[Stoves] clay mortar versus cement mortar in stoves

[Christa Roth]

Dear Crispin and other stovers, 

we are wondering in Malawi what would be more beneficial to use as mortar in a household size brick stove like the 'Esperanza stove' we just developped:

Does anybody have experience and evidence, what the difference in thermal expansion, heat resistance and durability (and other potential benefits) is between clay-based mortar and cement mortar?

I suspect that the cement mortar gives more physical strength to the structure, but might have a problem with expansion, as it is rigid and might crack. I also suspect that it desintegrates with the heat.
Clay-based mortar like the people use for the low-cost housing has the advantage of being cheap and locally available, unlike cement. It might have smiliar expansion coefficients like the bricks for being the same material, thus leading to less cracks. but the durabilty might be a problem.
these are all assumptions. Does anybody have evidence?

Next question: can anybody tell me what 'fire clay cement' is? Chemical composition, propertoes, where to get it, how to make it????

Thanks for helping to develop a stove that could cost much less than 5 US...

Christa Roth
Regional Coordinator Malawi - Tanzania - Zambia
Programme for Biomass Energy Conservation in Southern Africa

in Zambia: 
c/o GTZ office, Private Bag RW37x, Plot No. 6469 Kariba Road, Kalundu, Lusaka
Tel +260 1 2919 -18 / 19 / 20, Fax +260 1 291 946
 
in Malawi:
c/o Info Centre for Food&Fuel Security Promotion Mulanje 
P.O. Box 438, Mulanje, Malawi, Phone +265-1-466 279, Fax -466 435

Mobile Phones (only available when I am in the respective country):
Zambia +260 97 207 870, Malawi +265 8 860 936, Tanzania +255 787 20 10 15