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threedi 05-28-2009 10:07 AM

Small cracks in mortar.
I am firing my oven and going through the curing process. I have started to notice small cracks appearing in the mortar on the front arch of the oven. Should I worry about this (figure that the oven may have got too hot too quick). I have filled the cracks with more mortar but am a bit concerned. The mortar seems to have cracked on the inside of the oven also.
Any help would be great.

dmun 05-28-2009 12:06 PM

Re: Small cracks in mortar.
Someone, years ago, entitled a post "enough with the cracks already". I know it's distressing, my oven cracked too, and I wasn't happy about it, but it's really common.

We can tell you more if you tell us what kind of brick, and mortar you're using.

threedi 05-28-2009 12:52 PM

Re: Small cracks in mortar.
2 Attachment(s)
Thanks dmun.

I have attached some images of the oven as it is so far. Hopefully you can see the state of the cracks in the photo. I wasn't sure if I was being over worried (seems that I was).
The mortar is called WASC (wet air set cement) and thats all I know about it, I got it from a company called Handsworth refractories here in the UK, they use it for gluing firebricks together in foundry's, the guy said that it would keep a container of 300 tonnes of molten steel held together and for me not to worry.
I have also had some steam escaping from very fine cracks on the dome and wondered if this was OK too.

Thanks for the help.

Jochen 06-05-2009 04:24 PM

Re: Small cracks in mortar.
I have used the same supplier in the UK and also bought the air drying mortar. I didnít get on with the stuff at all. Mainly because it doesnít seem to "stick" to the bricks very well and takes a long time to dry. I used it mainly to fill in large gabs at the outside of the dome build. I used a fire clay/sand/cement mixture instead.

I have a crack in the mortar at the front arch which widens when the oven is really hot but after reading lots of comment in the forum about cracks this seems to be quite normal.

I would recommend to use your own mixture with fire clay. This has worked well for me.

dmun 06-05-2009 04:36 PM

Re: Small cracks in mortar.
We've had bad reports about pre-mix mortars in this country, about strength and rigid setting and lack of water resistance. I sure wouldn't want to be any where near a container of molten steel held together with this stuff. I suspect they are designed for applications where they are immediately brought to higher temperatures than we use in a WFO.

That said, your cracks don't look so bad. I got similar cracks using a standard dry firebrick mortar mix.

Neil2 06-05-2009 06:33 PM

Re: Small cracks in mortar.
The whole system is essentially a gravity structure with all elements acting in compression. I wouldn't worry about the cracks (unless bricks start to fall on your pizza).

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