Performance of a Highly Polymer-Modified Asphalt Binder Test Section at the National Center for Asphalt Technology Pavement Test Track

Abstract

Polymer modification of asphalt binders is commonly used to improve either the rutting or the cracking performance of asphalt mixtures. In most cases, 2% to 3% polymer is added to the binder; however, highly polymer-modified (HPM) mixtures can use 7% to 8% polymer to create a more integrated polymer chain network, which improves rutting and fatigue performance. In 2009, an HPM mixture test section was built at the National Center for Asphalt Technology Pavement Test Track; the test section was approximately 5.75 in. thick. A control test section was simultaneously built at 7 in. thick with the use of conventional paving materials. The objective of this study was to assess the long-term field performance of the HPM mixture and control sections placed at the test track. These sections were evaluated in regard to field performance and structural capacity. Falling weight deflectometer testing was conducted to determine in-place modulus over time, and weekly strain and pressure responses were collected to determine how the test sections behaved mechanistically under live trafficking. The performance of the test sections was monitored with the use of inertial profilers to measure rutting and ride quality, and visual inspection was used to quantify cracking. After 20 million equivalent single-axle loads of trafficking, the HPM mixture test section had less cracking and rutting than the control section and the ride quality had not diminished over time. These findings support the use of HPM mixes in agency paving programs where appropriate.