Black Ice Detection in Permeable Asphalt Pavements
In 2004, the University of Texas' Center for Transportation Research was awarded Project 0-4834, a two-year research project funded by the Texas Department of Transportation to study the formation of black (clear) ice in open-graded asphalt pavements. Dallas Semiconductor's Thermochrons and Hygrochrons (part of the iButton product line) are being heavily used in this research, which began in September 2004. Open-graded, or permeable, asphalt offers substantial advantages over conventional asphalt pavements, primarily in the form of reduced spray, better visibility, and greatly decreased noise. However, these pavements tend to be the first to freeze and the last to thaw when used in cold climates.
Project 4834 is tasked with studying this problem. At multiple locations in north Texas, Thermochrons were placed at various pavement depths to detect and record the process of ice formation in the pavement structure. Additional Thermochrons and Hygrochrons record the corresponding ambient temperature and humidity conditions.
The first year of winter data has now been successfully collected with all Thermochrons and Hygrochrons still functioning, despite some of the Thermochrons being placed directly in the wheel path in high traffic locations. Researchers have been able to characterize the onset, depth, and duration of ice in the pavement structure of both the permeable sections and the control sections. Data collected using the iButtons on site has been matched to data collected by the National Climatic data center as shown below.
In the near future, this data will be used to alert TxDOT maintenance crews to incipient icing conditions via wireless transmission. For more information on the use of thermochrons in concrete, visit iButton.com.