Multi-Scaling and Microstructure of Road Materials
The research focus area "Multi-Scaling and Microstructure" investigates road materials at a fundamental scale where performance enhancing or limiting phenomena find their origin. The goal is to further the fundamental understandig of:
- road materials behavior with respect to environmental effects such as water and temperature,
- interaction of bitumen with other substances, in particular with minerals
- targeted development of modern road materials
In order to characterize the microstructure of asphalt concrete environmental scanning electron microscope (ESEM), optical microscope, Atomic Force Microscopy (AFM) and computer tomography have been used. Other methods are continuously investigated for their suitability for asphalt concrete materials. Research conducted has shown that well performing and sub-optimally performing pavementd display evidence of suboptimal microstructure that could lead to premature failure. Microstructural features due to different compaction methods, polymer modification and homogenity of void structure can be investigated.
At Empa using a novel test set up the tensile behavior of viscoelastic bituminous films confined between mineral aggregates or steel as adherends, can be investigated in the brittle and ductile regimes. Uniaxial specimens can be fabricated employing a prototype set up developed in this allowing construction of micro-scale thin films and visualization of failure phenomena. The effect of key parameters, namely, temperature, binder type, adherend type (stainless steel and mineral aggregate), and water conditioning can be investigated.
In cooperation with other focus areas in the lab, information obtained from the microstructural, micro-tensile and other related characterization techniques is used to determine the origin of performance limiting or enhancing phenomena. Examples of materials of current interest are porous asphalt, recycled asphalt and multi functional pavement materials.