Coarse Aggregate and its types and uses

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    Coarse aggregate is the material that gives strength to the concrete. But so many of you may question then what the cement does. The cement is only the binding material it binds the Coarse and Fine aggregate to solid concrete. The Nature and Type of the course aggregate determine the strength and workability of the concrete. The Particle that was retained by the 4.75mm sieve (No.4) was known as Coarse aggregate.

General instruction before concreting in Project

    If you decide to make concrete on the Project site make sure your coarse aggregate is damped with water. Because coarse aggregate absorbs 5% of their surface area of water if they are dry. so when you put dry coarse aggregate into the concrete it absorbs the water and produces cracks in the concrete. So it is better to soak up your aggregate before producing concrete with it.

Types of Coarse aggregate

    The Nature and type of the coarse aggregate directly depend on the parent rock. Let's take for example coarse aggregate was produced with limestone as well as granite. But granite is harder than limestone hence granite coarse aggregate is used. The Coarse aggregate we classified based on the criteria below.,

1. Based on Shape
2. Based on Size

Based on Shape

    The shape of the coarse aggregate is very important, based on the nature of the parent rock and the crusher the Coarse aggregate may be Rounded, angular, or irregular.

• Rounded aggregate - This aggregate has a very low surface area and hence very low water and cement requirement. But the bonding makes were very weak with cement hence it reduces the strength of the concrete.
• Angular aggregate - This aggregate has a high surface area and hence requires more water and cement but the bonds that it creates in the concrete are very strong. So, Angular aggregate was majorly used in Concrete production. They Provide 10-20% more compressive strength.
• Irregular aggregate - These aggregate has more or less the same properties as angular aggregate but if they are more irregular, flaky, or too elongated it may lead to segregation of concrete which will reduce the strength of the concrete.

Based on the Size

    The Size of the aggregate is important when it comes to Reinforced Cement Concrete(RCC). Because the size of the aggregate that we select for the concrete needs to be small enough to enter into the space between the reinforcement. So Specific sizes of aggregate were used for specific structural member concrete.

    The Size varies from 10mm to 60mm, the reinforcement determines the size of the coarse aggregate. Hence in a standard procedure bigger sizes like the 40mm were used for PCC(Plain Cement Concrete) like flooring and concrete roads. Whereas 20mm was used for structural members like Columns, Beams, and slabs. There are some structural members called high steel structural members where the spacing between the reinforcement is very low so smaller 10 to 12mm aggregate were used for the concrete.

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