Moisture Testing - Moisture Science Unraveling the Mystery

In the fierce competition for dominance in moisture testing of building materials, many who manufacture, market, study, use and distribute such methods and devices seldom understand exactly what it is their respective devices actually measure, or how these either align or do not correlate with other methodologies.

Concrete Moisture Testing - A "Moving Target"

There are very few building materials used in construction that are more ubiquitous or confounding than standard concrete. Even the origins are often mixed and matched to the point where the initial emergence of what was first used, used n certain time periods as opposed to what is being used today are obscured either by accident, research laziness or by design.

Concrete - Thousands of Years Old - Yes and No

I was taught, lead to believe and held the belief that concrete was thousands of years old as articles addressed current concrete construction. That is a very misleading approach that has helped continue MANY fallacies.

Portland Cement concrete was developed and patented in the UK in the early 1800's by Joseph Aspdin. This is well-known...HOWEVER, what is lesser known and something of a precursor to questionable practices that followed, was that the son of Joseph Aspdin (William) was credited with launching the Portland Cement Industry.

From Wikipedia: ?William Aspdin had a history of "financial missteps" and questionable business arrangements suggests that William may have been both inept and dishonest.

I find it VERY interesting that the "founder" of the Portland cement industry is never mentioned in any of the concrete references or history of concrete.

One of the favorite tales of the Portland cement industry is to cite Roman, Egyptian and other ancient forms of concrete, that in reality are vastly different in both chemistry and characteristics.

It is true that the general heading of cement contains many geopolymer, calcium aluminates, along with Portland cement under the broad heading of "cement and concrete", however, these are not interchangeable in with history or composition.

Ch-Ch-Ch-Changes in concrete composition

From the 1920's until today, Portland cement has undergone significant changes. Even to the point where these changes SHOULD have been noted and clearly differentiated, but weren't.

In a very good article that appeared in a 1980's ACI publication, it was noted that with finer grinding, concrete of a specific compressive value (28 day) could be obtained with less cement. It was stated that upwards of 34% less cement was used for concrete in the 1980's as opposed to the 1950's. It was also noted that the permeability of the 1980's vs 1950's concrete, the 1980's concrete was 500% more permeable. Also noted, but somewhat obscured in detail, was the greater heat generation of the finer grind Portland cement.

Perhaps the most significant change began in the early 2000's when cement plants were forced into compliance with the EPA requirements of capturing flue gases to reduce the carbon footprint. One of the requirements was to reintroduce CKD (Cement Kiln Dust) back into the cement production.

Adding CKD increased the alkalinity of each cement production as they gradually came into compliance. So much so that when essentially all the cement plants came into EPA compliance, the concrete industry "announced" (2019) that low alkali cement would no longer be available.

For those who produce products that are used or installed over concrete, this should have been a major announcement since the concrete is now significantly more alkaline than it was in the past, with essentially all prior studies involving concrete have questionable relevance to what we are using today.

How this affects Moisture Testing

I needed to "set-the-table" so those reading this can now understand the why's and how's of moisture testing, particularly the methods that are significantly affected by the changes in concrete, particularly increased alkalinity.

ANY and ALL humidity testing is dramatically affected by alkalinity. The higher the alkalinity, the lower the RH measurements will be, irrespective of the actual moisture content, which is well represented in the photo by Clayton Shull. The RH in the air space is what is measured. If this container (or concrete void, capillary, etc.) was 1/8, 1/3, 1/2, 3/4, 7/8 full, the RH measurements would remain EXACTLY the same!

To a lesser extent, this also pertains to the F1869 CaCl test, E96, or any other method that relies upon a desiccation method to measure moisture. The desiccants currently used are NOT able to remove (measure) moisture at a certain point since the desiccant salts contained in concrete (calcium hydroxide and sodium hydroxide) have significantly lower humidity equilibrium than the desiccants used to extract moisture.

What this means is that there can STILL be liquid water within concrete that calcium chloride or other desiccants cannot remove and cannot measure or even give a hint as to this condition.

More subtle is that as moisture is extracted, this continuously increases alkalinity in the concrete, which also increases the resistance to moisture removal/uptake!

This CANNOT be overstated in importance! Nearly every single study has ignored or not considered this effect, with much confusion as to why predictive analysis continues to miss, where each study remains unresolved.

To Properly Test Moisture in Concrete

With the challenges noted earlier, there are additional challenges that also fly "under the radar". These are five forms of moisture, where most only recognize 3 forms of moisture. The three forms of moisture we are taught early on are gas (water vapor/humidity), fluid (liquid water) and solid (ice).

