What GPR Concrete Scanning Can and Can't Detect
What GPR Concrete Scanning Detects (and Its Limits)
GPR concrete scanning shows you what is hidden inside a slab or wall before anyone drills or cuts it. It is a locating tool, and knowing what it finds well, and where it has limits, helps you decide when a scan is enough and when you need more.
How GPR sees inside concrete
Ground-penetrating radar sends radio waves into the concrete and records the reflections that bounce back. Whenever the waves meet something different from the surrounding concrete, such as a steel bar, a pipe or an air pocket, part of the signal reflects. The scanner draws those reflections as an image, and an operator reads the image on site.
At Alpha Core Drill we use the GSSI Mini XT, which scans to a depth of up to 60 centimeters. Nothing is cut or broken, and work nearby can usually continue.
What GPR detects well
- Rebar and reinforcement mesh. The spacing and rough depth of steel bars, so a core location can be chosen between them.
- Post-tension cables. Tensioned steel cables in slabs. Hitting one is among the most serious mistakes in concrete cutting, which is why locating them comes first.
- Electrical conduits and pipes. Both metal and plastic services embedded in the slab or wall, although plastic is harder to read than metal.
- Voids and anomalies. Air pockets, gaps and areas where the concrete differs from what surrounds it.
What affects the result
Several site conditions change how clear a scan is:
- Dense reinforcement. Closely spaced bars can mask objects beneath them.
- Moisture. Wet concrete absorbs more of the signal and reduces how deep the scan can see.
- Slab thickness and access. The element has to be reachable with a flat, clear surface to scan.
- Operator experience. Reading the image correctly takes practice. The equipment alone does not give the answer.
What GPR does not tell you
GPR locates objects. It does not measure concrete strength, and it is not a substitute for a structural engineer's assessment. It also cannot always tell you exactly what an object is, for example the difference between a duct and a pipe of a similar size. For that reason a scan is normally followed by clear marking on the surface, so the person drilling or cutting knows where the safe areas are.
When to book a scan
Book a scan before any core drilling, wall saw cutting or opening work in reinforced or post-tensioned concrete, and before fixing heavy anchors into a slab. It is quick compared with the cost of repairing a damaged cable or a cut conduit.
Alpha Core Drill provides GPR concrete scanning across Dubai, Abu Dhabi, Sharjah and Ajman, with more than 25 years of experience behind our team. To book a scan, call us or message us on WhatsApp. Related reading: our guide to rebar scanning before drilling and cutting.