Alternatively, some people use a lighter structural polyurethane in an effort to backfill a crack, not at all understanding that when that crack widens, the rigid stuffing in it will not withstand the movement, and you simply get more open cracks, but now they have garbage in them.
A company came up with an idea to install a carbon fiber strip of wafer-board over the crack before injecting it with epoxy. If the first idea didn’t work, they figured adding something else over the crack might. Sometimes you hear it called kevlar. It sounds impressive, as that’s the name of the stuff the military wears in their vests, and in vests, or on car bumpers – the stuff works pretty well. However, these wafer-boards aren’t really kevlar, and trying to keep 2 tons of concrete from shifting a half inch isn’t going to happen with wafer-boards and glue. The end result is detailed above with the epoxy failure. Wafer-boards snap, epoxy comes unglued and cracks continue to plague homeowners.
That same company has openly discussed that re-cracking is a common experience, occurring 6-24 inches away from the repair, along the same crack. They offer a third application of a spray on foam that will cover those cracks so you don’t see them, and their exact wording is, “It’s a different approach which we think is very promising. It makes an expensive cure less expensive and stronger.”