Earthbag, also known as superadobe or soilbag, is a structural construction material used in natural building that requires easily found resources. It is mainly made of polymer bags (burlap sack) filled with soil, that is, a mixture of clay, silt, and sand.
Earthbag construction is a construction material which is both strong and can promote quickly building. It is a natural building technique that evolved from historic military bunker construction techniques and temporary flood-control dike building methods. The technique requires very basic construction materials: sturdy sacks, filled with inorganic material usually available on site. Standard earthbag fill material has internal stability. Either moist subsoil that contains enough clay to become cohesive when tamped, or an angular gravel or crushed volcanic rock is used. (Sandbag structures with sand fills are an alternative technology and require very different construction details). Walls are gradually built up by laying the bags in courses — forming a staggered pattern similar to bricklaying.
The construction material is currently being used all over the world, mainly in low-income regions and disaster affected areas.
Any person, community, or organization that wants to construct a low-cost and low-impact structure out of a easily available material: soil.
Earthbag as a construction material has been used all over the world in different countries and several construction sites. Specially, in low-income regions and post disaster affected areas. The earth used in the bags and the rubble for the foundation can be locally found. Polypropylene bags, barbed wire, rebar, sand and cement have to be purchased.
Patented. Superadobe is patented in the USA (US5934027A).
Users can obtain this product by constructing it themselves. Some organizations like CalEarth and Good Earth Global commercialize earthbags construction manuals, equipment, and building designs. There are also other organizations that offer free construction manuals. Earthbag can be produced anywhere the necessary resources which are basically bags (burlap or polypropylene sacks) and soil are available.
The exact number is unkown, however, earthbag construction matirial is an very widespread technique, used all around the globe.
Size of the component
List of primary materials in the component
List of secondary materials in the component
Measurement, calculated in hours, of the component’s resistance to fire
R value associated with material/product
The strength of the component, measured in MegaPascals per inch
- "Stabilising the soil will provide an initial cohesion which indicates that a higher vertical pressure is needed to cause failure of the earthbag. A similar effect can be seen with the introduction of clay to act as a binder and provide some cohesion to the soil." (Vadgama, 2010)
- " The stiffness of the earthbag is expected to increase as vertical applied stress increases which means that it is important to initially compact the earthbag in construction as this improves the initial stiffness of the earthbag and reduces overall short term deformation of the structure." (Vadgama, 2010)
List of suitable climates for use of this components
Earthbag construction is made by filling polymer bags with locally available earth. Even though local earth is used, it’s very important to ensure the correct soil mixture to allow the earth to be compacted as it is tamped inside the bags. Stabilizers such as lime or portland cement can also be added to improve the resistance of construction. The bags are generally made from polypropylene because it is a strong, durable, and semi-permeable material. The filled bags are laid in their desired form and each layer is tamped before laying the next layer. Barbed wire is placed between the layers to hold the bags at the proper position and prevent the wall to get out of plumb. There are several online resources that give very detailed instructions on how to build earthbag constructions.
The building can be maintained by local labour with Earth Building construction experience.
Built and maintained properly, an Earthbag building should stand for centuries.
There are many different manufacturers of earthbag constructions in the market. But, in general, earthbag is commonly described as an low-cost and low-impact technology with great thermal insulation and earthquake resistance.
Tests results available in the studies provided by testing organizations are related to soil mixtures used, this is, there are a wide range of results using different mixtures. As every soil is different from place to place the most important part of construction is to find the correct soil mixture. Besides that, tests concluded that earthbags have a much lower lateral strength than compressive strength, while seismic resistance is to be tested even if it suggests that earthbags have great resistance to earthquakes.
Builders should wear appropriate protective equipment such as hardhats, gloves and safety glasses while working to protect against physical injury commonly associated with heavy construction. Earth bag construction does not require the operation of any large machinery.
On exposed walls, many suggest to use a protective topcoat, embed tile or pebbles in earth plaster, use lime plaster or cement plaster on sandy earthbag fill.
Canadell, S., Blanco, A., Cavalaro, S. H.P., 2016, Comprehensive design method for earthbag and superadobe structures, Materials & Design. V. 96, Pages 270-282
Croft, C., 2011, Structural resistance of earthbag housing subject to horizontal loading. Master’s thesis, The University of Bath.
Daigle, B., 2008, Earthbag housing: structural behavior and applicability in developing countries. Master’s thesis, Queen’s University, Canada.
Kaki H, and Kiffmeyer D. (2004). Earthbag Building: The Tools, Tricks and Techniques (1st Edition). British Columbia, Canada: New Society Publishers.
Malik, A., 2013, Structural analysis of earthbag systems. Master’s thesis, Thayer School of Engineering at Dartmouth.
Tantono, S. F. (2008). The mechanical behavior of a soilbag under vertical compression . Master’s Thesis, Technischen Universität Graz, Graz, Austria.
Vadgama, N., 2010, A Material and Structural Analysis of Earthbag Housing. Dissertation (M.Eng.). University of Bath, Department of Architecture and Civil Engineering.
Zhaoa, Z. Lub, Q. Jiangc, X. , 2015, An Energy Efficient Building System Using Natural Resources–Superadobe System Research. Procedia Engineering Volume 121, Pages 1179-1185
Earthbag are mostly tested by compression strength, lateral load tests and soil mixture (clay, sand, gravel) parameters.
This video gives general information about earthbag construction: Cal-Earth Sustainable Architecture
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