A model for dynamic creep evaluation of SBS modified HMA mixtures

The specimens, according to the Marshall Stability testing procedure, of hot mix asphalt (HMA) containing bitumen modified with styrene–butadiene–styrene (SBS) have been constructed in the laboratory and tested under dynamic loading for permanent deformation using Suleyman Demirel University Asphalt Tester equipment (SDU-Asphalt Tester). Analysis of data shows that the permanent deformation of the samples may be modeled in terms of the specimen’s characteristics in a very satisfactory manner. Benefits of adding styrene–butadiene–styrene (SBS) in variant quantities and in variant types of additive to asphalt cement (AC-60/70) were investigated. Initial research was done to determine the physical properties of asphalt cement and modifiers. Fifteen asphalt binder recipes were prepared with two types of gradation, six different contents of bitumen, four different contents of polymer, three different types of polymer. After that, Marshall samples were prepared by using the modified and unmodified control asphalt binders. The results of investigation indicate that asphalt mixtures modified by any SBS additive gives the best permanent deformation resistance in the tests carried out in this study, so that, this modification increases physical and mechanical properties of asphalt binder. In this study, total deformation of each sample was calculated using a newly developed equation containing variables of mixture characteristics. In addition to these, to develop a model that could fit the creep curve a new logarithmic model derived from first 100 preconditioning loading was developed instead of power law function model for first stage of permanent deformation curves.