EU Research Project ASPHALT Successfully Completed

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Written by Jaroslaw Jurasz

Created on Saturday, 22 September 2012 18:09

A 978Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Better road quality through trouble-free processes at construction sites

As few construction sites as possible, finished as quickly as possible--that's what everyone who uses roads wants. Only if all operations at construction sites proceed without trouble can this be attained. Additionally, if processes are reciprocally coordinated with precision, work can be completed more quickly and with optimum results. Optimum results equal top-quality road surfaces that require repair work much less frequently. Thus, the number of construction sites is reduced--saving the money and time expended for premature improvement or repair work. This principle was tested by the EU-initiated project ASPHALT (Advanced Galileo Navigation System for Asphalt Fleet Machines) for satellite navigation and fleet management.

Trucks coming from the asphalt plant, several waiting in front of the paver--resulting in material temperature dropping under the critical temperature point. A truck bumps into the paver--therefore the paver stops and produces an uneven surface. Rollers, compacting the newly laid asphalt road behind the paver, but not in the right temperature range, or performing too many passes on one spot yet not enough passes on other spots. Results include thermal segregation and uneven surfaces due to no control of the paved temperature. Sub-optimal results cause reworks, delays, cost-escalations and irregularities in the process chain. Any one of these worst-case scenarios could happen at a road construction site. That is why MOBA Mobile Automation AG--together with Fraunhofer IIS, DKE Aerospace, Dynapac, Teleconsult Austria and inPosition--explored and realized a solution to optimize the asphalt paving process.

Within the scope of the ASPHALT research project, the project partners developed a way of optimizing the process flows at the construction site using GNSS technology from the paving of the asphalt to compaction, and at the same time networking the machines with one another. In doing so, the scalable, high-precision and cost-effective system interlinks the satellite-based positioning, steering and control systems of the deployed machines. Initial field tests took place late 2011 on Germany's A111 highway outside of Berlin. ASPHALT impressed not only the machine operators but also construction companies and state, national and EU decision makers.

Trouble-free processes based on satellite positioning
The project results are groundbreaking. Because while GNSS technology is being applied with increasing frequency in the area of earthwork and for monitoring tasks, satellite-based position data has very seldom been used for asphalt work up until now.

ASPHALT utilizes this technology to position the machinery. Trucks, pavers and rollers deployed at the construction site were equipped with receivers specially developed for the project. Currently, these work with GPS signals and, once available, will work with Galileo. With the satellite positioning data, fleet management can be improved, and all machinery deployment can be better processed. The precision of the GPS data needed depends on the task. For truck management, accuracy in meters is sufficient; whilst for compaction, accuracy in decimeter range is necessary. For paving and also for the docking of the trucks to the pavers, centimeter accuracy is requisite. Therefore, the system works with RTK (Real Time Kinematik). This way, the position signal can be improved right down to centimeter precision in order to fulfill paving requirements.

Another challenge was getting a constant signal, even in areas where satellite reception is limited or not available. This has been solved by combining GNSS and inertial sensor technology. This way, even short distances--under bridges, for example--can be circumvented without satellite reception.

With the compiled data, the entire asphalting process can be optimized and the deployment of the machines reciprocally coordinated.

Networking of the machinery--for better road quality
Exploring the asphalt process chain and improving each sub-process by constant monitoring and control of parameters is significant for the quality and durability of the road. Therefore, interconnecting the machines and their control systems allows controlling the important parameters for material delivery, temperature, compaction and quality of working steps, and also helps to optimize the complete process.

