ALF testing for development of improved Superpave binder specification

In 2001, the Federal Highway Administration (FHWA) and 15 State highway agencies (SHA) initiated a transportation pooled fund study to use FHWA's two accelerated loading facility (ALF) machines to validate and refine changes being proposed in Superpave specifications to properly grade modified asphalt binders. The study will also provide early data to test new features included in the proposed 2002 Pavement Design Guide. With active participation by the SHA and the asphalt industry in the design and development of the experiment, 12 full-scale lanes of pavements with various modified asphalts were constructed at the FHWA's Pavement Test Facility in Virginia during the summer and fall of 2002. Results of the first year's ALF rutting tests generally rank the performance of the modified binders much differently than the results from laboratory mixture performance tests (the French Pavement Rutting Tester, the Hamburg Wheel Testing Device, and the Superpave shear tester). This paper presents an overview of the pooled fund study, pavement construction, ALF loading conditions and sequences, and the data obtained to date.