What does the term 'aggregate' refer to in construction?

The term 'aggregate' in construction specifically refers to granular materials that are used in concrete and asphalt mixtures. These aggregates can be composed of natural sand, gravel, crushed stone, or manufactured aggregates such as expanded clay or pumice. They serve as the primary component in concrete, providing volume, stability, and strength to the final product. The selection and quality of the aggregate are crucial as they affect the durability, workability, and overall performance of concrete and asphalt.

The other options do not align with the definition of 'aggregate.' Steel components are typically associated with structural reinforcements, wooden structures pertain to formwork or framing, and liquid materials for waterproofing relate to protective coatings or membranes, none of which are classified as aggregates. Thus, the correct answer underscores the essential role of aggregates in the construction industry, particularly in the formation of durable and resilient concrete and asphalt mixtures.