Looking for best material to fix refractory cement dome

[capamando]

Hi,
My refractory cement dome has quite a few cracks that I have tried to fix before with no real success. They eventually fall off. I can live with the cracks but there are a few spots where there is missing chunks of refractory cement. What would you recommend to slow down those few spots that are missing refractory cement. So far, I have not found any product that sticks to the dome permanently.

[david s]

Filling cracks is rarely successful, but this method is as good as can be obtained. Wet the crack or void well. You may have to paint it with water and a brush repeatedly. Make up a thin slurry of finely sieved mortar to remove all the aggregate and paint this on the surface of the crack to be filled. Then force some mortar made up to peanut butter consistency into the crack. Try to keep the area damp for around 12 hrs. A wet rag propped up with a stick works ok for this if the crack is in the dome.
Then allow a week to dry before firing.
Keep fingers crossed that it will work. Remember that there are two types of oven owners, those that have cracks and those who lie about their ovens having no cracks.

[capamando]

Thank you David,

One question... when you suggest using a sieved mortar are you referring to a refractory cement mix that can withstand high temps?

[david s]

Same, if using homebrew or a calcium aluminate based product. You should use the same material that the dome is made of. The idea is to get some of the cement to bond to the cracked surface so you don’t want the sand or fine aggregate for that step.

[capamando]

Thanks David,

I will share my results in the near future.

[BradC]

a few things that helped me repair my dome.
1. Clear area of loose debris
2. Add moisture to application area.
3. Mix cement to a workable “peanut butter” consistency
4. Add cement mixture to pastry bag for application onto dome.
5. Smooth or float with trowel
6. Float with area with damp sponge
7. Keep area moist to slow drying time. It’s my understanding the slower the drying time the stronger the material will be.
8. Cure the new cement applied. As your oven needed to be cured when new, so does this fresh cement applied.