Retraction: Influence of Relative Mechanical Strengths between New and Old Cement Mortars on the Crack Propagation of Recycled Aggregate Concrete

Abstract

In order to better understand the failure mechanism of recycled aggregate concrete (RAC), numerical studies on modeled recycled aggregate concrete (MRAC) were conducted to investigate the initiation and propagation of microcracks and stress-strain responses of RAC. The constitutive relationships of interfacial transition zones (ITZs) and the corresponding cement mortars were proposed with plastic-damage constitutive relationships. The mechanical properties and the thickness of ITZs were obtained using advanced nanoindentation. The effects of the relative properties between new and old cement mortars on the failure process and stress-strain responses of MRAC were investigated. It was found that the numerical results agreed with the experimental results in terms of crack pattern and stress-strain curves under compression. The results showed that the microcracks first appeared around the weak new and old ITZs, and then propagated into the new and old cement mortar regions. With the increase of the relative strength between new and old cement mortars, the mechanical strengths of MRAC increased, and the microcracks initiation and propagation shifted from the new ITZ to the old ITZ. Overall, the numerical results indicated that optimizing the mix design and improving the properties of ITZs can be effective methods to enhance the mechanical properties of RAC.