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Calcium Carbide testing and Silicates

I have a project were Calcium Carbide testing is being used to attempt to show the performance of a topical silicate.
Is the test capable of determining Moisture Content (of the sample) once the concrete is contaminated with a silicate. I believe the surface test sample has the highest concentration of the silicate which maybe altering the results.
I believe the test is only shows the MC of the surface at best and has no way of determining to moisture reservoir that will ultimately make it's way to the surface where it will over time affect an adhesive.

The job is in the USA but the product linoleum is made in Europe by Armstrong.
The adhesive Mapei Ultra Bond G 21 2 part Urethane only references 2170 or 1869. 75 % and 5 lb .
The opposing consultant position is that the Calcium Carbide test is a valid test showing a dry condition.

My F- 2420 Dome testing reading which started out at 52% increased to 85% (a gain of 33% ) after only 5 day. Ambient conditions were under permanent house HVAC of 70 f and 40 % ambient. I did not flush the domes with Nitrogen. I have Wagner reading averaging 89 % and CC readings of 5.4 lbs.
I say the Silicate is NOT working. What say you ?


I had a similar situation on a job. (I think you were on that job, or at least someone told me that was you in a picture, with a large water jet shooting out of a blister, now used in Koster's marketing literature. )

I believe what was done was the blister water was shown to have turned into a sort of high pH acid and the presence of that high level showed why the adhesive emulsified and the floor bond failed. I believe that was a G21 installation over slipsheet.

Are you sure about the G21 75%&5#. Is that DLW's #? (DLW is the factory Armstrong lino is made, my father introduced them the USA back in the day before Armstrong bought them) I know in the sports world G21 is used with many slip sheets and those manufacturers let it go much much higher.

I have also had success is CaCl consultants testing over cracks. That can result in higher CaCl levels. Different silicate manufacturers say different things about treating cracks and it is often on a 2 sided doc that the 2nd page never gets submitted.

What did the lab say about cores? Often I have seen cores taken to see if the Silicate has penetrated the correct depth into the surface. I am unsure if a correlation between silicate penetration and failure has ever been demonstrated.

Finally, is there a sand blotter layer?

Is this really Bill posting on here?

I am unfamiliar with carbide testing but from what I have heard of it, it is accurate for what it does.

Is the test appropriate? Not in my book.

Silicates don't shut down the concrete capillaries as they claim. This has been proven by many experts in the field, and I'm sure Lepito has proven this also. So a CaCl test reveals the MVER still coming from the slab.

The carbide test will show the amount of free water in the sample collected, I don't doubt that, and I would suspect the test parameters will instruct to only take concrete samples from the top treated horizon of the concrete where free water has been bonded by the silicate. This is all fine and good, and the carbide numbers may be rather low, but the slab still is emitting vapor as evidenced by the 2420 test.

Looking back at what I just wrote, I think I said the same exact thing as Lepito. Wink

The fact of the matter is that these silicates were not designed to be vapor mitigation systems, they do not perform as vapor mitigation systems and there are failures when they are used as vapor mitigation systems! Testing moisture by methods unsupported by the flooring and adhesive manufacturers only serves to provide a poor claim of functionality for the silicate proponents. Smoke and mirrors if you will.
JD Grafton
Concrete Answers for Flooring Problems

Oh carbide test... what is that?

(09-15-2012, 12:32 PM)eaadams Wrote:  Oh carbide test... what is that?


It's a test silicate manufacturers try to create smoke with. Tongue
JD Grafton
Concrete Answers for Flooring Problems

Hi J.D. Yes it Bill.
Been a while since my last post.
I'm sure about 75 % and 5 LB as i have the data sheet in my hand for Mapei Ultrabond G21.

The project eaadams is referring was in Bakersfield Ca in an elementary school. Were you on that job ?

On today's project No sand blotter layer, good quality vapor retarder in direct contact with the concrete.
The question is :
Does silicate contamination render the test VOID when the test sample is treated with a silicate?

i can not find any reference to this question on the web.

IMHO the 2420 test will always accumulate RH inside the hood. The standard attempts to address it by stipulating the amount of acceptable drift in your reading once you've waited the 72h. If you're testing the performance of a mitigation product, it's only useful if you've tested the bare slab prior to the application, but as JD says, it at least evidences the fact that vapour is still emitting, albeit a little innacurately.

I love that geyser pic! Scott Tarr and Peter Craig have been dining out on that one for yonks... Smile
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher


Bill has become famous because of that one impromptu photo... Everyone has seen it! Big Grin
JD Grafton
Concrete Answers for Flooring Problems

(09-15-2012, 06:13 PM)Lepito Wrote:  The project eaadams is referring was in Bakersfield Ca in an elementary school. Were you on that job ?

(09-16-2012, 09:15 PM)CC Solutions Wrote:  Bill has become famous because of that one impromptu photo... Everyone has seen it! Big Grin

Yes we are the California 'partners' (distributor, contractor, a/d reps) with that flooring manufacturer. We were the replacement contractor on that job. Praying it is still staying down tight, nasty slab, nasty job. I was also the person that brought VAP in on the job. Still amazed they didn't require an isolation screed. I was also the person that 'pointed' the owner / architect to many of the consultants.

No one asked me for a autograph yet. Got a lot of milage out of that photo.
So the question remains can a Calcium Carbide test be performed on concrete that previously was treated with a Silicate? I can find nothing to support or dispute doing this test on concrete that has been sprayed with a silicate.

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