Structural concrete assessment

Supporting repair decisions

Define the question before selecting the survey. Targeted measurements can help compare drawings with existing conditions or identify locations for further testing.

Non-destructive observations help document a structure while limiting exploratory openings. Their usefulness depends on the investigation scope and measurement conditions.

• Purchase or refinancing

  Document the condition of a concrete slab or structure as part of a commercial or industrial property assessment.

• Older structure without drawings

  Recover part of the missing information on reinforcement and estimated thickness to guide the investigation.

• Parking garage, balcony or terrace

  Target areas for further examination when concrete shows signs of deterioration.

• Change of use

  Check reinforcement layout before adding equipment loads, a mezzanine or racking.

• After an incident

  Document a structure following a fire, water damage or impact, in support of the engineer’s evaluation.

• New slab

  Compare estimated thickness, cover and spacing with the drawings, within the limits of the method.

What GPR can document

Measurements require interpretation.

Grid survey methodology

To document an area rather than a single point, antenna passes are usually organized as a grid in two perpendicular directions. Line spacing depends on the size of the targets and the level of detail the decision requires.

Profiles are then combined into plan views at different estimated depths. These views help follow reinforcement continuity, identify areas where the signal changes and choose locations for any targeted checks.

Tying the grid to building references, such as columns or joints, makes it possible to find areas on site and to compare a later survey if needed.

1. 01

   Layout

   Mark the grid on the selected area and tie it to fixed references on the structure.

2. 02

   Data collection

   Scan every grid line in one direction, then the other.

3. 03

   Processing

   Combine profiles into plan views at different estimated depths.

4. 04

   Interpretation

   Identify reinforcement, interfaces and signal variations, with their uncertainties.

Limits of GPR assessment

The signal attenuates more in wet or chloride-contaminated concrete, which can reduce readable depth. Closely spaced reinforcement layers often mask items below them.

A covering such as tile, a membrane or asphalt adds an interface to interpret. Depending on the material and its bond, readings may remain possible or become uncertain.

An area that sounds hollow can come from bearing giving way under the slab or from concrete separating within its thickness. What each defect covers is developed on the voids beneath slabs and concrete delamination page.

• Does not measure concrete compressive strength
• Does not directly measure carbonation or corrosion activity
• Cannot always identify the exact nature of an anomaly
• Does not replace samples requested by the engineer

Complementary methods

An engineer may specify acoustic, electrochemical or ultrasonic tests, or targeted samples. GPR does not answer every condition-assessment question.

Methods described in technical references are not automatically included in a ScanAxis assignment. Scope and availability must be specified in the quote.

Survey and report

Agree on objectives, critical zones, available drawings and access. The measurement grid should match the decision being considered.

Define the methodology, maps, observations, limitations, delivery format and schedule required before work begins.

What the assessment does not replace

Estimated thickness and rebar locations alone do not establish load-bearing capacity. A survey does not replace structural calculations or an engineer’s conclusions.

Provide results to the professionals responsible for any change in loading, strengthening or repair.

Frequently asked questions