Guys,

What is the highest slump you all poured.  I really want to play with SCC in the next project.  Yes it is pricey (~120/yd) but may be worth it (consolidation worries).  RD134 from PCA says it can be done.  (Even the form pressures are not elevated - 90-100psf max).  What you all think????

Leonard

I have a hard time not believing form pressure doesn't elevate , with SCC at "Liquid Head"
Paper refuses no ink.

IMHO your formwork should be better prepared than normal for an SCC pour.
With ICF's, particularly the corners and bulkheads.

If you do experience a "blow out" the result will be very dramatic. LOL

Eric,

I thought the same. But RD 134 actually measured the pressures and they were also surprised that the results were coming in less than the predicted "liquid pressure" model. They attributed to friction, other forces. What's your highest slump they you are comfortable with???

Leonard

Just so you know the IRC states nothing over a 6" slump

Leonard : did the test include the use of vibrators ?
adding Super P to an already wet mix will create SCC type pour. That I have done a few times.
I try to stay in the normal slump ranges as much as practicable..but SCC will gain lots of ground in North America in the coming years.
On flatwork the labour saving is substantial.
Europe is much farther along in SCC acceptance by the Engineering Fraternity than it is here.

Eric,

As I read the article (http://www.icfmag.com/documents/PCA_Consolidation_Report.pdf), the SCC was not vibrated and is seemed to have the best results.

Bill...I was not aware that the IRC limited slump (I am using 2006, and I will check). Maybe related to weakening the mix with water??? But I am not sure.

Eric...I could not agree more...with experience SCC may be the standard for ICF and this I say from the simple point that if the forms can handle it and stay as braced then your pour will be trouble free. Imagine...no internal consolidation required...

Leonard

Leonard You will find the slump spec on page 194 of the 2006 IRC R611.6.1 it states,

Ready-mixed concrete for insulating concrete form walls shall be in accordance with Section R402.2.
Maximum slump shall not be greater than 6 inches (152mm) as determined in accordance with ASTM

I take that to mean regardless of mix design speced by the form manufacturer the slump must not exceed 6". That is the great part about most straight wall forms they do not need to be poured at much over a 4.5" -- 5.5" slump, I still like to spend the additional money and use SCC when ever possible as that with consolidation is my saftey factor.

Bill,

The latest PCA 100-2007 states that slump of 6 is max for removable forms and should exceed 6 for stay-in-place forms. Also they state that consolidation is not required if the slump exceeds 8. This book is available for download from the PCA bookstore.

Leonard

I've used 4 or 5 different icf's. I would have a hard time sleeping at night if I knew that I had to pour a 7" slump in a few of these forms. I've used a few forms that had all they could to to hold a 6" slump with a 3' lift. Isn't there a trade off with slump and strength? Sure you may not need to consolidate if you pour an 8" slump, but the concrete will be much weaker even though it is fully consolidated. If you had a standard 6" form with a standard amount of rebar, and you poured both a 6" and an 8" slump concrete without consolidating either, I believe the 6" wall would be a stronger wall. I think I'll go to the PCA bookstore and download the book mentioned above.


Bunt

Leonard That could be what the PCA states but the IRC which most of the inspectors will be dealing with won't allow any deviation with out engineering.

We have consistently poured our form with 5"- 5 1/2" slump with great results and top notch concrete compresive cylinder test, from time to time things come up requiring us to remove some of the foam and we have not wittnessed any voids. This may also be due to the consolidation and monitoring the loads to insure that we have used the correct yardage of concrete, excess concrete at the end of the pour would indicate there is a large void some where in our wall.

Bunt,

You make a good point about strength vs slump.  I do believe that modern concrete engineering (especially with a SCC mix) can yield what ever strength required.  I know I can spec a 3500psi mix, super-p added to create a mix of 8.  The issue of consolidation is critical as I think that this is the weak point of ICF construction.  PCA's RD134 addressed concrete mix designs and consolidation.  Ideally an SCC mix would be best.  But I am with you in that I would worry about the forms holding such a mix - but RD 134 states that it can be done.

