Evaluation of a highly-modified asphalt binder for field performance

This paper deals with laboratory and field evaluation of pure and polymer-modified asphalts (PMAs), in which one bitumen and one polymer type of different contents were used. Styrene-butadiene-styrene (SBS) modified asphalts were selected to evaluate which polymer concentration could offer cost-effective solutions on heavily trafficked highways. Polymer concentrations used were 0%, 3%, and 6% SBS by weight of binder. Asphalt cement containing 6% SBS was referred to as a highly-modified binder in this study. An in-service test road was constructed in 2012 to compare the performance of asphalt pavements built with PMAs while all other variables were held constant as possible. The results of laboratory testing indicated that the morphology of SBS modified binders was influenced by storage temperature and polymer content. The formation of an interlocked continuous network was shown to enhance the rheological properties of PMAs. Significant differences in resistance to rutting and cracking were noted between highly-modified and control asphalt mixtures. This observation was attributed to increased modulus and enhanced critical strain energy release rate of polymer-modified asphalt mixtures. Preliminary performance evaluations showed that none of the test sections evaluated exhibited obvious rutting. Notable differences were, however, observed in the cracking behavior. The test section with the highly-modified binder had a much better resistance to cracking. The field measurements on cracking corresponded well with the test results of the semi-circular bend test in the laboratory. The experimental results of the highly-modified asphalt were in good agreement with field performance. Future monitoring is needed to evaluate long-term trends in performance.