Concrete Scanning Services

The concrete scanning services

• GPR concrete scanning. Ground penetrating radar for reinforcement, tendons, conduits, voids and slab thickness from one face. The first method on most jobs.
• Scanning before drilling or coring. The slab, wall or soffit scanned and the targets marked out where required before anyone cuts into it.
• Post-tension cable detection. Tendons and ducts in post-tensioned floors indicated before coring, with the limits of the method stated.
• Rebar scanning and reinforcement mapping. Bar position, spacing, layers and estimated cover across an area, for the engineer's calculation.
• Ferroscan surveys. Electromagnetic cover and diameter estimation close to the surface, where radar's estimate is not enough.
• Ultrasonic testing of concrete. Pulse velocity to BS EN 12504-4 and pulse echo for thickness, honeycombing and delamination.
• Concrete compressive strength assessment. Rebound hammer, pulse velocity and cores combined and reported to BS EN 13791.
• RAAC surveys. Plank by plank identification and condition assessment in line with IStructE guidance; see how to identify RAAC.
• Concrete x-ray. Why radiography is rarely practical on site, and what replaces it.

Condition surveys: cover, carbonation and corrosion

Where the question is how long an element has left rather than what is inside it, three measurements are taken together. A cover survey with the Hilti PS Ferroscan or a cover meter maps the depth of concrete over the reinforcement and flags where it falls below the minimum in BS 8110 or Eurocode 2. Carbonation depth is measured on cores or drillings with phenolphthalein indicator to BS 1881-210, and set against the cover to estimate the time to depassivation. Half-cell potential mapping to ASTM C876 and BS 1881-201 records the electrochemical potential of the reinforcement across the surface, and the pattern indicates where active corrosion is likely. Reported together, they give the engineer a basis for repair priorities and a maintenance plan rather than a guess.

How a concrete scanning project runs

1. The brief. What the element is, what you need to do to it or know about it, drawings if they exist, and access. From that the specialist proposes the methods and the scope, in writing, with a price.
2. On site. The right antenna or instrument for the element, a grid the survey can be repeated on, and marking out on the surface where it is required. Short-notice attendance is usually within one to two working days across the Thames Valley, London and the Home Counties, and same day where the diary allows.
3. Interpretation. The data is worked up in the office before a single conclusion is drawn. The specialist who scanned the structure is the one who interprets it and writes the report.
4. The report. Scaled plans of every scanned area with the indicated targets, depth tables, photographs, the equipment and settings used, the standard applied, and the confidence attached to each finding with what it must not be relied on for. It follows within an agreed number of working days.

What concrete scanning cannot tell you

Radar indicates reinforcement where the signal reaches it; bars masked by closer steel, or deep in dense concrete, may not resolve, and radar does not measure bar diameter. Pulse velocity gives an estimate of strength, not a tested value; cores give the tested value. No method sees through a steel plate, a foil-backed board or standing water. Every NDTScan report says which of these limits applied, because an engineer deciding whether to core through a slab needs to know what the scan could not see as much as what it could. See the UK Concrete Scanning Standard for how this is set out.

Who instructs NDTScan

Structural engineers who need the reinforcement or the strength of an element before they can calculate; main and fit-out contractors and drilling and coring specialists who need to know what is in a slab before they cut it; building owners, schools, trusts, councils and housing providers facing RAAC; and surveyors and insurers who need a condition record they can rely on. The sectors NDTScan works in and the equipment it carries are set out on their own pages.

Where

Oxford based, with the Thames Valley, London and the Home Counties covered at short notice: Oxfordshire, Berkshire, Buckinghamshire, and the cities on the locations page, including London, Bristol, Birmingham and Southampton. The rest of the UK and Europe by arrangement.