Blue concrete?

[Drsnuggels]

Wondering if anyone knows if it's blåbetong I have in the picture?

 

[M.sandström]

Likely, try drilling into it. It should go quite easily.

 

[Stefan N]

Looks more like slag plates.

 

[Isakare]

No, looks like so-called slaggplattor.

 

[Drsnuggels]

Have measured radon and it is low, but the ventilation is good here as well. If I drill, what should I discover then? Can anything be activated by drilling?

 

[M.sandström]

If there is no radon, you have no problem.
Drilling into blåbetong is easy; it contains a lot of air and is a porous material, so you can also easily drive a nail into it.