I found this brand of brick that is labeled fire brick on craigslist but have practically zero information on it. The brand name stamped on the brick is Duro. What I have found using google suggests that this particular brand of brick is most likely acid and chemical resistant and dense. If I remember correctly I read that dense fire brick isn't that great for building rocket mass heaters. Does anyone have any information on this brand of brick at all and would it be a good brick to use when building a thermal mass heater?
There are many types of "Duro" bricks and i think most of them are very resilient to chemicals and heat. DURO DOT brick is appreciably more resistant to rapid fluctuations in temperature than DURO brick although slightly less dense. The refractoriness of DURO DOT brand brick is unusually high for acid-resisting material. It is well adapted for service in processes employing temperatures as high as 2100 degF in conjunction with nascent gases and acid fumes. It has exceptionally high mechanical strength and abrasion resistance. You'll have to find out exactly which type of "Duro" brick it is and unfortunately I do not know how to distinguish them apart.
If you already had these bricks in your possession i would build a rocket stove outside without using any mortar and just stack the bricks up into an L or J and insulate the heat riser in some temporary way that you could do a long test burn and make the temp rocket stove extremely hot and see if you have any spawling of the brick. duro bricks seem like very industry resilient and expensive bricks and if you got them for free or cheap consider it a good deal.
In general, any dense firebrick is likely to be durable and useful in the feed tube and burn tunnel, where you need abrasion resistance. It can work well in the heat riser if well insulated, but will take longer to come up to full operating temperature and be slightly less efficient. Getting all the MSDS info is always good, but in most RMH cases not essential.
The ideal configuration if you can choose all the materials is probably dense firebrick splits (1 1/4" thick) to line the feed tube and burn tunnel, with soft insulating firebrick or other refractory insulation for the heat riser and surrounding the hard brick core.
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