Aggregate
In geology, an is a mass of mineral crystals, mineraloid particles, or rock particles. For example, dolomite is an aggregate of crystals of the mineral dolomite, and rock gypsum is an aggregate of crystals of the mineral gypsum.
A broad category of particulate materials composed of crushed stone, gravel, sand, or recycled materials like concrete that is used in construction and maintenance of roads, highways, and other infrastructure. These materials are sourced from natural deposits, such as riverbeds or quarries, or produced by crushing larger rocks, often limestone, granite, or basalt, to achieve a range of particle sizes. The key characteristic of aggregate is its ability to form a stable, load-bearing matrix when combined, providing strength, durability, and proper drainage for surfaces like rural roads, highway shoulders, or pavement bases. Specifications, such as those from the Iowa Department of Transportation, define gradations—size distributions from coarse to fine to ensure the material compacts well and resists wear under traffic and weather conditions.
Aggregate serves a critical role in road construction and maintenance by creating a solid foundation or surface layer that distributes vehicle loads, prevents rutting, and manages water runoff. For example, in the rural mid west, limestone-based gravel aggregate is commonly used for granular surfacing, where a mix of coarse and fine particles binds together to form a drivable surface while allowing water to permeate, reducing erosion. The term "aggregate" encompasses both the raw materials and their collective behavior, as the combination of sizes and shapes interlocks to enhance stability. Engineers select specific types—such as Class A crushed stone or Class C gravel—based on project needs, local availability, and standards like those set by transportation departments, ensuring the aggregate meets durability, gradation, and performance requirements for safe, long-lasting roads. See also Aggregate Size and Grade Reference.
As an intransitive verb to aggregate is to gather into a mass, sum, or whole. It can refer to the total of something. It can refer to gathering or collecting information. In technology it can refer to content from different sources on the Internet or can relate to Usenet.