ABSTRACT

This project was designed to develop 1) a better quantitative understanding of the relation between laboratory accelerated binder aging and field aging, 2) a test procedure to measure properties of an aged binder that relate to failure on the road, and 3) a proposed specification for estimating the relative durability of binders in the presence of oxidative aging. Tests were conducted on original base and polymer modified binders, laboratory compacted mixtures, and pavement-aged binders. The project necessarily evolved to a more comprehensive approach to improving pavement service life. Methods for significantly improving pavement durability should be implemented: 1) construct pavements with the lowest possible accessible (interconnected) air voids, consistent with other best construction and mix design practices; 2) use mix designs that have an inherently low decrease in fatigue life with binder oxidation, coupled with an appropriately high initial fatigue life; 3) use binders with a minimum stiffness at the PAV* 16 hour condition (consistent with the appropriate performance grade); 4) use the pavement aging model for pavement design; 5) use binders that have inherently slow hardening rates kinetics; and 6) use modifiers that provide the most reduction in the hardening rate. Items 1 and 2 have a dramatic impact on pavement service life but require additional research for the most effective implementation: 1) determine the parameters that govern the decline of mixture fatigue life with binder hardening; 2) determine methods to reliably, and with minimal risk to other construction parameters, achieve very low accessible air voids in pavements.

 

Keywords:Asphalt, Modified Asphalt, Asphalt Durability Specification, Asphalt Concrete Long-Term Performance, Asphalt Hardening in Pavements, Asphalt Fatigue