can I do both Portland layers days apart?

[KEmerson]

Assuming I am going to do a vermiculite/Portland hearth insulation layer above the straight Portland structural layer, is it absolutely necessary to do both at the same pour, or same day? I imagine the only real reason for this would be for the concrete layers to adhere to one another better, but if the first (structural) layer is not smoothed, is roughed up, wouldn't that provide enough adhering strength? Can't I do both layers, say, a week apart provided the first layer is prepared in such a fashion? The concern has mostly to do with available finances as well as not deciding fully on what I'm doing about insulating.
Thanks,
Kim

[Lars]

Re: can I do both Portland layers days apart?

Kim,
You could do it the same day, or wait 10 years. Concrete will adhere to itself rather well, and it is not really necessary to adhere anyway. A lot of weight will be holding that layer in place for a long time.

Lars.

[KEmerson]

Re: can I do both Portland layers days apart?

Thanks. That's exactly what I thought. I appreciate the input.
Kim