Wireless Inspection System for Rebar Corrosion

Physical Sciences : Mechanical

Available for licensing

Inventors

  • Dean Neikirk, Ph.D. , Electrical and Computer Engineering
  • Sharon Wood, Ph.D. , Civil, Architectural and Environmental Engineering
  • Praveenkumar Pasupathy , Electrical and Computer Engineering
  • Ali Abu Yosef , Civil, Architectural and Environmental Engineering

Background/unmet need

The steel reinforcement in concrete structures is subject to corrosion, which can cause structural damage or failure. Monitoring this corrosion is difficult, since embedded steel is not visible to the naked eye. Furthermore, detection techniques are needed to indicate initiation of corrosion so that remedial action can be taken before the damage is irreversible.

Detection techniques such as acoustic, ultrasonic and radar have proven to be limited. Conventional corrosion monitoring techniques such as half-cell potential and linear polarization provide instantaneous measurements which are, however, highly subject to the conditions (moisture, temperature) during measurement. Sensors using a sacrificial corroding element provide the most direct measurement of corrosion. However, obtaining this data requires electrical access to the sensor. Any methods that require running wires breach the concrete and provide an ingress point for corrosion.

There is clearly a need for a wireless corrosion sensor. In addition, given the need for long-term monitoring of large structures, it needs to be battery-free, cost-effective, durable, and reliable.

Invention Description

Researchers at The University of Texas at Austin have developed a low-cost, battery-free, passive wireless sensor for monitoring the corrosion of steel reinforcement in concrete. The sensor is embedded in concrete and is interrogated using a magnetically coupled reader. The sensor has a resonator capable of wire-free interaction with a fully exposed sacrificial transducer which is in contact with the concrete environment that it is monitoring. A diffusion layer is included, which mitigates the effect of localized corrosion. This is a key innovation which ensures that the sensor will switch states predictably. Critically, this design is less susceptible to false positives, thus improving reliability.

Benefits/Advantages

  • Wire-free transduction protects circuitry and protects against premature failure.
  • Wireless and battery-free design avoids the breach of existing concrete by running wires and enables long-term non-destructive evaluation. 

Features

  • The design features a resonant, embeddable sensor which operates using magnetic coupling (wireless).
  • The design is battery-free, and does not include onboard electronics (passive).
  • The design includes a sacrificial transducer in direct contact with the concrete environment.
  • The transducer is capable of wire-free interaction with the hermetically sealed sensor circuitry.
  • The design includes a diffusion layer placed above the transducer to mitigate localized corrosion. 

Market potential/applications

Concrete bridge deck deterioration is one of the leading causes of structural deficiency in the U.S/ bridge inventory (NCHRP, 2004). Chase and Laman (1999) estimated that each year over one billion dollars is spent on bridge decks. Corrosion of the steel rebar is one of the leading causes of this deterioration.

Sources:
Chase, S., and Laman, J. (1999), "Dynamics and Field Testing of Bridges," TRB Millenium Paper, TRB A2C05 Committee on Dynamics and Field Testing of Bridges, December, 1999. http://onlinepubs.trb.org/Onlinepubs/millennium/00029.pdf ) NCHRP (2004).
"Concrete Bridge Deck Performance: A Synthesis of Highway Practice," Synthesis 333, National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C., http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_syn_333.pdf

Development Stage

Lab/bench prototype

IP Status