What constitutes an Aggregate?

Tuesday, July 30th, 2013


What are aggregates? Aggregates are simply any collection of rocks. In the aggregates industry, these rocks are classified as crushed stone, sand, gravel, and slag. We use aggregates every day. Streets, bridges, roads, and sidewalks are made of concrete or asphalt which is mostly made up of aggregates combined with a binder that acts like glue. Concrete is used in foundations and basements for houses. Other buildings sometimes use concrete throughout their structures. But did you know that many items you use every day have aggregates in them? Your toothpaste has aggregates in it. Glass is made from sand, which is an aggregate. Minerals and aggregates are in plates, dishes, pots and pans, baby powder, household cleaners, makeup, medicines, paints, pencils, fertilizers, wallboard, and more including some of the foods you eat!

Sand is a widespread but highly variable resource in Indiana that was formed mostly by glacial actions of large ice sheets and then sorted by running water. Sand can be used as fill, or more often the coarser parts find use as components of concrete or asphalt pavement. Sand, a finer granular material, also is important in concrete and in making mortar, and in snow and ice control. Very fine-grained sand finds use in foundries to make molds, and also in sandblasting, glass-making, or even as golf-course sand.

Gravel: The term gravel applies to a range of particle sizes, rather than a specific rock or mineral type. Gravel is colored by the rock types present. It is a collection of rock particles that are at least .08 inches in diameter sizes, but may also include boulders over 10 inches in diameter. Gravel is loose rock that is often rounded in shape from being worn by water at some point. Gravel can be used alone as fill, for gravel roads, or residential driveways. Gravel can also be used as a component of concrete or asphalt pavement.

Limestone (crushed stone): Limestone is the primary rock type making up aggregate and is mined throughout Indiana. It is usually gray rock (but color can vary) consisting of at least 50% calcite. The texture can be coarse to very-fine grained. Whole fossils or fossil fragments are typically present in limestone. Indiana is probably best known for her dimension building stone. Indiana Limestone has helped construct such iconic buildings as the Empire State Building, the Pentagon, The Washington National Cathedral, and many venerable official, commercial, or religious structures. The more widespread and less uniform limestone in Indiana provide for excellent crushed aggregate, cement, chemical raw material, and for limited architectural uses.

Aggregates in Indiana

The facts below are current as of 2009. They were compiled by the Indiana Mineral Aggregates Association, Indiana Geological Survey, National Stone, Sand & Gravel Association and the U.S. Geological Survey. Special thanks to Kathryn Shaffer of the Indiana Geological Survey and Mary Foster, an industry researcher.

Download the Indiana Aggregate Facts brochure. (download link: IMAAFactsBrochure.pdf)

Would you like copies of the Indiana Aggregate Facts brochure to distribute or display? Contact us to request brochures.

Indiana Aggregates Quick Facts:

-Aggregates are produced from 241 surface and underground mines located throughout Indiana.
-Aggregate mining occurs in 79 of the 92 Indiana counties.
-The majority of aggregate plants in Indiana are family-owned and operate with 20 or fewer employees.
-Indiana ranked 10th nationally in crushed stone production and 12th in sand and gravel production in 2009.
-Approximately 28,603 lbs. of aggregate are required for each Indiana resident per year.
-83.3 million tons of crushed stone, sand and gravel were produced in Indiana in 2009.
-Indiana ranks 1st nationally in the production of air-cooled blast furnace and steel furnace slag. In 2009, 4 million tons were produced in the Hoosier state.
-Slag is used as the surface material at the Indianapolis Motor Speedway because its angular, sharp texture creates excellent traction and skid resistance.

What’s the Economic Impact?

The aggregate industry constitutes an integral segment of the nation’s economy. This $21.2 billion dollar industry supplies construction materials for the transportation industry, and more than 90% of aggregate production is used directly or indirectly by the construction industry.

Aggregate operations create attractive job opportunities and a strong tax base for local communities. Aggregates are essential construction materials for residential and commercial development, as well as for improvements to infrastructure projects such as roads, bridges, dams, hospitals, schools and water/sewer systems. Every $1 million in aggregate industry sales creates 19.5 jobs (National Stone, Sand & Gravel Association).

Indiana by the Numbers

-2,300 workers employed by the Indiana aggregate industry in 2009.
-$97,181,000 wages generated by the Indiana aggregate industry in 2009.
-$4,275,964 Indiana income tax generated by the Indiana aggregate industry in 2009.

The Industry & Environmental Stewardship

-A number of lakes resulting from aggregate excavation have been reclaimed to make excellent water recreational facilities. These lakes also aid in recharging the groundwater aquifers, providing sources of water for cities and towns.
-Many old aggregate mines are now parks, wildlife habitats, and sites for office complexes, apartments and housing communities.
-The aggregate industry and its partners work to recycle old concrete and asphalt pavement, crushing and sorting it like rock so that it can be reused.
-Limestone and dolomite are key ingredients for the removal of sulfur dioxide created when high-sulfur coal is burned in electricity plants. Indiana has several plants producing material for limestone scrubbers and other air-cleaning systems, providing Hoosiers with cleaner air to breathe.

Why is Indiana Transportation Infrastructure so Important?

-Between 65-70% of all freight is transported over our highways, which serve as connectors with water, rail, and facilities.
-About 80% of all Indiana aggregate is transported by truck, 18% by barge, and 2% by other transportation.
-One mile of two-lane concrete highway is 24 feet wide and 12 inches thick and requires 7,205 tons of aggregate materials to build.
-One mile of two-lane asphalt pavement is 24 feet wide and 14 inches thick and requires 10,300 tons of aggregate materials to build.
-Beginning in the 1950s, the Federal Highway Administration began working with the states to build the 42,800-mile Interstate Highway system in 49 states, plus additional roads in Alaska, the District of Columbia, and Puerto Rico.
-The United States has 3.9 million miles of roadway, of which 3.1 million miles are rural roads. The Interstate System accounts for only 1.2% of the total mileage of roads, but carries 22.8% of total travel.

Indiana’s road transportation system encompasses more than 93,000 miles of federal, state, and county roads.