Concrete Scanning using GPR

At Penhall Technologies, a division of Penhall Company, we have specialized in concrete scanning for more than 20 years. We employ expertly trained analysts that use state-of-the-art GPR (Ground Penetrating Radar) equipment to find common embedded objects and other subsurface hazards that are hidden in the concrete.

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GPR Concrete scanning used to detect voids in columns When our analysts arrive on site, you will find you have gained a trusted partner who is professional and prepared. We can help you locate rebar, pipes, post and pre-stress tension cables, conduits and many other subsurface hazards. Often, the data we collect is used to analyze and measure the appropriate remedial solutions for concrete structural deficiencies and building remodels. Our skilled GPR analysts can also detect voids within or underneath concrete slabs. Penhall’s concrete scanning service is generally your first step before concrete cutting, concrete coring, or grinding. Our service can be pivotal in your construction projects when it comes to cost reduction and damage prevention. Scan before you cut- so that you won’t have to encounter financial loss.

At Penhall, we pride ourselves in providing quality service in a timely manner. Our company believes in a “zero incident” culture where safety is our number 1 priority. As a result, for many years, big contractors, engineers, and government agencies have come to trust Penhall first for safe and precise scanning services. In addition to GPR concrete scanning services we offer private utility locating and x-ray imaging.


  • Reduce your safety risk. Keep everyone on the job safe.
  • Reduce your financial exposure. (e.g. Accidentally Cutting a post tension cable can cost you thousands.)
  • Save time. Know exactly where to cut or drill to avoid a hazard and delays.

Scan Concrete and Detect Rebar with GPR – How it works:

In the GPR scanning process, radio waves are directed into the concrete using a transmitting antenna at a certain frequency.  Since radio waves are a form of electromagnetic energy, this energy bounces off of buried objects such as rebar, post tension cables, pipes and conduits and are then captured by a receiver in the same antenna.

GPR scanning equipment contains software that can quickly and accurately interpret the radio waves. The key to this interpretation is two-fold; first, the strength of the signal reflection, or the amplitude, and second the two-way travel time of the radar pulse. It’s important to note that the two-way travel time is how the scanning equipment will determine how deep the objects are embedded in the concrete. Any object that reflects the signal is displayed real-time on the screen as the GPR equipment moves along. In some cases, it can even be determined if the object is metallic or nonmetallic.

Since the equipment uses electromagnetic pulses, the depth of the scan is determined by the electrical conductivity of the material being scanned. Material with higher conductivity will allow the radar to penetrate deeper. Conversely, material with lower conductivity will limit the depth the radar can penetrate. The amount of water found in the reflective material primarily determines how conductive the material will be. The greater the depth of the scan the less accurate it becomes. Because of this, GPR is often conducted using high-frequency waves that may only penetrate several feet into the concrete but offer a much higher resolution and a clearer image of what’s inside.

Since GPR spreads out as it travels into the ground as opposed to a straight beam, the antenna can detect the buried object even if it is not directly above it. The reflected radio waves create an image where the buried objects show up in the form of peaks and hyperbolae. The shape of the hyperbola, whether narrow or broad, depends on the electromagnetic velocity and size of the subsurface material. If the signal does not hit a reflective object, it will gradually dissipate as it passes through the material.

Concrete Scanning – Benefits and Limitations

  1. Locating conduit using ground penetrating radarGPR provides a real-time image that displays detected objects
  2. GPR provides the depth of the objects within a few centimeters
  3. GPR can detect objects made of metal, plastic, and various other materials

While most GPR related research is focused on environmental and engineering applications, GPR can also be used in concrete scanning, utility locating urban planning, archaeological site characterization, military, security, etc. Whatever the application, GPR makes it possible to avoid subsurface hazards before drilling, cutting, digging, or where extra caution is necessary. According to World many construction outfits are coming around to the notion that concrete scanning services are vital for job safety.

Although recent advances in GPR hardware and software have improved the technology, some limitations still exist.

  • High-conductivity materials, such as clay soils and soils that are salt contaminated, reduce the depth of GPR ground penetration
  • Signal scattering in heterogeneous conditions (e.g. rocky soils) limit performance
  • Interpretation of GPR radargrams (the radar image of mineral deposits or a geophysical surface) is not intuitive
  • Considerable expertise is necessary to effectively design, conduct, and interpret GPR data

Concrete Scanning Tools

As part of our procedure, Penhall analysts uses the GSSI 2000 MHz Palm Antenna to inspect concrete in tightly spaced areas that were previously inaccessible such as corners, against walls and around obstructions. Like the bigger 1600 MHz version, the Palm Antenna enables Penhall to locate subsurface hazards.

The Basics of Concrete Scanning Equipment

The GSSI SIR® 3000 is the industry’s number one choice for data accuracy and versatility in ground penetrating radar scanning. The Subsurface Interface Radar (SIR) System enables Penhall to save clients time, money and even lives. In the video below, we’ll outline the specialized equipment that Penhall uses, including the high-resolution, all-purpose 1600 MHz antenna, to locate embedded rebar, post tension cables and conduits in concrete structures.

1. Portable GPR Scanning System

The StructureScan™ Mini HR, manufactured by GSSI, is an all-in-one high-resolution GPR system for concrete services. Along with our other equipment, Penhall uses the Mini to scan concrete to locate rebar, conduits,  post-tension cables, and other obstructions.

2. What is the difference between GPR and X-ray?

It’s important to understand some key differences between GPR and X-ray before determining which to use on your next project. Both provide data on what subsurface objects may exist in the concrete. The decision about which option is best for the situation depends on a variety of factors, including the project parameters (e.g. objective, location, etc.) and how definitive the image needs to be.

Key Differences

Ground Penetrating Radar X-ray
Radiation Exposure No Yes
Interpretation of Scan Subjective Definitive
Required Access to Scan One side of a surface Both sides of a surface
Scan Time Short Long (approx. 5-6 hours)
Occur during business hours Yes No
Real Time Inspection Yes No
Large Area Scans Continuous no limit Multiple exposures
Standard Scan Size 24 x 24 16 x 16
Slab on Grade Yes No
Electromagnetic Interference Yes No

Determining the Cost of Your Concrete Scanning Project

Pricing for ground penetrating radar (GPR) services is unique for each project. The ultimate cost is dependent on a number of factors such as:

  • Job location
  • Number and/or size of areas to be scanned
  • Depth of objects to be identified
  • Type of equipment needed to capture the image
  • Amount and/or complexity of the hazards believed to be in the concrete

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Identifying cables in post tension concrete slabs

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We Scan For

  • Pipes and Conduits
  • Post-Tension Cables
  • Utilities and Live Wires
  • Rebar and rebar patterns
  • Voids within the Concrete
  • Structural Integrity of the Concrete