Mechanism sand tailings fine powder concrete mix proportion design method

Abstract

The application discloses a kind of mechanism sand tailings fine powder concrete mix proportion design method, and the design method of mechanism sand tailings fine powder content includes: S1, determine the initial proportion of cement and mechanism sand tailings fine powder in concrete mix proportion, add water and cement, mechanism sand tailings fine powder is mixed, and mixed material is obtained;S2, fill standard test container;S3, calculate the packing density of mixed material;S4, gradually reduce the amount of water, repeat S1-S3, obtain the closest packing density of cement and mechanism sand tailings fine powder initial proportion;S5, change the proportion of mechanism sand tailings fine powder, repeat S1-S4, obtain the closest packing density of different cement and mechanism sand tailings fine powder proportion, determine the mixing amount ratio of mechanism sand tailings fine powder in cement.The method can fully consider the filling effect of mechanism sand tailings fine powder in concrete cementing system, and more accurately control the mixing amount range of mechanism sand tailings fine powder in concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for designing the mix proportion of finely ground concrete from manufactured sand tailings. Background Technology

[0002] Natural sand is a non-renewable local resource. With the increasing scale of national infrastructure construction and the gradual strengthening of farmland and river protection measures, the use of natural sand resources is restricted. As a substitute for natural sand, manufactured sand is increasingly used in concrete. The production process of manufactured sand inevitably generates a large amount of manufactured sand tailings, which are composed of limestone. Large quantities of limestone manufactured sand tailings cause environmental pollution problems. Previously, landfilling was the primary disposal method, but this seriously affects the ecological restoration of arable land and forest land. The environmental pollution and resource waste problems caused by manufactured sand tailings have become very serious. To improve the utilization efficiency of limestone manufactured sand tailings, the current treatment method is to grind them to form limestone powder that meets the requirements of GB / T35164-2017, "Limestone Powder for Cement, Mortar and Concrete". Generally, the particle size of manufactured sand tailings is less than 75μm. After grinding, it becomes less than 30μm, which is called finely ground manufactured sand tailings powder, used in concrete mix design.

[0003] In traditional concrete mix design, the dosage of limestone tailings fine powder is determined by strength tests of mortar blocks or strength-activity tests after concrete trial mixing. The appropriate dosage is then determined through comparison. Mortar block strength testing involves preparing blocks by mixing concrete with different formulations and then testing the strength of the blocks. This method is labor-intensive and time-consuming. Concrete trial mixing strength-activity tests determine the dosage by measuring the activity of different concrete formulations. However, since limestone tailings fine powder is an inert admixture and does not undergo hydration, its main function in cementitious materials is to fill and compact. Therefore, determining the dosage by measuring its activity is unreasonable.

[0004] Therefore, existing methods for determining the dosage of finely ground manufactured sand tailings lack consideration of the improvement in the compactness of the cementitious material packing system by the finely ground manufactured sand tailings. Secondly, traditional concrete mix design lacks analysis of the appropriate particle size distribution of finely ground manufactured sand tailings in the cementitious material. Therefore, the packing density of the concrete solid particle system is not considered from the perspective of the combination of finely ground manufactured sand tailings, cement, and coarse and fine aggregates, which lacks guidance for the design of concrete mix proportions. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned deficiencies in the prior art and provide a method for designing the mix proportion of finely ground manufactured sand tailings concrete, that is, a method for designing the dosage of finely ground manufactured sand tailings and the mix proportion of concrete. Considering the improvement of the compactness of the cementitious material mass by finely ground manufactured sand tailings, the dosage is more in line with the filling effect of finely ground manufactured sand tailings in the concrete cementitious system, and can provide guidance for the dosage range of finely ground manufactured sand tailings in concrete.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for designing the admixture dosage of finely ground manufactured sand tailings in concrete includes the following steps:

[0008] Step S1: Determine the initial ratio of cement and finely ground manufactured sand tailings in the concrete formula according to the designed concrete strength. Weigh the cement and finely ground manufactured sand tailings according to the initial ratio, add water and mix with the cement and finely ground manufactured sand tailings to obtain a mixture. The added water makes the cement and finely ground manufactured sand powder fluid.

[0009] Step S2: Fill the standard test container with the mixture and weigh the standard test container after it is filled.

