Step 01
Define the scan area
The member and grid are agreed and marked, with drawings reviewed beforehand where they exist so that findings can be compared against them.
Reinforcement Bar Scanning
Find the steel before you cut, drill or core, and check that the cover protecting it is what the drawing said it would be.
Reinforcement Bar Scanning: what it actually tells you
An electromagnetic cover meter induces a field in the concrete and detects the disturbance caused by steel. It locates bars, measures the depth of cover over them and, within limits, estimates the diameter. It is quick, cheap and accurate at shallow depths, which covers most cover survey work.
Ground penetrating radar goes further. It sends a short electromagnetic pulse into the concrete and times the reflections, which lets it see deeper, resolve two layers of reinforcement, and find things a cover meter cannot: voids, ducts, conduits and post tensioning tendons. On a congested slab, radar is often the only method that gives a usable picture.
Two jobs dominate the work. The first is safety: knowing exactly where the steel and the tendons are before anyone cores or drills, because cutting a post tensioning tendon is both dangerous and very expensive. The second is durability: cover depth is what protects reinforcement from chloride and carbonation, and in coastal Karachi a shortfall in cover is a direct shortfall in service life.
At a glance
- Cover meter rangeUp to about 100 mm to 180 mm depending on bar size
- GPR penetrationTypically 300 mm to 500 mm in concrete
- OutputMarked layout, cover statistics, scan images
- RateRoughly 100 to 200 square metres per day
How we run it
The sequence we follow on site and in the laboratory, and the point of each stage.
Step 02
Cover meter sweep
The surface is swept in two orthogonal directions to locate every bar, and bar positions are marked on the concrete as they are found.
Step 03
Measure cover
Cover is measured at each located bar, with the meter set for the estimated diameter, and a statistical spread reported rather than a single figure.
Step 04
Radar where needed
GPR is run where reinforcement is congested, cover is deep, a second layer is expected, or tendons and voids must be identified.
Step 05
Mark and report
Safe drilling and coring zones are marked directly on the structure, and results are reported against the specified cover and detailing.
What you receive
- Bar layout with positions marked on the structure
- Cover depth to each bar with the statistical spread
- Estimated bar diameter and spacing
- Location of second layer reinforcement, ducts and tendons
- Marked safe zones for coring and drilling
- Comparison against the specified cover and detailing
When this test is the right one
- Before coring, drilling or cutting into any structural member
- Cover depth acceptance on new construction
- Durability and condition assessment of an existing structure
- Verifying as built reinforcement against the drawings
- Locating post tensioning tendons before any penetration
Methods and standards
Every result is reported with its method reference and the calibration status of the instrument used.
BS 1881 Part 204 determination of strain, covermeter surveysASTM D6087 evaluating asphalt covered concrete bridge decks using GPRACI 228.2R non destructive test methods for evaluation of concrete in structuresBS EN 1992 1 1 cover requirements for durability
Common questions
What engineers most often ask us about reinforcement bar scanning.
Approximately, not exactly. A cover meter estimates diameter from signal strength, and diameter and cover trade off against each other in that signal. Where the diameter must be confirmed, we expose one bar at a representative location and measure it directly, then use that to calibrate the rest of the survey.
Cover meter for straightforward cover surveys on single layer reinforcement, which is most work. GPR where the steel is congested, deep, in two layers, or where you need to find tendons, ducts or voids. On many jobs we run the meter first and bring in radar for the difficult areas.
Not immediately, but it shortens service life. Cover is the barrier that keeps chloride and carbonation away from the steel, so a shortfall means corrosion will start earlier than designed. The response depends on exposure, and in a coastal environment it is taken far more seriously.
Often ordered alongside
Most investigations combine several of these. We scope them together so you are not paying to mobilise twice.
Concrete Testing
Concrete is specified by a strength it will not reach for 28 days, on a site where it is placed in minutes.
Read more
Schmidt Hammer Test
The fastest way to compare concrete across a structure.
Read more
Steel Testing
Reinforcement is bought by grade and specified by strength, but the grade is a claim until somebody tests the bar.
Read moreNeed reinforcement bar scanning on your project?
Send us the location, the structure and your programme. You get a scoped quotation with the standard, the number of tests and the turnaround written into it.