I am trying to avoid a special inspector for my pour. Does anyone snow someone who will specify a specific mix, including fly ash, that will help me avoid the costs of a person standing around all day just watching the pour? I suggested that my engineer specify a mix. I got the idea from another topic thread. Thanks

What does your ICF manufacturer/distributor recommend? Do they have written guidance regarding the concrete mix? Many ICF manuals contain recommendations for the concrete mix.

Lafarge concrete has a formula they use just for ICF

This is one of those questions that has a lot of "that depends..." in it.
In general, concrete walls require special inspection per building codes. Different regional code bodies may modify this requirement, or just decide not to enforce it. If the local building official requires special inspection, it will be required, and the concrete mix won't have anything to do with it. Special inspection is not really a function of concrete mixed design.

Then please note, that any given mix recipe will have different properties for different geographical areas. Sometimes even among different local concrete plants. Special inspection has basically everything to do with the placing process, not the finished product. So the design mix is very important there. Many factors affect the properties of the product going into the forms, such as type and size of aggregate, water/cement ratios, amount to fly ash, additives, etc.... So a "canned" Universal mix recipe will not be very meaningful.

Also, special inspection doesn't always mean constant observation. The engineer of record can often define the special inspection to include such things as rebar placement, spot check observation of placement, post-placement observation. Using a self consolidating mix can often smooth out the process. But if your design is totally prescriptive, and does not have an EOR or licensed architect overseeing it, you're likely at the mercy of the local building official.

I'm often amazed at the questions asked on this forum over the years. You purchased the forms from somebody, did you think of asking them what mix is used.

Thanks for the help. My question was genererated by another discussion on a forum. I do know what my Mfg. suggests but the other forum seemed to indicate that an engineered proven and "stamped" formula might save a costly inspection. I guess i'll just have to tollerate what ever level of oversight my local county building dept demands. thanks k52

If you have a county building department, then you have an adopted code.

Assuming residential, its going to be some variation of the IRC series of codes, probably the IRC2003.

There is a couple code sections for ICFs, read them and tell the BO that you will be using xyz in order to follow the code. That should make them happy.

I have never needed a special inspection for any residential ICF projects; SOME commercial may have special inspections required for facets of the job, concrete typically being one of them.

thanks K52

K52,

When we have used a mix design specified by the engineer of record, we have had to back that up with previous test data to prove that the mix design reached or exeeded the the engineer's required design strength. Messing around in the realm of mix design should only be done by a qualified and experienced contractor or ready mix personel. I have been doing this for a long time and there are many pitfalls you could endure going this route. Every region has different aggregates that have different dynamics in a concrete mix. Every region gets cement from different sources which can create huge diffrences in the dynamics of your mud. Some regions can easily get slag or fly ash some can't. Some ready mix plants use no admixtures in their concrete. Here is the big kicker, in my experience most ready mix plants don't employ a person with enough knowledge of concrete design to accurately design a mix with good data to support it. Just because they have been in business for 50 to 100 years does not mean they have educated themselves to the proper use of admixtures.

Jerry you are right on target. I am glad to see a PE participate and give good advice.

ICF Contractor

thanks again , K52