Thermodynamic evaluation of the effect of calcium carbonate on cement hydration

The use of calcium carbonate in the composition of cement compositions is considered from the point of view of its chemical ac-tivity during cement hydration. The activity of limestone (calcium carbonate) was determined from the standpoint of the thermody-namic probability of the occurrence of reactions when comparing the values of the isobaric-isothermal potential or Gibbs energy (ΔGo298) of the occurrence of reactions during cement hydration. The magnitude of the change in isobaric-isothermal potentials was found by calculating the ∆G = f(T) reactions in silicate systems based on known thermodynamic data. The values of the isobar-ic-isothermal interaction potential of calcium carbonate with cement minerals during its hydration and crystalline hydrates formed in this process are calculated. The possibility and preference of chemical reactions in cement compositions with calcium carbonate during cement hydration are analyzed. By the magnitude of the isobaric-isothermal potential ΔGo298, the degree of nonequilibrium of one or another reaction was estimated in real conditions. The thermodynamic assessment of the effect of calcium carbonate on cement hydration made it possible to substantiate the manifestation of the chemical activity of calcium carbonate when cement was added to the composition. The formation of calcium hydrocarboaluminate in cement compositions with limestone and the possibil-ity of the formation of calcium hydrosilicates of different compositions in such compositions are theoretically justified. The theo-retical conclusions made allow us to determine further experimental studies in cement compositions with calcium carbonate.