[0010] Step S3: Calculate the bulk density of the mixture according to the bulk density formula;

[0011] Step S4: Gradually reduce the amount of water added in step S1, and repeat steps S1 to S3 to obtain the packing density of the mixture with different water-cement volume ratios under the initial ratio of cement and machine sand tailings fine powder. The maximum packing density is taken as the densest packing density of the initial ratio of cement and machine sand tailings fine powder.

[0012] Step S5: Change the ratio of cement to finely ground manufactured sand tailings, and repeat steps S1 to S4 above to obtain the maximum compaction density under different cement to finely ground manufactured sand tailings ratios. Use the cement to finely ground manufactured sand tailings ratio corresponding to the maximum maximum compaction density to determine the amount of finely ground manufactured sand tailings in the concrete mix design.

[0013] In the above technical solution, the initial ratio of cement and finely ground manufactured sand tailings is first determined. The cement and finely ground manufactured sand tailings that meet the initial ratio are then mixed with water. The amount of water added is based on the standard that water enables the cement and manufactured sand powder to have fluidity. The mixture is placed in a standard testing container, and various parameters are obtained to calculate the bulk density of the mixture. Then, the bulk density of the mixture is calculated by changing the amount of water used, in order to obtain the densest packing density under the initial ratio of cement and finely ground manufactured sand tailings. The densest packing density under different ratios of cement and finely ground manufactured sand tailings is also calculated, thereby determining the proportion of finely ground manufactured sand tailings, i.e., the dosage of finely ground manufactured sand tailings. This invention utilizes the filling effect of finely ground manufactured sand tailings in the concrete cementitious system, providing a novel design approach for concrete mix design based on finely ground manufactured sand tailings.

[0014] It should be noted that the finely ground powder of manufactured sand tailings refers to powder with a particle size of less than 75μm after grinding during the sand making process, with a particle size range of D90 < 30μm.

[0015] As a preferred embodiment of the present invention, the density of the finely ground cement and manufactured sand tailings powder is measured before determining the initial ratio of the cement and manufactured sand tailings powder.

[0016] As a preferred embodiment of the present invention, in step S1, when water, cement and manufactured sand tailings are mixed, a slurry preparation device is used to stir the water, cement and manufactured sand tailings.

[0017] As a preferred embodiment of the present invention, the standard test container is a cuboid, and the size of the cuboid is determined according to the project and test requirements.

[0018] As a preferred embodiment of the present invention, the formula for packing density is as follows:

[0019]

[0020] Where Φ is the packing density; M1 is the mass of the standard test container; M2 is the mass of the standard test container after being filled with the mixture; V is the volume of the standard test container; ρ c ρ is the density of cement. s The density of the finely ground manufactured sand tailings; ρ w The density of water; u w The water-cement volume ratio of the standard test container is the volume ratio of water to cementitious materials in the concrete mix design; R c R is the volume ratio of cement to cementitious materials. s The volume ratio of finely ground manufactured sand tailings to cementitious materials.

[0021] As a preferred embodiment of the present invention, in step S3, during the process of filling the standard test container, vibration is performed to remove air bubbles, and excess paste is scraped off.

[0022] A second aspect of the present invention also provides a method for designing concrete mix proportions, comprising the following steps:

[0023] Step 1: Conduct particle size distribution tests on cement, coarse aggregate, and fine aggregate in the concrete mix design, respectively. The fine aggregate includes manufactured sand.

[0024] Step two: Based on the particle size distribution of cement, coarse aggregate, and fine aggregate, the theoretical cumulative passing rate for different particle sizes is calculated using a packing formula. Cement, coarse aggregate, and fine aggregate are mixed in a specific ratio to obtain mixed granular material. The actual cumulative passing rate for different particle sizes of the mixed granular material is then obtained based on the particle size distribution and ratio of cement, coarse aggregate, and fine aggregate. The expression for the packing formula is as follows:

[0025]

[0026] Where CPFT is the theoretical cumulative throughput for particles smaller than D; D L Maximum particle size; D S is the minimum particle size; q is the particle size distribution index, and the value of q is determined according to different strength grades of concrete, with a range of 0.27 to 0.35.

[0027] Step 3: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput for different particle sizes of the mixed granules;

[0028] Step 4: Adjust the mixing ratio of cement, fine aggregate, and coarse aggregate. Repeat steps 2 and 3 to obtain the sum of squares of the differences in the mixed aggregates under different mixing ratios. When the sum of squares of the differences is the smallest, the mixing ratio of cement, fine aggregate, and coarse aggregate is the mix ratio of cement, fine aggregate, and coarse aggregate in the concrete mix proportion.

