- Cast-refractory heat risers using perlite aggregate, or other methods to create insulation value, various thickness (1" to 2" have been successful in short-term prototypes but long-term data not available).
Has anyone used Geopolymers, specifically Low-Temperature Geopolymer Setting (LTGS), for the construction of their rocket stove? Any short term or long term data?
I am building a small j-tube 6" rocket stove with a 4.5" x 9" x 18" burn tunnel to heat riser ratio (1-2-4) as a prototype. The box portion will be cast with LTGS. The riser portion will be made from "Kiln Brick".
The curing is done initially at ambient room temperatures. Then a solar curing box can be used.
The wall thicknesses will vary from 1 1/2" to 2 1/2".
The main ingredients of the LTGS are:
sodium water glass powder
very fine slag sand
a very small amount of portland cement
I obtained the ingredients for the firebox mentioned above for about $30.
Glenn Herbert wrote:I checked the specs and the customer Q&A at Lowe's, and these are not "concrete" as the title says, but standard firebrick. The 3000 degree spec is contradicted by an answer in the Q&A that says they are good for 2000-2300 degrees, which is good enough if not spectacular. 3000 degree firebrick are a specialty high-performance item, not likely to be standard at a consumer big box store. Kiln supply companies offer 2300 degree and 2600 degree firebricks, with the 2600 version distinctly more expensive.
The upshot is that this would be a typical material for a J-tube and heat riser. You might want full thickness firebrick (4 1/2" x 9" x 2 1/2") for the bridge over the burn tunnel, as that shape might be more durable than the equivalent in splits on edge; I haven't seen comparison tests there.
I am building a j tube rocket stove and saw this Lowes fire brick as well. I did not find the 2000/2300f rating. But if its suitable its easy for me to get and no shipping. Can you explain what you mean by full thickness bricks. or splits? much appreciated
A full brick is 2.5" thick a split brick is 1.25" Same shape just not as thick. Insulated bricks are the best choice for your core away from the feed tube ,splits are desirable in the feed tube. Masonry supply houses usually have fire bricks and 50# sacks of fire clay.
I'm looking to source firebricks via Craigslist, and came across the following offer at 50 cents per brick which seems like a great deal if they are right kind:
* Solid "Hi-fired" clay
* 8-3/4" x 4-3/8" x 1-1/4" each
* Per manufacturer, these products will withstand temperatures of 2700° F. with an Alumina (Al203) content of 21% and a Silica (Si02) content of 70%. The Pyrometric Cone Equivalent (PCE) is 18-19 and the modulus of rupture (MOR) exceeds 1000 psi. This brick is in conformance with ASTM C 1261-10 (Standard Specification for Firebox Brick for Residential Fireplaces)
I have been hunting for a web page that will tell me something about ASTM C-1261-10 without asking me to pay $50 first... I'm just hoping this is an insulated firebrick split, where I could stack these and not need to add insulation around them for the riser and burn tunnel (beyond the insulation under the burn tunnel to protect the floor underneath if needed).
What you have found sounds like it is heavy split firebricks, not insulated bricks. They would be perfect to use for the feed tube in a J. Most masonry supply houses carry thick and split heavy firebrick, but they do not seem to stock the insulated brick. Most can order it for you. They always have fire clay available.
I was recently doing a job at a pulp mill in SE Washington. The kiln/refractory guys were there... Full pallets of every kind of fire brick known to man, including one that was ALL insulated split bricks ! Pallet after pallet of 50# sacks of solid refractory and insulated refractory... I was drooling...I told the guys how envious I was of all their supplies... they laughed and said I could have anything I wanted... Unfortunately the mill frowns at stealing product they paid for... I chose to not help myself. Sadly the refractory will sit in a shed and go rock hard, the firebricks of course are good for ever.
Any heavy industrial area (refinery's , pulp mills , wood saw mills if they kiln dry) they will have boilers and boilers need fire brick and refractory! I have acquired well over 100 heavy bricks and a few insulated , all for free, I live in timber country, we have saw mills, they are constantly buying things at auctions from other saw mills that have shut down. Very common for pallets of firebrick to be bought but not really needed... Is there a saw mill near you ???