老化对废机油再生沥青流变特性的影响及机理

Influence and Mechanism of Aging on the Rheological Properties of Recycled Asphalt Binders with Waste Engine Oil

沥青再生技术以降低环境污染、节约资源和提高成本效益等优点在路面工程中被广泛应用。诸多研究集中于再生沥青是否能恢复其初始性能,而对再生沥青二次老化过程中的性能变化关注较少。因而本工作分别对原沥青、老化沥青和废机油再生沥青进行不同时间段的老化模拟,借助动态频率扫描和傅里叶红外光谱试验,对比分析三种沥青在不同老化时间下的流变性能、低温抗裂性能、化学官能团的变化规律,探索其性能变化与官能团变化间的内在联系。发现再生沥青在老化过程中的流变性能、抗裂性衰减过程与原沥青类似,均在老化初期衰减较快,老化后期衰减较慢,且再生沥青的流变性能和抗裂性衰减幅度均大于原沥青;再生沥青与原沥青的抗裂性在老化初期相差较小,随着老化时间的延长两者的抗裂性差距逐渐增大,且再生沥青的抗裂性逐渐接近于老化沥青;老化沥青的流变性能和抗裂性在老化过程中衰减较缓慢;再生沥青与原沥青的羰基指数均随老化时间的延长先快速增长后缓慢增长,但两者之间的羰基指数差值逐渐增大,而老化沥青的羰基指数随老化时间的延长呈近似线性增长;三种沥青在不同老化时间下的G-R常数与羰基指数有较好的相关性,但沥青种类不同,两者之间的关系式不同,且沥青经历的老化条件不一样,其关系式也不相同。结果表明,在老化过程中再生沥青中的再生剂挥发和氧化完后,其老化程度逐渐接近于老化沥青,其流变性能和抗裂性能优势不再体现。

Asphalt recycling technology is widely applied in pavement engineering because of its advantages of reducing environmental pollution, saving resources and improving cost-effectiveness. Many studies focus on whether recycled asphalt can restore its initial performance, but pays less attention to the change of performance of recycled asphalt in the re-aging process. In this work, the thermal oxygen aging tests were carried out for the original asphalt, aged asphalt and waste engine oil recycled asphalt at different aging durations respectively. Then the rheological pro-perties, low-temperature crack resistance and chemical functional groups of the three kinds of asphalt at different aging times were compared and analyzed based on the frequency sweep test and Fourier infrared spectroscopy test, and the relationship between the variation of the perfor-mances and that of chemical functionas was investigated. It was found that the rheological property of recycled asphalt was similar to the original asphalt in the reaging process. The rheological property and cracking resistance of these two kinds of asphalt decreased faster in the earlier aging stage and slower in the later stage, and the decrease range of recycled asphalt was greater than the original asphalt. At the initial stage of aging, the difference of cracking resistance between recycled asphalt and original asphalt was small. With the increase of the aging time, the difference between the two kinds of asphalt increased, and the cracking resistance of recycled asphalt was close to the aged asphalt gradually. The rheolo-gical property and cracking resistance of aged asphalt decreased slowly all the aging time;the carbonyl index of the recycled asphalt and original asphalt increased rapidly at first and then slowly with the increase of aging time, but the differences of carbonyl index between the two kinds of asphalt increased with the increase of aging time. And the carbonyl index of the aged asphalt increased approximately linearly with the increase of aging time. There were good correlations between G-R constant and carbonyl index of these three kinds of asphalt at different aging time, but the correlations were asphalt types dependent. The correlations were also different at different aging conditions. The results show that after the volatilization and oxidation of the regenerant of recycled asphalt during the re-aging process, the aging degree of recycled asphalt was gra-dually close to the aged asphalt, and the advantages of rheological properties and cracking resistance of recycled asphalt were no longer reflected.