The first layer of epoxy that was laid on Day 1 is a Versatile 4195.  This epoxy is used for two reasons.  First, it has a vapor lock quality to it which helps fight any moisture that might try to push its way through the concrete.  Second, and very important, the epoxy is extremely slow drying which allows the coating time to sink deep into the concrete before hardening.  This deep penetration creates a good platform for the following multi layers of coatings.