#Login Register
insuti testing
  • 0 Vote(s) - 0 Average


05-02-2013, 08:05 AM #21
eaadams Concrete Moisture Expert *****
Status: Offline Posts:592 Threads:85 Joined:Jul 2010
CC Magazine did a Concrete Curling Field Test.

In one store room they did a grid of many different finishes and they installed RH probes.

I can't find it online, it may have only been in the magazine, so I am going from memory that is a few years old. But, the result was marginal. There wasn't a statistically significant change in RH between different surface finishes.

However, I've heard this surface finish drying argument more and more. Our flooring manufacturer started saying it quite a bit. I worry because I do not think any studies have backed up the assertion. However, it is a nice one because it does put some of the 'why is the concrete still wet' blame back on the finisher.

http://www.concreteconstruction.net/on-the-job/cc-field-test.aspx

We have found in the past our contractors have hit slabs with an aggressive sanding disk or even a light beadblast and you can get CC test to drop quickly. However, I do not know about RH tests.

05-02-2013, 08:45 AM #22
CC Solutions Concrete Moisture Evangelist *******
Status: Offline Posts:1,065 Threads:69 Joined:Dec 2009
If the moisture is coming out of the concrete, the RH is going down.

Steel trowels seal concrete. That's what they do. That's why they are used.

Sealed concrete, either chemically sealed or mechanically sealed, will dry slower than porous concrete.

It works! Couple it with a 3 day wet cure and you have a great chance at having dry concrete when it's time to put the flooring down.

JD Grafton
Concrete Answers for Flooring Problems
JGrafton@ccsolves.com

05-02-2013, 08:59 AM #23
eaadams Concrete Moisture Expert *****
Status: Offline Posts:592 Threads:85 Joined:Jul 2010
Steel trowels also make concrete flat.

The difficulty to make that slab flat goes way up if they can't machine it flat. Requires a lot more attention by designer and many of them do not have the skills. The answer from the 'industry' is to use type k cement. But that increases material costs bu 25%.

05-02-2013, 09:02 AM #24
CC Solutions Concrete Moisture Evangelist *******
Status: Offline Posts:1,065 Threads:69 Joined:Dec 2009
All the final trowel does is seal the concrete. The consolidation is done with mags and combo blades. By the time the steel blades are put on you can walk on the concrete.

JD Grafton
Concrete Answers for Flooring Problems
JGrafton@ccsolves.com

05-02-2013, 10:21 AM #25
eaadams Concrete Moisture Expert *****
Status: Offline Posts:592 Threads:85 Joined:Jul 2010
So, consolidation creates flatness?

And the steel densifies the surface layer.

I learn something new every day. Love this forum!

05-02-2013, 11:25 AM #26
CC Solutions Concrete Moisture Evangelist *******
Status: Offline Posts:1,065 Threads:69 Joined:Dec 2009
(05-02-2013, 10:21 AM)eaadams Wrote:  So, consolidation creates flatness?

And the steel densifies the surface layer.

I learn something new every day. Love this forum!

Not exactly, but when concrete is poured it has voids in it and working the concrete works many of those voids out. While it is still plastic it can be moved around and shaped, including being 'flattened'.

Steel blades seal the surface and densify it. Much of this densification comes from the moisture being retained which then allows additional cement paste reaction.

JD Grafton
Concrete Answers for Flooring Problems
JGrafton@ccsolves.com

05-02-2013, 11:30 AM #27
eaadams Concrete Moisture Expert *****
Status: Offline Posts:592 Threads:85 Joined:Jul 2010
I thought the top dark steel layer typically has lower cement hydration due to the water being pushed out.

ref: http://www.concreteconstruction.net/concrete/unexpected-results.aspx

" The process of squeezing most of the water and air voids out of the top 1/8-inch layer causes other changes too. Portland cement that doesn't hydrate soon after the initial mixing process doesn't hydrate in this layer either (see Photo D). "

[Image: tmp20.tmp_tcm45-627527.jpg]
"In this scanning electron microscope X45 magnification of the profile top ¼ in. of the slab unhydrated portland cement particles appear as white dots and air voids appear as black dots."

05-02-2013, 12:31 PM #28
jim decker Concrete Moisture Enthusiast *
Status: Offline Posts:42 Threads:4 Joined:Nov 2011
Incredible as they say TMI can confuse you. Have to figure out a way to index all this info. WOW!








Possibly Related Threads...
Thread / Author Replies / Views Last Post
3 Replies 1,364 Views
Last Post by jim decker
07-13-2015, 02:51 PM
3 Replies 7,832 Views
Last Post by CC Solutions
09-01-2013, 09:10 AM
3 Replies 6,814 Views
Last Post by eaadams
06-28-2013, 10:26 AM
23 Replies 28,170 Views
Last Post by CCR
03-21-2013, 05:05 PM
23 Replies 47,275 Views
Last Post by CC Solutions
07-26-2012, 06:19 AM
6 Replies 11,320 Views
Last Post by CCR
07-12-2012, 01:44 PM
1 Replies 6,180 Views
Last Post by hnelson
06-07-2012, 01:08 PM

Users browsing this thread:
1 Guest(s)