Characterization of bituminous materials using PiezoMEMS resonators
Bitumen is one of the heaviest products in refining of suitable crude oils and thus, an organic material with a complex chemical composition. Of the roughly 100 Mt (metric megatons) of bitumen applied per year worldwide, about 85% go into asphalt road pavements, 10% into roofing and 5% into other applications. In Europe, 95% of all paved roads are made of bituminous bound pavements. Bitumen is therefore a construction material of crucial importance for traffic infrastructure and other civil engineering structures.
Bitumen aging and PiezoMEMS
Since bitumen aging manifests in pronounced changes in viscosity, latest developments in the field MEMS sensors can be applied for characterization. Up to now, mostly bench scale equipment was proposed for the characterization of bitumen. For a continuous in situ monitoring of key material parameters, however, micro-machined, low-power sensors of both high sensitivity and high robustness are requested offering the potential for wireless readout of the output signals.
Challenges for the sensor
For high electrical output signals in such a high-viscous environment, MEMS cantilevered sensor are driven in resonance while interacting with the fluidic environment and their characteristic mechanical response spectrum is sensed. The coupling between mechanical movement and electrical signals is provided by integrated piezoelectric elements. The viscous damping in fluidic environments directly impacts key characteristics of the mechanical response such as resonance frequency and quality factor. This enables the measurement of the damping forces and thus allows the determination of physical fluid parameters such as viscosity and density.
In this project, a measurement setup shall be developed to test the MEMS based high viscosity sensors at various temperatures with different bitumen samples and other high viscosity test fluids for calibration purposes. This setup will be used to gain a deep understanding of the correlation between the mechanical response of the MEMS resonator and the varying visco-elastic properties of bitumen and other test fluids. Furthermore, modelling of the resonator performance when exposed to bitumen should deepen the knowledge on both the structure-fluid interaction in such a complex fluid like bitumen and to give guidelines for future MEMS sensor improvements.
Projektass. Suresh Alasatri
Project Assistant, Research Unit of Microsystems Technology
Privatdoz. Dipl.-Phys. Dr.techn. Michael Schneider
Assistant Prof., Research Unit of Microsystems Technology
The project is part of the Christian Doppler Lab for chemo-mechanical analysis of bituminous materials.