The Fresh Loaf

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Firebrick vs. Refractory Cement

MNBäcker's picture
MNBäcker

Firebrick vs. Refractory Cement

Firebrick vs. Refractory Cement...?

 

So, here's a question for all you experts out there: I just came back from my oven building class and started thinking about the following: when building the oven, one would definitely want to use firebrick for the hearth surface, but what about the inner dome? Is firebrick really necessary, or could the whole inner dome be constructed from refractory cement? I have heard about companies using large inflated tubes to build bridges, and I'm wondering if I could have a solid "dome" made from plastic, set it on top of my firebrick hearth and then pour refractory cement arond and over it to form the inner dome? Would the characteristics of the refractory cement be similar enough to the firebrick to make this product feasible? Or would there be concerns about cracking in the cement over time? So, inflate dome, pour 6 or so inches of cement around it, let harden, deflate dome and build chimney as usual?

Any input will be greatly appreciated.

 

Stephan

ClimbHi's picture
ClimbHi

One of the things that brick has going for it is it's natural ability to move with heating cycles due to the joints. Not so much with solid cement (well, technically concrete made with refractory cement). My construction experience has taught me that there are only two kinds of cement. 1) Cement that has cracked; and 2) Cement that is about to crack.

I also note that industrial furnaces for glass & ceramics are generally made of brick rather than solid.

That said, the kits that are available are generally made of castable refractory, (but again, they have joints built into the design) and mud ovens seem to work just fine. However, the straw in the mix may have something to do with that since it may allow it to expand/contract without breaking up.

Me, I wouldn't try -- but only because it's a lot of work & expense for something that's not proven. But if you do it, let us know how it works out! ;-)

ClimbHi
Pittsburgh, PA

polo's picture
polo

.......but there are several who have either built or purchased WFO's that were made from castable refractory. Forno Bravo sells several styles of pre-cast ovens, they battle the expansion problem by making the dome in sections. I'm sure that making the form and casting the dome would be challenging if you had never done that sort of thing before. I would try to find someone who has experience in using castable refractory to help guide you on your way.

A company called ANH would be the place to contact regarding the castable refractory material.

I would have to say though, that I am in agreement with Climbhi. We have several pusher style preheats where I work. While these preheats incorporate both brick work and castable refractory, it is the castable areas which need to be repaired most often.

sgregory's picture
sgregory

I guess you can cut every brick, but in reality, you can use straght brick on a form, breaking the joints between each row.  Back fill with a mortor and construct the next row if required by design.  Brtick is more forgiving but not required.

If you are worried about cracking and spalling with castable, use SS needles in the mix.  (watch the hands).  this will allow it to crack but maintain basic integrity during the heating and cooling cycles.  ANH is anker hearth or vietche radix,  which iirc is RHI.  hey merge and change names daily it seems.  In both cases you need to secure the base of the arch for its primary strength.