What impact do excessive fines in aggregate have on concrete quality?

Excessive fines in aggregate primarily affect the workability and increase the water demand of concrete. Fines are the very small particles within an aggregate that can fill the voids between larger particles. When there are too many fines, they disrupt the balance of the aggregate mix, leading to a higher surface area that requires more water for proper lubrication during mixing and placement.

This increased water demand can lead to several issues, such as a higher water-cement ratio, which negatively impacts the strength and durability of the concrete. Additionally, the excess fines can hinder the flow of the concrete mix, making it less workable and more difficult to place and finish properly. As a result, maintaining the correct aggregate grading, including managing the amount of fines, is crucial to achieving optimal concrete performance.

The other choices, while they may seem plausible, do not accurately describe the primary effects of excessive fines on concrete quality. Increased strength or improved durability is unlikely, and while a smoother finish might result from certain amounts of fines, excessive fines lead to more significant problems with workability.