Bulletin—127 Adobe, Pressed-Earth, and Rammed-earth Industries in New Mexico

By E. W. Smith and G. S. Austin, 1989, 60 pp. 7 tables, 91 figs., glossary. (superseded by Bulletin 159)

This report provides a survey of the soils, equipment, and techniques used today in NM to make adobe bricks, pressed-earth blocks, and rammed-earth walls. Many photos illustrate the ways in which soil, water, and stabilizers are combined to mold the earthen building materials into attractive, durable dwellings. Problems with earthen construction in radon-prone and seismically active areas are addressed. This report also contains a useful summary of soil mineralogy, thermal properties, preservation methods, physical-strength and water-resistance tests, and the current terminology used in the earthen industries.

NM continues to be the largest producer and user of adobe bricks and pressed-earth blocks in the nation. During field investigation and sampling in NM in 1987-1988, 33 commercial adobe-brick producers, 28 companies with pressed-earth-block machines, and 2 rammed-earth contractors were located. A significant number and variety of pressed-earth-block machines were in use; the gasoline- and diesel-powered machines were being made by five active NM manufacturers. In 1987, 3,124,000 adobe bricks and 642,000 pressed-earth blocks were produced. A breakdown on the types of adobe bricks produced in 1987 shows that 20 adobe-brick producers made 849,000 traditional adobe bricks, which sold for 21-40¢ per brick; 2,110,000 semistabilized adobe bricks, which sold for 30-35¢ per brick; and 165,000 stabilized adobe bricks, which sold for 59¢ per brick. The 642,000 pressed-earth blocks, largely made without stabilizers, sold for 25-35¢ per block.

During sampling, various tests were made on all types of adobe bricks and pressed-earth blocks. Mineralogy and particle-size analyses of the clays and soils, performed at the NM Bureau of Mines and Mineral Resources, show that soil materials used in the adobe-brick and pressed-earth-block industries contain more sand ± size particles than previously reported. Physical-property tests on selected adobe bricks and pressed-earth blocks, preformed at the United Nuclear Rock Mechanics Laboratory, NM Institute of Mining and Technology, show that the adobe bricks and particularly the pressed-earth blocks have high physical strength and in all cases meet or surpass the specifications and requirements of the NM Building Code.

The characteristics of the soils, the techniques of production, and the examples of earth-constructed buildings that are detailed in this report show that adobe bricks, pressed-earth blocks, and rammed-earth walls make energyefficient, durable, attractive dwellings. If problems in radon-prone and seismically active areas are properly recognized and controlled, then earth-constructed buildings are no more dangerous than homes constructed with other materials.