Tack Coat Performance and Materials Study

016634052017Final ReportPDFTech ReportFHWA/OH-2017-33SJN 135158Asphalt pavementsBenefit cost analysisBituminous overlaysBond strength (Materials)Longitudinal crackingPavement layersPavement performanceShear strengthTack coatsHighwaysMaintenance and PreservationMaterialsTack coatSpray paverTrackless tackBond energyBenefit-cost analysisProceduresUnited StatesOhio. Dept. of Transportation. Office of Statewide Planning and ResearchWilson, BryanChowdhury, ArifHu, ShengKim, Sang-SooNazzal, MunirAbbas, Ala R.Texas A&M Transportation InstituteOhio UniversityUniversity of AkronOhio. Dept. of Transportation. Office of Statewide Planning and ResearchUnited States. Federal Highway AdministrationUS Transportation CollectionA good bond provided by a tack coat can improve performance of asphalt overlays. The objectives of this research were: (1) develop a method for testing the bond between pavement layers; (2) evaluate the bond performance and predict long-term performance of different tack coat strategies; (3) assess the minimum bond to achieve acceptable performance; and (4) evaluate the cost effectiveness of different tack coat strategies. Field test sections were constructed considering surface type, tack type, tack rate, and application method. Core bond performance, initial and after 8-months, was tested in the lab with an interface shear strength tester. Tack type, application method, and bond age were statistically significant variables. Trackless tack had the highest bond performance. High performance was also achieved by SS-1H placed with a distributor, and by no tack samples. The rubberized tack and SS-1H placed with a spray paver had the lowest bond performance; however, after eight months, bond performance for these sections doubled and was well acceptable. Performance was predicted considering reflection cracking, rutting, and fatigue cracking. Generally, higher bond strength resulted in longer service life; however, on the milled HMA sections, the optimal performance was achieved at a partially bonded condition. The differences among pavement life-cycle costs for the different materials and methods were small, between 2 and 6 percent of the overall project cost. The shear bond strength test is recommended to evaluate field bond performance. A tack coat construction specification, with a minimum initial bond strength of 70 psi, may be considered for exploratory work