ACI PRC-555-2026, Use of Recycled Concrete Aggregate in Portland Cement Concrete, addresses the production and use of recycled concrete aggregate in new concrete. It follows the material from demolition and preparatory work through crushing and screening to the resulting aggregate characteristics, and summarizes the guidelines and standards that govern recycled aggregate, including repeated recycling across successive generations. Each processing step is tied to the characteristics the aggregate brings to the mixture. Later chapters turn to concrete made with the material, covering mixture proportioning and production, fresh and mechanical properties, and durability, together with methods for enhancing performance and the use of recycled aggregate for internal curing. Case studies describe applications in concrete roadways, architectural and low-strength concrete, and building structures. The guide serves concrete producers, engineers, and agencies evaluating recycled aggregate as a replacement for virgin material.