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Adhesives and Moisture

#1
Food for thought:

A little tidbit I found in some lit:

302.2R-18 ACI COMMITTEE REPORT

"shown that the adhesive strength decreases with an increase
in the concrete’s MVER. When these tests were conducted,
however, there were no criteria for acceptable bond strength,
and scatter in the test results did not indicate a clear dividing line
between acceptable and nonacceptable adhesive bond strength.
A report on recent testing that attempted to correlate moisture
in the concrete with floor covering performance concluded
that: “The evidence presented suggests that there is no
relationship between the relative humidity of a concrete base
or screed and adhesion of resilient floor coverings” (The
Concrete Society 2004).
While moisture criteria are often used, the relationship
between these criteria and floor covering performance is not
well understood."
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#2
Thank you for posting that Ernesto, these boards have been kind of quiet this week!!

I think I can read between the lines of your post. Please remember there is no correlation between MVER and relative humidity. A perfectly dry slab that is sprinkled with water for a few seconds will have a terribly high MVER, and this can have an effect on adhesive bond.

Also true is a slab with no vapor retarder can seem very dry and have a good MVER reading, yet fail over a short period of time after moisture wicks through the slab and attacks the adhesive bond.

I'm repairing a slab soon that had great MVER readings when the floor was installed but has since failed and now has high MVER readings. The slab is on a blotter layer of sand. The RH tests were bad from the get-go, but the installer went by the MVER readings because they were within specs.

This is why manufacturers are changing their specifications to rely less on the outdated CaCl test. You just can't trust MVER tests alone.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#3
Quote:I think I can read between the lines of your post. Please remember there is no correlation between MVER and relative humidity. A perfectly dry slab that is sprinkled with water for a few seconds will have a terribly high MVER, and this can have an effect on adhesive bond.

Yes, but remember are we not saying that when the floor is covered by an impervious or semi-impervious floor covering that the moisture in the slab then migrates upwards and evens throughout the slab (equilibriates), therefore causing higher mver?

Isn't that the crux of the reason why we are now told that cacl tests do not work good enough?

But where is the criteria for lessening bond strength with higher rh in the slab. Thats what it says.

Do you have any scientific data that states other wise besides what manufacturers tell us?

I think all you inspectors better start rethinking the way you write up reports on this subject.
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#4
Hi Ernesto,

Is there a question in there somewhere? I will be gone for a week, but would like to think this through with you!
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#5
Yes there was a question. But I forgot my train of thought now. Perhaps it has no meaning what so ever.Rolleyes
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#6
Ha ha ha .... Now you know what it's like to be old like me!

Say I just got a job on a slab with no vapor retarder and on a sand bed. It has a long history of water problems, but over the last 6 months has been gutted and is being added to and remodeled. The old slab right now is reading 3 - 4 lbs MVER and I was asked to mitigate for moisture. The principals know as soon as they put a floor back on the concrete they will have problems again...

Nice job too.... about 24,000 sf. Big Grin
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#7
My solution to that problem is to simply drill a hole through the slab eleviating the mver pressure and turn it into a drinking fountain..Tongue
Might need a condensing unit.

I am on residential slabs and been around a few construction sites in my day. Never seen no one out here use a vapor barrier. So....why even bother with testing the slab, just throw down some vapor retarder on top eh?Rolleyes
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#8
I suppose you have to if you have moisture sensitive flooring!

I work in commercial buildings, mainly medical facilities. Vapor retarders are always specified for new construction, but I run across a lot of older remodels that either have a deteriorated retarder or one that has been compromised. The hardest to explain to clients is why they have problems with a new homogenous vinyl floor when their old VAT or ceramic floor was doing great for 40 years.

Hey Ernesto, are we the only guys on here? It's been quiet lately. I even gave a shout out to Ray and he didn't reply..... Tongue
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#9
Which Ray are we talking about? I know of two, one here and the other has his own tek forum. But the latter is mad at me and kicked me off his board. If ya don't want my answers then don't ask the hard questions I always say. Cool
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#10
This Ray... Ray Thompson.

Kicked you off his board? You seem like an intelligent thoughtful person to me. Everyone comes from a different background of experiences and approaches a situation from a different perspective. All we can do is relay our findings and recant what we have found to work.

One thing I have found over the years is this: There are hundreds or even thousands of 'experts' in this field....... And most of them don't know the basics, let alone the real issues.

I just had this added to the back of my business cards:

Beware the man who knows the solution without fully understanding the problem.

I run across those types all the time. Sad
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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