If a mixture of lime and volcanic ash can be used to cement crushed stone to make concrete, it has high strength after hardening and can resist the erosion of fresh water and salt water.

In this era, it was the simplest material used to make a cement house.

However, volcanic materials have their own limitations.

Transportation was still very expensive in the Tang Dynasty, which was also an important reason why the price of grain in Chang'an could not be stabilized.

Abundant yields are cheap, and underharvest is expensive. The cost of shipping in from other places has increased by several times, or even hundreds of times.

There is no volcanic activity near Chang'an, so it is a little difficult to obtain volcanic ash, and it is not suitable for a simple production method, and the hardness will be relatively weak, that is, the soil method is used to make cement, and the limestone clay is ground into powder and then calcined into mature material, and then mixed with some slag to form soil cement.

Basically, powdered water and hard inorganic cementitious materials are stirred to form a slurry, and there are many substitutes, but the strength is different.

In the era when there was no mechanized manufacturing, all simple things would become difficult, and it was extremely difficult to grind millet into flour, not to mention the meticulousness of crushing and crushing stones.

However, to make bricks, you need a lot of firewood.

For ordinary people, it is better to directly use firewood to build houses, which is cheap and practical.

In the first year of Zhenguan of the Tang Dynasty, most of the buildings were one-story buildings, and as for the tall buildings, most of them had relatively high foundations, so they looked magnificent.

A small number of them have two-story buildings, and most of them are plots of land in the city.

For the layman, Fan Jingjing, it shouldn't be a big problem to simply build a first-floor building.

If you want everyone to afford to build a brick house, you can only do it if you have the money to increase the overall production volume.

The form of brick burning instead of firewood is the use of coal, which is an important source of coal near Chang'an, and does not need to be transported from afar.

It's that the pollution of coal is too heavy.

If it is used in large quantities, it will cause the problem of "black capital".

Whether you should use it or not, let the contemporary people decide!

Fan Jingjing looked at her students and felt that it was up to them to decide.

Of course, before deciding on the problem, she wants to give them a big picture, not just see the one-third of an acre in front of them.

As a prince and princess, she is born with an advantage and can have a wide range of thinking space.

"Teacher Jingjing, production will form a cycle, so that everyone can produce more things, isn't everyone working hard now? Isn't what they produce the limit?

In your opinion, don't we all live a very poor life? ”

Fan Jingjing's first lecture was not to explain the principle of building a house, but to put forward the theory of economic circulation.

Looking at the large and small radish heads in front of her, raising her hand to ask questions, Fan Jingjing was quite relieved, her students had not yet reached the point of innumbity.

Fan Jingjing only needs to take one class in ten days, and the class time is concentrated in half a day, what Fan Jingjing wants to explain is the knowledge that is not popular in this era, as for what kind of knowledge it belongs to, there is no limit.

None of Li Shimin's children are simple, whether they are men or women, there have been many stories in history, and even girls, most of them are fornicatory.

The boys lost the political battle.

There are many of them, and because of the rebellion, their fathers took their lives.

Li Shimin's family is a chaotic family, but now the children are still young, everyone looks cute, very cute, and there are no complicated thoughts in their hearts, at most they want to stand out among their brothers and sisters and get more love.

If they don't have the idea that they have to take the throne, won't the world be a better place?

Fan Jingjing wants to let them know that there are still many things in this world that they don't know that are worth studying or exploring.

Li Shimin has been in power for a very long time, these princes and grandsons, if they want to wait until they inherit the throne, they will have to wait for a long time, the sky has nothing to do, and staring at the throne is not a way, even if it is divided, it is just a waste of the court's money.

When Fan Jingjing studied before, she learned the basic subjects well, not to mention that agricultural knowledge has a lot to do in this era, unlike a tool of the times that future generations only lag behind.

Although you look down on agriculture, you can't live without food, just like a chef is very tiring, but a chef who can cook the best food is worth spending a million on a meal.

There is a limit to how much a chef can work in a day, and if you really have a chef's culinary skills, you want to eat a meal, but you have to squeeze your head, and it is inevitable to increase your money.

Fan Jingjing is not ready to manufacture cement buildings in large quantities, in terms of cost, the cement materials that need to be purchased from other places are more expensive materials, but not as good as wood, which can be easily built into houses.

Fan Jingjing is ready to open up a forest area to plant fast-growing trees, which are used as materials for construction, and fast-growing trees are enough for ordinary buildings.