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waynespizzaworld 10-05-2011 07:28 PM

suggestions for castable hearth
My partner and I are in the start up stages of putting together a plan for building a Casa 2G 100 with pre fabricated components like stand complete with roof and its structural hearth etc. We want to make as much of the finished oven in our fabricating facilities as possible and then deliver to our customers for final install.

The plan is to pour a castable hearth with re bar and or fibers or some sort to help with the strength of the hearth and also if possible to have a hearth that also can be light in weight . We would want this castable structural hearth to be something we can move around with a small crane with out it breaking. The idea is to have this hearth as a building pad for the cook dome, insulation, stucco etc just like a regular build but we would build this in our shop and then crane it to the pre fabricated stand either in our shop or on site depending on site conditions and how everything will come together the easiest. Even though this time its going to be a Casa G2100 it may be a build from scratch next time and we would want to use the same system with the component style structural hearth to add to other components as we go. Hope this all make sense.

My question is this.............Is there any light weight and yet strong (and of course cost effective) methods members can think off to make the kind of hearth I am describing.

Thank Wayne

david s 10-06-2011 01:04 AM

Re: suggestions for castable hearth
You really need the mass in the floor to hold heat. If it is light it can't store enough heat. Secondly if you add a light weight aggregate to reduce the weight you simply make the casting weaker. Also the larger the cast section the more likely it is to develop cracks. Experiment yourself, but you will find this to be true. If you are craning the section into place then surely the weight hardly matters. The standard reinforcing is stainless steel needles not rebar. The heat will accelerate any corrosive reaction.

sonomacast 10-06-2011 02:43 AM

Re: suggestions for castable hearth
If you use rebar in your cast it will expand and crack the concrete, my 1st oven was sat on a reinforced slab and the bottom of that slab actually exploded where the bar expandedso be warned....not a good idea at all

waynespizzaworld 10-06-2011 08:24 AM

Re: suggestions for castable hearth
Just to clear something up David you may have miss understood. The Castable hearth is not the cook floor. The insulation will stop this component from needing to be mass for me. Its only structural. But thanks for the tips.

HeidiL2011 10-06-2011 08:42 AM

Re: suggestions for castable hearth
Hi Wayne,

We think that you can do this with standard concrete and rebar. A 3 1/2" slab with a rebar grid set on 12" centers will carry the weight of the oven and a professionale crane operator would be able to lift and place the oven assembly with proper straps and other safety precautions. We have had assembled Toscana ovens moved and set in place with a crane -- which is a similar situation; an oven assembled in a workshop and move to its installation site.

Does anybody else have other ideas?


david s 10-06-2011 10:56 AM

Re: suggestions for castable hearth
Sorry Wayne, yes I did misunderstand you. I've been down this road too. I think the best you can do is to make a structural concrete slab as thin as you dare. Make it as strong as you can by containing sufficient reinforcement, getting the correct recipe measured by dry weight. Add the correct amount of water and super plasticizer, vibrate sufficiently to remove all the air from the mix once poured and finally seal the complete slab and keep continually wet for at least a week.My previous comments about lightweight aggregate still apply (they will make the slab weaker) you are better to make it strong with heavy aggregate,then reduce volume to reduce weight.

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