What defines the characteristic of Group III moderate lightweight concrete?

Group III moderate lightweight concrete is characterized by the intentional inclusion of air voids, which significantly reduces the density of the concrete while maintaining its strength and durability. This air-entraining process creates tiny bubbles within the concrete mix, contributing to its lightweight properties, making it suitable for various construction applications where weight reduction is beneficial. The presence of these air voids enhances workability, thermal insulation, and resistance to freeze-thaw cycles.

While heavier aggregates could lead to a denser concrete rather than a lightweight version, natural aggregates do not define the lightweight concrete type, as lightweight concrete can use a variety of aggregates, including synthetic ones. Furthermore, a higher water-to-cement ratio typically leads to a more traditional concrete mix that is not specifically suited to the lightweight category. Thus, the correct choice focuses on the essential trait of air void incorporation, aligning with the definition of Group III moderate lightweight concrete.