Embedded Disposable Sensor that can Measure the Curing of Cement

An Elizabethtown College professor has developed an embedded sensor that functions in cement much like a thermometer in the Thanksgiving turkey.

“The thermometer indicates if the turkey is done by measuring its internal temperature,” said Nathaniel Hager III, an adjunct faculty member in Elizabethtown’s physics and engineering department. “The embedded sensor does the same thing in concrete by monitoring how quickly water involved in the curing process is chemically combining with portland cement.”

Hager’s research, conducted with business partner and chemist Roman C. Domszy, involves embedding a disposable sensor in a concrete structure when the cement is poured. “A fast electrical pulse is bounced off the sensor, producing a reflected pulse that contains molecular signals due to unreacted water and water combining with portland cement,” Hager said. “Tracking these two signals along with cure time provides a better understanding of the cure process and identifies irregularities that lead to improper cure. Essentially, we’re looking for the signals that correspond with cement strength. If we don’t get them, we have to trust the signals to tell us that something is wrong.”

There are a number of applications in the construction industry for the system, which Hager and Domszy refer to as Time-Domain-Reflectometry (TDR) Concrete Cure Monitoring. The system could be used by companies that make cement and cement additives to determine how to optimize the curing process. It could also be used in the field to help test structures – “to see if cement is fully hard” -- or on multilevel structures, to determine when to pour the second layer. And it could help identify residual moisture in cement floors before surface coatings, like epoxy, are installed, minimizing moisture damage and reducing wait times.

“When the thermometer indicates that the turkey is getting done too quickly or too slowly, you take corrective action like turning the oven temperature up or back,” Hager said. “This monitoring system allows those in construction to do the same thing with concrete.”

An article on Hager and Domszy’s research, which was funded in part by National Science Foundation’s Small Business Innovation Research (SBIR) program, appeared in a recent issue of the Journal of Applied Physics. A patent for their concrete cure monitoring system should be issued in a few months.

Posted November 23^rd, 2004