Test Results

Rutting resistance is one of the most widely tested properties of asphalt mixes, including SMA, and various methods of testing are conducted all over the world.

The impact of side support during creep tests of SMA and AC have been com­pared in Swedish research (Said et al., 2000). Results have explicitly shown the great significance of that feature to SMA, while the results from testing AC with and without side support have not changed considerably (Figure 12.3). Other research (Ulmgren, 1996) on the comparison of the dynamic creep test (RLAT 100/100 mm) and the modified one (IRLAT 100/150 mm) with the results of a wheel-tracking test have demonstrated a very good relationship between IRLAT and the wheel-tracking test, with R = 0.91, while the relationship between RLAT and the wheel-tracking test was much worse, with R = 0.36.

U. S. research (Cooley and Brown, 2003) on SMA mixtures used for thin wearing courses has proved the advantages of conforming with requirements for resistance

to deformation (based upon APA testing), despite the maximum gradation of the SMA not exceeding 9.75 mm. British results (Obert, 2000) concerning the com­parison of SMA with hot rolled asphalt (HRA) have confirmed a higher resistance to deformation more for the former than the latter. Other research undertaken in Finland on test sections (Kelkka and Valtonen, 2000) compared SMA with AC, graded 0/18 mm with various binders. This time SMA turned out to be the win­ner again. Polish research (Sybilski and Horodecka, 1998) has acknowledged that creep tests are not appropriate for determining SMA resistance to deformation and also that better SMA rutting resistance has been proved in comparison with AC on road sections and in wheel-tracking testing (large device—French LCPC type).

Briefly, to sum up this short review of test results with regard to rutting resistance, it may be concluded that they reflect SMA’s superior properties over those of AC.