Answer:

Introduction:
Coarse aggregates are an essential component of concrete as they occupy a significant volume. They provide strength and stability to the concrete structure. The amount of cement paste required for a given quantity of coarse aggregate depends on the shape and surface texture of the aggregate.

Explanation:

Rounded Aggregate:
Rounded aggregates have a smooth and rounded shape. They are naturally occurring river gravels or crushed aggregates that have been subjected to wear due to water action. The rounded shape of these aggregates reduces the surface area in contact with the cement paste. As a result, less cement paste is required to coat the aggregate particles. This reduces the overall amount of cement paste needed in the concrete mix.

Irregular Aggregate:
Irregular aggregates have an irregular shape with sharp edges and corners. They are typically crushed rocks or artificially produced aggregates. The irregular shape of these aggregates increases the surface area in contact with the cement paste. This necessitates a larger amount of cement paste to adequately coat and bond with the aggregate particles. Therefore, irregular aggregates require more cement paste compared to rounded aggregates.

Angular Aggregate:
Angular aggregates have sharp and angular edges. They are usually obtained by crushing rocks or artificially produced aggregates. The angular shape of these aggregates also increases the surface area in contact with the cement paste. This leads to a higher demand for cement paste to adequately cover and bond with the aggregate particles. Therefore, angular aggregates require more cement paste compared to rounded aggregates.

Flaky Aggregate:
Flaky aggregates have a flat and elongated shape. They are obtained by crushing rocks or artificially producing aggregates. The flat and elongated shape of these aggregates results in a larger surface area in contact with the cement paste. This leads to the requirement of a larger amount of cement paste to adequately coat and bond with the aggregate particles. Therefore, flaky aggregates require more cement paste compared to rounded aggregates.

Conclusion:
In conclusion, rounded aggregates require the minimum amount of cement paste compared to irregular, angular, and flaky aggregates. The rounded shape of the aggregates reduces the surface area in contact with the cement paste, resulting in a lower demand for cement paste.