Performance of Flexible Pavement Rehabilitation Treatments in the Long-Term Pavement Performance SPS-5 Experiment

Abstract

The results of a study conducted to assess the relative performance of different flexible pavement rehabilitation treatments, including the influence of pretreatment condition and other factors, are presented. The data used in the study were drawn from the Long-Term Pavement Performance Studies' Specific Pavement Study (SPS) SPS-5 and General Pavement Study (GPS) GPS-6B experiments. The rehabilitation treatments used in the SPS-5 experiment are 2- and 5-in. overlays with virgin or recycled asphalt concrete mixes with or without preoverlay milling. Overlay thickness and preoverlay roughness levels were the two factors that most influenced the performance of the asphalt overlays of asphalt pavements in the SPS-5 experiment with respect to roughness, rutting, and fatigue cracking. Over the long term, the 5-in. overlays outperformed the 2-in. overlays with respect to roughness, rutting, and fatigue cracking. Overlay mix type (virgin versus recycled) and preoverlay preparation (with or without milling) had slight and inconsistent effects. The average initial postoverlay international roughness index of an asphalt overlay of an asphalt pavement was found to be 0.98 m/km. The data show a slight but statistically significant tendency for asphalt pavements overlaid when they were rougher to have more initial roughness after overlay than asphalt pavements overlaid when they were smoother. The data show that, on average, about 6 mm of rutting develops in the first year or so after placement of an asphalt overlay of an asphalt pavement. This is presumably due to compaction of the mix by traffic and appears to be independent of the overlay thickness, mix type, preoverlay preparation, and preoverlay rutting level.

Effects of Milling and Other Repairs on Smoothness of Overlays on Asphalt Pavements

“…In recent years, the use of Reclaimed Asphalt Pavement (RAP) in overlays has also gradually increased, and the performance of overlays with increased RAP contents is a concern for some state highway agencies. Research results from two studies indicated that there was no significant effect on post-overlay IRI or on the long-term development of roughness, rutting, block cracking, or raveling introduced by mixes with either virgin aggregate or with 30 percent RAP [10,11]. It should be noted that during the period covered by this current study, Caltrans…”

“…As with the preceding factors discussed, inconsistent results among earlier studies have not clarified the role of pavement smoothness prior to overlay as a key factor affecting overlay smoothness. A study by Hall et al [10] found that original surface roughness had a significant effect on the smoothness of overlays and work by McGhee [12] found a correlation between pre-overlay IRI and post-overlay IRI. However, Perera and Kohn [9] found a contradictory result that showed no correlation between the IRI before and after the overlay.…”

“…Hall et al [10] found that 5 inch thick overlays outperformed 2 inch thick overlays in terms of smoothness and fatigue cracking over an average analysis period of 7.8 years. In another study, Wen et al [11] found that a small increase of overlay thickness can effectively reduce the development rate of transverse cracking.…”

Aggregate and disaggregate statistical evaluation of the performance-based effectiveness of long-term pavement performance specific pavement study-5 (LTPP SPS-5) flexible pavement rehabilitation treatments

“…The participating states had been tasked with selecting sites such that approximately one half of them were in a fair state (low pre-treatment IRI) and the other half in a poor state (high pre-treatment IRI). However, the field surveys could not be carried out at the prescribed time; as such it was not possible to establish which sections had poor or fair pre-treatment conditions before the sites were selected (Hall et al 2003). Initial analysis revealed that initial pavement condition (pre-treatment IRI) has no significant effect on long-term roughness progression (Equations (1) and (2)).…”

Evaluating the Role of Aggregate Gradation on Cracking Performance of Asphalt Concrete for Thin Overlays

“…The performance of thin asphalt concrete overlays will depend upon a number of factors including mix design approach and materials, underlying pavement type, surface preparation, traffic, climate and the construction quality. Based on the long-term pavement performance (LTPP) database, which is managed by the Federal Highway Administration, numerous studies have been conducted to evaluate the performance of different maintenance techniques, including thin overlays [9][10][11]. Indeed, there is a Specific Pavement Studies Experiment 5 (SPS-5) in the LTPP program that studies the effects of overlay thickness, overlay material, and pre-overlay treatment on the performance of asphalt overlay [12].…”