Performance of Superpave Mixtures Under Accelerated Load Testing

The performances of two Superpave® test sections, constructed with 12.5 mm (0.5 in.) nominal maximum size Superpave mixture (SM-2A) with varying percentages of river sand at the Kansas Accelerated Testing Laboratory (K-ATL), are described. A 150-kN (34-kip) tandem axle with dual wheels and 620-kPa (90-psi) tire pressure was used for loading. After 10,000 repetitions, the sections were loaded by 160-kN (36-kip), 150-kN (34-kip), and 144-kN (32.5-kip) tandem axles and 98-kN (22-kip), 90-kN (20-kip), and 80-kN (18-kip) single axles, for estimating relative pavement damage due to different axle loads and configurations. Critical pavement responses were measured on each test section with the transverse strain gauges and soil pressure cells under both K-ATL tandem axle and falling weight deflectomter (FWD) loads. The pavement responses were also estimated from a multilayer elastic analysis program, ELSYM5. Laboratory fatigue tests were conducted on the SM-2A beams. Fatigue and rutting damage analyses were then conducted. The results indicated very little fatigue damage on these sections. The Superpave mixtures appeared to be less susceptible to fatigue damage, presumably due to better aggregate structure and higher binder content than the traditional asphalt mixtures. Rutting on the section with 15 percent river sand was mainly due to consolidation of the SM-2A and/or other layers since no significant flow of the Superpave mixture was evident. The AASHTO load equivalency factors were found to be much higher than those calculated in this study.