[0029] Step 5: Using the above-mentioned design method for the dosage of finely ground manufactured sand tailings in concrete, the dosage of finely ground manufactured sand tailings is obtained, and the mix proportion of finely ground manufactured sand tailings in the concrete mix proportion is calculated.

[0030] As a preferred embodiment of the present invention, the coarse aggregate includes large stones, medium stones, and small stones.

[0031] As a preferred embodiment of the present invention, in step one, the particle size distribution of cement particles is determined by a laser particle size analyzer, and the particle size distribution of the coarse aggregate and the fine aggregate is determined by sieving.

[0032] As a preferred embodiment of the present invention, when the designed concrete strength is C30, q is 0.32; when the designed concrete strength is C40, q is 0.3; and when the designed concrete strength is C50, q is 0.28.

[0033] As a preferred embodiment of the present invention, in step five, before obtaining the amount of finely ground manufactured sand tailings in the concrete mix proportion, when there are at least two types of finely ground manufactured sand tailings with different particle size distributions, it is also necessary to determine the optimal particle size distribution of the finely ground manufactured sand tailings in the concrete. The method for determining the optimal particle size distribution of the finely ground manufactured sand tailings includes the following steps:

[0034] Step 51: Perform particle size distribution tests on the finely ground sand tailings with different particle size distributions used in the concrete mix proportions.

[0035] Step 52: Mix the finely ground manufactured sand tailings with the cement, fine aggregate and coarse aggregate proportions in the concrete mix proportion determined in Step 4, and calculate the actual cumulative pass rate after mixing.

[0036] Step 53: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput after adding finely ground sand tailings with different particle size distributions;

[0037] Step 54: Determine the optimal particle size distribution of the finely ground powder of the manufactured sand tailings by using the particle size distribution corresponding to the minimum sum of squares of the differences between the manufactured sand tailings, cement, fine aggregate and coarse aggregate mixture.

[0038] As a preferred embodiment of the present invention, the particle size distribution of the finely ground manufactured sand tailings is determined by a laser particle size analyzer.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. This invention provides a mix design method for finely ground manufactured sand tailings in concrete. This method can fully consider the filling effect of finely ground manufactured sand tailings in the concrete cementitious system, guide the determination of the dosage of inert admixtures in cement and concrete, more accurately control the dosage range of finely ground manufactured sand tailings in concrete, provide a reference for determining the dosage of finely ground manufactured sand tailings in concrete, improve the efficiency of concrete mix design, increase the utilization efficiency of concrete raw materials and concrete strength, tap the potential of raw materials, and save concrete preparation costs.

[0041] 2. This invention provides a method for designing concrete mix proportions. This method can simultaneously consider the compact packing of cement, coarse aggregate, and fine aggregate system, which can effectively reduce the amount of cement in the system and improve the efficiency of mix proportion design. Attached image description:

[0042] Figure 1 To incorporate D 90 Curves showing the actual cumulative throughput and theoretical cumulative throughput of 28μm machine-made sand tailings fine powder;

[0043] Figure 2 To incorporate D 90 Curves showing the actual cumulative throughput and theoretical cumulative throughput of 12μm machine-made sand tailings finely ground powder;

[0044] Figure 3 To incorporate D 90 Curves showing the actual cumulative throughput and theoretical cumulative throughput of 5μm machine-made sand tailings finely ground powder;

[0045] Figure 4 To incorporate D 90 Curves showing the actual cumulative throughput and theoretical cumulative throughput of 2μm machine-made sand tailings finely ground powder;

[0046] Figure 5 This is a flowchart illustrating the method for determining the amount of finely ground manufactured sand tailings in concrete mix proportions according to the present invention. Detailed Implementation

[0047] To more clearly describe the inventive objectives, technical solutions, and advantages of the specific embodiments of this invention, the solutions in the specific embodiments will be described in detail below with reference to the accompanying drawings. The specific technical solutions involved in the following embodiments are merely for the purpose of clearly and completely describing the innovative technical solutions of this invention. They are only a part of the specific implementation methods that this invention can adopt, not all embodiments, and should not be construed as limiting the innovative solutions of this invention. Any solution that adopts the same inventive concept as this invention should be included within the protection scope of this invention.

