Abstract
Warm-mixed asphalt (WMA) has the characteristics of low mixing temperature and energy consumption, which makes it more suitable than hot-mixed asphalt for plateau regions (the altitude is above 500 m, and the terrain is relatively flat or has a wide area with certain undulations). However, WMA is subject to severe ultraviolet (UV) aging because the UV radiation in plateau areas is more intense. The asphalt’s aging changes its rheological properties inevitably, and thus degrades the asphalt pavement’s performance. Accordingly, the purpose of this paper is to investigate the effect of UV and oxygen coupling aging on WMA’s rheological properties and functional group index. Temperature and frequency sweep tests were performed with a dynamic shear rheometer. At the same time, the functional group index was used as an indicator to compare the changes in the WMA’s infrared spectrum before and after UV aging. The results showed that WMA’s elasticity increased and its viscosity decreased after aging with UV. Under the condition of UV–oxygen isolation, as the aging period increased, the WMA’s rutting factor increased gradually. The degree of improvement was greater than that under the condition of oxygen isolation. In contrast, the time required for the WMA’s complex shear modulus to recover under the condition of UV–oxygen coupling was delayed. An increase in the peak value of infrared spectrum indicates that the WMA has undergone oxygen aging. The presence and change in the carbonyl group reflects the degree of the WMA’s UV aging, and the UV aging condition had a greater effect on the peak values of the carbonyl and sulfoxide groups.
Highlights
Asphalt pavement has many advantages over cement concrete pavement such as flat surface, low noise and vibration, comfortable driving, a short construction period, and easy maintenance, so it is the form of pavement used most commonly for high-grade pavement in the highway industry.Asphalt is the main adhesive material in asphalt mixtures and is used widely in the fields of pavement construction because of its important properties including viscosity, viscoelasticity, and water resistance.As asphalt binder has higher viscosity, asphalt must be heated to a higher temperature in the production and construction processes
The purpose of this study was to study the effects of different UV–oxygen coupling aging conditions on the rheological properties of Warm-mixed asphalt (WMA) to obtain its rheological properties under UV aging, and to improve its anti-UV aging
As the aging time continued to increase, when it reached 200 h, the complex shear modulus had increased significantly. These results show that UV aging has a great influence on the total resistance of asphalt under repeated shear deformation, and the influence on the complex shear modulus varies as the UV aging time increases
Summary
As asphalt binder has higher viscosity, asphalt must be heated to a higher temperature in the production and construction processes. The range in the production temperature in the process of mixing is 150–160 ◦ C and 170–180 ◦ C for normal petroleum asphalts and polymer modified asphalts, respectively. A hot mix asphalt mixture consumes considerable energy in the process of mixing, transportation, paving, and compaction because of the high construction temperature. It emits a large amount of smoke and harmful gases that have adverse effects on Materials 2020, 13, 4216; doi:10.3390/ma13194216 www.mdpi.com/journal/materials
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