QUASI-ELASTIC NEUTRON-SCATTERING STUDY OF THE EFFECT OF WATER-TO-CEMENT RATIO ON THE HYDRATION KINETICS OF TRICALCIUM SILICATE

Quasielastic neutron scattering (QNS) measurements of the hydration ki netics of tricalcium silicate (C3S) have been made with 60 mu eV energ y resolution at a momentum transfer q = 1 Angstrom(-1). Monitoring the fraction of neutrons elastically scattered from C3S paste specimens f ollows the progress of the C3S hydration reactions. Three different wa ter/cement ratios (w/c = 0.3, 0.5, and 0.7) were studied in this exper iment. Analysis of the rate of reaction over the first approximately 1 5 h was by an Avrami model. After this time, the rate of hydration no longer follows nucleation and growth kinetics but enters a diffusion c ontrolled regime. At this point, the rate of hydration depends strongl y on the w/c, with more reaction at higher w/c ratios. A shrinking cor e model was used to analyze the diffusion-limited portion of the react ion at later times. The values of the apparent diffusion constant obta ined from these data indicate a log-linear relationship between the di ffusion constants and the w/c ratio. (C) 1998 Elsevier Science Ltd.