It looks like a flaw in the design. Concrete expands and contracts, you can't stop it so the design needs to take this into consideration. I would get the crack as clean and dry as possible and seal it with a flexible sealant. The width of the crack means the concrete contracted but the top edges of the crack are chipped off indicating that at times the concrete expanded and closed the crack. If the concrete wants to move, it will, that's why you need a flexible joint there. If you cut out and replace the damaged area with concrete without a flexible joint you will find that the crack will just reappear, maybe somewhere else but it will reappear.
