CT-Based Mesoscale Finite-Element Simulation Research on the Effects of Interfacial Transition Zones on Mechanical Properties of Recycled Concrete

Recycled concrete is an environmentally friendly concrete, which is composed of recycled coarse aggregate, new mortar, old mortar, and the interfacial transition zone (ITZ) between them. These ITZs are the areas where the mechanical properties of recycled concrete are relatively weak. Studying the influence of ITZs on the mechanical properties of recycled concrete is of great significance for optimizing the mix design of recycled concrete. Therefore, computed tomography (CT) scanning technology was firstly used to obtain grayscale images of the mesostructure of recycled concrete, and the grayscale images were processed through image processing technology to establish a finite-element model for the mechanical properties of recycled concrete under uniaxial compression. Finally, the influence of ITZs on the mechanical properties of recycled concrete was analyzed based on the established finite-element model. The results indicated that the finite-element model based on the CT image could effectively characterize the damage properties of recycled concrete. As the elastic modulus of ITZs increased or the thickness of ITZs decreased, the compressive strength of recycled concrete increased. Among them, the compressive strength of recycled concrete increased by 4.4%, when the elastic modulus of ITZ1 increased from 13.49 to 20.23 GPa. The effect of ITZ1 on the mechanical properties of recycled concrete was more significant than those of ITZ2 and ITZ3.