Home · Methods
METHOD 05 · STRUCTURES

Structural inspection with ground-penetrating radar and ultrasonic tomography

Two complementary techniques to see inside concrete: GPR for reinforcement, ultrasound for cracks and internal defects.

THE METHOD

How it works

High-frequency GPR sweeps the surface of the structure and produces a 3D image: position and depth of the reinforcement and prestressing tendons, slab thickness, voids and likely corrosion zones.

Ultrasonic tomography sends sound waves into the concrete using dry-contact sensors and reconstructs a 3D image of the interior. It finds what GPR sees poorly: internal cracks, delaminations (separation between layers) and honeycombing.

The two images cross-check and complement each other. The structure is neither drilled nor damaged.

For hard-to-reach areas (tall piers, vertical walls, areas above water), the sensors can be carried by a climbing robot, which avoids scaffolding and access platforms.

WHAT IT IS FOR

The problems the method solves

  • Locate reinforcement before coring or sawing, so it is not cut.
  • Measure the thickness and cover depth of concrete elements.
  • Detect delaminations, voids and internal cracks in slabs, piers and beams.
  • Check the quality of a new structure before acceptance: industrial slab, platform, pier.
  • Inspect inaccessible parts of a structure (tall piers, vertical walls) without scaffolding, using the climbing robot.
  • Assess the condition of older structures before deciding on repair or strengthening.
WHAT YOU RECEIVE

The results we deliver

Reinforcement maps

Position and depth of the reinforcement, mapped over the whole scanned surface, with cover thickness.

Internal defects

Location of voids, delaminations and cracks, with their extent at the surface and in depth.

Report and 3D images

Interpretation report, sections and 3D views of the inside of the structure, to support the repair decision.

Reference practice: ACI 228.2R, EN 12504-4, ASTM C597.

HOW TO USE IT

What this changes for your decisions

  • Targeted repairs: treat the zones that need it and avoid unnecessary demolition.
  • Destructive tests limited to the points that matter.
  • Safer interventions (coring, drilling), thanks to locating the reinforcement beforehand.
  • A baseline condition of the structure, to track its ageing over time.
OUR EQUIPMENT

The equipment selected

PROCEQ (SCREENING EAGLE) · GPR FOR CONCRETE

GP8100

Six-antenna GPR array designed for fast concrete scanning.

At a glance

  • Stepped-frequency continuous-wave (SFCW) technology, 400 to 4,000 MHz
  • Six antennas: six parallel profiles in a single pass
  • Investigation depth up to about 80 cm

Why this choice

It scans a large area quickly and in 3D, with high resolution on reinforcement and prestressing tendons. It suits slabs, bridge decks and floors.

ACS SOLUTIONS · ULTRASONIC TOMOGRAPHY

MIRA 3D (A1040)

Ultrasonic device with 32 dry-contact sensors, producing a 3D image of the inside of the concrete.

At a glance

  • 32 dry-contact sensors (4 × 8)
  • Real-time 3D image reconstruction (3D-TFM)
  • Low frequency: good penetration in thick concrete

Why this choice

Where GPR is limited (very dense reinforcement, non-metallic defects such as cracks and delaminations), ultrasound takes over. Dry-contact sensors avoid the use of coupling gel, which speeds up measurements.

HAUSBOTS (UNITED KINGDOM) · OPTIONAL, DEPENDING ON THE PROJECT

HB3, inspection climbing robot

A robot that moves along vertical concrete surfaces and carries sensors where access is difficult: bridge piers, shear walls, façades, chimneys.

At a glance

  • Adhesion by suction and airflow: works on concrete and other non-metallic materials
  • Payload of about 25 kg: can carry inspection sensors, including an ultrasonic device of the MIRA type
  • Connected to a safety cable; already used to inspect bridge piers

Why this choice

Without a robot, inspecting a tall pier or a deck above water requires scaffolding, an access platform or rope-access technicians: it is slow, costly and risky. The robot brings the sensors to the surface and sweeps it evenly, without staff having to climb. We can bring it in with its manufacturer for structures that justify it.

Equipment selected for our first campaigns, being acquired, rented or provided through partnerships depending on the instrument; availability is confirmed when the order is placed. Characteristics as stated in the manufacturers' data sheets; they depend on configuration and terrain.

LIMITS

What the method does not do

  • GPR reaches its limits in very densely reinforced zones; ultrasound then completes the analysis.
  • Surface condition and moisture influence the measurement; the report takes this into account.
  • Both methods locate anomalies: precisely characterising a defect may require a confirmation test.

A corridor or structure to inspect? Let's talk about your need.

Write to us