PROPERTIES AND DETERRIORATION MECHANISM OF SANDSTONE BLOCKS IN CHENGDE ROYAL BUILDINGS BETWEEN 1703 AND 1792

The mountain resort and its outlying temples, Chengde, located 250km northeast to Beijing, were built between 1703 and 1792. They are the Qing dynasty's royal gardens and temples. In 1994,it was listed as a World Heritage Site by UNESCO. Sandstone blocks were extensively used for the buildings. Many stone relics have been suffered from various weathering diseases including crack, scaling, disintegration, and biological invasion due to long-term weathering. In the paper, properties of mineralogy, physical and mechanical of weathered and unweathered sandstone samples are analyzed using petrographical and petrophysical methods. On this basis, deterioration mechanism is analyzed. The main causes of the sandstone weathering(main including scaling and disintegration) are dissolution calcareous cement, drying-wetting cycle and salt crystallization. The results can facilitate the choice of the most suitable conservation method.