Sticky rice holds parts of the Great Wall of China together.

In 2010, researchers at Zhejiang University studied the chemistry of this ancient mortar. They found that a carbohydrate in the rice called amylopectin reacts with calcium carbonate in the lime. This reaction creates a very tight structure that is physically strong and chemically stable.The rice molecules control how crystals grow in the mixture. This results in a finer grain than modern cement. This sticky rice mortar was used during the Ming Dynasty between 1368 and 1644. It was used for city walls, pagodas, and tombs.The mortar is often stronger than the bricks it holds together. In some historical tests, heavy hammers bounced off the walls without leaving a crack. Modern scientists are now studying this rice mixture to help fix old buildings. They want to use materials that match the original strength of the structures.