Test Results

A significant impact of mixture type on cracking temperature for newly made mixtures or after a short time of aging has not been observed with TSRST test­ing mixtures of AC, SMA, and porous asphalt (Isacsson et al., 1997). Not until a longer aging period (i. e., more than 25 days) has elapsed has a difference in favor of AC and SMA been observed. Porous asphalt is more susceptible to aging, and the recorded difference of crack temperatures has reached 6°C and 25°C after 25 and 100 days of aging, respectively. Test results (Judycki and Pszczola, 2002) con­cerning a comparison of low temperature properties of various mixtures have not revealed essential differences between AC and SMA. In a U. S. site investigation (Schmiedlin and Bischoff, 2002), the comparison of capabilities to slow down the advancement of reflective cracking in various mixtures concluded that SMA is superior to AC. The impact of aggregate size and its resistance to crushing has also been noted. Those conclusions are based on a 5-year observation of test sec­tions. Similar results have been achieved on a test section in Australia (Pashula, 2005) where, among other things, the abilities of various mixtures to slow down the advancement of reflective cracking were compared. It was stated after a 10-year observation that SMA’s distinctive feature is that it possesses the greatest potential of slowing the occurrence of reflective cracking.