How does the size of aggregate influence concrete strength?

The size of aggregate has a significant influence on the strength and workability of concrete. Larger aggregates typically contribute to the overall strength of the mix due to their ability to interlock and create a dense matrix, providing structural support. This helps in bearing loads and resisting various stresses that concrete may encounter.

On the other hand, smaller aggregates can lead to a smoother finish, which is often desirable in applications like flatwork finishing where aesthetics and surface smoothness are critical. The presence of smaller aggregates can fill the voids between larger aggregates, leading to a more cohesive mixture and potentially reducing the amount of paste needed.

This balance of aggregate sizes allows for optimizing the properties of concrete, depending on the specific requirements of the project. Therefore, the correct answer emphasizes the complementary roles of different aggregate sizes—larger aggregates for strength and smaller aggregates for finish quality.