[0048] Secondly, the descriptions in the accompanying drawings of the specific embodiments of this invention are merely for the convenience of those skilled in the art to understand the invention. The details shown in the drawings are for the purpose of clearly presenting the technical solution, and should not be construed as including all technical features in the drawings in the specific implementation examples, nor should the details in the drawings be considered as additional limitations on the innovative technical solution of this invention. The components in the various embodiments described and shown in the drawings can be combined and arranged in different configurations. These variations in combination and arrangement should be considered as part of all embodiments of the innovative solution of this invention and included within the scope of protection of this invention.

[0049] In summary, the solutions or descriptions presented in the specific embodiments and accompanying drawings of this invention are not intended to limit the scope of protection claimed, but merely to illustrate selected embodiments / examples to help those skilled in the art understand the relevant innovative solutions. All other equivalent or parallel embodiments obtained by those skilled in the art based on these embodiments without inventive effort are within the scope of protection claimed by this invention.

[0050] Example 1

[0051] This embodiment provides a method for designing concrete mix proportions, including the following steps:

[0052] Step 1: The particle size distribution of cement, coarse aggregate, and fine aggregate in the concrete mix design is tested. The coarse aggregate includes manufactured sand; the fine aggregate consists of large, medium, and small stones. The particle size distribution of cement is determined by a laser particle size analyzer, and the particle size distribution of the coarse and fine aggregates is determined by sieving.

[0053] Step two: Based on the particle size distribution of cement, coarse aggregate, and fine aggregate, the theoretical cumulative passing rate for different particle sizes is calculated using a packing formula. Cement, coarse aggregate, and fine aggregate are mixed in a specific ratio to obtain mixed granular material. The actual cumulative passing rate for different particle sizes of the mixed granular material is then obtained based on the particle size distribution and ratio of cement, coarse aggregate, and fine aggregate. The expression for the packing formula is as follows:

[0054]

[0055] Where CPFT is the theoretical cumulative throughput for particles smaller than D; D L Maximum particle size; D S q is the minimum particle size; q is the particle size distribution index, which is determined according to different strength grades of concrete, and the value of q ranges from 0.27 to 0.35.

[0056] In production practice, the inventors discovered that when the particle size distribution index q is 0.37, the solid particle packing is at its densest state. However, considering the workability of concrete and the actual conditions of water mixing, the value of the particle size distribution index q needs to be adjusted according to the actual situation. The commonly used concrete strength grades in concrete production are C30 / C40 / C50. Through actual concrete mix design tests (concrete slump 180mm±20mm) and the deviation of later strength, the inventors determined the particle size distribution index corresponding to different concrete strength grades as follows: when the designed concrete strength is C30, the particle size distribution index q is 0.32; when the designed concrete strength is C40, the particle size distribution index q is 0.3; and when the designed concrete strength is C50, the particle size distribution index q is 0.28.

[0057] In the above calculations, the theoretical cumulative throughput is calculated using the packing formula. The influencing factors are only the maximum and minimum particle sizes and the q value of all materials. Once the particle size distribution of cement, coarse aggregate, and fine aggregate is determined, the theoretical cumulative throughput curve composed of the theoretical cumulative throughput of different particle sizes is determined. The actual cumulative throughput is obtained through testing and sieving. The actual cumulative throughput will change according to different proportions, thereby allowing for adjustment and determination of appropriate material proportions by referring to the theoretical cumulative throughput curve.

[0058] Step 3: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput for different particle sizes of the mixed granules;

[0059] Step 4: Adjust the mixing ratio of cement, fine aggregate, and coarse aggregate. Repeat steps 2 and 3 to obtain the sum of squares of the differences in the mixed aggregates under different mixing ratios. When the sum of squares of the differences is the smallest, the mixing ratio of cement, fine aggregate, and coarse aggregate is the mix ratio of cement, fine aggregate, and coarse aggregate in the concrete mix proportion.

[0060] Step 5: Using the above-mentioned design method for the mix proportion of finely ground manufactured sand tailings in concrete mix proportions, the dosage of finely ground manufactured sand tailings in concrete mix proportions is obtained.

[0061] The method described above determines the mix proportions of cement, fine aggregate, and coarse aggregate. These proportions represent the ratios of different raw materials. In practical applications, the usage mass of different raw materials can be obtained based on the total mass of solid particles in concrete of different strength grades. The design method using finely ground manufactured sand tailings yields the dosage of finely ground manufactured sand tailings, which is the ratio of finely ground manufactured sand tailings to cement. Based on the determined cement mix proportion, by substituting cement by equal mass, the mix proportion of finely ground manufactured sand tailings in the concrete mix can be determined.

