As a leader in the construction materials industry, Knife River Corporation has long realized the environmental and economic benefits of recycling. The list of materials being recycled or beneficially reused in construction materials applications includes recycled asphalt pavement and asphalt shingles being used in hot-mix asphalt and base applications; fly ash, slag and silica fume being used as a cement-replacement material in ready-mixed concrete; and returned concrete and demolition concrete being used in recycled concrete aggregate and base applications.

Knife River always is looking for new and innovative ways to minimize waste and maximize resources at its operations and is continuing to research opportunities to increase the use of recyclable materials. At a number of facilities, Knife River has installed concrete reclaimer systems to recover and reuse concrete aggregate, a valuable and high-quality resource that is becoming scarce in some areas. Provided below are some examples that illustrate the environmental and economic benefits of recycling construction materials products.

Asphalt is 100 percent recyclable and, by weight, has long been one of the most recycled materials in the U.S. This is because asphalt recycling preserves landfill space, conserves aggregate resources, uses less energy and, ultimately, costs less for the consumer. Asphalt shingles contain essentially the same ingredients as asphalt — aggregate, asphaltic cement and mineral filler — and offer the same environmental and economic benefits of asphalt when reused in hot-mix asphalt or road-base applications.

In Knife River's ready-mix concrete operations, fly ash and other materials such as slag and silica fume are being used to replace cement because of their environmental and economic benefits, as well as engineering properties. Re-use of these materials preserves landfill space, conserves natural resources and results in a significant offset in greenhouse gas emissions when used as a cement replacement. For every ton of fly ash used in concrete, it is estimated that this results in the reduction of approximately one ton of carbon dioxide emissions.