Ageing of stone mastic asphalt and evaluation of cracking resistance

The influence of binder characteristics on the cracking resistance of stone mastic asphalt (SMA) wearing courses was recently investigated at the Braunschweig Pavement Engineering Centre (ISBS), Germany. Variations of SMA mixtures were produced using 7 different binder products. From the virgin and by a special procedure aged mixtures prismatic specimens were produced. Then the specimens were subjected to thermal stress restrained specimen tests, uniaxial tensile stress tests and cyclic tensile stress tests. The low-temperature-test results are shifted up to 5 K, caused by the ageing procedure. The effect of ageing on fatigue-properties depends on the temperature conditions. At low temperatures, it leads to a reduction in the endured number of load cycles to fatigue failure, whereas at the higher test temperatures they are improved. It is emphasized, that the application of suitable test conditions is of utmost importance when performing laboratory tests to characterize the mechanical properties of asphalt mixtures.