Block Making

We’ve had a great deal of welcome rain this summer. Everything is green and lush. I’m still waiting for the methane digester to turn all this grass to gas but you cannot push life (let alone work) in East Texas. We’re in a lovely Indian summer now with Fall-like days and cool mornings and bright sunshine, so we’ve picked up block making. Here’s how we do it—not how you should do it--but it may help you pay a little less tuition if you see what and understand WHY we do what we do.

We have stacked up 250 tons of clay and sand, which we mine with the tractor bucket. I dump 3 x 300lbs. of soil in 3 tractor buckets (10 x 5 gallon buckets each) of clay from the mound onto a hard floor where it is first tilled to a uniform blend, then I dump 100 pounds of Portland and mix it until the soil is a uniform color and properly damp—not wet.

I scoop up the prepared soil and dump it onto the screen above the hopper. Sometimes this requires a raking because of clods, which will not pass the required rock screen—catch a rock in the press, and it will bend the press. The large clods need to be recycled and smashed because they do not have cement inside them and so the blocks will be weak.

Once in the hopper, the fine dirt and cement falls onto the conveyor, which must be moving as you dump—this soil is heavy. The conveyor is connected to the hydraulic system in unison with the pressing pistons, so when any piston is under full load, the conveyor stops. When there is enough hydraulic pressure it resumes. We have identified the speed that keeps the press hopper loaded and thus continuously feeding the press but at the speed of the machine itself. The conveyor is perfect, and we are pleased at its contribution to the process. The hopper is also very slick and has never bridged. We are learning—slowly. Now we just need new bodies!

The blocks come out of the press and roll down a sloped conveyor where they are turned at a right angle two at a time, and they slide to the end of the second conveyor, ready to be off loaded onto the five pallets that hold about 100-120 blocks each. The blocks are first stacked nearly touching and standing on their narrow sides so that they can be watered completely—missing only the side that is down.

They get watered twice the first day to prevent surface cracking. Edges will break in the moving process, but that is no problem because the holes in the wall they leave act as “keys” and so we don’t have to make so many keys later. What you don’t want is surface cracking. They indicate differential drying inside the block.

You avoid surface cracking by thorough mixing of clay, sand and cement, then watering.
I broke one of the blocks made in the morning yesterday by hitting it in the middle with
a hammer. It cleaved properly and a close up reveals very uniform color, perfect fines distribution and a clean edge. The cracking inside came from the hammer blow.

The two of us can make around 200-300 blocks a day. We have to pick up and move 500 each day because yesterday’s batch must go to the construction site the first thing the next day. All the blocks are hauled by tractor to pallets near the construction site and re-laid. Each layer of blocks is first dampened—misted, not soaked. Then the second layer is laid across the first but flat too. The reason for changing the drying pattern of the entire stack is that it reduces the surface area presented to the air—thus less differential drying. When all 100 blocks on a pallet are stacked this way, the entire stack is misted and then shrink-wrapped around its sides. We cover the top with cut grass—of course! Watering must continue twice daily for 14 days until the cement is properly cured and extremely hard.

Two old people making blocks is exhausting, so we sit down a lot, drink electrolytes and enjoy the prospect of a strong, efficient and beautiful house. It doesn’t matter how many blocks we make...we have no worries! You can see the entire process set up in the last picture.