Rammed Earth Construction Part 21210466806514

CONSTRUCTION PROCESS

•

The formwork is constantly removed and placed on the next set of horizontal timbers where the process is repeated. Once the formwork has been moved on, the horizontal timbers are removed from the wall leaving characteristic holes. Upon completion of one horizontal level the formwork is moved vertically, the mass of standing wall being known as a lift.

•

The wall is so solid that, if desired, the forms can be removed immediately. This is necessary if wire reveal texture is desired otherwise walls become too hard to brush after around 60 minutes.

•

Walls take some time to dry out completely, but this does not prevent further work on the project.

brushing to

FORMWORK BRACING TECHNIQUES

DESIGN CONSIDERATIONS

REINFORCEMENT PROPORTIONS

•

Rammed earth walls have

low tensile

strength, and should be reinforced by providing a bond or collar beam. • Beams can be constructed of concrete, wood or steel. • Vertical reinforcing may also be done, •

and may be required by some building officials. All openings in rammed earth walls, such as windows and doors, must have span the opening width.

lintels to

• Water flow and moisture control is critical to protect structural walls. Special detailing to accommodate manufactured windows may be necessary to accommodate wall thickness.

•

All openings for doors and windows will require a

frame.

Wood,

as opposed to metal, is recommended due to the corrosive action of moisture from the soil material.

roof and opening details is necessary to protect the structure from water damage. • Foundations required by most codes are concrete reinforced with steel. • Soil block material may be used as a filler material

•

Careful attention to both

•

between piers of a reinforced concrete pier and beam foundation. Historically, many structures built with earth materials had no

sand and gravel foundations. The latter are excavated trenches filled with two parts sand to

foundation, or used

OPENING PROPORTIONS

•

three parts gravel. Trench bottoms were graded to provide positive drainage. Soil material block should not be used in below grade walls unless supported on both sides. Natural ground may infiltrate the block,

compressive strength.

moisture from the resulting in reduced

BAMBOO REINFORCED RAMMED EARTH •

A Rammed earth wall is erected over a

bamboo reinforced

monolithic stone foundation, using a special T-shaped steel slip form. •

The 31 inch wide wall sections are rammed continuously until the final wall height is reached so that no horizontal shrinkage cracks can occur.

•

¾ inch gap to provide independent movement during seismic activity. Each section is separated by a

•

•

for

Four vertical bamboo rods act as reinforcement for the wall sections, and together with the gap give sufficient stability against horizontal loads created by seismic activity. The bamboo is interconnected with the reinforcement of the foundation as well as with the

ring beam that connects the tops of all the wall sections.

BENEFITS OF RAMMED EARTH • • • • • •

Reduced CO2 Emissions Thermal Mass Noise Reduction Strength Durability Low Maintenance

• • • • •

Fire Resistance Pest Resistance Cost Effective Rapid Construction Environmentally Friendly

CO2 Emissions •

• • •

Using rammed earth as a construction material greatly reduces the amount of CO2 released during the construction of the building. The manufacture of cement requires the burning of limestone and produces CO2 as a waste product. Around 10% of global CO2 emissions are from the cement industry. In using soil taken directly from the site, there is no transport requirement, directly reducing CO2 emissions and taking vehicles off the road.

Thermal Performance •

•

•

•

The high thermal mass of rammed earth walls mean they act to naturally regulate the internal temperature of a building. If a rammed earth wall is designed into the heating system of a structure, the energy required to both heat and cool the building can be greatly reduced, which further reduces the CO2 emissions of the building.

Rammed earth naturally regulates the internal relative humidity of the building, producing an improved air quality. This contrasts greatly with air conditioning systems, which act to dry the air in a building and contribute to harsh working and living environment.

Structural Performance •

Rammed earth is perfectly able to act as load bearing members within a structural system.

•

strength of dry, un-stabilized rammed earth is close to 1MPa. The

•

The strength and stiffness of the material reduce greatly

with increasing water content, and thus the building must

be well designed in order to

maximize the structural potential of the rammed earth.

Embodied Energy • The inherent recycle-ablility

of rammed earth, and the reduction in CO2 emissions during the lifetime of the structure, the high thermal mass and thus low operating costs all mean that rammed earth has a much lower embodied energy than comparable building materials.

Feasibility •

Rammed earth complies with Building Regulations for insulation,

strength, water resistance, fire and acoustics. •

•

Not all soils are suitable for use as rammed earth. The soil must be compacted at a particular water content to ensure optimum compaction, and this water content should be predetermined before construction begins. Structural design of rammed earth buildings is usually very simple, with

walls acting compression,

in

but detailing is important to ensure the rammed earth is used to its maximum potential.

GREEN BUILDINGS Vineyard Residence Victoria, Australia • • •

• •

Rammed Earth Walls angling outward evokes the impression of continuing into the landscape. Cross ventilation is achieved throughout all the areas, between the walls.

Architect: John Wardle Architects Completion: 2002 Area: 400 m2

Center for Gravity Foundation Hall Jemez Springs, New Mexico • • •

Architects: H. Predock, J. Frane Completion: 2003 Area: 279 m2

•

The thick Rammed Earth Walls act as

thermal

composites, keeping unwanted summer heat out during • •

the day and re-radiating it at night. Cooling is achieved thru cross ventilation by opening the sliding panels to the east and the entry doors to the west. In the winter, heat is generated by geothermal water.

Chapel of Reconciliation Berlin, Germany • • •

Architect: Reitermann + Sassenroth Completion: 2000 Area: 315 m2

•

The interior is of oval shape, and is delimited by a rammed earth wall 7.2m in height and .6m in thickness. The Rammed Earth wall contains large fragments of broken brick from the former church, as well as gravel, which together constitutes 55% of the

•

coarse-grained mixture reduces material shrinkage to only .15%. The admixture of flax fibers and

material.

•

This

intensive compaction with a tamping roller was able to produce a

compressive 3.2N/mm2.

strength

of