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.