Using Fines from Recycled High-Quality Concrete as a Substitute for Cement

Concrete manufacturing and recycling must evolve to meet sustainability and carbon reduction demands. While the focus is often on reusing coarse aggregates, fine fractions are also produced during recycling. This study explores using ground fine fractions (0/2) as a partial cement substitute. The fines were characterized for their mineralogical, chemical, and physical properties, and experiments were conducted on pastes and mortars with 0% to 30% cement substitution, including isothermal calorimetry and strength tests. Two concrete mixes—a reference mix with natural aggregates and CEM I, and a mix with 10% concrete fines replacing CEM I—using recycled sand and coarse aggregates were tested for compressive strength, carbonation, shrinkage, and freeze–thaw resistance. The results indicated that the recycled concrete had a comparable strength to the reference and a slightly reduced durability in freeze–thaw conditions. In terms of shrinkage, recycled concrete with 10% concrete fines had an increased drying shrinkage and a lower autogenous shrinkage due to the water retention capacity of the recycled aggregates.