Structural and Concrete Scanning

By far the most popular form of concrete scanning, as the name would suggest, a ferroscan survey is used to detect and position rebar within reinforced concrete in much the same way as a covermeter survey. Unlike that more basic approach, however, the ferroscan can also determine both bar diameter and spacing, letting an experienced user build up a far more detailed picture of sub-surface conditions.

Determined to stay at the forefront of concrete scanning technology, all of our teams use the very latest ferroscan instruments, the all-new Hilti Ferroscan PS300. Site conditions allowing, this revolutionary new instrument is able to provide the following details down to approximately 200mm below the surface…

• Cover depth
• Bar diameter
• Bar spacing
• Mesh layout

That’s up to 100mm deeper than its predecessor, the otherwise Hilti Ferroscan PS250. A ferroscan survey can also detect other metallic objects (e.g. steel cables) but, as the name would suggest, is unable to detect non-metallic items.

Two types of survey can be carried out using the Hilti Ferroscan…

Quick Scans – The lateral position of any rebar can be marked directly onto the slab, column or beam itself using chalk, paint stick or similar. This seemingly rudimentary approach is perfect for those intending to drill or core through concrete. Not only is it quick, providing instant results, it also lets the client drill cleanly, missing any reinforcement on the way through.

Image Scans – For those requiring more in-depth information, image scans are the preferred route. Granted, this type of ferroscan survey takes longer to perform and the results cannot be analysed in situ. That said, once the surveyor has returned to base, the data can be downloaded to their computer for analysis within Hilti’s Profis software. At this point, cover depth, bar diameter and bar spacing measurements can be extracted. ‘Slices’ through scans as well as the overall mesh layout can also be output. These images can be added to reports or CAD drawings according to your specifications.

A somewhat different approach to the more traditional ferroscan, our Hilti PS1000 and Proceq GPR Live ground penetrating radar systems are developed specifically for the interrogation of structures. With a substantially greater operating depth, these tools are able to provide an incredibly detailed picture of sub-surface conditions.

By no means an exhaustive list, GPR concrete scanning can help identify the following…

• Voids
• Cracks
• Reinforcing bars (position, spacing and layout across one or a number of layers)
• Non-ferrous services (pipes, conduits, ductwork etc.)
• Changes in surface

Whilst it does have its limitations, concrete specific ground penetrating radar has helped revolutionise the field of concrete scanning, having a number of advantages over more traditional types of surveying.

GPR concrete surveys provide

• The ability to calculate the thickness of a slab
• The ability to view two layers of reinforcement without the need to access both sides of the slab
• Significantly improved operating depth
• The identification of voids, buried services and other buried elements, including non-metallic
• The ability to mark out reinforcement without the need to first remove any levelling compounds or screeds
• The ability to produce three dimensional and cross-sectional images of conditions inside the slab

A real step forward in the field of concrete scanning, ultrasonic testing has changed the way both we and the wider industry attempt to locate defects within concrete structures.

At Perry Testing, we’ve embraced the very latest in ultrasonic testing technology – the Proceq Pundit PE200 – in order to identify a whole range of structural defects in concrete. These include, but are not limited to…

• Cracks (including crack depth)
• Voids
• Pipes
• Honeycombing

Quite commonly, the ultrasonic testing of concrete may only be required from one side of the object, making access issues a thing of the past. What’s more, thanks to the nature of the device, we’re often able to provide critical data there and then, reducing down time and maintaining productivity on site. Naturally, however, these insights can be followed up by detailed drawings and reports highlighting any areas of concern.

Interestingly, the same technology can also be used to provide valuable information on the strength and uniformity of a whole variety of materials including…

• Concrete
• Wood
• Ceramics
• Rock and more.

A simple and cost-effective form of concrete scanning, a cover meter survey is intended to locate reinforcing bars (or ‘rebar’) within concrete as well as providing an accurate determination of cover depth – the distance from the surface of the slab to the top of the rebar.

Designed for exactly this purpose, a cover meter is a handheld instrument that uses pulse-induction technology to induce electromagnetic pulses into a concrete slab. The closer a reinforcing bar is to the surface, the stronger the magnetic field it will generate, thus making it possible for a covermeter survey to determine cover depth.

Until the advent of the Hilti Ferroscan, the cover meter was the only reliable method of determining cover depth. That said, if you don’t need to know bar diameter and spacing (features of the more advanced Ferroscan tool), a cover meter survey could still be the service your project requires. Indeed, lower equipment costs and reduced reporting time means that cover meter surveys can prove particularly cost effective.