2009.11.02_materialconcept_compressedearthblock

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Material Concept Research | June 2009 | CEBs

B R I G H T G R E E N R E S E A R C H . O RG

Compressed earth BloCks (CeBs)

History:

Earth construction has existed or over 9000 years. Adobe houses have beenuncovered in Russian Turkistan dating rom 8000 to 6000 BC as well as homesrom 4000 BC in Assyria. Upper Egypt still displays monumental structuresthat are approximately 3200 years old. The core o Shibam, Yemen was built

entirely out o adobe covering 20,000 sq meters.

Earth Construction:

Earth can be used or building in a variety o ways. Wet earth can be molded by handto orm walls, oten reerred to as cob construction. Earth can be ormed, thrown, orsprayed over a rame making a wattle-and-daub structure. Earth can also be heavilycompressed within a ormwork to make rammed earth walls. Unbaked, handmadebricks o earth are reerred to as Adobe.

Compressed Earth Blocks:

Blocks produced manually by pouring wet earth into a orm and dried are called ado-be. A modern adaptation o this building element is the compressed earth block (CEB).CEBs, also called compressed soil blocks, are produced by compacting moist earth in amanual or powered press. The rst manually operated soil block press was producedin 789 by French architect Franois Cointreaux. More recently, ully automatic presseshave been made, producing as many as 500 to 4000 blocks per day.2

Unortunately, most CEBs need to be stabilized rom erosion with 4% to 8% cementbecause o the lack o sucient water or kneading through impact to ully activatethe binders. Without stabilization, most CEBs have a lower compressive strength thantraditional adobes.3

Construction:

Foundation:

A CEB wall needs a well-constructed oundation. A common oundation is a rubbletrench, extended below the rost line, topped with a cast-in-place concrete beam. Inareas with excessive ground water a drain line should be installed to divert the wateraway rom the walls. The grade beam should be high enough to ensure the wall is wellabove the nished grade, approximately 3 6. A typical reinorced concrete ootingand stem wall can also be used. However, this will involve a signicant amount oconcrete as the stem wall must be a third thicker than the CEB wall, sometimes as thickas .5 eet.

The CEB wall sits directly on top o the stem wall or grade beam and can be connectedby simply leaving the top surace o the concrete rough or a strong mechanical bond.

GernotMinke,BuildingwithEarth:DesignandTechnologyofaSustainableArchitecture(Basel:Birkhauser-

PublishersforArchitecture,2006),6.

2 Minke,63.

3 Minke,64.


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Stacking:

CEBs can be stacked much like typical masonry. A double wall or cavity wall canbe constructed with a layer o insulation, such as a sawdust lime mixture or perliteinsulation, between the interior and exterior CEB walls. Wall ties are used to link theinterior and the exterior aces together. A solid masonry wall can also be constructedrom CEBs with a layer o rigid insulation applied to the exterior. The exterior will needto be nished with stucco or cladding.

Mortar:

CEBs are laid with an earth mortar or lime mortar or slurry. Midwest Earth Builders,a CEB manuacturing and construction company, uses a thin slurry or un stabilizedblocks and a thicker lime mortar or stabilized blocks. Some cement may be added tothe mortar but pure cement mortar should not be used as it is too rigid.4 Earth blocksmay also be dry stacked i the blocks are dipped in water long enough to make thesurace o the blocks sot.

Openings, Bond Beam, and the Roof:

Door openings, window openings, and niches can all be ormed into the CEB wallsusing lintels o cast-in place concrete or solid wood. Arches can also be constructed oconcrete or earth blocks over doors or windows.

A cast-in-place bond beam or a steel or wood ring beam is built above the CEB walls to

tie the walls together and provide a connection or the next oor or the roo. The roo,like the oundation, is necessary in protecting the CEB walls rom the sun and rain thatcause weathering and erosion.

Finishing:

The exterior walls should be nished with plaster, such as lime, cement, or earthplasters, or cladding to prevent weathering and erosion. Because CEB construction isnot monolithic, like rammed earth, it is more susceptible to erosion.

The interior o the CEB walls can be nished with paints, water repellants, plasters, orcladding or let exposed.

Some breathable paints can be used to protect the walls but should be renewed

periodically: a pure lime wash dries white and provides weather resistance; a lime-casein wash can be used to make the surace wipe resistant; a borax-casein wash actslike the lime wash but produces a darker nish; a colorless casein coating retains thenatural color o the earth while increasing its wipe resistance; and other lime washesusing urine, clay, animal glue, and other animal products can also enhance weatherand wipe stabilization.5

Other colorless liquids can be applied to make the exterior suraces o the wallswater-repellant including silane and siloxanes, silicone resins, siliconates, acrylicresins, silicate ester with hydrophobising additives, and silicates with hydrophobisingadditives though each can reduce vapor difusion.6

4 Minke,65.

5 Minke,98-00.

6 Minke,0.


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Technical Information:

Compressive Strength:

The compressive strength o earth construction depends on the distribution o grainsize, the water content, the compaction method o the mixture, and the type o claymineral used. Generally speaking, the maximum compressive strength o a materialis reached i the structural ller, sand and gravel, is distributed or maximum packingvolume and the binder, silt and clay, are ully lling the inter-granular spaces o thegravels.

