Field testing of concrete slabs at O'Hare
On October 29, 2007, a new section of taxiway was poured at O'Hare, and our UIUC research team installed sensors into the pavement to measure temperature, relative humidity, lift-off of slab corners, and joint-opening displacements.
Sensores and Data Collection Systems
Powered by the solar panels, the sensors and data collection system are designed to be self-sustaining in off-grid or remote areas.
The temperature and relative humidity sensors were assembled as sensor trees, installed prior to the pouring of concrete, to provide the environmental response profiles inside the pavement.
Internal lift-off sensors, also installed before pouring, were placed next to the dowels to monitor the vertical displacement or curling deformation at the corners. 
Joint-opening sensors were installed after saw-cutting to capture the opening initiation and displacement afterwards.
External lift-off sensors were attached in place near the potential opening posterior to after the removal of the side forms. The purpose of these measurements is to analyze the deformation of the slab under early age volume changes and environmental changes.
It is well known that concrete undergoes shrinkage, and that differential temperature and drying gradients can cause slabs to curl. Internal stress in the concrete is induced when slab corners lift-off the ground, making the slabs susceptible to cracking under applied loads. The measurements will be analyzed to tell us how the slabs behavior compares to predictions made by computer models. Confidence in the design will be enhanced by improving our understanding of slab behavior and the accuracy of predictive models.