Exfoliation of stone cultural relics under the microclimate in the Yongling Mausoleum of the Former Shu Dynasty

Abstract

Many degradation processes of cultural heritage objects are associated with unsuitable microclimatic conditions. One of the most ubiquitous deteriorations is the crystallization of salts in pores, which can accelerate the erosion rate of masonry historical relics. In this study, the microclimate of the burial tomb and exfoliation of sandstone in the Yongling Mausoleum of the Former Shu Dynasty in Chengdu were monitored for 1 year to determine the development of the degradation. We established a connection between the monitoring data and exfoliation variations of the stone with time. To predict the deterioration of the stone, a three-dimensional computational finite element model was used to simulate the detailed process of the thermo-hygrometric performance that led to salt crystallization and artwork deterioration. Two results were obtained. In the simulation of the microclimate, the temperature ranged from 15 to 22.6 °C, and the relative humidity was heterogeneous and varied between 60 and 100%. The other was the relationship between the microclimate and exfoliation. It was found that the exfoliation was more severe in the higher relative humidity areas where the water vapor frequently interacted with the relics. The crystallization and hydration of sulfate produced stress, which damaged the stone relics. These results provide a rationale analysis and a reference for better management of the environmental interactions and reduction of the environmental impacts in the subsequent scientific conservation of ancient Chinese cultural relics in tombs.