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Concrete coring involves drilling precise, circular holes into concrete structures.
It sounds simple, but coring is a technically demanding task. It requires careful planning, specialized equipment, and – most critically – accurate data showing you what's embedded within the concrete slab before you core.
How Is Concrete Coring Done?
The coring process begins with selecting the appropriate drill and bit size. Contractors prefer diamond core bits because they can cut through concrete, aggregate, and embedded steel with minimal vibration and dust. The drill is mounted on a rig, which may be handheld or anchored to the surface for stability.
Water is typically used during drilling to cool the bit and suppress dust. In sensitive environments, such as hospitals or data centers, dry coring can be used. Dry coring often employs vacuum systems to effectively handle debris.
The operator must maintain steady pressure and monitor their progress. They need to ensure they are not damaging the surrounding concrete slab, or any embedded utilities or structural components.
Once extracted, cores can be analyzed for compressive strength, density, or other properties.
Why Is Concrete Coring Necessary?
Concrete coring serves a wide range of functions across industries:
- Utility Installation: Electricians, plumbers, and HVAC technicians often run conduits, pipes, or ductwork through concrete walls or floors
- Structural Testing: Engineers extract cores to assess the quality and integrity of existing concrete, especially in aging infrastructure
- Retrofitting and Renovation: When buildings are modified or expanded, coring allows for the integration of new systems without compromising structural integrity
- Anchoring and Fastening: Holes may be drilled to install anchor bolts, dowels, or other structural reinforcements
Precision is paramount when concrete coring to ensure the success of your project. Misaligned or poorly executed cores can compromise the structure, damage embedded systems, or create safety hazards.
The Hidden Dangers Beneath the Surface
Concrete is rarely just concrete. Modern slabs often contain a complex network of embedded elements:
- Reinforcing Steel (Rebar): Provides tensile strength and structural integrity
- Post Tension Cables: Used in high-performance slabs to reduce cracking and increase load capacity
- Electrical Conduits: Carry power and data throughout buildings
- Plumbing Lines: Transport water, gas, or waste
- Fiber Optic Cables: Critical for communication infrastructure
Drilling into any of these elements can have serious consequences. Severing a post tension cable can release stored energy with explosive force. This endangers workers and can compromise the structure. Damaging electrical conduits can cause outages, fires, or electrocution. Hitting a water line can flood the site and halt work for days.
These are not hypothetical risks. These things happen regularly on job sites across the world. The cost of such mistakes can be staggering, both in terms of safety and project delays.
Why You Need to Know What’s Below
Before you core, you need to know what's within and below the concrete slab you're planning to penetrate.
Ground penetrating radar (GPR) is a non-destructive imaging technology used for locating and mapping objects embedded within concrete slabs. A GPR scanner emits radio waves into the slab, then detects the interactions between those waves and any embedded objects such as rebar, post tension cable, or conduit. These interactions show up in a GPR readout as hyperbolas. Their size and shape vary based on the material detected.
Unlike X-ray scanning, GPR does not require access to both sides of the slab and poses no radiation risk. It’s fast, accurate, and ideal for identifying:
- Rebar patterns and depth
- Post-tension cables
- Conduits and pipes
- The likely location of voids or honeycombing
- Embedded anomalies
When properly interpreted by a qualified concrete scanning professional, the resulting data reveals safe coring areas. You’ll be able to avoid any critical embedded infrastructure and ensure compliance with safety standards.
Let GPRS Keep You Safe When You Need to Core
Concrete coring isn't just drilling holes. It's a precise and risky task that requires skill and planning.
Concrete slabs have hidden complexities, so every coring job comes with risks. If you don't hire a professional concrete scanning company to give you accurate data of what's within the slab before you core, you're risking serious safety hazards and financial setbacks.
GPRS provides precision concrete scanning services that help keep your concrete coring projects on time, on budget, and safe. Utilizing GPR scanning, electromagnetic (EM) locating, and other complementary technologies, we Visualize The Built World® to help you plan, manage, and build better. Our SIM-certified concrete scanning Project Managers have achieved and maintained a 99.8%+ rate of accuracy, meaning we’re providing you with industry-leading services to ensure you can get your work done while avoiding mistakes and delays.
