GPR Concrete Scanning

GPR can map reinforcing bars, welded wire, post-tensioning patterns, metallic and some non-metallic conduits, slab thickness changes, and selected void or delamination responses. Detection depends on depth, size, moisture, congestion, orientation, and access. Harrowgate reports likely target type and limitations rather than presenting every radar reflection as positively identified.

Useful depth depends on antenna frequency, concrete moisture and conductivity, reinforcing congestion, target size, and access. High-frequency antennas resolve typical slab reinforcement well but do not see indefinitely. We select equipment for member thickness, calibrate where possible, and state the reliable scan zone. Deeper or masked areas need supplementary methods.

Sometimes pattern, spacing, continuity, depth, drawings, and nearby boxes support a reasonable interpretation, but radar alone does not label material. Rebar usually forms regular mats, while conduits follow service routes. Harrowgate combines orthogonal scans, electromagnetic locating, records, and isolation. High-consequence targets may require both-face scanning or controlled exposure.

No. GPR is one part of a post-tension risk process. Tendon drawings, stressing-end locations, member geometry, scans in both directions, engineer-defined exclusion zones, and sometimes other verification are required. Tendons are not drilled, cut, or exposed because a single scan line appears clear. The structural engineer approves the final opening location.

A linear target produces its clearest crossing response when the antenna travels across it. A pass parallel to the target can be weak or misleading. Orthogonal grids reveal both reinforcement directions, improve continuity tracking, and help distinguish intersections. Tight grids are used around proposed holes so the safe layout is based on complete coverage.

No. A clear result applies only to the scanned area and reliable depth and is limited by congestion, material, access, and equipment. Small plastic conduits, deep services, or targets below dense steel can be missed. Harrowgate combines scan results with drawings, isolation, depth stops, observation, and stop-work rules for unexpected resistance.

The record identifies the scanned grid and permanent references, proposed work, accessible face, equipment, target markings, estimated depths, photographs, limitations, and unresolved conflicts. It links field marks to the approved penetration or anchor template. If the layout or depth changes, the affected area is rescanned rather than relying on an old general survey.