Xie Zili suddenly asked: "Mr. Li, now our Huhai Concrete Technology R&D Center is making rapid progress in high-performance concrete. In particular, self-compacting high-performance concrete is a new type of high-tech concrete with high fluidity without segregation and water leakage at a low water-glue ratio, and can be leveled by self-weight without vibration and filled with model and wrapped steel bars, and this technology can produce excellent concrete of uniform quality. The main performance of self-compacting high-performance concrete is that it does not need to vibrate under its own weight, and fills the formwork space by itself, which can be used for structures that are difficult to pour or even impossible to pour. The concrete structure formed by self-compacting has good mechanical properties and durability properties. It's just that there is no system for this calculation method, do you think we want to do it, is it feasible?"

Li Ruoyu nodded and said: "The mix ratio calculation is the first link to determine the mix ratio of self-compacting high-performance concrete. The mix ratio of self-compacting concrete is very different from that of ordinary concrete, and there is no unified design calculation method. There is no concrete mix that can be used universally in any case, but the mix calculation method for the characteristics and laws of self-compacting high-performance concrete should be able to be found. ”

In 1993, Professor Fu Okamura of the University of Tokyo, Japan, who was the first to propose the mix ratio design method of self-compacting high-performance concrete, first tested the slurry and mortar to detect the compatibility between superplasticizer, cement, fine aggregate and pozzolana admixture, and then carried out the mix ratio test of self-compacting high-performance concrete. The advantage of this method is that it avoids the repetition of the same concrete quality control test, saving time and labor.

The disadvantage of this method is that the mortar and slurry need to be quality controlled before the design of the self-compacting high-performance concrete mix, and many concrete ready mix manufacturers do not have the equipment required to do these tests.

Mix design methods and processes are too complex for practical applications. Professor Fu Okamura also proposed a simple self-compacting high-performance concrete mix ratio, and the amount of coarse aggregate is fixed at 50% of the solid volume. The amount of fine aggregate is fixed at 40% of the volume of the mortar. The volumetric water-cement ratio depends on the nature of the cement and is assumed to be between 0.9 and 1.0. The amount of superplasticizer and the final water-cement ratio are determined according to the need to ensure the self-compacting capacity of the concrete.

These can be used as verification principles for the mix ratio of self-compacting high-performance concrete. In addition, JRMCA proposes a simplified version of the Okamura Fu method, a standardized ratio design method for self-compacting high-performance concrete, which can be used for occasions with a large amount of fine powder admixture and a water-glue ratio of less than 0.30.

The Japan Ready Mixed Concrete Federation proposed a method to fix the volume content of sand and gravel to calculate the mix ratio of high-flow self-filling concrete. The French Road & Bridge Center has developed a mix design method for self-compacting high-performance concrete based on BTRHEOM rheometer and RENELCPC software. But without buying software, the method is difficult for others to use.

Based on the relationship between the blockage volume ratio and the net distance of the reinforcement and the particle size and particle size ratio, the Swedish Institute of Cement and Concrete Research Institute proposed a mix ratio design method for self-compacting high-performance concrete, because the concrete mixed with only coarse aggregate and slurry is easy to lead to the segregation, and it is not very clear how to use this method to carry out evaluative tests.

That's all for later. Now, of course, they won't know about Xie Zili. Li Ruoyu knows this, but it is really difficult to choose which one.

Li Ruoyu thought for a while and said: "We can do some experiments, and the calculation method of the mix ratio is as simple as possible." For example, the amount of coarse aggregate is fixed at 50% of the solid volume. The amount of fine aggregate is fixed at 40% of the volume of the mortar. The volumetric water-cement ratio depends on the nature of the cement and is assumed to be between 0.9 and 1.0. The amount of superplasticizer and the final water-cement ratio are determined according to the need to ensure the self-compacting capacity of the concrete. In this case, you can slowly explore in the experiment, and I believe that you can build a mathematical model. ”

Qin Haijuan seemed to be very interested in this, and she hurriedly asked: "Mr. Li, you can go into more detail, let us also learn the most advanced concrete mix calculation method today." ”

Li Ruoyu smiled bitterly: "I'm just a theoretical assumption. Well, the fixed sand and gravel volume content calculation method is based on the balance relationship between the fluidity, segregation resistance and mix ratio factors of high-flow self-compacting concrete, and on the basis of experimental research, a mixture ratio calculation method that can better adapt to the characteristics and requirements of high-flow self-compacting concrete. The first step is to set the loose pile volume of stones in each cubic meter of concrete to be 0.5-0.55 cubic meters. The amount of stone and the mortar content are obtained. The second step is to set the volume content of sand in the mortar to 0.42-0.44 to obtain the amount of sand and the content of slurry. The third step is to calculate the water consumption and the total amount of cementitious material according to the water-glue ratio and the proportion of admixture in the cementitious material. Finally, the amount of cement and admixture is calculated from the total amount of cementitious material. Got it?"

Qin Haijuan nodded and said: "Well, through the mixture ratio calculated by guò, it seems that we should also optimize the mix ratio of self-compacting high-performance concrete, due to the characteristics of self-compacting concrete, such as the amount of cementing material and the large sand rate, if it is not handled properly, there may be some deficiencies in its stress and deformation performance." In order to ensure the safety and economic applicability of white dense concrete structures, the mix ratio should be further optimized! ”

Li Ruoyu thought for a while and said: "In the case of realizing the uniform molding of concrete by its own weight, reduce the amount of cementing material, reduce the sand rate to improve the stability of concrete volume, and at the same time improve the rationality of the cost of self-compacting concrete." Attention should be paid to the optimization of the mix ratio of self-compacting concrete. The first is to optimize raw materials, optimize aggregate gradation, reduce the amount of cementing material, and ensure the workability of white dense concrete at the same time. Try to reduce the sand rate. ”

looked at Xie Zili and the other three, and even Li Liangfeng was listening attentively.

Li Ruoyu continued: "The second is to add mineral fine mixtures to the concrete mixture, especially fly ash, which can exert its morphological effect, increase the workability of concrete, and save costs. Third, according to the different types of cement used, carefully select the appropriate admixture and carry out the appropriate compounding. The result is a highly efficient composite admixture that meets the specific engineering requirements. Fourth, the workability of self-compacting concrete should be determined by slump, expansion and L-shaped flowmeter with reinforced mesh, and the concrete passes through the reinforcement mesh in the L-shaped flower and finally leveling is an important condition for determining the workability of self-compacting concrete. (To be continued.) )