Simple performance test for permanent deformation of asphalt mixtures

This research study had a primary objective: to recommend a fundamentally based laboratory Simple Performance Test (SPT) for permanent deformation evaluation to be used within the Superpave volumetric mixture design procedure. This SPT was intended to provide accurate correlation to field rutting performance. Three candidate tests and sixteen test parameters were evaluated using mixtures and performance data from three experimental sites: the Minnesota Road Project (MnRoad); the Federal Highway Aeration (FHWA) Accelerated Loading Facility Study (ALF), and the FHWA Performance-Related Specifications Study (WesTrack).; The scope of this work incorporated new development in laboratory test specimen instrumentation techniques, and the determination of the minimum test specimen dimensions that would provide true measured material responses. The testing program included confining and radial deformation measurements. Both of these are generally not common in current testing practices. A major task effort was also undertaken to develop two predictive models for their use as design tools for permanent deformation prediction.; Several failure analysis concepts were introduced and verified throughout the testing program. These concepts included failure strains, plastic strain ratio, volume change, constant compliance at failure, and plastic to resilient strain ratio at failure as a design guide parameter.; Two tertiary flow laboratory response parameters stood out in the study as having excellent correlation with field rut depth data: the flow number from the repeated load test and the flow time from the static creep test. The results in both tests indicated that tertiary flow could be captured from either axial or radial strain measurements. This was a very significant finding related to the simplification of testing equipment and sample instrumentation that could be realized with the use of radial measurements only. Furthermore, the rate of permanent deformation obtained from the confined repeated load tests best simulated the rate of deformation occurring in the field. Overall, the flow number of repetitions from the repeated load test was recommended as the design test parameter for the simple performance test.