Because there are multiple factors that affect the measurement results of the rebar scanner cover thickness, the following conditions must be met in order to accurately measure the reinforcement protective layer thickness:
1. The concrete surface is smooth and flat, and the concrete does not contain additives or magnetic components
2. The rebar is not corroded.
3. The rebar is parallel to the concrete surface.
4. Avoid rebar welding and binding points.
5. The reinforcement shall be perpendicular to the scanning direction, with an allowable deviation of ±5°.
6. The diameters and protective layer thicknesses of adjacent steel bars are similar.
7. The roller of the instrument must be in contact with the object being measured.
8. The surface of the instrument’s roller needs to be clean and free of sand and gravel particles.
9. As shown in Figures 1.1 and 1.2, the ratio of reinforcement spacing L to protective layer thickness S usually needs to meet the requirement of not being less than under the condition of 2:1, the ratio should increase accordingly as the diameter of the rebar increases, such as when the diameter is greater than 18mm，and it is not greater than 25mm, the condition of 2.5:1 must be met; when it is greater than 25mm, the condition of 3:1 must be met.
10. As shown in Figure 1.1, the surrounding stirrups should be located at a distance of more than 75mm from the center of the probe measurement.
To ensure the reliability of the measurement results for rebar diameter, the following measurement conditions must also be met:
1. The thickness of the protective layer should not exceed 60mm.
2. The probe position should be kept constant during the measurement process.
Rebar Detectors for the Installation of Reinforcement Bars | Langry
