Ampex

For a 3” concrete slab, including the volume between nubs, you would need 0.0135 cubic yards per square foot (0.0103 m3/sf) of concrete.

For a 4” concrete slab, including the volume between nubs, you would need 0.0166 cubic yards per square foot (0.0127 m3/sf) of concrete.

Refer the complete concrete volume calculator here.

No, you do not need a vapor barrier. The Ampex panel has been tested to ASTME96 and meets the requirements for a vapor retarder/ barrier. Refer the Ampex Panel Physical Properties Chart.