Create sidewalk and parking lot from concrete

I can't reach the 10 cm thickness. Max. 7 cm is possible because 50 percent of the path's substrate is concrete, as there is a basement room underneath. Do I have to install expansion joints at certain intervals? Can I actually mix "simple" concrete myself here, or does it have to be special WU concrete to prevent moisture from passing through, since, as mentioned, 50 percent of it is basemented? Do I have to treat the surface afterwards to protect it permanently and to prevent efflorescence? Unfortunately, I can't find anything about this on the internet.

Just a different question. What does your [Bebauungsplan] say about concrete? Very often, parking spaces and paths have to be made from permeable materials.

For exposed concrete, the magic word is "frost de-icing salt resistant". Otherwise, the surface will deteriorate over time in winter. And joints are also maintenance-intensive. 7 cm thickness won't do. And reinforcement won't help either, minimum cover. You should look towards concrete slabs, as you initially intended.

What does the structural analysis of the basement ceiling say?

I haven't really dealt with the statics of the basement ceiling. I wasn't very worried that something would happen. Mh, if there will be problems at 7cm, I wonder how manufacturers manage to produce panels in large dimensions with a thickness of 4cm, which then also hold up. I thought it would work without any problems. And without reinforcement? There is no steel in panels from the hardware store/specialist trade either.

Panels from the hardware store are prefabricated parts made with very high-quality concrete, which is practically produced under laboratory conditions. For example, you could never produce the [Filigrandecke] like this on a construction site. Can't you "move upwards" to increase the thickness? A normal gravel bed is 3-5 cm. That doesn't leave much thickness for the panels. I wouldn't put a car on it...