RUT DEPTH PREDICTION: A PRACTICAL VERIFICATION. SIXTH INTERNATIONAL CONFERENCE, STRUCTURAL DESIGN OF ASPHALT PAVEMENTS, VOLUME I, PROCEEDINGS, UNIVERSITY OF MICHIGAN, JULY 13-17, 1987, ANN ARBOR, MICHIGAN

This paper presents the contribution of the ESSO Research Centre at Mont-Saint-Aignan (France) to an overall research program monitored by the Road Engineering Division of the Rijkswaterstaat. Two test overlays of asphaltic concrete were built in 1978 on National Highway No. 28 in The Netherlands. The main objective of the program was to check the ability of various design methods to predict the behavior of the test sections. Within the framework of ESSO Road Design Technology, the rutting behavior of bituminous mixes is assessed by means of a specifically designed dynamic creep test. When recorded against the number of load cycles, the axial permanent deformation of the specimen shows a rapid initial growth followed by a steady creep rate regime. Rut depth prediction is derived from computed stresses and temperatures and with reference to the creep curves obtained at laboratory under various state of stress and temperature conditions. In the usual ERDT rutting subsystem, initial creep is not taken into account. All the bituminous layers are supposed to be in a "linear phase" of creep. Calculations are thus simplified but provide only the rut depth evolution after the first period of rapid deformation. In this particular case, this was not sufficient as the short time elapsed since the overlay construction conferred a key role to the initial creep in the road test analysis.