A full-scale experiment was conducted at the Florida Department of Transportation (FDOT)'s accelerated pavement testing (APT) facility to evaluate the impact of segregation on hot mix asphalt (HMA) pavement performance. Localized areas of segregation were artificially generated during the construction of the APT test tracks, using improper paving techniques without any manipulation of the aggregate gradation. The subsequent APT results showed that, under similarly controlled conditions, the segregated locations exhibited significantly higher rutting than the non-segregated areas. Furthermore, supplementary field and laboratory tests indicated that the segregated locations had, in comparison, greater cracking, raveling, and tirepavement interaction noise potentials.
A full-scale experiment was conducted at the Florida Department of Transportation’s accelerated pavement testing (APT) facility to identify factors affecting the occurrence of interlayer scabbing and the impact of scabbing on pavement performances. Two experimental parameters—interlayer bonding condition of existing asphalt layers and milling thickness—were considered for the first objective. For the second objective, core specimens were obtained after the hot mix asphalt overlay on sections where scabbing was present and not present to compare their interlayer bonding strengths. In addition, APT was utilized to assess the rutting and cracking performance of the test sections. Test results indicated that the occurrence of scabbing is highly dependent on the interlayer bonding condition of the existing asphalt layers and milling depths. Once scabs form after milling, the scabs result in a weak or variable bond with the new overlay. Also, the accelerated loading using heavy vehicle simulator generated approximately 30% greater rut-depth and longitudinal cracks along the edge of the wheel path on the test sections with interlayer scabbing. In consideration of the reduced performance of the test sections with interlayer scabbing, the authors suggest preventing or removing the scabbing before the asphalt overlay.
Use of a material transfer device (MTD) during asphalt paving to provide smoother pavement while eliminating thermal and material segregation is well known. However, the additional operating cost may prevent contractors from investing in an MTD. This study evaluated the effect of MTDs on the smoothness of the finished friction course layer and predicted the incentives or disincentives a contractor may receive by using an MTD. Two empirical models were developed by using simple linear regression analysis to predict the smoothness of the final friction course on the basis of the underlying structural layer smoothness and whether or not an MTD was used. The regression model results were used in Monte Carlo simulations in conjunction with residual analysis techniques to predict, in a probabilistic fashion, the incentives or disincentives that a contractor could receive as a result of the Florida Department of Transportation’s new developmental specification for smoothness. Finally, expected incentives were predicted as a simulation result. Two validation projects with a normalized length of 10 mi showed additional expected incentives of $9,700 and $10,000 when an MTD was used compared with the expected incentives when an MTD was not used. The additional incentives were approximately 30% more than the typical operating cost of an MTD for construction of a 10 lane miles long friction course in Florida.
Flexible pavements are often rehabilitated by milling distressed asphalt and placing new asphalt at a thickness that accounts for expected traffic growth and pavement life. However, there are many reported benefits to concrete overlays as a method to rehabilitate and preserve distressed asphalt pavements. In 1988, the Florida Department of Transportation designed and constructed an unbonded concrete overlay on US-1 between Daytona Beach and Titusville. The 1.9-mile concrete overlay was part of a larger 8-mile milling and resurfacing of a deteriorated asphalt pavement. The concrete overlay test sections were divided into three groups based on design thicknesses of 6, 7, and 8 inches. Each of these groups included subsections with three joint spacing levels and two dowel bar configurations consisting of standard 12-inch spacing and wheel path only. The overlay sections are still in service with no major rehabilitation effort. The primary distress is pavement roughness found in sections with wheel path dowels only. The section with the most cracked slabs had joint spacings of 20 ft, which is no longer recommended. This paper documents the experimental program and presents the analysis and findings.
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