A Model for Oxidative Aging of Rubber-Modified Asphalts and Implications to Performance Analysis

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• 作者：Jason F. Chipps ; Richard R. Davison ; and Charles J. Glover
• 刊名：Energy & Fuels
• 出版年：2001
• 出版时间：May 2001
• 年：2001
• 卷：15
• 期：3
• 页码：637 - 647
• 全文大小：193K
• 年卷期：v.15,no.3(May 2001)
• ISSN：1520-5029

文摘

Oxidative aging of asphalt binders is a primary cause of binder-related long-term road failures.Viscosity hardening is primarily due to the oxidative conversion of polar aromatics to asphaltenes;oxidation is indicated by carbonyl formation. The aging of unmodified asphalts yields a constant,aging-temperature independent "hardening susceptibility" (HS) relation between viscosity changeand the growth of the infrared carbonyl peak. Crumb-rubber-modified asphalts (CRMA) exhibitsuperior aging characteristics, lower hardening rates, and, often, lower oxidation rates, throughoutthe aging simulation range. However, CRMA materials may exhibit a hardening susceptibilitythat varies with aging temperature, suggesting either enhanced diffusion resistance or a kineticcompetition between the oxidation sites of the rubber polymer and the asphalt's polar aromatics.This evidence suggests that the commonly accepted high-temperature, high-pressure, long-termaging technique is of questionable value when applied to CRMA materials. The agingcharacteristics of CRMA were found to depend most heavily upon the curing method, the fractionalcontent of the rubber, and the chemical composition of the binder. The curing method has amajor effect on the material and chemical properties. Curing at lower temperatures and shearrates leads to a mere introduction of the rubber material into the binder, producing a swollen,gelatinous particle phase, the aging consequences of which are difficult to assess. Progressivelyhigher levels of mixing shear and temperature partially degrade the long polymer chains andcross-link structures. Polymer chains freed by thermo-mechanical shear are integrated in thebinder, shielding or altering by competitive means the oxidation of the binder.