Compressed Earth Block often referred to simply as
CEB, is a type of manufactured construction material formed in a mechanical press that forms an appropriate mix of dirt, non-expansive clay, and an aggregate into a compressed block. Creating CEBs differs from
rammed earthRammed earth, also known as taipa , tapial , and pisé , is a technique for building walls using the raw materials of earth, chalk, lime and gravel. It is an ancient building method that has seen a revival in recent years as people seek more sustainable building materials and natural building methods...
in that the latter uses a larger formwork into which earth is poured and tamped down, creating larger forms such as a whole wall or more at one time. CEB blocks are installed onto the wall by hand and a slurry made of a soupy version of the same dirt/clay mix, sans aggregate, is spread or brushed very thinly between the blocks for bonding. There is no use of mortar in the traditional sense. (This is not necessarily true for vertical presses, see link at bottom of page)
Development
The advance of CEB into the construction industry has been driven by manufacturers of the mechanical presses, a small group of eco-friendly contractors and by cultural acceptance of the medium in areas where it is seen as superior to
adobeAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
. In the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, most general contractors building with CEB are in the Southwestern states:
New MexicoNew Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
,
ColoradoColorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
,
ArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
,
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, and to a lesser extent in
TexasTexas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. However, manufacturers of the mechanical presses enjoy their heaviest sales overseas.
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and
Third WorldThe term Third World arose during the Cold War to define countries that remained non-aligned with either capitalism and NATO , or communism and the Soviet Union...
countries have been attractive markets for the presses for years.
Advantages
The advantages of CEB are in the wait time for material, the elimination of shipping cost, the low moisture content, and the uniformity of the block thereby minimizing, if not eliminating the use of mortar and decreasing both the labor and materials costs.
- CEB can be pressed from humid earth. Because it is not wet, the drying time is much shorter. Some soil conditions permit the blocks to go straight from the press onto the wall. A single mechanical press can produce from 800 to over 5,000 blocks per day, enough to build a 1200 square feet (111.5 m²) house in one day. The Liberator
The Liberator is a high performance, open source, compressed earth block press., developed by Open source ecology.In tests, it was able to produce 6 bricks per minute with manual controls. Its theoretical limit is 12 bricks per minute with automatic controls.A remarkable aspect of this press is...
, a high performance, open source CEB press, can produce from 8,000 to over 17,000 blocks per day.
- Shipping cost: Suitable soils are often available at or near the construction site. Adobe
Adobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
and CEB are of similar weight, but distance from a source supply gives CEB an advantage. Also, CEB can be made available in places where adobe manufacturing operations are non-existent.
- Uniformity: CEB can be manufactured to a predictable size and has true flat sides and 90-degree angle edges. This makes design and costing easier. This also provides the contractor the option of making the exteriors look like conventional stucco
Stucco or render is a material made of an aggregate, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as decorative coating for walls and ceilings and as a sculptural and artistic material in architecture...
houses.
- Non-toxic: materials are completely natural and do not out-gas toxic chemicals
- Sound resistant: an important feature in high-density neighborhoods, residential areas adjacent to industrial zones
- Fire resistant: earthen walls do not burn
- Insect resistant: the walls are solid and very dense, discouraging insects
- Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
resistant: there is no cellulose material - such as in wood, Oriented Strand BoardOriented strand board, also known as OSB and SmartPly , is an engineered wood product formed by layering strands of wood in specific orientations. In appearance, it may have a rough and variegated surface with the individual strips Oriented strand board, also known as OSB (UK) and SmartPly (UK &...
or drywallDrywall, also known as plasterboard, wallboard or gypsum board is a panel made of gypsum plaster pressed between two thick sheets of paper...
- that can host moldMolds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...
Presses
CEB had very limited use prior to the 1980s. It was known in the 1950s in
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, where the Cinva Ram was developed by Raul Ramirez in the Inter-American Housing Center (CINVA) in Bogota, Colombia. The Cinva Ram is a lever-action, manual press that makes one block at a time.
U.S. manufacturers produce much larger machines that run with diesel or gasoline engines and hydraulic presses that receive the soil/aggregate mixture through a hopper. This is fed into a chamber to create a block that is then ejected onto a conveyor.
During the 1980s, soil-pressing technology became widespread.
FranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
,
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
,
GermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and
SwitzerlandSwitzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
began to write standards. The
Peace CorpsThe Peace Corps is an American volunteer program run by the United States Government, as well as a government agency of the same name. The mission of the Peace Corps includes three goals: providing technical assistance, helping people outside the United States to understand US culture, and helping...
, USAID, Habitat for Humanity and other programs began to implement it into housing projects.
Wall construction
Construction method is simple. Less skilled labor is required; wall construction can be done with unskilled labor encouraging self-sufficiency and community involvement. If the blocks are stabilized with
cementIn the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
and/or
fly ashFly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...
