A concurrent multiscale approach for modeling recycled aggregate concrete

The use of recycled concrete aggregates in new concrete is an alternative that can provide economical and environmental benefits. However, the influence of the inert particles on the mechanical behavior of concrete needs to be better understood. To provide a comprehensive simulator to predict the failure mechanism of this material taking into account its heterogeneity in mesoscale, a mesh fragmentation technique composed of interface solid finite elements equipped with a tensile damage model is employed. To minimize computational costs, a concurrent multiscale strategy based on the use of coupling finite elements to connect the macro and mesoscale regions is adopted. In mesoscale, the different phases of the recycled aggregate concrete (RAC) are explicitly represented, consisting of: (i) new mortar matrix; (ii) recycled aggregate composed of old matrix and crushed rock (natural aggregate); and (iii) interfacial transition zones in between all of them. For the regions where cracks are not expected, homogenized elastic parameters are assumed for the RAC. Three-point bending beams experimentally tested by Casuccio et al. {[}4] are numerically analyzed for concrete with compressive strength targets of 18, 37 and 48 MPa. These concrete beams were produced with coarse aggregates derived from natural crushed stone and another two coming from recycled concrete with high and normal strengths. The numerical results obtained show that the concurrent multiscale model is able to represent the tensile failure mechanism of the RAC, taking into account explicitly the effects of the recycled components on crack patterns and structural predictions. (C) 2020 Elsevier Ltd. All rights reserved. (AU)