The pros and cons of using calcium lignosulfonate as a recycled anti-aging additive on engineering properties of bituminous mastics

Abstract

High temperature and traffic loading are two primary threats for asphalt pavement during the pavement's life cycle. The mentioned threats lead to significant distractions, namely bitumen's oxidative aging, rutting, and fatigue failure. In this study, calcium lignosulfonate (CLS) obtained from lignin was investigated as an anti-aging bitumen additive. After morphology analysis of CLS particles based on field emission scanning electron microscopy (FESEM) technique, the CLS was mixed with the bitumen of 60/70 penetration grade at four quantities (i.e., 5%, 10%, 15%, and 20%). Then, the rolling thin film oven test (RTFOT) was used to simulate bitumen aging. In the next step, physical tests (penetration, softening point, and ductility), rheological tests (rotational viscosity and dynamic shear rheometer), and performance tests (multiple stress creep recovery and linear amplitude sweep) were conducted on both aged and un-aged samples. Finally, to evaluate the change of bitumen's chemical components during the aging process, the Fourier transform infrared spectroscopy (FTIR) was carried out. Results showed that CLS particles had a bumpy structure. Moreover, the addition of CLS into the bitumen increased the stiffness and high-temperature performance of bitumen. Although CLS modified bitumen needed more energy for mixing and compaction to compare with virgin bitumen, CLS modified bitumen had lower rutting susceptibility than virgin one. The presence of CLS within the bitumen increased the binder's brittleness, leading to fatigue life degradation. Based on FTIR analysis and aging indices, CLS as a recycled bitumen additive can significantly inhibit bitumen's oxidative reaction.