This is a building materials lesson.

With the progress of the lecturer's lecture, a huge electronic screen in the classroom also appeared on some PPT content screens.

The lecturer spoke very carefully and meticulously, and the loud voice echoed in the classroom. However, the students below were not in high spirits listening to the lecture. Perhaps due to lack of sleep, some of the students' bodies were still slightly shaky and their eyes were almost closed.

Perhaps the lecturer is aware of everyone's emotional problems, and he intends to increase some interaction with the students below. So, he quickly asked a question to focus everyone's attention.

"The pouring of concrete has a lot to do with temperature. Generally speaking, the pouring temperature of the mold should not be lower than minus 5 degrees Celsius. In the case of the construction of China's famous Qing-Tibet Railway, due to the long-term cold and freezing there, except in summer, it is usually below zero. So, how did engineers solve this problem of concrete pouring in an extremely cold region? ”

"One way is to use antifreeze admixtures, and the other is to use special cold-proof concrete. However, both of these options would significantly increase the capital budget and would not be practical. But our clever engineers found a different way to solve the problem. Do any of you know what this solution is? "The lecturer on the podium is asking everyone.

The questions asked by the lecturer are not mentioned at all in the textbooks issued by the school. Therefore, the students below cannot find the corresponding answer in the textbook. Some of the students were scrambling through the textbooks, and naturally they couldn't find anything.

This question obviously aroused the interest of the students, and everyone talked a little in a whisper, but they didn't seem to be able to come up with any specific solutions.

The lecturer's eyes were looking forward to it, but the situation below was clearly a little cold.

Yao Yayao, who was busy flipping through another book in the audience, raised his right hand very casually.

"Well, this classmate who raised his hand, please stand up and say something." The lecturer motioned for Yao Yayao to get up and answer the question.

"They set up a boiler on site to heat the stones and sand from the raw materials and then mix them. This solves the problem of low temperatures and reduces the overall cost increase. However, the heating temperature is also limited, and it cannot exceed 60 degrees Celsius, otherwise it will seriously affect the mixing performance of concrete. Yao Yayao replied.

"Very good, this student answered very correctly. Come, tell me your name? The lecturer spoke.

"Yao Yayao". Yao Yayao said his name and sat down. He saw that the lecturer seemed to have something registered on paper.

The classroom burst into applause from the other students. And the lecturer also stared at Yao Yayao with some surprise, his eyes were slightly deep, as if he was a little surprised that he was able to answer this question correctly.

Yao Yayao, who sat down, felt a little lucky. A few days ago, because he was curious, he bought a copy of "The Construction of the Qing-Tibet Railway" in the game world, which happened to mention these details. I can't think of an unintentional move, but now it has made him a little limelight in the classroom.

"Hardly a textbook mentions the idea of heating raw materials for on-site construction. Books are dead, but people are alive. We should be good at prescribing the right medicine to solve the problem, combined with the complex actual environment on the site, and then find the corresponding solution. ”

"In a similar vein to the idea above, when pouring some large dikes, you can also use the method of cooling raw materials. If there is a high temperature difference between the inside and outside, then a large number of penetrating microcracks will appear inside and outside due to the expansion stress during the overall molding. ”

So how do engineers solve this heat dissipation problem? First, on-site ice making can be considered, using ice water to mix concrete, and pre-heat dissipation in advance. Second, a heat dissipation pipe can be reserved in the formwork, and then the cold water circulation in the pipe can be used during the condensation period to take away the huge heat generated inside. After the final molding, all the heat dissipation pipes are blocked with pure concrete. The famous Hoover Dam in 1936 was built using the latter idea of heat dissipation. ”

The lecturer on the stage continued to lecture and showed some pre-prepared live pictures and short videos to the students.

Because what he was teaching at this time was not mentioned in the textbook. Therefore, the students' interest in listening to the lecture was greatly stimulated. Everyone began to listen with relish, and they were no longer so sleepy. And teachers and students have begun to interact with each other more, instead of the rigid mode of you talking and listening.

。。。。。。

After class, Yao Yayao went to a cafeteria in the school to prepare for lunch.

There are five large student dining halls in the school, and this one is the most popular. Not because it's the best food, but because it's the most accessible restaurant. Not only is the price here the cheapest, but the meals are plentiful.

It is said that universities are ivory towers, and there is no dispute with the world, but this is not necessarily the case. With just a small canteen setting, the students have fully reflected the huge class disparity.

For example, another student cafeteria in the school is much more elegantly decorated and has a much richer menu, and students can also order food on the spot and let the chefs stir-fry it. However, the price is not cheap. Such an aristocratic style also attracted many second-generation students from the wealthy class.

Another difference is that there is basically no queue for meals in the student aristocratic restaurant. And the civilian restaurant is a long queue every day.

This is the most affordable student restaurant, and the students who come to eat are far more crowded than the people in the aristocratic restaurant. Yao Yayao waited in line for more than ten minutes before it was finally his turn.

"Shredded potatoes, baby cabbage, scrambled eggs with tomatoes, scrambled pork ears."

As usual, Yao Yayao reported a self-selected dish with three vegetables and one meat. He looked at the plate of golden roasted chicken thighs with some envy, and then reluctantly withdrew his eyes.

He really wanted to order two big chicken legs to feast on it, but he didn't have enough energy. Don't say two, but he can't afford one.

Such a big chicken leg costs 6 yuan. And 5 yuan is already Yao Yayao's entire budget for lunch. His father's living allowance was 1,000 yuan a month, including food and daily necessities. Yao Yayao has to be careful every day, and he can't spend a dime more. Yao Yayao knows the embarrassing economic situation of the family.

Prices are now very expensive, and one-dollar bills have become the smallest currency. A person like Yao Yayao, who only has a living allowance of 1,000 a month, is almost the poorest class in the school.

Suddenly, Yao Yayao remembered the brown paper envelope he had pressed in the drawer. There were three thousand dollars in it. The 3,000 yuan is the creative compensation given to him by his shadow roommate Li Xiaogang. Li Xiaogang used his original children's basketball board idea to set up the "Beautiful Campus" club, which made a splash in the school.

If these 3,000 yuan are converted into fragrant chicken thighs in front of him, there are a total of 500 pieces, which is enough for Yao Yayao to live a full mouth and tongue addiction for a period of time.

But for some reason, Yao Yayao never had any intention of using this money. He would rather have a poor daily meal than use the money for extra meals.

He hadn't thought about what the money was going to be used for, so he put it aside for the time being, ready to use it in case of emergency.

(To be continued)