Normal stress and stress relaxation of sand asphalt mixtures are measured using a torsional rheometer. The description and the operating principle of the torsional rheometer and the measurement procedure are presented. The raw data obtained, namely the torque and the normal force, are documented for different rotation rates and loading times. Repeated experiments exhibit remarkable consistency and show that the normal force and the torque decrease with the decrease in rotation rate. The results show the necessity for developing non-linear constitutive models for asphalt mixtures. © 2004 Published by Elsevier Ltd.