Basically, the type of aggregate mix, the type and content of binder, and the amount of air voids (Va), voids in mineral aggregate (VMA), voids filled with binder (VFB) are taken into account when analyzing the resistance to deformation of an asphalt mixture course. The development of rutting is a fairly complex process depending on, among other things, the relationships among the three aforementioned factors. Hence the resistance to deformation depends on the shear strength of an asphalt mix (Kandhal et al., 1998), which is the result of binder and aggregate (aggregate blend) interactions.
With mixtures like SMA, it would seem to be a justified statement that with such a strong aggregate structure, the role of the binder should be substantially reduced. However, practice has proved that functionally better binders like polymer modified binder (PMB) or multigrade binders are being used in more and more countries. They provide for better cohesion at high service temperatures and also improve pavement characteristics (e. g., crack resistance) at low temperatures.
Resistance to deformation has been tested for many years. Many assessment methods have been developed, from the simplest and the oldest ones like an assessment based on Marshall stability, through the so-called Marshall quotient (the ratio of stability to flow), to sophisticated up-to-date test methods including triaxial dynamic compression and shear machines.
Next, the following test methods will be discussed:
• Creep tests with constant and repeated loads
• Triaxial dynamic compression test
• Wheel-tracking test
• Asphalt Pavement Analyzer (APA)
