Refractory concrete Domes Vs. Firebrick Domes.

Posted by Admin (202.032.19.12) on November 15, 2004 at 16:25:40:

In Reply to: refractory concrete dome posted by Rob on November 15, 2004 at 06:23:18:

Hi Rob, below is just my point of views...
Best is to build wood oven dome out of firebricks. Look at brick dome as on structure constructed of many fragments, when this dome gets heated up it expands and then on cooling it shrinks again. Brick dome is resilient capable to absorbing movements because bricks are next to each other moving nicely. Therefore brick domes will not develop major cracks and won't peal down the road. These ovens can be built inside the house as well, are less costly and very efficient.

To make a good dome mould 3-4 and more casting tests will need to be done. Leave the dome to cure and water to dry out. First prefabricate test develops cracks after firing, these cracks show how to split the dome into larger sections and how these get arranged fitting together. Then another casting test using existing crack lines for casting in segments, test firings again to see the new dome behavior. Next round and maybe another one to come up with the best dome function. Wise would also be to use quality higher density castable if the dome is to last for a long time.

Look at rectangular ovens built by old masters out of firebricks ( chamotte bricks ) many decades ago, they continue to work very well still, these domes are perfect. There is a picture of 1955 bakery oven in this site's gallery, it's being fired daily for years '!' baking Swiss cakes and lovely breads at present. I has firebrick dome - 4m x 4m chamber internally. Professional bakers who use wood fired ovens only want rectangular/square floor dome shape ovens constructed out of firebricks and well insulated, who else could be more competent to ask about.

Standard Firebricks of 26% alumina content in the body are meant to withstand 1350deg.C continuous use, this temperature can not be reached in traditional ovens heated with wood fire, and also in the manufacturing process these bricks are being stabilized/fired in industrial kilns!
I have no too much experience with domes made of larger concrete blocks or delivered completed concrete domes. I am not sure how long these last under mild or heavier use, they are expensive. But I recognize if one wanted to experiment with cheaper version of refractory concrete mix then why not to give the experiment a go and have some fun.