Concrete Thickness
GPRS Project Managers provide GPR scanning services to determine key slab information for structural engineers, including concrete cover and overlay thickness, concrete thickness, and even dowel placement. Unlike other concrete scanning companies, GPRS is not limited by the size or scope of your site; we have the training and the equipment to fully evaluate your concrete structure.
Slab On Grade
Ground penetrating radar’s ability to visualize what’s inside and under concrete slab-on-grade is one of its biggest advantages over X-Ray scanning technology. Because GPR only needs access to one side of a concrete slab or structure to scan the material for anomalies such as embedded conduit, it can evaluate slab-on-grade.
Shallow Utility Locating
It’s not just the utilities within your concrete slab that you need to worry about – if it’s a slab-on-grade, you also need to avoid lines buried in the soil below. GPRS Project Managers utilize both GPR and EM locating to provide you with a 99.8%+ accurate picture of the infrastructure within and below your concrete slab.
Conduit Mapping
We know you can’t risk severing an electrical conduit while coring or cutting through concrete. We mark our GPR findings directly on your slab so you know where all subsurface obstructions are buried and where you can safely cut or core.
Rebar Locating
Damaged rebar will cost you tens of thousands of dollars to repair. And that’s not counting any structural damage or injuries that occur because of the damaged support. GPRS Project Managers are specially trained to use GPR to locate and map the rebar within your slab or concrete structure.
Post Tension Cable Mapping
Our concrete scanning GPR service can locate post tension cables prior to core drilling. Our concrete scanning results are directly marked on the slab's surface. We can also create 2D CAD drawings and a 3D BIM model. These will show the layout of the post-tension cables inside your slab.
The GPRS Green Box Guarantee
When GPRS places a Green Box within a layout on a concrete slab before you cut or core the concrete, we guarantee that area will be free of obstruction.
If we’re wrong, we agree to pay the cost of any damage that occurs.
Green Box Guarantee information is presented directly on the surface of the coring location. This ensures clear communication of where you can and can’t safely core. GPRS Project Managers perform post-job walkthroughs to explain all Green Box Guarantee locations and parameters.
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Post Tension Slab 3D BIM Modeling
See inside your post-tensioned concrete slabs - including conduit, draping, rebar, and more - with comprehensive 3D BIM models that help you avoid damages and plan, upgrade, and renovate better.
Case Study: GPRS Provides Accurate PT Cable Layout for 49-story Building
Task:
GPRS partnered with Turner Construction to locate and mark the full post tension cable system layout for floors 12-23 of a 49-story building, with approximately 12,500 sq. ft. of concrete on each floor. After completing concrete scanning using GPR, each floor was 3D laser scanned. We used this data to produce 2D CAD drawings and a 3D BIM model for virtual design and construction. The architect received a permanent record of the post tension cable layout to complete fit and finish design plans for the 12 floors of the building.
Problem:
The AEC team required precise interior PT slab mapping for design, planning, and construction of their mixed-use building. Every PT cable bears up to 30,000 Ibs. of load and costs $20,000-$30,000 to replace.
Solution:
GPRS Project Managers employed GPR to accurately scan the interior of each slab. The team then 3D laser scanned the surface markings so that our in-house Mapping & Modeling Team could build accurate 2D CAD drawings and a 3D BIM model of the interior of each slab, including individual and bundled cable drape.
What can we help you visualize?
Frequently Asked Questions
Can GPRS scan vertical surfaces or ceilings?
Yes, GPR can scan for the location of rebar in concrete columns and walls. It can also scan the underside of a floor to mark out the reinforced steel and any embedded conduits.
How is GPR used to identify 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.
How long does it take to scan an area for core drilling?
GPR is an extremely efficient and rapid technology. Large areas can be easily and quickly scanned with the state-of-the-art GPR units utilized by GPRS Project Managers. Our standard layout for a typical core drilling location is 2’x2’. It usually takes about 10 minutes to scan and mark an area this size.
Can GPR scan concrete slab-on-grade?
Yes, it can. Unlike with X-ray, where both sides of a concrete slab must be accessible to obtain a picture of the subsurface structure, GPR only requires access to one side of a slab to obtain a comprehensive view of what’s inside the slab. This makes it an ideal technology for evaluating concrete slab-on-grade.
