Concrete Moisture Testing - RH Probes Do NOT Test concrete Moisture. That claim is False!

I just read a couple advertisements saying how RH probes can measure the moisture content of concrete, or test moisture of concrete. Neither claim is true, yet the false claims persist.

The first claim from several years back was that RH Probes were the "most accurate method of testing the total moisture content of concrete", then the claim morphed into "best method of measuring the moisture condition of concrete", and again, can be "used as a predictor of future moisture problems"....not a single one of the claims is true, and if people would pay attention, no one would be using RH Probes to try and measure moisture under field conditions, why? Because I have yet to see or read ANYTHING confirming RH probes are accurate or even assignable to in place concrete.

The Title Says it all - ASTM F 2170 - Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes

What the standard DOESN'T say and remains as an unfounded sale gimmick, is RH probes DO NOT measure the moisture content and/or moisture volume in concrete, irrespective of what is claimed. The data referred to since 1997 is based on this study: Hedenblad, G. Drying of construction water in concrete. Drying times and moisturemeasurement. Report T 9:1997. Swedish Council for Building Research. Stockholm.Sweden. Distribution: Swedish Byggtj?nst S-11387 Stockholm.

I want everyone reading this and please share it to those involved or affected by the outcome of such field measurements, this study is based SOLELY on the construction water in concrete.

What is construction water in concrete these probes measure? It is the water that remains (after the bleed water has evaporated, the concrete has set and the initial hardening has taken place) that was used in the initial mix design AND is based on the concrete NOT being rewetted or under field conditions. The RH Probe is a straight drying indicator based on fixed temperatures and humidity.

These have NOT been tested or approved by third parties as a method to measure concrete that is subject to field conditions, or after a floor has failed.

What is Concrete Moisture and how can it actually be tested?

Up until a few short years ago, the only method that I would have considered an accurate method is gravimetric (oven dry test). This methodology has been used by hundreds of different industries where knowing the accurate moisture content is critical. As accurate as it is, the method has almost no practical application for any concrete past small samples. The methodology is destructive, expensive and as impractical as it is accurate if being considered for concrete.

I read a study that was performed in Finland where different moisture test methods were first evaluated in a laboratory environment, then brought out into field conditions where bridge decks were chosen for evaluating the effects of environmental dynamics outside a well-controlled laboratory environment.

After 28 weeks exposure, only the Tramex Concrete Meter correlated with the gravimetric. My initial response to the Tramex personnel was "Do you have any idea how significant this study is?" At first they weren't as impressed as I was about their own product since they have been field proven over and over again by the various professions of waterproofing, restoration and building sciences.

I shared with them that this PROVES not only just how accurate their concrete moisture tests were with their concrete meter, but instead of the ponderous, tedious, expensive and completely impractical gravimetric method, they literally had a method that mirrors the accuracy of gravimetric and the data is available in minutes, rather than hours or days.

Concrete moisture is well established by the concrete industry and academia as the moisture content of concrete that resides in the pore water and capillaries within concrete. The form of this moisture is in a liquid form. Moisture in a liquid form is INVISIBLE and unmeasurable with ANY form of humidity measuring device. Additionally, moisture in a liquid form is very high volume moisture when compared with the vapor form, which is what humidity devices measure. Even water mist is essentially unmeasurable using a humidity measurement method.

To place this in perspective; if you take a cubic meter (35.3 cubic feet) of an open area, it would take slightly more than 264 gallons of water to fill that space. Now compare the volume of water needed in a vapor form to reach 100% RH (saturation): slightly less than 2 ounces of water!

WHY are we being led to believe that a potential of 2 ounces of moisture is somehow more significant than 264 gallons of water? THAT is the comparative and WHY humidity measurements CANNOT "test" concrete moisture content...RH devices measure the air space, NOT the anything or anywhere liquid water is present in the concrete.

One Bad Claim after Another

I am going to hold some of the RH "experts" accountable for their many non-facts, and in many cases, nonsensical claims..in no particular order:

1. RH Probes measure the total moisture content of concrete.
2. RH Probes can be used as a predictor of future moisture problems.
3. RH Probes measure the moisture condition of concrete.
4. Water vapor can carry salts and acids (yes, they actually said this).
5. Water vapor (humidity in excess of stated limits) cause flooring failures.
6. Once an alkaline solution is saturated, the humidity will return to 100%.
7. When criticizing CaCl testing, which was the industry standard at that time: "If moisture testing is so accurate, why are we still having failures?"
8. Moisture only moves through concrete in a vapor form.

I am not making this up...I even have a handout given by one of these "experts" who claimed calcium chloride tests are deficient because an environment with warmer, humid air can "exaggerate" moisture readings, even as the moisture hasn't increased.

That claim was an inadvertent admission the presenter doesn't understand moisture dynamics and couldn't recognize something as simple as higher humidity and warmer air will increase the moisture content of a cooler concrete surface.

I generally do not like coming right out and criticizing someone for ill-obtained information, but the persistence of misinformation is hurting people and businesses....There is NO legitimate reason the flooring industry should be experiencing 3 billion in estimated moisture claims per year...we CAN bring that total to near zero....and finally, I will reiterate what the RH expert stated when criticizing CaCl testing: "If moisture testing is so accurate, why are we still having failures?" To which I will add, if RH testing is so accurate, why have moisture failures increased?

What is the value of ANY test methodology if it isn't solving problems?