[0062] After determining the mix proportions of finely ground manufactured sand tailings, cement, fine aggregate, and coarse aggregate, the mix proportions of other raw materials in the concrete mix proportions, such as water, water-reducing agent, and added fibers, can be determined based on engineering experience or existing methods.

[0063] In some embodiments, in order to optimize the concrete mix proportion, after initially determining the concrete mix proportion using the above method, a trial mix is ​​conducted based on the concrete formula, and then the concrete sand ratio and cement content are reasonably adjusted based on the trial mix to obtain the final concrete mix proportion.

[0064] In the concrete mix design process, it is necessary to adjust the mixing ratio of cement, coarse aggregate, and fine aggregate to obtain the sum of squares of the differences between the actual cumulative passing rate and the theoretical cumulative passing rate of the mixed aggregates with different ratios. When the designed concrete strength is C30, q is taken as 0.32, and the sand ratio does not exceed 45%. The results of the mixed aggregates with different ratios are shown in Table 1 below:

[0065] Table 1. Cumulative Pass Rate of Mixed Granular Materials with Different Proportions

[0066]

[0067] As shown in Table 1, the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput of the mixed granular materials at ratios 1-5 is the smallest. Having determined the mix proportions of other raw materials using existing technology, the resulting concrete mix proportion, excluding finely ground manufactured sand tailings, is: cement 294 kg, manufactured sand 883 kg, small aggregate 352 kg, medium aggregate 398 kg, large aggregate 321 kg, water 153 kg, and water-reducing agent 5.95 kg. Table 2 shows the performance of concrete mix proportions for different strength grades obtained using this design method.

[0068] Table 2 Performance of Concrete Mix Proportions for Different Strength Grades

[0069]

[0070] Example 2

[0071] This embodiment provides a design method for the dosage of finely ground manufactured sand tailings in concrete, used to determine the dosage of finely ground manufactured sand tailings in the concrete mix proportion.

[0072] This embodiment contains four different batches of finely ground limestone tailings. Each batch of finely ground limestone tailings has a different particle size distribution. The Dg of the four different batches of finely ground limestone tailings is... 90 The particle size distributions of finely ground manufactured sand tailings (28μm, 12μm, 5μm, and 2μm) have different effects on improving the density of the cementitious material packing system in concrete mix proportions. Therefore, before designing the mix proportion of finely ground manufactured sand tailings, it is necessary to determine the optimal particle size distribution of the finely ground manufactured sand tailings in the concrete mix proportion. The method for determining this distribution includes the following steps:

[0073] Step 51: The particle size distribution of the finely ground manufactured sand tailings with different particle size distributions used in the concrete mix design is tested; the particle size distribution of the finely ground manufactured sand tailings is determined by a laser particle size analyzer; in this embodiment, the finely ground manufactured sand tailings have four particle size distributions.

[0074] Step 52: Mix the finely ground manufactured sand tailings with the cement, fine aggregate and coarse aggregate proportions in the concrete mix proportion determined in Step 4, and calculate the actual cumulative pass rate after mixing.

[0075] Step 53: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput after adding finely ground sand tailings with different particle size distributions;

[0076] Step 54: Determine the optimal particle size distribution of the finely ground powder of the manufactured sand tailings by using the particle size distribution corresponding to the minimum sum of squares of the differences between the manufactured sand tailings, cement, fine aggregate and coarse aggregate mixture.

[0077] Figures 1-4 To determine the theoretical packing curves of finely ground sand tailings with different particle size distributions using the above-mentioned method, Figure 1 D of the fine powder of medium-sized machined sand tailings 90 =28μm, Figure 2 D of the fine powder of medium-sized machined sand tailings 90 =12μm, Figure 3 D of the fine powder of medium-sized machined sand tailings 90 =5μm, Figure 4 D of the fine powder of medium-sized machined sand tailings 90 =2μm, from the figure we can see that when the particle size distribution of the finely ground powder of the manufactured sand tailings is D 90 When the value is 2μm, the sum of squared differences is minimized, therefore, D is determined. 90 The particle size distribution corresponding to 2μm is the optimal particle size distribution for finely ground manufactured sand tailings. During the experiment, considering the energy consumption of the manufactured sand tailings grinding device and project schedule, finely ground manufactured sand tailings with smaller particle size distributions were not considered. The optimal particle size distribution for finely ground manufactured sand tailings determined in this embodiment is D. 90 =2μm, and then determine the mix ratio of the finely ground powder of the manufactured sand tailings.

