Protective Materials for Rock Cultural Heritage: Current Status and Future Perspectives

Rock cultural heritage, as a vital constituent of human civilization, is highly vulnerable to multifaceted deterioration processes-including weathering, cracking, and salt efflorescence—when subjected to prolonged exposure to complex natural and anthropogenic environments. Addressing the conservation and restoration of these materials has therefore emerged as an urgent priority. Traditional conservation agents, such as limewash, silicate-based consolidation, and natural organic substances, have provided valuable practical experience; nonetheless, they are constrained by issues of compatibility, durability, and long-term stability. In recent decades, advances in nanomaterials, polymers, and functional composites have offered new possibilities, exhibiting favorable characteristics such as superior penetration, enhanced long-term durability, weather resistance, and environmental sustainability. Concurrently, the exploration of biomimetic materials has further expanded the conceptual framework of heritage conservation. Case studies suggest that these novel materials confer notable advantages in practice; however, uncertainties remain regarding their long-term performance, substrate compatibility, and structural stability. The field continues to be challenged by the absence of standardized evaluation protocols, limited longitudinal monitoring data, and insufficient interdisciplinary integration. Looking ahead, research should prioritize the development of environmentally friendly and intelligent materials, promote the transition from single-material innovation toward systematic conservation strategies, and reinforce the establishment of international standards and collaborative networks to ensure the sustainable preservation and transmission of rock cultural heritage.