Investigation of the rheological properties of boron modified polymer bitumens

In this research, the use of boron minerals—particularly boric acid, one of Turkey's strategic underground resources—in combination with a reactive elastomeric terpolymer (RET) known as Elvaloy was investigated for bitumen modification. The main objective of the research is to transform Turkey's rich boron reserves into a value-added component in road construction, to scientifically assess the performance of domestic additives, and to contribute to sustainable road infrastructure by reducing foreign dependency. In the experimental setup, bitumen samples were modified by incorporating varying proportions of Elvaloy (1%, 2%) and boric acid (0.4%, 0.15%, 0.12%, 0.10%, 0.05%) in different combinations. The mixtures were blended at various temperatures (140 °C, 150 °C, 160 °C, 180 °C) for 2 hours at 1200 rpm followed by 30 minutes at 1400 rpm, resulting in a total mixing duration of 2.5 hours. The modified samples were subjected to comprehensive physical and rheological tests including penetration, softening point, viscosity, elastic recovery, flash point, specific gravity, aging (RTFOT, PAV), and dynamic shear rheometry (DSR). In addition, advanced characterization methods such as FT-IR spectroscopy were used to analyze chemical changes in detail. Experimental findings revealed that the addition of boric acid improved performance parameters such as hardness, softening point, and high-temperature resistance. However, performance at low temperatures declined as the temperature increased. On the other hand, Elvaloy enhanced the elasticity and long-term deformation resistance of the bitumen. The combined use of both additives offered significant advantages in terms of rutting resistance, high-temperature stability, and storage durability. These results indicate that polymer-modified bitumens can exhibit considerably superior performance compared to traditional binders and that boron minerals have the potential to serve as value-added materials in this context. In conclusion, this thesis demonstrates that boron-doped RET-modified bitumen components can be synthesized under laboratory conditions, their technical performance can comply with international standards, and they offer a strong alternative for the development of sustainable asphalt technologies. The data obtained not only contribute to the scientific literature but also present a feasible solution from economic, environmental, and engineering perspectives. The Elvaloy-modified samples containing boric acid can be considered suitable for application in moderate and high-temperature climates. Based on the study's findings, future field implementations and long-term durability assessments are recommended to further validate the real-world performance of this additive system.