The ASPARi unit at the Department of Construction Management and Engineering is currently involved in a 4TU project studying the application of Fibre Optic Sensor (FOS) in asphalt to monitor certain process parameters. The FOS technology based on integrated photonics offers specific benefits including thermal mapping, damage detection and shape- and distributed sensing. Several challenges have been highlighted during pilot testing including the range of temperature detection capabilities, the loading/pressure sensing capabilities, preventing damage to the sensor and disturbing the asphalt layer during the installation process. The latter highlights the high-risk challenge of installing the sensor into the asphalt layer in a non-invasive manner (without disturbing the asphalt) so that temperature-, pressure-, shape detection and other parameters are accurately measured during the life cycle of the asphalt pavement. In short, sensors needs to be embedded in a manner conducive for highly accurate structural condition monitoring of the process.
The focus of this proposed Living Lab Project is therefore on the installation of FOS into existing asphalt layer(s) on the UT campus, so that the benefits of thermal mapping, damage detection, shape- and distributed sensing can be realised for constructed asphalt layers. Accurately monitoring key process parameters after construction using the appropriate sensor technology should provide more insight into the behaviour of the asphalt layer during its service life (especially during critical periods e.g. freeze-thaw cycles). This critical data can be used to develop strategies for extending the service life (durability) of asphalt pavements.
Seirgei Miller, Denis Makarov, Paul Havinga and Nirvana Meratnia - University of Twente
Sandra Erkens and Anupam Kumar - Technical University Delft
Jan van der Water - Ballast Nedam
Devrez Karabacak - Fugro
Three focal areas (outputs) are proposed:
1. Develop a robust, affordable and accurate condition monitoring system for asphalt layers based on heterogeneous sensor modality and reliable wireless communication
2. Install a prototype FOS system for asphalt condition monitoring which can guarantee long lasting and accurate monitoring, and
3. Demonstrate the concept on 2 roads on the UT campus.
Please contact Seirgei Miller (email@example.com) should you wish to participate in the project. There are several student and staff opportunities for participation in this multi-disciplinary project including the development of finite element models, infrastructure performance models, asset mangement strategies, distributed systems and IT related initiatives.
Project followers: 3
If our roads could talk!
Researchers and students of Civil Engineering's ASPARi group installed sensors into our UT campus Boerderijweg
Our roads carry us and our precious loads when we are on the move. Once paved they do their job for many years, accepting the battering of traffic and the weather silently, until they fail and need to be reconstructed. What if our roads could tell us how they feel? What If they could complain about (too) heavy loads? What if they could call out when they are at breaking point? What if our roads could talk to us? Would we treat them with more respect? Could we help them stay healthy for longer?
The Boerderijweg on our campus has a voice since the 7th December 2017! A group of researchers and students from Civil Engineering installed Fibre Optic and Radio Frequency Identification (RFID) sensors under the new asphalt surfacing layer. Civil Engineering's ASPARi unit successfully pitched this project to the Living Lab Campus program. The team held several fruitful planning meetings with the Facilities Bureau representative, André de Brouwer to discuss the details of the project. Lansink bv, the local contractor undertaking the construction work, joined the preparation a bit later. PhD intern Denis Makarov, assisted by Civil Engineering Master students Daan Brinkerink and Sjon van Dijk took responsibility for the installation of the sensors. Sjon and Daan completed their bachelor projects on the use of RFID and fibre optic sensors respectively and built up considerable experience in the use of sensors. Denis recently successfully developed a Real-time Process Control System for asphalt construction during his successful PDEng project and hopes to integrate more sensors measurements into the construction process in order to improve the quality and durability of our roads.
Installing the sensors
Four fibre optic sensor (FOS) lines and five passive RFID sensors were installed in the 3cm thick Stone Mastic Asphalt (SMA) layer at the Boerderijweg. Figure 1 shows the layout of the sensors. The RFID chips and two of the FOS lines will be used to conduct long-term temperature measurements of the asphalt layer during the road's use. While the temperature of the asphalt will be monitored year round, researchers are particularly interested in what is happening to the asphalt layer during extreme weather conditions viz. freeze-thaw cycles and high summer temperatures. Water ingress during very cold conditions and subsequent freeze-thaw cycles cause damage to the asphalt layer and sometimes leads to premature failure. Heat waves may result in a softening of the bitumen (the glue in the mixture) and stripping of the asphalt layer. This stripping mechanism may then lead to surface damage and premature failure of the layer.
Figure 1 - Locations of the fibre optic cables (yellow lines) and RFID sensors
Two FOS lines have been installed in the wheel path areas as shown above. These sensors will be used to measure strain given that the wheel path areas experience the most loading during usage. Researchers hope to build up a better understanding of the behaviour of the asphalt layer under various loading conditions e.g. heavy trucks, passenger vehicles and cyclists using the Boerderijweg. Overall, a detailed analysis of the temperature, strain and traffic data should lead to a better understanding of quality decay over time and harmful mechanisms that may cause early failure. Once we know how to deal with these mechanisms we can improve the quality and durability of our roads.
Testing a new infrared camera for monitoring temperature homogeneity
While the focus was on the installation of the sensors to monitor the asphalt's structural health condition over its lifetime, the research team also took the opportunity to test a new infrared camera mounted on the back of contractor Lansink's asphalt paver. This camera weighing 280g, will be used to monitor the temperature homogeneity of the asphalt behind the paver during construction operations and is meant to replace current sensors which are considered heavy (a linescanner with mounting equipment typically weighs more than 20kg) and is considered rather expensive (more than 12000 euros). Denis Makarov adapted the algorithms needed to process and visualize the raw data in real-time. The testing proved to be a success with the paver operator able to see the asphalt surface temperature progression on a laptop mounted next to his operator seat and the data captured faultlessly. Further testing of the camera's robustness, data transfer, data latencies, accuracy and most importantly, integration into the Real-time Process Control System, will continue when the asphalt paving season resumes in Spring 2018.
Opportunities for student learning
The sensor installation on the Boerderijweg provides good research opportunities here on the campus. Perhaps more important, is that it provides opportunities for students from various disciplines e.g. civil engineering, mechanical engineering and IT, to test the installed sensors, collect data, develop models and in general, be exposed to innovations right here on our campus. A true living lab experience!!! André Dorée, Chair of Markets and Organisation Dynamics and ASPARi spearhead states: "We expect that the Boerderijweg will tell us a true story to enhance road durability and to better predict road success and failure. This is of prime importance since road infrastructure provides the backbone for economies. Failing roads cause accidents and high costs to the economy. Road repairs are costly and obstruct the traffic. Experimentation on our UT-campus offers good opportunities for students, feeds the research and creates innovative practices."
The ASPARi network contractors that support our research initiatives are shown in the image below.
Here are some pics taken of the sensor installation process
Contractor cutting the grooves for installing the fibre optic lines
Daan Brinkerink connecting the interogator and other hardware
Paver with the lightweight infrared camera mounted below the canopy. The camera is used to monitor temperature homogeneity during paving.
Ready for the asphalt layer to be paved over the fibre optic line ... data collection time!!!
Researchers Seirgei Miller, Silu Bhochhibhoya and Denis Makarov sharing a light moment during the installation activties.