Testing has shown that kneading earth rather than or in addition to compressing earthproduces a denser material with a higher compressive strength. An internal electricalreaction o the material structure is triggered by water and movement o the mixture.When compressing material, testing has proven that beating or ramming material,types o dynamic movement that cause vibrations in the structure, produces a highercompressive strength than compacting the material with a static orce.

Additives can also increase the compressive strength i necessary. Adding 7% byweight Montmorillonite clay such as Kaolinite and Bentonite or lime and cement willincrease the compressive strength. However, additions o minerals in amounts lowerthan 5% can actually decrease the compressive strength o the material. Other organicadditives such as urine containing urea and ammonium acetate, can increase the

compressive and binding strength as well. Typically, the addition o bers to reduceshrinkage, such as straw, can decrease the compressive strength though in smallamounts can increase tensile strength.

The maximum compressive strength o earth construction ranges rom approximately284 psi (20 kg/cm) to 70 psi (50 kg/cm).7 Compressed stabilized earth blocks, withan average o 5-6% cement or lime addition, have an average o570 psi (40 kg/cm)to 850 psi (60 kg/cm) at 28 days drying. This strength increases 20% ater 2 years.8 AFactor o Saety o at least 7 is usually used to determine the allowable compressiveorce o the material. This means the allowable compressive orce ranges rom 80 psito 120 psi.

Shrinkage and Erosion:

Shrinkage cracks in earth walls should be prevented as increased erosion will occurwhen exposed to weathering. Shrinkage during drying depends on the mixtureswater content, the type o clay and percentage o clay, and the distribution o grainsize o the structural ller. Exterior paints, water repellants, plasters, or cladding shouldbe used in conjunction with overhangs to minimize erosion rom weather.

Insulation and R-Values:

Earth walls have an average oR-0.25 per inch o wall thickness. For a 2 inch wallthat is R-2.8 to R-3.0, and or a 24 inch wall that is R-5.6 to R-6.0. I larger aggregatesare used to increase the porosity o the wall, thus increasing the insulating qualities othe material, a 2 inch wall could reach R-4.4 and a 24 inch wall could reach R-8.7.

This is hardly sucient or the weather extremes o the upper Midwest. CEBconstructions need added insulation on the exterior o the wall, with stuccoor cladding, or buried within the wall, as a cavity wall, to maintain comortabletemperatures year round. Insulation can add R-4 to R-8 per inch to the wall (4 ofinsulation buried between two 5 inch layers of CEBs results in R-21 to R-37).

Minke,43-4.

8 AurovilleEarthInstitute,EarthTechnologies:CompressedStabilizedEarthBlocks,http://www.earth-auroville.

com/?nav=menu&pg=technologies&id=9.


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Acoustics:

A 6 inch CEB wall has a Coecient o acoustic attenuation (tested at 500 Hz)o 40 to 50 dB or an approximate STC of 45.9

Fire:

CEB walls are said to have good re resistance though no testing has beendone to date to conrm this.0

9 AurovilleEarthInstitute.

0 AurovilleEarthInstitute.


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Resources:

Books:

The Adobe Storyby Paul G., Jr. McHenry and Helen K. Kerschnerhttp://www.amazon.com/dp/0826392/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0826392&creative=373489&camp=289

Adobe Houses for Today: Flexible Plans for Your Adobe Home

by Laura Sanchez and Alex Sanchezhttp://www.amazon.com/dp/0865346623/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0865346623&creative=373489&camp=289

Earth Architecture

by Ronald Raelhttp://www.amazon.com/dp/568987676/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=568987676&creative=373489&camp=289

Adobe: Build It Yourself, Revised Edition (Paperback)

by Paul Grham McHenry Jr.http://www.amazon.com/dp/086509484/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=086509484&creative=373489&camp=289

Earth Construction Handbook: The Building Material Earth in Modern

Architectureby Gernot Minkehttp://www.amazon.com/dp/85328058/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=85328058&creative=373489&camp=289

The Good House Book: A Common-Sense Guide to Alternative Homebuilding

by Clarke Snellhttp://www.amazon.com/dp/57990282/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=57990282&creative=373489&camp=289

