A foundation crack shouldn't be fixed with any sealant, because the crack will most probably reopen or crumble down during the next movement in the soil or wall. Rigid sealants are band-aid solutions that don't fix the problem permanently.
The FlexiSpan Wall System is the solution. FlexiSpan is used to seal cracks while adapting to the wall movements over time. Because this sealant transforms into a rubber and waterproof material once it is injected in the crack, it will not crumble or crack anymore but will instead adapt to the movements of the soil or the wall that risk widening the crack. And because it is made of an inorganic waterproof material, it blocks water infiltrations and vapors which prevent its deterioration over time.
But if your crack is caused by a structural foundation issue, wall reinforcing systems such as CarbonArmor and PowerBrace will form a more appropriate solution that will fix the problem permanently by stabilizing your foundations once and for all.