Aggregate / Construction
Natural aggregate is one of our most abundant, accessible, and widely used natural resources. Construction aggregate consists of sand, gravel, and crushed stone.
It is primarily used by highway and building construction industries.
Wyoming’s energy industry also requires large amounts of aggregate for the construction of well pads, wind generator bases, and access roads to industrial sites.
Aggregate Industry Facts
More than 2.5 billion tons of aggregate (construction-grade crushed stone [1.5 billion tons] and sand and gravel [1 billion tons]) were produced for every person in the United States in 2017 (based on U.S. Geological Survey [USGS] Mineral Industry Surveys production and U.S. Census population estimates).
It takes 400 tons of aggregate to build the average home in America, according to the National Stone, Sand and Gravel Association.
Construction of one mile of interstate highway is estimated to require 38,000 tons of aggregate, according to the National Stone, Sand and Gravel Association. The Wyoming Department of Transportation indicated a mile of Wyoming highway may contain more than double that amount, depending on the aggregate quality, native soils, and use of the road.
Aggregate Geology
Wyoming has a variety of geologic landscapes providing plentiful aggregate resources including the following:
Sand is acquired from alluvial floodplains along stream and river valleys as well as from extensive dune sands. Windblown sand deposits occur between the western Green River Basin through Wyoming and into western Nebraska.
Sand and gravel deposits occur on the tops of benches and terraces along mountain flanks. The quality of these deposits varies greatly, as terraces may contain areas of caliche. Caliche-coated gravels do not bind well with asphalt or cement.
Glacial gravels are not widely used due to location in national parks and national forests. However, they are occasionally used for local road construction projects.
Older gravels from poorly consolidated conglomerates are a source of “natural gravel" that are useful if they can be extracted without blasting or cutting.
Limestone is exposed along the flanks of mountain ranges and is a significant source of crushed stone. Limestone is the preferred rock for highway construction.
Granite is another source of crushed stone. Specifically, quartzofeldspathic gneiss is mined in the largest aggregate quarry in Wyoming, west of Cheyenne. Railroad ballast is one of the quarry’s main product, simply because the foliation in the gneiss allows the rock to have a 2:4:6 dimensional ratio, which is a requirement of certain types of railroad ballast.
Clinker, also called scoria or baked and fused rock, is formed by the burning, baking, and melting of strata overlying burning coal beds. Clinker is found and used extensively in the Powder River Basin (PRB), where no other aggregate sources exist. It is used for the sub-base of roads and for well-pad construction. Although it is abundant in the PRB, clinker is not as durable and breaks down more easily than sand and gravel.
Mine tailings are a unique source of gravel in the South Pass mining district and are used locally for road building.
Aggregate Recycling and Renewal
Recycling of aggregate, primarily re-crushing concrete and asphalt, is economically viable in many situations. The Wyoming Department of Transportation recycles and turns into new pavement nearly all the asphalt and concrete pavement they remove from Wyoming’s roadways. There are also various processes for creating lightweight synthetic aggregate from waste products such as coal ash and sewer sludge. Recycled aggregate sources help relieve shortages and reduce landfill waste.
References
State of Wyoming Department of Workforce Services, 2021, Annual Report of the State Inspector of Mines of Wyoming: State Inspector of Mines of Wyoming.
State of Wyoming Department of Revenue, 2021, State of Wyoming Department of Revenue Annual Report: State of Wyoming Department of Revenue Annual Report, 79 p.
USGS Minerals Industry Surveys, 2022, Crushed stone statistics and information: United States Geological Survey Quarterly Reports.
Contact:
Patty Webber, patty.webber@wyo.gov