Cast Earth is made with equipment used in the concrete industry, although concrete trained operators can not immediately work with Cast Earth successfully. Its chemistry is substantially different and its operating requirements are more rigorous. Attempting to replicate the Cast Earth mix designs and application know-how without prior training can result in expensive and difficult problems, including placing walls with too little strength to meet code requirements that may be dangerous to the installers and occupants.
To outward appearances, the process would look much like a concrete job. Basically what takes place is:
o Wall forms are set to receive the Cast Earth mix, and are restrained from spreading under the weight of the mix by form ties which are secured to the inner and outer forms and run through the inner space between them.
o As the forms are set in place, electrical conduit and plumbing are placed within them as required. Block-outs for window and door openings are also placed within the forms, as is insulation (if any).
o Aggregates (soil and any amendments) are stockpiled at the site.
o A precalibrated concrete mobile mixer is stationed at the site, along with the following:
o When all is in place, the mixer starts producing Cast Earth mix and dumping it into the pump or other placing device, from which it is transferred into the forms. This process is continuous unless it is temporarily interrupted to move items.
o While the mixing continues, soil, calcined gypsum, water, retarder and accelerator are added to the mixer so that it never is depleted of these materials. These additions are semicontinuous; the surge volume of the mixer's bins and tanks allows for short periods without replenishment.
o After the mix has set, the forms are stripped for reuse. In most cases, before they are stripped, a reinforced concrete bond beam is poured in the top six inches, where Cast Earth is not placed to leave a void for the bond beam.
o An alternative to the mobile mixer and all the equipment which feeds it are concrete ready mix trucks which operate in conjunction with a nearby batch plant. In this case, the pouring remains continuous or nearly so, with a full truck arriving just before a truck is empty.
o While the mixing proceeds, iron oxide pigments may be added in various combinations to create color striations in the finished wall.
Note: This description covers volume production of Cast Earth, in which extensive use of equipment and rapid pouring is used to maximize efficiency and minimize cost. In some cases, small projects are built by parties who want to include a segment of Cast Earth for its beauty. In these jobs, cost is a secondary consideration. See This Link for examples of small jobs.
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