Glass containers that are brown, green, and clear are commonly recycled in Minnesota. The majority of this glass is recycled back into new containers to package food and beverages. However, many companies and counties are exploring alternative recycling options for post-consumer glass.
Many Minnesota counties have used reclaimed glass as aggregate. While many different applications have been demonstrated in Minnesota and other states, the use of 10% blend for road base is the most common, well-proven and safe.
Minnesota Department of Transportation
The Minnesota Department of Transportation (MnDOT) developed a specification for recycled aggregates for use in road base: Specification 3138: Aggregate for Surface and Base Course. Class 7 provides for use of up to 10% reclaimed glass blended with other aggregate materials.
The specification is intended to incorporate recycled materials into one class of aggregate, making it easier for government entities to incorporate recycled content material into their contracts and to create consistency throughout the state with regard to aggregate quality. The scope of this specification also covers the quality of glass aggregates used in construction of dense graded bases. Class 7 may be made from 100% recycled materials or blended with a combination of virgin and recycled aggregate. Glass aggregate is competitive with natural aggregate and in some cases can improve the quality of a sandy, virgin aggregate.
Reclaimed Glass Information Kit
This "tool kit" explains the basics of using reclaimed glass in the aggregate mix for roadbed construction. Technical information is supplemented with resources for implementing a glass project, including case studies, references, and a statewide list of reclaimed glass suppliers.
This project to promote the use of reclaimed glass in base aggregate was a collaborative effort: Minnesota Local Road Research Board, the Minnesota Local Technical Assistance Program (LTAP) at the University of Minnesota's Center for Transportation Studies, the Minnesota Department of Transportation, and the former Office of Environmental Assistance.
Success story: Ramsey County
For several years, the Ramsey County Public Works Department experimented with different applications of glass in cooperation with Super Cycle of St. Paul. Ramsey County found glass to be an excellent aggregate amendment and has actively pursued new and different engineering applications for the material. Ramsey County has used glass in shouldering, a 10% mix in base, asphalt and a 100% use in base.
Ramsey County Demonstrations of Recycled Glass as an Aggregate Supplement [Dan Krivit & Associates (1999)]
A 7-minute video is available about this project: A Glass Recycling Alternative: a Highway Re-Construction Project in Otter Tail County. To borrow, contact the MPCA's Learning Resource Center, 651-296-6300 or 800-657-3864 toll free.
Otter Tail County's Highway Engineer, Rick West, made an early commitment to use recycled glass for use in a road resurfacing project in the county. In 1996, the county recycling program began stockpiling glass containers collected for recycling. In 1997, because the glass was dedicated to use in highway construction, the glass recycling program was expanded to include non-container glass, including dishes, window glass and glass cookware.
The project to re-construct a four-mile section of Highway 74 began in September 1998. Bid specifications required the contractor to include a 10% blend of recycled glass (by weight) in the aggregate used in the road base. The County Solid Waste Administrator, Mike Hanan, and the County Engineer, Rick West, worked closely with the contractor to ensure that the material used in the base course was clean and of high quality. Engineers determined that the glass could be crushed as it was blended with gravel. The finished product was a MnDOT Class 5 aggregate base with a one-inch maximum particle size. Some salvaged asphalt pavement was also included in the blend.
This mixture performed well during construction, with no need for special equipment. The county has found that this use is an excellent way to recycle glass locally, avoiding the high transportation costs and color separation of the glass required for recycling back into container glass. "We will do these kinds of things (aggregate amendment) until the market says that trucking glass to be used for new glass makes sense," says West.
Public Works Department
Otter Tail County Courthouse
419 South Court Street
Fergus Falls, MN 56537
Other information sources for glass as aggregate
Conducts research and outreach on environmental and material properties of recycled materials and their wise and appropriate use in highway construction.
Minnesota LTAP conducts workshops and seminars, conferences, customized training, demonstrations, and distance learning to improve the skills and knowledge of local transportation agencies. The goal of Minnesota LTAP is to foster a safe, efficient, and environmentally sound transportation system.
- Dan Krivit, Dan Krivit & Associates
977 W Nebraska Ave, St. Paul, MN 55177-3328
phone: 651-489-4990 email: firstname.lastname@example.org
- Gene Isakson, PE
4 Marie Lane, St. Peter, MN 56082