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Construction aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, and crushed stone. As with other types of aggregates, it is a component of composite materials, particularly concrete and asphalt. Aggregates are the most mined materials in the world, being a significant part of the 6 billion tons of concrete produced per year.
Aggregate serves as reinforcement to add strength to the resulting material. Due to the relatively high hydraulic conductivity as compared to most soil types, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under building foundations, roads and railroads (aggregate base). It has predictable, uniform properties, preventing differential settling under the road or building.
Aggregates are also used as a low-cost extender that binds with more expensive bitumen to form asphalt concrete or with Portland cement to form concrete.
Self-binding aggregate refers to angular crushed material (quarrystone rubble) comprising a mixture of finer and coarser particles that interlock after being compacted. More recently, recycled concrete, steel and carbon fibres as well as geosynthetic materials have also been used as aggregates.
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. In addition, there are some (minor) materials that are used as specialty lightweight aggregates: clay, pumice, perlite, and vermiculite. Other minerals include:
In Europe, sizing ranges are specified as d/D, where the d shows the smallest and D shows the largest square mesh grating that the particles can pass. Application-specific preferred sizings are covered in European Standard EN 13043 for road construction, EN 13383 for larger armour stone, EN 12620 for concrete aggregate, EN 13242 for base layers of road construction, and EN 13450 for railway ballast.
The American Society for Testing and Materials publishes an exhaustive listing of specifications including ASTM D 692 and ASTM D 1073 for various construction aggregate products, which, by their individual design, are suitable for specific construction purposes. 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. State transportation departments further refine aggregate material specifications in order to tailor aggregate use to the needs and available supply in their particular locations.
Aggregate base is typically composed of crushed rock capable of passing through a 20-millimetre (3⁄4 in) rock screen. The component particles will vary in size from 20 mm down to dust. The material can be made of virgin (newly mined) rock, or of recycled asphalt and concrete. Base is used as a base course in roadways, as a base course for cement pads and foundations, and as backfill material for underground pipelines and other underground utilities. The base course is the sub-base layer of an asphalt roadway. Generally consisting of larger grade aggregate, spread and compacted to provide a stable base for further layers of aggregates or asphalt pavement. Aggregate base course is often referred to as ABC.
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Construction aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, and crushed stone. As with other types of aggregates, it is a component of composite materials, particularly concrete and asphalt. Aggregates are the most mined materials in the world, being a significant part of the 6 billion tons of concrete produced per year.
Aggregate serves as reinforcement to add strength to the resulting material. Due to the relatively high hydraulic conductivity as compared to most soil types, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under building foundations, roads and railroads (aggregate base). It has predictable, uniform properties, preventing differential settling under the road or building.
Aggregates are also used as a low-cost extender that binds with more expensive bitumen to form asphalt concrete or with Portland cement to form concrete.
Self-binding aggregate refers to angular crushed material (quarrystone rubble) comprising a mixture of finer and coarser particles that interlock after being compacted. More recently, recycled concrete, steel and carbon fibres as well as geosynthetic materials have also been used as aggregates.
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. In addition, there are some (minor) materials that are used as specialty lightweight aggregates: clay, pumice, perlite, and vermiculite. Other minerals include:
In Europe, sizing ranges are specified as d/D, where the d shows the smallest and D shows the largest square mesh grating that the particles can pass. Application-specific preferred sizings are covered in European Standard EN 13043 for road construction, EN 13383 for larger armour stone, EN 12620 for concrete aggregate, EN 13242 for base layers of road construction, and EN 13450 for railway ballast.
The American Society for Testing and Materials publishes an exhaustive listing of specifications including ASTM D 692 and ASTM D 1073 for various construction aggregate products, which, by their individual design, are suitable for specific construction purposes. 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. State transportation departments further refine aggregate material specifications in order to tailor aggregate use to the needs and available supply in their particular locations.
Aggregate base is typically composed of crushed rock capable of passing through a 20-millimetre (3⁄4 in) rock screen. The component particles will vary in size from 20 mm down to dust. The material can be made of virgin (newly mined) rock, or of recycled asphalt and concrete. Base is used as a base course in roadways, as a base course for cement pads and foundations, and as backfill material for underground pipelines and other underground utilities. The base course is the sub-base layer of an asphalt roadway. Generally consisting of larger grade aggregate, spread and compacted to provide a stable base for further layers of aggregates or asphalt pavement. Aggregate base course is often referred to as ABC.
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