Alaska's Unnatural Resources: Recycled and reused materials in construction.

Author:Shipe, O'hara

Construction projects can have a significant impact on the environment. To illustrate, it is estimated that the global cement industry contributes approximately 5 percent of global carbon dioxide emissions. During the three-step production process required to create cement, combined minerals are crushed into three-inch pebbles before being sent to a kiln heated to 1,500 degrees Celsius (it is during this process that harmful carbon dioxides are released). The resulting material is called clinker. Once the clinker is cooled, it is ground into a super-fine powder and mixed with either gypsum to produce Portland cement or lime to produce masonry cement.

According to the US Environmental Protection Agency, the United States is the world's third largest cement producer, with production occurring in thirty-seven states. Alaska is one of nine states equipped to grind finished clinker into usable concrete or cement.

Cement Is Necessary, Environmental Contamination Isn't

Because cement is essential to the production of concrete, a primary building material for the construction industry, ceasing concrete production isn't a solution. Instead, many environmentally-minded individuals and businesses search for ways to reduce waste or repurpose already manufactured products.

Recognizing the potential to reuse concrete as a building aggregate, Alaska's Central Recycling Services (CRS) and sister company Central Environmental Inc. (CEI) combined forces to offer grinding services to local contractors. The result is an aggregate that can be used for a variety of projects. Smaller pieces of concrete can be used as gravel for new construction projects. Sub-base gravel can be laid down as a base for fresh concrete or asphalt. Uncontaminated recycled concrete can also be crushed and used as dry aggregate for brand new concrete. Finally, well-graded concrete can be provided as a substitute for landscaping stone or mulch.

CRS's founders have been working in construction and demolition for the past twenty-five years, but according to Civil and Environmental Engineer Donna Mears, the company itself has been in operation for the past decade.

"About ten years ago we demolished Clark Middle School, and the Anchorage School District and the architect requested that we do material recycling to meet LEED standards. Recycled asphalt, pavement, and concrete crushing is something that happens a lot, so we're not the only game in town for that, but we have pivoted to be able...

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