Fuzzy comprehensive evaluation of the compatibility of restoration materials — Case study in the rammed earth restoration of the M2 Han tomb in Dingtao, Shandong Province

Based on the restoration of rammed earth structures in the Mausoleum of the Dingtao King (M2) in Shandong Province, China, a fuzzy comprehensive evaluation system for determining the compatibility of rammed earth cultural relics and various restoration materials was established using the fuzzy logic theory. Using this system, the compatibility between organic/inorganic-composite-modified natural hydraulic lime (NHL)-based restoration materials and the rammed earth matrix was evaluated. In this study, the primary factors affecting the compatibility of the modified NHL-based restoration material and the matrix to be restored included soil binder ratio, silica fume (SF) dosage, and organic modifier dosage. The soil binder ratio was found to be the most important factor affecting the compatibility between the restoration material and the matrix; the optimal formulation for the restoration material was found to have a soil binder ratio of 8:1, a SF dosage of 5%, and an organic modifier dosage of 10%. This optimal formulation was then applied in the field reinforcement test of the rammed earth in the M2 Han tomb. After one year, no cracking or separation at the interface between the restoration material and the rammed earth matrix was observed; the interface bonding performance and compatibility were thus considered excellent. The restored part of the structure exhibited no surface effloresce or detachment; therefore, the durability of the restored structure was considered to be excellent. The abovementioned results demonstrate the effectiveness of the fuzzy comprehensive evaluation method proposed in this study. This study can be used as a reference for the optimization of restoration materials for use in the restoration of cultural relics.