Pressed Earth Blocks: Make 'Em Yourself!

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THE BLOCKMAKING PROCESS

The first step In making pressed-earth blocks Is to prepare the soil/water/cement "mix". To do this, we sifted the earth we Intended to use to free It of gravel and organic residue (which we spread over our yard In lieu of a water-demanding lawn). Then we dumped 16 shovelfuls of the sifted soil Into our mixing container (which was actually an old sandbox) along with a shovelful of cement, and blended the two together until the mix became a uniform color and consistency.

Next, It was time to add water. Proper moisture content is very important: A mix that's too dry makes for blocks which have built-in cracks, while a too-wet soil-cement blend produces bricks that bend or fall apart as they're transported to their curing site. A good rule of thumb !s: if a handful of the damp mix-when squeezed tightly in your handwill cling together without leaving moisture in your palm, it's just right. (A gallon and a half of water per 16 shovelfuls of soil proved about right for us.)

Converting the final soil-cement-water mix into blocks is easy: All you have to do is load the CINVA Ram's mold with moist earth, pull down on the machine's long handle, throw the lever over, and (very carefully) lift out the damp block.

CURING TIME

The way the CINVA Ram bricks are cured can be just as critical to their ultimate strength as the mix of earth, water, and cement which goes into them. In general, the more slowly the blocks dry, the stronger they'll ultimately be. This means-of course-that freshly made blocks cannot simply be left sitting in the hot sun. To keep our bricks from curing too fast, we always covered them with black plastic right after they came out of the Ram. They then set up without losing excessive amounts of moisture too fast, and could be moved (carefully) by the end of the day or the following morning after they had been pressed.

CINVA Ram blocks, we've learned, can be stacked as high as five deep within a day of their manufacture. (Starting from the time they were stacked for curing, we sprinkled our blocks with water three times a day for a few days so thatonce again-they wouldn't cure too quickly.) Within eight days of leaving the mold, the bricks can be laid up in a wall (using the same construction methods you'd employ with ordinary concrete blocks), after which they continue to harden and gain strength for about 30 more days.

We always stacked our blocks to cure right where they were to be used (thus keeping needless carrying of the bricks back and forth to a minimum). Likewise, we always set up our blockmaking plantthe sifting screen, the mix-box, and the Ram-right where we Intended to build. (That's one of the nice things about pressed-earth construction: Instead of hauling tons of blocks from one site to another, you can move the brickmaking plant itself!)

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