Ancient Chinese building secret revealed: sticky rice mortar
Scientists in China have discovered the secret to a 1,500-year-old super-strong ancient Chinese sticky rice mortar that is found in buildings still standing today. Sticky rice is the sweet, glutinous rice.
But only the Chinese appear to have discovered that when mixed with slaked lime, it creates a composite organic/inorganic mortar of legendary strength.
The key to this super-strong mortar is amylopectin, a type of polysaccharide, or complex carbohydrate, found in the rice, report Bingjian Zhang and colleagues from the Laboratory of Cultural Relic Conservation Materials in the Department of Chemistry at Zhejiang University in Hangzhou, China. Their paper is in this month's edition the American Chemical Society journal, Accounts of Chemical Research.
Ancient Chinese builders experimented with multiple organic compounds to add to mortar, including egg whites, tung oil, fish oil and animal blood. Historians believe these organic/inorganic mortars are one reason why so many ancient Chinese buildings have survived. But sticky rice mortar was the most widely used.
The earliest record of sticky rice mortar is found in a book on construction techniques from the Ming Dynasty, 1368 to 1644. But archeological digs show that it was already a mature technology by the South-North Dynasty, from 386 to 589. (Source: Elizabeth Weise, AP, Jun 1, 2010).