Compressed earth block

CEB technology has been developed for low-cost construction, as an alternative to adobe, and with some advantages. A commercial industry has been advanced by eco-friendly contractors, manufacturers of the mechanical presses, and by cultural acceptance of the method. In the United States, most general contractors building with CEB are in the Southwestern states: New Mexico, Colorado, Arizona, California, and to a lesser extent in Texas. The methods and presses have been used for many years in Mexico, and in developing countries.

The South African Department of Water Affairs and Forestry considers that CEB, locally called "Dutch brick" is an appropriate technology for a developing country, as are adobe, rammed earth and cob. All use natural building materials.[1] In 2002 the International Institute for Energy Conservation was one of the winners of a World Bank Development Marketplace Award for a project to make an energy-efficient Dutch brick-making machine for home construction in South Africa. By making cheaper bricks that use earth, the project would reduce housing costs while stimulating the building industry.[2] The machine would be mobile, allowing bricks to be made locally from earth.[3]

Various types of CEB production machines exist, from manual to semi-automated and fully automated, with increasing capital-investment and production rates, and decreased labor. Automated machines are more common in the developed world, and manual machines in the developing world.

• Minimal or no need for mortar, thus reducing both the labor and materials costs.
• Transport cost: Suitable soils are often available at or near the construction site.
• Strengths might exceed the ASTM standard for concrete blocks (1900 psi) in some instances. In India, the observed compressive strength and flexural strength of CSEB at 28 days of aging with 9% cement stabilization has been observed to be 3.2 MPa and 1 MPa respectively.[4]
• Non-toxic: like bricks, materials are completely natural, non-toxic, and do not out-gas
• Sound resistant: an important feature in high-density neighborhoods, residential areas adjacent to industrial zones
• Fire resistant: like bricks, earthen walls do not burn
• Insect resistant: like bricks, insects are discouraged because the walls are solid and very dense, and have no food value

• There is a wait-time required with this construction technique, because after the blocks are pressed, materials must dry.
• The mixture of the interlocking blocks must be consistent and just moist enough. If the mixture is too dry, it will collapse after it has been hydraulically pressed and if the mixture has too much water, it cannot be solidified.[5]
• There is also the risk of erosion from weather conditions such as winds or rain that could threaten the stability of the blocks.[6] Reinforcement using plaster might be required to ensure that wall is durable in weather conditions such as rain and wind.[7]
• Power is needed on-site for the compressing machines.[7]
• Workforce trained to produce and construct interlocking blocks is limited.[7]
• Being understudied, the durability of these blocks has not been seen in environments other than rural developments.[7]

CEB had very limited use prior to the 1980s. It was known in the 1950s in South America, where one of the most well-known presses, the Cinva Ram, was developed by Raul Ramirez in the Inter-American Housing Center (CINVA) in Bogota, Colombia. The Cinva Ram is a single-block, manual-press that uses a long, hand-operated lever to drive a cam, generating high pressure.

Industrial 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. France, England, Germany, South Africa and Switzerland began to write standards. The Peace Corps, USAID, Habitat for Humanity and other programs began to implement it into housing projects.

Completed walls require either a reinforced bond beam or a ring beam on top or between floors and if the blocks are not stabilized, a plaster finish, usually stucco wire/stucco cement and/or lime plaster. Stabilized blocks can be left exposed with no outer plaster finish. In tropical environments, polycarbonate varnish is often used to provide an additional layer of wet-weather protection.

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.

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)