Q.: Where can we obtain aggregate for making radiation shielding concretes?

A.: A source in the United States and Canada is:

C. and L. Roma International Inc. 3500 Vista Terrace Cincinnati, Ohio 45208 and 1171 Ambleside Drive, Suite 2206Ottawa, Ontario K2B 8E1

The company supplies aggregates suitable for shielding concrete or other heavyweight concretes such as required for counterweights. The aggregates are various iron ores. Some, such as goethite and limonite, have high water of hydration and range in specific gravity from 3.6 to 4.2. Magnetite, a magnetic iron oxide with a specific gravity of 4.4, is available. Hematite, a nonmagnetic iron oxide, is available at a specific gravity of 4.6. The aggregates are said to be available in all sizes from coarse to fine.For more information, see "Finding Special Aggregates," The Concrete Producer, July 1997.