Abstract
Asphalt suffers from a series of aging processes in the natural environment. This is a significant factor in asphalt pavement diseases. Research of the properties of the decay processes in the natural weathering of asphalt will be helpful in distinguishing the characteristics of the various types of asphalt and in the selection of pavement materials. Neat asphalt A70, a styrene-butadiene-styrene- (SBS-) modified asphalt, and crumb-rubber-modified asphalt AR are exposed to outdoor conditions to weather naturally. This process is traced by testing the basic physical properties and the surface free energy of asphalts, using the sessile drop method. Results illustrate that the basic physical properties of asphalt change significantly during the natural weathering process and that the rubber asphalt has the superior aging resistance, while the neat asphalt A70 has a high aging susceptibility. Furthermore, the presence of the SBS and rubber-powder modifiers transforms the change trend of the surface free energy of neat asphalt. The adhesion work between aggregate and asphalt can be used to quantitatively evaluate the adhesive properties between them. Meanwhile, the presence of moisture between the asphalt and aggregate changes cohesive failure into adhesive failure.
Highlights
In the natural environment, asphalt will undergo complex physical and chemical reactions under the influence of sunlight, oxygen, and heat and lead to the deterioration of asphalt performance [1,2,3]. e adhesion failure of asphalt that manifests as the peeling off from the aggregate surface is another important factor that affects the durability of the asphalt pavement [4,5,6]. us, understanding the physical and adhesive properties of the naturally weathering asphalt is crucial.Currently, research on the simulation of the aging of asphalt is widespread
The methods of the laboratory simulation of the asphalt sample still cannot reflect the natural environment fully. us, to study the real situation of asphalt aging in the natural environment, some researchers are exposing modified asphalts to outdoor conditions to subject them to natural weathering for one year at most [2, 15, 16]. is is insufficient time for achieving a simulation of the entire service life of asphalt exposed to outdoor conditions
Asphalt will suffer from a series of complex physical and chemical reactions in the natural environment because of sunlight, heat, oxygen, and moisture
Summary
Research on the simulation of the aging of asphalt is widespread. Ese standard laboratory-aging methods are the shortterm and long-term aging simulations of asphalt [8,9,10,11]. To simulate natural weathering conditions optimally, researchers evaluate the performance of asphalt after accelerated weather aging. The methods of the laboratory simulation of the asphalt sample still cannot reflect the natural environment fully. Us, to study the real situation of asphalt aging in the natural environment, some researchers are exposing modified asphalts to outdoor conditions to subject them to natural weathering for one year at most [2, 15, 16]. Is is insufficient time for achieving a simulation of the entire service life of asphalt exposed to outdoor conditions The methods of the laboratory simulation of the asphalt sample still cannot reflect the natural environment fully. us, to study the real situation of asphalt aging in the natural environment, some researchers are exposing modified asphalts to outdoor conditions to subject them to natural weathering for one year at most [2, 15, 16]. is is insufficient time for achieving a simulation of the entire service life of asphalt exposed to outdoor conditions
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