Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least seven days, dilatometers were manually recorded during at least 56 days. The dispersion model was applied to fit chemical shrinkage results and to estimate the maximum (or ultimate) value for calculation of degree of hydration. Except for a pure Portland cement best fits were obtained by the general form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different cement types.