Building Material | Rammed Earth – A sustainable Building Construction Technique
Rammed earth is a sustainable way of construction buildings . Rammed earth walls are constructed by ramming a mixture of selected aggregates including gravel ,sand,slit and a small amount of clay into place between panes called formwork .
Its a technique for constructing foundation ,floors and walls using natural raw material .
its an ancient method that has been revived recently as a sustainable building material.
Rammed earth is simple to manufacture . It is non combustible, thermally massive , strong and durable . However structures such as walls can be laborious to construct.
Its environmentally friendly and sustainable way of construction as the construction uses local available material . It generated very little waste .
The soils used are typically subsoil low in clay between 5 % and 15 % which conserve the top soil for agriculture . When the soil excavated for foundation can be used for construction the transpiration costs are minimum saving energy and time as well .
Rammed earth is probably the least environmentally damaging construction material and technique that is readily and commercially available. Also formwork is removable and can be reused reducing the need for lumber .
A vernacular green building material as well as in more recent ECO House rammed earth is an ancient form of construction usally associated with arid areas .
Rammed earth construction may also reduce the ecological impacts of deforestation and the toxicity of artificial materials associated with conventional construction techniques .
Most of the energy is only required in quarrying the raw material.
The color of the rammed earth walls is determined by the earth and aggregate used . The ramming process proceeds layer by layer and can introduce the appearance of horizontal stratification to the walls which can enhance overall appearance .
Rammed earth is very strong in compression and be used for multistory load bearing construction . Research in new Zealand indicates that monolithic earth walls perform better under earthquake conditions than walls made of separate bricks or blocks . A five storey hotel in Queensland is built to stabilized rammed earth . Rammed earth can be engineered to achieve reasonably high strengths and be reinforced in similar manner to concrete although horizontal reinforcement is not recommended and excessive vertical reinforcement can cause cracking problems .
Rammed earth acts as a heavy weight masonry with a very high thermal mass . Basically theramll mass absorbs or slows down the heat transnfer through a material and then releases the same heat when ambiance temperature goes down.
Some times it is required to insulate the walls to limit energy consumption .
It is more effective when the difference between day and night outdoor temperature is at least 6 degree celsius . If used correctly thermal mass of rammed earth can delay heat flow through the building envelope by as much as 10 to 12 hours and can even out daily temperature variations . It is not recommended in tropical regions where thermal mass can hold too much and cause thermal discomfort.
Its a best solutiin for soudn insualtion . it has excellent sound reverbearation chareateristic and dot generate the harsh echoes .
Durability and Moisture Resistance
The basic technology has been around for thousands of yeas and there are many rammed earth buildings still standing that are centuries old . rammed earth does possess a generally high durability but all types of rammed earth walls are porous by nature and need protection from driving rain and long term exposure to moisture .
Manufacturing rammed earth involves compressing damp mixture of earth that has suitable proportions of sand,gravel clay or an added stabilizer into an extremely supported frame or mold forming either a solid wall or individual blocks . To add variety some modern builders also add colored oxides or other materials such as bottles , tires or piece of timber .
The construction of an entire wall begins with a temporary frame ,denominated the formwork which is usually made of wood or plywood as a mold for the desired shape and dimensions of each section of wall . The form must be durable and well braced, and the two opposing faces must be clamped together to prevent bulging or deformation caused by the large compressing forces.
The material is compressed iteratively, in batches or courses, so as to gradually erect the wall up to the top of the formwork. Tamping was historically manual with a long ramming pole, and was very laborious, but modern construction can be made less so by employing pneumatically powered tampers. After a wall is complete, it is sufficiently strong to immediately remove the formwork.
Construction is optimally done in warm weather so that the walls can dry and harden.
In modern variations of the technique, rammed-earth walls are constructed on top of conventional footings or a reinforced concrete slab base. Where blocks made of rammed earth are used, they are generally stacked like regular blocks and are bonded together with a thin mud slurry instead of cement.
Presently more than 30% of the world’s population uses earth as a building material
One of the finest example of Rammed earth construction is 345 Telenor headquarter in islamabad .
A communication tower constructed at the site breaks the world record of tallest earth rammed structure at 100 feet .
The tower wall thickness is around 3 FT and parameter wall width is 2 ft .The project has been shortlisted for the 2018 world ARCHITECTURE FESTIVAL AWARDS OFFICE BUILDING CATEGORY .
other projects are
Though there is growing number of buildings constructed with rammed earth its prospects of entering mainstream construction as a structural material are limited due to form work and labour costs involved together with climate that has relatively high humidity and moderate external temperatures .