What is the primary characteristic of moderate lightweight concrete used in construction?

Moderate lightweight concrete is characterized primarily by its use of expanded aggregates. This type of concrete is designed to reduce the overall weight while maintaining sufficient strength for construction purposes. Expanded aggregates, such as expanded clay, shale, or pumice, create air pockets within the concrete. This not only decreases the density of the material but also improves its thermal insulation properties and workability.

The use of expanded aggregates is integral to achieving the lightweight nature of this concrete, making it suitable for various applications, including structural components in buildings where reducing weight is essential for design or load considerations. While other characteristics, such as lower density or potential water resistance, can be associated with lightweight concrete, the defining characteristic remains its incorporation of these specialized aggregates. This allows for a balance between performance and weight, meeting specific engineering and architectural needs in construction projects.