A super adobe structure is a man-made building made of sandbags (small or long) with the native material available in abundance and stacking or putting them in a layer that is reinforced with barbed wires.
Superadobe is extensively used in temporary buildings used for disaster relief, flood control, stabilization of water edges, embankments. If the natively available material doesn't have a good binding property then cement or lime is added to it then the walls are plastered and which is coated with waterproof coating.
This technology dates back to 1984 when NASA called for housing design for future human settlement on the moon and Mars. Nadir Khalili proposed this technology of filling plastic super adobe tubes with moon dust and place together for making a structure.
The first super adobe structure was built in 1995 at the time of the Persian Gulf War for the refugees which was able to hold 15 people in it. Later this super Adobe method has been put into use all over the world in Brazil, Chile, Thailand, and India and even in the United States of America.
Construction Process of SuperAdobe
- Mix the earth material available in the vicinity with cement or lime, asphalt emulsion to give the binding strength.
- Water is added and mixed thoroughly that when the mix is squeezed in hand, it doesn’t leave the hand wet.
- The standard size of the footing trenches is 30 cm (12”) deep.
- The foundation must be made up of 2 or 3 bag rows of earthen material, which should be level and compact.
- The bags are placed in the trenches and start filling upright like a short column.
- Filled bags are twisted and tuck to close the openings.
- The earth is compacted as hard as possible using the tamper, to make it solid, uniform block because only compacted earth becomes strong.
- Attach continuous barbed wire - 1 wire for domes up to 4m (12 ft), 2 wires for bigger.
- Compass is recommended for the construction of domes.
- While placing the bags, make sure that the bags are slightly sloped towards outside.
- An arched entry is placed to the opening to buttress and protect the entrance
- Plastering is done as soon as the stacking of bags is completed.
- The locally available material is used to make the structure waterproof to resist moisture and erosion.
- The construction of a monolithic structural system is enabled by the superadobe techniques by using earth material in curved forms.
- The flexibility property of sandbags allows the construction of a curved surface very easily.
- The transfer of stress is along the surface of the structure but not from the elements like a column- and beam-type buildings in single and double curvature compression shells.
- The different types of load coming upon the structure are uniformly transferred into the ground all over rather than in the beam and column structure where the load is transferred into the ground only via column n footing which creates the two basic structural problems of differential settlement and frost heaving.
- In a monolithic bearing wall, dome or vault, differential settlement and frost heaving do not pose severe problems.
- The superadobe structure being a dome or bearing wall built on a floating foundation, the base-isolated by a layer of gravel or sand, provides the ideal earthquake-resistant structure.
Advantages of Superadobe
- This is an approved technology used in Moon and Mars as it uses the native material.
- This construction doesn’t need any special type of framework for building.
- Their structure can be built for flood control, erosion control, stabilization of water edges, hill slopes and embankments and retaining walls.
- This technology does not require heavy equipment.
- This construction cost is low as it uses native material which reduces the cost of transportation.
- In the conventional construction, the use of forest products is more, whereas super adobe eliminates up to 95% of timber, allowing not only for forest products to be more wisely utilized but also resulting in fire-safe buildings.
- Skilled labor is not required as a technique used in this construction is simple.
Disadvantages of Superadobe
- As the construction of this type of structure is to be done manually, the manpower required is more.
- Requires prior knowledge of superadobe construction.