When are cracks acceptable?

[Microheli]

I fired up my my brick Pizza oven for the 1st time last night. The oven has a a brick dome with a 2 inch coat of the correct cement. I noticed some exterior cracks two hours into the burn. The cracks were emiting steam like vapor. the interior has no cracks.

This morning I could notice the cracks had some kind of white calcium residue.

Is this normal?

Today after I started heating the oven, I noticed the oven entrance has some cracks along the brick cement joints.

I am worried, am I doing somthing wrong?

After 5 days of heating the oven I was plan to cover the exterior dome with insulation and later regular cement and some decorations.

Should I be doing somthing diffrent?

[brickie in oz]

Re: When are cracks acceptable?

Sounds like the oven is still wet, did you go through the curing process?

[cholme]

Re: When are cracks acceptable?

I assume when you say you fired it up, that you are either on the first low temp curing fires? Cracks will occur for a couple reasons. First, if the concrete dried to quickly after the initial pour. i.e. If the air temperature was such that the concrete dried before curing. It is recommended that you keep it moist for a week or so.

The second way to ensure cracks is to start too hot a fire too fast when there is still moisture in the concrete.

Hairline cracks are to be expected, but it you are getting smoke through some of them, you will probably want to patch those.

[Microheli]

Re: When are cracks acceptable?

The oven is currently in the curing process 2nd day 07/24/2011.

Today I found some hairline cracks in the arch; I am kind of worried that the arch might collapse. Thank you for you're feedback.

[cholme]

Re: When are cracks acceptable?

Not that it matters at this point, but did you soak the bricks before you mortared them? If your bricks were dry, they will leech out the water in the mortar and won't cure properly. I am not experienced enough to recommend a fix for this. Perhaps some of the Master Builders will chime in for you.

I do think you should address it, those look like more than hairline cracks to me.

[brickie in oz]

Re: When are cracks acceptable?

Not that it matters at this point, but did you soak the bricks before you mortared them? If your bricks were dry, they will leech out the water in the mortar and won't cure properly.

Not true actually.
As Ive stated many times, we lay bricks in 30+deg c with no ill effects to the mortar.

The cracks look as if the fire got too hot too quickly.
Plus the lack of buttressing for the arch wouldnt have helped, as the arch heated up is spread and tried to flatten out.

[Microheli]

Re: When are cracks acceptable?

I agree, the fire did get to hot and to quickly in the arch area. Is there anything I can do? Can I just leave it like that? Is there a thin compound that could be poured in the cracked area? Is there a risk of the Chimney area falling?

[brickie in oz]

Re: When are cracks acceptable?

Is there a risk of the Chimney area falling?

Wider shot pics are needed to tell that.

If its not too bad you can dig out the mortar and bog it up again with a mortar slurry.

[cholme]

Re: When are cracks acceptable?

Not true actually.
As Ive stated many times, we lay bricks in 30+deg c with no ill effects to the mortar.

I stand corrected. I am not a brick mason... just going on what I have heard and read. The spreading makes sense. Is it too late to add a buttress to your arch support? Perhaps something made of angle iron if space is an issue.

[Johnny the oven man]

Re: When are cracks acceptable?

Arch-bricks would have been a better option, with less gap.
As it stands, those bricks appear to be able to just fall out, there is no "wedge" to hold them in place.

[brickie in oz]

Re: When are cracks acceptable?

I stand corrected.

Dont stress, if I had a dollar for every Furphy Ive heard about bricklaying I wouldnt have to keep working.

[brickie in oz]

Re: When are cracks acceptable?

Al,
Do you mean Furphie!!!

A Furphie about a Furphy, brilliant.