The effects of asphalt binder oxidation on hot mix asphalt concrete mixture rheology and fatigue performance

摘要

Asphalt oxidation causes major changes to binder properties and is hypothesizedto be a major contributor to age-related pavement failure such as fatigue cracking.Extensive laboratory aging research has been done to assess the effects of oxidation onbinder properties. Previous work shows binder oxidation makes the binder stiffer andmore brittle, leading to higher binder stresses under a given deformation. Failure occurswhen these stresses exceed the strength of the binder. However, binder oxidation inpavements has not been studied in the same detail as laboratory aging of neat binders.The impact of binder oxidation on long-term pavement performance has been eitherunderestimated or ignored.This research includes studies of binder oxidation in Texas pavements tocompare the field aging with laboratory neat binder aging, the impact of binder oxidationon HMAC mixture aging and HMAC mixture fatigue performance, and fundamentalrheological property changes of the binder and the mixture.Binder oxidation is studied in fifteen pavements from locations across Texas.Results indicate that unmodified binders in pavements typically oxidize and harden to adegree that exceeds generally accepted pavement aging assumptions. This hardeningmay also extend much deeper into the pavement than has been previously assumed ordocumented. Data suggest that pavements can oxidize at rates surprisingly uniform withdepth once early oxidation occurs, and that these rates continue for an extended time.Laboratory-aged HMAC mixtures and binders were tested and analyzed forfatigue resistance and their rheological properties. Mixture aging shows the same aging mechanisms as neat binder aging. Both binder and mixture have a higher modulus withaging and a good rheological correlation. The decline in mixture fatigue life (determinedusing the calibrated mechanistic fatigue analysis approach with surface energymeasurement) due to oxidation is significant. Pavement service life is dependent on themixture, but can be estimated by a cumulative damage approach that considers binderoxidation and pavement loading rate simultaneously. The differences in expectedpavement life arise from differences in the rate of binder stiffening due to oxidation andthe impact of this stiffening on the decline of fatigue life.