I used clear packing tape for my pour, it worked very well. It only split in one or two places. The concrete icecubes this created popped right out, and I had it all stripped off in about the same ammount of time it took me to apply it... This was 2" Duck brand tape from the Wallmart

, with two strips applied, overlapping in the middle across the top of the ICF interlocking teeth which probably made it a little stronger across the top... Same tape i used to hold the foam bucks in place while the foam gliue cured...