Assessing the usefulness of the outer-area method in quantifying the structural capacity of full-scale composite pavement sections subjected to accelerated pavement testing

The focus of this study was to evaluate the overall accuracy of the Outer-Area method in quantifying the structural capacity of full-scale, composite pavement sections that are subjected to APT. Five 9.1 m. long and 3.7 m wide composite field sections were evaluated in this study. All sections contained a similar substructure (i.e., 203 mm, Portland cement concrete base, 406 mm New Jersey I-3 (A-1-a) granular subbase, and 304 mm, compacted subgrade). Section 1 contained a stone matrix asphalt (12.5-SMA) overlay while Section 2 contained a 50.8 mm thick, New Jersey high performance thin overlay (NJHPTO) overlay. Sections 3, 4 and 5 contained an overlay that was a combination of a 25 mm thick, binder rich intermediate course (BRIC) and a 50 mm layer of a Superpave mixture (9.5-ME), SMA, and NJHPTO, respectively. All sections were instrumented with two asphalt strain gauges and subjected to accelerated pavement testing (APT) using a heavy vehicle simulator (HVS). During APT, a 60 kN, dual tire, single axle load was applied to the sections at 8 km/h for 200,000 repetitions. Heavy weight deflectometer (HWD) testing was performed on each test section before and after APT. The collected pavement deflection data from each composite section was analyzed using the outer-Area method to determine the overall structural capacity of the bound pavement layers before and after APT. The actual field performance of the test sections was assessed using the strain data collected during APT. Based on the results of the study it was determined that the Outer-Area method may not be able to accurately quantify the damage full-scale composite pavements experience due to APT.