Concrete-slab floor on grade, surface delamination

[m1208]

I have a one-story building with concrete-slab floor on grade, with carpet flooring. The slab is approximately 40-years old. Recently one corner of the concrete-slab floor (by the exterior walls) shows sign of surface delamination/flaking. Any idea what may cause that after 40-years.

 

[hokie66]

Looks to me like levelling compound which has delaminated.

 

[Tomfh]

Looks like surface delamination:

https://alconcrete.org/wp-content/downloads/cip/20p.pdf

Could be topping compound too like hokie said.

It’s unlikely to have just happened.