Production of compressed-earth-blocks -- Habitat for Humanity Int'l 1

Production of compressed-earth-blocks

By Minor Rodríguez

Since June 2005 Habitat for Humanity Mexico has incorporated into its work methodology the production of compressed-earth blocks—a type of improved adobe. The blocks are made with a lime hardpan (called tepetate in Mexico), cement, chalk and water. Block production takes advantage of traditional techniques, while increasing resistance and quality through modern technology.

Production and use of compressed-earth-block walls has also begun in Honduras in the local Copán office, where the material has long been part of the zone’s cultural and architectural heritage.

Benefits

The development of this construction technology and its application in home building has yielded many benefits for participating communities, such as:

Launch of a production project:
The Los Tuxtlas affiliate, in the Mexican state of Veracruz, acquired and installed compressed-earth-block-production machinery. The facilities employ trained, qualified staff and produce 51,300 blocks per month for use in Habitat homes. Each Habitat home (39 square meters) requires approximately 1,700 compressed-earth blocks. Unused blocks are sold on the local market at preferential prices.

Process mechanization:
The mechanization of the compressed-earth-block process facilitated large-scale production and higher quality blocks that cost less to produce. An automated production line was acquired, including a crusher, sieve, mixer, mix transport belt and the main cutter, which produces blocks in 10 x 15 x 30 cm molds.

In addition to water, which keeps it moist, the mix is composed of the following proportion of materials:

Clay and lime (tepetate)

six 5-gallon buckets

Sand

one 5-gallon bucket

Cement

half of a 50-kg sack

Chalk

half of a 25-kg sack

There are three types of blocks: solid, two-core and U-shaped two-core. The two-core blocks can be reinforced with vertical 3/8” rebar and are suitable for pipe installations, and U-shaped blocks can be used with horizontal reinforcement.

On average, an eight-hour workday produces 2,000 to 2,400 blocks. Exceptional outputs can reach up to 3,000 blocks.

Cost savings compared to masonry walls:
Considering the basic mix proportions for compressed-earth blocks, there is a savings of 15 percent to 20 percent per square meter over sand-cement blocks and traditional bricks. This is largely attributable to the cost of tepetate and cement in the zone.

Test blocks were made from a mix in which cement was substituted by chalk. To date, the major observed difference is the drying time: up to 40 percent more. Furthermore, testing revealed a compression strength of 45 kg/cm2, which meets the regional quality standards.

Better insulation properties:
Compared to traditional blocks—made from a sand-cement base or mud bricks—compressed-earth blocks are better suited to extreme climates. This guarantees much more comfortable and appropriate temperatures inside homes.

More attractive houses:
Buildings in several communities in Mexico and Honduras are often gray-looking because of the sand-cement-based construction materials used. Compressed-earth blocks, in contrast—thanks to an inexpensive and ecologically friendly sealant—create a durable and pleasant-looking wall.

Resistance to change

It was not easy to convince participating families to switch to this innovative technology. It required extensive communication efforts and persuasion, but satisfaction levels are now very high.

Minor Rodríguez (mrodriguez@habitat.org) is project manager for HFH in Latin America and the Caribbean. This article was based on information provided by the architect Juan Carlos Sapién, construction manager for HFH Mexico.