Author: Tan, Zhifei
Title: Investigation of the effects of rejuvenators on aged polymer modified friction course asphalt materials
Advisors: Leng, Zhen (CEE)
Degree: M.Sc.
Year: 2018
Subject: Hong Kong Polytechnic University -- Dissertations
Pavements, Asphalt -- Design and construction
Roads -- Maintenance and repair
Department: Faculty of Construction and Environment
Pages: xi, 66 pages : color illustrations
Language: English
Abstract: It is widely accepted that the aging of asphalt binder deteriorates the performance of asphalt pavement. Rejuvenators, with the potential to restore the viscoelastic properties,have gained considerable popularity in recent times for the maintenance of asphalt pavement and the reuse of reclaimed asphalt pavement (RAP). Nowadays, a number of rejuvenators have been used to rejuvenate the aged binder from organic-based to petroleum-based rejuvenators. However, there is a lack of standard methods to evaluate the effects of rejuvenators on the aged asphalt binder. Hence, the objective rejuvenators on aged asphalt materials, and therefore to guide the selection of rejuvenators using in asphalt pavement. Generally, the Superpave performance grading (PG) method is used to evaluate the performance of asphalt binders. Same as rejuvenated asphalt binders, this method is also adopted by the researchers to evaluate the performance of the rejuvenated asphalt binder. As the aged asphalt binder is restored to the original PG grading, this dosage of rejuvenator used is regarded as the optimal rejuvenator contents. However, from this study, it was found that even though the different types of rejuvenators are capable of recovering the aged binder to the same PG grading, the fatigue performance is significant different dependent on the rejuvenator used. Hence, the effects of rejuvenators on the fatigue performance of aged asphalt binder was also investigated.
Four types of commonly used rejuvenators were selected in this study. They were tall oil (TO), waste cooking oil (WCO), extract oil (EO) and aromatic oil (AO). Firstly, the aged asphalt binder was rejuvenated to the same high temperature PG grade by the rejuvenators. Then, the effects of rejuvenators on aged asphalt materials have been explored from asphalt binders, mastics and fine aggregate matrixes (FAMs). In asphalt binder level, the chemical, engineering, rheological and fatigue properties have been investigated. The chemical experiments of Fourier transformed infrared (FTIR) on rejuvenators and their rejuvenated asphalt binders identified the major compositions of rejuvenators and their effects on aged asphalt binder. In engineering properties, the viscosity as well as the rolling thin film oven (RTFO) loss have been measured. Viscosity results show that rejuvenators have the capability to recover the viscosity of the aged asphalt binder to the base binder (PG 76) level. However, RTFO loss results indicate that the rejuvenated asphalt binders are more susceptible to aging. To characterize the rehological performance of rejuvenated binder, frequency sweep (FS) test is performed on rejuvenated asphalt binders. The constructed master curves show that the impacts of different types of rejuvenators on rheological performance of rejuvenated asphalt binders are marginal. However, the fatigue performance from the linear amplitude sweep (LAS) test is significantly different. The fatigue life of WCO rejuvenated asphalt binder is double than the rejuvenated asphalt binders by other rejuvenators. This means that although the rejuvenators have the ability to recover the rheological properties of aged binder, the fatigue performance of aged asphalt binder would be greatly varied by rejuvenators. To demonstrate the influences of rejuvenators on the rheological and fatigue performance of rejuvenated asphalt binders, experiments on mastics and FAMs were conducted as well. Mastics, as the actual binder materials in asphalt mixture, the cohesive and adhesive properties of rejuvenated asphalt binders were considered in the mastic tests. The rheological performances of rejuvenated asphalt mastics display a good agreement with binder tests. However, LAS tests indicated that the cohesive performances were differed with rejuvenators. With regards to FAM, by considering fine aggregate, it can more accurately exhibit the performance of rejuvenated asphalt binders in asphalt mixtures. For the rheological properties,the similar tendency of complex shear moduli and phase angles were observed from the FS tests on FAM specimens. As to the fatigue performance, the rejuvenated FAMs' fatigue life lines of fatigue lives respect to strain levels were fitted and developed. The fatigue lives also showed a good correlation with the binder mastic test. Hence, the following conclusions can be summarized from this study: 1) Rejuvenators are capable of recovering the mechanical performance of aged binder to the level of original binder; 2) Since many rejuvenators are susceptible to aging, it is necessary to examine the anti-aging properties of rejuvenators; 3) The fatigue performance of rejuvenated asphalt materials is varied with the differences of rejuvenators and the fatigue properties should be considered in the selection of rejuvenators; 4) The rheological and fatigue performances on rejuvenated asphalt binder have a good agreement with mastic and FAM experiment; 5) WCO is an excellent rejuvenator candidate considering its superiors performance on fatigue and aging resistance.
Rights: All rights reserved
Access: restricted access

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