Although there are still a few months before the concrete batching plant is completed, Xie Zili also took Qin Haijuan and Li Liangfeng into the busy concrete mix design and trial work. You must know that the design of concrete mix ratio is simple and simple, and it is complicated to say that it is complex.

For a concrete company, a commonly used concrete mix library is necessary. Although the concrete mix ratio can be calculated theoretically, the theoretical calculation is not accurate enough, and there are too many factors that affect the concrete mix ratio, such as cement varieties, cement actual strength, aggregate gradation, cement and admixture adaptability, etc., these are things that need to be tested to allow the mix designer to master.

Only the concrete mix designed for the specific raw materials used and the needs of the project is the real usable mix. Of course, most of the concrete supplied by the ready-mixed concrete plant is ordinary concrete, so the commonly used concrete mix needs to be made before production to form a series.

If there are few varieties of raw materials, then the number of concrete mixtures in the concrete mix library is relatively small, if there are many varieties of raw materials, such as the use of two or three kinds of cement, and the admixtures are two manufacturers, then the number of common mix ratios in the concrete mix ratio library has increased dramatically, even as many as thousands.

Fortunately, in the early nineties, the concrete raw materials available in the Huhai building materials market were still very abundant and relatively cheap. After all, at this time, the ready-mixed concrete industry has just started, the quantity is very small, and the demand for concrete raw materials is also small, so you can choose high-quality concrete raw materials, and the number of raw material suppliers can also be controlled in one or two, and the variety of raw materials is also small.

For example, only one or two kinds of cement are selected, one is admixture, one is ordinary natural medium sand, and one is ordinary limestone continuous graded gravel. That's the case. The number of commonly used mix ratios is not much, at most more than 100.

However, Li Ruoyu introduced high-quality fly ash from the Huhai power plant because he knew how to use high-quality fly ash. It plays a very important role in improving the performance of concrete and reducing the cost of concrete. Now high-quality fly ash is as cheap as Chinese cabbage, dozens of yuan a ton, and one ton of high-quality fly ash can replace 700 to 800 kilograms of cement. The price difference between the two has reached nearly 200 yuan a ton, and the cost savings are naturally considerable.

More importantly, the addition of high-quality fly ash to the concrete can significantly improve the working performance of the concrete and the mechanical properties and durability of the hardened concrete, which can be said to kill two birds with one stone.

Li Ruoyu also joined Xie Zili in their work, after all, Li Ruoyu himself is a technical worker, in his previous life he was also an expert in the concrete industry, with decades of experience, if he does not come to guide, Xie Zili and others of the design concept of the mix is still in the eighties, the level of on-site mixing concrete. How can this work?

In the rented temporary office building in Linjiang Village, Li Ruoyu, Xie Zili, Qin Haijuan and Li Liangfeng are discussing the establishment of the concrete mix ratio library and the trial matching of the concrete mix design.

Li Ruoyu said with emotion: "Everyone, concrete mix design is the core technology of concrete production control, and its technical connotation determines the technical status of the whole production process. Therefore, on the one hand, we must follow the requirements of the concrete mix design specifications, on the other hand, we must also be bold and innovative, and now our country's fly ash concrete application specifications have also been introduced, it is when we vigorously introduce the use of high-quality fly ash, it can not only save costs, but also greatly improve the performance of concrete. All right. Today, we will design a few commonly used concrete mix ratios, and today we will do the pumped concrete mix ratio, from C15 to C50, and the slump is designed according to 120 mm plus or minus 30 mm. ”

Xie Zili nodded and said, "Okay." Then let's do the first one, C15 pumping fly ash concrete mix ratio design. Li Liangfeng, you are in charge of writing and calculation, and this is also a good learning opportunity for you. The first step is to determine the strength of the concrete, and now we do not have the strength number of historical statistics. There is no standard deviation of strength, and the selection can only be made based on the above provisions of the design specification. Li Liangfeng, open the specifications and see how many you should choose? ”

Li Liangfeng was naturally very nervous in his heart, to know that it was the first time for him to really calculate the concrete mix ratio like this, and there were leaders and bosses next to him.

Li Liangfeng opened the thin concrete mix design code and found the concrete mix design steps.

The first step is to calculate the strength of the concrete, which has a formula that takes the standard strength of the concrete plus 1.645 times the standard deviation of the concrete strength. Of course, there is an explanation in the regulations, that is, when there is no historical statistical standard deviation of strength, the value in the specification is used, such as C20 and below strength concrete, and the standard deviation of this strength is 4.0 megapascals.

Li Liangfeng understood it at once, and he had also learned some concrete knowledge, and the regulations were also explained more clearly.

Li Liangfeng thought for a while and replied, "Chief Engineer Xie, should you choose 4.0 megapascals?" If it's a C30, choose 5.0 MPa. ”

Xie Zili glanced at Li Liangfeng with appreciative eyes, and then smiled: "That's right! Looks like you have some foundations. But do you know what this formula means? ”

Li Liangfeng shook his head when he heard this, he really didn't understand this formula too well, why was it 1.645 times the standard deviation of intensity? To add the strength standard value, the strength standard value of C15 is 15 megapascals, he knows.

Xie Zili smiled and said to Qin Haijuan: "Xiao Qin, you can talk about it." ”

Qin Haijuan is an undergraduate student who graduated from inorganic non-metallic materials, and has also worked in the Huhai Concrete Technology R&D Center for a period of time, so she is naturally very clear. After all, Li Liangfeng is just a young man who has not graduated from secondary school.

Li Ruoyu also glanced at Qin Haijuan curiously, to see if she could explain it to someone who didn't understand, this is actually a kind of ability, if a laboratory director in charge of technical work can't effectively guide his subordinates, then he is an incompetent laboratory director.

Li Liangfeng also knows that such an opportunity is rare, when he was in school before, the teacher didn't care about the three-seven-twenty-one, and he finished according to the textbook, but in fact, many of the students below did not understand.

Qin Haijuan also knew that this was Xie Zili testing her, and Li Ruoyu, the boss and senior expert, heard about it on the side, she was also a little nervous, but fortunately, her own theoretical knowledge and skills were also excellent, this was not difficult, the difficulty was how to make Li Liangfeng really understand. (To be continued.) )