Characterizing Cracking of Asphalt Mixtures with Fiber Reinforcement

Abstract

This study characterized the cracking resistance of two independent sets of mixtures from the FHWA full-scale accelerated loading facility and a Pennsylvania Department of Transportation trial section. Both sets had the same selection of three types of comparative materials: an unmodified control mixture, a mixture with a binder modified with styrene–butadiene–styrene (SBS), and the same control mixture modified with synthetic fiber reinforcement. Two methods of cracking characterization that can be conducted with the Asphalt Mixture Performance Tester were evaluated: simplified viscoelastic continuum damage cyclic fatigue and direct tension monotonic strength. Dynamic modulus results showed that fiber modification had less of an effect than did polymer modification. Cyclic fatigue test results predicted that both SBS- and fiber-modified mixes performed better than did the control mixes in both sets of materials. Furthermore, the cyclic fatigue tests also indicated that the SBS-modified mix performed better than did fiber under smaller fatigue strains, but the fiber-reinforced mix performed better at higher strains. Recent performance data from the FHWA full-scale accelerated loading facility agreed with the laboratory observation. The pattern where the fiber mixtures exhibited a strain-dependent performance benefit was also observed when the same continuum damage models were used but with data from a different testing methodology by means of monotonic direct tension tests. When all test data are considered, the performance benefits of fiber modification for crack resistance appear to be subtle when observed in the laboratory, but benefits are likely at relatively higher strains.