A unique structure at Oracle, Arizona will house a re-creation of the earth's natural climates, life cycles, and systems completely sealed off from the surrounding atmosphere. Called Biosphere II, the 3.1-acre self-contained habitat provides 7 million cubic feet of laboratory space. Concrete provides the principal Biosphere structure, backing up the stainless steel liner at the bottom of the Biosphere and providing support for the space frame that roots the functional division.
Exacting specifications for the project challenged the principal concrete contractor, Diversified Design and Construction, Inc., Tucson, Arizona. All chemicals brought onto the site had to be evaluated and approved because of the possibility of contamination of the closed environment. Concrete curing compounds were ruled out, admixtures were limited, and galvanized metal was prohibited.
To obtain the smooth surfaces required as backup for the steel liner plate, Diversified selected a system of prefabricated metal wall form panels on which they were permitted to use the manufacturer's release agent or plain form oil as required. For areas where elevated slabs were formed, a truss-supported deck system that could be lowered and moved horizontally from one casting position to the next was used. Foundation concrete had a compressive strength of 3000 psi, and a 4000-psi mix was used in slabs and walls.