Aggregates

Aggregates are composed of geological materials such as stone, sand, and gravel and are used in virtually all forms of construction. They can be used in their natural state or can be crushed into smaller pieces.

The aggregates used for building are called “construction aggregates”. Aggregates are also used in agriculture, manufacturing, and other industries.

An indispensable ingredient

Aggregates are an indispensable ingredient in ready-mix concrete, asphalt, and mortar. Accounting for approximately 60% to 75% of ready-mix concrete’s volume, aggregates strongly influence concrete’s freshly mixed and hardened properties.

Aggregates not only increase concrete’s strength, but also can make the mix more compact, enabling applications such as weatherproofing and heat retention.

They can further contribute to concrete’s aesthetic qualities. For example, sand gives surface treatments their brightness.

A variety of applications

Our customers use our aggregates for a wide array of applications:

As a key component in the construction and maintenance of highways, walkways, parking lots, airport runways, and railways
For drainage, water filtration, purification, and erosion control
As fill material
For sand traps on golf courses, beaches, playing field surfaces, horse racing tracks, and related applications
To build bridges, homes, and schools

Aggregates are obtained from natural sand or sand-and-gravel pits, hard-rock quarries, dredging submerged deposits, or mining underground sediments. For more information about how aggregates are extracted, view our animated process.

Types of Aggregates

Crushed Stone and Manufactured Sand

These products are obtained by mining rock and breaking it down to a preferred size. In the case of manufactured sand, the product is obtained by crushing rock to the selected shape or texture, ensuring product and project specifications are met. Sources of crushed stone can be igneous, sedimentary, or metamorphic.

Gravel

Gravel deposits are produced through a natural process of weathering and erosion. It can be used for roads, for concrete manufacturing, or for decorative purposes.

Sand

Sand occurs naturally and is composed of fine rock material and mineral particles. Its composition is variable depending on the source. It can be used for roads, for concrete manufacturing, or sanitation.

Recycled Concrete

Recycled concrete is created by breaking, removing, and crushing existing concrete to a preferred size. It is commonly used as a base layer for other construction materials because it compacts to form a firm surface.

How we extract aggregates

How a rock quarry works

Rock quarries usually operate for at least 30 years and are developed in distinct benches or steps. A controlled explosion is normally used to release the rock from the working face. It is then transported by truck or conveyor to a crusher, where it goes through a series of crushing and screening stages to produce a range of final sizes to suit customers’ needs.

Just enough explosive is used in blasting to break the rock from the face. A powerful excavator loads the rock into dump trucks for delivery to the primary crusher.

Crushing

Powerful hammers or metal jaws within the primary crusher break the rock down. Rock passes through a series of screens that sift it into different sizes. It may also pass through further crushing stages.

Dry stone is delivered by road or rail from the quarry.

How sand and gravel quarry works

Sand and gravel quarries are much shallower than rock quarries and are usually worked and restored in progressive phases. This minimizes the area exposed for quarrying at any time and limits the period the land is out of use for other productive purposes.

Sand and gravel quarries are pumped to allow them to be worked dry or operated as lakes with extraction below water.

A conveyor draws raw material into the processing plant, where it is washed to remove unwanted clay and to separate sand. Sand separated during processing is dewatered and stockpiled. Gravel then passes over a series of screens that sift the material into different sizes.

Processing separates the gravel into stockpiles in a range of sizes for delivery by truck.

How marine aggregates are extracted

A significant proportion of the demand for aggregates is satisfied from river, lake, and sea beds. Our marine resources are an increasingly important alternative source of aggregates. Marine aggregates play an important role in replenishing beaches and protecting coastlines from erosion.

Satellite navigation may be used to position vessels precisely within licensed dredging areas. Vessels trail a pipe along the marine floor at speeds approaching 1.5 knots and use powerful suction pumps to draw sand and gravel into the cargo hold.

Dredged material is discharged at wharves and other marine facilities, where it is processed, screened, and washed as required.

Questions?

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