The networking of the machinery is a very promising aspect for improving the quality in road construction, while at the same time saving time and money through quick completion of work at construction sites. In addition to the experience of the construction workers, the material properties and the quality of the pavement are also dependent upon the material provision. The process handling during the asphalting and the controlling of the paver and the shield play an important role as well. The application and compacting temperature, and the compaction itself, are further parameters that are decisive for the properties of the road. With ASPHALT, material movements plus the asphalt temperature are monitored from the application of the asphalt up to the paver. The system can be used to coordinate the transport of the asphalt to the construction site and make it easier for the driver to dock the truck to the paver. This is a very critical moment, as even the smallest bumping of the truck into the paver induces an irregularity of the paver’s movement, causing improper paving and therefore produces unevenness in the asphalt layer. To prevent this, distance sensors, which are mounted on the paver, scan the distance from truck to paver and allow a smooth docking without interruptions in the paving process.

Also the coordination of the trucks can also be managed with the GPS positioning. Too many asphalt trucks in front of the paver will result in lower temperatures, whereas a disruption of the supply chain will cause a stop of the paver, resulting in a bump in the road. By controlling the position of the trucks, their passages can be coordinated. This way, no disruption of the flow of material can occur and the asphalt is applied in the optimum temperature range as there is always new material available exactly when it is needed. Furthermore, with the MOBA-matic leveling system and the Sonic-Ski®, the layer thickness is regulated in such a way that a smooth, even road surface is provided for and unevenness is prevented. The contact-free Sonic-Ski® works with five ultrasonic sensors and scans the reference eleven times every second. By calculating the average elevation out of the three best measurements, small irregularities are taken out of the resulting measurement. The sensor can scan string lines but can also use the ground as reference, so that no string lines are necessary. With these measurement values, the paver’s screed can be triggered in a way that it produces an even surface in accordance to the target values.

During asphalting, the temperature of the applied material is monitored by MOBA PAVE-IR™, which is mounted on the backside of the paver. The system scans the surface over the whole paving width via infrared sensors and delivers a temperature profile. This allows detecting thermal segregation in real time and enables contractors to achieve a uniform high quality surface free of segregation.

PAVE-IR™ also offers substantiating documentation that the material is being applied at the correct temperature. The MOBA MCA-2000 roller system supports roller drivers when compacting by measuring the asphalt temperature via temperature sensors and monitoring the number of the repeated passes over the pavement. By aligning the actual number of overruns and the target number of passes, incorrect compaction is prevented.
Networking of the machines with their positional data ensures that the rollers compact the material at locations within the appropriate temperature range.

Potential savings combined with higher quality
Using ASPHALT research outcomes for future construction sites leads to a faster completing of job sites with better results and roads with a longer lifespans. With ASPHALT, time and money can be saved because time buffers are no longer necessary, unnecessary transport trips are avoided and no redundant material is delivered or used. The sub-processes are ideally synchronized and thus allow a smooth workflow during the whole construction time.

The paver terminal serves as gateway for the Internet. The data from all machine control systems is shown on the display of the paver which gives an overview over the whole project. An additional bonus: All data can be automatically recorded and documented. ASPHALT also offers huge potential for saving to communities, urban and rural areas. Thanks to the high quality of the roads, the ensuing maintenance costs reduce and repairs become more seldom or are only necessary at greater time intervals.

Of the 5.27 million kilometers of roadways in Europe, 90 percent are paved with asphalt. The repair costs for this surface is between 100.000 to 200.000 Euros per kilometer. Since an average service life of a road surface equals ten years, an annual requirement to repair about 500.000 kilometers per year exists. If the service life of roads is increased by just 10 percent from ten to eleven years, this means annual savings of 4.5 billion in Europe, as about 45.000 kilometers of asphalt roads less need to be repaired. This also means that fewer resources are consumed. Furthermore, the number of traffic jams on highways--15% of which are caused by construction sites in Germany, thus making them the second most frequent cause of traffic jams (after traffic overload)--is reduced. CO2 emissions, and hence environmental pollution, are reduced. Since unevenness of the road surface--which causes aquaplaning--is prevented, road traffic safety is also improved.

Jaroslaw Jurasz studied Electrical Engineering and obtained his Doctorate in that field at the University of Karlsruhe in 2003. Since 2009 Jaroslaw Jurasz is MOBA's Head of Development.

A 978Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

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