Test Blocks

Since the Christmas day tornado we have experienced considerable rainfall (very welcome) and rather a cold return to winter. The peaches and plums are however blooming after a week of hot weather near the 80’s. Weird!

Anyways, we have not been able to get a bull-dozer on the property to push up the stockpiled soil from the dam nor have we been able to get dry enough material from the smaller stockpile we already have to make test blocks.

Last year we did sample the soil for pH, silt and clay content. We also did a test to see how much lime it would take to “stabilize” a block of our compressed soil. That test revealed that 5% lime (by eight) would be enough to get the pH to 12.0--which defines stabilized, or water resistant. That was good news. The picture below shows the test process for lime stabilization.

© Dan Schellenberg Lime Stab test.jpeg

We found some better tiller tines to use in place of the cultivator tines we had originally installed as a bridge buster. I think these new tines will reach deeper into the hopper and cause more disturbance too. See the picture below of the new tines.

© Dan Schellenberg new tines.jpg

We’ve also been working to perfect the controller program and that is now first class. It allows us to work manually with a step switch or on full automatic. I can also calibrate the sensors to the pins electronically. This is a very robust and sophisticated controller, developed by Bell Systems in Arlington, Texas. They also created the remote control watering system so I can turn on the misting pump from the tractor.

The entire system of soil sifting, moisture control, cement mixing and block pressing is now in place. As soon as the threat of a bad freeze passes, we will press five test blocks in sets of 30 blocks each. We will add 5% lime to 30 blocks. We will add 10% lime to 30 more.We will do the same with cement and then cement plus 5% Bentonite clay. When the soil is mixed and the additives and moisture are ideal (tested by dropping a ball on the hard ground) we can press 30 blocks in about 5 minutes. How long it will take to make 500 remains to be seen.

Once the test blocks have been shrink-wrapped and covered from the sun, they will cure for 14 days. A random sample of 2 from each pile will be taken to a state certified lab where they will be crushed and broken to determine their relative compression strength and their modulus of rupture—how easily they will crack.

We, of course, are trying to find the least-cost, least effort block that exceeds the required minimum standard of 300 psi compression and a modulus of rupture of about 30 psi. These are New Mexico CEB standards.

We will report on the test results in a future blog.

#cebblockmaking #rammedearthblocks

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