• Concrete with recycled aggregate matched/exceeded original concrete’s strength. • Steel fibers outperformed PP fibers in boosting flexural and splitting tensile strength. • Two types of interfacial transition zone ITZ types after recycling: recycled aggregate-cement and natural aggregate-cement. • Recycled aggregate-cement ITZ was compact and rarely caused cracks, unlike natural aggregate-cement ITZ. • Minor porosity change, but higher water absorption in recycled aggregate concrete. The recycling of construction and demolition waste is increasingly important for sustainable construction practices. However, limited attention has been given to the reuse of high-performance concrete across multiple recycling generations while maintaining engineering-level performance. This study examines the feasibility of using high-performance fiber-reinforced concrete (HPFRC) as a recycled aggregate source for multigenerational concrete production with potential structural applications. Three generations of concrete mixtures incorporating either steel or polypropylene fibers were produced, tested, crushed, and reused as partial replacements of coarse aggregate. Standard mechanical tests, water absorption measurements, and microstructural characterization were conducted to assess strength retention, durability-related behavior, and microstructural integrity. The experimental results demonstrated that HPFRC-derived recycled aggregates preserved high functional performance across successive recycling cycles. The compressive strength remained close to 70 MPa, or even exceeded 80 MPa, after the first recycling cycle, and declined only slightly after the second cycle. Microstructural observations indicated that residual fibers reduced crack propagation and porosity while improving interfacial transition zone formation, thereby enhancing mechanical performance and water resistance. From an engineering perspective, the results indicate that HPFRC-derived recycled aggregates can be utilized in concrete mixtures requiring high mechanical performance and crack resistance while maintaining acceptable durability-related properties. The obtained results contrast with the typical performance deterioration observed in recycled concrete. Overall, the repeated use of HPFRC-derived recycled aggregate represents a practical approach for reducing natural aggregate consumption and supporting circular construction strategies in engineering applications.
Krejsová et al. (Sun,) studied this question.