Home brew mortar crumbling

[Deanf]

hi all,

i have just finished Building a 36” oven, used red bricks and home brew mortar, after my fire few curing fires I have noticed a fair amount of the mortar crumbling from the inside i of the dome. Is this normal or am I in for a rebuild already? I used a mix of 6parts clay 3parts sand and 1 part Portland cement

[UtahBeehiver]

Where did you get the material ratios from? Typical home brew used on this forum is 3 sand, 1 fire clay, 1 lime, 1 portland. What I see from you mix is high clay ratio and no lime. It is also a chance when using red bricks, sometimes they work and sometime they don't. I know how expensive materials can be in the southern hemi so you work with what you can get but if the mortar is failing just after curing then it will not get better as you go on but the oven are mostly self supporting.

[Deanf]

Hi. The oven was built following a local article in “the shed” magazine. i Am wondering if the clay used had too higher concentration of silt.i will try to wire brush the inside to clean all loose material out and use a product like this https://www.bunnings.co.nz/cemix-lai...-5kg_p00706176