Long-cycle freeze–thaw performance of demolition-derived recycled aggregate concrete

Temperature variability and moisture availability can affect the condition of existing concrete and, in turn, the quality of recycled aggregates (RAs) recovered after the demolition of concrete structures. Demolition concrete from Ordu, Trabzon and Gümüşhane (in the Black Sea region of Türkiye) was cored to assess the concrete quality in terms of uniaxial compressive strength, then crushed to produce coarse RA. Recycled aggregate concrete was produced with 0%, 25%, 50% and 100% RA and exposed to 300 controlled freeze–thaw (FT) cycles. Ultrasonic pulse velocity was measured every 30 FT cycles and specimen mass was recorded to track internal damage and physical deterioration. Post-exposure, scanning electron microscopy identified microcracking, pore coalescence and interfacial transition zone degradation, which was found to intensify with an increase in RA content. Provincial temperature amplitude and mean relative humidity were used as source-history context to interpret variability in the integrity of the parent material. A higher RA content accelerated damage evolution and led to late-stage specimen failure, supporting RA source quality screening for FT-exposed applications.