Evolution of the microstructure of unmodified and polymer modified asphalt binders with aging in an accelerated weathering tester

Abstract

This paper presents findings on the evolution of the surface microstructure of two asphalt binders, one unmodified and one polymer modified, directly exposed to aging agents with increasing durations. The aging is performed using an accelerated weathering tester, where ultraviolet radiation, oxygen and an increased temperature are applied to the asphalt binder surface. Ultraviolet and dark cycles, which simulated the succession of day and night, alternated during the aging process, and also the temperature varied, which corresponded to typical summer day and night temperatures registered in the state of Qatar. Direct aging of an exposed binder surface is more effective in showing microstructural modifications than previously applied protocols, which involved the heat treatment of binders previously aged with standardized methods. With the new protocol, any molecular rearrangements in the binder surface after aging induced by the heat treatment is prevented. Optical photos show the rippling and degradation of the binder surface due to aging. Microstructure images obtained by means of atomic force microscopy show gradual alteration of the surface due to aging. The original relatively flat microstructure was substituted with a profoundly different microstructure, which significantly protrudes from the surface, and is characterized by various shapes, such as rods, round structures and finally 'flower' or 'leaf' structures.

Evolution of Morphological and Nanomechanical Properties of Bitumen Thin Films as a Result of Compositional Changes Due to Ultraviolet Radiation

“…The molar absorptivity of bitumen increases rapidly with decreasing wavelength. ,− Almost all UV light is absorbed in the top 4.5 μm of the bitumen surface, although aging products could diffuse millimeters deep or further over time . The shallow penetration depth of UV radiation results in a hardened thin film on the aged bitumen surface. , Dynamic shear rheometry (DSR) of UV-aged bitumen showed an increase in viscosity when the samples were made to have a thickness of 150 μm or less. , An even more dramatic dependence on depth was observed in X-ray photoelectron spectroscopy measurements showing an enrichment in oxygen, sulfur, and nitrogen within the first few hundred nanometers of the surface . This dependence on depth makes it difficult to isolate the effects of UV exposure.…”

Design of performance evaluation model for warm mix recycled asphalt pavement based on fuzzy decision algorithm

“…The main problem of fuzzy mathematics evaluation method is to establish a membership function which meets the needs of practical problems. At present, there is still no good solution to the selection of membership function [10][11][12][13][14]. In the method of determining the membership function of practical problems, the approximate method is often used to establish the membership function of practical problems.…”

The Effect of Waste Engine Oil and Waste Polyethylene on UV Aging Resistance of Asphalt

“…During the service life of asphalt pavement, asphalt surface aging is vulnerable to take place due to the ultraviolet (UV) radiation from the sunlight. UV can change the chemical composition and chemical structure of asphalt and weaken the performance of asphalt pavement [19][20][21][22]. Bocci et al [23] designed a UV aging simulation experiment in the laboratory.…”