Qin Shihuang’s Terracotta Army is one of the most important and well-known cultural heritage sites in China. The army was probably set up to protect the nearby grave of the first emperor Qin Shihuang (259–210 BC) as well as his afterlife. At the renowned site, archaeologists began the latest round of excavation in 2009 in a pit untouched for two decades. The main damages of the unearthed ware sculptures are missing surface chips, cracking, and flaking, which are possible due to salt erosion and freeze-thaw.
The feasibility and effectiveness of two typical bridged siloxanes monomers as consolidants for the Qin Shihuang’ Terracotta Army were investigated. The protection performances of selected siloxanes were tested on simulated terracotta samples in the laboratory by methods including colorimetric measurements, consolidant uptake, water absorption ratio, porosity and saturation factor in freeze-thaw. The treated samples exhibited a significant increase in resistance to freeze-thaw and salt damage, which could be attributed to water absorption reduction as the surface became hydrophobic. As expected, the dynamic elastic modulus and compress strength increased as the bridged siloxanes organic-inorganic hybrid formed. Meanwhile, the porosity decreased due to the pore filling by the hybrid consolidant, as revealed by mercury porosimetry. The water resistance ability was evaluated by the capillary water absorption test, and the “breath function” did not significantly change based on the water vapor transmission test data.
