Fire clay mixed with mortar

[korybodily]

Can I simply mix fireclay with premixed mason's mortar to use in the dome construction, or do I need to mix each component separately (ie as spelled out in the pompeii oven plans)?

[NoHa_abeetz]

Now don't quote me on this, but this is what my father did when building his oven. I'm in the process of building my own at my house. When discussing materials with him, he took a standard type s mix and added in the dust from cutting the bricks. Not sure if he was consistent in batching it, but for what it's worth his oven was built in 09 and has had no issues or deterioration. It is my intent to do something similar.

[Gulf]

Here is my 2 cents from an earlier thread on the subject. Homebrew question...

Sorry for the late reply. I'm glad that you found the hydrated lime. In answer to your op: In most cases the answer is no. Type-N masonry cement can't always be substituted for the Porland cement and lime. Although, the original recipe for Type-N masonry cement is 50% Portland and 50% hydrated lime, the manufacturers are allowed to substitute the lime with "the equivalent". That usually means some lime, some crushed limestone, and other proprietary additives. There are still a few small companies that make it from the original recipe but, very few. The old brick layers that preferred it (due to it's workability) have about all died out. The current generation of brick layers prefer the altered recipe because it is much less corrosive to the skin.

When I was a young brick layer's helper for my uncle, we would sometimes use premixed Type-N and at other times make it from scratch. I did not fully understand it at the time. Along with other brick jobs, we built fireplace boxes and brick BBQ's. We would sometimes go back and do repairs on old fireboxes. That usually meant just repointing the joints on a 30 year old fire box. The mortar would erode over time, but the firebrick would generally be in good shape. A 30 year old firebox today that was layed with the modern mortar will have substantial brick damage. Imo, the crushed limestone will swell when heated causing the faces to pop off the firebrick

When I first joined the forum, I would have told you that you could use any Type-N masonry cement to replace the Portland/Lime parts of the "home brew". Then, Tscarborough schooled me on modern masonry mortars.So, here I am, passing on the information that I have learned on the forum. I wanted to reply to this just in case someone else researches this question.