#21  
Old 07-15-2011, 04:37 AM
Laborer
 
Join Date: May 2011
Location: Brisbane Australia
Posts: 62
Default Re: Calcium Aluminate - Ciment Fondu

Fornoa

I suspect that it is all in the terminology...

Air dry (usually pre mixed) refractory mortar is recommended up to 2-3 mm

Cement Fondue is likely Ciment Fondu which is the trade name for calcium aluminate cement which was made by Lafarge now Kerneos

Ciment Fondu (calcium aluminate cement) is used to make concrete or mortar that is refractory up to around 1100 C

The Pompeii Oven plans have a mortar mixes with either portland cement and lime or using calcium aluminate cement CAC.

I am using the 3 : sand (or in my case blend with crushed firebrick) 1:fireclay 1: CAC

This mortar will be used to fill the gaps between the firebricks which is up to 20mm

Hope that helps
Brett
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  #22  
Old 07-15-2011, 08:43 AM
david s's Avatar
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Default Re: Calcium Aluminate - Ciment Fondu

Brett,
I think the crushed firebrick is overkill for the mortar. We are not firing to 1100 C. Silica sand should suffice IMO. Do not add lime with the CA cement, it shortens the pot life too much for practicality. Personally I think you are better of with the home brew. It is way cheaper and works really well for the temps we fire to, but if you have your heart set on CA go for it.
Dave

Last edited by david s; 07-15-2011 at 08:48 AM.
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  #23  
Old 07-16-2011, 04:05 AM
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Default Re: Calcium Aluminate - Ciment Fondu

Hi Dave

I was going to use normal home brew but when I found I could buy ciment fondu I thought well I have spend a lot on firebricks and insulation... the cost of the ciment fondu was not that much in comparison even though it was about 5x cost portland cement. So I am hoping one bag will be plenty. otherwise I will be using normal home brew mortar. From what I have read you can also use ciment fondu with portland cement to make rapid set concrete... I will try that sometime for interest.

I did make a whole lot of small trial mixes to see what difference between firebrick, sand and to gauge the amount of water I needed. Also did a mix with lime to see how fast set.

What I found was that when using firebrick you need to add heaps more water than recommended. Maximum 40% water to ciment fondu is what is specified in the datasheet.

With 3:1:1 crushed firebrick:fireclay:ciment fondu needed 1 part water and mix was more like a grout than a mortar. Set in about 2 hours (just under 20 Celsius). Really quite hard and solid mix.

As I substituted the sand for firebrick less water was required and the mix was more workable. I still needed more than 40% water to ciment fondu to get a workable mortar but mix set in 2 hours with no issues.

To one of the mixes I added 1/4 part hydrated lime, more water was needed than the comparable mix without lime. The mix with lime though seemed more smooth and workable as a mortar but was solid in 20 minutes at under 20 Celsius. Seemed just as hard and solid as other mixes.

I have started filling up the triangular gaps between the bricks in the first course of the oven and used firebrick instead of sand but for later courses I will really need to use sand because the mortar with firebrick instead of sand is not very workable at all.

Brett
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  #24  
Old 07-16-2011, 09:33 PM
Peasant
 
Join Date: Jun 2011
Location: Newcastle, Australia
Posts: 32
Default Re: Calcium Aluminate - Ciment Fondu

Hi everyone,

Thanks for the really informative and helpful replies. I now feel more confident using a home brew.

After constructing a steel frame for the base and positioning it, last week I formed up and yesterday we finally poured the slab. (3 photos attached)
I'm a bit worried with me and my mates because after a few well earned beers
all three of us spoke about it in oddly glowing terms. Mmmmmm!!!

Now that I am armed with the necessary information regarding mortar, I will start building oven next week. I have attached a photo of the design I have decided to go with. I liked this design for 2 reasons. 1) because I have no expecience laying bricks and the Barrel vault form I have built means there is little room for error when laying, and 2) there is only minimal brick cutting needed. I plan to use bricks for the sides of the arch and the doorway.

