ARXX specifies a slump not less than 5.0 and not more than 6.5.

I stand corrected. This is from the 2012 IRC:

"R404.1.2.3.4 Proportioning and slump of concrete.
Proportions of materials for concrete shall be established to provide workability and consistency to permit concrete to be worked readily into forms and around reinforcement under conditions of placement to be employed, without segregation or excessive bleeding. Slump of concrete placed in removable forms shall not exceed 6 inches (152 mm).

Exception: When approved, the slump is permitted to exceed 6 inches (152 mm) for concrete mixtures that are resistant to segregation, and are in accordance with the form manufacturer’s recommendations.

Slump of concrete placed in stay-in-place forms shall exceed 6 inches (152 mm). Slump of concrete shall be determined in accordance with ASTM C 143."

This is also listed in the 2012 code:

R404.1.2.3.5 Consolidation of concrete.
Concrete shall be consolidated by suitable means during placement and shall be worked around embedded items and reinforcement and into corners of forms. Where stay-in-place forms are used, concrete shall be consolidated by internal vibration.

Exception: When approved for concrete to be placed in stay-in-place forms, self-consolidating concrete mixtures with slumps equal to or greater than 8 inches (203 mm) that are specifically designed for placement without internal vibration need not be internally vibrated. "

I guess you should ask if the concrete is a self consolidating mix, or did they just thin it out to a high slump.

This website is a good resource:

http://publicecodes.citation.com/icod/irc/2012/index.htm?bu=IC-P-2012-000002&bu2=IC-P-2012-000019

Posted By jeepster on 08 Dec 2011 09:22 PM

Posted By Lbear on 08 Dec 2011 07:24 PM
Is using an 8" slump common practice with ICF pours?

I hope not.  That's a code violation.  I believe a 6" slump is the highest allowed slump.  How did they achieve an 8" slump?  Water or admix?  Lemme guess, no vibration . . .

They claim that the concrete plant mixes them the 8" slump. They do vibrate but they claimed they prefer 8" slumps.

Posted By jeepster on 08 Dec 2011 11:16 PM
I stand corrected. This is from the 2012 IRC:

Slump of concrete placed in stay-in-place forms shall exceed 6 inches (152 mm). Slump of concrete shall be determined in accordance with ASTM C 143."

This is also listed in the 2012 code:

R404.1.2.3.5 Consolidation of concrete.
Concrete shall be consolidated by suitable means during placement and shall be worked around embedded items and reinforcement and into corners of forms. Where stay-in-place forms are used, concrete shall be consolidated by internal vibration.

Exception: When approved for concrete to be placed in stay-in-place forms, self-consolidating concrete mixtures with slumps equal to or greater than 8 inches (203 mm) that are specifically designed for placement without internal vibration need not be internally vibrated. "

I guess you should ask if the concrete is a self consolidating mix, or did they just thin it out to a high slump.

This website is a good resource:

http://publicecodes.citation.com/icod/irc/2012/index.htm?bu=IC-P-2012-000002&bu2=IC-P-2012-000019

Interesting. Stay in place forms (ICF) require that the slump be GREATER than 6" and that INTERNAL VIBRATION methods be employed except if they use 8"+ slumps.

This tells me that INTERNAL VIBRATION is becoming the standard for ICF and that 6"+ slumps are also the standard for ICFs. I bet these new codes are because of the problems with VOIDS.

This is quite a lot of discussion to spend on voids, which can be avoided by using some very basic guidelines and by not sleeping when you pour. Don't re-invent the wheel. Make sure you at least see a couple of pours before you run your own.

How many ICF projects are actually damaged by voids?

And, if you do get one, the chances are that it is going to be very minor and easily repairable.

Posted By Lbear on 09 Dec 2011 05:02 AM

...I bet these new codes are because of the problems with VOIDS.

Where have you seen problems with voids?  I'm talking real world problems, not those created in a lab under specious pretenses.  I mean, using a palm sander to vibrate an ICF wall?  Or a reciprocating saw with a bent blade on the end?  Who would even seriously consider those tools because they impart little if any vibration into the wall?

This thread is starting to sound like the "What is the best oil to use" thread in a motorcycle forum that I frequent.