[0078] like Figure 5 As shown, a method for designing the admixture dosage of finely ground manufactured sand tailings includes the following steps:

[0079] Step S1: Determine the initial ratio of cement and finely ground manufactured sand tailings in the concrete mix proportion based on the designed concrete strength. In this embodiment, the finely ground manufactured sand tailings used has the optimal particle size distribution determined in Example 1, specifically particle size distribution D. 90 =2μm finely ground cement and finely ground sand tailings powder; before the initial ratio of cement and finely ground cement and finely ground sand tailings powder, the density of the cement and finely ground sand tailings powder is determined, wherein the density of the cement and finely ground sand tailings powder is determined by GB / T208-2014 "Cement Density Test Method".

[0080] After determining the initial ratio of cement and manufactured sand tailings powder, weigh the cement and manufactured sand tailings powder according to the initial ratio, wherein the mass of cement used is M. C The mass of the finely ground manufactured sand tailings is M. S Add water and mix with cement, manufactured sand tailings, and finely ground powder. Record the mass of water added as M. w The added water makes the cement and manufactured sand powder fluid; it is enough to make it initially fluid, and too much water is not advisable. A paste mixer is used to mix the water, cement, and manufactured sand tailings powder to obtain the mixture.

[0081] Step S2: Fill the standard test container with the mixture after paste filling. Vibrate the container to remove air bubbles during the filling process, and scrape off any excess paste. Weigh the standard test container after filling.

[0082] The standard test container used in this embodiment is a container that can measure volume, specifically a cuboid, the size of which is determined according to the project and test requirements.

[0083] Step S3: Calculate the bulk density of the mixture according to the bulk density formula; the bulk density formula is as follows:

[0084]

[0085] Where Φ is the bulk density; M1 is the mass of the standard test container; M2 is the mass of the standard test container after filling with the mixture; V is the volume of the standard test container; ρc is the density of cement; ρs is the density of the finely ground manufactured sand tailings; ρw is the density of water; u w Rc is the volume ratio of water to cementitious material in the standard test container; Rs is the volume ratio of cement to cementitious material; Rs is the volume ratio of finely ground manufactured sand tailings to cementitious material.

[0086] Step S4: Gradually reduce the amount of water added and repeat steps S12 to S3 above to obtain the packing density of the mixture with different water-cement volume ratios under the initial ratio of cement and machine sand tailings fine powder. The maximum packing density is taken as the densest packing density of the initial ratio of cement and machine sand tailings fine powder.

[0087] Step S5: Change the proportion of finely ground manufactured sand tailings in the concrete mix proportion, and repeat steps S1 to S4 above to obtain the maximum compaction density under different cement and finely ground manufactured sand tailings ratios. Use the cement and finely ground manufactured sand tailings ratio corresponding to the maximum maximum compaction density to determine the mix proportion of finely ground manufactured sand tailings.

[0088] The concrete strength grade designed in this embodiment is C30. Except for the proportion of finely ground manufactured sand tailings, the original concrete mix proportion is: cement 323 kg, manufactured sand 840 kg, small aggregate 214 kg, medium aggregate 534 kg, large aggregate 321 kg, water 168 kg, and water-reducing agent 4.84 kg. Using the design method of Example 1, and combined with the actual concrete water-cement ratio and water-reducing agent dosage, trial mixing was carried out, and the sand ratio was appropriately adjusted to meet the relevant requirements for concrete workability. The improved concrete mix proportion is: cement 294 kg, manufactured sand 883 kg, small aggregate 352 kg, medium aggregate 398 kg, large aggregate 321 kg, water 153 kg, and water-reducing agent 5.95 kg. The amount of finely ground manufactured sand tailings in the original and improved concrete mix proportions has not yet been determined. Using the above-mentioned mix proportion design method for finely ground manufactured sand tailings, the results of the most compacted packing density under different cement and finely ground manufactured sand tailings ratios are shown in Table 3. Thus, it is determined that when the concrete strength grade is C30, the amount of finely ground manufactured sand tailings in the concrete mix proportion and the improved concrete mix proportion is 10%.

[0089] Table 3. Results of the densest packing density under different ratios of cement and manufactured sand tailings fine powder.

