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, 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 depending on 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 satisfactorily during service conditions. A new device, the rotary wheel tester, has been developed to evaluate the rutting and stripping performance of HMA mixes. This device operates on a principle similar to that of the Hamburg wheel tester: the main difference is that 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 whether the rotary wheel tester could distinguish between good- and poor-performing mixes and to determine whether PG 76-22 or PG 67-22 plus hydrated lime improved mix performance. Results indicate that the rotary wheel tester is an easy-to-use testing device that appears to provide reasonable prediction of the rutting and stripping performance of HMA mixes. It also appears that PG 76-22 asphalt binder improves mix performance to a greater extent than does PG 67-22 plus hydrated lime.
Abstract