Yes, Rust Bullet Concrete coatings may be applied to unsealed concrete after the concrete has fully cured. If a fresh pour is done with the intent to coat with Rust Bullet, you want a rough or broom finish. Do not have the floor power troweled and do not use a sealer. It is also recommended to perform a moisture test to ensure the concrete is completely dry throughout prior to application and follow all provided guidelines.
To perform a moisture test, take a piece of plastic (one side cut off a gallon resealable bag works great) and tape it to the floor on all edges, making sure its sealed on all sides. Wait 24 hours and inspect to see if there is condensation or darkening of the concrete in this spot. If there is a darkening or condensation, this indicates moisture is still present and the concrete is not ready to coat. Do this in a few places, going from the outside edges to middle of the floor to ensure it is dry throughout.