NEW METHODS
Right: Completed Binishell pneumatic building
Below: A workman controls the blower unit which inflates the neoprene sheet to lift the concrete
BALLOON FORMWORK FOR CONCRETE SHELLS
AN
N Italian architect, Dr. Dante Bini, has patented a construction tech- nique for thin-shell habitable domes by which an unreinforced sheet of neoprene synthetic rubber is raised pneumatically to form a mould for the fresh concrete.
This "off-the-ground" method raises new design possibilities and consider- ably reduces construction time costs. The air-tight flexible neoprene membrane is anchored to a peripheral foundation. Steel mesh reinforcement and concrete mix are placed over the sheet and the entire assembly is raised to the desired height by blowing air under the membrane.
The steel mesh, in addition to rein- forcing the concrete and controlling the bubble growth, keeps the mix from sliding off.
Self-supporting
Before and after inflation, the con- crete is settled by means of a vibrator. The thin reinforced shell cures within a short period and is self-supporting when the neoprene sheet is deflated and removed.
Insulation material can be evenly adhered to the dome's interior by re-inflating the membrane which ap- plies the necessary pressure. Open- ings for doors, windows, extensions and design are simply cut into the bubble with rotary saws.
The Binishells technique is appli- cable to the construction of light- weight vault structures over circular, square, rectangular or other shaped bases.
It is unique in that it requires no formwork, scaffolding, lifts or cranes, and less time and labour than con- ventional building methods. Only 30 minutes are required, for example, to raise a dome of 5cm. wall-thickness and 30m. dia., enclosing a volume of 4,000 cu. m. with a surface area of over 700 sq. m.; eight workmen are sufficient to handle these operations.
The sheet of Du Pont neoprene synthetic rubber has high elasticity and resistance to abrasion, and can be reused many times. It has an edge reinforced with nylon fabric for
Cross sections showing construction se- quence
attachment to a specially designed peripheral base ring. The membrane varies in thickness between 2.5 and 4mm.
Binishells are already used in Italy, where they have undergone extensive structural tests. The technique allows an almost unlimited number of dome designs for a variety of purposes, in- cluding homes, offices, motels, ware- houses, and sports centres.
3
section: 0=ground;
4
2 1
0
1=neoprene
Cross membrane; 2=steel mesh; 3-concrete mix; 4=waterproofing film
Far East BUILDER, June 1968.
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