Investigation of the effect of thermoplastic aromatic hydrocarbon resin on the rheological properties of asphalt binder

Increasing traffic loads, fluctuating climatic conditions, and environmental factors significantly shorten the service life of asphalt pavements and lead to substantial performance losses. Therefore, improving the rheological and mechanical properties of asphalt binders has become a fundamental requirement in modern highway engineering. Although polymer additives enhance performance, their high cost and compatibility issues have prompted the search for alternative modifiers. In this thesis, the effects of petroleum-derived aromatic thermoplastic resin (TPR) additive on the physical and rheological properties of asphalt binders were comprehensively investigated. The main objective of the study was to develop a resin-based modification system that could serve as a cost-effective and highly compatible alternative to conventional polymer additives. In this context, TPR with an aromatic hydrocarbon structure was incorporated into 70/100 penetration grade asphalt binder at different dosages, and the material behavior was evaluated using conventional and advanced rheological tests. The thermal and morphological properties of the additive were characterized through thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Subsequently, penetration, softening point, and rotational viscometer (RV) tests were performed on both unmodified and modified binders to determine their workability and temperature susceptibility parameters. Using a dynamic shear rheometer (DSR), temperature sweep tests were conducted within the range of 40 °C–70 °C at different frequencies to examine the complex modulus (G*) and phase angle (δ) values of the binders. Rheological data were mathematically expressed using the Cross and Carreau–Yasuda models, and the results were verified with high correlation coefficients. In addition, the Response Surface Methodology (RSM) was employed to analyze the multivariable interactions between the additive ratio and rheological parameters. Statistical analysis with a quartic model revealed that the optimal additive content was approximately 4.8%, which maximized the high-temperature performance of the binder. The findings demonstrated that the thermoplastic resin significantly improved the rheological performance of bitumen. The incorporation of TPR increased the softening point, reduced penetration values, and enhanced rutting resistance under elevated temperature conditions. Dynamic rheological measurements showed that the addition of TPR strengthened the elastic component of the binder, thereby improving resistance to permanent deformation, while simultaneously reducing the phase angle and imparting an elastomeric character. Furthermore, SEM images confirmed the homogeneous dispersion of TPR within the binder matrix. In conclusion, the petroleum-derived aromatic thermoplastic resin is considered an environmentally and economically feasible modification material that provides improvements in both mechanical and rheological performance of asphalt binders.