Performance Evaluation of Hot-Mix Asphalt Using Rotary Loaded-Wheel Testing (05-1175)**
Shane Buchanan, APAC, Inc.
Benjamin J. Smith, Brown and Mitchell Inc.

Permanent deformation and moisture damage (i.e., rutting and stripping) are two predominant hot mix asphalt (HMA) distresses. Rutting can be caused by many factors, including stripping, all of which result in reduced HMA shear strength. Hot mix asphalt stripping evaluation is a source of significant industry discussion and debate. Transportation agencies use a number of methods to evaluate stripping, with many methods customized by agencies depending upon local concerns and environmental conditions. Today, many agencies use some type of loaded wheel testing, with associated mix “pass/fail” criteria, as part of the mix design acceptance procedure. This process is often referred to as “proof” testing and provides a higher confidence that the HMA mix will perform satisfactory during service conditions. A new device, the rotary wheel tester, has been recently developed to conduct rutting and stripping performance evaluation of HMA mixes. This device operates on a similar principle as the Hamburg wheel tester, with the main difference being the specimen is loaded along its diameter instead of from the top. The cost of the rotary wheel tester is less than half that of the Hamburg wheel tester. Testing was conducted to determine if the rotary wheel tester could distinguish between good and poor performing mixes and to determine if PG 76-22 or PG 67-22 plus hydrated lime improves mix performance. Results indicate the rotary wheel tester is an easy to use testing device that appears to provide reasonable prediction of rutting and stripping performance of HMA mixes. It also appears that PG 76-22 asphalt binder improves mix performance to a greater extent than PG 67-22 plus hydrated lime.