, they can be used as bricks and assembled using standard masonry techniques of brick-laying.
Soil mix conditions
The soil mix is 15-40 percent non-expansive clay, 25-40 percent silt powder, and sharp sand to small gravel content of 40-70 percent. The more modern machines do not require aggregate (rock) to make a strong soil block for most applications. Soil moisture content ranges from 4 to 12 percent by weight. Clay with a plasticity index (PI) of up to 25 or 30 would be acceptable for most applications. The PI of the mixed soil (clay, silt and sand/gravel combined) should not exceed 12 to 15; that is the difference between the Upper and Lower
Atterberg limitsThe Atterberg limits are a basic measure of the nature of a fine-grained soil. Depending on the water content of the soil, it may appear in four states: solid, semi-solid, plastic and liquid. In each state the consistency and behavior of a soil is different and thus so are its engineering properties...
, as determined by laboratory testing.
Finishing
Completed walls require either a reinforced bond beam or a ring beam on top or between floors (8')and if the blocks are unstabilized, a plaster finish, usually stucco wire/stucco cement and or lime plaster. Stabilized blocks create a brick wall that if properly stabilized can be left exposed with no outer plaster finish.
Foundations
Standards for foundations are similar to those for brick walls. A CEB wall is heavy. Footings must be at least 10 inches thick, with a minimum width that is 33 percent greater than the wall width. If a stem wall is used, it shall extend to an elevation not less than eight inches (203 mm) above the exterior finish grade. Rubble-filled foundation trench designs with a reinforced concrete grade beam above are allowed to support CEB construction.
CEB code
CEB's strongest market in the USA is probably
New MexicoNew Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, which has incorporated the method into its Earthbuilding Code family. The first CEB Code Development meeting in
New MexicoNew Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
took place Dec. 12, 2001. The persons present at that meeting are considered today the leading experts in the field. They include:
- Fermin Aragon, general bureau chief of the Construction Industries Division for Santa Fe, New Mexico
- Joe M. Tibbets, publisher of Adobe Builder Trade Publications, Bosque, New Mexico
- Larry Elkins, Adobe International Inc., Milan, New Mexico
- Jim Hallock, Earth Block Inc., Pagosa Springs, Colo.
- Lawrence Jetter, A.E.C.T., San Antonio, Texas
- Jim Hands, P.E., Red Mountain Engineering, Santa Fe, New Mexico
- Todd Swanson, Bio-Hab Inc., Hesperus, Colo.
- Joaquim Karcher, architect, Taos, New Mexico
Code work was completed June 10, 2002 and melded into New Mexico's new section, R1100 Earthen Building Materials.
The CEB code is different from the
adobeAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
code in numerous respects. For instance, the CEB code allows slip mortars and permits blocks ejected from a press to go directly to the wall.
CEB strength
Using the ASTM D1633-00 stabilization standard, a pressed and cured block must be submerged in water for four hours. It is then pulled from the water and immediately subjected to a compression test. The blocks must score at least a 300 pound-force per square inch (p.s.i) (2 MPa) minimum. This is a higher standard than for adobe, which must score an
average of at least 300 p.s.i. (2 MPa)
It must be emphasized that the compressive strength minimums for code compliance are nothing like the true strength of CEB blocks.
New MexicoNew Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
only sought to assure that CEB would be at least as strong as adobe.
CEB can have a compressive strength as high as 2,000 pounds per square inch (13.7×10
6 Pa). Blocks with compressive strengths of 1,200 (8.27×10
6 Pa) to 1,400 p.s.i. (9.65×10
6 Pa) are common.
Thermal advantages
Also, due to the enormous mass - these are monolithic walls - CEB has excellent thermal performance, reducing heating and cooling costs.
Thermal testing: From May 31 to June 3, 2004, the Biology Dept. of
Southwest Texas Junior CollegeSouthwest Texas Junior College is a comprehensive, public, two-year college with four campuses serving eleven counties in southwest Texas.The campuses are located in unincorporated Uvalde County , Del Rio Southwest Texas Junior College is a comprehensive, public, two-year college with four campuses...
, Del Rio, Texas, conducted tests for thermal change on three structures: concrete block,
adobeAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
and compressed earth block.
Results indicate the interior temperature of the
adobeAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
and CEB modules were significantly lower than for concrete blocks.
With a maximum ambient temperature of 107 °F (41.7 °C), the interior temperatures were:
ConcreteConcrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
Module: |
111 °F (43.9 °C) (four degrees Fahrenheit above ambient) |
AdobeAdobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...
Module: |
95 °F (35 °C) |
| CEB Module: |
91 °F (32.8 °C) |
The CEB module was consistently cooler inside than the adobe by approximately 3 degrees.
External links