Aggregate

Definition

Aggregate refers to inert particles such as sand, gravel, crushed stone, or expanded materials that are used in a concrete or plaster mixture. It also includes granular materials like iron blast-furnace slag. When combined with a cementing medium, these materials form hydraulic-cement concrete or mortar.

Purpose

The primary purpose of aggregate in concrete or mortar is to provide bulk, stability, resistance to wear or erosion, and other desired physical properties to the finished product. Aggregates contribute significantly to the strength, durability, and overall performance of concrete and plaster. They also help to control shrinkage and provide a more economical construction material by reducing the amount of cement required.

Examples of Use

1. Concrete Production: Aggregates are a major component of concrete, providing structure and strength. For example, a mixture of cement, sand, and gravel is commonly used for constructing buildings, roads, and bridges.
2. Mortar: In mortar mixtures, fine aggregates like sand provide the necessary consistency and workability for laying bricks and stones.
3. Plaster: Aggregates are used in plaster to create a smooth finish on walls and ceilings. Fine sand is typically used to provide a fine texture.
4. Road Construction: Crushed stone and gravel are used as base materials under roads and pavements, providing stability and load-bearing capacity.
5. Railroad Ballast: Aggregates such as crushed stone are used to form the trackbed upon which railroad ties and tracks are laid, providing drainage and stability.

Related Terms

1. Cement: A binding material used in construction that sets, hardens, and adheres to other materials to bind them together.
2. Concrete: A composite material made from a mixture of cement, aggregates (such as sand, gravel, and crushed stone), and water.
3. Mortar: A mixture of cement, lime, sand, and water used to bond bricks, stones, and other masonry units.
4. Plaster: A mixture of lime, cement, sand, and water applied to walls and ceilings to form a smooth or textured surface finish.
5. Hydraulic Cement: Cement that sets and hardens through a chemical reaction with water, capable of setting even underwater.

Notes

• The size, shape, and quality of aggregates can significantly impact the properties of the finished concrete or mortar, including strength, workability, and durability.
• Fine aggregates (e.g., sand) generally pass through a 4.75 mm sieve, while coarse aggregates (e.g., gravel, crushed stone) are retained on a 4.75 mm sieve.
• Proper grading and mixing of aggregates are crucial to achieve the desired properties in the final concrete or mortar product.
• Aggregates must be clean, strong, and free of harmful substances that could affect the setting and durability of concrete or mortar.
• Recycled aggregates from demolished concrete structures can be used in new concrete mixtures, promoting sustainability and resource conservation.