Final answer:
Fine aggregate, like sand, is crucial in a concrete mix as it fills voids between coarse aggregates, enhances workability, and contributes to the durability and longevity of the concrete while also being cost-effective.
Step-by-step explanation:
The purpose of fine aggregate, or sand, in a concrete mixture is multifaceted. Firstly, sand helps to fill the voids between the coarse aggregates (like gravel or crushed stone), leading to a denser and more stable concrete mix. This density enhances the structural integrity of the final concrete product. Additionally, fine aggregates contribute to the workability of the concrete, making it easier to mix, transport, and place during construction.
Moreover, the fine aggregate influences the durability, finishing, and appearance of the concrete once set. It also reduces shrinkage and stresses in the concrete, leading to a longer-lasting material. The use of sand specifically allows for a more economical construction, as sand is a more readily available and less expensive material compared to other types of fine aggregates.