Q: Counterweights for cranes must often fit a small volume. Sometimes a counterweight of concrete with a density of 150 pounds per cubic foot is not heavy enough. Is it possible to make concrete of various higher densities tailored to meet the volume requirements?

A: The ingredient of concrete that contributes most to its density is the aggregate because there is more of it than anything else. Most common aggregates have densities of about 162 pounds per cubic foot and when mixed with cement and water produce concrete that may have a density of about 150 pounds per cubic foot. The standard way of increasing the density of the concrete is to use heavier aggregate. Some examples of high aggregate density and resulting concrete density are:

Aggregate density, pounds per cubic foot
Concrete density, pounds per cubic foot

limonite

212-287
180-210

barite

250-275
220-230

lmenite, hematite or magnetite

263-300
210-260

ferrophosphorus

363-395
280-330

Trial mixes should be made if it is necessary to determine the exact volume needed to produce a specified weight.