vermiculite/concrete question Pompeii Oven Construction Discuss vermiculite/concrete question in the Pizza Oven Design and Installation forums; We took the forms off today, and there are places around the edges and in a couple of the corners ...

[briot]

We took the forms off today, and there are places around the edges and in a couple of the corners where the vermiculite and concrete look crumbly - as if it was not well compacted. Is this a bad sign?

[Neil2]

"Is this a bad sign?"

Not necessarily. Continue to keep it damp for the whole six days.

[Roadkyng]

Mine is the same way. I even had a few areas crumble out that I had to fill and level before starting my floor. The compressive strength is still there (can't really push down too far with my thumb) so it will support the weight just fine. My insulating layer is 8" thick. The biggest area that is crumbling out now is in front of the oven arch, what I call the 'landing'. I will probably cut out this area and re-pour concrete when my oven is done. Kinda like slicing a piece of cake and adding icing!

[briot]

Also, you can sweep a lot of loose vermiculite off the top. I'm worried about how uneven it may end up when all that stuff is swept away.

[Roadkyng]

Yep - mine is the same. I probably didn't add enough concrete mix to the vermiculite.

To set my floor I put a scratch coat of refractory mortar, then leveled it off. After it cured I put a layer of fireclay/water and set my floor bricks. I then mortared my soldiers to the scratch coat.

If you go with the FB board (CalSil) under your floor the small voids could be filled with dry fireclay

Originally Posted by briot

Also, you can sweep a lot of loose vermiculite off the top. I'm worried about how uneven it may end up when all that stuff is swept away.