Help! Refractory morter does not stick!?

[a.s.albuzilfah@gmail.com]

Hi all, new to this forum so not sure if i am writing in the right place or not.

i am building a 42” wood fired oven

PROBLEM: I noticed that my mortar is not sticking to the bricks. As in the bricks and mortar are separating and when the mortar is dry (after a week) it is brittle and i can crush it into a powder using my hands my hands.

the mortar cement i am using is Vesuvous Surebond 60DA (monolithic refractory)

as per package instructions i should keep the cement after mixing for 4 hours and then use it. I tried both ways using it immediately and after the 4 hour cure but i have the same issue.

Note:
i have +38% alumina refractory bricks that is soaked in water before applying.

[a.s.albuzilfah@gmail.com]

update:

I was frustrated by the lack of adhesion in the mortar even after 24 hours of mixing , the mortar was wet and broken in most parts and crumbling in the dry parts. so, I just added Portland cement to part of the mix to help with adhesion.

now I am using a 1:1 ratio which works in terms of sticking and hardening but have NO IDEA if it impacts insulation, heat resistance or thermal properties.

still need some guidance and support if anyone can help or share experience.

thanks guys.

[SableSprings]

Sorry not to have responded earlier, first...welcome to the forum! The problem you are having is primarily due to the refractory material. Refractory compounds are designed for withstanding high temperatures when used for casting...not adhesion. If you built a mold for a dome and used this material to cast it (best in sections to allow expansion/contraction), it would work great...but not to mortar bricks together.

Highly recommend you use the home brew mortar successfully used in most of the builds here. It's a mix of sand, lime, fire clay, & Portland cement (3:1:1:1), giving you good adhesion and strength. Be aware that the lime is not agricultural lime, but builders lime...two very different materials. I suspect you've already seen all this while reading through various threads in the Newbie section (especially the extremely useful thread, Hidden treasures...the top sticky thread in that section). Hope that helps or that you've already solved this issue.