What materials can fine aggregate consist of?

Fine aggregate plays a crucial role in concrete composition, primarily influencing the workability, strength, and durability of the concrete mixture. The correct answer highlights that fine aggregate can consist of natural sand, manufactured sand, or a combination of both.

Natural sand is typically derived from riverbanks, beaches, or mountains and is screened to remove debris and larger particles. Manufactured sand, on the other hand, is produced from crushing rocks or stone, which allows for more control over the characteristics, such as size and shape, compared to naturally occurring sand.

Both types of fine aggregate serve to fill the voids between larger aggregates in concrete, providing a stable and dense mix that adheres well during the curing process. The blending of natural and manufactured sand is commonly practiced to achieve desired performance standards and to optimize the properties of the concrete.

Other options focus on more restrictive definitions. For instance, stating that fine aggregate consists only of natural sand excludes the versatility and benefits that manufactured sand can provide. Additionally, including gravel and crushed stone refers to coarse aggregates rather than fine aggregates, which are distinctly smaller in grain size and purpose within the concrete mix. Air-cooled blast furnace slag, while a valuable alternative aggregate in certain applications, does not fit the category of fine aggregates either