Abstract
For characterizing the polymer modified binders, different state Departments of Transportation (DOTs) use different time consuming and empirical Performance Grade (PG) Plus test methods. Furthermore, the PG Plus tests are silent when asphalt binders are modified with chemicals such as polyphosphoric acid (PPA). But, the effects of the polymer are not accurately identified through these conventional tests such as Elastic Recovery (ER) and tenacity. The main goal of this study is to recommend alternative test method(s), which can possibly be pursued by using, a Dynamic Shear Rheometer (DSR). Thus, Multiple Stress Creep and Recovery (MSCR), ER-DSR, Frequency Sweep, and Binder Yield Energy Test (BYET) are being explored to find their effectiveness. Three PG binders (PG 64-22, PG 70-22 and PG 76-22) have been selected for this investigation. These binders have been prepared with styrene-butadiene-styrene (SBS) polymer, PPA, or a combination of both. Further, chemical tests such as SARA (Saturate, Aromatic, Resin, and Asphaltene) analysis and FTIR (Fourier-transform Infrared spectroscopy) are also being explored to fulfill the objectives. Preliminary findings suggest that the PG Plus tests deem to be obsolete. Also, a single test procedure is not sufficient to identify the presence and effectiveness of modifiers in the PG binders.
Highlights
The uses of polymer modified asphalt binders have been extensively increased in pavement engineering due to high resistance against rutting, thermal cracking, fatigue cracking, stripping, and temperature susceptibility [1, 2]
Routine Superpave tests such as Rotational Viscometer (RV) (AASHTO T 316), Dynamic Shear Rheometer (DSR) (AASHTO T 315), Rotational Thin-Film Oven (RTFO) (AASHTO T 240), Pressure-Aging Vessel (PAV) (AASHTO R 28) and Bending Beam Rheometer (BBR) (AASHTO T 313) are included in the test plant
The variation of the height of the peaks during the Fourier-transform infrared spectroscopy (FTIR) test can be used to explain the variation of chemical compositions between the neat binder samples
Summary
The uses of polymer modified asphalt binders have been extensively increased in pavement engineering due to high resistance against rutting, thermal cracking, fatigue cracking, stripping, and temperature susceptibility [1, 2]. The existing Performance Grade (PG) test methods are not suitable to determine the mechanical properties of the polymer modified binders beyond the linear viscoelastic range. The conventional Superpave tests were developed only to characterize the unmodified asphalt binders [3]. Many state Departments of Transportation (DOTs) including Arkansas Department of Transportation (ArDOT) use PG Plus tests such as Elastic Recovery (ER) [4] to characterize the polymer modified binders to examine the existence of polymer. The Plus tests are silent in the cases of chemicallymodified PG binders
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