Analysis of the Long-Term Pavement Performance Data for the Idaho GPS and SPS Sections

This project addresses the analysis of the Long-Term Pavement Performance (LTPP) data for the LTPP sites in Idaho. The goal was to determine the performance trends for the pavement in Idaho as found in the LTPP experiments. The research also investigates the use of the data to develop (as much possible) models that enable the prediction of the seasonal variation effects on the pavement materials (soils and asphalt mixes). In addition, the project looks into the applicability of the LTPP data in Idaho for the use and implementation of the new Mechanistic-Empirical Pavement Design Guide (MEPDG). Idaho participates in the LTPP program with 13 sites of general pavement studies (GPS) that include GPS-1, 3, 5 and 6A experiments. The only specific pavement studies (SPS) experiment in Idaho is SPS-3. Idaho participates in the SPS-3 with 12 sections. All data from all the sites were obtained and accumulated on a mini database. Analysis of the Idaho data was supplemented with data from few LTPP sites located in adjacent states with similar environments. Analysis of the performance data including roughness and rutting revealed that Continuous concrete pavements performed best, followed by jointed concrete pavements. The asphalt pavements on granular bases and existing asphalt overlays on asphalt pavements showed mediocre performances. That was largely due to the big gap in data at these sites. For SPS sites regarding cracking and rutting, the various types of surface treatments tested at the SPS 3 experiment were not effective at improving pavement conditions. Results showed that to improve pavement roughness, a thin overlay is the best treatment option, followed by the placement of a slurry seal coat. Placing chip and crack seal treatments did not show significant impact on pavement roughness. As part of the outcomes of this project, a mini-LTPP database for the LTPP sections in Idaho was developed in MDB file format and series of Excel files that include all Idaho data. In addition, models were developed based on analysis of national data for the subgrade and asphalt concrete moduli. An investigation into the implementation of the MEPDG in Idaho indicated that the current performance data in the Idaho sites are not sufficient for any meaningful calibration of the performance models in the new design guide.