GPRS’ precision concrete scanning services were integral to the rehabilitation of a 38-story residential skyscraper in Jacksonville, Florida.
A team of GPRS Project Managers worked to ensure the contractor renovating the tower could safely install the buck hoists they needed to transport workers and materials to different levels of the building. Additionally, they scanned numerous locations throughout the building to ensure safe anchoring into its post-tensioned concrete slabs, and to locate and map rebar on the building’s pool deck that was failing and required extensive repairs.
GPRS Area Manager Will Sizemore said that while the tower is only 20-25 years old, owners of buildings like this in Florida have in recent years gone to greater lengths to ensure the structural integrity of their properties. This is due to the 2022 passing of “The Surfside Bill,” which requires engineers and architects to certify the structural integrity of every high-rise condominium building in the state by providing “Milestone Inspections” that must be completed by December of 2024, and updated every 10 years after that.
If these inspections are not completed by the end of 2024, or if necessary concrete repairs found by inspections are not completed and certified in a timely manner, the owners of these towers risk incurring fines and even jail time.
“It’s made a lot of condo owners very anxious and wanting to verify that everything is done properly,” Sizemore explained.
GPRS was not the first professional concrete scanning company hired to work on this tower in Jacksonville. Sizemore explained that firm originally hired backed out of the job.
“[The other firm] found out that it was all post tension slab, and they didn’t want the liability from [the contractor] drilling into it. So, then [the client] called us.”
Working with post-tensioned concrete does come with risks. Severing a single post tension cable with a saw or drill can lead to as much as $30,000 in repair costs – not to mention structural failure that endangers everyone on site.
Ground penetrating radar (GPR) is the most effective tool for locating subsurface elements like post tension cables and rebar within concrete. A GPR scanner transmits non-destructive radio waves into the surface or soil, which then interact with encountered objects, producing a readout of hyperbolas that vary in size and shape based on the detected materials.
GPRS Project Managers are specially trained to interpret these readouts to tell you where objects are located within a slab or underground and provide an estimated depth for these buried obstructions.
GPRS is so confident in the accuracy of our concrete scanning services that we introduced the Green Box Guarantee. When we place a green box within a concrete layout prior to you anchoring or coring into that slab, we guarantee the area within that box will be clear of obstructions.
If we’re wrong, we agree to pay the material cost of any damage that occurs.
From skyscrapers to sewer lines, GPRS Intelligently Visualizes The Built World® to keep your projects on time, on budget, and safe.
What can we help you visualize?
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Frequently Asked Questions
What types of concrete scanning does GPRS provide?
GPRS provides two specific but different scanning services: elevated concrete slab scanning and concrete slab-on-grade locating. Elevated concrete slab scanning involves detecting embedded electrical conduits, rebar, post-tension cables, and more before core drilling a hole through the slab. Performing a concrete slab-on-grade locating service typically involves scanning a trench line for conduits before conducting saw cutting and trenching to install a sanitary pipe, water line, or something similar.
How is GPR used to identify post-tension tendons vs. rebar in a post-tensioned slab?
In post-tensioned structures, we typically find one mat of support rebar near the base of the slab. This mat is generally consistently spaced and remains at a constant elevation. Post-tension cables are generally found above this support mat and “draped” throughout the rest of the structure. The elevation of the cable is usually high near the beams and column lines and drapes lower through the span between beams and column lines. Knowledge of these structural differences allows us to accurately differentiate between components. Our Project Managers will leave you feeling confident in our findings and in your ability to drill or cut without issue.
Can GPR determine the difference between rebar and electrical conduit?
Ground penetrating radar 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.