For building envelopes, there are two other forms of water which are; adsorbed moisture and absorbed moisture. Hence my criticism of most "certification bodies"...this isn't taught ANYWHERE in ANY of the curriculum I have read (at least in the flooring industry).

RH measuring devices can measure ONLY water vapor/humidity. RH devices CANNOT measure liquid moisture, CANNOT measure adsorbed moisture or absorbed moisture. Hence my irritation that these devices have even been CONSIDERED, much less used as a Concrete Moisture Testing protocol.

The desiccant-dependent type of tests can measure water vapor and liquid water IF the liquid water is not adsorbed or absorbed.

Adsorbed and absorbed moisture are present due to attractive forces that actually compete against the attractive forces of the selected desiccant methodology.

Any alkalinity or hygroscopic material is present, and not knowing how much or where the alkalinity and/or hygroscopic material is present. This unknown prevents desiccant-dependent methods from producing a reliable measurement of moisture content.

Gravimetric Measurements - The Industry Baseline

Gravimetric is the baseline ALL devices should be measured against IN THE FIELD. Laboratory gravimetric does not and cannot simulate field conditions. There have been methods pre-qualified under laboratory conditions when compared to gravimetric, but when brought out into the field, the results no longer were correlative, with some so far apart from gravimetric, there was simply no way to obtain meaningful correlation.

Gravimetric yields accurate results, but for all intents and purposes are not useful for any concrete structure or flooring surface that uses a truckload or more of concrete. It is impractical, destructive and expensive.

What is needed is to use a device that aligns with gravimetric, thankfully there is one device I found that fits this criteria, the Tramex Concrete Meter.

There may be others that will eventually prove effective under field conditions where gravimetric is used as the baseline, but until then, I cannot and will not recommend anything that hasn't yet been proven.

Measure Where the Problems are

Lastly, the dynamics of moisture dictate accuracy of moisture testing, not the unfounded garbage we have been led to believe.

We have been brainwashed to believe that once moisture enters concrete, it decides that the laws of thermodynamics no longer apply!

Seriously, I even had one of the RH Testing experts try and argue that humidity in concrete is different from humidity in the air...that made my head hurt. Although I do admit I had a lot of fun when I asked him to explain the differences. Hint: he couldn't.

Moisture moves from warm to cool. In most environments, the room averages warmer than the concrete surface, the concrete surface averages warmer than the concrete underside..which means according to the laws of thermodynamics, the moisture migration would be downwards, NOT upwards!

The surface of the concrete has been established as the source of compromised quality. The gradient in (recent) study after study is established at 0.75-1.0 inch into the concrete surface. One study even showed that the moisture in the concrete remained constant and unchanged even when the surface was exposed to 150-160 degree heat.

What those who have taught us incorrectly have ignored, are the laws of diffusion and that chemicals tend to become more reactive and active with increased temperatures...THAT is the origin of the surface moisture and ensuing issues with surface coatings and flooring, NOT from underneath.

The concrete capillaries can act like a freeway for transport of salts, the freeway doesn't move, but there is an active transport of cars.

I water, where higher concentrations of contaminants, salts, etc. exist, diffusion tends towards equilibrium....easily demonstrated by adding a dye to water..the dye mixes faster in warmer water and the water isn't moving, even as the dye eventually comes into equilibrium.

The long held belief that moisture migrates from the underside to the surface is a misunderstanding of diffusion, it ISN'T moisture migration, it is diffusion of contaminants where the areas of higher concentration enter and diffuse to areas of lower concentration, even as the moisture remains stationary.

Modern Example - Type I cement vs Type III cement

I like to use this to underscore the significance of finer grinding. If one were to try and place a 6 inch slab with Type III cement, the results would be a concrete that is much more subject to significant cracking and curling, particularly due to the internal heat generation of Type III cement.

Here is the kicker, chemically there is NO chemical difference between Type I and Type III cement. The ONLY notable difference is that Type III is a finer grind, and as such, is designated as a "rapid setting" cement.

Back to Basics

One of life's biggest challenges is to unlearn what you've been led to believe is a fact. When I first started to realize that a lot of what I thought I understood was nonsense, each step of this rediscovering (after my anger and frustration passed) became easier and clarity of thought allowed for an acceleration of discovery, to where it is now exciting. When we get back to basics, we start solving problems rather than the current trend of creating problems.