Approximately 1,500 years ago, ancient Chinese builders mixed glutinous rice, slaked lime, and limestone to create a paste, which was then filled into the gaps between bricks and stones, producing an ultra-strong "glutinous rice mortar."

The Miraculous Adhesive in Ancient Architecture: Glutinous Rice Mortar

Glutinous rice mortar is considered the best material for restoring ancient buildings that still exist today. It is regarded as one of the greatest technological innovations in history.

The composition of glutinous rice mortar includes slaked lime, glutinous rice paste, and some sandstone. Glutinous rice mortar may be the world's first composite mortar made from organic and inorganic raw materials, offering greater strength and water resistance than pure lime mortar.

Why is Glutinous Rice Mortar So Sturdy?

Scientific research has discovered a "secret ingredient" called amylopectin, which appears to be the main reason for the legendary strength of glutinous rice mortar. Amylopectin is a polysaccharide or complex carbohydrate found in rice and other starch-containing foods. Scientists state: "Analytical research shows that ancient masonry mortar is a special organic-inorganic composite material. The inorganic component is calcium carbonate, while the organic component is amylopectin derived from the glutinous rice soup added to the mortar. In addition, we found that the amylopectin in the mortar acts as an inhibitor: on the one hand, it controls the growth of calcium sulfate crystals, and on the other hand, it generates a compact microstructure, which should be the reason for the great strength of this organic-inorganic mortar."

The Big Wild Goose Pagoda and the Small Wild Goose Pagoda in Xi'an have withstood the vicissitudes of a thousand years. The formerly bustling Tang Dynasty Jianfu Temple has long been destroyed in war, but the Big Wild Goose Pagoda and the Small Wild Goose Pagoda have survived, standing majestically for more than 1,300 years and becoming landmark buildings left over from the Tang Dynasty Chang'an City. They have witnessed the thousand-year development of the ancient capital Xi'an. Scientists have discovered glutinous rice components in the wall adhesive of the Great Wall (Ming Dynasty Great Wall), and glutinous rice mortar is considered the main adhesive material of the Great Wall. This highly strong adhesive material is also believed to be the reason why the Great Wall has stood for thousands of years. In ancient China, glutinous rice mortar was generally used in the construction of tombs, pagodas, city walls, and other large buildings, some of which still exist today. Some ancient buildings are so sturdy that even modern bulldozers struggle to demolish them, and they can withstand intense earthquakes.

To determine whether glutinous rice can aid in the restoration of buildings, researchers prepared lime mortars with different amounts of glutinous rice mixed in and tested their properties against traditional lime mortar. The test results of the two types of mortar showed that lime mortar mixed with glutinous rice soup has more stable physical properties, greater mechanical strength, and better compatibility, making it a suitable material for restoring ancient stone buildings.

To this day, many ancient buildings that used glutinous rice mortar, such as the ancient city walls in Nanjing, Xi'an, Jingzhou, Kaifeng, and the Ming and Qing Dynasty Fish Scale Stone Embankment along the Qiantang River, remain very sturdy despite having withstood the erosion of wind and rain for hundreds or even thousands of years. Facts have proven that glutinous rice mortar is an outstanding architectural cementitious material.