Rampant Misinformation - RH Probes vs Tramex Concrete Meter

I just finished reading an "article" written by a RH promoter that was so full of misinformation and outright fabrications, I couldn't let it pass without comment.

To qualify the responses; there is a thinly veiled graphic used in this "article" directed towards Tramex since their meter uses a similar graphic, hence my specificity.

Fabrication #1: "Concrete moisture meters should never be used to make the final determination as to whether or not a concrete slab is dry enough for a flooring installation."

Fact 1: Tramex Concrete Meter was tested under field conditions where the researchers used a baseline of gravimetric, which is THE most accurate method of measuring moisture content. Tramex was the ONLY method in that study that indicated moisture content nearly identical to gravimetric. As a result, the Tramex Concrete Meter is the ONLY method currently available (and affordable) that can determine concrete dryness. Because of this qualification, I will not be referring to other devices that have not been qualified in this manner.

Fabrication #2: "No concrete moisture meter of any type can give consistently accurate ‘moisture’ readings across the different mixes and densities of concrete."

Fact 2: As stated earlier, Tramex was tested under field conditions, and was consistently mirroring the measurements of gravimetric, irrespective of where the field samples were extracted. It is interesting to note that the two RH Probes evaluated in the same study measured excessive moisture, even as the concrete aged and continued to dry. The RH probes were indicating the concrete was somewhere between dry and wet, with ranges unacceptably varied for any practical purpose.

Fabrication and Misinformation #1: "Additionally, even IF the so-called ‘concrete moisture meters’ were sufficiently accurate (again, they are not), they only measure ‘moisture’ (not relative humidity) in a very small area near the surface of the concrete slab. This type of surface ‘moisture’ testing tells us nothing about the conditions down in the slab. Once a floor covering is placed on a concrete slab, the relative humidity (RH) within the slab will equilibrate throughout the thickness of the slab."

Facts and Clarification #1: Once again, the unqualified statement of the "so-called concrete meter" not being accurate is inaccurate, with the justification an object lesson in misinformation. The "small area near the surface" is where floors actually fail and well confirmed in MANY studies, the concrete surface has a gradient and is typically more porous and more permeability in the top 25 mm (1 inch) of the surface, shown in the title graphic. Another bit of misinformation is the equalization of moisture. The referenced "proof" consistently used by the RH promoters is based SOLELY and COMPLETELY on the construction water/mix water used in the concrete itself. This same study cautions against using drying curves for concrete that has been rewetted. I have yet to see, read, or hear ANY information regarding concrete that has either been in service or has undergone environmental changes prior to a floor being installed...NOTHING!

NOTE: An unintended admission that EVERYONE should focus on: The article stated "they only measure ‘moisture’ (not relative humidity). Moisture, NOT humidity is what causes failure mechanisms to become active...and this statement IS correct, RH probes do NOT measure moisture, these measure humidity (water vapor).

Fabrication and Misinformation #2: This means that a slab that may have been “dry” (low RH) at the surface (without a floor covering) will see a higher RH (migrated from down in the concrete) at the surface when the floor covering has been installed. This is where the problems occur.

Facts and Clarification #2: This is a nonsensical statement since there is ZERO determination or qualification stated what constitutes a "dry" slab. The statement "this is where the problems occur" is flat out false. I and several others have tested under floors that have been installed successfully for weeks, months and even years. It is actually very uncommon for the RH under these floors to be less than 90%, which according to most specifications is considered "excess humidity". Yet these floors aren't failing...so much for "this is where the problems occur". That is a flat out false statement.

Unintentional Admission and Misinformation #1: "Keep in mind that an uncovered concrete slab will indeed have an RH gradient (typically drier at the surface; much wetter at depth) throughout its thickness until a floor covering is put on top. Under normal conditions, the RH at roughly 50% slab depth will be significantly higher than the surface unless the slab has been down for a long time, and a vapor retarder is directly underneath the slab."

Admission and Clarification #1: Although there is an admission of a gradient being present, this person does not understand concrete well enough to know that the gradient is limited to what has been stated in numerous studies of between 0.75-1.0 inches (19 mm - 25 mm) into the concrete. The humidity is typically higher well before the 50% slab depth and in a 5 inch slab, approximately 80% of the slab is at or near the same exact humidity level. A gradient is exactly what it states...it is an area that behaves differently from the remainder of the concrete. This is CRITICAL knowledge when evaluating the concrete for any coating or flooring installation. All concrete to a certain extent has autogenous shrinkage, self desiccation and other factors that are limited to the top surface of the concrete. THIS is what creates the gradient, which is a permanent part of the concrete, yet RH probes cannot differentiate the differences between the more permeable and porous surface and the body of the concrete. RH probes measure air, and cannot determine the volume, frequency or deviations in these air spaces...if a probe were to be inserted into a small cup or large barrel, if each has the same humidity, then these would be evaluated with no ability to account or compensate for volume.

Fabrications and Misinformation #3: "At best, concrete moisture meters (pin-type or surface-type) may have some practicality as relative (qualitative, not quantitative) measurement devices for possibly indicating best placement for accurate, quantitative RH sensors within the concrete. Moisture meters for concrete, similar to other non-quantitative test methods, are not final determination tools."

Facts and Clarification #3: The "at best" statement is factually incorrect, as is the claim of "quantitative RH". In the study used for the RH probes for the mix water of concrete, there is a caveat in the study that RH promoters deftly side-step. Why do they side step this? Because once people understand its importance, they no longer use the RH probe as any form of a moisture quantification. In concrete, alkalinity exists in greater and lesser amounts and varies throughout the concrete. As noted in the Hedenblad Study, in the presence of alkalinity, even if the concrete has the same moisture content, the humidity readings will be lower. Missing from the study is even with MORE moisture, if the alkalinity is higher, the humidity measurements might STILL be lower as these measurements would be dependent upon the concentration of alkaline salts in water.

This is how the industry standard calibration solution works..it contains salt and water and will not allow the humidity to exceed 76% no matter HOW much solution is present, whether it is 10% full or 90% full, the humidity measurements remain the same. At best, this is quantification without context, which can be more detrimental than helpful.

FACTS that MUST Be Considered

Humidity measurements do not and CANNOT measure the moisture content of concrete, these measure where the concrete ISN'T, which is any area of open space.

Humidity is water vapor. Water vapor does not transport solids or salts, water vapor doesn't create any sort of moisture barrier, and there exists no empirical data that can state precisely how much humidity will cause a moisture related flooring failure. I have asked repeatedly for justification of humidity limits and over the past 20 years of such requests, still nothing. I think it is safe to say if such data DID exist, the RH probe promoters would be screaming this from the mountain tops.

Every single failure exists when moisture is in a liquid form.

The real culprit; condensation at time of installation, and AFTER successful installation any damage experienced is due to some form of chemical compound suspended in water.

In a prior article, I address the types of condensation/moisture that ARE the cause of moisture-related flooring failures: Dew Point, Condensation and Ionic Dew Point....THAT is the three headed hydra you should fear. If these are known, addressed and compensated for, most, if not all these current moisture claims will no longer plague the flooring industry.