A STUDY OF THE HYDRATION OF ALUMINATE MINERALS BASED ON THE MEASUREMENTS OF THE MEAN AND THE VARIANCE OF THE PROTON MAGNETIC-RESONANCE RELAXATION RATE

Mean longitudinal proton relaxation rates and their variances were mea sured in hydrated mono- and tricalcium aluminates. The results were an alysed using a two-site model of bulk and adsorbed water. A formalism for the calculation of the fractions of water in these states and of t he relaxation rate in adsorbed state was developed. A significant rele ase of water from the adsorption layer occurred at about 400-500 min a fter hydration of the monocalcium aluminate. The relaxation rate of wa ter protons in the adsorbed state increased continuously during the ce ment hydration (up to 1200 min). During the induction period this incr ease is attributed to the growing viscosity of the bulk liquid and to the nucleation. During the later stages of hydration the rate increase is explained by the diminishing number of adsorption layers. The maxi mal values of the relaxation rate in the adsorption layer of monocalci um aluminate indicated the monomolecular adsorption. The hydration of tricalcium aluminate was characterised by higher initial and lower fin al (t(hydr) = 1100 min) values of the relaxation rate in the adsorbed state, After about 500 min of hydration the fraction of adsorbed water molecules and the relaxation rate in the adsorbed state reach a maxim um.