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

摘要

The application of asphalt overlays on existing pavements comprises a significantpercentage of maintenance activities to restore asphalt pavement condition. Increasingattention is being paid to improving surface smoothness from overlay constructionbecause smoother overlays will likely have longer lives due to decreased dynamicloading, as well as provide fuel economy benefits and greater comfort to road users.California Department of Transportation (Caltrans) Pavement Condition Survey (PCS)data were used in this study to investigate the effects of repairs, pre-overlay condition,surface type and binder type on initial overlay smoothness. Linear mixed effects modelswere used in the analysis to take into account the variation across random effectvariables. The smoothness of overlays was measured in terms of the InternationalRoughness Index (IRI). The analysis results indicated that pavement pre-overlaycondition (IRI) was the most important variable affecting overlay smoothness: pavementswith lower pre-overlay IRI were smoother than those with higher pre-overlay IRI.Increasing overlay thickness was found to have a significant effect on the smoothnesswhen the pre-overlay condition was poor. In terms of pre-overlay repairs, analysis ofCaltrans PCS data showed that pavements with digouts (milling and patching in thewheelpaths) performed better than pavements with milling of the entire surface prior tothe overlay. The effects of surface type (dense- or gap-graded versus open-graded) andbinder type (rubberized or not rubberized) were dependent on the pre-existing pavementcondition and/or other factors. Possible reasons for differences with previous studies arementioned.