Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

[david s]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Commercial mortars tend to be designed for much higher service temps (like 1300 C) This is way in excess of what we require. Sand in the mortar can turn to glass in the presence of certain fluxes. This does not occur at the lower temps we use. Lime mortars were used for hundreds of years with great success, but they are not as strong as portland cement mortars, although they do stand up to heat really well. I think the high temp mortars are a waste of money. Just my opinion.
Dave

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Raffy, I have heard fireclay referred to as mortarclay ( actually I have a bag of mortar clay) I think what you may have is straight fireclay.
Eric

Hi Eric,

I'm thinking that too. It would not have fazed me if it were not for the suppliers comment. They said not to mix it with any other substance and adding water would suffice.

This stuff looks like the SK32 Firebricks I bought but in powder form. I'm thinking it sets/bonds the bricks together as it bakes in the heat. Could be an airset type mortar? It hardens if you bake it in the sun but crumbles if you scratch it.

I tried it with the homebrew recipe changing the ratio of sand to 2 since the fireclay appeared to have sand in it already. So it goes 1:1:1:2 lime, portland, the "SK32 Mortar", sand. It hardened after 3 hours and seems to be setting properly. It appears strong but I'll test the bond strength tomorrow once its been given some time to cure.

I'll post the ingredients once I get it from the supplier.

Thanks for your help

Raffy

[100million]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Products Details
Look here

PRODUCT TYPE STA.SK.32 STA.SK.34 STA.SK.34 STA.SK.38
Suhu Kerja Maximum
Dalam (0?C) 1.200 1.400 1.600 1.700
Komposisi Kimia
A12 O3 (%)
Si O2 (%)
Fe2 O3 (%)
35
57
2,3
45
50
1,8
57
32
1,2
70
19
0,7
Ukuran Butir (%)
+ 0,5 mm
- 0,74 mm
<2
<35
<2
<37
<2
<40
<2
<40
Pemakaian Fire Clay Brick High Alumina Brick

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Hey Chris,

Thanks for that link! It gave me other links which showed me that SK32 Mortar is actually heat setting. All I can glean from this is that it will set only through heat. I need advice from you experts whether it would be bad for me to use this SK32 Mortar in place of fireclay for the homebrew. I searched the forno bravo forum for heat set and was surprised to see that Frances has a similar heat set mortar I am using. I am currently reading her thread trying to learn from her experience. Added insight from you guys much appreciated!

http://www.fornobravo.com/forum/f6/h...ying-2584.html

http://www.fornobravo.com/forum/f8/h...clay-2783.html

[pduany]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

As to the cost question, the homebrew is much more cost efficient. The refractory mortar usually runs about $55.00 per 50# bag and most people have said that they use 4-5 bags. For the cost of 1 bag of HeatStop 50 you can make all the homebrew you need to assemble your dome. ....

Perfect looks like I will be going the homebrew route as well

Thanks

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

The SK32 Mortar I'm dealing with seems to be Grog/fireclay Mortar. It is a heatset mortar similar to Frances and it seems Dvonk has used it in his build as well.

Here is the chemical composition: 40% minimum alumina (Al2O3), 30% minimum silica (SiO2), 4% maximum Iron(III) oxide (Fe2O3), and 2% maximum of calcium oxide (CaO) and magnesium oxide (MgO) combined.

To the point, I can't use it (on its own) since it is "sensitive" to water. Frances and some internet "literature" that I've read attest to this. I live in a tropical country and the oven is outdoors. Would there be any "side-effects" if I incorporated this to the homebrew recipe in place of the fireclay?

[david s]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Most of the commercial mortars use calcium aluminate cement which uses a different chemical reaction. You should not mix lime or cement with it because this will interfere with the reaction. I discovered this once when trying lime added to a calcium aluminate cement. It accelerated the reaction making the brew set even faster. The aggregate in these commercial mortars is not sand but crushed and fired fireclay.

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

The aggregate in these commercial mortars is not sand but crushed and fired fireclay.

