Building a 32 mgal concrete tank. It will be filled with radioactive grout. The engineer of record requires us to test the slab for "flatness". The engineer states this test is only to determine the adequacy of the concrete cover since the floor will be covered with grout. I can't find any literature describing that this test gives any indication of concrete cover over rebar. No rebar is exposed.

Flatness measurements do not relate to rebar cover with the exception that a better flatness profile will generally yield more consistent cover; however, flatness tolerances are much tighter than placement tolerances, so there is no real correlation between the two.

A request for information (RFI) should be directed to the engineer of record, asking for clarification.