Definition - What does Aggregate mean?

Aggregate refers to the constituent of a composite material that resists compressive load and provides bulk to the composite material. It is mostly used in construction. Aggregates are inert materials like sand, gravel, crushed stone, slag and recycled aggregates. The aggregate of a composite needs to be much smaller than the finished item and should come in a wide variety of sizes for efficient filling. Aggregates account for between 60 to 75% of the total volume of concrete.

Corrosionpedia explains Aggregate

Aggregate is a component of composite materials such as concrete and asphalt concrete. Aggregate comprises large chunks of material in a composite, commonly coarse gravel or crushed rocks and fine materials. Aggregate comes in two types:

  • Fine aggregate – normally consists of sand, crushed stone or crushed slag screenings; most particles pass through a 3/8-inch sieve.
  • Coarse aggregate – consists of gravel (pebbles), fragments of broken stone, slag and other coarse substances; particles range between 3/8 and 1.5 inches in diameter.

Aggregate materials are used in building and construction for mixing with cement, bitumen, lime and gypsum to make concrete or mortar. Aggregate helps to provide volume, stability, resistance to wear or erosion, and many other desired properties to the final products. For example, cement is a brittle material in its pure state, but when used with aggregate, the durability and stability of the concrete significantly increases. The redistribution of aggregates after compaction often leads to strength gradients.

Most aggregates are extracted from mines. Aggregate provides reinforcement and adds strength to the overall composite material. Therefore, it is used as a stable foundation or as road/rail bases with predictable properties and inexpensive extenders to the high-cost cement or asphalt.

Aggregates should be clean, hard and free from absorbed chemicals or coatings of clay and other fine materials when added to cement for a good concrete mix. Without cleaning, aggregate can cause the deterioration of concrete quality. Recycled aggregates are also used as partial replacements of natural aggregates in composite materials.

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