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Fireclay, Non-Refractory Mortar

An alternative to true refractory mortar is to make a non-refractory high-temperature mortar using a 3:1:1:1 mixture of fine mesh sand, Portland cement, fireclay and hydrated lime. While Portland cement starts to break down at temperatures as low as 400ºC (732ºF), temperatures that your pizza oven dome will experience every time it is fire, the fireclay and hydrated lime serve as binders, holding the material together over time.

You can use this fireclay mortar in place of true refractory mortar when building a brick oven. Keep the brick joints facing the inside of the oven tight, where the fireclay mortar is exposed to little direct heat and flame it will last forever. And it’s much, much more cost-effective than expensive commercial refractory mortar.

You can also use this fireclay mortar, in a pinch, to cast a pizza oven dome. It will definitely crack and not last forever, but it’s easy to work with, and you can use it with a sand or cardboard pizza oven mold to build a very low-cost oven.