By Byron Tumlinson
I have had quite a few people email and ask me to explain the process of making the papercrete blocks. The method and formula I use is as follows.
(1) Tear up paper into about 4 inch pieces. A 3/4 full five gallon bucket will make two 6 x 6 x 12 blocks.
(2) Pour water over the torn up paper until it covers it at least 2 inches. Let it soak for 24 hours.
(3) Make a paper slurry by grinding up the wet paper. I use an old model 3600 Vita-Mix to do this job. It is powerful and can completely grind up a large hand full of wet paper in 15 seconds.
(4) After you get at least 3/4 of a five gallon bucket full of the slurry, mix in about 2 lbs of Portland cement. That is about 4 small vegetable cans of the powder. At the price I get Portland cement, that comes out to about 5 cents per block. The price of Portland cement does vary, so you may get it cheaper or more expensive than I do. Also you can use clay and sand (see comment below). This would make the blocks free.
(5) Use a paint mixer to mix the cement or clay/sand mixture with the paper slurry very thoroughly. I bought a paint mixer at Lowe's for $3.78. I attach the mixer to my 3/8th drill for mixing the slurry and cement.
(6) Pour the mixture into the 6 x 6 x 12 forms (or whatever size forms are best for you). Let these set for at least 30 minutes in hot weather. In cooler weather you may have to let them set longer. You will be able to tell when to remove the forms because the mixture will start pulling away from the sides of the form. DO NOT LET THE MIXTURE COMPLETELY DRY IN THE FORMS AS YOU MAY HAVE A HARD TIME REMOVING IT. At the same time do not remove them to soon as the block may fall apart if not dry enough.
(7) After removing the blocks from the forms, let them set until they are dry enough to handle without falling or breaking apart. Usually this is about 24 hours but it can be as long as 3 days depending on the humidity.
(8) Move the blocks to a drying area in the direct sun or under a shed if you want to protect them from the weather. Stack them and let them completely dry for about 30 days. They will turn white and you will not be able to break them apart. At this point, you can use them for any building project you wish.
This mixture can also be used as the mortar to cement the blocks together in your building project.
I have never used it, but I have read you can also substitute clay and sand for the cement in the mixture and have a block that is just as durable and weather proof. By using the clay and sand from your own land, the cost of the blocks would be zero.
Since I use my blocks in the garden to surround my beds, I use a coating of water proofing in the form of linseed oil. The paper blocks will soak up the linseed oil, so do not be surprised how fast it soaks in. ( I usually brush on one coat on all sides and ends that is enough to weatherproof it).
Also when the blocks are in the forms, they will shrink considerably. I usually overfill the blocks to compensate for this. You will have to experiment to see how you want