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Posted by Admin (188.8.131.52) on October 06, 2004 at 10:39:50:
In Reply to: Mortar posted by Claude on November 01, 2003 at 16:02:35:
Two more refractory mortar recipes: 1.* If your construction structurally allows you to join firebricks by having them supported under, the best refractory mortar to use would be 50% sand and 50% fireclay. This would be the best option if setting time or structural design won't matter to your application, it's the traditional refractory being also suggested by manufacturers of refractory products, just ask. Firebricks are also made out of clay, and are in manufacturing process fired/stabilized in industrial kilns. Standard 26% alumina content firebricks are meant to work and withstand in 1320 degrees Celsius continuous use. Such temperature is not being reached in wood fired ovens.
2. * Above mentioned mortar is very good, but it will set/dry slowly so you need to hold mainly top dome firebricks up secured in the position for some time, so they won't slid down. You can also add cement to speed up mortar setting. You can use also Portland cement to achieve this but that's only for the reason to be able to work slightly quicker. Portland cement is already a bit refractory but on it's own it is not wise to rely on as it will burn out. Replace half of the cement content with lime, lime is in fact a calcium and takes over this cement in hot cooking conditions. You still need to add fireclay in as well but here is no need to use a calcium aluminate cement:
Sand (brickies loam - has mud in it already), Fireclay, Portland cement, Lime - Parts ratio 10 : 6 : 2 : 3
3. * If you have any difficulty with where to buy refractory materials in your area don't worry. This is very common question emailed to us. The wood fired oven building CD (workshop- heaps of people prize it a bunch) has new addition in a CD log on request, it's a folder with "Equivalent refractory materials and their sources" (fire clays, refractory mortars, heat insulation's, firebricks) suitable substitutes, locating and work with them. This also includes plus 'in Dome photographs' folder of fires and meals from the wood burning oven.
Recipe mentioned in the message ahead: A mix of sand, cement /Calcium Aluminate cement/ and a fire clay in the ratio of 10x3x1.5 is a good recipe apparently used in bread builders.
Rado is at home with a bad flue but getting better, thank you.
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