I! Pretending to Be Reborn, Director of Doomsday Hoax

Xu Qiu's words did not end, he continued:

"Next, the water-binder ratio."

"The greater the water-binder ratio, the more freezable water the concrete contains, and the faster the concrete freezes. As you know, if the water-binder ratio is too high, the cold resistance of concrete mixed with air-entraining agents will not be improved. High?" Yan Yan was stunned.

Prior to this; they paid little attention to the water-binder ratio, just made the water-binder ratio as small as possible to reduce the water content in the concrete.

I never thought that the water-binder ratio is also related to the effect of the air-entraining agent.

But being mentioned by Xu Qiu, Yan Yan immediately began to think.

Suddenly, his eyes brightened, and he said in disbelief: "The air-entraining agent affects the structure of the air cells. The larger the average air-cell distance, the lower the strength of the concrete..."

"But in fact, it is water that directly leads to the collapse of concrete strength!"

"If the water-binder ratio is too high, the impact of water content is greater than that of air bubbles, so the presence or absence of air-entraining agents cannot greatly change the cold resistance of concrete!!"

Xu Qiu nodded in satisfaction, "Exactly."

"When the water-binder ratio changes in the range of 0.45 to 0.85, the frost resistance of the concrete without air-entraining agent does not change much. Only when the water-binder ratio is less than 0.45, the frost resistance will be significantly improved with the decrease of the water-binder ratio."

"Concrete with a water-binder ratio of less than 0.35 has high frost resistance even without air-entraining agents."

"Of course, air-entraining agents can be added, so naturally they should be added, because air-entraining agents have another important function—improving durability!"

"The reason is that the concrete durability index is also a reliable indicator for judging the frost resistance of concrete!"

"Not only the addition of air-entraining agent, but also the reduction of the average bubble spacing"

"Concrete durability index also depends on the water-cement ratio, and the cell spacing is a function of air content and water-cement ratio."

"Therefore, as long as there is a mathematical relationship between the durability index of concrete and the air content and water-cement ratio, based on these relationships, quantitative design can be carried out, and concrete with higher cold resistance can be obtained!"

Yan Yan suddenly realized, and said excitedly: "So that's it! That's it! The water-cement ratio must be lower, and the water-cement ratio must be well controlled!" Xu Qiu ignored Yan Yan's ecstasy, touched his chin, and said in a deep voice : "There is another parameter that needs to find a critical value—air content." Yan Yan once again showed doubts on his face.

"Critical value, what does this mean?"

Xu Qiu asked: "How does your team deal with the air content of concrete now?"

Yan Yan shook his head helplessly, with a self-deprecating smile on his face, "The air content is a hard stubble. Some of the various concretes we make have improved cold resistance because of the air content, but some are more fragile, so we It is thought that air content may not be of much help to cold resistance."

"This kind of uncertainty is a big hidden danger in the actual production process!"

Xu Qiu smiled and said, "That's why I said we must find a critical value!"

"Within a certain range, the more air content, the better the cold resistance of concrete, but if it exceeds this range, the cold resistance will plummet!"

Yan Yan subconsciously asked: "Why?"

"Because! While the air content reduces the average cell spacing, it also reduces the strength of the concrete!"

"If my calculations are correct, for every one percent increase in the air content of the concrete, the compressive strength drops between three and 5.00 percent!"

"That's why some of your concrete is more fragile! Because their air content has exceeded this critical range!"

Yan Yan and the surrounding chairman and executives looked shocked. They looked at Xu Qiu as if they were looking at a master of concrete manufacturing technology...

Gollum.

Yan Yan swallowed his saliva, and asked: "Director Xu, have you...calculated how much gas content is the most optimal?"

Xu Qiu shook his head, "You need to experiment on your own. My estimate is between [-]% and [-]%. Within this range, an increase in air content can improve cold resistance." Yan Yan seemed to have opened a new window. The gate of the world ran away without saying a word.

After a while, he had changed into safety work clothes and a helmet.

Behind him followed four or five of his apprentices, respectively pushing yellow sand, cement, stones, aggregates, etc.

"Director Xu, I'm going to try it myself to see how much air content the concrete has to get better cold resistance!"

"Now, just increase the gas content and test it!"

The increase in gas content is relatively simple.

For example, start with materials.

For example, if the fineness of cement is large and the alkali content is high, the gas content will decrease. At the same dosage, the gas content of Portland cement is higher than that of ordinary cement, slag cement and pozzolanic cement in turn.According to previous research by Yan Yan's team, for every 90kg/m3 increase in cement, the gas content will decrease by about one percent.

Fly ash, one of the materials, also has a strong adsorption effect, which will significantly reduce the air content of concrete. Therefore, when a higher air content in concrete is required, the amount of fly ash should be controlled or the air-entraining agent should be appropriately increased. The dosage.

In addition, the finer the mineral admixture, the smaller the air-entraining amount.

As for the raw material sand and gravel, natural sand has a higher air content than artificial sand. When the particle size of the sand is in the range of 0.3-0.6 mm, the air content of concrete is the largest, and when it is less than 0.3 mm or greater than 0.6 mm, the air content of concrete decreases significantly.

There is actually a critical value here, the larger the sand ratio, the larger the gas content, but when the sand ratio increases to a certain level, the change of the gas content is not obvious.

According to what Xu Qiu said, he controlled the gas content between [-]% and [-]%, and added a control group with less than [-]% and more than [-]%.

The configured concrete mixture is divided into two layers and crashed into the mold, and the thickness of the two layers of filling is controlled to be roughly equal.

Then, stir the tamper, working evenly from the edge to the center in a spiral direction!

