Concrete Imaging using GPR

Ground Radar can map rebar and locate voiding

Analysed ground radar 3D data showing rebar in concrete slab

Ground penetrating radar (GPR) is regularly applied to examine concrete structures such as walls, floors, columns and bridges. It has recently gained popularity for concrete imaging. GPR’s advantages over more traditional methods such as covermeter and Ferroscan are many:

• Greater depth penetration (up to 500mm at high resolution)
• Resolve second layer of rebar (subject to spacing)
• Determine slab thickness
• Detect air voids, conduits and pipes (including plastic), tensioning cables, etc.
• Screed does not have to be removed to map rebar in floor slabs
• Generally only one sided access required
• Capable of depth slice images and 3D models

Historically only X-ray technology created a photographic image of the concrete interior but it required access to both sides of the structure and involved the use of hazardous X-ray sources. The Ferroscan does offer imaging, but this is poor and limited in comparison.

Detailed imaging of reinforcement can be achieved by scanning at close centres on a regular orthogonal grid. The data is processed using specialist software and depth slices or a 3D model of the reinforcement can be produced.

Alternatively, if depth and rebar spacing is required, this information can be shown graphically or exported to a spreadsheet for statistical analysis including contour plotting.