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Most design methods for road pavements require the design traffic, based on the transformation of the traffic spectrum, to be calculated into a number of equivalent passages of a standard axle using the equivalent axle load factors (EALFs). In general, these factors only consider the type of axle (i.e. single, tandem or tridem), but they do not consider the type of wheel on the axles, i.e. single or dual wheel. The type of wheel has an important influence on the calculation of the design traffic. The existing design methods assume that the EALFs are valid for all pavement structures and do not consider the thickness and stiffness of the pavement layers. This paper presents the results of the development of a model for the calculation of the EALFs considering the type of axle, the type of wheel and the constitution of the pavement. The model was developed based on the tensile strain at the bottom of the asphalt layer that is responsible for bottom-up cracking in asphalt pavement, which is the most widely considered distress mode for flexible road pavements. The work developed in this study also presents the influence of the type of wheel (single and dual) on pavement performance. The results of this work allowed the conclusion that the EALFs for single wheels are approximately 10 times greater than those for a dual wheel. This work also proposes average values for the EALFs. An artificial neural network was developed to calculate the EALFs.

Bituminous mastics are a blend of bitumen and the finest mineral particles which have the role of filling the voids created by the coarse mineral aggregates. The rheological properties of the mastic phase have a determinant effect on the mechanical behavior of the whole asphalt and can be evaluated in the light of tests recently developed for pure and modified bitumens. The objective of this research is to evaluate the effects of different filler/bitumen ratios and two bitumens grades (50/70 and 30/45) on rheological properties of bituminous mastics associated with permanent deformation and fatigue cracking. The original samples were subjected to short-and long-term ageing according to standard procedures using a rolling thin film oven and a pressure ageing vessel. The short-term aged samples were submitted to the MSCR test and the long-term aged samples were submitted to the LAS test. The MSCR test was performed at 52, 58, 64, 70 and 76°C in order to cover a wide range of temperatures where permanent deformation can occur. The LAS test was run at 25°C, which is a typical temperature where fatigue cracking appears in the asphalt. The overall conclusions are: (i) the filler/bitumen ratio are responsible for an expressive increase in the resistance of the asphalt to the accumulation of plastic deformations and these positive effects are more expressive when a harder bitumen is used; (ii) in the light of the af parameter, obtained from the fracture mechanics, the harder the bitumen and the higher the f/b ratio, the higher the tolerance to fatigue damage of the mastics, but, on the other hand, the fatigue life curves, obtained from the continuum mechanics, indicated the opposite, i.e., the harder the bitumen and the higher the f/b ratio, the lower the fatigue life of the mastics. The analysis based on the fatigue parameter of the Superpave specification (G*.sin) is in tune with the results obtained from the analysis of the fatigue life curves.