Why is the grading of aggregates important?

The grading of aggregates is crucial primarily because it affects the packing density and workability of the concrete. Properly graded aggregates can fill voids efficiently, which leads to a denser, stronger final product. If the aggregate grading is not optimal, it can result in an excess of void spaces that need to be filled with cement paste, which can negatively impact the concrete's strength and durability.

Additionally, grading influences how easily the concrete can be mixed and placed, which is referred to as workability. Well-graded aggregates contribute to a more cohesive mix that flows easily, can be worked into place without segregation, and has reduced chances of air voids.

While other options mention factors like the color of concrete, estimation of volume, and cost reduction, these are less significant in the context of grading's direct influence on the fundamental properties of the concrete mix. Therefore, achieving the right grading is key to ensuring that the final concrete performs adequately in its intended application.