Why Calcium Chloride Testing Is No Longer the Gold Standard

calcium chloride test

Calcium chloride tests used to be the standard. But advancements have made it obsolete.

The calcium chloride test, developed in the 1950s, tests moisture in concrete through the moisture vapor emission rate (MVER). It follows the ASTM F1869 standard and sat on the throne of commercial concrete moisture testing for over 40 years.

It was basically the only way people tested concrete in North America.

Even today, some people still think calcium chloride is the way to go in commercial settings. However, the reign of calcium chloride may be over. How come? We’ll find out by looking at:

First, let’s look at how calcium chloride became a common test in commercial settings.

Why Was Calcium Chloride So Popular?

Calcium chloride was one of the only tests available for at least 40 years. People came to trust it, and no newer methods arose to prove it inaccurate.

Here are some other factors that added to its popularity:

The quick and easy appeal—or not?

The calcium chloride test is not complicated, and much of the work is passive. This is why many think it is quick and easy.

However, it takes a lot of effort to prepare and quite a bit of time in total.

To prepare the area you want to test, you grind the concrete with a grinder. Then, place a dish of calcium chloride (previously weighed) on the clean section and seal it under a plastic dome. Let it sit for 60–72 hours (3 days) and then weigh the dish again. To do this, some people send it to a lab with very precise scales. Others have precise scales to weigh the calcium chloride and then calculate the results. This weight difference is used to calculate the MVER.

That’s a lot of time spent on a test, and in the meantime, you have to hold up construction waiting for it.

Besides all this waiting and effort, there is the expense of the test.

Cost-effectiveness: bang for the buck?

Calcium chloride testing is also relatively inexpensive at the start. If you place 13 tests across a slab of 10,000 square feet, that’s only going to cost (in materials) about $147.95.

That’s only $11.38 a test! That seems hard to beat when you’re potentially saving hundreds or thousands of dollars on a future ruined floor.

However, while calcium chloride may seem cheaper at the start, it doesn’t save labor, time, or even as much flooring damage as you might think. Modern methods of concrete moisture testing have shown just how much the calcium chloride test lacks.

The Rise of Modern Methods of Concrete Moisture Testing

Modern ways of measuring concrete moisture emerged in the 1990s in Sweden. Researchers at the Technical University of Lund did extensive testing and eventually developed what was called the NordTest, the basis for relative humidity (RH) testing.

Let’s take a closer look at the RH test.

More about RH testing

Unlike the calcium chloride test, RH testing analyzes the moisture content deep in the concrete, which is a more accurate picture

Unlike calcium chloride, which only measures the surface of the concrete slab, RH testing takes a deep dive into the concrete to look at what’s underneath.

An RH test is inserted in the concrete 40% down if it’s drying from a single side, and 20% down if it’s drying from both sides (which is rare).

Inserting a test nearly halfway into the concrete gives a better picture of the entire slab’s moisture condition. That 40% depth best correlates with the final condition of the entire slab once the covering has been placed over the top and the moisture has equalized throughout.

The surface of the concrete generally dries first. So even though the surface seems dry from various surface tests, the concrete deep down probably isn’t. Moisture may continue to seep up to the surface from the depths of the concrete for a while.

By giving you a fuller picture of the concrete’s actual moisture condition, RH tests can help you prevent moisture problems in flooring before they happen. You won’t get a false reading that indicates your concrete is dry when it really isn’t.

And unlike calcium chloride tests, RH tests can be calibrated, ensuring an accurate reading.

Not to mention, RH tests can be done in a third of the time of a calcium chloride test. A calcium chloride test requires 60–72 hours to collect results, while an RH test needs just 24 hours. And with our Rapid RH, only one hour is usually needed before you have a close-enough result (generally within 3–5% of the final reading) to make a business decision. While you’re waiting for the equilibration time to finish, you can start to schedule the installation crew or consider more drying time.

The digital world has changed the uses of the RH test even more. More on that next.

Tech-driven moisture testing

Technology has enabled RH testing to become even more useful. With apps to save and display readings, and devices that log data, RH testing is more reliable and easy.

You can use apps to automate the readings, plus download them to see reports of the moisture in the slab over time.

Our DataMaster app, for example, connects via Bluetooth to our Rapid RH Total Reader, which reads, records, and reports slab moisture data. You can add pictures and notes to the reports and print them from your smartphone.

You can even monitor ambient temperature and humidity with technology like our Smart Logger and the accompanying app. This little tool keeps track of the room 24/7, saving time and money.

All these devices are user-friendly and give you additional information for testing concrete moisture and ensuring everything stays within the required testing parameters.

So, with the advances in RH testing, what has happened to calcium chloride testing?

Where Calcium Chloride Lost Its Charm

With the fast-advancing technology of RH testing, the calcium chloride test simply can’t compare anymore. Let’s look at a few areas in which it’s lacking.

Surface level insights: just the tip of the iceberg?

If moisture levels in concrete were an iceberg, the calcium chloride test would report on the part you see above the water.

Of course, everyone knows that’s only the tip. The majority of the iceberg lies hidden beneath the water.

And so it is with moisture in a concrete slab. Usually, only a small portion of the moisture in the slab will be at the surface at any given time. This is what you see, and it’s what the calcium chloride test sees.

The RH test takes the entire iceberg into account—all the moisture in the concrete. And this matters for the durability of the floor above the concrete. Even if the surface doesn’t seem to have any moisture, what’s beneath the surface will come back to bite you. It’ll damage the durability of floor covers laid atop the concrete.

So, in short, the calcium chloride test detects moisture on the surface of the slab. But even though it can do this, it isn’t always accurate. More on that next.

