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pH Testing - it is NOT being taught correctly
pH Testing Necessary, but Misunderstood
To ensure concrete moisture testing is accurate, it is imperative that pH testing be conducted to determine the concrete is clean, open and without any adhesives, coating, curing compounds, etc. pH testing should never be separated from “moisture tests” because without knowing the pH value, the moisture results could be VERY confusing, leading to incorrect diagnosis and/or subsequent repair/remediation.
What pH testing does
pH testing shows if the concrete is the proper pH, rather than the “improper” pH. Meaning that although there are written restrictions given by some manufacturers and to what constitutes a “safe” pH, these levels are for the most part, meaningless as the pH is at 9.5 or higher.
Fully “neutralized” concrete has a pH which is the same as limestone (which is a slightly alkaline stone). Neutral for water is 7.0, but that is actually acidic for concrete. In fact anything below a pH of 9 should be considered “acidic” for concrete.
Limestone has a pH in the range of 9-9.5. Limestone chemically is calcium carbonate. Concrete when fresh is alkaline 12.0-12.5 due to the natural formation of calcium hydroxide as “cement” develops. Neutralization occurs most commonly by exposure the the CO2 (carbon dioxide) in our air. When this carbon dioxide is absorbed by the moisture in concrete, it “carbonates” (carbon dioxide when added to water produces carbonic acid, same as that used to make sodas "bubbly")...turning into – calcium carbonate. So if any surface pH readings are less than 9, there is something on the concrete interfering with accurate testing.
It is not uncommon for concrete to have a pH as high as 13.3 (extremely alkaline), which is mostly caused by sodium hydroxide (and to a lesser extent; potassium hydroxide) that is a natural by-product introduced during the sintering process. In the last few years, the sodium hydroxide content has increased (created by environmental concerns that require the “recapturing” of flue gases) by as much as 400% percent in some cement mixtures, creating problems with alkalinity that were not as much of a concern in prior years. This is where it gets confusing: sodium hydroxide is highly “buffered” meaning it maintains a high pH through a HUGE range of concentrations.
At 1% concentration, the pH of sodium hydroxide is about the same as fully concentrated calcium hydroxide – pH of 12 (which can lead to misidentification of elements if analysis is not done), at 10% - pH of 13, and holds this high pH until almost fully concentrated, when the pH value goes to 14. Since fresh concrete has a range of 12-13.3, concentration of the much more damaging sodium hydroxide is unknowable with a simply pH test. At a 10% concentration, likely is not damaging to a coating or adhesive, but at concentration levels higher than 20% almost assuredly damaging and in higher concentrations, the effects can be devastating to a floor assembly.
Complications of pH Testing
It is common for specifications to state that the flooring installer, a “certified test agency” or possibly even a laboratory conduct moisture tests. In truth most, if not all these agencies are not sufficiently skilled nor taught what pH values mean and many “professionals” think that pH and alkalinity are correlative - they are NOT!!!
To my knowledge, this information is NOT taught by any of the private schools or professional organizations as to how to properly teach moisture and pH testing. Until the facts are known, certification of such individuals is of suspect value. This may sound harsh, but it IS the reality of where the flooring and even concrete industry sits at the present time.
To ensure concrete moisture testing is accurate, it is imperative that pH testing be conducted to determine the concrete is clean, open and without any adhesives, coating, curing compounds, etc. pH testing should never be separated from “moisture tests” because without knowing the pH value, the moisture results could be VERY confusing, leading to incorrect diagnosis and/or subsequent repair/remediation.
What pH testing does
pH testing shows if the concrete is the proper pH, rather than the “improper” pH. Meaning that although there are written restrictions given by some manufacturers and to what constitutes a “safe” pH, these levels are for the most part, meaningless as the pH is at 9.5 or higher.
Fully “neutralized” concrete has a pH which is the same as limestone (which is a slightly alkaline stone). Neutral for water is 7.0, but that is actually acidic for concrete. In fact anything below a pH of 9 should be considered “acidic” for concrete.
Limestone has a pH in the range of 9-9.5. Limestone chemically is calcium carbonate. Concrete when fresh is alkaline 12.0-12.5 due to the natural formation of calcium hydroxide as “cement” develops. Neutralization occurs most commonly by exposure the the CO2 (carbon dioxide) in our air. When this carbon dioxide is absorbed by the moisture in concrete, it “carbonates” (carbon dioxide when added to water produces carbonic acid, same as that used to make sodas "bubbly")...turning into – calcium carbonate. So if any surface pH readings are less than 9, there is something on the concrete interfering with accurate testing.
It is not uncommon for concrete to have a pH as high as 13.3 (extremely alkaline), which is mostly caused by sodium hydroxide (and to a lesser extent; potassium hydroxide) that is a natural by-product introduced during the sintering process. In the last few years, the sodium hydroxide content has increased (created by environmental concerns that require the “recapturing” of flue gases) by as much as 400% percent in some cement mixtures, creating problems with alkalinity that were not as much of a concern in prior years. This is where it gets confusing: sodium hydroxide is highly “buffered” meaning it maintains a high pH through a HUGE range of concentrations.
