Mesoscale modelling of recycled aggregate concrete under uniaxial compression of different strain rates

Abstract

Studying the compressive behaviour of recycled aggregate concrete (RAC) under different strain rates in a mesoscale model is of considerable interest. In the mesoscale model in this paper, RAC is regarded as a five-phase composite material mainly comprising natural aggregates, old interface transition zone (ITZ), old cement mortar, new ITZ and new cement mortar. The existence of pore defects is also considered. Random round aggregates and oval aggregate models of different recycled coarse aggregate replacement rates (0%, 25%, 50%, 75% and 100%) are constructed in the mesoscale RAC model. The uniaxial compressive behaviour of the mesoscale RAC model under different strain rates is numerically simulated. Numerical results show that the material properties of the ITZs have an impact on material damage. The compressive strength of recycled concrete increases with the strain rate, showing dynamic strain rate effects. The dynamic increase in strength is not only due to the material property, but also due to the inertia confinement. A mesoscale model of RAC with 1% porosity is then established to study the influence of initial micro-defects in RAC on its mechanical properties. The numerical results are compared with those of RAC without initial pore defects. These results indicate that the existence of pores considerably affects the formation and development of cracks under static and dynamic uniaxial compressions and weakens the compressive strength of RAC materials.