Hydration of cement pastes with calcium carbonate polymorphs

Three anhydrous calcium carbonate polymorphs including calcite, aragonite and vaterite were synthesized in laboratory conditions and characterized comprehensively with various analytical techniques to determine their morphologies, particle size distribution, specific surface area, chemical bonding and phase compositions. The influence of these polymorphs on the compressive strength, hydration kinetics and phase assemblages of cement pastes were investigated experimentally, along with thermodynamic modelling which provided additional insights into the phase compositions of the systems at equilibrium. Cement pastes with the polymorphs showed comparable strength, but different degrees of accelerating effect on cement hydration. Metastable aragonite and vaterite were found to be stable in the cement systems even after a prolonged age, and thermodynamic modeling revealed that this caused slight changes in the optimal replacement level and phase assemblages. The stabilization of aragonite and vaterite have significant implications for their usages in cement systems depending on the intended applications.