Compressed earth bricks, back to the drawing board.

Its been almost a year since I constructed the chimney of the aluminum furnace out of CEBs. Indiana has a harsh winter season with more than a few freeze/thaw cycles. This is the result of exposure to that bitter winter moisture!

Spalling of many of the faces of the bricks due to freezing after moisture intrusion.

Notice how the mortar has held up better than the clay body of the bricks.

My initial hypothesis is that I skimped too much on the cement content of the clay mix for the bricks. The higher level of cement would likely add to the moisture resistance of the bricks by lowering their water absobtion rate. That is critical in outdoor enviroments where water and freezing are combined threats.

Not sure what I will do about this yet. I do know that any unfired CEBs that I make in the future will have a higher cement quantity in the clay mix. Or I may skip the cement and just fire my CEBs in a clamp kiln to vitrify them and gain the waterproofing needed for my Indiana climate.

The aluminum furnace chimney may be torn down and rebuilt, not sure yet about that either.

Pressing firebricks

Ive been working on a home addition at my house for over a year now. I dug out along the foundation to lay drainage pipe and heating tubes from the wood furnace. The soil is a very sticky clay here. Perfect for the firebricks we have been making for the lining of the furnace.

After sitting in the sun for several days with no rain, the clay hardens into stiff clumps that need broken down for mixing with sand.

50% clay, 40% sand, and 10% portland cement.

Here is a pile of free creek sand taken from my property.

The mix is damp but not soggy. It will clump in your fist.

And here is the result from the press!

Making clay firebricks.

My oldest son William has joined me making bricks. I have contracted out to him the job of making the firebricks for my wood heat boiler. He has done a pretty good job for a near 16 year old kid. Using only a shovel, wheelbarrow, mixer and hand mold, he has made me 60 of these so far.

First fireup test! April 12, 09

Even though the chimney isn't to its finished height yet, I was excited to try out the furnace to see how it may do with a small fire in it. Would the flue and chimney draw smoke? Very well was my observation! I found it to do very well. It may have had trouble though if it had been a windy day with the low chimney height it has now. I will fix that soon.


It feels really good to see it in action!


I made a small fire this time so not to crack any bricks. Just wanted to drive out the left over moisture in them and the mortar joints. Did see some steam coming out of a few places. Not to much though. Some of this brickwork had been drying out for a few months now.



Once the fire was hotter it drew through the flue great! Not to much smoke in the shed.

Brickmaking and furnace update for April 11, 09

Heres the progress on the furnace chimney! It wont be long now till its first smoke!


I love the warmer weather we now are enjoying here.

Back outside. 3-26-09

With the warmer spring weather Ive had here, I set up my brickmaking outdoors to increase output.

By stockpiling clay and sand in bigger piles, I can mix up more and larger batches for the presses.

I have made alot of progress on the chimney base since the last post. I am nearing completion of the flue and base. Im starting to form up the chimney stack now. This is were its gonna really take shape!

Construction update 3-20-09

Poured some concrete for the bottom of the flue passthru and ash chute. It is a concrete made with sand and gravel from a closeby creekbed. In the mix is a portion of clay. The idea being to give it some ability to resist the heat of the gases as they pass thru the flue.

Progress for Feb 22, 2009

Just a small bit of work done lately on the top of the front face. Wont be long now till I pour the top slab and finish this part of the furnace. Need the weather to warm up!

Brick furnace construction update Feb 15, 2009

Ive began work on the flue passageway thru the wall to the chimney. Aslo began closing off all of the brickwork gaps around the front door of the arch chamber.

Brick furnace update for Feb. 9

Heres my progress so far. Getting close to the top! If I had to do it over I would have added more cut bricks to surround the arch. But for my first work, it isn't too bad.

Brick furnace archway key

A two day spell of warmer air has given me the chance to lay some more bricks. When I made the plans up for the archway to the firebox I figured I needed twelve tapered bricks. Either I got the number of brick needed for it wrong or my inexperience at laying the mortar joints for them at an angle is showing. Rather than redo all of it I improvised and came up with a keystone of sorts. Im sure it will be strong enough for this project at least.

All along I knew I would have to cut off the tops of the arch bricks to keep the access door to the crucible shelf low enough for access. This works out ok for that also. I have some mortar joints I need to clean up, but its not too bad I think. Gives a strange diamond detail to the arch. I like it!

More bricks pressed

With the warmer temps here lately, I have managed to press another 38 bricks for the furnace.

I am trying a different red stain mix on some of the brick faces. Its a mix of redwwod deck stain like before, a small amount of yellow water based paint and a couple table spoonfulls of portland cement. I want to see if it helps give the face of the brick a harder, sealed surface than just using the red stain alone would.

Im also messing around again with the ingredients on a few sample bricks. So far Ive settled on a mix of about 50% brown clay, 40% sifted creek sand, and 10% portland cement.

For the test sample I have went with 25% brown clay, 25% yellow clay, 40% sand and 10% portand cement. The yellow clay comes from the same hillside but its in a seperate band Ive uncovered below the brown clay. It seems to be stickier than the brown is and I want to see if it will be more water resistant mixed into the brick. I will let you know my findings.

Building the inside brick arch.

I used an old water pressure tank as my arch form.

I had some trouble pulling the old tank out the next day. It had gotten stuck where the welded beads of the tank rubbed against the bricks. I was finally able to wiggle it out without cracking any of the bricks or mortar joints. Lucky me.

I still have alot of mortar work left to do on the inside of it. But it will have to wait for the weather to warm back up some. Next few days are gonna be below zero with wind chill.