Material in the subfloor panel?

[Kirtap66]

a WARNING is in order.... using plywood material in the trossbotten has made me 200,000 SEK poorer... Plywood, due to its sandwich construction, eventually becomes saturated with moisture between the glue layers and starts to mold... and it doesn't matter if it's mold-resistant or not...
Mold on a mold-resistant product just smells worse...
cellplast, or pure wood, or oil-treated masonite gets my vote... but in my case, the crawl space foundation was removed and I've now cast a slab inside the whole house of 38m2

I'm very curious about the casting of the crawl space foundation. I have the same plans. Do you need to reinforce externally for pressure? What I want to cast is about 8000×5500 but the surface is divided into four compartments.