Christian-Doppler Laboratory for ¿Performance-based optimization of flexible pavements¿

01.07.2002 - 30.06.2010
Research funding project
The reliable assessment of the performance of asphalt requires suitable procedures and models for the evaluation of key material properties, representing its resistance to rutting, to cracking at low temperatures, and to fatigue failure under repeated load cycles. Asphalt shows a complex thermo-rheological behavior, with the low viscosity of asphalt at high temperatures (T >135 °C) being a necessary prerequisite for the construction and compaction process of high-quality asphalt layers. When the surface temperature reaches 70 °C during hot summer periods, however, this viscosity should be significantly higher in order to minimize the development of permanent deformations (rutting). The desirable increase of viscosity and, hence, increase of stiffness with decreasing temperature at hot and medium temperatures (0 < T < 70 °C) are, on the other hand, disadvantageous at low temperatures (T < 0 °C), causing low-temperature cracking in asphalt pavements. This optimization problem concerning the behavior of asphalt at different temperature regimes is the objective of the Christian Doppler Laboratory ¿Performance-Based Optimization of Flexible Road Pavements¿ (TU Wien). For the optimization process of a multi-composed material such as asphalt, three different modes can be distinguished: 1. variation of mixture characteristics (e.g., bitumen/aggregate-ratio), 2. change of constituents used (e.g. different bitumen or filler type), and 3. allowance of additives (e.g., polymers to modify the bitumen). Within this research project, a multiscale model for asphalt shall be developed. Hereby, the amount and type of bitumen, filler, and aggregate serve as input parameters, allowing us to cover a wide range of asphalt mixtures resulting from the given modes of optimization. The multiscale model for asphalt is characterized by four additional observation scales below the macroscale, namely (i) the bitumen-scale (asphaltenes and maltenes), (ii) the mastic-scale (bitumen + filler), (iii) the mortar-scale (mastic + aggregate with ø < 2 mm), and (iv) the asphalt-scale (mortar + aggregate with ø > 2 mm). Within each observation scale, the characteristics (such as structure and material properties) of the constituents present at this scale are taken into account. Moreover, changes in scale characteristics, resulting from mechanical loading and/or environmental conditions may be considered at the respective scale of observation. The goal of the multiscale model is the determination of macroscopic material parameters (key properties) which serve as input for macroscopic analyses of flexible pavements. These parameters are obtained by means of upscaling procedures, bridging the scales from the bitumen-scale to the macroscale. For the assessment of the used upscaling techniques, so-called verification experiments are performed in addition to identification experiments. The latter are used for identifying material characteristics at the different scales of observation. Following this hybrid character of the research work, comprising theoretical work regarding the development of appropriate upscaling schemes and experimental work (mainly carried out at the laboratory of the Institute for Road Construction and Maintenance, TU Wien) for either identification or verification, upscaling of key properties of asphalt provides the basis for the assessment of the risk of low-temperature cracking, fatigue failure, and permanent deformations (rutting).

People

Project leader

Project personnel

Institute

Grant funds

  • Christian Doppler Forschungsgesells (National) Christian Doppler Research Association (CDG)

Research focus

  • Special and Engineering Materials: 30%
  • Computational Materials Science: 35%
  • Modeling and Simulation: 35%

Keywords

GermanEnglish
flexible Straßenbefestigungflexible pavements
Asphaltasphalt
Mehrskalenmodellmultiscale modeling
Mikromechanikmicromechanics
HomogenisierungHomogeneization

External partner

  • ENVIRO OEG Environmental Research Group
  • Institut für Verkehrswissenschaften

Publications