What type of aggregate is formed by crushing, sizing, screening an existing hardened concrete surface or structure?

• A. Natural aggregate
• B. Recycled aggregate
• C. Lightweight aggregate
• D. Manufactured sand

Answer: (B)

Crushing, sizing, and screening an existing hardened concrete surface or structure creates recycled concrete aggregate. This material is called recycled aggregate because it originated from demolished concrete and is reused as aggregate in new concrete or as base material. It’s different from natural aggregate, which comes from natural rock deposits; from lightweight aggregate, which is engineered to be low density; and from manufactured sand, which is fine sand produced from rock rather than from concrete. Using recycled aggregate helps reuse waste concrete, though its properties (like higher water absorption due to cement paste) require appropriate mix design and quality control.