Effect of mechanical treatment on recycled aggregate properties

The replacement of natural aggregate (NA) with recycled aggregate (RA) in concrete offers significant economic and environmental benefits by reducing landfill disposal of construction and demolition waste (C&DW) and lowering the costs and emissions associated with NA excavation and transportation. However, RA typically has higher water absorption and poorer bond with cement paste due to adhered old mortar, which limits its replacement ratio in structural-grade concrete. This study investigates the effect of mechanical treatment methods on the properties of RA in terms of density, water absorption, and crushing value, including their variability. Subsequently, the treated aggregate is used to replace the coarse fraction and produce recycled aggregate concrete (RAC), and the material properties are assessed. The mechanical treatment is performed using ball mill, and the parameters investigated include processing time and media ratio under wet and dry conditions. Treatment durations varying from 30 to 120 minutes were applied to twelve groups of RA samples. The results are discussed in terms of changes in the physical and mechanical properties of both treated RA and the resulting RAC. Overall, the treated RA exhibits reduced water absorption and a lower crushing value, resulting in concrete with improved mechanical properties and reduced variability.