Evaluation of Asphalt Binder Properties and Polymer Modifications Effect on Asphalt Mixture Cracking

Asphalt pavement cracking has become the primary concern in relation to asphalt pavement durability over the past several years. The asphalt binder’s contribution to cracking has been investigated as one of the causes for this increase in overall asphalt pavement cracking. Increases in cracking have been attributed to the addition of re-refined engine oil bottoms (REOBs), air blowing, as well as various refining processing techniques. One asphalt binder parameter gaining interest in industry, as an indicator of the asphalt binder’s cracking potential, is delta critical temperature (ΔT c ). Several studies have shown that, as the value of ΔT c becomes more negative, asphalt pavement cracking increases. A significant issue exists concerning ΔT c and polymer modified asphalt binder. When the base asphalt binder exhibits good ΔT c values, modification with polymers often has a negative effect on the ΔT c value. Given that polymers have been shown to improve cracking response in an asphalt pavement it becomes critical that resolving this difference in response must be evaluated. This study focused on cracking properties of an asphalt mixture produced with asphalt binders having both good and poor ΔT c values and varied levels of polymer modification. Asphalt binders were evaluated with extensive rheological testing. Repeated load uniaxial direct tensile testing and viscoelastic continuum damage analysis were used to evaluate the asphalt mixtures. Preliminary indications are that polymers can mitigate poor ΔT c properties of the base asphalt binder.