What is aggregate in concrete? Explain different types of aggregate in concrete.

In concrete, an aggregate is a material used in combination with cement and water to form the solid foundation of a structure. The aggregate is typically composed of various types of crushed rock or other materials that help to create the desired strength, durability, and overall composition of the concrete.

There are three primary types of aggregate used in concrete:

1. Coarse aggregate: This type of aggregate is typically larger than 4.75 mm in size and is usually made up of crushed stone or gravel. The coarse aggregate helps to provide bulk to the concrete, which is necessary to reduce shrinkage and cracking.
2. Fine aggregate: This type of aggregate is typically smaller than 4.75 mm in size and is usually made up of sand, crushed stone, or recycled concrete. The fine aggregate helps to fill the voids in the concrete and provide a smooth finish.
3. Lightweight aggregate: This type of aggregate is typically made up of materials like pumice or volcanic ash, and is used in situations where weight is a concern, such as in the construction of tall buildings.

In addition to these primary types of aggregate, there are also specialized aggregates that can be used for specific purposes, such as recycled aggregates, which are made from materials that have been previously used in construction, and decorative aggregates, which are used for aesthetic purposes in the construction of sidewalks, patios, and other outdoor areas.