naturally, the firmness of the Great Wall built in this way can't be compared with that of modern concrete, and it may be weathered and collapsed after a long time. So far, we have not seen a complete Qin Changcheng.
It is not only ancient China people who use lime as building materials. Lime was used in the construction of pyramids in ancient Egypt and cities in ancient Rome. They mixed sand into the sticky slaked lime, so that this mixture sucked in carbon dioxide in the air and became hard calcium carbonate, thus firmly bonding bricks and gravel together.
The ancient Romans also creatively used volcanic ash as building materials. Volcanic ash mainly contains silicate, which is the fine powder of underground lava, but it is not hard. However, careful ancient Romans found that if volcanic ash is mixed with lime and clay and poured with water, it is a building material with strong adhesive force. Moreover, this material can harden even in water and can be used for underwater construction.
Unfortunately, volcanoes are not everywhere and erupt every day. After all, volcanic ash is very limited, so lime is still the most used building material. It is hard to imagine that this kind of building material, which looks very simple from the eyes of modern people, actually shines in the hands of ancient Romans. For example, the Pantheon, which was built in ancient Rome in the early 2nd century A.D., has a circular base with a diameter of 43 meters as the height of the dome from the ground. Such a large-span vault building is very remarkable even today.
Lime was used for thousands of years, until something bad happened to Smithton.
In 1756, a lighthouse on the British Channel Islands suddenly caught fire and was destroyed. This is terrible. You know, this is the most important lighthouse at the southern end of the English Channel. Without it, it will affect the navigation of countless ships. The British government ordered the engineer Smithton to rebuild the lighthouse as quickly as possible.
Smithton immediately informed that limestone should be transported to the island where the lighthouse is located, so that the stones produced on the island can be bonded and rebuilt after being burnt into lime. Smithton has completed similar projects many times and is full of confidence in completing the reconstruction task as scheduled.
Two weeks later, the limestone arrived and Smithton rushed to the unloading dock. When he saw these limestone sent across the mountains and seas, he couldn't help but exclaim, "What bad luck! Why is this stone black?" It is mixed with too much soil. Isn't it a joke to build a high-standard lighthouse with this raw material? " However, time is no longer allowed to transport high-quality limestone. Smithton has to make do with these inferior raw materials for firing.
Unexpectedly, Smithsonian every cloud has a silver lining. The lime burned with this batch of limestone has surprisingly good performance, and the stones have never been bonded firmly. When the supervisor informed Smithsonian of this unexpected result, he jumped up with surprise: "Ah, Almighty God is protecting me!" Then he calmed down again; "There is something in this lime, so we should check it out." Smithton immediately inspected these limes and found that they were indeed impure, which contained as much as about 2% clay.
"It seems that it is these clays that are regarded as impurities that play a good role." Smithton later consciously matched clay with limestone to calcine it, and the performance of this lime was really ideal. Smithton happily told people about his experience.
Smithton's practice soon spread all over Europe, which aroused many people's interest. People have also succeeded in imitating this method to calcine. Around 182, when Russian architect Chiliyev was engaged in building construction in Moscow, he used this method to burn lime and built many buildings, the most famous of which was to repair the walls of the Kremlin.
"can you make it perform better?" An English craftsman named Aspudin tried to improve Smithton's invention. He thought of the ancient Rome's practice of adding volcanic ash to lime in order to strengthen the adhesion of lime, which led to a new idea: volcanic ash is the product of high-temperature melting and burning of rocks. So, is it similar to volcanic ash to grind the fragments of pottery and bricks into fine powder?
Aspuddin gave it a try, and the effect was really good. Later, he thought that the cinder after high-temperature combustion of coal and the slag from high-temperature smelting in iron-making blast furnace might have similar functions. The experiment also confirmed his idea.
in 1824, based on repeated experiments, Aspuddin summed up the proportion of lime, clay, slag and other raw materials and the method of producing this mixture. Aspudin applied for a patent for his invention, and what was produced with this patent was what we call "cement" today. Because the color and strength of Aspudin cement after hardening are almost the same as the stone produced on Portland Island in England at that time, people call it "Portland cement".
The earliest large-scale application of Portland cement was the construction of a tunnel crossing the Thames. Later, it spread rapidly all over the world, and France and Germany built cement factories in 184 and 1855 respectively. Now, cement has become an indispensable material in modern human life.