Leonard

 

I always try to pour at a 5-5 1/2" slump 40000 psi peastone for 6" cavities. I always remove some foam randomnly to check consolidation. I have never found any issues. I poured a 4" slump once to try it in an 8" form. Vibrating obviously much more critical with 4" slump. This was a little 10 x 10  out house building, we consolidated two walls and didn't consolidate the other 2. The two which were not vibrated had much more honeycombing.

Bunt

Germans, as far as I was told from my frineds there, don't use the slump system anymore. They say it is outdated by over 20 years. They only pour SCC. They laughed at me when I mentioned the need for vibration in order to consolidate. I have contacts with an ISORAST installer in Germany. He only pours with the MAXIT system, again SCC. The rate of fill per square foot of wall is quite reduced - that would explain the ICF system to be able to withstand the fluid pressure. Set-up is probably quick as well, but not too quick - they are not worried about cold-joints either.

Manfred

Go ahead but bring a shovel! It will get to be a BIG mess!
Don't be afraid of the vibrate, it will be your Friend and give you good consolidation.
 A 4 1/2" to 5" max slump with 3/4 " crushed rock no super p or additives is what I have found works the best (for me)
 When you pull off the foam to check look at the cold joint.
 I have found more problems their and under double bar then any were else.
 If you don't think I am right then just try your scc and tap on the wall or what ever you think is needed for consolidated concrete.
  Now you stick a vibrator in and see the concrete drop 2" .
Were did that go?
The vibrator will only have a small area of influence and the raise in pressure for a short time.
 The block will handle it and if it dose crack or blow out it's still easer to fix than honey comb or voids. 
This is a thing you get the feel for after you do it a few years and can NOT just be picked up on the side from reading about it.
 Sorry all the diy out their I seen buildings that had to be taken down because of this. A LOT OF THEM.
 Do you need to see pic. ?

nine inch slump was specced on a commercial job, mud was brought in at a 4 and superP added on site.

a 16ft. pour six inch core completed in three lifts in 4 hours had two minor problems which wouldn't have occurred with a stiffer mix.

the next couple hundred yards went without a hitch in nine ft walls, 4 inch core, one lift.

six inch on center fixed form was used.

Hope this helps,
Kevin

Manfred,

The Europeans have always advanced building technologies.  Once we get some experience here and factor in the cost of SCC vs plunging a vibrator q12" I think SCC will win.  JMHO.

Leonard

We poured a wall today, the trucks came out with about a 4" slump, super P was added to bring slump to 5 1/2". The concrete flowed quite well and needed minimal effort to get good consolodation. We poured a couple of sample cylinders, I can let you guys know the results when I get them back, but bringing the slump up with super P made the pur really easy. We poured a 9' wall in two lifts, I plan on doing some minor invstigation after curing to see what we really ended up with.

Leonard,

this is for info purposes only: An SCC placed with high viscosity due to higher cement content flows better any day than a regular 3000PSI mix design. The mix design for an SCC in Europe is no less than 5000PSI or almost double the cement requirement for our current "minimum" designs. I don't want to challenge anybody with their placement techniques of current local practices. One has to deal with what one gets.
I think the question of whether an SCC design will be accepted here is based on the same mind set that comes into play when considering steel fiber vs. rebar placement. Rebar placement of current practice is inconsistent when compared to steel fibers especially when you consider just dropping in the verticals. But that is the accepted practice here - it is what it is.

Manfred

Manfred,

Would you elaborate on steel fiber vs. rebar placement?

Jeff

GreenOaks

Some concrete companies have a steel fiber which can be mixed into the concrete at the plant which some say will replace the use of 10m/#3 bar in the wall.
I have looked into it where I am, it would be a lot quicker building without bar, except for lintels and openings, but not many are doing it where I am, plus price on the fiber is quite a bit more per meter.