Quantification of Effect of Polymer-Modified Asphalt on Flexible Pavement Performance

Polymer-modified asphalt (PMA) mixtures are routinely used today in flexible pavement structures or overlays carrying high volumes of traffic. Although there have been numerous laboratory and field studies comparing the performance of PMA and conventional hot-mix asphalt (HMA) mixtures, for example, Superpave® and Marshall, there has not been a concerted effort to quantify the benefits of using PMA mixtures or to develop guidance on when the use of PMA mixtures is cost-effective. An investigation of nearly three dozen real-world pavement sections in North America was conducted to quantify the benefits of using PMA mixtures. The test sections used in performance comparisons included both roadway and accelerated pavement test sections. Performance data for the test sections were derived from published literature or other public sources such as the Long-Term Pavement Performance or the National Center for Asphalt Technology databases. On the basis of the performance comparisons made between PMA and conventional sections, it was found that PMA mixtures significantly enhance not only the rutting performance of flexible pavements but also their fatigue and fracture performance. The examples used in this study show an extended service life for deep-strength HMA pavements of 5 to 10 years through the use of PMA mixtures, on the basis of the performance observations from the companion test sections, which were constructed mostly with older Marshall or Hveem mixtures. A definite bias exists between the predicted and measured distress values for the sections with PMA mixtures when using current mechanistic-empirical distress prediction models. This finding suggests a need for different calibration factors in PMA mixtures for use in rutting and fatigue cracking prediction equations.