Characterization of asphalt recycling agents and evaluation of recycled asphalt binder aging properties.

摘要

Several experiments were conducted to develop tools for the analysis of asphalt recycling agents and for the production of recycled asphalts. In addition, experiments were conducted to study the physical properties and aging characteristics of both lime-treated tank asphalts and recycled asphalts.; A new high performance liquid chromatography technique was developed in which the asphaltene content is determined gravimetrically, the saturate content is determined by calibration of the refractive index response factor, and the total aromatic content (naphthene and polar aromatics) is determined by difference. Low saturate, low asphaltene, highly aromatic materials suitable for use as asphalt recycling agents were isolated through supercritical fractionation of asphalt feedstocks. Additionally, a new "universal" viscosity mixing rule was developed for aged asphalt/rejuvenating agent systems.; The aging studies conducted on both lime-treated tank asphalts and recycled asphalts indicate that the single most important factor affecting the properties of recycled asphalts is dilution of the existing asphaltenes present in the aged asphalt. Dilution of the aged asphalt was generally shown to result in superior aging kinetics and hardening susceptibilities. However, dilution was also shown to result in relatively poor rheological properties. Rejuvenating agent composition was shown to have some effect on the aging characteristics, particularly the hardening susceptibility. However, the effects of recycling agent composition generally could not be separated from the effects of dilution. Lime was shown to have relatively little effect on the kinetics of tank asphalts and on the viscosity temperature susceptibility of unaged tank asphalts and unaged recycled asphalts. However, lime treatment modestly improved the kinetics of recycled asphalts and modestly improved the hardening susceptibilities of both tank asphalts and recycled asphalts. Unfortunately, lime treatment was also shown to have serious detrimental effects on the low-temperature bending beam properties of recycled asphalts. Finally, the aging studies indicate that the pressure air vessel aging index is strongly correlated with the road condition hardening rates of recycled asphalts produced from a given aged asphalt. As a result, the pressure air vessel aging index can be used as an acceptable criterion for selecting a rejuvenating agent for a given aged asphalt.