Molecular dynamics simulation and experimental analysis on fluidity improvement of liquid rubber modified asphalt binder

Liquid styrene-butadiene rubber (LSBR) has been used as a modifier to improve high-temperature storage stability and cracking resistance of asphalt binder. However, the interaction mechanism between LSBR and asphalt binder at both micro and macro scales has not been well understood. In this study, the intermolecular dynamics, rheological and chemical properties of liquid rubber modified asphalt (LRMA) binder by laboratory experiments and molecular dynamics simulation. Five LSBR dosages (0, 0.5, 1.0, 1.5, 2.0, and 2.5% by weight of asphalt binder) were applied to prepare the LRMA binders. Frequency sweep, performance grading, and multiple stress creep recovery (MSCR) tests were conducted to assess the intermediate- and high-temperatures rheological properties of modified asphalt binders. Fourier transforms infrared (FTIR) spectroscopy was applied to evaluate the chemical properties. Molecular dynamics (MD) simulation was performed to evaluate compatibility and molecular mobility during self-healing process. The results indicated that the addition of LSBR improved the fluidity of asphalt binder at intermediate- and high- temperature, and also enhanced the susceptibility to temperature changes. FTIR results showed that LSBR could effectively delay aging of asphalt binder and ameliorate the service performance degradation. The MD simulation results indicated that the addition of LSBR could improve the solubility of different components in asphalt and the homogeneity of asphalt system. LRMA had a better capability to heal micro-crack than the unmodified asphalt binder. LSBR could improve the fluidity of base asphalt and aged asphalt. It is feasible and appropriate to use liquid styrene-butadiene rubber to improve fluidity of asphalt to meet the requirements of construction and production. Keywords: asphalt fluidity, molecular dynamics simulation, liquid styrene-butadiene rubber, self-healing, rheological property.