Polymer modified hot mix asphalt field trial.

788560706Final report.PDFTech ReportFHWA/MS-DOT-RD-99-111MS-DOT-RD-99-111Asphalt pavementsAsphalt additivesAdditivesMixturesHot mix paving mixturesTestingEvaluationUnited StatesMississippi. Dept. of TransportationAlbritton, Gayle E.Barstis, William F.Crawley, Alfred B.Mississippi. Dept. of Transportation. Research DivisionUnited States. Federal Highway AdministrationNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceNTL-HIGHWAY/ROAD TRANSPORTATION-DesignNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceUS Transportation CollectionA problem plaguing HMA pavements is rutting, which develops because of the high summer temperatures and heavy trucks. Many differentpolymer modifiers for asphalt cement have been developed to help improve both the rutting and thermal cracking problems of HMA by altering theproperties of the asphalt cement binder.The primary objective of this research was to evaluate the engineering properties and performance, especially rut resistance, of dense graded HMAcontaining specific polymer modifiers. The polymer modifiers were used in the HMA for the top two pavement layers of an HMA overlay of aflexible pavement The nine modifiers considered in this study included two crumb rubbers and one gelled asphalt.Primary conclusions and recommendations resulting from this study include the following:1. Each polymer required mixing at a higher temperature than regular HMA. These temperatures ranged from 320o to 351oF.2. The modified HMA mixes were successfully produced in a normal HMA production facility. Most of the modifiers did not require a blendingunit.3. Brookfield Viscometer tests showed that the modifiers were all more viscous at the lower temperatures.4. Results of the GTM tests showed that the laboratory specimens had sufficient shear strength to resist the stress state in the pavement and thatthe air voids were above the flushing level and were consistent with design values.5. Results to date indicate that all the modified binders are providing superior rutting resistance as compared to the control binder. This validatesthe wisdom of using modified binders for areas of high equivalent single axle loading (ESAL). Continued monitoring will help to better quantifythe improvement provided by the modified binders.6. The APA test results correlate well with field rutting measurements for most of the polymer modifiers considered in this study. This indicatesthe potential for using the APA to predict the relative rutting performance of different polymer modifiers. Research should be conducted tosubstantiate this use of the APA.7. The selection of a polymer modified asphalt binder grade based on the high temperature component of the PG designation could be quiteinappropriate for a given project, especially when crumb rubber modifiers are considered for use in the HMA