The goal of the half-cell potential field measurement is to measure the potentials at the concrete surfaces, in order to get a characteristic picture of the state of corrosion of the steel surface within the concrete.  These investigations can locate areas where corrosion is actively occurring but is not evident at the surface in order to identify problem areas and mitigate the issue before it is too late.  ACER’s full suite of half-cell potential measurement electrodes can be applied to very small areas such as columns and beams all the way up to entire bridge decks with a 4-wheeled survey cart.  Upon completion of the survey, the results are plotted on a Chipping Graph in accordance with ASTM C876 which assigns a 90% probability of corrosion ongoing to the areas more negative than -350 mV, and a 90% probability of no corrosion to the areas more positive than -200 mV.  Further refining and calibration of these thresholds can be achieved through an intrusive investigation to correlate the measured potentials to the physical state of the reinforcing steel.

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In addition to the half-cell potential testing, ground-penetrating radar (GPR) can be used to assess corrosion of concrete reinforcement rebar by detecting changes in the electromagnetic properties of the concrete caused by corrosion.  When reinforced concrete is corroded, the rebar can lose some of its cross-sectional area and strength, which can lead to structural problems. GPR can help detect corrosion by sending electromagnetic waves into the concrete and measuring the strength and timing of the reflected waves.  In particular, GPR can detect the presence of voids, cracks, and other defects in the concrete, which can be an indication of corrosion. GPR can also detect changes in the dielectric constant of the concrete, which can be used to estimate the presence of corrosion.