If I were to tell you that I spent the last week using a giant mixer, a piping bag and biscuit molds, you might think that I chose to redirect my Maguire grant to study the delightful field of baking. Rest assured, I’m still researching compressed earth block technology for a rural housing project. But I did get to use all of those things, and a lot of other seemingly kitchen-related material, out in the field when I attend DwellEarth’s training session last week.

I was one of 15 attendees at DwellEarth’s semi-annual training sessions.

DwellEarth is a construction firm that specializes in compressed earth block construction.

The other participants came from all over the world. Though earthen construction is certainly lagging in America more than in other parts of our world, I am happy to say that I had some fellow Texans in my company. We began the week with a brief orientation before heading out, almost immediately, into the construction site where the hands-on learning would begin.

The first day focused on material science. We learned how to identify the different components of soil to determine how viable it was for construction. These tests ranged from incredibly simple – involving nothing more than your hand and a sprinkle of water –  to more methodical – moving a mixture of soil and water through a series of test tubes to separate the different compounds.

Most soil is made of a mixture of clay, silt and sand. To prep the soil to be used in a compressed earth block, you need to know the proportion of these three components in the virgin soil, and see whether it needs any modification. Check out a few of my tests below!

One of the simplest tests. Simply mix a pile of soil with water until just moist. Rolling the soil into different shapes will give you different information about its properties.

Tools we used to test the soil. Beginning at the top left, you’ll see the soil mixes with 10%, 20%, 30% and 40% sand by volume, all jammed into biscuit molds. As the soil dried, some biscuits shrank or cracked, which helped us determine the correct amount of sand to add. My sample performed best in its original state.

This test determines whether or not the soil is expansive. After mixing with water and standing several hours, the sample should settle back below the black line. Our soil (on the right) was slightly expansive.

The second day focused on the block making process. Out at the training site were two different presses: one automatic and one manual. We began with the automatic machine. Based on our soil tests from the previous day, we put the appropriate amounts of soil and water into a mixer. We also added a small amount of cement to act as a stabilizer. After thoroughly mixing, the soil was moved up a conveyor and dumped into the press. The soil then funneled into the chamber to be subjected to a burst of about 2000 psi of pressure. Several seconds later, out popped a compressed earth block! The blocks were transported to a curing stack. The manual press worked similarly, but required a little more muscle to get the block fully compressed.

The BP714 (automatic press). The soil mixture travels up the steep conveyor into the hopper, and then is lowered into the chamber for compression. The levers to the left control the compression chamber, and the block is released onto another conveyor for inspection.

The Aurum (manual press). The soil is loaded into the top and lowered into the compression chamber. As the chamber lowers, the long pump (far left) is raised. Once the lid is locked in place, the pump is pulled down to compress then release the block. For most of our mixtures, It took two (sometimes three) teammates to complete the compression.

It amazed me throughout this entire process how intuitive these methodologies are. I began to understand how the dirt should feel before it went into the press. I could tell when it was too dry or needed more sand added in. The machines could speak to us, as well. Our instructor, Adam, encouraged us to think about the exercise as listening to the story of the block. The machine would tell us what we needed to know about the mixture, and we could adjust it in turn. Within a number of hours, our whole team – most of us with little to no experience in construction, let alone earthen construction – understood the fundamentals enough to begin producing quality earth blocks.

Days 3-5 forthcoming!