While it's certainly important to monitor the condition of paved roads, keeping an eye on the surface will only tell you so much. You also need to know what's going on with the underlying asphalt, which is where an embedded layer of electronic fabric is designed to come in.
A paved road does not, of course, just consist of a uniform ribbon of blacktop.
There are typically multiple layers, some of which include a bottom subgrade layer of compacted earth, a subbase layer of granular material, a covered base layer of hard asphalt, and an exposed surface layer of smoother water-resistant asphalt.
In order to check on the condition of the hidden base layer, roads have to be closed and core samples have to be taken. Not only is this inconvenient, time-consuming, labor-intensive and destructive, it also only indicates the condition of the asphalt in that exact location. The fabric is intended to address these shortcomings.
Developed by scientists from Germany's Fraunhofer Institute for Wood Research and the SenAD2 project, the material consists of flax fibers interwoven with an electrically conductive sensor wire less than 1 mm thick. The fabric is produced on a double rapier loom in a width of 50 cm (19.7 in) at whatever length is needed.
Side-by-side connected lengths of the material are laid down across the base layer of a road, as it's being constructed. The surface layer is then poured over top, covering them. At the side of the road, however, an external measurement unit is connected to the sensor wire, which protrudes out from the blacktop.
As cracks proceed to form in the asphalt over the months and years that follow, the material expands, placing pressure upon the sensor wire. This creates a change in the electrical resistance of the wire, which is detected by the measurement unit. AI algorithms running on that unit are thus able to determine the current extent of the damage, and to provide an estimate of its likely progression over time.
"Our goal is to be able to plan over a longer period of time, to continuously monitor changes in the condition of the road and, on that basis, to establish forecasts and incorporate them into maintenance management activities," says Christina Haxter, a research scientist at Fraunhofer. "This won’t make the roads last longer, but it will improve efforts to monitor their condition."
The technology is currently being tested on an industrial road in Germany.
Source: Fraunhofer
