ارزیابی آزمایشگاهی خصوصیات رئولوژیکی قیرهای اصلاح شده با نانورس مونت موریلونیت و پودر لاستیک فرآوری شده

The growing demand for durable and environmentally sustainable pavement materials has directed significant research efforts toward modifying asphalt binders with advanced additives. Among the various options available, montmorillonite nanoclay and reacted and activated rubber (RAR) have attracted particular attention due to their complementary characteristics. Nanoclay, with its layered silicate structure and exceptionally high surface area, is known to enhance the thermal stability, stiffness, and aging resistance of asphalt binders. On the other hand, RAR—derived from recycled waste tire rubber—improves elasticity and fatigue resistance while simultaneously addressing critical environmental concerns related to the disposal of end-of-life tires. The combined use of these two modifiers offers the potential for a synergistic effect, resulting in improved rheological behavior and long-term performance of asphalt binders under varying service conditions. This study was systematically designed to analyze the rheological behavior of asphalt binders modified with different proportions of montmorillonite nanoclay (2%, 4%, and 5% by weight) and RAR (15%, 20%, and 25% by weight) under a range of temperature conditions. The modified binders were subjected to a comprehensive testing program using a Dynamic Shear Rheometer (DSR), Multiple Stress Creep Recovery (MSCR), and Linear Amplitude Sweep (LAS) tests. Permanent deformation (rutting resistance) was evaluated using DSR at high temperatures ranging from 58°C to 82°C (specifically at 58, 64, 70, 76, and 82°C) under a frequency of 1.59 Hz (10 rad/s) and a constant strain of 12%. These tests were conducted on binders both before and after short-term aging with the Rolling Thin Film Oven (RTFO). Fatigue performance was assessed using the DSR in the intermediate temperature range of 16°C to 22°C (16, 19, and 22°C), also at 1.59 Hz, under a constant strain of 1.01%, applied on binders aged with the Pressure Aging Vessel (PAV) to simulate long-term service life. Following these assessments, MSCR tests were performed on short-term aged binders, and LAS tests were conducted on long-term aged binders to provide a holistic evaluation of rutting and fatigue resistance. The experimental results demonstrated that the optimal performance was achieved in binders containing 4% nanoclay and 25% RAR. From an engineering perspective, this composition resulted in substantial enhancements of both rutting and fatigue resistance. Specifically, the parameter G*/sinδ, a measure of rutting resistance, improved by 115% compared with the base binder, while G*·sinδ, indicative of fatigue resistance, increased by 87%. These improvements highlight the effectiveness of the nanoclay–RAR system in addressing the critical challenges of permanent deformation at high temperatures and fatigue cracking at intermediate temperatures. Furthermore, the MSCR results confirmed the significant reduction in non-recoverable creep compliance, while LAS outcomes demonstrated enhanced fatigue life, providing robust evidence of the synergistic effects between nanoclay and RAR. The findings of this research emphasize the potential of incorporating nanoclay and RAR as a hybrid modification strategy for asphalt binders, particularly in hot climate regions where pavements are exposed to severe thermal stresses and high traffic loads. Beyond the technical benefits, the use of RAR also offers an environmentally responsible solution by recycling waste tires into value-added infrastructure materials. The integration of advanced nanomaterials and recycled polymers therefore represents a promising approach to designing high-performance, cost-effective, and sustainable asphalt binders capable of extending pavement service life and reducing maintenance costs. This study contributes valuable insights for pavement engineers and researchers, demonstrating that the combined modification with nanoclay and RAR provides a balanced improvement of stiffness, elasticity, and durability, making it a viable candidate for next-generation asphalt technologies.