Ph Of Concrete - Printable Version
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Ph Of Concrete - Ernesto - 02-16-2011 05:17 PM
Got a question foir you Guru's out there.
Can the ph of the concrete tell you more about MVER's than any moisture test?
RE: Ph Of Concrete - CC Solutions - 02-18-2011 10:46 AM
PH is a measure of alkalinity (or acidity, technically). We are concerned with alkalinity in the flooring biz because cement is naturally alkaline, and the glues we use can be broken down by excessive alkalinity.
MVER stands for Moisture Vapor Emission Rate. Specifically, we concern ourselves with measuring the amount of water vapor that is being released by the concrete that we are gluing our floor to. Excessive vapor transmission will affect the glue.
Ernesto (I think) is considering that as moisture moves up through a concrete slab it brings the highly alkaline compounds in the slab up to the surface with it. Carbon dioxide in the air reacts with the calcium hydroxide in the concrete and forms calcium carbonate. This process lowers the alkalinity of the carbonated concrete to about PH9.
It would make sense then that fresh green concrete would be both highly alkaline and have high moisture emissions. And as the concrete vapor emissions drop over time, and the concrete surface carbonates, the PH falls as well as the MVER.
Where we can prove this correlation doesn't fall on a nice graph we can use to tie these phenomenon together is in the case of a old carbonated and highly porous slab that allows sub-surface moisture to move through it quite readily, however the PH is extremely low. Another case is a quite dry slab poured on a retarder that we grind or abrade the surface carbonation off, exposing the more alkaline core, yet the concrete is emitting very low levels of vapor.
To further muddy the waters, concentration of CO2 in the air, concrete density, amount of pore water, age of concrete, and I'm sure other factors I'm not considering will come into play changing how PH and MVER relate in any given slab.
Excellent question, and I sure hope I didn't mess up my chemicals in my answer. I need to re-read this kind of stuff every year or I forget it quick!
RE: Ph Of Concrete - Ernesto - 02-18-2011 05:55 PM
Yes your assumption was correct. But please read Bob's Post over here:
RE: Ph Of Concrete - CC Solutions - 02-21-2011 03:37 PM
As I readily admit, Bob and I do not always see eye to eye.
To be honest, I read the link, and I didn't get a point out of the article, did you? He initially stated that without knowing PH, the moisture tests could be VERY confusing. But then he never explained why he states that. (You can remind him that RH tests are happening deep within the slab at PH levels in the 12-13 range ).
I don't know much about him, but a lot of what he says seems to fly in the face of ASTM's and many of the industry experts I follow.
I think what he really is trying to say in this article is: You may trust your CaCl moisture readings but still have a failure due to alkali breakdown of the adhesive.
Is that what you got? I mean he throws a bunch of numbers out there and scares us with CAPITAL LETTERS and says all the big organizations are teaching us improperly, but what is the reader's take away of the article?
RE: Ph Of Concrete - Ernesto - 02-22-2011 08:10 PM
LOL Try and talk to Bob on the phone. I say huh alot. Not sure about you but his experience is rather huge in the concrete arena. Heck, I don't even know your real name let alone your background info and experience. Much as I can tell you could be a IICRC carpet cleaner/concrete inspector. LOL
Just kidding with ya.
Seriously though, he scares me too. I pull 8's alot around here and it's dang scary after reading that article. If your slab is high rh does that mean its going to have high MVER's? Is there any correlation? Course not. And if you have high MVER's thats got to effect the ph does it not?
I might be able to go off on a tangent an throw some info out there off the top of my head like you did,,,well maybe not so good as you did. But when your out in the field, thats a whole different world than reading from a book. I am just so confused, so confused.
RE: Ph Of Concrete - CC Solutions - 02-23-2011 10:14 AM
LOL, don't feel like the Lone Ranger Stephen! We all get confused from time to time.
I just try to think things through, don't overcomplicate issues and follow the ASTM's to the letter. When things get fuzzy, I call in the manufacturers and get a written opinion. Try to keep players in the game. If everyone agrees that there is no vapor retarder under that slab, that the RH is correctly measured and reading 85%, but the manufacturer demands you follow MVER and the Owner believes the 2lb MVER reading an independent took, I say get the signatures and move forward.
You know a LOT about what can happen, why it can happen and how to spot potential failures. And one thing I have noticed is I can teach and teach and well preach and preach yet when it comes to installing a floor or paying for what some consider 'slaying the boogeyman' many owners will take the risk. In that case you can either walk away and wish them good luck or you can install under 'protest'.
You won't look like an idiot because you have reservations, but you sure would if there were a failure and you installed without pointing out the potential failure indicators beforehand. Don't believe this absolves you of liability though, as I have seen judges award money to owners because the flooring installer is the professional and should have known better and refused all work.
Me? I own a moisture mitigation company. We only deal with bad slabs, never the good ones! We always have to prove our value, always have to teach the parties involved and always have to justify our costs. And when those costs can reach $10/sf, people take notice!
RE: Ph Of Concrete - Ernesto - 02-23-2011 09:12 PM
I know what you mean about justifying costs. On every bid I write in moisture testing accroding to the manufacturers requirements. I win some, I lose some. I scare lots of them into doing the mositure testing too.
Some times I will even drop a few Rapid tests at my own cost if I am leary of the Cacl tests just to protect myself. Sure I could do the matt test cheaper, but will it hold up in court? LOL Don't laugh...I've seen it in a few manufacturers installation guidelines lately.
Speaking of matt tests, here is a stunning revelation I just witnessed over at the hardwood forum. All I can say is gosh. I think the guy is a building engineer and writes for the magazine there. He also teaches inspectors, craigdewitt.
Quote; "One test for concrete slab dryness is to lay a piece of plastic on the slab and see if you get water forming between the plastic and slab. Its a great, simple test. So why does water under plastic on a slab indicate a problem, but water under plastic on soil not indicate a similar problem?" End Quote
RE: Ph Of Concrete - CC Solutions - 02-24-2011 11:43 AM
I read that, he was troubleshooting a cupping wood floor installed over a crawl space. Some posters were saying there is no need to put plastic over the soil, and some even say it 'draws the water out of the soil'.
Kind of unbelievable how some people think.
RE: Ph Of Concrete - Ernesto - 02-24-2011 07:40 PM
Yea, pretty scary huh?
I see this kind of logic a lot from people who have only dealt with wood subfloors all their lives and now are attempting to somehow relate that science into concrete substrates. It just don't work that way.
RE: Ph Of Concrete - barry88rowe - 02-26-2011 12:10 AM
I have no idea why the pH in your influent water varies, I'd check environmental factors such as rainfall, temperature, and time of year for correlation.