Design and validation of a multi-electrode embedded sensor to monitor resistivity profiles over depth in concrete

Implementation of an Embedded Sensor Based on Electrical Resistivity to Monitor Drying in Thick Concrete Structures

“…The PCB sensor has a ladder shape in order to improve the anchoring of the electrodes in the concrete. The number of electrodes in the PCB sensor used in this study was increased from 19 (Badr et al, 2019) to 28 electrodes, each having dimensions of 5x1.5 mm 2 staggered on either side of the circuit, to investigate the entire 30 cm thickness ( Figure 1). The spacing between the electrodes is 2 cm on each side, hence 1 cm taking into account both sides.…”

“…The differences observed in Figure 3 can be related to the variability of the concrete. Indeed, a measurement is essentially sensitive to a restricted volume of material between (and around) the two electrodes where the potential is measured (Badr et al, 2019). This volume is less than the representative elementary volume (REV) of an electrical measurement in concrete, the dimensions of the REV having to be at least three times the maximum size of aggregates (Du Plooy et al, 2013), in this case 3Dmax = 36 mm.…”

“…In addition, it is necessary to wet the surfaces of the electrodes to avoid high resistance contact. Hence, Badr et al (2019) developed an embedded sensor based on a printed circuit board (PCB), which presents various advantages such as: measuring profiles with a centimeter resolution through the whole thickness of a reinforced concrete structure, ensuring good and lasting electrical contact between the concrete and the electrodes, reducing invasiveness, allowing a high geometric accuracy together with a low fabrication cost and mitigating wiring problems. This new resistivity embedded sensor and the measurement chain were validated in various solutions and in small concrete specimens (Ø11x22 cm) but not in full scale concrete structures (Badr et al, 2019).…”

An Embedded-Sensor Approach for Concrete Resistivity Measurement in On-Site Corrosion Monitoring: Cell Constants Determination

“…Given the utility of broaching durability problems effectively and sufficiently in advance, however, by monitoring structures from the time they are built, alternative embedded methods for monitoring resistivity have been proposed. Examples include a multi-electrode system developed by Badr et al [ 13 ] to determine resistivity at different depths or the screen-printed sensor proposed by Sophocleous et al [ 14 ]. Inasmuch as resistivity is particularly helpful when analyzed in conjunction with other durability parameters, the idea of integrating resistivity measurements in embedded corrosion rate assessment systems has been gaining in popularity [ 15 , 16 ].…”

“…In addition, under certain circumstances, some resistivity sensors could reduce their reliability because the cell constants used are usually limited to very specific implementation conditions [ 8 ]. It is usually due to the use of a limited number of calibration solutions [ 13 ], as well as due to variations in the geometric features of the sensor during its implementation which have not been considered in the cell constant calibration [ 10 ]. Therefore, it is usually suggested to calibrate the cell constant in every sensor implementation to ensure reliability [ 10 , 20 ].…”