The effect and mechanism of La2O3 on the anti-ultraviolet aging characteristics of virgin bitumen

Abstract

Modified bitumen was prepared by adding the rare earth oxide La2O3 to virgin bitumen to improve its anti-ultraviolet aging performance. An ultraviolet aging chamber was used to simulate the ultraviolet aging process of bitumen. Ultraviolet aged and non-aged bitumen were then tested to evaluate the ultraviolet aging degree from both the macro and micro perspectives and to analyze the effect of La2O3 on anti-ultraviolet aging performance. A dynamic shear rheometer, bending beam rheometer, infrared spectrum, and scanning electron microscope were used to conduct these tests. The results showed that, compared with virgin bitumen, the complex shear modulus, creep stiffness, creep rate, and sulfoxide index of 1–3% La2O3 modified bitumen after ultraviolet aging were reduced under the same aging condition. When the La2O3 content was 2%, the modified bitumen aging degree was the lowest, and its ratios of complex shear modulus, creep stiffness and creep rate were 1.26, 1.09, and 0.87 respectively. The sulfoxide index increment was 0.07, while the four corresponding indexes of virgin bitumen were 1.44, 1.11, 0.85 and 0.12. The SEM image analysis showed that the modification of bitumen by La2O3 was a physical modification. La2O3 that is evenly distributed in bitumen can absorb and reflect ultraviolet radiation, reduce the absorption of ultraviolet energy by bitumen molecules, improve the anti-ultraviolet aging performance, and effectively extend the service life of asphalt.