WHAT IS RAMMED EARTH?
• Rammed earth is a simple construction technique based on compacting earth between formwork to make a homogeneous mass wall.
• Rammed earth construction is a process of compressing a damp mixture of earth that has suitable proportions of sand, gravel,and clay into an external supported frame that molds the shape of a wall section creating asolid wall of earth.
• Traditional stabilizers such as limeor animal blood were used to stabilize the material, but cement has been the stabilizer of choice for modern times.
• After compressing the earth the wall frames can be immediately removed and require an extent of warm dry days after construction to dry and harden.
• The structure can take up to two years to completely cure, and themore it cures the stronger the structure becomes.
• When the process is complete it is much like constructing a hand made wall of solid rock.
HISTORY & ORIGINS
• Rammed earth technology has been around for thousands of years, as an ancient sustainable construction material, used to form monolithic walls.
• Long sections of the Great Wall of China, and famous buildings such as the Alhambrain Granada, and the Potala Palace in Lhasa are built in rammed earth.
• Many European castles and the cores of pyramids were made of rammed earth, then faced with stone.
RAMMED EARTH SPECIFICATIONS
• Properly constructed rammed earth walls are unaffected by rain, wind, fire or termites.
• Load Bearing Rammed earth walls are generally 18 to 24 inches thick.
• Non-Load Bearing Rammed earthwalls are generally 10-14 inches thick.
• Rammed earth compressive strength is approximately 300psi.
• Rammed earth walls can be stucco-ed, plastered, or left bare to expose the soft, rhythmic layers of earth, like sediment lines in sandstone.
• Rammed earth can be used in any style building with any kind of roof.
• Properly designed, a rammed earth structure will store the sun’s heat eachwinter and block it each summer, yielding energy savingsyear after year.
• Rammed earth will begin to cure immediately, and can take from several months to several years, depending on weather and humidity to complete the process.
• Rammed earth may have originally been developed in climates where humidity and rainfall did not permit the production of soil block.
• For soil block to cureuncovered, there must be at least 10 rain-free days.
• Soils with high clay contentmay be more suitable for ramming, as they tend to crack in blocks when curing.
• Rammed earth soil mixes must be carefully prepared by screening, pulverizing, and mixing to ensure a uniform mix and to break up any clumps.
• The soil mix needs to be carefully balanced between clay, sand, and aggregate.
• A widerrange of soils are suitable when a small amount of cement (6% of mixture) is added.
• ‘Stabilized Rammed Earth’ is a strong masonry product which provides excellent thermal mass.
• Earth is a widely available building material with virtually no side effects associated with harvesting for use in construction. The earth used is typically subsoil, leaving topsoilreadily available for agriculturaluses.
• Often the soil can be used on the site where the construction takes place reducing cost and energy used for transportation.
• Transporting the soil mix to the forms is a demanding tasks.
• Large quantities of soil must be moved and transported vertically for placement in the forms. This process is not the same as pouring concrete, because the material is not liquid.
• Traditionally,workers passed baskets or buckets of earth up to where it was needed.
• Hoists can also be used effectively for this task.
• Soil is taken from the ground and if necessary sieved to remove larger particles.
• Additives such as straw or limemay be mixed into the soil, which is then dropped into the formwork in layers, usually around 15 cm high.
• Additives such as Kaolin and Bentonite...