Bitumen Aging-Laboratory Simulation Methods Used in Practice and Selected Directions of Research on New Methods

Abstract

Changes in the properties of bitumen binders that occur as a result of aging have a huge impact on the durability of products produced from them. In particular, asphalt pavements, which constitute the most common use of petroleum bitumen, are susceptible to damage resulting from the increasing stiffness of the bitumen during its life cycle. Increased stiffness of asphalt pavements reduces the pavement resistance to low-temperature cracks and fatigue cracks, ultimately leading to the loss of their functional properties and the need for road repair. The rate of changes in bitumen properties is influenced by many factors, the most important of which are environmental conditions, technological parameters of binder processing, and physicochemical properties. The greatest impact on minimizing the adverse effect of aging is the use of bitumen suitably resistant to aging, and changing the technological parameters of its application. This article reviews the literature and standardized test methods of bitumen aging, with a focus on the methods that are most often used in practice, to evaluate the suitability of bitumen for use in road construction. The presented methods are limited to aging simulation. This mini-review presents the most important stages of aging procedures, their advantages and limitations, as identified by the authors of this publication for different types of bitumen. Moreover, the most important directions of developments in the field of new laboratory aging tests are highlighted. The suggestions are based on the industrial practice of the authors of this review, taking into account identified demands for quality control in the industry.

Keywords: binder; bitumen; chemical degradation; laboratory aging methods; oxidation; roads.

Figure 1

Schematic for the group separation of chemical constituents in bitumen.

Figure 2

Model of the chemical structure of bitumen developed in the SHRP program [13]. The polar hydrocarbon systems are shown in black, while the white denotes the area representing nonpolar hydrocarbons.

Figure 3

Aging effects on binder properties represented by the viscosity ratio index during the life of the bitumen [14].

Figure 4

Photograph of a set of pans and an oven for aging bitumen by the TFOT method.

Figure 5

Oven and squirrel cage-type fan for aging by the RTFOT method (EN 12607-1:2014).

Figure 6

Schematic of RFT aging setup [EN 12607-3:2014].

Figure 7

Diagram of the PAV aging setup [EN 14769-2012].

Figure 8

Schematic diagram of the RCAT aging apparatus (EN 15323:2017).