Detection of early Chinese organic-inorganic composite lime surface from the Lushanmao site, 4300 years ago

Abstract The Lushanmao site, which was excavated from 2016 to 2018, is located in Yan'an City, Shaanxi Province, China. The core area of the ruins is about 2 million square meters, and its total area is more than 2,100 m2s. Its walls and grounds are all covered with a 3-mm thick, white lime coating. We used XRD, IR, and organic additive detection methods (chemical methods and ELISA) to detect white lime samples from the Lushanmao site. Experimental results show that as early as 4300 years ago (about 2300 BCE), local residents had already started adding protein substances to make white lime coatings. This is the earliest organic-inorganic composite building mortar discovered in China so far.