Yes, all concrete can crack, especially lifting sunken slabs up into place. When the concrete sinks, it will get a stress crack on the bottom, but will not necessarily be visible. When the slab is then raised, the pressure will release and the crack will show on the top. These cracks are not caused by the Slab Jacking but are just made more apparent when raised. There can be cases where Slab Jacking will crack the concrete, if the correct process is not used.