When the average person thinks about the construction industry, they are likely thinking of blueprints, heavy equipment, steel beams, new homes and even road construction crews. Construction aggregates are not usually top of mind.
Yet, as the most mined material in the world, aggregates such as sand, gravel and crushed stone are the backbone of the construction industry. They provide the foundation for roads, bridges, and buildings. Aggregates make up over 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, according to the National Stone, Sand & Gravel Association. Construction of the average home requires 400 tons of aggregate, and the average size school or hospital requires 15,000 tons. In other words, aggregates are truly the foundation upon which most of our society sits.
So, what exactly are aggregates?
Construction aggregate includes all types of construction material like sand, gravel, crushed stone, slag and geosynthetic aggregates largely used in the construction sector.
Aggregates are the base material for every construction job. Whether it is roads or railways, the aggregate materials help in building a strong foundation. They have uniform properties that build a stable foundation and bind cement and other materials together for long lasting results.
Additionally — because of the high hydraulic conductivity value of aggregates — drainage applications such as septic drain fields, retaining wall drains and roadside edge drains commonly use aggregates.
In 2020, according to the U.S. Geological Survey Mineral Commodity Summary, the total value of industrial minerals production was $54.6 billion. And of that, $27 billion was construction aggregates production (construction sand and gravel and crushed stone). Crushed stone was the leading nonfuel mineral commodity in 2020 with a production value of $17.8 billion and accounted for 22% of the total value of U.S. nonfuel mineral production.
What makes an aggregate a good aggregate?
Aggregates must have predictable, uniform, and consistent materials properties. Good-quality aggregate must be clean, hard, strong, have durable particles, and be free of absorbed harmful chemicals, coatings of clay, or other contaminates that can affect hydration of cement or reduce the paste-aggregate bond. Aggregates to avoid include:
- Those that are friable or susceptible to being split.
- Those with significant quantities of soft and porous materials.
- Certain kinds of “chert,” since they may have very low resistance to weathering and can lead to surface defects, called popouts.
Aggregates are only as good as their processing. They are mined, crushed, washed, and separated – and the success of each necessary step depends on the hardworking men and women in the industry who mine over 2 billion tons of aggregate in the United States every year.
Types of Aggregates
Limestone is an important source of construction aggregate due to its strength, versatility, and low thermal expansion. It is used in concrete production (producing a stronger concrete less prone to expansion); used in asphalt production (hydrated lime reduces cracking and stripping); road construction (as a road base due to its strength and durability); new construction (in home construction under concrete slabs that form the foundation for homes); erosion control (as riprap along rivers, streams, drainage and road edges); and soil stabilization.
Gravel is an important commercial product, with a number of applications. For example, globally gravel surfaces far more roads than concrete or asphalt. Gravel is used in road construction (commonly as a road base); new construction (to fill and stabilize the base of a project’s foundation); oil & gas pipeline (as access roads for pipeline maintenance); concrete production (gravel can lessen the cost of production in concrete making); and in erosion control (lining or filling drainage ditches and interceptor dikes).
Thanks to increased environmental laws, and the desire to keep construction costs down, recycled concrete aggregate has quite a following. Concrete from demolition sites is crushed, processed to remove metal such as reinforcing steel, and then screened to appropriate sizes. Crushed concrete is re-used as aggregate for fill, road base or even new concrete – many of the same applications as conventional crushed stone.
Recycling concrete features both cost savings and environmental benefits:
- Reduced disposal of concrete in landfill
- Conservation of natural resources
- Reduced cost for raw materials
- Energy savings from less processing and transportation
INDOT aggregates meet INDOT compliance for all roadway construction projects, and are CAPP (certified aggregate producers program) compliant. This ensures gradation consistency in all aggregate used for INDOT projects.
Today, many fields use iron and steel slag specifically for its unique characteristics. For example, road and railway construction and engineering all benefit from iron and steel slag. Iron and steel slag is highly regarded as a recycled material for reducing environmental impact. Slag is commonly used to cover driveways, to fill potholes, repair farm lanes, residential entrances, or yards. Hard and durable, slag makes a perfect aggregate for covering parking lots for long term results. When used for chip seal road projects, steel slag aggregate binds well and sets hard on the surface, extending the life of the road.
The term trap rock doesn’t describe a specific class of rock. It is a general term for various dark-colored, fine-grained, igneous rocks such as basalts and diabases. These materials are exceptionally hard and dense, with a low absorption. Construction applications such as concrete, macadam, and paving stones use trap rock. More technical applications use trap rock as ballast for railroad track beds to provide track stability, drainage and support of significant loads carried by railcars.
If you are looking for the right company that offers supply and transport facility for your construction business, contact Shoreline Aggregate today. Shoreline offers a wide selection of limestone, sand and gravel products for road construction, golf courses and sports field projects. We deliver aggregates throughout Illinois, Indiana and Michigan. Quarries are strategically located for quick delivery and competitive pricing.