I'd like to know if it is somehow possible to include Concrete in a blueprint. When I select an area with my blueprint, the ground is ignored. Do i need to hold a special key, or is it just not possible (yet)?
Yes, you need to concrete some empty piece of land (with no buildings on it) and then blueprint it. Next use it as a regular blueprint (even under already built factories et al)
You need to ghost the concrete. Then they will be included.
In 0.13 You can have blueprint containing both terrain and machines, you can just select whether you want to include only terrain, machines or both by the checkboxes.