Concrete stone - fireproof?

[Arlamannen]

I've hauled home 25m2 of concrete stone, like "byasten" but I'm not really sure what to do with them.

Is concrete fireproof or will the stones crack after a while if I use them to build a bake oven/grill/fireplace...?

What kind of mortar should be used? Refractory mortar is hardly an option considering the cost. :O

I have lime, cement, and sand at home... also have some good clay a little way down in the ground.

 

[anaitis]

Not completely fireproof.

 

[Arlamannen]

Suspected it...

Keen to try it anyway, if the damn thing breaks, it breaks. I'll try to build with clay mortar so I can take it apart and build something else with the stones.