Balanced Mix Design Rut Test Validation Test Track: Construction of HMA Sections

This technical memorandum describes the design and construction of a full-scale test track and the construction quality control/quality assurance testing of the different materials, including subgrade, aggregate base, and asphalt mixes. Construction of the test track and the Heavy Vehicle Simulator (HVS) and laboratory testing that followed are part of the Caltrans balanced mix design (BMD) implementation effort led by the Pavement and Materials Partnering Committee (PMPC) BMD Working Group. The main goal of the test track evaluation was to compare the rutting performance of surface mixes under the HVS with laboratory rutting test results. A secondary goal was to compare the reflective cracking performance of the same mixes with laboratory cracking test results. The test track includes four lanes, each 177 ft. long, and each with a variation of a control hot mix asphalt (HMA) surface mix, with two sections in each lane for evaluation of either rutting or reflective cracking performance. The rutting evaluation sections had an asphalt long-life pavement structure designed and built to test the rutting performance of the surface layer under the HVS. The reflective cracking evaluation sections were an asphalt overlay on a jointed plain concrete pavement. The test track asphalt surface can be evaluated and replaced in successive testing rounds. Following PMPC BMD Working Group directions, the first round of testing focused on HMA Type A with plain binder, used in the construction documented in this document. The control mix, used for paving Lane 1 of the test track, was an HMA with 3/4 in. maximum aggregate size, 25% reclaimed asphalt pavement content (percent by aggregate replacement), and virgin binder graded as PG 58-22. Three alternative mixes were used for paving Lane 2, Lane 3, and Lane 4. The alternative mixes were intentionally designed to make the mixes susceptible to rutting. The construction of the subgrade, aggregate base, concrete slabs, and asphalt mixes went as expected, with no incidents to report. Overall, the asphalt mixes used for the construction matched the design expectations, and the field compaction was as expected.