废油再生沥青二次老化后的性能与组分变化

目前对于回收废油再生沥青的研究热点集中于其是否能使老化沥青的各项性能恢复至原有水平，而对再生沥青二次老化后的性能损失关注较少。基于此，研究采用具有代表性的废食用油（RCOB）、废生物油（RBOB）、废机油（REOB）再生剂对具有13年服役历史的70^#沥青进行再生，并对再生沥青进行RTFOT，PAV20h，PAV40h三阶段的老化模拟，跟踪每阶段老化后再生沥青的基本指标、高温稳定性和低温抗裂性的变化，对各阶段老化后的再生沥青组分变化进行分析，探索其性能改变与组分变化间的深层原因。研究结果表明：3种再生剂都能以提升轻质组分的方式将回收沥青的基本性能恢复至原始水平附近；RCOB以提供饱和分为主，但其会在RTFOT后迅速流失，致使各项性能在该阶段迅速下降，继续老化后，组分状态趋于稳定，性能下降也逐渐缓和；REOB再生沥青由于原料中存在机械金属残渣构成的灰分，其对沥青的氧化和缩聚存在催化作用，导致REOB再生沥青在长期老化后性能迅速下降且没有逐渐稳定的趋势；RBOB再生沥青由于具备相对稳定的胶体结构，且不存在对老化起催化作用的灰分，在3阶段老化中其组分损失过程是最稳定有序的，因此，其性能也表现为阶段性的合理损失；研究基于组分变化提出了新指标"测试沥青与原始沥青各组分间的平均偏差σ"来衡量沥青的老化程度，该指标与针入度，延度，软化点，低温临界开裂温度，135℃高温黏度这5个指标具有显著相关性。研究表明对于再生沥青的评价，不能仅注重再生后与原始沥青的性能差距，应更多地集中到再生沥青二次老化后的性能损失上，以筛选出真正性能优良，抗老化能力显著的再生剂产品。

Research on Change of Performance and Component of Recycled Oil Regenerated Asphalt During Secondary Aging

There have been many studies focused on whether recycled oil could be used as an asphalt regenerant to make the properties of aged asphalt return to original level or not. However, only little attention was paid to the performance loss of these regenerated asphalts after secondary aging. In this study, three representative asphalt regenerates taking different recycled oil as raw material including:recycled cooking oil bottom (RCOB), recycled bio-oil bottom (RBOB) and recycled engine oil bottom (REOB), were used to regenerate an aged matrix asphalt which has been in service for 13 years. Three-staged aging treatment including RTFOT, 20h PAV and 40h PAV were conducted to simulate the natural aging process. After each aging stage, the performance decreases of these regenerated asphalts were investigated, including:basic properties (penetration, softening point, ductility), high-temperature stability and low-temperature crack resistance. At the same time, the underlying causes of this decreases above were explored by the asphalt component analysis experiment based on thin layer chromatography-flame ionization detector (TLC-FID). The results show that, all three asphalt regenerants can restore the basic properties of the aged asphalt to original level by increasing the light components. However, the light components provided by RCOB are mainly saturates that evaporated rapidly after RTFOT, and the components proportion of RCOB returned to the same level as before regeneration, which leads to the significant performance decline. As for REOB, it brings a small number of ashes, which are mainly residual caused by metal friction. The ashes may catalyze the oxidation and polycondensation of asphalt, which led to the rapid decline of the performance of REOB regenerated asphalt after long-term aging. RBOB regenerated asphalt shows relatively stable colloidal structure, and there is no existence of ashes which would catalyze the aging, so its components transfer process is the most stable and orderly in all three regenerated asphalts. The study proposed a new index used to measure the aging degree of the asphalt, which is average deviation of components between the test asphalt and the original (marked σ). σ has a significant correlation with the five indexes of asphalt including penetration, ductility, softening point, low-temperature critical cracking temperature, and high-temperature viscosity at 135℃. The above results indicate that, as evaluating regenerated asphalts, performance gap before and after regeneration should not be focused on only and more attentions should be paid to the performance loss after secondary aging. Only in this way can asphalt regenerant with good properties and aging resistance be found for actual production.