Of course, Li Zhi should use the best materials to build a city wall for his life.

Li Zhi chose to produce Portland cement, which was simple and durable in the early 19th century cement.

Portland cement costs much lower than Sanhe soil, but the effect is even better than Sanhe soil. Not only does cement need to be used to build city walls, but with the development of Li Zhi's business, the amount of civil engineering projects in various places will definitely not be small in the future, and this kind of cement must be used everywhere.

Limestone and clay are needed to burn Portland cement. After burning, it is equipped with a small amount of gypsum as a retarder. Li Zhi and clay are both extremely cheap things and are easy to get. Li Zhi found a miner to order 100,000 jin of limestone and 30,000 jin of clay, which cost only a few dozen taels of silver. Gypsum also had minerals in the late Ming Dynasty and was used as a medicinal material and was not very expensive. Li Zhi found a big medicine shop in Tianjin and bargained for a price of three cents per jin.

Cement production focuses on grinding and one burning. Before calcining, limestone and clay should be ground into powder. Use 1,300 high-temperature calcining in a cellar. After calcining, the resulting cement should be ground into powder.

Li Zhi built several factories on the outside of the south gate of Fanjiazhuang, with a wall on the outside to be used as a factory for producing Portland cement. There are thirty large stone mills in the factory, pulled by donkeys, specially used to grind fine materials and finished products. Li Zhi hired four lime craftsmen who burned quicklime for three taels of silver and asked them to erect a cellar in the factory to burn cement.

Li Zhi directed the craftsmen to grind the materials into powder, and then prepared limestone in a three-to-one ratio and sent it to the cellar to calcinate. The cellar gradually heated up, calcined at the highest temperature for three hours, and then turned off the heat to obtain clinker like big and small stones. Li Zhi asked the limes to pour the clinker on the stone mill and grind it into powder, and then added some gypsum as a retarder.

Four limestors operated according to Li Zhi's requirements and obtained the first furnace of test items. Li Zhi took it and tried it: add water to stir the cement powder into a paste and applied it to the brick to bond another brick. After the cement was dry, Li Zhi grabbed one brick and lifted the two bricks up.

The second brick can still stick to the first brick at first, but with a slight sway, the second brick will fall off.

The first furnace cement experiment failed and failed.

Li Zhi was a little annoyed. He thought about it and checked the recipe of Portland cement in his memory. After confirming it, Li Zhi felt that the temperature of the cellar might not be enough.

Li Zhi walked to the two-star cellar, looked back and forth, turned around and said to the most experienced craftsman, "Boss Liang, the temperature is not enough now. Can the temperature in your cellar still be increased?"

As an industrial designer, Li Zhi knew the formula of Portland cement, but did not study the laying cellars that burned lime, and could only rely on the craftsmen of this era. After saying this, Li Zhi looked at Boss Liang with a little nervousness.

Boss Liang replied respectfully: "Officials, you can still improve it, but the Lijian needs to be renovated."

Li Zhi was happy on his face, patted Boss Liang on the shoulder, and smiled and said, "Then change it quickly! Hurry up!"

Those lime craftsmen are also old-fashioned and have a lot of experience in controlling Lijian. After three days, they modified Lijian and increased the temperature.

After burning the second furnace again, Li Zhi finally produced the world's first qualified Portland cement.

——————————————
Chapter completed!