Describe the purpose and limitation of half-cell potential testing when evaluating rebar corrosion?

The purpose of half-cell potential testing when evaluating rebar corrosion is to identify areas within a concrete structure where there is a higher probability of active corrosion of the reinforcing steel. This test measures the electrical potential difference between a reference electrode (typically a copper-copper sulfate electrode, CSE) placed on the concrete surface and the reinforcing steel. More negative potential readings indicate a higher likelihood of corrosion activity. The limitations of half-cell potential testing are that it only provides an indication of the *probabilityof corrosion, not the *rateor *extentof corrosion. It can be influenced by factors such as moisture content, temperature, and the presence of chlorides in the concrete, which can affect the readings. It also only assesses the corrosion state at the surface of the rebar and may not accurately reflect conditions at greater depths within the concrete. Therefore, half-cell potential testing is best used as a screening tool to identify areas for further investigation using other techniques, such as core sampling or corrosion rate measurements.