Concrete floors are bound to crack over time. They cure, and then they settle, sometimes resulting in a cracked surface or slab.
Once a crack exists, it can be worsened by other routine activities and common events. Things like moisture seeping into the cracks, exposure to oils or chemicals that contaminate or corrode the floor, poor cleaning due to existing cracks, and vehicles driving over the cracked surfaces will all aggravate cracks in a concrete floor.
There are many reasons why concrete floors crack. The important thing is that when it happens, you know what you should and should not do.