The deteriorating ecological environment and the concept of sustainable development have highlighted the importance of waste reuse. This article investigates the performance changes resulting from the incorporation of shellac into asphalt binders. Seashell powder-modified asphalt was prepared with 5%, 10%, and 15% admixture using the high-speed shear method. The microstructure of the seashell powder was observed by scanning electron microscope test (SEM); the physical-phase analysis of the seashell powder was carried out using an X-ray diffraction (XRD) test; the surface characteristics and pore structure of shellac were analyzed by the specific surface area Brunauer-Emmett-Teller (BET) test; and Fourier infrared spectroscopy (FTIR) qualitatively analyzed the composition and changes of functional groups of seashell powder-modified asphalt. The conventional performance index of seashell powder asphalt was analyzed by penetration, softening point, and ductility (5 °C) tests; the effect of seashell powder on asphalt binder was studied using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR) at high and low temperatures, respectively. The results indicate the following: seashell powder is a coarse, porous, and angular CaCO₃ bio-material; seashell powder and the asphalt binder represent a stable physical mixture of modified properties; seashell powder improves the consistency, hardness, and high-temperature performance of the asphalt binder but weakens the low-temperature performance of it; seashell powder enhances the elasticity, recovery performance, and permanent deformation resistance of asphalt binders and improves high-temperature rheological properties; finally, seashell powder has a minimal effect on the crack resistance of asphalt binders at very low temperatures. In summary, the use of waste seashells for recycling as bio-modifiers for asphalt binders is a practical approach.

Waste biomass powders and waste oils are promising sustainable modifiers for asphalt binders, but solid-phase biomass powders and oil-phase modifiers often have competing effects on high-temperature stability and low-temperature relaxation. In this study, peanut shell powder (PSP) and waste cooking oil (WCO) were combined at a fixed mass ratio of 1:1 to modify No. 70 base asphalt binder, and the material characteristics, physical properties, rheological responses, and chemical interactions of unaged PSP/WCO-modified asphalt binders with total modifier dosages of 5%, 10%, and 15% were evaluated. The results showed that PSP had a rough, wrinkled, and locally porous lignocellulosic structure and showed no obvious thermal decomposition near the preparation temperature of approximately 150 °C. As the PSP/WCO dosage increased from 0% to 15%, the softening point increased from 50.2 °C to 53.9 °C, while penetration decreased from 66.2 to 62.6 (0.1 mm) and ductility decreased from 74.0 mm to 69.5 mm, indicating increased binder consistency and improved high-temperature flow resistance. DSR and MSCR results showed enhanced high-temperature deformation resistance; at 15% dosage, Jnr at 3.2 kPa decreased from 2.35 to 1.25 kPa⁻¹, while R increased from 0.51% to 1.36%. However, BBR results showed increased creep stiffness and decreased m-value, indicating reduced low-temperature relaxation capacity. FTIR spectra showed no new strong characteristic absorption peaks, suggesting that the modification was mainly associated with physical blending, compositional regulation, and weak intermolecular interactions. The main novelty of this work is that it demonstrates a fixed-ratio PSP/WCO composite modification strategy that combines biomass-powder reinforcement with oil-phase regulation to improve the unaged high-temperature rheological performance of asphalt binders while promoting the resource utilization of peanut shells and waste cooking oil.