Multi-Factorial Damage Mechanisms of Chinese Grey Bricks Under Complex Natural Environments: A Comprehensive Review from Manufacturing to Performance Degradation

Grey bricks possess significant technological and cultural value and suffer severe degradation from long-term exposure to complex natural environments. Following PRISMA guidelines, this study systematically reviews manufacturing processes, physical and mechanical properties, and damage mechanisms of grey bricks, integrating civil engineering, materials science, and cultural heritage perspectives. By introducing traditional manufacturing processes, the study highlights substantial differences in modern replica raw materials, craftsmanship, and kilns, emphasizing caution when generalizing durability assessment conclusions based on modern replica grey bricks to historical grey bricks. Statistical analysis of 2,733 physical and mechanical parameters across 24 categories reveals high data dispersion stemming from intrinsic variability, cumulative damage, and experimental differences. Damage mechanisms are categorized into physical (water–ice expansion, fluid migration, fatigue damage), chemical (dissolution, salt crystallization), biological (biophysical destruction, biochemical corrosion), and mechanical (contact damage, stress wave propagation) processes, often exhibiting synergistic or inhibitive effects. This study proposes priority directions for advancing the field through advanced characterization techniques, standardized testing systems, computational simulation, and artificial intelligence. The research findings provide a basis for enhancing structural disaster resilience, evaluating material durability, developing novel durable materials, and deepening the study of material degradation under complex natural environments.