Block Manufacturing

Block Manufacturing

Perhaps the most important ingredient in pressed block manufacturing is the soil. If the soil sample cannot be formed into a firm ball, there is good indication or insufficient clay content. The test ball should dry hard and have the ability to withstand a scratch by the fingernail without crumbling. Another simple test involves forming a soil sample into the shape of a cigar. An adequate clay content will allow a "cigar" to project over a table edge at least an inch without breaking off. These simple field tests are not intended to provide a definitive answer regarding soil quality and should be used advisedly.

On the other hand, excessive clay content will lead to an unacceptable degree of cracking in the dried blocks.

"Select the soil for your earth blocks by the trial method. Start with a sandy clay loam, a soil that is neither high in clay content nor high in sand content. It should also be reasonably free of weeds, roots and other organic matter.

Make a sample block from the soil you have selected and let it dry. If it warps or cracks when it dries, there is too much clay in the soil and you will have to mix sand with it to make a satisfactory building block.

If the sample block crumbles, there is too much sand in the soil. You will have to add clay, or a stabilizer, to make a satisfactory block."

The decision as to whether or not use site soil or imported soil should not be made as a matter of convenience, but based on the quality of the soil. All soils should be tested by a certified testing lab or a sample block tested for psi strength.

Machine-pressed Earth Blocks can be stabilized, that is, made either water-resistant or waterproof - by the addition of Portland cement to the soil mix prior to block manufacturing. Typically, the percentage of Portland cement is between five and ten percent. This variability in percentage depends both on the clay content of the soil and whether or not the goal is the production of semi-stabilized (water-resistant) or fully stabilized (waterproof) blocks. A thorough mixing of the Portland cement with the soil sample is critical and somewhat difficult. As Portland cement is very dry, the acceptable rage of the moisture content percentage is reduced. For instance, when making natural earth blocks (without stabilizers), the moisture content may range from approximately seven to fourteen percent, with around ten percent typically considered ideal. With the introduction of Portland cement, the acceptable range shrinks.

Most adobe blocks, whether sun-dried or machine-pressed, stabilized or unstabilized, should be cured prior to placement in the wall. Some codes suggest two to three weeks of cure time, however, different soil and weather conditions will alter the drying time. Curing is important because the blocks get stronger and slightly shrink as they dry. Shrinkage and settling are typical in earthen structures and these unwanted effects can be minimized with curing. Earth Block, however, can be used almost immediately.

Earth Blocks can be stored for unlimited periods of time (unstabilized must be kept dry). The blocks must be sufficiently elevated off the ground to prevent moisture from wicking up into the stack. If poly/plastic covering is used, it is worth noting that the black variety better withstands sun damage than the clear.

Earth Block, Inc.

P.O. Box 3605
Pagosa Springs, CO 81147
Jim or Nora Hallock
Phone: 970-883-2456
Email: earthblock@juno.com