Notes from Windward: #68


Making Bricks

Orly describes the initial work with the CINVA ram

  May 24:

     Making brick out of earth! What is more abundant than earth beneath our feet? When looking to build the next intern cabin, we didn't need to look any further than beneath our toes. In previous editions of the Notes, you can see the construction of the CINVA ram which we are using to compress the earth into bricks.

our CINVA ram

     Before we could start compressing any earth, we had to fix the mortar mixer and construct a riddle.

loading the riddle

     After Walt and I worked on the riddle, he came to the site with the backhoe and dug up some earth. The following day I started shoveling and sifting.

sieving the dirt through the riddle

     Now I was ready to play around with the dirt, mix it up, and get a feel for the whole process. I also got some help from a visiting friend, Eric. We took a five gallon bucket, threw in some dirt (roughly 3 coffee cans), and some water.

working up the proportions

     We mixed it around in the bucket till the water was absorbed and the mixture was uniform and dense.

Eric and Orly getting hands on

     Our first brick didn't last long since we poured in too much water. It became a big blob and fell apart.


     The second brick we used only a little bit of water. This made it very difficult to mix the dirt evenly. After compressing it showed lots of cracks and we figured we needed a bit more water the next time.

our CINVA ram

     The third brick, we put a bit more water, but we weren't able to mix it evenly with just our hands doing the mixing, so it turned out better but not great.

     I did some research online and found an article entitled Making Building Blocks with the CINVA-Ram Block Press where I learned that I needed to test the soil for clay content. I filled a jar halfway with earth and the rest of the way with water. I mixed it really well for 2 minutes and let it sit. The different components settle at different rates so I was able to see the relative amounts of gravel, sand, and clay. Clay is the top layer.


     With the fourth brick we decided to get the mortar mixer going. We didn't make any measurements of the dirt to water ratio, we just eyeballed what we thought was good. The mortar mixer was a step in the right direction. The third brick turned out nicely. It was darker and much more solid that any of the previous bricks.


     There were a few problems we faced in the first 4 bricks that we are in the middle of solving...

1) The CINVA ram didn't pull the brick up all the way after we compressed it so it was difficult to pull out. To fix this Walt cut out some wood/formica shims that we could insert on the bottom.


2) Some parts of the ram didn't fit together well. To fix this, Walt bought some huge washers to help keep the sliding blocks in place. Soon there will be more pics.


     I made a fifth brick with a wood piece on the bottom of the chamber to see if the piece helped. The brick looked great until I tried to take is out of the chamber. It seems that one wooden piece isn't enough. Soon I will put two down and see how that works out. I also have to fit the washers in.

from top left clockwise: 5th, 2nd, 4th, 3rd

     The next part of the project (after the small adjustments) is to get measurements of how much water to add to how much dirt. After that I will perform a box test to figure out the ratio of soil to cement and start playing around with that mix.

  June 27:

     The previously mentioned adjustments have been made (using two wood/formica shims instead of one and inserting the washers) in addition to some new ones. After the initial adjustments, we were still having issues with getting the ram to move smoothly (it would get stuck when we were trying to lift the pole to the vertical position to compress the bricks).


     About a week ago we took the next step of figuring out the ratio of earth to water, which is 10.5 coffee cans earth to 1 coffee can water. The bricks all turned out solid.

     Five days ago we made some further improvements and added cement to the mix. We started by greasing up the ram so that it would move more easily. This made the process run much more smoothly. We worked as a team of three, sifting the dirt and pouring the ingredients into the mixer. We decided to add 1 coffee can of cement to the mix and we quickly learned that we needed to add another coffee can of water. So now the mixture consists of about 10.5 cans of earth, 2 cans of water, 1 can cement. We mixed the earth and cement first before adding water. After the ingredients were mixed we wet the sides of the ram compartment, and did an initial compression of the with our hands by pressing the mix into the corners and sides of the ram compartment. Two people worked on each side of the ram (either compressing or lifting the brick out), while the third lifted the brick out of the ram and set it down to cure. The third person also sprinkled water on the sides to smooth out the cracks. Each batch made about 5 bricks.

     To cure the bricks, we have been laying them out on a flat clean surface, keeping them covered with a tarp, and watering them once a day for the first 5 days, then just keeping them covered for the next 10 days. Soon it will be time to test their ability to keep their integrity under compression and tension.


Notes From Windward - Index - Vol. 68