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ICRI pH testing Concrete Repair Bulletin

I thought people would be interested in this article in the ICRI Concrete Repair Bulletin. Ashok lives close to me, but I haven't yet worked with him directly.

I think the point of the article sums down to the debate over what a 'clean concrete slab is' from F710. And that goes back to the proper prep of a surface under ASTM F1869.

Here is the article: https://www.icri.org/publications/2014/PDFs/marapr14/CRBMarApr14_Kakade.pdf

Essentially we will be sweeping up concrete dust and creating a water solution. Crazy. I can't imagine how expensive (time) that would be. But what I do like is the change it would force to every CaCl test 'kit' out there.

It will certainly affect people using the wagner ph meter. http://www.wagnermeters.com/shop/rapid-rh-and-concrete-moisture-products/rapid-rh-digital-ph-meter/

My largest objection is this statement: "However, the concrete surface is generally shot blasted in preparation for installing new flooring." A completely unrealistic statement. From a flooring installers perspective it would be cost prohibitive to shot blast every floor. Also I know of no installer who will lay a floor over a shotblast floor without some amount of skim coat on the surface to smooth out the profile. maybie w/carpet

I know there is some discussion about F710 and there was a recent change to ASTM F1869 that changed what surface prep to do before testing. I would hope whatever is decided is a unified approach across standards regarding ph. http://www.astm.org/DATABASE.CART/WORKITEMS/WK28850.htm

Further, this procedure seems to be create a ph solution out of cement dust. This seems counter intuitive of the goal of PH testing. The goal of ph testing is to see the ph environment an adhesive will be exposed to when glued down with a floor. If you get too much vapor under the floor, salts move up with the vapor and create a salt solution on the surface, in the presence of adhesive but under the flooring. Vapor doesn't move up and grind the surface of the floor. Further it is vapor not a liquid water drive so saying water moves up through the floor is also wrong.

Very interesting Evan, thanks for that.

Still- for the purposes of a warranty, what will the manufacturer accept? They won't look past F710 for now I presume, but this does look to address some of F710's problems.

The biggest issue with pH testing I find is that ogre of power troweled / burnished surfaces. If it fails a simple bead test, pH testing the usual way is pointless as you're only measuring the water on the surface. I now charge extra for pH testing and more if I need to use a hand grinder to open up the surface.

I note this report says that 50G sandpaper will be able to "scarify a hard-troweled surface". I'm not sure- some of the burnished surfaces I've seen won't open up without grinding.
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher


Thanks for that eaadams. But wouldnt he be mixing in the carbonated with the underlying concrete and getting a bad reading of the surface?
This also brings me to question which surface, the carbonated one if your simply gluing to that or testing a scarified/shot blasted surface underneath the carbonated one.
Then the first picture where the tested registered a 6 did not even sand or grind the surface under the CaCl kit that I could see. And besides that, is it not impossible for concrete to be acidic?
Also, is it not prudent to swish the ph paper in the solution near the surface of the concrete to aid recieving a better reading. If your simply dipping the paper into a beaded up solution within one minute I really do not see how the solution is going to pick up or transfer the full amount of ions that the "vacuumed" surface has in it in sixty seconds unless it is grinded and the solution adsorbs into the concrete surface as it looks in Jason's video.
I also agree with you on the shoot blasting of every site, not gonna happen. Especially on a residential setting.
Stephen Perrera dba
Top Floor Installation Co.

Thank you for this forum and thanks to Ernesto, Ruben, & Evan for their comments and questions. I will try to answer questions raised by them with respect to the "pH" article I published in the March/April 2014 issue of Concrete Repair Bulletin of ICRI.

1. The article shows a photograph identifying pH of concrete as 6. That is a wrong pH of concrete measured using present ASTM F 710 method.

2. Evan mentioned that typically shot blasting is not used for floor preparation. He mentioned to me that the concrete surface is cleaned by grinding the surface using sand pads. The test method I proposed in the above paper uses 50 grit sand paper to mimic exactly the sand pad type grinding.

3. I have seen shot blasting used prior to many flooring installations in CA. However, it does not matter if shot blasting is used or sand pad grinding is used. Both the sand pads or shot blasting do the same thing. It exposes freshly ground concrete surface along with cement/cementitious dust. When this cement/cementitious dust mixes with the water from the water based flooring adhesive or subsequent accumulation of water under a non-breathable vinyl flooring, then it creates a high pH solution at the interface of concrete to adhesive. If the adhesive cannot tolerate high pH condition, then it is susceptible to adhesive failure.

4. Yes, sometimes grinding hard steel troweled surface is difficult and may need power tool to grind the surface just like the sand pad grinding mentioned by Evan. That is why I proposed a 50 grit sand paper and not a 100 grit lighter sand paper. I have no problem using power tool to grind the surface to collect the dust for testing as long as we do not grind the concrete surface too deep. Hand grinding using a 50 grit sand paper has much better control in the grinding process.

5. If the concrete surface is carbonated, so be it. We will measure a lower pH. The idea is to measure the "True" pH of concrete surface and not a false pH as it is often measured and reported using ASTM F 710.

If you wish you can contact me directly with any technical question at [email protected] or at (510) 581-2342 extn. 107. Thanks.

Ashok Kakade, P.E.
Concrete Science, Inc.

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