Cheng Nantong was very happy to see Professor Lin and Li Ruoyu chatting, and said with a smile: "Professor Lin, Mr. Li, you patronize and talk about concrete, and also popularize knowledge for us!" ”

Professor Lin smiled and said, "Let's let Mr. Li say it, to be honest, in terms of some new ideas, I think I am inferior to him!" ”

Li Ruoyu smiled bitterly: "Professor Lin, you are also exalting me too much, in this case I will be proud!" ”

The remark caused everyone to laugh, and the atmosphere became more enthusiastic.

Li Ruoyu said: "High-performance concrete is a new type of concrete developed in recent years. The European Concrete Institute and the International Association of Prestressed Concrete define it as concrete with a water-to-adhesive ratio of less than 0.40, and in Japan, self-compacting concrete with high fluidity is called high-performance concrete. Although in different countries, different scholars or engineers have different understandings of high-performance concrete. For example, American scholars emphasize high strength and dimensional stability, European scholars pay more attention to durability, and Japanese scholars focus on high workability. However, their basic point is high durability, and the understanding of this is the same. ”

"The performance characteristics of high-performance concrete are also significant, durable concrete must be able to resist weathering, chemical erosion, abrasion and other damage processes, which means that high-performance concrete should not only have high strength, but also should have high stiffness, small volume change, in fact impermeable, chloride ions are difficult to penetrate, high elastic modulus, shrinkage creep is small, thermal strain is small. Therefore, high-performance concrete should be different from ordinary concrete in composition and structure, one is durability. The combination of high-efficiency superplasticizer and mineral ultrafine powder can effectively reduce water consumption, reduce the voids inside the concrete, and make the concrete structure work safely and reliably for more than 50~100 years, which is the main purpose of high-performance concrete application. ”

"The second is work. Slump is the main index to evaluate the workability of concrete, the slump control function of high-performance concrete is good, in the process of vibration, high-performance concrete viscosity is large, the sinking speed of coarse aggregate is slow, in the same vibration time, the sinking distance is short, and the stability and uniformity are good. At the same time, due to the low water-cement ratio of high-performance concrete, less free water, and mixed with ultra-fine powder, there is basically no water secretion, and the viscosity of its cement slurry is large, and the phenomenon of segregation is rarely produced. ”

"The third is mechanical properties. Because concrete is a heterogeneous material, the strength is affected by many factors, the water-cement ratio is the main factor affecting the strength of concrete, for ordinary concrete, with the reduction of water-cement ratio, the compressive strength of concrete increases, and the high-efficiency superplasticizer in high-performance concrete has strong dispersion ability and high water reduction rate to cement, which can greatly reduce the unilateral water consumption of concrete. The addition of mineral ultrafine powder to high-performance concrete can fill the voids between cement particles, improve the interface structure, improve the compactness of concrete, and improve strength. ”

"Fourth, the volume is stable. High-performance concrete has high volume stability, that is, concrete should have a low heat of hydration in the early stage of hardening, and a small shrinkage deformation in the later stage of hardening. Fifth, economy. The high strength, good durability and manufacturability of high-performance concrete can make it economical. The good durability of high-performance concrete can reduce the maintenance cost of the structure, prolong the service life of the structure, and receive good economic benefits; The high strength of high-performance concrete can reduce the size of components, reduce their own weight, and increase the use of space; Good workability can reduce the work intensity of workers, speed up the construction speed, and reduce costs. ”

After Li Ruoyu finished speaking, everyone applauded.

Professor Lin nodded and said, "Yes, Li Gong summed it up very well!" Let me talk about one of the key indicators of high-performance concrete, the resistance to chloride ion penetration, and the foreign electricity flux index to detect. The electric flux index is the most important and specific indicator of the durability of concrete. At present, there is no national standard for electric flux test in China, and the United States has a ASTMC1202 rapid electric power measurement method, which can be used to distinguish and evaluate the compactness of concrete, and the compactness is the most critical factor affecting the durability of concrete. In the past, the impermeability of concrete was mostly evaluated by impermeability, but practice has proved that the impermeability test is only suitable for judging the compactness of concrete of lower strength grades, and when the strength grade exceeds C30, the impermeability grade can almost reach more than P20, and it is more difficult to test it downward. This is the main reason why the electrical flux index replaces the impermeability mark as the durability control of concrete. The electric flux of concrete mainly depends on the water-glue ratio, and a large number of tests have obtained the law, generally when the water-glue ratio is less than 0.5, it can basically meet the requirements of the electric flux less than 2000, and when the water-glue ratio is less than 0.45, it can basically meet the requirements of the electric flux less than 1500. Nowadays, the development of high-performance concrete in China is relatively good, and there is a lot of space, but it is still necessary to understand and practice the process of understanding and practicing high-performance concrete in construction projects. With the continuous enhancement of China's construction infrastructure, high-performance concrete will become an important construction engineering material in the new century. ”

Li Ruoyu nodded and said: "Yes, it is precisely because of this that I have an idea that concrete production must enter the modern large-scale industrial and group-type industrial production from decentralized, semi-mechanical workshop-type production, including the concrete industry group integrating the upstream and downstream industries of concrete production, and I plan to initially build a concrete industry group in the next five years." In the future, a large number of high-tech concrete varieties will continue to emerge; High durability, high workability, light weight and high strength have become the achievable goals of engineering concrete; A large number of high-rise buildings, long-span bridges, large water conservancy and hydropower dams, highways and railways, and low-carbon energy-saving and environment-friendly concrete buildings will become important symbols of civilization in the 21st century. ”

"At the same time, the concrete industry is facing unprecedented sustainability challenges. It is necessary to find a solution to the contradiction between two equally important social needs: infrastructure development and the protection of the environment and resources. As an important participant in infrastructure construction, an important consumer of the earth's natural resources and a giver of damage to the ecological environment, the concrete industry needs to have a clear positioning and accept all process technologies that are conducive to environmental and resource protection, that is, environmentally friendly concrete technology. They should be built on the basis of the following four basic elements: first, vigorously save concrete raw materials and energy; the second is to strive to improve the durability of concrete works and structures; the third is to properly solve the ecological and environmental protection problems in concrete production, including the production of its raw materials, and use; Fourth, actively look for new materials that can replace or partially replace concrete raw materials, especially cement. I believe that the future of the concrete industry is definitely bright, and the development potential is also huge. ”

As soon as Li Ruoyu's words fell, he won the applause of everyone present! Especially Mi Yun and Qin Haijuan, they are all loyal followers of Li Ruoyu! (To be continued.) )