How to determine the moisture content of concrete

[lorand]

Hi there,

I'm just curious as to how to determine the moisture content of some concrete we've recently set. I was hoping I could just use an Ohm meter to, set the probes say 1cm apart and have some kind of table that corresponds to xxx resistance = xxx % moisture content.

Anyone have any ideas?

 

[Pyrrhus]

Yes it is possible to measure the moisture in concrete with such method, as long as you don't consider the results (quantitatively accurate) if you are measuring a structural element such as a slab, beam, ...

If you have the cores of the structural element, you could try a gravimetric approach which is more accurate.

 

[lorand]

Oh, this is only a small amount of self levelling concrete - in a room about 4m x 3m - and thickness of the self-levelling is ~11mm. Reason we need to figure out the moisture content is we are planning on laying down some bamboo flooring (with adhesive) and the documentation requires less than 5% moisture content for normal sealant application.

 

[Pyrrhus]

Electronic meters are usually not recommended to get an accurate reading, as i said above. I will recommend another procedure like Calcium Chloride test, you could look it up on the ASTM website.

However, I'm not sure about the emission rate such concrete sheet might have. I'll have to look into it, but have you tried a reading already?

 

[chemisttree]

I wouldn't believe the resistance readings anyway. Self levelling concrete has additives that might affect the conductivity. A good rough check can be made by taping some plastic visqene to the floor and let it sit overnight. ANY condensation on the underside of the plastic will cause problems with adhesion.

 

[realitybend]

Sorry to dig up an old thread, but I was browsing this forum and I can't stand to leave this question not completely answered. All the methods that have been talked about here can give an indication, but there's the whole qualitative vs. quantitative test issue. I think this article by industry expert Howard Kanare really addresses the issues more directly than I've seen anywhere else.

http://www.wwwagner.com/pdf/HK%20Problems%20with%20moisture%20Eprint.pdf

Good luck to all who run across this problem again!

 

[coltleader]

Hi there,

I'm just curious as to how to determine the moisture content of some concrete we've recently set. I was hoping I could just use an Ohm meter to, set the probes say 1cm apart and have some kind of table that corresponds to xxx resistance = xxx % moisture content.

Anyone have any ideas?

I just joined this forum and it's so weird that I just came across this thread because I have a similar question! I'm interested in finding out how much moisture is going through a concrete floor attached to my house. Does anyone know where I can get a test? I did a little research and discovered a place that has a calcium chloride test but I would like a review if anyone has used it, and also I would like to know how to use it!
Thanks so much!