5. Effect of Bar Diameter Setting
To carry out a covermeter survey, NDT personnel often have to input the bar diameter on
their covermeters on site without knowing the actual diameter of the reinforcing bar in the
concrete. This is especially the case when surveying older structures. Using a default setting
for the bar diameter such as 12mm or 16mm will not produce concrete cover readings as
accurately as indicated in the previous section. In order to measure concrete cover in the most
accurate manner, the bar diameter needs to be known and set accordingly in the covermeter.
However it is interesting to consider how large an affect an educated “guestimate” would
have on the accuracy of cover measurements.
In this study, covers for N24 bars were measured with the setting for the bar diameter to
16mm, 20mm and 24mm respectively. Figure 5a shows the comparison. Covers for N28 bars
were also measured by setting bar diameter to 24mm and 28mm respectively. Figure 5b
shows the comparison.