GPR Concrete Scanning Services

What GPR concrete scanning indicates

• Reinforcement and mesh. Position, spacing and depth in each direction, and a second layer where it resolves beneath the first. Position is usually good to within about 10 mm in ordinary conditions; the report states the tolerance that applied.
• Post-tensioned tendons and ducts. Indicated where the signal reaches them, and separated from the reinforcement with a dual-polarisation antenna. See post-tension cable detection.
• Conduits and embedded services. Electrical, data and heating runs within slabs and walls.
• Slab and wall thickness. From one face, where the far face returns a signal.
• Cover to reinforcement. Across an area, feeding cover, carbonation and half-cell condition surveys.
• Voids and delamination. Loss of contact beneath overlaid slabs and behind linings, where the signal supports it.
• RAAC. Plank by plank identification from the density and reinforcement signature of the material. See RAAC surveys and how to identify RAAC.

When you need it

• Before drilling, coring or cutting. On post-tensioned structures it is the only sensible first step; on any reinforced element it is cheaper than a struck bar or a severed conduit. See scanning before drilling or coring.
• Structural assessment. When the reinforcement layout, spacing or depth is unknown or undocumented and the engineer has to calculate. See rebar scanning.
• Refurbishment and fit-out. Before fixing through floors, walls and soffits, and before opening up for new services.
• RAAC. Schools, hospitals and public buildings of the 1950s to 1990s, identified plank by plank.
• Voids and settlement. Where a slab sounds hollow, has dropped, or sits over fill of unknown condition.

Standards and method

Scanning follows the principles of BS EN 12504 for testing concrete in structures and CIRIA C748 for safe intrusive investigation, and pre-drill and pre-core work follows the UK Concrete Scanning Standard, under which NDTScan holds the Level 4 Operator certification. The antenna is chosen for the element: high frequency for close reinforcement in a slab, lower frequency for thick walls and foundations. Instruments are calibrated by UKAS-accredited laboratories where the work requires it, and every report names the equipment, antenna and settings used.

Equipment

GSSI SIR 4000, StructureScan and FlexNX with the NXT antenna range; Proceq GP8800 and GP8100; Mala GPR for deeper work; and the Hilti PS Ferroscan for cover and diameter estimation close to the surface. All of it is described on the equipment page, and the radar systems in detail under GSSI, Proceq and Mala.

What the report includes

• Scaled plans of every scanned area with the indicated targets drawn in each direction.
• Depth tables for each identified feature, with the tolerance that applied.
• Photographs of the areas and of any marking out on the surface.
• Equipment, antenna, settings and the standard applied.
• The confidence attached to each finding, and what the scan could not resolve and why.

Marking out on site is done where required. The interpreted report follows within an agreed number of working days.

What GPR cannot do

Radar does not measure bar diameter, does not pass through steel decking, foil-backed boards or metal plates, and loses resolution in wet, dense or heavily reinforced concrete. Tendons bundled together or masked by closer steel may not resolve. Where a decision depends on something the radar could not confirm, the report says so and recommends the small break-out or core that settles it.

Coverage

Oxford based, with short-notice attendance across the Thames Valley, London and the Home Counties usually within one to two working days and same day where the diary allows, and anywhere in the UK by arrangement: Oxfordshire, Berkshire, Buckinghamshire, London, Reading, Milton Keynes, Bristol, Birmingham, Cambridge and the rest of the locations.