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Posted by Rob Dykeman on March 26th, 1998 06:59 PM
In reply to Foam Form (ICF) by Mark K. on March 26th, 1998 04:04 PM [Go to top of thread]

I have been using foam forms (ICF's) for about 6 years.
I have also made it my "business" to know and find out how foam forms function.
This site will be devoted to ICF's and how they relate to other products in the building industry.
Myself and Pieter Vanderwerf are putting this together.
Pieter is the person who has written the books for the Portland Cement Association on ICF's.
The site will be online within a couple of months.
Till then you are welcome to throw your questions directly at me and I'll answer them the best I can.
The issue of cracking:
Concrete poured into foam forms,like any concrete, is subject to cracking. It probably won't for a couple of reasons.
We are all aware of cracks in poured concrete foundations, we all have seen them a one time or another. These cracks are here usually because the concrete was not cured properly before there was backfill placed agianst the wall.
A concrete contractor pours foundation, finishes pouring that foundation at 6PM. The following morning at 6AM his crew is there stripping that foundation so they can get to the next job.
During the day it reachs 95 degrees and is very dry out. The concrete wall stops curing. If the mix design was 3000lbs psi it probably will only obtain about half of that strength. Lateral strength is directly related to compressive strength.
It is about 1/3. The wall is not strong enough to hold up to the fluid wieght of the soils bacfilling it, the concrete cracks.
In an ICF foundation the concrete is always encapsulated in the foam it will, for the life of the wall, always be gaining strength. If I poured a mix design of 3000lbs in 180 days should gain about 4000lbs, or a1/3 more than my design.
1/3 of that number is much stronger than the poured wall. This does noy eliminate cracks, but it helps.
Also i usually pump the concrete so I can place the concrete at a proper slump rather than adding water to the mix to make it flow. The amount of water in the mix is critical in the quality of the end product.
So reasons why these walls are less likely to crack:
Proper mix design
proper curing
I use re-bar
Hope this answers some questions any more let me know
Rob Dykeman

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