Quasielastic 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 kinetics of tricalcium silicate (C3S) have been made with 60 mu eV energy resolution at a momentum transfer q = 1 Angstrom(-1). Monitoring the fraction of neutrons elastically scattered from C3S paste specimens follows the progress of the C3S hydration reactions. Three different water/cement ratios (w/c = 0.3, 0.5, and 0.7) were studied in this experiment. Analysis of the rate of reaction over the first approximately 15 h was by an Avrami model. After this time, the rate of hydration no longer follows nucleation and growth kinetics but enters a diffusion controlled regime. At this point, the rate of hydration depends strongly on the w/c, with more reaction at higher w/c ratios. A shrinking core model was used to analyze the diffusion-limited portion of the reaction at later times. The values of the apparent diffusion constant obtained from these data indicate a log-linear relationship between the diffusion constants and the w/c ratio. (C) 1998 Elsevier Science Ltd.