From Bread to Blocks

Wheat starch may yield an inexpensive, lightweight aggregate for the concrete in tomorrow's homes. The wheat-based concrete could be used for roofing tiles, insulation, flooring, or soundproofing. Or it could be used to make insulated patios and sidewalks or the water-resistant backing for shower stalls in place of gypsum board.

Wheat starch, says ARS plant physiologist Gregory M. Glenn, can form an aquagel that acts as a durable aggregate for mixing with cement.

Glenn is conducting experiments with this unique use of wheat in his laboratory at the ARS Western Regional Research Center in Albany, California. And he will be working with an independent testing laboratory to check density, strength, and other key properties of the new concrete. He says wheat-based aquagels offer several advantages over some other lightweight aggregates. The aquagels would likely require less energy and labor to produce than aggregates derived from some other sources.

Glenn's tests indicate that the concrete's density "will remain uniform when poured to considerable depths. That's not the case," he says, "with lightweight concrete made from foams or foaming agents. If they're poured too deep, the weight of those mixes will compress the bubbles, yielding concrete that is denser at the bottom than the top."

The simple, straightforward method he developed begins with heating a mixture of wheat starch and water, then pouring it into a mold and cooling it to form a gel. Next, the gel is air-dried, making it hard, transparent, and brittle. It is then milled or ground into shiny white particles about the texture of coarse sand.

The little particles are soaked in water for several hours, then rinsed and drained. The result: a tough, rubbery aquagel aggregate. Composed of about 25 percent starch and 75 percent water, it won't disintegrate during the shearing action of the cement mixer.

With a few modifications, the process yields durable aquagels from other sources. Each aquagel can either serve as the sole aggregate used in a concrete or be mixed with other aggregates -- By Marcia Wood, ARS.

For more information on U.S. patent application serial number 08/ 515,502, "Aquagel- Based Lightweight Concrete," contact Gregory M. Glenn, USDA-ARS Western Regional Research Center, Albany, CA; phone (510) 559-5677.