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The paper presents the results of studies on based the universal morphology of recycled coarse aggregates in reality, an idealized model of recycled coarse aggregates was prepared using stones. Axial compressive strength tests were conducted on prism-shaped specimens of Modeled Recycled Coarse Aggregate Concrete (MRCAC), which were prepared with different old cement mortar coverages and aggregate arrangements. Through comparison with experimental data, the reliability of the finite element analysis model was determined. It was found that the arrangement of MRCA had a significant impact on the failure characteristics and elastic modulus of MRCAC. Thus, different arrangement modes affected the stress distribution within the specimens, resulting in significantly different axial compressive strength. • Studied the influence of aggregate arrangement on the stress characteristics of MRCAC. • Studied the influence of old cement mortar on the mechanical properties of MRCAC under different internal force transmissions. • Revealed the influence characteristics of old mortar on the stress-strain relationship in recycled concrete. [ABSTRACT FROM AUTHOR]

• Developed a FEA model for six-phase MRCAC. • Studied the influence of MRCA replacement rate and residual mortar thickness on compressive performance of recycled concrete. • Clarified coverage and adhesion amount of old cement mortar by statistical methods and analysis results. Based on the typical morphology of recycled coarse aggregate in reality and the ontological relationship of the existing recycled aggregate concrete (RAC) mesoscopic constituent materials, a finite element analysis model of recycled coarse aggregate that can take into account the factors of the amount and location of attachment of the residual mortar was developed to establish the Modeled Recycled Coarse Aggregate Concrete (MRCAC). Combined with the mesoscopic mechanical properties of MRCAC, a plastic damage intrinsic model was used in the numerical analysis of MRCAC under uniaxial compressive loading to study the damage characteristics and stress–strain relationships of MRCAC. In this paper, the Modeled Recycled Coarse Aggregate (MRCA) is established in the ABAQUS numerical analysis software by self-compiled Python script, and the uniaxial compression simulation of MRCAC is carried out. Compared with the existing idealized model recycled concrete and other forms of digital recycled concrete model, The results show that, on the premise of meeting the general law of existing research results, the development of cracks in MRCAC under load is directly related to the shape of residual mortar wrapping. The strength of MRCAC is minimally influenced by residual mortar adhesion amount; however, the coverage of residual mortar has a significant impact on its strength. The arrangement of MRCA may also play a role in the stress–strain relationship of MRCAC. Additionally, it should be noted that residual mortar adhesion amount and coverage are distinct concepts that affect the strength and strain of MRCAC independently. These findings highlight the need to differentiate between these two factors in further research. [ABSTRACT FROM AUTHOR]

• This study aims to investigate the uniaxial stress–strain relation of mixed recycled aggregate concrete (MRC). • The stress–strain relation of MRC cannot be well predicted by existing models. • The proposed model can effectively predict the stress–strain relation of MRC. The purpose of this paper is to study the uniaxial stress–strain relationship of mixed recycled concrete (MRC), which composed of brick recycled aggregate (BRA), concrete recycled aggregate (CRA) and natural aggregate (NA). MRC with various replacement ratio of MRA and various contents of BRA was studied under uniaxial compression. The stress–strain characteristic and toughness of MRC were studied firstly, and the results exhibited that the peak stress and elastic modulus decreased with the increase of MRA replacement ratio and BRA content, while the opposite trend was observed for the ultimate and peak strain. Then, the test stress–strain data were compared with existing stress–strain models of natural or recycled concrete. The comparison results indicate that the existing models cannot be well predicted the stress–strain relationship of MRC. According to the test results in this study, the stress–strain constitutive model of MRC was established by modifying of the shape parameters for the CRA concrete (RAC) constitutive model, which can well predict the stress–strain relationship of MRC. [ABSTRACT FROM AUTHOR]