How GPRS Concrete Scanning Protects Historic Buildings

How GPRS Concrete Scanning Protects Historic Buildings

When a contractor needed to renovate a historic building in downtown Kansas City, Missouri, they called GPRS to provide precision concrete scanning services on an elevated slab in the structure.

Several core drillings were planned for the decades-old building. Striking any conduits or reinforcements within the slab while coring could have compromised the integrity of the structure.

Damaging a single post tension (PT) cable during concrete coring or cutting will set you back at least $20,000 to repair the damage, and there’s additional cost in the downtime necessary to complete the repair. Additionally, damaged PT cable can lead to structural failure that endangers your workers and anyone else in the vicinity.

A person uses a white marker to mark on a concrete slab.
GPRS provides precision concrete scanning services to keep your projects on time, on budget, and safe.

To ensure safe coring locations, GPRS Project Managers deploy handheld ground penetrating radar (GPR) concrete scanning antennas. These devices emit radio waves into a concrete slab, and those waves interact with – or “bounce off” – any material they encounter, including rebar, PT cable, and electrical conduit. These interactions are detected by the GPR unit and the results are displayed in a readout as a series of hyperbolas varying in size and shape depending on the type of obstruction that was located.

Professional concrete scanning technicians such as GPRS’ SIM-certified Project Managers can interpret these readouts to tell you what was located, so you can avoid these items during coring or drilling.

Prior to the application of GPR in construction, the only method available for non-destructive concrete testing was concrete X-ray. GPR has largely replaced X-ray, however, due to several advantages the former has over the latter:

  • X-ray is limited to investigating elevated slabs; it cannot scan slab-on-grade because it needs access to both sides of a slab to function properly.
  • GPR can scan slab-on-grade as it only requires access to one side of a slab to evaluate it.
  • X-ray technology is inherently dangerous as it requires the use of a radioactive isotope. Considerable set-up time is required, and you may need to shut down your entire job site while testing is conducted to mitigate the risk of irradiating personnel or the public.
  • GPR emits no harmful radiation and requires minimal-to-no setup time.
  • X-ray imaging isn’t only slower to conduct on-site than GPR – it’s also slower to yield results. Modern GPR scanners provide instant data for a professional technician to interpret. Data collected from an X-ray scan typically needs to be developed off-site before it can be interpreted.

GPR is the most effective tool for precision concrete scanning and imaging. And thanks to SIM, GPRS Project Managers (PM) are the most effective at tailoring the abilities of GPR to meet your needs.

Two men kneel on concrete while looking at a tablet.
All GPRS Project Managers are required to become SIM certified, which means completing a minimum of 320 hours of field training and 80 hours of classroom training.

SIM stands for Subsurface Investigation Methodology, the industry-leading specification and training program for private subsurface locating professionals. It guides how GPRS Project Managers conduct utility locates, concrete imaging, video (CCTV) pipe inspections, and leak detection.

All our PMs are required to become SIM certified, which means completing a minimum of 320 hours of field training and 80 hours of classroom training. During this training program, the PMs are challenged with real-world scenarios that prepare them for anything they may encounter in the field.

It’s because of GPRS’ commitment to SIM that our PMs have achieved and maintain a 99.8%+ rate of accuracy in the over 500,000 concrete scanning and utility locating projects we’ve completed to date. This includes scanning the elevated slab in the historic building in downtown Kansas City, where the PM determined the spacing and depth of the reinforcement with the slab and located a conduit running through the concrete.

This kept our client’s renovation on schedule by ensuring they were able to core the slab safely.

Our confidence in our PMs to do this for you, job after job, led GPRS to introduce the Green Box Guarantee.

It’s simple: when we place a Green Box within a layout prior to you anchoring or coring concrete, we guarantee that the area will be free of obstructions. If the area isn’t free of obstructions, GPRS will pay the material cost of the damage.

Whether you’re renovating a historic structure, or building new, GPRS Intelligently Visualizes The Build World® to keep your project on time, on budget, and safe.

What can we help you visualize? Click the links below to schedule a service or request a quote today!

Frequently Asked Questions

Why do I need concrete scanning?

When you’re excavating for a new structure or renovating an old building, there are countless subsurface hazards that need to be accounted for prior to excavation, core drilling or saw cutting.

Striking one of these hazards could decimate your budget, your schedule, and your reputation, and endanger your workers and anyone else in the vicinity.

Can GPR determine the difference between rebar and electrical conduit?

Ground penetrating radar (GPR) can accurately differentiate between rebar and electrical conduit in most cases. We have an extremely high success rate in identifying electrical lines in supported slabs or slabs-on-grade before saw cutting or core drilling.

Additionally, GPRS can use EM locators to determine the location of conduits in the concrete. If we can transmit a signal onto the metal conduit, we can locate it with pinpoint accuracy. We can also find the conduit passively if a live electrical current runs through it.

The combined use of GPR and EM locating allows us to provide one of the most comprehensive and accurate conduit locating services available.

Will there be a Green Box Guarantee placed on every concrete slab I have GPRS scan?

No. Our Green Boxes communicate to our clients that all critical targets such as rebar reinforcement, electrical conduits, and post tension cables are absent, and no obstruction is present. We place Green Boxes on elevated concrete slab locations that we’re confident are clear to core, cut, or drill through. If we aren’t confident that you won’t hit anything, we won’t place a Green Box on the slab.