2017 FFG - Optimal asphalt mix aging procedure
Table of contents
Optimal asphalt mix aging procedure for consideration in computational dimensioning
Project staff
Contracting authority
Austian Research Promotion Agency
Project period
10/2017 - 09/2019
Abstract
Bitumen as an organic material is subject to aging, triggered primarily by oxidation and UV radiation. As a result, asphalt mixes also change their mechanical behavior during the service life; they become more brittle and harden, which leads to a lower resistance to cracking, the technical service life decreases as does the recyclability. For an optimization of the durability already during the mix design, as well as for the realistic determination of the technical service life in the computational dimensioning, it is necessary to be able to efficiently represent and evaluate aging effects within the scope of laboratory tests before construction. Currently available aging methods either do not represent field aging efficiently enough (duration) or not close to reality.
The aim of this research project is to evaluate existing aging methods in terms of realism, time and cost efficiency, complexity of application, adaptability and occupational safety. Methods already considered in the European Technical Specification (TS) 12697-52 will be taken into account. The method that emerges as the most suitable from this evaluation is subsequently optimized by a parameter study to the extent that it takes into account all relevant aging mechanisms (oxidation, UV radiation) and is thus both realistic and efficient. In a further step, the defined method is comprehensively validated. For this purpose, field-aged materials from six test sections, for which reserve samples of the initial bitumen are available, will be comprehensively examined at asphalt and bitumen level. Mixed materials will be generated in the laboratory with the reserve samples of bitumen, and test specimens will be aged using the method. These laboratory-aged samples are also analyzed for asphalt and bitumen levels. In addition to the mechanical tests, the materials are analyzed chemically and physically (spectroscopy and microscopy). This allows the laboratory aging method to be comprehensively validated against data from field-aged samples. In addition, it is ensured that field and laboratory aging are not only mechanically similar on a macroscopic level, but also that the chemical processes are correctly represented.
In parallel, models that are the basis for the computational dimensioning will be adapted to take into account the essential aging parameters in the future. If necessary, e.g. with regard to the development of cold cracks and their influence on the damage of the superstructure, new but already developed and tested models will be implemented. In a final step, the entire concept developed for a complete superstructure (surface course, binder course, base course), which is representative for the high-ranking German and Austrian road network, respectively, will be worked through as an example: from specimen production in the laboratory, via laboratory aging and determination of the mechanical material parameters, to comparative dimensioning with and without consideration of aging.
(Source: Austian Research Promotion Agency)