Creep in conventional and modified asphalt mixtures

The aim of this study was to evaluate permanent deformation of conventional and styrene butadiene styrene (SBS) polymer-modified asphalt concrete. Two types of polymer modification were selected. First pre-modified (PM) bituminous binder with SBS was used and identical samples were produced at optimal bitumen content. In addition SBS powder was incorporated and modified samples were prepared with laboratory-modified binder (M). Samples were prepared with great care. Static creep and repeated creep tests were conducted at both low (0 °C) and high (40 °C) temperatures. A Nottingham Asphalt Tester (NAT) was used for creep tests. Permanent deformations were evaluated with both identical samples for the same mixture type and different types of mixtures were interrogated with average deformations. Efficiency of SBS polymer additives was clearly observed with high temperature (40 °C) in both static creep tests and repeated creep tests. The PM mixtures showed a slightly increased resistance to the permanent deformation in comparison with the M mixtures. Static creep and repeated creep tests were found to be a good indicator of the rut resistance at high temperature (40 °C) for both conventional and polymer-modified mixtures. The superior performance of polymer modification in terms of rutting was clarified. The modified samples protected structural integrity at high temperature.