[0090] Serial Number Cement admixture Dosage of finely ground manufactured sand tailings Maximum packing density 2-1 100％ 0 0.553 2-2 95％ 5％ 0.568 2-3 90％ 10％ 0.576 2-4 85％ 15％ 0.570 2-5 80％ 20％ 0.557

[0091] To verify the effect of the mix proportion of finely ground manufactured sand tailings, performance tests were conducted on concrete with different mix proportions. The small stone particle size used was 4.75mm to 9.5mm, the medium stone particle size was 9.5mm to 16mm, and the large stone particle size was 16mm to 31.5mm. The different concrete mix proportions are shown in Table 4, and the performance test results are shown in Table 5. It can be seen from the table that when the optimal mix proportion of finely ground manufactured sand tailings is 10%, the concrete has better strength performance.

[0092] Table 4. Mix proportions for C30 manufactured sand tailings finely ground concrete (unit: kg)

[0093]

[0094] Table 5. Strength properties of C30 concrete with different mix proportions (unit: MPa)

[0095] Serial Number 7d strength 28d strength Remark 2-1 37.3 46.8 Original concrete mix proportions 2-2 38.2 46.9 The original concrete mix proportion includes 5% finely ground manufactured sand tailings. 2-3 39.8 47.9 The original concrete mix proportion includes 10% finely ground manufactured sand tailings. 2-4 35.8 42.1 The original concrete mix proportion includes 15% finely ground manufactured sand tailings. 2-5 40.6 49.1 Improved concrete mix proportions 2-6 39.5 48.4 Improved concrete mix proportion by adding 5% finely ground manufactured sand tailings 2-7 41.9 50.9 Improved concrete mix proportions include 10% finely ground manufactured sand tailings. 2-8 38.1 46.2 Improved concrete mix proportions include 15% finely ground manufactured sand tailings.

[0096] As can be seen from the data in Table 5, when the dosage of finely ground manufactured sand tailings increased from 5% to 10%, the strength of concrete prepared using both the original and improved concrete mix proportions increased. Furthermore, for the original concrete mix proportion, the strength of the concrete decreased when the dosage of finely ground manufactured sand tailings increased from 10% to 15%. This indicates that the optimal dosage of finely ground manufactured sand tailings can improve concrete strength. In this embodiment, 10% is the optimal dosage of finely ground manufactured sand tailings; excessive dosage will lead to a decrease in concrete strength. Therefore, the determined concrete mix proportion is: cement 265 kg, finely ground manufactured sand tailings 29 kg, manufactured sand 883 kg, small aggregate 352 kg, medium aggregate 398 kg, large aggregate 321 kg, water 153 kg, and water-reducing agent 5.25 kg. This invention fully considers the filling effect of finely ground manufactured sand tailings in the concrete cementitious system, which is different from traditional methods. At the same time, without reducing the original mix strength, this method considers the improvement of the compaction of cementitious material by the addition of finely ground manufactured sand tailings to better match the filling effect of finely ground manufactured sand tailings in the concrete cementitious system, and appropriately adjusts the proportion of cement and sand, which can effectively improve the compaction of concrete particles, thereby reducing the amount of cementitious material used and saving costs.

[0097] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, conventional technical manuals in the field can be consulted. At the same time, appropriate understandings or adjustments can be made to the above-mentioned terms to deduce the same or similar technical solutions without creative effort.

[0098] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and the description of the invention content in the specification are only the principles or specific cases of the present invention. There are various changes and improvements to the innovative solutions of the present invention, and all such changes and improvements fall within the scope of protection claimed by the present invention.

Claims

1. A method for designing the dosage of mechanically produced sand tailings fine powder in concrete, characterized by, Includes the following steps: Step S1: Determine the density of the cement and manufactured sand tailings fine powder, determine the initial ratio of cement and manufactured sand tailings fine powder in the concrete formula according to the designed concrete strength, weigh the cement and manufactured sand tailings fine powder according to the initial ratio, add water to mix with the cement and manufactured sand tailings fine powder to obtain the mixture, wherein the added water makes the cement and manufactured sand powder fluid. Step S2: Fill a standard test container that can measure volume with the mixture, and weigh the standard test container after it is filled. Step S3: Calculate the bulk density of the mixture according to the bulk density formula; the bulk density formula is as follows: wherein Φ is the bulk density; M1 is the mass of the standard test container; M2 is the mass of the standard test container after filling with the mixture; is the volume of the standard test container; p c is the density of the cement; p s is the density of the machine-made sand tailings ground powder; p w is the density of water; u w is the water-binder volume ratio of the standard test container; Rc is the volume ratio of cement to binder; Rs is the volume ratio of machine-made sand tailings ground powder to binder; Step S4: Gradually reduce the amount of water added in step S1, and repeat steps S1 to S3 to obtain the packing density of the mixture with different water-cement volume ratios under the initial ratio of cement and machine sand tailings fine powder. The maximum packing density is taken as the densest packing density of the initial ratio of cement and machine sand tailings fine powder. Step S5: Change the ratio of cement to finely ground manufactured sand tailings and repeat steps S1 to S4 to obtain the maximum compaction density under different ratios of cement to finely ground manufactured sand tailings. Use the ratio of cement to finely ground manufactured sand tailings corresponding to the maximum value of the maximum compaction density to determine the amount of finely ground manufactured sand tailings in the concrete mix proportion.

