Simple way to model the mechanical properties of concretes with recycled concrete aggregates

Researchers have made efforts to model the mechanical properties of concretes with recycled aggregates joining large research databases. The replacement ratio criterion of natural aggregates by recycled ones has been widely used in the models, however, itself leads to a great dispersion of results and is inaccurate. In the manuscript, the weighted water absorption of both aggregates (coarse natural and recycled concrete one, Ww) and the effective water/cement ratio were used to easily predict accurately the porosity, compressive strength, and elastic modulus of the recycled concretes. For the modelling, a systematic review of the Brazilian studies from 1999 to 2020 was conducted compiling 169 concrete compositions and joined with 212 concrete mixes from international studies. A supplementary Excel file with the database and all existing correlations was provided. The 20%-replacement ratio limit of many standard codes for structural recycled concretes can be exceeded by using Ww < 5 % for structural concrete [40-60 MPa], or Ww < 8 % [25-40 MPa]. Aggregates with Ww > 8 % can be used for non-structural concretes, with little reduction in compressive strength in absolute terms (<5 MPa). The best %-replacement can be defined for each case, practical for concrete formulations in ready-mix companies.