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Stabilize the Clay
Mixing Mortar for Earth Block Construction, Loreto Bay, Mexico

The mortar is mixed at the building site.

Photo © Jackie Craven
Although clay is essential in earth block construction, blocks that contain too much clay may crack. In many parts of the world, builders use Portland cement to stabilize the clay. At Loreto Bay, Earth Block Operations Director Jim Hallock uses freshly-mined lime.

"Lime is forgiving and lime is self-healing." Hallock credits lime for the endurance of the centuries-old Tower of Pisa and the ancient aqueducts of Rome.

The lime used to stabilize the clay must be fresh, Hallock said. Lime that has turned gray is old. It has absorbed humidity and won't be as effective.

The exact recipe used to manufacture CEBs will depend on the soil composition of the region. Here in Baja California, Sur, Mexico, the Loreto Bay plant combines:

  • 65% clay
  • 30% sand
  • 5% lime
These ingredients are placed in a large concrete batch mixer that spins at 250 rpm. The more thoroughly the ingredients are mixed, the less need there is for stabilizer.

Later, a smaller mixer (shown here) is used to combine the mortar, which is also stabilized with lime.

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