Modern production

The advent of modern blasting methods enabled the development of quarries, which are now used throughout the world, wherever competent bedrock deposits of aggregate quality exist. In many places, good limestone, granite, marble or other quality stone bedrock deposits do not exist. In these areas, natural sand and gravel are mined for use as aggregate. Where neither stone, nor sand and gravel, are available, construction demand is usually satisfied by shipping in aggregate by rail, barge or truck. Additionally, demand for aggregates can be partially satisfied through the use of slag and recycled concrete. However, the available tonnages and lesser quality of these materials prevent them from being a viable replacement for mined aggregates on a large scale.

Large stone quarry and sand and gravel operations exist near virtually all population centers. These are capital-intensive operations, utilizing large earth-moving equipment, belt conveyors, and machines specifically designed for crushing and separating various sizes of aggregate, to create distinct product stockpiles.

Aggregate is needed for any kind of construction. Mineral aggregates will be used in ever-increasing quantities as long as economies remain stable. Roads, including these used to transport aggregate, require continual maintenance and rebuilding. Homes, offices, warehouses, shopping centers, and workplaces all require foundations composed of aggregate, as well as concrete footers, asphalt parking lots, manufactured bricks, blocks and poured walls. Corporations which specialize in mining and processing aggregates are likely to grow and consolidate. In fact, the purchase of small aggregate companies by large, global corporations is the dominant trend in the industry. As less-developed countries build their infrastructure, the worldwide demand for construction aggregates will continue to grow. This demand will increasingly be met by global aggregate companies such as Hanson Aggregates, Polaris Minerals, Martin Marietta Aggregates, Vulcan Materials Company, Lafarge, Oldcastle, Cemex, Samscreen and Perforated Screen Surfaces, Inc (PSSI).

According to the USGS, 2005 U.S. crushed stone production was 1.69 billion tonnes valued at $12.1 billion, of which limestone was 1,090 million tonnes valued at $7.49 billion from 1,904 quarries, granite was 263 million tonnes valued at $2.16 billion from 339 quarries, traprock was 130 million tonnes valued at $1.04 billion from 348 quarries, and the balance other kinds of stone from 597 quarries. Limestone and granite are also produced in large amounts as dimension stone. The great majority of the crushed stone moved by heavy truck from the quarry/plant to the first point of sale or use. According to the USGS, 2005 U.S. sand and gravel production was 1.27 billion tonnes valued at $7.46 billion, of which 294 million tonnes valued at $1.98 billion was used as concrete aggregates. The great majority of this was again moved by truck, instead of by electric train.

Currently, total U.S. aggregate demand by final market sector was 30%-35% for non-residential building (offices, hotels, stores, manufacturing plants, government and institutional buildings, and others), 25% for highways, and 25% for housing.