Simone Swan: Adobe Buildingby Dennis Dollenshttp://www.amazon.com/dp/093082958/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=093082958&creative=373489&camp=289

Ageless Adobe

by Jerome Iowahttp://www.amazon.com/dp/086534034X/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=086534034X&creative=373489&camp=289

Adobe Conservation

by Cornerstones Community Partnerships Staf and Francisco Contrerashttp://www.amazon.com/dp/0865345279/re=nosim?tag=hartworkscom-20&link_cod

e=as3&creativeASIN=0865345279&creative=373489&camp=289

Ceramic Houses and Earth Architecture: How to Build Your Own

by Nader Khalilihttp://www.amazon.com/dp/88962509/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=88962509&creative=373489&camp=289


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Adobe Book

by John F. OConnorhttp://www.amazon.com/dp/0942709X/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0942709X&creative=373489&camp=289

Adobe and Rammed Earth Buildings: Design and Construction

by Paul Graham McHenryhttp://www.amazon.com/dp/086524/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=086524&creative=373489&camp=289

The Owner-Built Adobe House

by Duane Newcombhttp://www.amazon.com/dp/0826323235/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0826323235&creative=373489&camp=289

Casa Adobe

by Karen Witynski and Joe P. Carrhttp://www.amazon.com/dp/58685038/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=58685038&creative=373489&camp=289

Adobe Detailsby Karen Witynski and Joe P. Carr

http://www.amazon.com/dp/58685030X/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=58685030X&creative=373489&camp=289

An Architecture for People: The Complete Works of Hassan Fathyby James Steelehttp://www.amazon.com/dp/0756757967/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0756757967&creative=373489&camp=289

Behind Adobe Walls: The Hidden Homes and Gardens of Santa Fe and Taos by Lisl

Dennis and Landt Dennishttp://www.amazon.com/dp/088646/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=088646&creative=373489&camp=289

Adobe Architectureby Myrtle Stedman and Wilred Stedmanhttp://www.amazon.com/dp/0865347/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0865347&creative=373489&camp=289

Build With Adobe: Revised and Enlarged

by Marcia Southwickhttp://www.amazon.com/dp/0804006342/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0804006342&creative=373489&camp=289

Small Adobe House

by Agnesa Reeve and Robert Reckhttp://www.amazon.com/dp/586850652/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=586850652&creative=373489&camp=289

Adobe Houses for Today: Flexible Plans for Your Adobe Home

by Laura Sanchez and Alex Sanchezhttp://www.amazon.com/dp/0865343209/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0865343209&creative=373489&camp=289


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Adobe: Remodeling & Fireplaces

by Myrtle Stedmanhttp://www.amazon.com/dp/0865340862/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0865340862&creative=373489&camp=289

Pueblo Architecture and Modern Adobes: The Residential Designs of William

Lumpkins

by Joseph Traugott and William T. Lumpkinshttp://www.amazon.com/dp/089033670/re=nosim?tag=hartworkscom-20&link_cod

e=as3&creativeASIN=089033670&creative=373489&camp=289

Building with Earth: Design and Technology of a Sustainable Architectureby Gernot Minkehttp://www.amazon.com/dp/3764374772/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=3764374772&creative=373489&camp=289

Adobe

by David Larkin and Orlando Romerohttp://www.amazon.com/dp/0395566932/re=nosim?tag=hartworkscom-20&link_code=as3&creativeASIN=0395566932&creative=373489&camp=289

CEB and CEB Press Information Kits:

Dirt Cheap Housing Building

Adobe & Cinva Ram Earth Block Resource Guide on CDContains extensive inormation on adobe and CEB making.

Cinva Ram Block Press Plans

Contains plans or building your own block press.

Videos:

A Sampler of Alternative Homes: Approaching Sustainable Architecture

Produced by Kelly Hart

https://www.createspace.com/Workow/cart.do?action=jump&jump.step=cart


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Products:

Compressed Earth Blocks by Midwest Earth Builders

Midwest Earth Builders Compressed Earth Blocks were selected as one o the Top 0Green Building Products o 2008 by Sustainable Industries! Located in Soldiers Grove,Wisconsin, Midwest Earth Builders (MEB) manuactures CEBs as well as builds housesutilizing green materials and sustainable design. MEB use locally available materialsmixed onsite and generate the CEBs using an earth block press.


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References:

Auroville Earth Institute. Earth Technologies: Compressed Stabilized EarthBlocks, http://www.earth-auroville.com/?nav=menu&pg=technologies&id=9.

Minke, Gernot. Building with Earth: Design and Technology o a SustainableArchitecture. Basel: Birkhauser-Publishers or Architecture, 2006.

2009.11.02_materialconcept_compressedearthblock

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