasodium salts on the gypsum curing process. The concentration dependence of the inhibitory effect of acid and its salts in the concentration range of 0.0008-0.025 mol/L was studied. In the course of the experiment revealed that etidronic acid and its salts showed pronounced inhibiting effect on the curing process of the plaster. As expected, the inhibitory activity increases with increasing concentration of solutions up to the studied concentration of 0.025 mol/L. All studied compounds showed activity with respect to both the beginning and end of solidification of gypsum, comparable to the activity of sodium citrate in the same concentrations. With respect to the start time of solidification at high concentrations (above 0.01 mol/L), the activity of disodium salt exceeds that of sodium citrate. And with respect to the end of solidification, the tetranatric salt is slightly more active than sodium citrate at the highest studied concentration (0.025 mol/L). Solutions with a higher concentration were not studied, since already at a concentration of 0.025 mol/L or higher, the strength characteristics of the obtained samples were observed to deteriorate. The most optimal from a practical point of view, it should obviously be considered a range of concentrations of 0.005-0.01 mol/L for both the etidronic acid itself and its salts.