Evaluation of Georgia asphalt mixture properties using a Hamburg wheel-tracking device.

PDFTech ReportGDOT Research Project No. 15-03FHWA-GA-17-1503RuttingRuts (Pavements)Asphalt mixturesAsphalt pavementsStripping (Pavements)Hamburg Wheel-Tracking DeviceAsphalt MixturesRAPTemperatureRut depthStripping Inflection PointGeorgiaUnited StatesGeorgia Institute of Technology. School of Civil and Environmental EngineeringShen, JunanKim, SungunJeong, M. MyungGeorgia Institute of Technology. School of Civil and Environmental EngineeringGeorgia. Department of Transportation. Office of ResearchUnited States. Federal Highway AdministrationUS Transportation CollectionThis study used a Hamburg Wheel-Tracking Device (HWTD) to evaluate the resistance of Georgia asphalt mixtures to rutting and stripping. It aimed to develop an HWTD test procedure and criteria aligned with GDOT\u2019s asphalt materials and mixture design. Aggregates, reclaimed asphalt pavement (RAP), and asphalt binders from four representative hot mix asphalt plants A1, A2, A3 and A4 - were selected for the test. All mixtures contained RAP. Asphalt binders of performance grade (PG) 64-22 and PG 76-22 were used, and four nominal maximum aggregate size (NMAS) Superpave mix types (25 mm, 19 mm, 12.5 mm, 9.5 mm T1 and T2), a 4.75 mm dense-graded and a 12.5 mm SMA mixtures were selected for this study. For Superpave and dense-graded mixtures, 30% RAP was used for A1 and A2 sources, and 25% RAP for A3 and A4. For SMA mixtures, 15% RAP was used regardless of source. Three temperatures of 50, 64, and 70\ub0C were selected for each asphalt mix type. In total, 216 mixture samples were made by Superpave gyratory compactor (SGC), and 216 sets were tested by HWTD. The results are as follows: 1) Rut depths were very small - less than 5 mm, even after 20,000 wheel passes at 50\ub0C and increased remarkably at the higher test temperatures; most mixtures reached 20.0 mm within 20,000 wheel passes at 70\ub0C. 2) Rut depths may reflect the influence of the type and size of the aggregates and the binders at test temperatures of 64\ub0C and higher. 3) Rut depths from the mixtures with NMAS of 25 mm and 19 mm were obviously lower than those from NMAS of 12.5 mm, 9.5 mm, and 4.75 mm. 4) Rut depths increased and stripping inflection point (SIP) decreased as the NMAS of the gradation decreased. 5) Overall, mixtures using modified binders had lower rut depths than those using unmodified binders; in addition, the rut depths of 12.5 mm SMA using modified binders was much higher than those of 12.5 mm Superpave mixtures. 6) The raw material sources of aggregate and RAP had an apparent effect on rutting and stripping performance. 7) RAP preprocessing methods during laboratory mixing\u2013 either not heating or preheating in a 110\ub0C oven for 2 hours before the RAP was mixed with the virgin aggregates and binder - affected rutting and stripping performance, regardless of temperature and mix type. 8) HWTD test procedures were proposed for evaluating Georgia asphalt mixtures