Questionable accuracy and the cost of mistakes

The calcium chloride test can only measure the surface moisture of a slab. But even that measurement may not be accurate since ambient conditions in the room can skew the results.

Suppose your calcium chloride test results say the moisture levels are acceptable. Satisfied, you lay down hardwood flooring.

But the test was inaccurate because it was measuring conditions on the surface, when the moisture problem was deeper in the concrete. What you didn’t know was that the moisture levels were still much too high to move forward. Eventually, the floor covering is ruined. And you receive a call from the builders or homeowners wanting to know why.

Now, you have to waste time and money returning to the site to re-evaluate the situation, fix the problem, and potentially reimburse the homeowner for the ruined floors.

RH testing solves the problem of lost time, materials, and money by presenting a more accurate picture of what’s happening beneath the surface of the concrete.

Let’s look at what the experts are saying about this switch from calcium chloride to RH testing.

Industry Voices and Expert Opinions

hardwood flooring moisture problems

Moisture can easily wreck a beautiful hardwood floor if the subfloor hasn’t been properly tested

While some floor installers still use calcium chloride as their test of choice, much of the industry has shifted away from it to more accurate testing methods, such as the RH test.

What professionals are saying

The one thing many professionals have in common when citing their reasons for switching from calcium chloride to RH testing is accuracy. They want the results to be accurate to prevent problems and mistakes.

J. D. Grafton, former owner of CC Solutions, has worked with concrete for years, and he has seen first-hand how calcium chloride tests come up short. He observed that slabs certified dry by those tests tended to have flooring failures.

When the RH tests became available, he quickly switched to them. The reason?

He said, “[T]he accuracy is certified and it doesn’t need to acclimate past its initial point. We could stick it in there, read it and trust it. We went that [way] and we stuck with it.”

RH testing delivered accurate readings and prevented flooring failures when calcium chloride tests could not. Read more of his story.

Here’s what others say about the RH test:

“The Rapid RH is very accurate and because the sensor is already in the bottom of the hole and is already equilibrated to the hole, when you insert it to take the reading, all you’re doing is taking the reading and not disturbing it. I can walk away, come back, and I can have the customer with me and we can read it in a matter of minutes” – John Lowther, JKL Construction

“My job is to provide professional, thorough, accurate, impartial testing services. My obligation is to use what works – and Wagner [Rapid] RH® flat out works. And I trust them to work every time” – J. K. Nixon, Concrete Restoration Services, LLC

“The Rapid RH® is inexpensive, quick and easy to use, and enables us to do calibration checks required for ASTM F2170 compliance in seconds rather than hours. And because it gives us quick, accurate results, we can address a potential problem quickly. Or, if there’s no problem, we can get back to the install without further delay. This saves us time, money, and effort” – David Harris, President and CEO, Riverbed Concrete, LLC

Professionals have adopted RH testing. Here’s how industry standards have moved with it.

Industry standards and recommendations

The ASTM F2170 is the standard used for concrete testing. After RH testing was found to be more accurate than calcium chloride, the ASTM F2170 standard was born to accommodate these findings. This was in 2002.

Since then, testing has continued to influence the ASTM standard, as new and better methods have been introduced. In 2010, ASTM halted the use of calcium chloride testing on lightweight concrete due to unreliable test results.

Testing on the F2170 method continued with ASTM’s Precision and Bias (P&B) study, completed in 2014. This led to ASTM’s most recent amendment: An RH test requires only 24 hours, rather than 72 hours, for equilibration.

These studies have brought RH testing to the forefront of concrete moisture testing as the most reliable and accurate method.

Once the Standard, But Now There’s Better

Calcium chloride testing, while not perfect, had its place. It was one of the earliest attempts to assure floor covering installers that the concrete was dry. And it went many years without a contestant.

Calcium chloride was also the test that got people thinking about accuracy and reliability. Merely eye-balling a slab wasn’t good enough anymore.

With that focus on accuracy, the future must necessarily be in RH testing. RH is the new standard of accuracy, with greater precision than calcium chloride could ever dream of.

Our Rapid RH test is considered one of the best RH tests out there. Visit our store to make it part of your workflow.

Frequently Asked Questions

What is RH testing, and how does it differ from calcium chloride testing?

Relative humidity (RH) testing is a test that measures the relative humidity levels of a concrete slab. It involves placing small probes into holes in the concrete and allowing them to equilibrate for 24 hours before taking readings.

The calcium chloride test, on the other hand, involves placing a dish of calcium chloride on top of a concrete slab. It’s sealed by a plastic cover and left to absorb moisture. This moisture is then used to calculate the moisture level of the slab.

RH testing is a more dependable method because it measures deep within the slab rather than just on the surface.

Why is in-depth moisture testing crucial for concrete floors?

Without an in-depth moisture test, you risk ruined floors—as soon as a few months after installation. Much of the moisture in concrete resides below the surface and continues to rise and leave the concrete as it dries. If a floor covering is placed on top before the concrete dries, the moisture will be trapped under the floor. This could cause enormous damage.

With an in-depth test of the concrete, you can tell whether the concrete is actually dry enough to lay a floor covering on top.

What are the long-term cost implications of using outdated testing methods?

Using an outdated testing method, such as calcium chloride, can cause a chain of undesirable events. It can cause flooring failures, which can then result in lost time and money when you’re called back to fix the issues.

If this happens enough, your reputation could sag and then collapse, which results in a loss of business.

By moving to better testing methods, you save a lot of money, time, and hassle.

How can professionals transition to newer, more accurate testing methods?

The transition from old testing methods to new and accurate ones is easy, and you’ll never regret the change. To learn more about the Rapid RH test, contact our concrete moisture testing experts here at Wagner Meters by emailing info@wagnermeters.com or calling 855-391-1003.

Last updated on September 25th, 2024

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