Water absorption variability of recycled concrete aggregates

The "ValReCon20 program" has proven the possibility to replace up to 100% of the coarse virgin aggregates by coarse recycled concrete aggregates (CRCA) in concrete of strength class C25/30. Recycled concrete from building demolition is a heterogeneous material. This heterogeneous nature results in a higher standard deviation of many properties of CRCA. One of the important properties of CRCA, needed to design concrete mixes, is the water absorption. The variation due to 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 are investigated. The results show large differences in workability and density of the fresh and hardened concrete, dynamic modus of elasticity, mechanical properties like compressive strength, splitting tensile strength and flexural strength.