The mesoscopic-scale discrete element method (DEM) modeling approach demonstrated high compatibility with macroporous recycled concrete (MRC). However, existing DEM models failed to adequately balance modeling accuracy and computational efficiency for recycled aggregate (RA), replicate the three distinct interfacial transition zone (ITZ) types and pore structure of MRC, or establish a systematic calibration methodology. In this study, PFC 3D was employed to establish a randomly polyhedral RA composite model and an MRC model. A systematic methodology for parameter testing and calibration was proposed, and compressive test simulations were conducted on the MRC model. The model incorporated all components of MRC, including three types of ITZs, achieving an aggregate volume fraction of 57.7%. Errors in simulating compressive strength and elastic modulus were 3.8% and 18.2%, respectively. Compared to conventional concrete, MRC exhibits larger strain and a steeper post-peak descending portion in stress–strain curves. At peak stress, stress is concentrated in the central region and the surrounding arc-shaped zones. After peak stress, significant localized residual stress persists within specimens; both toughness and toughness retention capacity increase with rising porosity and declining compressive strength. Failure of MRC is dominated by tension rather than shear, with critical bonds determining strength accounting for only 1.4% of the total. The influence ranking of components on compressive strength is as follows: ITZ (new paste–old paste) > ITZ (new paste–natural aggregates) > new paste > old paste > ITZ (old paste–natural aggregates). The Poisson’s ratio of MRC (0.12–0.17) demonstrates a negative correlation with porosity. Predictive formulas for peak strain and elastic modulus of MRC were established, with errors of 2.6% and 3.9%, respectively.

The previous freeze-thaw damage model for macroporous recycled concrete (MRC) neglected the pore structure damage that can reduce permeability. Furthermore, macro–mesoscopic factors, such as the old paste on recycled aggregates (RA), were not adequately considered. To address the aforementioned issues and establish a macro–meso coupled freeze-thaw damage model for MRC, freeze-thaw tests were conducted on saturated MRC and its meso-components, namely paste, interface transition zone (ITZ), and RA, in an air environment. The compressive strength, shear strength, indentation elastic modulus, ITZ thickness, old paste exfoliation rate, pore size distribution parameters, and average pore size of the paste, ITZ, RA, and MRC were measured. The test results indicated that, in an air environment, the freeze-thaw damage rates of the paste, ITZ, RA, and MRC were relatively low. Initially, their performance improved before gradually declining. When the paste compressive strength reached 62.5 MPa, the central region of the ITZ specimen exhibited earlier damage compared to the surface region. A novel method for quantifying the damage degree of MRC was developed by integrating changes in both macrolevel mechanical properties and mesolevel pore structure. The damage degree of the MRC was regressed by incorporating the damage degrees of the paste, ITZ, and RA, as well as the filling ratio. The damage degree of the MRC under any number of freeze-thaw cycles can be accurately predicted using the filling ratio of paste and the initial meso parameters of the paste, ITZ, and RA, with a calculation error ranging from 0.004 to 0.080.