SOLID WASTE/City uses glass cullets for road construction aggregate

As glass recycling has become more widespread, so has the problem of glass containers of different colors breaking and mixing together, leaving a cullet that cannot be mixed with any one color.

Oberlin, Ohio, population 8,800, has come up with an alternative use for mixed glass cullet accidentally generated in collection and processing of recyclables. The city stockpiles the cullet for use as a construction aggregate.

Glass accounts for about 70 percent of the weight of mixed rigids processed at Oberlin’s materials recovery facility, run by Houston-based Browning-Ferris Industries.

City officials first determined that glass cullet does meet many of the construction aggregate criteria (for example, it is porous, nontoxic, non-reactive and strong in compaction).

Officials then developed a proposal for the Ohio Department of Natural Resources’ Division of Recycling and Litter Prevention to help fund the reconstruction of a section of street using the cullet as the sub-base.

The city hired R & R International, Akron, Ohio, to run engineering tests on the composite material to develop specifications for its use in this application.

A literature search identified Seattle-based Clean Washington Center as an organization that has conducted extensive research on the use of glass as a construction aggregate. The Washington Department of Transportation has used mixed glass cullet for construction purposes such as wall backfill or drainage channel aggregate, according to Bob Kirby of the Clean Washington Center, but Washington’s recyclers do not generate enough volume for use in state highway projects.

After learning of Washington’s experience, Oberlin conducted Toxicity Characteristic Leachate Procedure testing to satisfy the requirements set by the Ohio Environmental Protection Agency’s Division of Surface Water for a beneficial use permit. Three random tests confirmed the absence of any problems caused by heavy metals, volatile organics and airborne dust.

Although mixed cullet has been used as a fill or base material in a number of applications, its use on a public street had not been previously documented when Oberlin awarded a contract for the reconstruction of a 675-foot section of street to Asphalt Sealers, Amherst, Ohio.

As of early March, the company had installed stormwater lines, concrete catch basins and manholes.

Application of the sub-base — 30 percent mixed glass cullet (about 125 tons) mixed with 70 percent limestone — has gone smoothly, and the material has been compacted. Curbs and paving will be installed as weather permits in the early spring.

The 125 tons used in the road project is approximately equal to the amount of glass recovered at curbside in Oberlin in one year.

“We believe the time is right for an industrywide recognition of the potential use of this material by the heavy construction and road construction industries,” says Jeffrey Baumann, Oberlin’s recycling coordinator.