Sticky rice mortar was invented in

ancient China The earliest known written records of the history of China date from as early as 1250 BC, from the Shang dynasty (c. 1600–1046 BC), during the reign of king Wu Ding. Ancient historical texts such as the '' Book of Documents'' (early chapte ...

utilizing

organic materials Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

in inorganic mortar. Hydraulic mortar was not available in ancient China, possibly due to a lack of

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

. Around 500 CE, sticky rice soup was mixed with

slaked lime Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has ma ...

to make an inorganic−organic composite mortar that had more strength and water resistance than

lime mortar Lime mortar or torching is composed of lime and an aggregate such as sand, mixed with water. The ancient Egyptians were the first to use lime mortars, which they used to plaster their temples. In addition, the Egyptians also incorporated various ...

Sticky rice Glutinous rice (''Oryza sativa var. glutinosa''; also called sticky rice, sweet rice or waxy rice) is a type of rice grown mainly in Southeast and East Asia, and the northeastern regions of South Asia, which has opaque grains, very low amylose ...

played a major role in maintaining the durability of the

Great Wall The Great Wall of China (, literally "ten thousand Li (unit), ''li'' wall") is a series of fortifications that were built across the historical northern borders of ancient Chinese states and Imperial China as protection against Eurasian noma ...

, as well as tombs, pagodas, and city walls. Sticky rice mortar had high adhesive strength, sturdiness, waterproofing capability, and prevented weeds from growing as crude mortar made of sticky rice and burnt lime created a seal between bricks that would rival modern cement in strength. During the

Ming dynasty The Ming dynasty (), officially the Great Ming, was an Dynasties in Chinese history, imperial dynasty of China, ruling from 1368 to 1644 following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming dynasty was the last ort ...

(1368–1644 AD), brick-making techniques improved significantly in terms of quantity and quality of production. Since then, Great Wall sections were widely built with bricks, with lime mortar and sticky rice used to reinforce the bricks strongly enough to resist earthquakes and modern bulldozers while keeping the building intact. Modern chemists, through their research, identified

amylopectin Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Plants store starch within specialized organelles called amylopl ...

, a type of

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...

, or complex carbohydrate, found in rice and other starchy foods to appear to be responsible for the sticky rice mortar's strength and durability.

References

Bricks Building materials Cement Chinese inventions Concrete Great Wall of China Rice Traditional East Asian Architecture {{architecturalelement-stub