Creep Rheological Models for Recycled Aggregate Concrete

Five rheological models for conventional concrete are modified to make them suitable for application to recycled aggregate concrete (RAC). The modification involves the inclusion of the effects of the quantity and properties of residual mortar on creep of RAC. The accuracy of the modified models is assessed by comparing their predictions with measured creep strain data from 150 x 300 mm (6 x 12 in.) concrete cylinders made of RAC, proportioned either by the conventional concrete mixture design method or by the Equivalent Mortar Volume (EMV) Method developed by the authors. It is demonstrated that the modified rheological models can be used to obtain reasonable estimates of the creep of RAC, irrespective of the mixture proportioning method and the aggregate type. It is also shown that, for practical applications, the existing ACI Method for calculating the creep of concrete can be applied to RAC via the introduction of a recycled concrete aggregate (RCA) coefficient.