By Denis Jelagin, Alvaro Guarin, Ibrahim Onifade, Nicole Kringos, and Bjorn Birgisson (KTH)
The Division of Highway and Railway Engineering, Royal Institute of Technology (KTH) promotes advances in computational and experimental science in order to develop new materials, tools and systems for improved mobility, transportation safety and infrastructure durability. The group works on analysis and performance-based design of roads and tracks, management as well as operation and maintenance of roads.
Asphalt mixtures are inhomogeneous materials consisting of stones, sand and filler held together by a bitumen-based binder. The performance of asphalt mixtures with respect to permanent deformation, cracking, permeability and ageing is greatly affected by their internal structure. Understanding of micromechanical processes governing asphalt mixture performance requires tools for both determination of quantitative parameters describing asphalts internal structure, and for multi-physics modeling based on finite element (FE) method. FE analysis allows the quantification of microstructure influence on mixture performance, providing thus an innovative way for asphalt's material design optimization.
Reconstructed stone surface.
KTH Royal Institute of Technology uses Avizo software to visualize and characterize the internal structure of asphalt based on X-ray micro-CT data. Avizo software is used to measure the stone size distribution and orientation in asphalt mixtures, distribution and geometry of the contact zones between stones, as well as binder and air void distribution. Stones and stone-to-stone contacts provide a primary load carrying mechanism in compression and shear, especially at high temperatures. These parameters define to a greater extent the stone skeleton strength and its susceptibility to aggregate breakage and permanent deformation of asphalt mixture.
Once all three phases, i.e. stones, binder and air voids, have been segmented and analyzed with Avizo software, tetrahedral meshes are generated and exported to finite element analysis software. Performing the finite element analysis of different loading and thermal scenarios allows to gain further quantitative insight into the impact that the internal structure of asphalt has on its performance in the field. In the FE analysis example presented on the above figure, the influence of the air void structure on temperature gradient in asphalt mixtures is examined.
The division develops new long-lasting materials for road and rail, designing environmentally friendly materials and solutions, as well as studying the degradation and failure mechanisms of road surfaces and railway tracks.
Amira and Avizo are high-performance 3D software for visualizing, analyzing, and understanding scientific and industrial data coming from all types of sources and modalities.
Images and text are courtesy of KTH Royal Institute of Technology