为实现固体废弃物资源化利用，提升青藏严寒地区再生混凝土砌块性能。在100%再生粗骨料基础上，研究了再生细骨料和活性掺合料对大掺量固废再生混凝土承重砌块抗渗性、耐水性及抗冻性的影响，采用扫描电镜（SEM）、核磁共振（NMR）技术分析了再生混凝土的微观结构，基于生命周期方法（LCA）定量评估了材料性能、成本和碳排放。结果表明：再生混凝土承重砌块渗透性和吸水率随再生细骨料的增加逐渐增大，随粉煤灰与矿渣复掺比的降低先减小后增大，抗冻性和软化系数变化规律则相反。当再生粗骨料取代率为100%、粉煤灰与矿渣复掺比为3∶1时，砌块抗压强度为11.77 MPa，抗折强度为3.89 MPa，软化系数为0.99，吸水率为0.7%，冻融50次后质量损失率为2.2%，抗压强度与抗折强度损失率分别为10.2%和13.9%，满足严寒地区承重及耐久性要求，可作为推荐配合比。微观分析表明，碱激发促进了复合胶凝材料二次水化，生成了更多的水化产物填充内部孔隙，使再生混凝土的细观结构更加密实。随着冻融次数的增加，砌块内部孔隙数量逐渐增多，微孔和中孔逐渐衍生为大孔和裂隙，导致砌块性能劣化。基于性能-成本-碳排放分析，单掺100%再生粗骨料不利于低碳减排，混掺再生骨料和活性掺合料的推荐配合比综合效益最优，碳减排率为31.03%。

To realize resource utilization of solid waste and improve the performance of recycled concrete blocks in severe cold regions of the Qinghai-Tibet Plateau, this study investigates the effects of recycled fine aggregates and active supplementary cementitious materials on the impermeability, water resistance and frost resistance of load-bearing concrete blocks, based on 100% replacement of coarse aggregates with recycled aggregates. The microstructure of recycled concrete was analyzed by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). A life cycle assessment (LCA) approach was employed to quantitatively evaluate material performance, costs and carbon emissions. The results show that the permeability and water absorption of load-bearing recycled concrete blocks increase with the increase of the proportion of recycled fine aggregates, while they decrease first and then increase with a reduction in the fly ash-to-slag blend ratio. Conversely, frost resistance and the softening coefficient exhibit the opposite trend. Under the condition of 100% recycled coarse aggregate replacement and a fly ash-to-slag blend ratio of 3∶1, the compressive strength of the blocks reached 11.77 MPa, flexural strength was 3.89 MPa, softening coefficient was 0.99, water absorption was 0.7%, mass loss after 50 freeze-thaw cycles was 2.2%, and the loss rates of compressive and flexural strength were 10.2% and 13.9%, respectively. These properties meet the load-bearing and durability requirements for severe cold regions, making this mix ratio the recommended formulation. Microscopic analysis shows that alkali activation promotes secondary hydration in the composite cementitious materials, generating additional hydration products that fill internal pores, thereby enhancing the densification of the recycled concrete. However, with the increasing freeze-thaw cycles, the number of internal pores gradually increases, with micropores and mesopores envolving into macropores and cracks, leading to performance degradation. Based on the performance-cost-carbon emission analysis, using 100% recycled coarse aggregates alone is unfavorable for carbon reduction. In contrast, the recommended mix proportion incorporating both recycled aggregates and active SCMs demonstrates the optimal comprehensive benefits, achieving a carbon reduction rate of 31.03%.