Construction Aggregates 101: What They Are (and Why They Matter)

Mon August 31, 2020 - National Edition
Sara Feuling, AEM Director of Construction



Aggregates are often overlooked when we talk about the construction industry today. They are not appealing. They are not glamorous. They are just rocks after all.

That said, aggregates are — quite literally — the building blocks of our society. Aggregate production dates back to the Roman Empire, and it has been critical to the growth of our world ever since.

Aggregates are the most basic material used in construction. They provide the foundation for roads, bridges, and buildings, while also making up more than 90 percent of an asphalt pavement and up to 80 percent of a concrete mix.

On average, 38,000 tons of aggregates are necessary to construct one lane mile of interstate highway. Construction of the average home requires 400 tons of aggregate, while the average size school or hospital requires 15,000 tons.

Every state and roughly three-quarters of the nation's counties are home to an aggregate operation, producing nearly 2.4 billion tons of material annually, valued at more than $25 billion.

That's a huge impact for some rocks.

In partnership with the National Asphalt Pavement Association (NAPA) and the National Sand, Stone and Gravel Association (NSSGA), AEM will bring World of Asphalt and AGG1 to Atlanta, Ga., in March 2021.

What Are Aggregates?

Aggregates are raw materials that are produced from natural sources and extracted from pits and quarries, including gravel, crushed stone and sand. When used with a binding medium, like water, cement and asphalt, they are used to form compound materials, such as asphalt concrete and Portland cement concrete.

In 2018, according to the U.S. Geological Survey Mineral Commodity Summary, 75 percent of the 1.4 billion tons of crushed stone produced was used in construction. Meanwhile, of the almost 1 billion tons of sand and gravel produced, 24 percent was used in road construction, 12 percent in asphalt and 44 percent in concrete.

Why Are Aggregates Important?

Not only are aggregates the building blocks of our society, they also are prevalent in our daily lives.

The average American requires roughly 10,000 tons of aggregate per year. We would not have glass and plastic without sand, or pennies without zinc. Quartz gives us the silica for computer parts, limestone gives us the calcium carbonate for antacids. Aggregates also are used in the water filtration and purification process, as well as air filtration and purification.

What Makes An Aggregate a Good Aggregate?

Aggregates must have predictable, uniform and consistent materials properties. They must be dry and clean before they can be used.

Aggregates are only as good as their processing. They are mined, crushed, washed and separated. The successful outcome of each step, the processing of a good aggregate, depends on the success of the previous step. That success depends on the hardworking men and women in the aggregates industry.

Aggregates are here to stay. Today's machines are high performance, low maintenance and energy efficient machines. They allow the men and women in the aggregates industry to work quickly and safely while producing high quality materials. Dedicated to aggregates processing, AGG1 and the AGG1 Academy will showcase the machines and detail the processes that are, and will be, instrumental to the future of the aggregates industry.

This story also appears on Aggregate Equipment Guide.