Electric Cable in Concrete
Conquest survey in an warehouse.
Overview
When cutting or coring concrete, embedded electrical cabling poses a challenge. This example from a client shows the power of powerline detection combined with GPR imaging to define active power cables.
Problem
Locating live electric cables embedded in concrete is a concern for both operational safety and building rennovation. Confirming the as-built construction at the design stage allows planners to optimize placement of new infrastructure. If concrete structures have to be cut or cored for facility upgrade, damage to live power cabling creates an operator safety hazard and disrupts critical building functions. Avoiding such surprises is the goal!!
GPR Contribution to Solution
A contractor in Mississauga, Canada used Conquest GPR to image concrete for many years. Embedded conduits were normally identified by the meandering response pattern which did not align with normal reinforcing structure. On this occasion, he found an anomalously strong response from a reinforcing member but no indication of the expected conduit.
Sensors & Software had just introduced the next generation of Conquest GPR with the integrated PCD (power cable detection) sensor and the new system was tested on this site.
Collecting a standard Conquest data grid resulted in the images below. The GPR depth slice showed a strong response at position 2.25 which fit into the regular reinforcing pattern visible in the depth slice. The PCD detector image showed that a strong powerline response was aligned with this strong GPR response suggesting that the rebar and a power cable were co-located.
Conquest GPR depth slice showing an unusually strong response from a reinforcing element aligned along numeric position 2.25.
Conquest - PCD image showing live current.
Subsequent coring and chipping confirmed that an electric cable was located close to a rebar. The enhanced Conquest GPR response was the combined response of the rebar and the electrical cable.
Results & Benefits
This case study demonstrates the power of Conquest with PCD; combining the two sensor observations provides more definitive indication of embedded live power cables. Some key observations are:
- Conquest imaging quickly defines reinforcing structure
- Users can be effective with only a few hours of training
- Experienced users can identify unusual responses but explanations may be ambiguous
- Adding the PCD sensor provides a simple, reliable indicator reducing uncertainty
GPR responses vary greatly depending on the target being sought and the host material. GPR response variability can be challenging to new GPR users. When learning about GPR, the best practice is to review several similar case studies to develop an understanding of variability. Check for other insightful information on the resources tab to learn more. Use Contact Us or Ask-the-Expert to reach our Application Specialists who can help you tap into Sensors & Software's vast array of technical information.