concrete GPR method interpretation

Concrete and GPR: Basic Method and Interpretation

In part one of this two-part blog series, we went over some basics on what’s known as ground penetrating radar, or GPR. This form of non-destructive testing has seen major improvements due to technological upgrades over the last 15 years or so, and is now one of the most common testing formats used to determine the quality and characteristics of the concrete, soil and other materials below the surface of your slab.

At Lift-Up Concrete Lifting, LLC, we’re happy to offer a wide range of residential and commercial concrete lifting and leveling, plus robust testing services to determine the need for our concrete repair solutions. When you’re worried there’s significant damage taking place below the surface of your concrete slab, the type you can’t pick up with the naked eye, GPR is often one of the tests used to help know for sure. Today’s part two of our series will go over how GPR works, how data is interpreted, and how this form of technology has improved significantly over recent years.

How GPR Actually Works

As we noted in part one, GPR is an imaging technique that uses electromagnetic waves. But how exactly does this take place?

When you’re looking to investigate a given concrete surface, the GPR setup will be brought and an electromagnetic pulse will be sent into the structure. As this pulse passes from one material type to another, the velocity of its waves changes – the energy reflected back to the receiver is able to note this, and also provides a record of the interference. Basically, by noting when waves return at a different velocity than they were sent out at, this method helps map out areas of the concrete, or even the soil below it, where material damage or other changes are taking place.

Interpreting Radar Data

Now, it takes a bit of expertise to interpret the radar data here. This data comes initially in analog form, or a series of lines that require some experience to understand.

Generally, the most important items in this data are metallic inclusions like reinforcement bars, dowels, pipes and pre-stressing tendons. However, data response will vary from material to material, so an inexperienced user could misinterpret this data if they aren’t careful. This is why both experience and equipment knowledge are required here.

Improvements in Quality

As we noted in part one, GPR has been around for decades – but has seen major improvements over the last 15 years or so, to the point where it’s much more viable than it used to be as a concrete testing method. Radar data is digitally recorded, for instance, rather than being burnt onto thermal paper using belts, making it much more accurate; in addition, three-dimensional maps are now possible where they were not in previous generations.

For more on ground penetrating radar in concrete testing and repair, or to learn about any of our concrete lifting and leveling services, speak to the staff at Lift-Up Concrete Lifting, LLC today.