Construction aggregate

Aggregates are the most mined materials in the world,[1][2] being a significant part of 6 billion tons of concrete produced per year.

Self-binding aggregate refers to angular crushed material (quarrystone rubble) comprising a mixture of finer and coarser particles that interlock after being compacted.

Sources for these basic materials can be grouped into three main areas: mining of mineral aggregate deposits, including sand, gravel, and stone; use of waste slag from the manufacture of iron and steel; and recycling of concrete, which is itself chiefly manufactured from mineral aggregates.

These products include specific types of coarse and fine aggregate designed for such uses as additives to asphalt and concrete mixes, as well as other construction uses.

The invention of concrete, which was essential to architecture utilizing arches, created an immediate, permanent demand for construction aggregates.

Vitruvius writes in De architectura: Economy denotes the proper management of materials and of site, as well as a thrifty balancing of cost and common sense in the construction of works.

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.

Where neither stone, nor sand and gravel, are available, construction demand is usually satisfied by shipping in aggregate by rail, barge or truck.

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 due to the high cost of transportation relative to the low value of the product.

[8] 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.

Steel furnace slag sales in 2006 were for use in road bases and surfaces (51%), asphaltic concrete (12%), for fill (18%), and the balance for other uses.

In Bay City, Michigan, for example, a recycle program exists for unused products such as mixed concrete, block, brick, gravel, pea stone, and other used materials.

For example, Ring Industrial Group's EZflow[11] product lines are produced with geosynthetic aggregate pieces that are more than 99.9% recycled polystyrene.

This polystyrene, otherwise destined for a landfill, is gathered, melted, mixed, reformulated and expanded to create low density aggregates that maintain high strength properties under compressive loads.

Such geosynthetic aggregates replace conventional gravel while simultaneously increasing porosity, increasing hydraulic conductivity and eliminating the fine dust "fines" inherent to gravel aggregates which otherwise serve to clog and disrupt the operation of many drainage applications.

[14] The Waste and Resource Action Programme[15] has produced a Quality Protocol for the regulated production of recycled aggregates.