Effects of chemical admixtures on the rheology of fresh recycled aggregate concretes

Air-entrainers and super-plasticizers are among the most used chemical admixtures that affect the rheological parameters of fresh cement-based materials. In this work, their influence on fresh properties of recycled aggregate concrete (RAC) is investigated through an experimental campaign, where Bingham rheological parameters, i.e. plastic viscosity µ and yield stress τ0, were analyzed. Ten concrete mixtures were prepared, varying w/c ratio, admixtures content, recycled coarse aggregate substitution ratio and aggregates proportioning methods. In this regard, a particular attention was paid on the Equivalent Mortar Volume (EMV) method for RAC designing. Results were then compared to ones obtained in a previous experimental campaign carried out by the same authors, where further twenty concretes were prepared with the same materials and under the same conditions. From the results achieved in this work, it is possible to conclude how the admixtures addition and aggregates proportioning method influence yield stress and plastic viscosity values.