[ckissick]

So the concrete is splitting apart? That's different.

A possibility is that the concrete may be deteriorating due to a process called alkali-silica reaction. This is when alkaline soil (limestone is very alkaline) attacks the silica in the aggregate of the concrete. Aggregate that is rich in microcrystalline quartz is prone to this. This process makes the concrete expand and spall, or split apart, as you describe.

A way to check for it is to get a core sample of the concrete and make thin sections to look at the silica with a petrographic microscope.

The only solution is to replace the concrete. As we say in the scientific community, this is not a trivial task.

Not having seen it first hand, I could be wrong. But if this were a test question on an exam, I'd probably get full marks for my answer.