Gravimetric Testing Explained—and Why Wagner’s C555 Concrete Moisture Meter Holds Up

Powdery white efflorescence on a concrete surface demonstrates the effects of excess moisture in concrete.

Excess moisture can cause issues like efflorescence, mold, and structural damage.

Here’s the simple definition of gravimetric concrete moisture testing. You weigh a sample of a concrete slab before and after oven-drying to calculate the total moisture percentage. It’s highly accurate. But it’s not very practical—unless you have a ton of time and your jobsite doubles as a laboratory.

That’s where a concrete moisture meter, like Wagner’s C555, comes in. It helps make moisture measurement practical on the jobsite.

And that’s a big deal! Concrete moisture testing is a must. If you skip it, you could end up with moisture-related issues like efflorescence, cracks, and ruined floor coverings. Not to mention voided warranties and costly callbacks.

A practical tool can make all the difference.

We’ll walk you through:

Overall, you want a clear understanding of how to protect your project and still keep schedules on track.

So let’s first get into the nitty-gritty of gravimetric moisture testing.

What Gravimetric Concrete Moisture Testing Is

Here’s the longer definition. Gravimetric testing is a concrete moisture testing method that involves taking a sample, weighing it, drying it, and weighing it again. By calculating the weight before and after drying, you’ll learn how much moisture the slab contains as a whole.

It’s considered to be an accurate method for determining how much moisture remains in the concrete. However, it’s more practical for the lab than the jobsite. But it does serve as a solid benchmark to measure all other concrete moisture meters against.

How It Works

Let’s break it down in six steps:

  1. Use a core drill to make a hole in the concrete to collect a core sample.
  2. Weigh the “wet” sample with a precision laboratory balance.
  3. Place it in a laboratory oven, high-quality drying oven, or kiln.
  4. Dry it until all moisture evaporates (i.e., when the weight stops changing).
  5. Weigh the sample again to get the dry weight.
  6. Use the difference to calculate the moisture percentage by weight.

Drawbacks of Gravimetric Testing

Despite its reputation for accuracy, gravimetric testing comes with some major drawbacks, including:

  • Time: Testing can take a significant amount of time and labor.
  • Equipment: It requires more specialized tools than other methods.
  • Sample size: Too small a sample makes weight changes less meaningful. But too large takes much longer to dry and is more destructive to the slab.
  • Sample quality: The sample must include both cement paste and some aggregate.
  • Handling: Samples need immediate protection and early weighing to avoid losing moisture too soon.

Like high school chemistry class, gravimetric testing gets complicated.

Thankfully, it’s rarely required by flooring manufacturers—and there are other, more practical ways to measure concrete moisture.

Wagner’s C555 Concrete Moisture Meter: Where Practicality Meets Efficiency

Someone uses Wagner’s C555 pinless moisture meter on concrete, a tool calibrated to gravimetric testing results.

Wagner’s pinless C555 moisture meter is twice as accurate as other leading meters, according to study.

Many flooring professionals on a time crunch keep a pinless concrete moisture meter on hand. They’re fast, non-destructive, and practical in the field.

High-quality moisture meters, like Wagner’s C555, are calibrated to the oven-dried samples of common concrete mixes. And they meet ASTM F2659 guidelines for preliminary evaluation of moisture in concrete, gypsum cement, and other floor slabs and screed.1

In other words, they help flooring professionals find moisture hotspots that need further monitoring during the concrete-drying process. And that includes determining where to place relative humidity (RH) tests for deeper and more thorough moisture testing.

Keep in mind, you should always check the moisture-testing requirements of flooring manufacturers before you make a final flooring decision (to protect the warranty). Concrete moisture meters are not always accepted to make final decisions about whether or not the concrete is dry enough to put down a floor covering.

So, which concrete moisture meter works best?

The C555 Concrete Moisture Meter: Twice as Accurate

If you’re planning to use a moisture meter to assess concrete, use Wagner’s C555. It’s pinless, so it doesn’t do any damage to the concrete. And when tested against industry-leading competitors, it consistently delivered readings that were closest to oven-dried results.

But not just by a hair. The C555 concrete moisture meter proved approximately twice as accurate as leading competitors in recent tests using multiple concrete mixes.

See It for Yourself

In the chart below, you’ll see how Wagner’s C555 concrete moisture meter readings compare with those of other leading manufacturers. All three meters were used to measure the moisture content (MC) in nine common concrete mix designs. And readings were compared using oven-dry test results (aka gravimetric testing) as the benchmark.

You can see that on average, the C555 had only half the errors compared to top competitors.

That means Wagner’s C555 readings came closest to gravimetric test results. Every single time.

A bar graph shows how MC readings of the C555 meter are twice as accurate when compared against two other meters, using gravimetric test results as the baseline.

This graph shows how Wagner’s C555 is twice as accurate (half the errors) as leading concrete moisture meters.

This study highlights the superior performance of the C555 moisture meter. It’s the concrete moisture meter flooring professionals can count on when working with any mix—from lightweight aggregates to those with various admixtures.

And that’s helpful for a flawless, long-lasting floor installation that keeps your profits and your reputation intact.

C555 Field Calibration Aids Accuracy

Someone places the C555 on its On-Demand Calibrator, demonstrating how this unique technology can prevent project delays.

Wagner’s C555 includes an On-Demand Calibrator—unique to concrete moisture meters.

Moisture testing with a meter simplifies real-world moisture testing. And the C555 is built to handle rugged environments.

But even the toughest moisture meter can benefit from a calibration check if it takes more of a beating than usual. (Hey, it’s not only keys and coffee cups that get left on truck roofs.)

Some moisture meters do on-site verifications. But even if they’re out of calibration, you have to pack it up and return it to the manufacturer for recalibration.

That’s another way Wagner’s C555 prevents some real headaches. It comes with a separate device for on-demand calibration so you can both check and recalibrate your moisture meter in a matter of minutes.

No construction delay. And no pressure to put your project at risk by skipping moisture tests.

Get Moisture Readings You Can Rely On

Gravimetric testing is considered an accurate way to measure concrete moisture. And calculations based on oven-dried concrete samples set a fantastic benchmark for other concrete moisture-testing tools. But its practicality is limited outside the lab. They require time and tools that don’t make sense for most flooring professionals.

Concrete moisture meters are far more practical on the jobsite than doing actual gravimetric testing. If you plan to use one, it’s best to go with the most accurate concrete moisture meter on the market—the C555 concrete moisture meter.

Wagner’s C555 is twice as accurate as the other industry-leading moisture meters, according to recent testing. That, along with its superior calibration technology, leaves you confident you are using the best meter for measuring concrete MC. The C555 can help you keep construction schedules on track. Plus, it’s fast and easy to use across multiple jobsites.

Here’s what Wagner customers say about the C555 concrete moisture meter:

“This is great. Measure the moisture in a concrete slab and it seems very reliable. I am very happy with this purchase and it’s a great value compared to other meters on the market.” — Drew, Verified Customer

“I am an inspector and use it to test the moisture content of concrete slabs mostly. I have used the Tramex meter in the past. This one is more affordable so I took a chance and am happy I did. I actually like the way it works better and the accuracy seems comparable. I would definitely recommend this meter.” — Coach K, Verified Customer

So go ahead! Explore Wagner’s concrete moisture meter for yourself.

 

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