| Binder and mixture tests were performed to evaluate the relative performance of a PG 67-22 base binder and six other commercially available binders produced by modifying the same base binder with the following modifiers: one Styrene Butadiene Styrene (SBS) polymer, three commercially available hybrid binders composed of different percentages of rubber and SBS polymer, and two asphalt rubber binders (5% and 12% rubber: ARB-5 and ARB-12). Results indicated that hybrid binders (modified with more rubber than SBS) that exceed the cracking performance characteristics of unmodified binder and asphalt rubber binders, and have about the same cracking performance characteristics of SBS polymer modified binder can be produced commercially. Results also indicated that hybrid binder can be suitably specified using existing specification requirements for PG76-22 binder and solubility. Therefore, it appears that hybrid binder has the potential to replace three binders currently used by FDOT in hot mix asphalt: SBS polymer modified asphalt, ARB-5, and ARB-12. It was recommended that FDOT develop a transition plan to accomplish this. The research also showed that existing binder tests do not accurately predict cracking performance at intermediate temperatures, even in a relative sense. A further Healing testing was performed on the dense-graded granite mixtures to evaluate the healing potential of hybrid binders compared to base binders. Different testing procedures were carried out and analyzed to give a better understanding of healing mechanisms. Results from healing test agreed with those from cracking performance evaluation. However, more healing parameters and procedure need to be fully developed to capture healing characteristics more specifically. It was recommended that FDOT pursue development and evaluation of the healing test. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)... |
