How to Make Concrete Lighter While Preserving Its Integrity

Consult your architect, builder or your own notes to determine the maximum forces to which your concrete will be exposed. Use the minimum volume of concrete necessary to provide the support needed. Unnecessary additional concrete adds unnecessary weight. For example, if your architect states that 6 inches of standard mix concrete is required, use only 6 inches. Standard concrete weighs 150 pounds per cubic foot, so every additional inch of thickness on a 6 foot square slab will add 450 pounds of weight.

Use the lightest aggregate you can obtain. According to Benjamin A. Graybeal, Ph.D., head of the Federal Highway Administration's Structural Concrete Research Program, using lighter rocks results in a lighter concrete. For example, basalt and granite aggregates both weigh roughly 165 pounds per cubic foot, but limestone weighs 12 pounds less at 153 pounds per cubic foot. Using limestone rather than granite aggregate would cut more than a ton from the weight of a concrete retaining wall 6 feet high, 2 feet thick and 20 feet long.

Use non-aggregate filler in the concrete, such as foaming agents, vermiculite or aluminum powder that creates tiny gas bubbles as the concrete cures. Such mixes do not have the compressive strength of traditional mixes, but they may weigh as little as 35 pounds per cubic foot. As long as the mix strength exceeds the strength required for the construction project, its integrity will not be compromised. Using a mix weighing 35 pounds per cubic foot to create the example wall in Step 3 would result in a wall weighing less than one-quarter of the original weight.