Water absorption variability of recycled concrete aggregates

The programme ValReCon20 has demonstrated the possibility of replacing up to 100% of coarse virgin aggregates with coarse recycled concrete aggregates (CRCA) in concrete of strength class C25/30. Recycled concrete from building demolition is a heterogeneous material, resulting in a higher standard deviation of many properties of CRCA. One of the important properties of CRCA, needed to design concrete mixes, is water absorption, but the heterogeneous nature of CRCA makes it harder to predict the actual amount of water that will be absorbed by CRCA during the mixing process. This paper compares the effects of over- and underestimation of the water absorption of CRCA. Various properties were investigated and the results show large differences in the workability and density of fresh concrete, water absorption by submersion and capillarity of the hardened concrete, dynamic modus of elasticity and mechanical strength properties.