Use of polymer-modified binder has become much more important in recent years to enhance the durability and strength of asphalt concrete (AC) pavements in order to sustain higher traffic volumes, heavier loads, and extreme weather conditions. Unlike neat (unmodified) asphalt binders, polymer-modified binders are sensitive to the applied stress levels and show a nonlinear response in rutting factor and phase angle. The widely used dynamic shear rheometer (DSR) test (AASHTO T315) is not sufficient to capture viscoelastic properties of polymer modified-asphalt binders. Thus, state transportation agencies often need to conduct additional expensive and time consuming “PG Plus” tests (e.g., elastic recovery (ER), force ductility, toughness, and tenacity) for characterizing polymer-modified binders. Multiple stress creep recovery (MSCR), a recently introduced test method (AASHTO TP 70) for measuring high temperature properties of an asphalt binder, is expected to replace the existing AASHTO T315 for short-term aged binder. In the current study, MSCR and Superpave tests were conducted on three commonly used performance grade (PG) binders (PG 64-22, PG 70-28, and PG 76-28) from 12 different sources throughout Oklahoma. Based on expected traffic loads and service temperatures, the tested binder samples were graded in accordance with the MSCR grading system. The non-recoverable creep compliance (Jnr) and MSCR % recovery values obtained from the MSCR tests were then analyzed using the polymer curve and quadrant methods to assess the feasibility of the adoption of the MSCR test method for conditions prevailing in Oklahoma. Findings of this study reveal that the MSCR test method can be used to characterize polymer-modified binders without penalizing suppliers or risking the users.

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To address asphalt pavement thermal cracking, researchers have developed performance-based evaluation tools for asphalt mixtures. A minimum fracture energy obtained from a disc-shaped compact tension test and Black space parameters determined by the stiffness and relaxation properties of asphalt mixtures are two such methods to ensure good thermal cracking resistance. Mix specifiers and producers strive to meet the requirements set by these performance-based criteria by adjusting their mix designs. However, there is a lack of information and consensus on the effect of mix design variables (such as binder grade and mix volumetrics) on thermal cracking performance of mixtures as it relates to fracture energy and Black space location. This study strives to fill this gap by quantifying the effect of: (1) recycled asphalt content, (2) effective binder content, (3) air voids, (4) asphalt film thickness, (5) voids in mineral aggregates, and (6) PG low and high temperature grades on thermal cracking resistance. A large dataset, 90 mixtures from the Minnesota Department of Transportation and 81 mixtures from University of New Hampshire database, was used for the study. The results indicate a strong correlation between binder related properties (binder content, asphalt film thickness, PG spread) and fracture energy. The correlation coefficients obtained from this study for PG spread, effective binder content, and air void can be confidently employed to achieve targeted fracture energy thresholds. The same can be achieved for the Glower-Rowe parameter at 15ºC by employing the correlation coefficients obtained for PG low temperature, virgin asphalt content, and voids in the mineral aggregate.

Pavement preservation is playing an increasingly significant role in 1 maintaining our aged pavement infrastructure under severe budget constraints. One 2 important component is the use of surface treatments based on application of sealants.