Ride Quality Performance of Asphalt Concrete Pavements Subjected to Different Rehabilitation Strategies

Abstract

The Long Term Pavement Performance (LTPP) program is a 20-year study of pavement performance. The performance of asphalt concrete pavements that are subjected to different rehabilitation strategies are studied under the SPS-5 experiment in the LTPP program. In a SPS-5 project, various rehabilitation techniques are applied to eight test sections, with all of the rehabilitation techniques involving an overlay. The factors that are studied in this experiment are, overlay mix type (recycled and virgin), overlay thickness (50 and 125 mm), and surface preparation of the asphalt concrete surface prior to overlay (i.e., overlay placed with and without milling). Data obtained from SPS-5 projects were analyzed to evaluate the reduction in roughness achieved for each rehabilitation strategy, and to compare the roughness progression after rehabilitation. The International Roughness Index (IRI) was used to characterize the roughness in this study. A statistical analysis comparing the IRI of the pavement before and after the overlay indicated the IRI of the pavement after overlay did not depend on the pre-rehabilitation IRI, overlay thickness, if milling was performed or not prior to overlay, or the type of asphalt concrete used for the overlay (virgin vs. recycled asphalt). The analysis was repeated considering the SPS-5 projects that had a pre-rehabilitation IRI greater than 1.5 m/km, which only considers the rougher projects. A similar result as the previous analysis was obtained in this case too, except that milling prior to overlay was a factor that affected the IRI of the overlaid pavement. An evaluation of roughness progression over a 7-year period after the overlay was performed by using the time-sequence IRI data available for each project. The statistical analysis of data indicated the progression of roughness in the overlaid pavements depend on the pre-overlay IRI of the section and overlay thickness. The analysis did not indicate milling prior to overlay or asphalt concrete type as being significant factors that affect the progression of roughness.