Laying of warm mix asphalt: Study of the feasibility of the workability measure modifying the parameters of the standard Gyratory shear compactor

Abstract

The development of Warm Mix Asphalt (WMA) created a workability issue on road site, which did not exist or was not as noticeable in the case of conventional Hot Mix Asphalt (HMA), especially during manual laying. The study presented in this paper is an experimental project carried out by the French ESTP (Ecole Spéciale des Travaux Publics) in partnership with Eurovia, to complete a PhD thesis being written on the workability of Warm Mix Asphalt. It aims to change some conventional parameters of classical road laboratory equipment by means of the Gyratory Shear Compactor test (vertical strength and rotation speed) to characterize and evaluate the workability of asphalt mixes, and particularly of Warm Mix Asphalt. Some Nynas workability device tests will also be carried out for the sake of comparison. This paper will explain the choice of the new parameters in terms of the capacity of the equipment. It will also present the results of the experimental study carried out on a classic asphalt formula (a semi-coarse asphaltic concrete 0/10), varying the temperature, the presence of a WMA additive and the bitumen grade, to create mixes of really different workabilities. It will show that the GSC, even set with lower parameters, is not able to characterize workability properties of asphalt mixtures.