Pastes based on a sulfate-resistant cement, with or without silica fume, and of water/binder ratios in the range 0.25 to 0.55 have been studied. Thus, the binder phase of high-performance concrete as well as of ordinary concrete is covered. The phase composition of the unhydrated cement, and the degree of hydration of the major cement phases from 1 day to 9 months have been determined in a multi-method effort. The non-evaporable water content of the pastes and the pozzolanic activity of the silica fume are also reported. The obtained phase composition of the cement depends somewhat on which method is used for its determination. The Bogue method seems to overestimate the content of ferrite. Silica fume does not appear to influence the cement hydration, except for pastes of very low water/binder ratios where the presence of silica fume reduces the cement hydration somewhat at later ages. The various direct methods (SEM image analysis, 29Si NMR and QXDA) mostly provide similar results of the degree of hydration. In high-performance concrete as much as 50% of the original cement may remain unreacted. The degree of hydration is not well estimated by the non-evaporable water content by use of a commonly applied formula relating the non-evaporable water content to the degree of hydration. Improved coefficients are provided.