Dual tires have traditionally been used to limit pavement damage by efficiently distributing axle loads over a larger contact area than single tires. However, in recent years, the trucking industry, stating economic and safety benefits, has promoted the use of wide-base single tires. The Super Single tire, an early type of wide-base tire, proved inadequate and induced excessive pavement damage. By contrast, the new generation wide-base tires have contact areas that approach those of dual tires and offer the potential for improved performance. The Florida Department of Transportation investigated the pavement damage potential of four tire types, including a conventional dual tire (11R22.5), a Super Single (425/65R22.5), and two newly designed wide-base single tires (445/50R22.5 and 455/55R22.5 respectively). A controlled accelerated pavement testing program, in addition to theoretical modeling, was performed to determine critical pavement response parameters. Pavement damage was measured in terms of rutting and fatigue cracking (bottom-up or top-down), the predominant distresses in Florida. The investigation revealed that the 455-mm wide-base tire performed as well as the dual tire. By comparison, the 445-mm wide-base tire was shown to create more rut damage on a dense-graded pavement surface and was predicted to create more bottom-up cracking than a dual tire. As expected, the Super Single induced the most damage to the pavement.
Reclaimed asphalt pavement (RAP) mixtures have shown good resistance to rutting for hot-mix asphalt (HMA) pavement. Mixtures with polymer-modified binders such as styrene-butadiene-styrene (SBS) have also shown good performance against rutting and cracking. This paper presents the laboratory evaluations used to determine the rutting and cracking performance of the RAP mixtures with SBS polymer-modified binders as virgin binders. The asphalt pavement analyzer (APA) test and indirect tensile (IDT) test were conducted for the laboratory evaluation. The properties of SBS polymer-modified binders blended with recovered RAP binders were also investigated. The binder tests included G*/sinδ as the rutting parameter and G*sinδ as the cracking parameter of the Super-pave® PG grade system. The multiple stress creep and recovery test, which has recently received attention as an indicator of the rutting potential of polymer-modified asphalt binders, was also performed. RAP mixtures with SBS polymer-modified binders were fabricated containing different amounts of RAP materials: 0%, 15%, 25%, and 35%. From the APA and Superpave IDT tests, RAP mixtures with modified binders showed good performance regardless of the amounts of RAP materials in HMA. Even though the parameters, G*/sinδ and G*sinδ, and the percentage of recovery indicated the different amounts of RAP binders in polymer-modified binders, the relationship between these parameters and mixture performance was not clearly identified.
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