2. The method for designing the dosage of the finely ground powder of the mechanically produced sand tailings in concrete according to claim 1, characterized in that, In step S1, when water, cement, and manufactured sand tailings are mixed, a paste mixing device is used to stir the water, cement, and manufactured sand tailings.

3. The method for designing the dosage of finely ground manufactured sand tailings in concrete according to claim 1, characterized in that, In step S3, the standard test container is vibrated during filling to remove air bubbles, and excess paste is scraped off.

4. A method for designing concrete mix proportions, characterized in that, Includes the following steps: Step 1: Conduct particle size distribution tests on cement, coarse aggregate, and fine aggregate in the concrete mix design, respectively. The fine aggregate includes manufactured sand. Step two: Based on the particle size distribution of cement, coarse aggregate, and fine aggregate, the theoretical cumulative passing rate for different particle sizes is calculated using a packing formula. Cement, coarse aggregate, and fine aggregate are mixed in a specific ratio to obtain mixed granular material. The actual cumulative passing rate for different particle sizes of the mixed granular material is then obtained based on the particle size distribution and ratio of cement, coarse aggregate, and fine aggregate. The expression for the packing formula is as follows: in This represents the theoretical cumulative throughput for particles smaller than D; D L Maximum particle size; D S is the minimum particle size; q is the particle size distribution index, and q is determined according to different strength grades of concrete, with a value ranging from 0.27 to 0.

35. Step 3: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput for different particle sizes of the mixed granules; Step 4: Adjust the mixing ratio of cement, fine aggregate, and coarse aggregate. Repeat steps 2 and 3 to obtain the sum of squares of the differences in the mixed aggregates under different mixing ratios. When the sum of squares of the differences is the smallest, the mixing ratio of cement, fine aggregate, and coarse aggregate is the mix ratio of cement, fine aggregate, and coarse aggregate in the concrete mix proportion. Step 5: Obtain the amount of finely ground manufactured sand tailings in the concrete mix proportion using the design method for the amount of finely ground manufactured sand tailings in concrete as described in any one of claims 1-3.

5. The method for designing concrete mix proportions according to claim 4, characterized in that, In step one, the particle size distribution of cement particles is determined by a laser particle size analyzer, and the particle size distribution of coarse and fine aggregates is determined by sieving.

6. The method for designing concrete mix proportions according to claim 5, characterized in that, When the designed concrete strength is C30, q is taken as 0.32; when the designed concrete strength is C40, q is taken as 0.3; and when the designed concrete strength is C50, q is taken as 0.

28.

7. The method for designing concrete mix proportions according to claim 5, characterized in that, In step five, before obtaining the dosage of finely ground manufactured sand tailings in the concrete mix proportion, when there are at least two types of finely ground manufactured sand tailings with different particle size distributions, it is also necessary to determine the optimal particle size distribution of the finely ground manufactured sand tailings in the concrete mix proportion. The method for determining the optimal particle size distribution of finely ground manufactured sand tailings includes the following steps: Step 51: Perform particle size distribution tests on the finely ground sand tailings with different particle size distributions used in the concrete mix proportions. Step 52: Mix the finely ground manufactured sand tailings with the cement, fine aggregate and coarse aggregate proportions in the concrete mix proportion determined in Step 4, and calculate the actual cumulative pass rate after mixing. Step 53: Calculate the sum of squares of the differences between the actual cumulative throughput and the theoretical cumulative throughput after adding finely ground sand tailings with different particle size distributions; Step 54: Determine the optimal particle size distribution of the finely ground powder of the manufactured sand tailings by using the particle size distribution corresponding to the minimum sum of squares of the differences between the manufactured sand tailings, cement, fine aggregate and coarse aggregate mixture.

8. The method for designing concrete mix proportions according to claim 7, characterized in that, The particle size distribution of the finely ground manufactured sand tailings was determined by a laser particle size analyzer.

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