Ali Abu-Yosef

This paper describes a prototype passive sensor that can be powered and interrogated in a wireless manner to monitor the conditions inside structural concrete members. The term “passive” is used because the sensors do not include any on-board processing capabilities or sources of power (batteries). The sensors are designed to be embedded in the concrete during construction and interrogated sporadically over the life of the structure. The response of an embedded sensor is determined by measuring the impedance of an external reader coil that is magnetically coupled to the sensor. To date, the research has focused on detecting the initiation of corrosion within concrete structures. Accelerated corrosion tests were used to evaluate the reliability of the passive sensors. Sensors were embedded in reinforced concrete prisms and successfully detected the onset of corrosion in the reinforcement. Unlike the traditional measurements, such as half-cell potentials, the passive sensor readings did not fluctuate with changes in the temperature or moisture content of the concrete.

A corrosion detection sensor embedded within a concrete structure. The sensor includes a hermetically sealed resonant circuit that is a resistor-inductor-capacitor (RLC) circuit. The sensor further includes a sacrificial transducer that is inductively or capacitively coupled to the resonant circuit, where the sacrificial transducer is exposed to an environment outside the sensor to monitor corrosion of steel reinforcement in the concrete structure. Additionally, the sensor includes a protective cementitious housing surrounding the resonant circuit and the sacrificial transducer. The sensor further includes a diffusion layer placed over the sacrificial transducer, where the diffusion layer enables a dispersion of a chemical species over the sacrificial transducer. In this manner, a more uniform distribution of the chemical species over the surface of the sacrificial transducer mitigating the localized corrosion is ensured. Furthermore, such a design is less susceptible to false posit...

ABSTRACT A passive sensor platform has been developed at the University of Texas at Austin to monitor corrosion of embedded reinforcement in concrete structures. The sensors are powered and interrogated in a wireless manner. Initial sensor designs used a sacrificial corroding steel wire to indicate the risk of corrosion within concrete. The wire was physically connected to the sensor circuitry and passed through the circuit protection layer. Consequently, it allowed contaminants to reach the circuit electric components causing corrosion and limiting the service life of the sensor. A novel sensor configuration that relies on wireless inductive coupling between a resonant circuit and the transducer element is presented. The non-contact design eliminates the breach concern and enhances the durability of the senor. Preliminary test results of the new design will be discussed in this paper.

This paper describes the ongoing research efforts to develop a novel class of low-cost, unpowered, wireless sensors for detecting corrosion of reinforcement in concrete structures. The sensors are powered through magnetic coupling between an external reader coil and an embedded sensor. Measured AC impedance is used to interpret the state of the embedded sensor. The sensors are envisioned to be placed during construction and interrogated as part of routine inspections. The sensor prototype incorporates a sacrificial corroding element that is placed entirely outside the sensor components and interacts with the resonant circuit by inductive coupling and shielding of the magnetic fields. As the resistance of the sacrificial element increases due to corrosion, the measured frequency response changes gradually indicating corrosion initiation within concrete. In this paper the potential for detecting multiple levels of corrosion damage is demonstrated.