Implementation and thickness optimization of perpetual pavements in Ohio

"[Prepared] for the Ohio Department of Transportation, Office of Statewide Planning and Research and the United States Department of Transportation, Federal Highway Administration"--Cover.; "June 2015."; Includes bibliographical references (pages 202-207).; Final Report.; State Job Number: 465970This report documents the performance of perpetual pavement structures constructed by the Ohio Department of Transportation. Three perpetual pavement test sections on U.S. Route 23 in Delaware, Ohio (DEL-23) were constructed with AC thicknesses 11 in. (28 cm), 13 in. (33 cm), 15 in. (38 cm) and instrumented to detect strains in Fatigue Resistant Layer (FRL) and base layers, deflections, temperatures, and subgrade pressures. Strains at bottom of FRL during Controlled Vehicle Load (CVL) testing in summer indicated the 13 in. (33 cm) section on stabilized subgrade and 15 in. (38 cm) section on compacted subgrade met perpetual criteria, while 11 in. (28 cm) section on stabilized subgrade did not. Computer simulation of DEL-23 sections with PerRoad confirmed these findings, but also indicated the 11 in. (28 cm) section would meet perpetual pavement criteria. Test pavements were built in the Accelerated Pavement Load Facility (APLF) and instrumented similarly to DEL-23. The sections were thinner, but included Highly Modified Asphalt (HiMA) with Kraton polymer binder in sections of depth 8 in. (20 cm), 9 in. (23 cm), 10 in. (25 cm), and 11 in. (28 cm), the last using conventional asphalt in the base as a control with HiMA in upper layers. There was no FRL. The 10 in. (25 cm) and 11 in. (28 cm) sections met perpetual criteria even when heated through to 100° F (37.8° C). After enduring 10,000 passes of 9000 lb (40 kN) load at 5 mph (8 km/h), the surface rutting was measured with a profilometer and was considerably below even the ODOT threshold for "low rutting" (0.125 in. or 0.32 cm). An extrapolation of the curve fit suggested the HiMA surface would remain under the low rutting threshold much longer than conventional or WMA surfaces. Note these sections were built under ideal conditions, so field experience may differ. Fatigue endurance limit was computed using parameters measured in the laboratory asphalt mixture performance tester from samples collected from DEL-23 and APLF. Endurance limits computed following the NCHRP Project 9-44A method and MEPDG guide (E0=E*) provided a good fit with field results. Ten high-performing existing AC pavements from a previous forensic study (Sargand and Edwards, 2010) were further evaluated as potential perpetual pavements. Follow-up field investigations at each site included distress surveys, falling weight deflectometer (FWD) measurements, dynamic cone penetrometer (DCP) data, and Portable Seismic Property Analyzer (PSPA) measurements. Strains at the bottom of the asphalt were back calculated from FWD deflections using the elastic modulus program Evercalc. AC cores were collected and tested for indirect tensile strength and resilient modulus. The pavements were modeled using finite element software Abaqus, which confirmed the Evercalc strain computations. Of the ten pavements, seven appeared to meet conservative perpetual pavement strain criteria, one could be upgraded to meet perpetual pavement criteria by adding an additional asphalt layer, and two clearly did not meet perpetual pavement standards. A brief report on the status of previous perpetual pavement designs built in Stark County (STA-77) and Wayne County (WAY-30) is given