Phase Site Investigations carried out a geophysical survey to map reinforcement within a concrete structure using high frequency ground penetrating radar (GPR) and a Ferroscan covermeter. The survey was required to assist in determining the load bearing capacity of the concrete.
Covermeters are able to estimate rebar diameters and also the depth / cover to the top layer of reinforcement but they can only locate the upper layer of reinforcement and their penetration is limited. GPR can also provide information on the depths to rebars, it can penetrate deeper than a covermeter and also locate multiple layers of reinforcement but it cannot determine rebar diameters. Combining both techniques allows significantly more information to be obtained on rebar size, depth and distribution than just using one technique.
The survey was able to accurately map the rebar layout within the structure and showed that the although there were two layers of reinforcement it was unevenly distributed, was missing in places and in others had either been put in on an angle or had slumped. Not the information that the engineers were expecting but now they could factor this into their calculations. Had they just utilised a few cores to try and obtain this information then the variability within the reinforcement may not have been realised and could have caused major issues with the proposed construction. The geophysical survey was carried out in less than a day and the results presented in a clear format within 3 days of the completion of the site work.