Hi David,

The aggregate is crushed what? You didn't finish that part. I don't think the mortar I have has calcium aluminate. SK32 mortar never sets because I think its a heat-setting mortar like Frances and Dvonks. I will need to fire the oven to make it set and according to Frances and Dvonk, water will erode the joints if it gets into the igloo so they have waterproofed their ovens. I can't have that so I really have to use some sort of cementitious mortar to widthstand the tropical storms and typhoons here.

[Tscarborough]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Raffy, I am not familiar with that brand product, but on the basis of what they told you and how it is acting, I think it is safe to assume that is a natural refractory clay that has been processed (cleaning, drying, milling) and bagged. A locally produced one is available here in Austin. It is fine for indoor, thin joint projects.

For an indoor fireplace, the fireclay is slaked similar to lime. It is used at the consistency of runny pancake batter. It is for very thin full bed joints only. It does not really "set"; it will only dry out, and is more of a chinking material than a mortar. It should not be used alone for the type of joints used in making a dome.

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Thanks, Tscarborough. Your description definitely matches the material I have. It would have been disastrous if I followed the advice of the supplier. Imagine, the dome and arch would have collapsed once water seeped in. Chilling...

Anyway, since it is some sort of refractory clay I have incorporated it in the homebrew mortar recipe and it is performing now (it seems) as it should. I was still a little bit wary but your reply has eased my mind.

My advice to beginner WFO builders, if you want peace of mind, go with the FB Mortar. Although if budget is an issue, the homebrew is a great cost effective alternative. If it were up to me and money and shipping charges would not be an issue, I would have LOVED to buy the FB Mortar. Even local refractory cement here is quite expensive. It comes to about USD 135.00 for a 20 kilo bag. Ouch!

Thanks a lot to everyone for their help and I just realized, I kinda deviated from this thread's original topic. Apologies to the author.

[Tscarborough]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

And as a supplier, it is a problem I run up against pretty often. Unless I know exactly what you are doing (and I usually do not have time nor inclination to find out), I can only assume that you know what you are doing, and that you understand the nomenclature and are asking for exactly what you want. If you ask me for "mortar", you will get pre-mixed mortar, just add water. If you ask me for "fire clay", that is exactly what you will get. I carry about 10 different types of "cement", so if you ask for that, you will simply get a questioning look.

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

And as a supplier, it is a problem I run up against pretty often. Unless I know exactly what you are doing (and I usually do not have time nor inclination to find out), I can only assume that you know what you are doing, and that you understand the nomenclature and are asking for exactly what you want. If you ask me for "mortar", you will get pre-mixed mortar, just add water. If you ask me for "fire clay", that is exactly what you will get. I carry about 10 different types of "cement", so if you ask for that, you will simply get a questioning look.

I absolutely agree with you. I know the supplier meant well by trying to advise me but it was the different terminologies and the orthodox application methods (that they are used to) that created this whole mess.

I did in fact just asked for fireclay but it was the different labels/terminologies that caused the confusion.

I have to thank you again for easing my mind. Cheers!

[david s]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

Here in Australia fireclay is sometimes used as an additive in mortars. The stuff supplied by companies who service the building industry offer this stuff labelled as fireclay when in fact it is not a true refractory. If you need a refractory (fireproof) fireclay then get it from a refractory supplier. I'm told they are now relabelling the non refractory fireclay and calling it bricklayers clay.

[Raffy]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

I asked them about the alumina and silica content and it is the same as the firebrick that I purchased from them. The "model number" SK32 is apparently an indication of its max temp capacity. I guess I'll know for sure after the "trial by curing fire." hehehehe

[Scott Welker]

Re: Fire clay Mortar Vs Refractor Mortar FB.... HeatStop... Earthcore

I used regular mortar, right off the shelf, and mixed in 20% fireclay. It was easy to work with, dried very hard, and is holding up well. I've had several firings where the oven got much hotter than I like, over 1000F, and no flaking, cracks, or any issues whatsoever have arisen with the mortar.

Not as cheap as mix-your-own but not expensive either, extremely simple and easy to work with. It was the best choice for me.

Scott