When considering aggregate size for concrete, what is crucial for minimizing voids?

Selecting a nominal maximum size for aggregates that is not larger than three-quarters of the clear spacing between the reinforcing bars is crucial for minimizing voids in concrete. This practice ensures that the aggregates can be efficiently packed together, reducing the amount of space that remains unfilled, which can otherwise lead to a lower density and strength in the concrete mix.

When aggregates are appropriately sized relative to the clear spacing, it promotes more effective distribution and alignment within the mix, resulting in a denser composite material. This consideration is particularly important in structural applications where strength and durability are paramount.

Utilizing aggregates that are excessively large (as posited in some alternatives) can create gaps that contribute to voids, while mixing aggregates of varying sizes arbitrarily lacks a strategic approach that takes into account load distribution and consolidation. Additionally, opting for highly porous aggregates would counteract the goal of reducing voids, as porosity increases the potential for air pockets. Thus, the practice of aligning the maximum aggregate size with the spacing of reinforcing bars is a fundamental principle in concrete design aimed at achieving optimal density and strength characteristics.