Qin Haijuan took out the adjusted mix ratio and said, "Mr. Li, can you help us take a look again, is there any problem with this mix ratio now?"

Li Ruoyu took it with a smile, and then looked at it carefully, and now compared with the preliminary calculation the day before yesterday, some adjustments have been made, one is that the sand rate has been adjusted by two percent, and the second is that the admixture content has been reduced by 0.2 percent, it seems that the problem is mainly focused on these two points.

Li Ruoyu nodded and said: "Okay, I don't think there is basically any big problem, now the trial matching, it should be able to meet the requirements of work performance, and finally determine the mix ratio, but also look at the 28-day intensity, then you can use the drawing method to find the final mix ratio." Let's try it out now!"

A few people moved quickly again.

The sand and gravel are air-dried, and there is no need to calculate the moisture content, so it is very simple to calculate the amount of a trial match, that is, to multiply the theoretical mix ratio by the amount of the test match, 0.02 cubic meters. This job was still handed over to Li Liangfeng, which was a good learning opportunity.

In the process of determining the mix ratio of the concrete strength test, the water-cement ratio, sand rate, water consumption, etc. must be correctly selected according to the design conditions of the concrete mix ratio, which is called the adjustment before the trial.

Li Ruoyu said with a smile: "According to the condition of raw materials to select the appropriate parameters, mix design in the "ordinary concrete mix design regulations", on the selection of parameters, there are some regulations, these regulations, but also based on the experience of production practice, can be used directly, for example, in the determination of water consumption, when using fine sand, the water consumption per cubic meter of concrete can be increased by 5-10kg, when using coarse sand, it can be reduced by 5-10kg, for fluidity, The water consumption of high-fluidity concrete is based on the water consumption of 90mm slump, and the water consumption increases by 5kg for every 20mm increase in slump. ”

Xie Zili nodded and said: "Well, there are also regulations on the selection of sand rate for fine sand or coarse sand. The sand rate can be reduced or increased accordingly. When preparing concrete for single-grain coarse aggregate, the sand rate should be increased appropriately. For thin components, the sand rate is taken as a larger value. These are all determined in the regulations according to the condition of raw materials, the selection of design parameters of the mix ratio. The situations encountered in daily production are often more complex, which requires us to comprehensively consider all aspects of factors and choose design parameters according to the inspection results of raw materials. For the parameters that can be determined according to the inspection results of raw materials, the parameters must be determined after inspection to ensure the reliability of the calculation results of the mix ratio. ”

Qin Haijuan nodded and said, "Fortunately, our current raw materials such as sand and gravel are very stable, and the quality is also reliable." The best Ganjiang medium sand can be purchased in the market, with a fineness modulus of about 2.5, and the gradation is also very good. Of course, the crushed stone comes from Zhoushan, as long as the acceptance of raw materials is carefully done, the quality is controllable, which is for our future production quality control. It's still more advantageous. ”

Indeed, now in the Shanghai building materials market, the source of sand and gravel is very sufficient, unlike more than 20 years later, due to the depletion of natural sand resources, all kinds of unqualified sand are flooding the market, and finally lead to a lot of quality problems.

In order to solve these problems, experts in the concrete industry have found another way, which is to use artificial sand, that is, the sand obtained by crushing stones with machines. Of course, the quality of that kind of sand is also uneven. First, it depends on the quality of the stone, such as the mud content, material and solidity of the stone, and the second is to see the advanced nature of the crushing equipment. And how is the production process.

Of course, the quality of most artificial sand is not as good as that of natural medium sand, so it also needs to be used in combination with natural fine sand and extra-fine sand with poor quality. Of course, there are a few advanced enterprises that use the most advanced artificial sand production equipment and technology to produce high-quality artificial sand. The quality is even better than that of natural medium sand.

This is because of artificial sand, which contains an appropriate amount of stone powder, which can play a filling role in concrete, which is equivalent to poor quality fly ash, if the limestone is broken, this stone powder still has a certain activity, so that later after the fly ash resources were urgent, the concrete industry also used a large number of limestone grinding stone powder as admixture.

In addition, the quality of artificial sand, its gradation is controllable, so that the sand gradation is better, at the same time, because the particle shape of artificial sand has a certain edge, so its grip and wrapping force is stronger, the concrete prepared by this artificial sand is stronger, and the cement is more economical.

Of course, this is when the natural sand resources are exhausted, due to the sharp rise in the price of natural sand, artificial sand has a cost advantage, and now to produce artificial sand, the cost must be much higher than that of natural sand, and it is not economical. Therefore, Li Ruoyu did not consider engaging in an artificial sand production line.

Li Liangfeng was still immersed in calculations, Li Ruoyu said with a smile: "We should do a good job in the analysis of sensitive factors that affect the performance of concrete in our daily life, and when the quality characteristics of raw materials change, we must analyze whether it has an impact on the performance of concrete and the size of the impact." For the factors with greater influence, the regression analysis method can be used to determine the influence of the change of the characteristic value of the raw material on the performance of the concrete, and the specific design calculation of the concrete mix ratio is the influence of the characteristic value of the raw material quality on the selection of design parameters. The design parameters are taken as the dependent variables, and the quality characteristic value of the raw materials is the independent variable, and the corresponding functional relationship is established under the assumption that other factors are relatively stable. The relationship between the characteristic values that have no obvious functional relationship or cannot find the functional relationship, but has a great impact on the performance of concrete, and its relationship with the design parameters can also be expressed in the form of a list of numbers. Through the above means, we can reasonably estimate the influence of the change of a certain factor on the performance of concrete, and make adjustments to the selection of design parameters accordingly. This is the scientific technical quality management, I hope we want to become the leading enterprise in the national concrete industry, these are to walk in front of the peers. ”

Xie Zili nodded: "I think we must also do a good job of technical reserves when the quality of raw materials changes greatly." For example, if the stone grading is not good, and there is no material available if it is refused, the mix ratio should be adjusted according to the production test and statistics, so as to increase the cement dosage of unilateral concrete and reduce the water-cement ratio. To improve the sand rate, the single-grain concrete batching is used, because the void ratio between the coarse aggregates is larger, the sand rate must be improved, and more mortar is used to fill the voids between the coarse aggregates, so as to ensure the compactness and fluidity of the concrete. Of course, there may be other problems, and we must all take them into account and do a good job of technical reserves. ”

Li Ruoyu said with a smile: "Senior Brother Xie, you have thought it through, I completely agree with your suggestion, let you take the lead, and when we have all the personnel, we can carry out these tasks." (To be continued.) )