No abstract

The permanent deformation performance of asphalt concrete is strongly dependent on the rheological properties of the asphalt binder. It has been recognized that the asphalt's low shear viscosity (LSV) characterizes the mixture's rutting resistance. At the same time, the pavement temperature is one of the main factors that significantly affect the mixture performance. In this work the rutting performance of mixtures prepared with the same aggregate gradation and different binders [conventional (C), multigrade (M) and polymer modified (PM) asphalts] were evaluated by using wheel tracking tests (WTT) performed at 50, 60, 70 and 80°C; in parallel, the LSV of asphalts were measured at the same temperatures. The relationship between the asphalt's LSV and rutting, to predict asphalt mixture performance, was discussed and a criterion to consider the effect of LSV is proposed.

The relationship between the rutting performance of dense asphalt concretes and the low shear viscosity (LSV) of different asphalt binders was analysed in a previous work. A LSV limit was found for the original asphalt to prevent the rutting of the mixtures, and in addition, a model to predict the rutting performance based on the LSV of the asphalt binder was validated. With the aim of amplifying the criterion previously found, the performances of micro and stone mastic asphalt mixtures are studied in this work. Conventional, multigrade and polymer modified asphalts were used as binders. Considering that the properties of original and aged asphalts must be taken into account for a better asphalt binder characterization, LSV measurements on aged asphalts were also done in order to analyse their relationship to the mixtures rutting performance. The micro and stone mastic asphalt mixtures showed a similar behaviour as the dense grade asphalt concrete in the previous study. Regarding the control of rutting, a LSV limit of 500 Pa.s was found for original asphalts, while 2,000 Pa.s was the limit for aged asphalt binders. The model to predict the rutting performance of asphalt mixtures was amplified, incorporating both original and aged asphalt LSVs as appropriate input data.

The development of new technologies and road pavement materials require the evaluation of the asphalt mixture performance. Rutting is one of the main modes of failure of asphalt mixtures; it is typically studied at the laboratory through the wheel tracking test (WTT). Weather and traffic conditions (temperature, loads) significantly affect the pavement rutting performance. The bitumen rheological properties also have a main role in mixture rutting response; they can adequately characterized by the bitumen Low Shear Viscosity (LSV). The estimation of rutting performance appears as a useful decision tool to optimize pavement design process. This paper studies the rutting performance of asphalts mixtures utilising the WTT. The specimens were tested at different temperatures and loading levels to simulate different climatic and traffic pavement conditions. A performance estimator was developed including temperature and traffic load on the pavement, and LSV of the binder as input data.