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What makes it so super?
Superadobe is a form of adobe (earthen) construction that uses long snake-like sand bags and barbed wire in buildings with arches and domes, for strong and attractive results. The process was innovated by an Iranian-born architect - activist named Nader Khalili in 1984 in a project sponsored by NASA in pursuit of durable building material for sustainable habitations on the Moon and Mars. The design for Khalili´s superadobe structures met its application in the early 1990s, when large groups of Iraqis found themselves homeless as a result of the Persian Gulf War. Nader Khalili then partnered with the United Nations in order to disseminate his design as a means of emergency refugee shelters. Superadobe construction is a development based on the principles of traditional adobe construction with a few adjustments made to further stabilize the system. Whereas some traditional adobe construction boasts structures standing for over 500 years, traditional adobe is vulnerable to damage by earthquakes. Superadobe, on the other hand, is intended to be earthquake-resistant. Another benefit of Superadobe construction - which can be said of many natural building techniques - is that renovation is simply a matter of mixing more Superadobe and applying it to the existing structure. Maintenance is therefore easily achieved as structures can be continually improved upon.
The components of traditional adobe construction
Traditional adobe construction uses the following materials to form bricks.
- Earth : preferably with a high clay content, this provides structure
- Sand : provides resistance
- Horse Manure : acts as a binder
- Pine Needle or other natural fiber: gives lateral integrity
- Water: creates a paste
The components of Superadobe
Superadobe construction uses the following materials to form a paste which is applied to dome like structures constructed of sandbags.
- Earth: preferably with a high clay content, this provides structure
- Sand: provides resistance
- Cement: acts a binder and a stabilizer: provides earthquake resistance
- Water: creates a paste
Pine Needle can also be added, but the use of cement has proven to be very effective in providing structual integrity.
Construction with Superadobe is a relatively simple process. Generally, the required values of materials gives a ratio of
10 earth : 1 sand : 1/5 cement
In our construction, we used the dirt contained with the fallen sandbags of a failed superadobe construction (USE MATH WHEN DESIGNING YOUR DOME). This particular type of sandbag is called a costal, and contains 60 liters of earth. We applied our paste to a cylindrical wall composed of more repurposed costales from the failed superadobe construction.
- Earth: 10 costales * 60 liter/costal = 600 liter
- Sand: 3 buckets * 20 liter/bucket = 60 liters
- Cement:(.15 bag)* (80 liter bag) = 12 liter
- Water: this material is a bit trickier to measure as every mix is different, depending on the quality of the earth and sand. For our construction,we ended up using about 60 liters of water to procure our paste.
- Combine the dry materials, sifted sand and earth to begin with. Mix with shovels, sticks or hoes to achieve a soft brown blend of the two materials. A useful method for mixing well is to create a second mound by heaping all your materials about a meter away from your original mound. After you´ve moved all the material to the second mound, return the material to the original space. The more cycles you repeat of this, the better mixed your superadobe will be. After the sand and earth are well mixed, add the cement and repeat the mixing process.
- Create a crater in your mound of well mixed dry material. Fill the crater with water and proceed to turn the dry materials into the wet. Add the water in frequent but brief amount - best of all is to have a few friends working at once, 2 or 3 mixing and 1 dousing the pile in water. If you have worked with mortar before, you will recognize the desired texture of the end product: not brittle, but definately thicker than cake batter.
- To test the texture of your superadobe paste, try applying it to a costal. If the mix does not adhere to the costal, it is probably too watery ; add more dry material. If the mix does not spread well ùpon the costal, it is probably too brittle; add more water.
Here are is a video demonstrating proper superadobe mixing technique:
Applying the Paste
As said before, we built a cylindrical wall of costales. Alone, the costales had a predicted durability of 10 years before succoming to weathering damage. With our paste, the predicted durability of the wall is 150 years! The term "repello" describes the process of maintenance of the wall, and includes intermittently reapplying superadobe paste upon the existing structure to prevent cracking. Cracks are inevitable - people walk into things.
Here is a look (albeit brief) at our completed superadobe wall:
- "they have passed seismic testing required under California's strict earthquake-zone building codes." - - Calearth News Article - Sandbag homes may be shelter breakthrough, Anton Ferreira, 30 Jul 2001.
- "Concrete is resistant to earthquakes." http://www.concretethinker.com/Papers.aspx?DocId=329
- California Institute of Earth Art and Architecture (Cal-Earth)
- The Aga Khan Award for Architecture 2004. Sandbag Shelter Prototypes, various locations