Comparison of SUPERPAVE mix design and performance criteria with European design methods

The mix design of asphalt mixtures has changed over the last decades due to various developments and is now challenged again by increasing traffic volumes and increased requirements concerning performance and durability of pavements. \nA turn to more fundamental design concepts is sought by the European Standardization Committee dealing with European wide uniform standards in highway engineering as well as in other engineering fields. \n\nThis thesis compares the current practice of mix design in Finland and in Germany and the United States of America (Superpave mix design) in order to investigate the applied approaches. \nThe comparison was preceded by a thorough literature study of mix designs in general and the current standards providing the corresponding requirements and guidelines for mix designs. \nTo illustrate the requirements a volumetric window was computed which shows the relationships of the volumetric properties and offers the graphical view of acceptable mixtures according the mentioned specifications. \nThe comparison was performed for the most common types of asphalt: asphalt concrete CAC) as a continuous graded mixture and stone matrix asphalt (SMA) as a gap graded mixture. \nBoth types of asphalt were designed applying the three selected concepts and evaluated following the specific guidelines and specifications. \n\nFurthermore the performance of the designed mixtures was investigated with the following mechanical properties: stability (Marshall Stability test), stiffness (resilient modulus, diametric test) and indirect tensile strength. \nThese mechanical properties were evaluated and compared with the expected resistance to fatigue cracking, one of the major distresses for asphalt pavements. \nThe expected performance was obtained from the results of a cyclic diametric test, conducted in a stress controlled mode. \nThe fatigue life of all mixtures was assessed. \n\nResearch showed, that the different compaction methods and binder selection criteria had more influence on the designed mixture that the influence of the varying gradation. \nHowever, mix design according to Superpave system gave the lowest binder content and the coarsest gradation for the AC as well as for the SMA, caused of the most severe compaction effort. \nThe German mix design led to the highest binder content for both types of asphalts. \nThis was due to the compaction method and effort which was the Marshall hammer. \nThe Finnish mix design yielded with stiffest mixture and therefore the best rutting resistance due to the selected stiff binder grade. \nA correlation between the mechanical properties of stiffness/strength and fatigue life was confirmed for the AC.