Thanks again guys.
Attached Thumbnails
Calcium Aluminate - Ciment Fondu-oven-frame-slab-001.jpg   Calcium Aluminate - Ciment Fondu-oven-frame-slab-002.jpg   Calcium Aluminate - Ciment Fondu-oven-frame-slab-003.jpg   Calcium Aluminate - Ciment Fondu-finished_unit.jpg  
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  #25  
Old 07-17-2011, 01:46 AM
cobblerdave's Avatar
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Default Re: Calcium Aluminate - Ciment Fondu

Dear Brett

What I found that was workable for me was to make real small batches of mortar so there was no waste and no mortar going off to fast. I used a 20 ltre bucket with a paint stirrer in an electic drill. Measured with one of the wifes tupperware containers. I could fiddle and fart around with one brick without worring a larger batch of mortar waiting to be layed.
Used the forno home brew mortar with cement, lime,firebrick and sand . Found also that it had better workability when using a fine washed sand like the stuff you buy for kids sand pits by the 20 kg bag.
When mixing any concrete or mortar always mix the measured dry ingredients first then add nearly all of the water mix the mortar then add the rest if required. You cant take the water out only add dry which puts your patient measuring out.
Hope to see some photos in the future
Loved the arch in the stand

Regards Cobblerdave
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  #26  
Old 07-17-2011, 05:35 AM
Peasant
 
Join Date: Jun 2011
Location: Newcastle, Australia
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Default Re: Calcium Aluminate - Ciment Fondu

Reading even more posts (Mar 05)
refer:http://www.fornobravo.com/forum/f8/f...ratios-20.html (fireclay mortar ratios)
In this link they say that to minimise cracking the expansion properties of the mortar used should mimic the expansion properties of firebrick and that a mix of 10:3:1.5 sand/Portland/fireclay is fairly similar to the composition of firebricks so it has pretty much the same thermal properties (in terms of expansion, etc.).

Does anyone know if I were to substitute Calcium Aluminate Cement for the Portland cement is this recipe, would the expansion properties of the mortar be any different?

Regards Fornoa
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  #27  
Old 07-17-2011, 06:15 AM
david s's Avatar
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Default Re: Calcium Aluminate - Ciment Fondu

Given that Portland cement fails at temps over 300C the only thing holding the sand together with the above recipe is the clay, which does not permanently change until 573 C so the mortar is never truly hard enough. That is why the home brew 3:1:1:1 sand, Portland, fireclay, lime is superior. The Portland fails but the lime takes over as a binder.
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  #28  
Old 07-17-2011, 12:19 PM
Peasant
 
Join Date: Jun 2011
Location: Newcastle, Australia
Posts: 32
Default Re: Calcium Aluminate - Ciment Fondu

Reading even more posts (Mar 05)
refer:http://www.fornobravo.com/forum/f8/f...ratios-20.html (fireclay mortar ratios)
In this link they say that to minimise cracking the expansion properties of the mortar used should mimic the expansion properties of firebrick and that a mix of 10:3:1.5 sand/Portland/fireclay is fairly similar to the composition of firebricks so it has pretty much the same thermal properties (in terms of expansion, etc.).

Does anyone know if I were to substitute Calcium Aluminate Cement for the Portland cement is this recipe, would the expansion properties of the mortar be any different?

Regards Fornoa
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  #29  
Old 07-17-2011, 12:21 PM
Peasant
 
Join Date: Jun 2011
Location: Newcastle, Australia
Posts: 32
Default Re: Calcium Aluminate - Ciment Fondu

Hi Dave

Reading even more posts (Mar 05)
refer:http://www.fornobravo.com/forum/f8/f...ratios-20.html (fireclay mortar ratios)
In this link they say that to minimise cracking the expansion properties of the mortar used should mimic the expansion properties of firebrick and that a mix of 10:3:1.5 sand/Portland/fireclay is fairly similar to the composition of firebricks so it has pretty much the same thermal properties (in terms of expansion, etc.).

Does anyone know if I were to substitute Calcium Aluminate Cement for the Portland cement is this recipe, would the expansion properties of the mortar be any different?

Regards Fornoa
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  #30  
Old 07-17-2011, 01:57 PM
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Default Re: Calcium Aluminate - Ciment Fondu

Why not just stick with the homebrew mortar? it is cheap and works well. Many builders have used it successfully and reported it works better than many proprietary mixes.We are not trying to create a mortar that has to perform to really high temperature, so you are unlikely to achieve much by going for a product that is designed to do so.
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