UK oven build - help with fire cement

[brickie in oz]

Re: UK oven build - help with fire cement

Will it really loose that much through the bricks into the floor?

Any extra insulation will be fruitless if you dont insulate underneath the ENTIRE oven.
Pull it down and build it properly.

[samcoombes85]

Re: UK oven build - help with fire cement

Damn.

I know what I'll be doing tonight then :-(

Back to the drawing board!

[brickie in oz]

Re: UK oven build - help with fire cement

Its better to see the faults early in the build rather than posting after the build that, "my oven takes ages to get to temp and takes a forest of firewood to keep it warm" which seems to come on here all the time.

[samcoombes85]

Re: UK oven build - help with fire cement

Indeed - thanks again.

So my mix of 3:1:1 fine sand, cement and hydrated lime will be ok to stick it all together?

[brickie in oz]

Re: UK oven build - help with fire cement

Indeed - thanks again.

So my mix of 3:1:1 fine sand, cement and hydrated lime will be ok to stick it all together?

Ive always used propriety mixed refractory glue in oven builds, if anything fails then its not my fault for using the wrong bog ie, home made bog.
But its always used with very thin joints under 5mm.

[samcoombes85]

Re: UK oven build - help with fire cement

Thats my problem - the joints at the front (inside) the dome will be virtually nothing, but in the back, due to the shape would be upto 15mm in places.

If I can find some fire clay powder or similar that would be a bonus, but really looking to get it up by the wekeend to give it a few weeks to cure, then start some fires to cure it all out.

[Bookemdanno]

Re: UK oven build - help with fire cement

Hi Sam ,sorry i'm late!

Replied to your PM too.

I used NHL2 Hydraulic Lime with my build due to using old Victorian Clay Bricks, not firebricks.
If you want to carry on with the pre-mix, you could only use a small amount on the internal edge of the bricks, and chock the outer edge to backfill later. But i would only use this as a very last option, and you'd still need fireclay. Don't rush it.

Try Liam at Kilnlinings, they have a website if you want to source Fireclay and go for the Homebrew mix.
You have Vitcas also, any pottery suppliers, Sheffield Insulations (Sheffins) and even Ebay. Lots of ovens have been built this summer, and many will have over ordered their clay.
Some find that the 3.1.1.1 mix a bit rich so pushing it out to 6.1.1.1 is also an option thats been used over in the UK with fine results.

I have seen ovens built with standard bricklaying mortar, like you mentions Sand, OPC, Lime, and they've done fine. But not necessarily with Firebrick. I'd strip back, get some under-oven insulation (100mm Thermolite Blocks are a good, easily sourced option), fireclay and get back in action. You don't want a "shoulda, woulda, coulda" do you!

Where are you based?

Cheers, Danno

[samcoombes85]

Re: UK oven build - help with fire cement

Hello again,

Ok, i've dismantled my dome, and extended the base insulation to 3" deep, and widened it to fill the entire base of the oven and the entrance.

I have now got hold of some fire clay and hydrated lime. I knocked up a small amount and stuck two bricks together - it feels solid enough, and I soaked the bricks which seemed to make them stick better. What does the lime actually do, as it seemed to go off quick enough using a 3:1:1:1 mix.

Tomorrow I anticipate commencing the re-build, and feel a bit more confident with my muck!

Cheers again for the advice.

[Alomran]

Is your oven with the soft sand / hydraulic lime / portland cement is still standing without any cracks?
intend to build a new oven this week and would like to find the best type of cement to build the dome with. Shall I go for fire cement or 2:1:1 mixture of : soft sand / hydraulic lime / portland cement mixture?
Any feed back would be appreciated.

[Alomran]

What type of fire cement can I use under UK weather to build the brickwork on the dome?
Shall i go for the fire cement ? or the a 3:1:1:1 (sand: lime: portland: fire clay) ...homebrew. Some say a 5:1:1:1 mix for mortar some say do not use fire cement ready mixed like Vitcas as it dries slowly... What are your thoughts?

[Alomran]

Allow me to ask about your statement of :
"Some find that the 3.1.1.1 mix a bit rich so pushing it out to 6.1.1.1 !

1- Kindly confirm what are the materials in the aforementioned ration you were referring to?
2- I am building an oven with ordinary bricks, what sort of cheap mixture of mortar to build the brick dome?
What would you advise to fill the holes on the outside of the mortar?
Thanks

[UtahBeehiver]

Bookemdanno has not posted for quite a long time so he may not following the forum regularly.

[david s]

I believe the reason that the mix is so rich is because if the Portland cement fails it is only the lime acting as the cementious component. The clay is really a fine aggregate only as it won't sinter (go permanent at WFO temperatures), so in that case you are left with a 5:1 ratio, still acceptable.
Making it 6:1:1:1 will leave you with a ratio of 8:1, aggregate to cementious ratio, too weak IMO.

[Alomran]

I believe the reason that the mix is so rich is because if the Portland cement fails it is only the lime acting as the cementious component. The clay is really a fine aggregate only as it won't sinter (go permanent at WFO temperatures), so in that case you are left with a 5:1 ratio, still acceptable.
Making it 6:1:1:1 will leave you with a ratio of 8:1, aggregate to cementious ratio, too weak IMO.

Thank you David for the informative explanation. Some recommend 5:1 ratio for pumice to cement. or Perlite to cement. But looking at your explanation, it seems that 5:1 ration should include 3 parts big stone of volcanic materials, then 2 part of crushed volcanic material, (this make a total of 5 parts which is equal to a 5 part ballast) then one part cement.
This will make a total of 5:1.
So if one uses only perlite with cement without crushed perlite, then the mixture is imbalanced.
Also, if cement degrades with heat, would one part of lime will maintain a bonding agent when the cement becomes sand with heat?
What ration should be used if lime is included?
Thanks

[david s]

I'm not quite sure what you intend to do with this mix. I assumed when you said mortar that you were referring to the mortar used between the bricks. You don't want and pumice in that kind of mortar mix because firstly, the grains are too large for mortar and secondly, pumice will reduce the strength of the resulting mortar joint. If you are making an insulation mixture to clad the dome then perlite is a good material because the minute air pockets in each grain act as insulation. The addition of lime to such a mix for purposes of creating a more refractory brew is unnecessary IMO because (apart from the mix that is in actual contact with the outer surface of the brick) it will not see temps that will destroy the Portland content.
I can't see much advantage in crushing the perlite as it just crushes up the air pockets in the grains, you may as well use sand.