Numerical method to model the creep of recycled aggregate concrete by considering the old attached mortar

Experimental creep tests have shown that recycled aggregate in concrete increases its displacement rate. In order to explore this behavior, multiscale modeling has been performed. To consider the old attached mortar surrounding recycled aggregates, creep parameters were calculated from the cement hydrates scale. Sixteen ordinary mortars were calculated to have a large range of values. A homogenization model was applied to calculate the viscoelastic properties. At the concrete scale, in order to take into account the influence of the heterogeneity of the recycled material, a creep-damage coupling model was used. The proposed numerical method demonstrates that the viscoelastic strain of recycled aggregates is not negligible, and leads to a larger creep displacement and higher damage level. Its influence on the time-dependent behavior of recycled aggregate concrete should be considered in modeling.