[Stoves] RE: Refractory cements for experiments

Sat May 20 05:50:32 CDT 2006

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Dear Jigme

Many thanks for your exhaustive list of castables.  It is really nice 
collection of information.  I will have some information to share on the 
same subject, perhaps in a couple of months.  When the details are reliable 
I will also post them for the benefit of everyone.

It was very interesting to me that at least one of the unit claimed to be 
using phosphate bonds.  From what I have discovered so far, stoves are not 
getting hot enough to warrant the expense of the high temperature castables. 
Most companies punt their high temperature capability which is just not 
required for a domestic stove.

If we have operating temperatures for the appliance (not the flames) of 600 
C max, we should be able to use a phosphate bonded material.  I have yet to 
locate a report on the thermal expansion of such low temperature bonds  It 
seems that all the low thermal expansion materials (ceramics as far as I 
know) are melted at 1150 or higher.  Good results can be achieved at 1200 
and 1250 when the ceramic bonding really gets under way.

I have a report from our ceramics lab that they got at 1150 C a low 
expansion (2.0 x 10^-6) using 52% lithium feldspar and the Maputo clays. 
This is very good news.  It is about 1/4 of the expansion of the standard 
fired clay and that translates into a far better resistance to thermal shock 
than anything seen so far for a stove.  We are going to battle to get 1150 
degrees with a wood fired furnace and are still trying to get the low 
expansion at 1100 which is known to be achievable.

The thermal expansion for the castable seems to be low in most cases, but it 
is more because of the fillers used (expensive ones) rather than because of 
an inherent quality of the cement.  On top of that, they are 'low expansion' 
in the 1500 degree range because all in all they are intended for high 
temperature use.  Stoves don't make that sort of demand for performance.

If we can find a phosphate bond mix that is fired to 900 C and which is 
either physically resilient or has a very low expansion rate in the 25 to 
500 degree range we will have a winner.  It can be made in a pit kiln with 
wood fuel.

Regards
Crispin

----- Original Message ----- 
From: "Jigme Rangdrol" <rangdrol at turboisp.com>
To: "Stove List" <stoves at listserv.repp.org>
Sent: Saturday, May 20, 2006 2:05 AM
Subject: [Stoves] Refractory cements for experiments

Here is what I found on the available stuff for experiments.
Some of you asked me to let you know but I do not remember who you are.
One of you sent me a contact but I lost it, can you resend it please?
Thanks.

I started with the list at:
http://www.anhrefractories.com/products/datasheetsv1.asp
and concentrated on the castables:

[snip] 