Yan Yan is obviously a person who often goes to the field to make adjustments himself, and his movements are very skilled. When inserting the tamping rod, the tamping stick is very vertical, and the other hand is always holding a spatula to scrape the inner wall.

clang clang clang.

There is the sound of the rubber hammer hitting the mold as the concrete fills the gaps left by the tamping.

Yan Yan's expression is focused, his life's dreams are all in this small mold.

As the concrete gradually solidified, he immediately stood up, saluted Xu Qiu, and brought the finished product to the testing room to conduct all-round tests on cold properties, strength, and so on.

More than half an hour later, Yan Yan ran out excitedly, with some mud spots on his face.

"Director Xu...your theory...is correct!"

"Seven point three percent is exactly the air content that can maximize cold resistance!"

"We have improved the concrete according to what you said, and the original cold resistance of minus ten degrees has been directly increased to minus fourteen point three degrees!!"

Yan Yan burst into tears. The dream of this engineer in his life is the concrete that builds the city's tall buildings.

He never expected that at the age of retirement, he would receive such guidance and push his works to a new level!

The eyes of Zou Botao, the chairman of Shenlong Construction and others were full of shock.

It actually...really works!

Yan Yan is one of the most well-known figures in the country who researches concrete technology. Even he has been troubled by the cold resistance breaking through minus ten degrees for a long time. The extreme temperature dropped to minus fifteen degrees!

Compared with the excitement of the crowd, Xu Qiu's expression still didn't change much.

He said lightly: "Follow the steps I have outlined and continue with Gai Ailing."

"The average air cell spacing is controlled below [-] microns, the water-binder ratio is reduced to below [-] as much as possible, the aggregate with high water absorption and no water is selected, and Portland cement is used."

"At the same time, the amount of fly ash must be controlled, and the amount of silicon fume must not exceed [-]%!"

"There are also water-cement ratio, air-entraining agent, slump, temperature, etc. You should be very familiar with these parameters, and they all depend on durability, cold resistance and strength."

"What we want to create is a concrete that can maintain the same performance at room temperature at a low temperature of minus [-] to [-] degrees!"

"It will be called low-temperature reliable concrete from now on."

Xu Qiu was not satisfied with the name of Extreme Cold Concrete.

The severe cold of more than 200 degrees below zero is available, and thirty or forty degrees below zero can only be regarded as low temperature at best.

Yan Yan bowed deeply, and his eyes were full of gratitude and admiration from the students for the teacher: "Thank you, Director Xu, for giving me the name. I, Yan, will definitely develop better low-temperature reliable concrete, which will be used in the Little Ice Age two months later. ...delivering high-quality raw materials to the whole country!"

"When the whole world had to shut down due to the cold and the concrete was frozen and unusable, we in the Dragon Kingdom were stirring concrete in the snow and ice... This will shock the engineering world of the world!!"

Speaking of this, Yan Yan's blood boiled with enthusiasm.

If it can be successfully developed, he, Yan Yan, may be able to become famous in the entire engineering world! !

And all of this stems from that young man...

this day.

The chairman found that Yan Yan seemed to be a different person.

This proud engineer hardly ever leaves his workshop and office.

However, when Xu Qiu took a special plane to leave Shenlong Construction Engineering, he also walked out, stood on the playground, looked up, with a moved expression.

He watched the helicopter getting farther and farther away, with tears streaming down his eyes.

Eagle Country, House of Representatives.

At this moment, the Prime Minister was sitting on the stage with a pale face.He glanced around, and the faces of everyone in the audience were also gloomy.

"This time, our Eagle Country has suffered too much damage."

"However, we have a more dangerous future to face..."

The prime minister knocked on the table in an attempt to cheer everyone up.

But his voice was also weak and unconvincing.

The Little Ice Age, the sun goes out...

It is too difficult for the whole country to carry through these disasters one by one!

A congressman sighed and said: "I hope that the universe will be extinct directly. In this case, no one will have a way out, and we can enjoy the days that follow."

The eagle country sociology research expert stood up and said: "There is no country that can achieve the cohesion like the dragon country. They can build dungeons, but we can't!" This is actually all countries in the world. Except for the dragon country, almost There is no reason why countries build dungeons.

If all other factors are discarded, with the current technology of human beings, before the technology of controlled nuclear fusion and interstellar immigration is mastered,

The most reliable, safest and most comfortable measure is to build dungeons.

However, after countries tried to build dungeons, they discovered several problems.

First: the construction process is too difficult.

The underground city involves many theoretical systems such as deep physics, rock mechanics, geology, underground environmental engineering, underground construction, etc. Moreover, no one, including Longguo, has any experience in building a large underground city!

Although many countries have previously proved the development and utilization of underground space.

For example, Dr. Berry Country demolished the six-lane viaduct passing through the city center and replaced it with an eight- to ten-lane underground expressway.

They turned the original ground into tree-lined roads and street parks, reducing the concentration of carbon monoxide in the urban air by 12.00%.

There is also Sakura Guodong Jindu, which has set up an underground air-inducing machine drainage treatment and ventilation station, through electrostatic dust removal, chemical adsorption, photocatalysis and other technologies to remove harmful components and then discharge them, reducing carbon dioxide by 3.4 tons and nitric oxide by 160 million tons every year , 16 tons of suspended particles, effectively solving the problem of urban air pollution...

However, these facilities all have one thing in common, they only exist as an auxiliary of the above-ground city, and they cannot live in people!

Including the underground streets and underground commercial streets of international cities in various countries, the purpose is to alleviate the sense of congestion caused by the shortage of urban space above ground.