Arkie6, you would be astonished at some of the crazy stuff we see "experienced installers" try to do. No matter how experienced the installer claims to be, we always have technical advisers on site for their first Polycrete install.Orbital sanders? Yep. Reciprocating saws? All the time! Banging with 2x4's? Yup, that too. And of course the guys who say. "We never vibrate because it blows out the forms. Our pump operator told us never to vibrate ICFs, so we don't"

These are guys who started out as stick-built house builders and figured if the ICF industry markets to DIY-ers then an accomplished house builder could do it too. But they never took the time to get properly trained, or they took an intro course at the local Holiday Inn on a Saturday and figured they had enough info to get going. Actually, they had only enough to be dangerous.

You never want to market to the lowest common denominator.

It's a losing proposition.

Posted By ICFHybrid on 09 Dec 2011 10:12 AM
You never want to market to the lowest common denominator.

It's a losing proposition.

Sam Walton would probably disagree with that.

Alan,

I agree with you.  Sam Walton never under estimated the customer's desire to buy cheap.  Why else is everything made in China?

That was an admittedly broad statement, but, to be fair, we are talking about contractors performing here, not selling retail goods. You will always have someone at the bottom who can't follow commonsense guidelines with any product, not to mention stated specifications.

Posted By BrucePolycrete on 09 Dec 2011 10:02 AM
Arkie6, you would be astonished at some of the crazy stuff we see "experienced installers" try to do. No matter how experienced the installer claims to be, we always have technical advisers on site for their first Polycrete install.Orbital sanders? Yep. Reciprocating saws? All the time! Banging with 2x4's? Yup, that too. And of course the guys who say. "We never vibrate because it blows out the forms. Our pump operator told us never to vibrate ICFs, so we don't"

I have watched concrete being placed in many walls formed with either ICF or aluminum forms without any type of vibration.   I have seen 3000 PSI concrete watered down with added water at the site to the point where it flowed like water from one end of a form to the other.  I have heard the concrete contractor tell the ready-mix truck driver add water to the mix and don't stop until he told him to stop without any regard to how many gallons were added.  I have seen contractors place uncompacted dirt back into a footer trench when the trench was dug too deep in certain areas.

And yes, I have seen many cracks in basement walls resulting from a weak mix and lack of proper rebar placement.  These jobs were not my projects and I could not say anything.  This taught me to supply the specs for my projects and then supervise the installation.

Poor concrete practices and the use of concrete block for basement walls has convinced some people that basements will leak.

That's why ICFs are getting so popular - the foam covers up a lot of corner cutting :-). Does anybody not on commercial projects test the concrete after cure?

Posted By jonr on 09 Dec 2011 03:31 PM
That's why ICFs are getting so popular - the foam covers up a lot of corner cutting. Does anybody not on commercial projects test the concrete after cure?

That is one of the biggest fears/hurdles to overcome if choosing ICF over wood. With a wood frame construction, what you see is what you get. With ICF, it's anyone's guess what is actually sandwiched in-between that EPS.

For residential, I don't believe they test the concrete after cure. For commercial, yes, but not residential.

I suppose you can get a contract like that - if there are voids or the concrete doesn't test out, they get to do it over. Or if the walls aren't straight and level.

I don't see voids as a big issue, voids are easily prevented and if a mistake is made a void can be filled. The only time in all our pours that there was a problem was when the ready mix truck's water lines froze on the way to the job and we could not add water to get it beyond a 4" slump. We had to fill voids along side a couple doors that all the vibrating in the world would not fill.

add water

I thought that the recommendation was to not do that and use a super plasticiser. But OK if concrete was delivered with excess strength and would still meet specs when watered down.

I will bring concrete to a 5.5" slump with water, design strength at that should not be compromised. always a minimum of 4,000 psi.

Posted By jonr on 09 Dec 2011 10:22 PM

add water

I though that the recommendation was to not do that and use a super plasticiser. But OK if concrete was delivered with excess strength and would still meet specs when watered down.

I could be wrong but I've gotten the impression that trucks often leave the plant with dry mix or under watered mix, and then add water at the site up to the mix ratio that was ordered.