Properties and Characterization of Building Materials from the Laosicheng Ruins in Southern China*
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Properties and Characterization of Building Materials from the Laosicheng Ruins in Southern China* Ya Xiao1,2, Ning Wang2, Haibin Gu1, Weimin Guo1, Feng Gao2,3, Ning Niu4, Shaojun Liu2,5** 1
Cultural Relics and Archaeology Institute of Hunan Province, Changsha, 410083, China State Key Laboratory for Powder Metallurgy, Central South University, Changsha, 410083, China 3 Chinese Academy of Cultural Heritage, Beijing, 100029, China 4 Henan Research Institute of Ancient Architecture Protection, Zhengzhou, Henan, CHINA 5 School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China 2
ABSTRACT As one of the most typical ancient cultural relics in southern China's minority regions near Changsha in Hunan province, the magnificent Laosicheng ruins excavated recently have been included in the UNESCO World Cultural Heritage Tentative List. Urgent conservation of excavated Laosicheng ruins brings about the need for a study of the formulation and properties of construction materials used, including earth, stone, mortar, and brick. In the present study, comprehensive analyses were carried out to determine their raw material compositions, mineralogical, and microstructural properties using sheet polarized optical microscopy, scanning electron microscopy with energy dispersive spectrometer, thermogravimetric/differential scanning calorimetry, X-ray powder diffraction, and Fourier transform infrared spectroscopy. Special attention was paid to mortars, which were the most widely used in building the Laosicheng. Results show that mortar used as external render of the city wall is mainly built up from inorganic CaCO3 and MgCO3 based hybrid materials produced by the carbonation of Ca(OH)2 and Mg(OH)2 with a small amount of sticky rice. In contrast, mortar used to bond stones of the city walls is a traditional mortar that does not contain sticky rice. This study is a part of a huge interdisciplinary project aimed to clarify the role of organics in ancient China’s organic-inorganic hybrid mortar, which can be considered as one of the greatest invention in construction material history. The results provide valuable basic data and restoration strategies that can be used in the conservation of the ruins as well. INTRODUCTION The Laosicheng ruins, currently the largest, best preserved, and oldest ancient military castles in Southwest China, are located in the Yongshun County in the Hunan province, China. The original city was built in 690AD with a well-conceived layout. The Laosicheng used to be *
Note: The characters “cheng” in Laosicheng mean city in Chinese. Corresponding author. Tel: +86 731 88876315; Email address: [email protected] (S. J. Liu)
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the economic, political, military and cultural center of Tujia ethnic group, a traditional minority in Southwest China, during the reign of Tusi system. The Laosicheng ruins are about 25 square kilometers. The central city about 19 hectares includes the palace areas, government offices, residential areas, tombs, and religious worship areas. As one o
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