Has anyone seen any long term data on the rusting of rebar inside icf concrete. Would we be likely to see any moisture moving through the concrete. So far I have found a few solution to building an ICF that can last 100s of years. 1. Glass reinforced Rebar 2. Fly ash concrete - high alkaline content prevents rusting 3. stainless steel rebar (expensive) I would like to think an icf house could last a very long time. this would justify the use of concrete. So am I being overly worried about rusting rebar bursting the concrete and losing strength.

think you need to ask yourself what will cause corrosion
which must be water +oxygen usually
so well compacted concrete around rebar and concrete made with well washed sand --no salt content -
and rebar well buried in concrete .not near surface ,where some moisture could penetrate-
then you are worrying about nothing

Have you considered basalt rebar that does not rust?

If the rebar is properly placed in the concrete with at least 1.5" of concrete cover and the concrete is properly consolidated to eliminate voids, there is virtually no concern with corrosion of the rebar.

In short, your concerns are largely unfounded, just take a look at bridges. However, you could alleviate many of your concerns by adding a product such as Vapor Lock 20/20 to the concrete, which greatly decreases the ability of water/vapor to migrate through it.

You could also look at epoxy coated rebar. It should be cheaper than stainless steel, but not sure how it compares to glass/rock bar.

At the end of the day, I don't think this should be a concern, however. As mentioned, moisture should be minimal/non-existent in an ICF wall. Air is also required, which should also not be present in any sizable quantity.

There are zero issues with using normal steel rebar or helix micro rebar for typical ICF construction. The only time you need to use more exotic rebar is when the concrete structure will be immersed in water or will see salt treatments. There have been catastrophic failures of parking garages that were treated with salt to melt ice. Salt can get deep into the concrete and to the rebar via the control joints.

Epoxy coated rebar is very problematic because the epoxy coating is easily damaged during rebar placement and during the actual pour. Stainless steel rebar is very expensive and has a lower tensile strength than normal steel rebar.

We always use basalt rebar for our water work projects (e.g., cross flow turbine, fish screen by-pass tank, water wheels, etc). Basalt rebar is somewhat flexible like steel cable and this allows it to be used for more complicated shapes like cylindrical tanks, etc. Basalt rebar is also lighter in weight than normal steel rebar and has a higher tensile strength.