Non-Destructive Testing / FILE 05
GPR Concrete Scanning
Ground-penetrating radar reveals what is hidden inside concrete without cutting or coring. We map reinforcement, locate post-tensioning tendons, find conduits, and detect voids with millimetre precision.
EVIDENCE / GPR-CONCRETEGround-penetrating radar (GPR) is a non-destructive scanning technique that uses high-frequency electromagnetic pulses to image the internal structure of concrete. GPR detects interfaces between materials with different dielectric properties, including steel reinforcement, post-tensioning tendons, electrical conduits, voids, and delamination planes.
We deploy both 2D line-scan and 3D area-scan GPR systems. High-frequency antennae (1600 to 2600 MHz) provide fine resolution for reinforcement mapping in the upper 300mm of concrete. Lower-frequency antennae (400 to 900 MHz) penetrate deeper for slab thickness measurement, void detection, and post-tensioning tendon location.
GPR scanning produces real-time results on-site. Our engineers interpret GPR data in the field, enabling immediate decision-making for pre-coring clearance, as-built documentation, and condition assessment. Detailed post-processing provides calibrated reinforcement maps, cover depth measurements, and annotated cross-sections.
The technique is non-destructive, non-invasive, and requires no radiation licensing. GPR can be performed on occupied buildings without disruption, on single-sided access, and on horizontal, vertical, and overhead surfaces.
Capabilities
What we deliver
10 deliverables across the gpr scanning engagement.
- 01Reinforcement location, spacing, and cover depth mapping
- 02Post-tensioning tendon and duct detection
- 03Electrical conduit and embedded service location
- 04Void, honeycombing, and delamination detection
- 05Slab and wall thickness measurement (single-sided)
- 06Pre-coring and pre-cutting safety clearance
- 07As-built reinforcement documentation
- 08Moisture ingress path identification
- 092D line-scan and 3D area-scan capability
- 10Same-day field interpretation and reporting
Process
Our methodology
01
Survey Planning
Review of available drawings and investigation objectives. Selection of antenna frequency, scan grid density, and survey areas based on the structural questions to be answered.
02
Field Scanning
On-site GPR scanning with real-time data display. Engineers interpret results in the field to identify areas requiring additional investigation or immediate attention.
03
Data Processing
Post-processing of GPR data to produce calibrated reinforcement maps, cover depth contours, annotated B-scan profiles, and 3D depth slices where 3D scanning was deployed.
04
Reporting
Technical report with annotated GPR results, reinforcement layout plans, cover depth data, and findings relevant to the investigation objectives.
Use cases
Common applications
- Structural investigation of existing buildings
- Pre-demolition reinforcement mapping
- Post-tension tendon location before penetrations
- Service location before coring or cutting
- As-built documentation where drawings are missing
- Bridge deck condition assessment
- Facade panel investigation
- Heritage building non-invasive investigation
Frequently asked questions
5 questions answered.
Q01
What can GPR detect inside concrete?
GPR detects any interface where material properties change. This includes steel reinforcement bars, post-tensioning tendons and ducts, electrical conduits, PVC pipes, voids, honeycombing, delamination planes, moisture zones, and boundaries between concrete pours. The detection depends on contrast in dielectric properties between the target and surrounding concrete. Metallic objects produce the strongest reflections.
Q02
How deep can GPR scan into concrete?
Penetration depth depends on antenna frequency and concrete conditions. High-frequency antennae (1600 to 2600 MHz) typically penetrate 200 to 400mm with fine resolution suitable for reinforcement mapping. Lower-frequency antennae (400 to 900 MHz) can penetrate 600mm or more, suitable for slab thickness measurement and deep target detection. Wet or chloride-contaminated concrete reduces penetration depth.
Q03
Is GPR safe to use in occupied buildings?
Yes. GPR emits low-power electromagnetic pulses at power levels well below those of a mobile phone. No radiation licensing, exclusion zones, or personal protective equipment are required for GPR operators or building occupants. Scanning is quiet and non-disruptive. It can be performed during normal business hours without affecting building operations.
Q04
How accurate is GPR for reinforcement cover depth?
GPR provides cover depth accuracy of plus or minus 5 to 10mm under typical conditions when properly calibrated against known targets or core measurements. For more precise cover depth measurement (plus or minus 1mm), we use electromagnetic cover meters (Ferroscan) in combination with GPR. The two technologies are complementary: GPR provides the broader structural picture, while Ferroscan provides the precise cover data.
Q05
Can GPR replace destructive testing?
GPR reduces the need for destructive testing by providing a non-invasive structural picture that guides where cores, samples, or openings are needed. It does not replace laboratory testing for material properties such as compressive strength, chloride content, or carbonation depth. GPR is a screening and mapping tool; destructive testing provides the material data. Used together, they minimise the number of cores required while maximising investigation coverage.
Related
Related services
- 01Concrete Coring & Laboratory TestingNATA-accredited material testing for compressive strength, carbonation, and chloride analysis.
- 02Corrosion InvestigationHalf-cell potential mapping, resistivity testing, and reinforcement condition assessment.
- 03Ultrasonic Pulse Velocity TestingIn-situ concrete quality assessment using ultrasonic wave velocity measurement.
- 04Building Condition AssessmentFull building surveys, dilapidation reports, and capital works planning.