The Great Wall of China is a structure that amazes not only with its scale but also with its amazing strength. Abandoned in the middle of the 17th century, the building survived numerous earthquakes, temperature drops, humidity, passed through the centuries, without falling apart to the foundation, like most modern buildings.
How many years did they build the Great Wall of China?
Contrary to popular belief, the defensive structure, stretching for 21 thousand kilometers, began to be erected back in the 5th century BC. and continued to work until 1644.
At the same time, the brick building became only by the XIV century, through the efforts of the rulers of the Ming dynasty. Up to this point, the fortification was a network of adobe and earthen ramparts, reinforced from the outside with red shields.
During the period of feudal fragmentation, to protect against the raids of nomads from the north and from each other, every Chinese principality-kingdom acquired similar structures.
Emperor Qin Shi Huang joined the wall into a single whole in 249 BC. Is the first ruler in Chinese history to conquer and unite the entire region.
The grouping of scattered shafts into one structure lasted 10 years. It was 249 BC. considered the formal date of the construction of the Great Wall.
For a thousand years, the wall was improved and expanded, periodically mobilizing from 300 thousand to 2 million workers. Considering the ancient and medieval level of medicine, supply problems, and attitudes towards human rights in general, tens of thousands of workers вЂњdid not live up to the delivery of the facilityвЂќ.
In 1644, when the nomads bribed the garrison, marched behind the wall, and once again conquered the Celestial Empire, the Chinese abandoned the Great Wall.
The restoration of the wall began only in 1984!
How were the bricks of the Great Wall held together?
Rice flour paste.
In Western Europe, since the time of the Roman Empire, volcanic dust was added to the mortar to give strength to the structure. The crushed magma strengthened the material, making it durable.
There was no volcanic ash in the Celestial Empire, but there was rice вЂ” a scarce, expensive, but accessible resource.
From this resource, according to research by a professor of physical chemistry Bingjiang Zhang, Chinese builders were the first in the world to invent paste.
The binder was obtained by mixing rice broth with slaked lime вЂ” calcium carbonate. The polysaccharide amylopectin, which is one of the components of rice starch, provided moisture resistance and strength of the composite material.