cracked arch and chimney

[josephl]

I rebuilt the arch for the second time and after using it for awhile it cracks and breaks loose and the chimney also cracks. I was thinking about reinforcing the arch with flat iron and bend it to the the shape of the arch to support it. Any other suggestions.

[Faith In Virginia]

I had the same problem. This web page will help you to understand forces on an arch

Auroville Earth Institute, training courses, workshops on Vaults, Arches, Domes(VAD), stabilized rammed earth walls, compressed earth blocks, vaulted structures, compressed stabilised earth blocks, rammed earth.

What I did to fix my issue is I built a form put about an 1-1/2inches of vermiculite portland cement mix on the arch itself then some re bar and then filled it with regular cement. I held back from the face of my firebrick so that I have room to put a stone facing. This concrete will also have extra support when I build the housing around the oven so right now it's just standing there.
Hope this helps

[david s]

Is your arch in direct contact with the inner parts of the oven or did you leave a small insulating space to isolate it? I believe that the temp. differential in the outer arch is a major cause of cracking problems. The insulating gap reduces both heat conduction to the outside and also reduces the temp differential between the inner and outer faces of the arch.
Dave

[Faith In Virginia]

I know I missed that on this oven...live and learn. So yes it is in direct contact.

[Tscarborough]

The main problem with that arch is excess outward thrust. It needs more mass to buttress the arch.

[josephl]

Yes the arch is in contact with the dome. The problem is that the outer part of the arch is cracking. I guess the weight of the chimmy is to much. I was going to put a quarter inch by one inch flat steel bar shaped to the arch to reinforce it. The sides of the arch wall are fine and they do not crack. Just the front part of the arch falls out. Any suggestions.

[josephl]

Any ideas for the arch how to redow it