Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Kapow! Low RH by Sundt
05-10-2013, 10:26 AM
Post: #11
RE: Kapow! Low RH by Sundt
I know the cement content is low because it's only a 4,000 psi mix. Wink

JD Grafton
Concrete Answers for Flooring Problems
[email protected]
Find all posts by this user
Quote this message in a reply
05-24-2013, 09:41 AM
Post: #12
RE: Kapow! Low RH by Sundt
Just a couple of comments because I just happened to receive some specs for another job. You have to commend the specifier/GC for keeping the W/C ratio down. I'm looking at a spec right now, with water reducer, that is still calling out a 6"+-1" slump and an estimate of .54 W/C ratio. Sound like the GC also did a great job protecting the slab from rewetting.
Find all posts by this user
Quote this message in a reply
05-24-2013, 09:48 AM
Post: #13
RE: Kapow! Low RH by Sundt
Jason - can you tell us a little more about that spec? Is the slab low RH? Because 0.54 seems high to me, and isn't that little a slump unworkable? I've always been told that to 'specify' a slump is in no way related to moisture results. Heck you can use Lafarge Agila (~100% slump) and still get the same drying characteristics of other concrete.
Find all posts by this user
Quote this message in a reply
05-24-2013, 10:09 AM
Post: #14
RE: Kapow! Low RH by Sundt
EA:

The spec I am looking at has not been tested yet so I can't answer the RH question. As far as the slump and moisture results directly, I would have to agree with you. Indirectly though a higher W/C ratio will slump more that a lower W/C ratio. Typically the concrete manufacturer is the one who provides this slump information once the materials and proportions of the the mix design are calculated. This would be a QC measurement for someone on site. So in my pea brain, the more it slumps the more water in the design, the longer it will take me to dry the slab of that excess.

Jason
Find all posts by this user
Quote this message in a reply
05-24-2013, 10:16 AM
Post: #15
RE: Kapow! Low RH by Sundt
Things like Agila are superplasticizers. So yes I agree with that caveat.

Slump as a Q/C is only good as Q/C for batch plant to site. It shouldn't be relied upon for performance.
Find all posts by this user
Quote this message in a reply
05-27-2013, 10:17 AM
Post: #16
RE: Kapow! Low RH by Sundt
(05-24-2013 09:48 AM)eaadams Wrote:  Jason - can you tell us a little more about that spec? Is the slab low RH? Because 0.54 seems high to me, and isn't that little a slump unworkable? I've always been told that to 'specify' a slump is in no way related to moisture results. Heck you can use Lafarge Agila (~100% slump) and still get the same drying characteristics of other concrete.

Slump is how much a column of concrete sags when the casting mold is removed. A 6" slump is quite soupy, and would be very easy to work. Flat concrete is usually spec'd at a 4" slump, but by using water reducers contractors can use only the water required for a 3" slump and still get the consistency of a 5" slump.

Water reducers make the concrete slippery, allowing it to consolidate and flow more readily. These products dissipate rapidly and don't add excess water to the mix.

JD Grafton
Concrete Answers for Flooring Problems
[email protected]
Find all posts by this user
Quote this message in a reply
Post Reply 


[-]
Share/Bookmark (Show All)
Facebook Twitter Linkedin Technorati Digg MySpace Delicious