Engineering performance of asphalt pavement highly depends on the properties of bitumen, the bonding material to glue aggregates and fillers together. During the service period, bitumen is exposed to sunlight, oxygen and vehicle loading which in turn leads to aging and degradation. A comprehensive understanding of the aging mechanism of bitumen is of critical importance to enhance the durability of asphalt pavement. This study aims to determine the relations between micro-mechanics, chemical composition, and macro-mechanical behavior of aged bitumen. To this end, the effect of aging on micro-mechanics, chemical functional groups, and rheological properties of bitumen were evaluated by atomic force microscope, Fourier transform infrared spectroscopy and dynamic shear rheometer tests, respectively. Results indicated that aging obviously increased the micro-surface roughness of bitumen. A more discrete distribution of micromechanics on bitumen micro-surface was noticed and its elastic behavior became more significant. Aging also resulted in raised content of carbonyl, sulfoxide, and aromatic ring functional groups. In terms of rheological behavior, the storage modulus of bitumen apparently increased after aging due to the transformation of viscous fractions to elastic fractions, making it stiffer and less viscous. By correlation analysis, it is noted that the bitumen rheological behavior was closely related to its micro-mechanics.

Lignin accounts for approximately 30% of the weight of herbaceous biomass. Utilizing lignin in asphalt pavement industry could enhance the performance of pavement while balancing the construction cost. This study aims to evaluate the feasibility of utilizing lignin as a bitumen performance improver. For this purpose, lignin derived from aspen wood chips (labeled as KL) and corn stalk residues (labeled as CL) were selected to prepare the lignin modified bituminous binder. The properties of the lignin modified binder were investigated through rheological, mechanical and chemical tests. The multiple stress creep recovery (MSCR) test results indicated that adding lignin decreased the J_nr of based binder by a range of 8% to 23% depending on the stress and lignin type. Lignin showed a positive effect on the low temperature performance of asphalt binder, because at −18 °C, KL and CL were able to reduce the stiffness of base binder from 441 MPa to 369 MPa and 378 MPa, respectively. However, lignin was found to deteriorate the fatigue life and workability of base binder up to 30% and 126%. With bituminous mixture, application of lignin modifiers improved the Marshall Stability and moisture resistance of base mixture up to 21% and 13%, respectively. Although, adding lignin modifiers decreased the molecular weight of asphalt binder according to the gel permeation chromatography (GPC) test results. The Fourier-transform infrared spectroscopy (FTIR) test results did not report detectable changes in functional group of based binder.

This paper presents a laboratory study aiming to characterise the influences of aggregate micro-texture on the skid resistance under consideration of different wavelengths. To achieve this objective, 11 kinds of aggregates were used to prepare aggregate specimens. Micro-Deval (MD) and Aachen Polishing Machine (APM) were utilised to represent the changes in aggregate morphology which is caused by traffic loading. The Wehner/Schulze (W/S) test was used to measure the skid resistance. A high-resolution profilometer was utilised to collect the surface topography of the specimens. The two-dimensional power spectral density of the aggregate specimens was calculated based on the collected surface topography to investigate the differences in texture resulting from abrasion and polishing. Furthermore, the key wavelength ranges of the pavement surface texture responsible for the skid resistance is identified. The key wavelength range was then divided into four subranges; thereafter, the effect of the micro-texture on the skid resistance is investigated. Analyses show that the MD and APM affected different wavelength ranges of the texture. The most influential wavelength range for the skid resistance is found to be 32–128 µm. Mineral properties and the composition of aggregate directly affect the skid-resistant performance as well as the polishing resistance.