The Englishman in 1796. Parker fired brown Roman cement from marl, and by 1824, the British builder Joseph Aspo invented cement and patented Portland cement, before that, cement was still a myth, but without cement, the Ming City Wall had lasted 600 years and was still indestructible. Materials are reluctant to use in modern times.
In 1357, the Ming Dynasty minister Zhu Sheng proposed to Zhu Yuanzhang to "build a high wall, accumulate grain, and slowly claim the king", Zhu Yuanzhang felt that it was reasonable, so he adopted it, Zhu Yuanzhang established the Ming Dynasty and ordered the construction of the city universally, the Nanjing Ming City Wall was built in 1366, after 28 years, it was completed in the twenty-sixth year (1393) of Ming Hongwu.
According to records, 280,000 migrant workers have invested in the construction of the Ming City Wall in Nanjing, about 350 million city bricks, which is the world's longest, largest and best preserved ancient city wall, and was selected as the world's largest city wall of the World Records Association, and the Ming City Wall can stand to this day, only because the Ming Dynasty people used these materials.
Rammed earth, is to compact the soil, make very strong mud blocks, even more solid than masonry, the Ming city wall uses both bluestone bricks and rammed earth, rammed earth is used inside the city wall, the exterior is used bluestone bricks for further stabilization, and in order to prevent cutting corners, craftsmen perfunctory, etc., basically each brick and stone will be engraved with the name of the responsible worker, so that such a Ming city wall can resist cannon stone.
Rammed earth has a long history of use, from the Neolithic age to the 1950s and 1960s has been used on a large scale, the Spring and Autumn Warring States period celebrity Mencius once said: "Shunfa in the mu, Fu said to lift between the plates." "The banzhu is about rammed earth technology.
There is also a material in the Ming City Wall, even modern people are reluctant to use, that is, glutinous rice, although there was no cement concrete at that time, but made of glutinous rice, slaked lime and limestone mixed to make a special concrete, became very viscous, is the main adhesive material, so that the masonry of the Ming City Wall will not deteriorate and damage for a hundred years.
In this regard, the Ming Dynasty's book "Tiangong Kaiwu" records: the ash used for xiang tombs and storage ponds is divided into river sand, loess is divided into two points, glutinous rice, sheep peach vine juice and even, built strong, never broken, known as triad soil.
As we all know, glutinous rice is a kind of food crop, or a very nutritious grain, "Materia Medica" records: glutinous rice as a traditional Chinese medicine, has the effect of warming the spleen and stomach, stopping cold and diarrhea, shrinking stools, collecting self-sweating, and acne. Nowadays, it is certainly reluctant to use glutinous rice in the construction of the city wall.
The scale of the Ming city wall is not small, you can also know that in order to build the city wall, a lot of glutinous rice crops were used, which caused a lot of pressure on the people, in fact, glutinous rice was not used for construction from the Ming Dynasty, dating back to 1500 years ago, construction workers mixed glutinous rice and hydrated lime and limestone into paste, called "glutinous rice mortar", mainly used for the construction of mausoleums, pagodas, walls and so on.
Qin Shi Huang ordered the construction of the Great Wall, which has stood for thousands of years, also because of the use of glutinous rice, a precious material, and only the king can order the use of glutinous rice for large-scale construction, but it makes the people pay serious taxes all year round, but this also shows that China's ancient construction technology is advanced, from the cultural relics that still exist for thousands of years, see the wisdom of the ancients, and the diligence of the working people.