Aggregates are inert granular materials, such as sand, gravel, or crushed stone, that are essential components of concrete. These materials are usually obtained from natural resources and can be used in their natural state or after undergoing mechanical processing, such as crushing, washing, and sizing. Currently, only recycled aggregates made from construction or demolition waste are recommended for use in new concrete construction. Aggregates have a wide range of applications, from building roads and aqueducts during the Roman Empire to creating high-strength concrete today.
The properties of aggregates vary depending on the type of material used and the purpose for which it is intended. For example, angular aggregates have better interlocking properties that contribute to the strength of the concrete, while recycled aggregates may differ in properties due to the design of the parent concrete. An example of an aggregate is the population of a country represented by its President. This is known as the aggregate population.
Before studying the properties of concrete, it is important to understand the aggregates that make up the majority of its volume. Recycled concrete aggregate (RCA) is made primarily from crushed concrete, while recycled aggregate (RA) contains substantial quantities of materials other than crushed concrete. Natural aggregate deposits known as pit gravel consist of gravel and sand that can be easily used in concrete after minimal processing. Samples can be sent to Europe for expert examination up to a total weight of 2000 tonnes, subject to payment of the required duties. To ensure that the aggregate is inert, it is manufactured from materials that have been tested and characterized according to European waste codes.
Some types of aggregates do not require any form of binding agent, such as those obtained as waste from some industrial and metallurgical engineering operations.