Innovative application of coffee grounds oil as an asphalt modifier: Extraction, preparation, and rheological properties

This study innovatively utilized coffee grounds oil (CGO) extracted from waste coffee grounds to modify base asphalt, aiming to promote sustainable reuse of coffee waste. The effects of modifier dosage, type, and aging conditions on the rheological properties of asphalt were investigated. After determining the extraction protocol, coffee grounds oil-modified asphalt (CGOA) and waste cooking oil-modified asphalt (WCOA) were prepared and subjected to short-term aging. Fourier transform infrared spectroscopy (FTIR) analyzed the modification mechanism, while temperature sweep, frequency sweep, bending beam rheometer, and multiple stress creep recovery (MSCR) tests assessed the rheological properties at high and low temperatures. Results showed that before aging, CGO improved thermal stability at medium to high temperatures and enhanced deformation and stress relaxation at low temperatures, though it reduced rutting resistance at high temperatures. After aging, CGOA with a dosage limited to 4 % exhibited rheological properties approaching base asphalt and improved the viscoelasticity of aged asphalt. In comparison, WCOA demonstrated significantly weaker performance, particularly after aging. This study provides practical insights into the novel application of CGO in pavement engineering.