Bridged siloxanes as novel potential hybrid consolidants for ancient Qin terracotta

Comparing to the research work on the polychromy protection of Qin Shihuang's Terracotta Army, the protection of the terracotta body itself is somewhat being overlooked. But a very recent survey organized by the State Administration of Cultural Heritage of China shows that the water erosion and salt damage of ancient potteries, including terracotta, are more obvious than previous thoughts. In this work, the protective performances on simulated Qin terracotta samples of two bridged siloxanes with various alkyl bridge groups, bis(triethoxysilyl) ethane and bis(triethoxysilyl) octane, are investigated and compared with tetraethoxysilane and triethoxyoctylsilane. Influences on the porosity and pore size distribution, morphology, physical properties, color alteration and capillary water absorption of untreated and treated terracotta samples are carefully examined. The accelerated freeze-thaw and salt crystallization aging tests are further carried out to evaluate the resistance to aging after protection treatment. The results indicate that both bridged siloxanes show great potential in terracotta consolidation.