Question: We are building a 2-story condominium complex with concrete slab-on-grade. For the second story a foamed type of lightweight concrete is being used over plywood for sound absorption between floors. Please send us information regarding the proper chemical to use to achieve the proper mix for the lightweight concrete. Since there are no lightweight concrete contractors in our area we are going to place the concrete ourselves. We need to know what chemical to use, how much to use and the correct slump. We will be placing the concrete with wheelbarrows, not pumping it.

Answer: Following are some companies which supply foams, foaming equipment and services needed for producing cellular lightweight concrete:

Elastizell Corporation of America

Box 1462

Ann Arbor, Michigan 48106

The Mearl Corporation

220 Westfield Avenue West

Roselle Park, New Jersey 07204 Waukesha Foundry Division

Abex Corporation

1300 Lincoln Avenue

Waukesha, Wisconsin 53186

They can supply concrete technical information.Insulating lightweight aggregate concretes made with perlite or vermiculite are also used for the same purpose. Information about perlite concrete can be obtained from:

Perlite Institute Inc.

45 West 45th Street

New York, New York 10036

and information about vermiculite concrete from:

W. R. Grace & Company

Construction Products Division

62 Whittemore Avenue Cambridge, Massachusetts 02140

Reader Response:

Lightweight concrete made with expanded shale, clay or slate aggregate produced by the rotary kiln method has also been used very successfully in an operation of this kind. If one uses a lightweight concrete weighing 90 pounds per cubic foot, a 1 1/2-inch thickness of this concrete weighs about 11 pounds. Concrete weighing 100 pounds per cubic foot and 1 1/2 inches thick weighs about 12.5 pounds. When using expanded shale, clay or slate lightweight concrete, one can do the job without specialty contractors because these expanded lightweight aggregate concretes are mixed and handled in the same way as normal weight concrete.The Expanded Shale Clay and Slate Institute, 4905 Del Ray Avenue, Suite 210, Bethesda, Maryland 20014 can supply information and answer inquiries relating to the uses of rotary-kiln produced expanded shale, clay or slate aggregates and to the properties of concretes made with them. The Institute has members throughout the United States, Canada and several foreign countries who would be able to assist contractors on this subject.

Harry C. Robinson

Managing Director

Expanded Shale, Clay and Slate Institute.