Laboratory Testing to Design an Asphalt-Treated Permeable Base for the Federal Highway Administration’s Pavement Test Facility

The Federal Highway Administration reconstructed a new Pavement Test Facility (PTF) to perform accelerated testing on various pavement structures. Three of the eleven lanes were designed with an asphalt-treated permeable base (ATPB) to evaluate its impact on pavement response and performance. ATPBs are created by mixing an open-graded aggregate with a small percentage of asphalt binder; however, the job mix formula (JMF) and the compacted density of the mix all influence the stiffness, strength, and permeability of the resulting ATPB. To develop an appropriate JMF for the PTF, various unbound and ATPB specimens were prepared using three different locally sourced open-graded aggregates with 0 to 4% asphalt binder. Asphalt permeameter test specimens, 150 mm in diameter and 116 mm in height, were prepared using a Superpave gyratory compactor which also determines the minimum void ratio and the maximum density of the mix. The stiffness and strength of the ATPB specimens were measured by performing resilient modulus and quick shear tests on 150 mm by 300 mm compacted specimens. The stripping resistance of select ATPB specimens was evaluated by conducting tensile strength ratio tests. The findings showed that the asphalt binder content had a negative relationship with permeability and air voids but a positive relationship with stiffness. The binder grade and specimen gradation had a significant impact on moisture susceptibility. The results informed the selection of the ATBP JMF for the PTF. This paper provides an overview of the PTF design requirements and the ATPB experimental approach with the results.