At 1% concentration, the pH of sodium hydroxide is about the same as fully concentrated calcium hydroxide – pH of 12 (which can lead to misidentification of elements if analysis is not done), at 10% - pH of 13, and holds this high pH until almost fully concentrated, when the pH value goes to 14. Since fresh concrete has a range of 12-13.3, concentration of the much more damaging sodium hydroxide is unknowable with a simply pH test. At a 10% concentration, likely is not damaging to a coating or adhesive, but at concentration levels higher than 20% almost assuredly damaging and in higher concentrations, the effects can be devastating to a floor assembly.
Complications of pH Testing
It is common for specifications to state that the flooring installer, a “certified test agency” or possibly even a laboratory conduct moisture tests. In truth most, if not all these agencies are not sufficiently skilled nor taught what pH values mean and many “professionals” think that pH and alkalinity are correlative - they are NOT!!!
To my knowledge, this information is NOT taught by any of the private schools or professional organizations as to how to properly teach moisture and pH testing. Until the facts are known, certification of such individuals is of suspect value. This may sound harsh, but it IS the reality of where the flooring and even concrete industry sits at the present time.
Replies to This Discussion
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Permalink Reply by Bob Higgins on -
The reasoning for sanding or grinding the surface, is to remove contaminants and coatings that would interfere with testing OF the concrete. If you want to properly test the metal under a coating..you have to remove the coating to get to the metal.
Sometimes concrete will appear to have a sound surface, because it was finished too early...grinding and sanding will sometimes reveal hidden problems.
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Permalink Reply by Stephen on -
But Bob, if I do the water drop test and the drop absorbs within a minute would that not tell me if there is a contaminate or sealer on it?
And what kind of hidden problems are we speaking of? Small fractures under the surface?
How about steel troweled surfaces releasing less water vapor, true or false?
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Permalink Reply by Bob Higgins on
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sealer surfaces are notorious for "sealing" concrete, with the small "skin" of the surface creating sometimes a virtually impermeable surface..which also creates problems with the set time for adhesives....there is no where for the water to go, so it gets entrapped between a sealed concrete surface and a non breathing to low perm floor, creating what LOOKS like a moisture problem
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Permalink Reply by Stephen on
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Bob, I don't think you really answered my question about the water test and therefore the need to abrade, sand or grind the surface. Will you not possibly get a false reading on the ph test ot calcium chloride test?
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Permalink Reply by Bob Higgins on
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Stephen that is still a big "maybe". Some curing compound can degrade fairly quickly and absorption of moisture doesn't say whether or not the surface is still contaminated. A really well-cured concrete surface may absorb moisture very slowly..this is as much art as science. These are great points for discussion to properly set up scenarios within a classroom environment, showing the different readings one can get...
If you grind the surface, it should be well cleaned before pH testing...freshly ground concrete surfaces, even if fully carbonated can reveal alkaline materials not readily available to the flooring assembly under normal circumstances.
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Permalink Reply by Stephen on
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Well....yea uh ya don't know how long I have been asking that question and not getting any answers Bob, thanks. It would be interesting if we could do a class that had samples of varying degrees and kinds of sealants and surface finishes like steel troweled etc.
Not only is ph testing being taught wrong, I have witnessed pictures of inspectors placing a CME on a concrete surface immediately after pulling a glued down plank and calling the concrete as too wet. Well of course the surface is going to register very high on a CME immediately after pulling a glued down plank, thats not even taking into account the adhesive residue on the surface of the concrete besides the concretes rh being in equilibrium
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Permalink Reply by Stephen on
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Found an interesting article on ph testing
http://findarticles.com/p/articles/mi_qa5363/is_200704/ai_n21285402...
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Permalink Reply by Bob Higgins on
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I like the article...lot's of good information in it..but I am going to talk to my buddy who was one of the authors about a few details before I comment further..thanks Stephen!
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Permalink Reply by Wooden Scavenger on -
Bob:
With all due respect for your knowledge . . . I still can't figure out what the relationship is between pH of the concrete and an accurate moisture reading.
Please, explain.
Thanks.
Wood Scavenger
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Permalink Reply by Bob Higgins on
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Actually these conditions can be unrelated.....there is an assumption that moisture problems and high pH and/or high alkalinity are correlative....it "suggests" there may be a moisture issues, but each can exist without the other...both tests should be part of an inspectors checklist..to rule things in..as well as rule things out.
I did an inspection for Armstrong several years ago in the gulf region...the adhesive was fried off from the high concentration of alkalinity from the concrete (extremely corrosive to the adhesive), but there were no "moisture issues".
Turned out the concrete was contaminated with alkaline materials from improperly washed sand taken from a source where high lime contents were present at the excavation site.
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