What is Coarse aggregate in concrete? Explain in details with their size, shape and strength.

Coarse aggregate is a type of aggregate used in concrete that is larger than 4.75 mm in size. It is typically made up of crushed stone, gravel, or recycled concrete, and is used to provide bulk to the concrete mixture, which helps to reduce shrinkage and cracking. Coarse aggregates are typically classified based on their size, shape, and strength.

1. Size: The size of coarse aggregate is typically measured in millimeters, and it can range from 4.75 mm to several inches in diameter. The most common sizes of coarse aggregate used in concrete are 20 mm, 16 mm, and 12.5 mm.
2. Shape: The shape of coarse aggregate can also have an impact on the properties of the concrete. The most common shapes of coarse aggregate are rounded, angular, and cubical. Rounded aggregates are smooth and provide good workability, while angular aggregates are more jagged and provide better bonding between the aggregate and the cement paste. Cubical aggregates are a compromise between the other two shapes and provide good workability and bonding.
3. Strength: The strength of coarse aggregate is typically measured in terms of its compressive strength, which is the amount of pressure the aggregate can withstand before it fails. The compressive strength of coarse aggregate can range from 100 MPa to 300 MPa, depending on the type of rock or gravel used.

In addition to the above characteristics, there are other factors that can affect the properties of coarse aggregate, such as its density, porosity, and water absorption. It’s important to choose the right type of coarse aggregate for a particular concrete mixture, based on the desired properties of the finished product.