Sticky rice mortar is an ancient building material that originated in China. It utilized

organic materials Organic matter, organic material or natural organic matter is 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 come fro ...

such as sticky rice soup along with inorganic materials such as

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 with water. Annually, approxim ...

to form a mortar. Its usage has been dated to the

Northern Wei Dynasty Wei (), known in historiography as the Northern Wei ( zh, c=北魏, p=Běi Wèi), Tuoba Wei ( zh, c=拓跋魏, p=Tuòbá Wèi), Yuan Wei ( zh, c=元魏, p=Yuán Wèi) and Later Wei ( zh, t=後魏, p=Hòu Wèi), was an imperial dynasty of Chi ...

from the fourth century CE. The mortar provided extra strength, resilience, and water resistance to structures, and hence was an important component in the construction of several historical buildings including walls, and other structures across China.

History

The sticky rice mortar dates originated in China. Its origin can be traced back to the

from fourth century CE. While it was introduced much earlier, its use became widespread during the

Ming Dynasty The Ming dynasty, officially the Great Ming, was an Dynasties of China, imperial dynasty of China that ruled from 1368 to 1644, following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming was the last imperial dynasty of ...

in the later

Middle ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...

, when it formed a key component of large construction projects such as the

Great Wall of China The Great Wall of China (, literally "ten thousand ''li'' long wall") is a series of fortifications in China. They were built across the historical northern borders of ancient Chinese states and Imperial China as protection against vario ...

, and other monuments.

Composition

The ingenuity of incorporating

sticky rice Sticky may refer to: Adhesion *Adhesion, the tendency of dissimilar particles or surfaces to cling to one another *Sticky mat, an adhesive mat used in cleanrooms to lessen contamination from footwear *Sticky note, a generic term for a Post-it Note ...

, a readily available food source, into a building material showcases advanced traditional Chinese engineering knowledge. This practice was a closely guarded secret among master masons for centuries. Sticky rice soup was mixed with

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

lime mortar Lime mortar or torching is a masonry mortar (masonry), mortar composed of lime (material), lime and an construction aggregate, aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, used in ancient Rome and anci ...

. The sticky rice is typically boiled to a thick soup or gruel, which is then mashed and added to the lime. 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 amyloplas ...

, 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 wat ...

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

Uses

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. It played a major role in maintaining the durability of the

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

, as well as tombs, pagodas, and city walls. Sections of the Great wall of China 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. Other structures built with sticky rice mortar such as the walls of Xi'an and Nanjing, have been standing for significant amount of time against the natural elements and other human activities. The amylopectin enhances the cohesive forces within the mortar, leading to significantly higher compressive and flexural strength. It has higher water resistance than traditional mortar.

References

{{reflist Bricks Building materials Cement Chinese inventions Concrete History of the Great Wall of China Rice Traditional East Asian architecture