Properties of Polyurethane-modified Asphalt Based on Castor Oil

To develop a new type of modified asphalt, castor oil-contained asphalt is obtained with green renewable castor oil instead of petroleum-based polyols. The second monomer-liquefied methylene diphenyl diisocyanate (MDI) is gradually added to a pitch system with shearing, and castor oil-based polyurethane (PU)-modified asphalt is prepared. The dosages of castor oil and second monomer MDI are calculated with isocyanate index R (—NCO/—OH)=1.8, and the modified asphalt with 10%-30% content of castor oil-based PU is synthesized. The performance of the modified asphalt is characterized through a conventional experiment. Experiment results show that the modifier in the asphalt is dispersed evenly, and the high-and low-temperature performance of the castor oil-based PU-modified asphalt is improved. The high-temperature grade of the asphalt is determined by performing the original grade test and thin film oven test on samples. On the basis of the high-temperature grade, the high-temperature performance of different asphalt samples after aging is analyzed and evaluated via a multiple stress creep recovery test. Test results show that the creep compliance of the modified asphalt is reduced significantly, and the recovery rate is increased compared with that of base asphalt. Increased elasticity and stiffening are achieved. With the increase in modifier dosage, creep compliance declines and the recovery rate increases simultaneously. The modification effect is also improved.