Preparation method of machine-made sand modifier and machine-made sand modification method based on modifier
By preparing the microsphere structure of the machine-made sand modifier and utilizing its coating layer and decomposition effect, the concrete performance problem caused by stone powder in the machine-made sand was solved, and the mixture performance and mechanical properties of the concrete were improved.
Patent Information
- Application Number
- CN202510640275.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-10-14
AI Technical Summary
The high stone powder content in machine-made sand leads to increased concrete viscosity, decreased workability, low surface strength, high degree of carbonization and poor appearance quality. The existing flocculant cleaning method affects the performance of concrete.
The manufactured sand modifier is prepared by reacting a mixed solution of soluble iron salts, soluble calcium salts, sodium phosphate cellulose, sodium bicarbonate and polyacrylamide decomposing bacteria with sodium alginate to form a coating microsphere structure, which adsorbs and decomposes polyacrylamide in the manufactured sand and improves the performance of concrete.
It improves the mixing performance and mechanical properties of concrete, reduces the adverse effects of stone powder on concrete, and improves the volume stability and strength of concrete.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of building materials, in particular to a preparation method of a machine-made sand modifier and a machine-made sand modification method based on the modifier. BACKGROUND
[0002] Due to the characteristics in the mechanical crushing process, the machine-made sand usually contains a high amount of stone powder, which leads to the problems of increased viscosity of concrete and decreased workability. The concrete prepared using the machine-made sand with high stone powder content may also exhibit low surface strength, high carbonation degree and poor appearance quality in practical application. These problems are mainly caused by the large fluidity requirement or the change in fluidity caused by on-site water addition, and the lighter stone powder will float on the surface of the concrete during the vibrating process, resulting in insufficient compactness of the structural surface and further affecting the appearance and strength. Therefore, it is particularly important to control the stone powder content in the machine-made sand.
[0003] At present, the method for reducing the stone powder in the machine-made sand mainly uses anionic polyacrylamide for cleaning, but in order to ensure the cleaning effect, an excessive amount of flocculating agent is often added, and these residual chemicals will have an adverse effect on the subsequent concrete performance. With the increase of the residual amount of flocculating agent, the viscosity of the concrete is enhanced, the fluidity is reduced, and the slump loss is accelerated, which significantly increases the dosage of water reducing agent, brings challenges to industrial production, and increases the risk of segregation and bleeding. Therefore, it is crucial to inhibit the adverse effect of the flocculating agent on the concrete. SUMMARY
[0004] Based on the problems existing in the above background technology, the present application provides a preparation method of a machine-made sand modifier and a machine-made sand modification method based on the modifier, which can effectively alleviate the adverse effect of the flocculating agent in the machine-made sand on the performance of the concrete, improve the performance of the concrete mixture, and enhance the mechanical properties of the concrete.
[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:
[0006] A preparation method of a machine-made sand modifier, comprising the following steps:
[0007] (1) mixing a soluble iron salt and a soluble calcium salt and then adding them into water to form a mixed solution A;
[0008] The mass ratio of the soluble iron salt to the soluble calcium salt is 1:4-6;
[0009] (2) dissolving a sodium phosphate cellulose, a sodium bicarbonate and a polyacrylamide decomposition bacterial group in water to form a mixed solution B;
[0010] (3) weigh the sodium alginate solution and place it in a container, set a funnel above the container, slowly drop the mixed solution A obtained in step (1) and the mixed solution B obtained in step (2) into the funnel at the same time, mix them, and then drop them into the sodium alginate solution to obtain a mixed solution C;
[0011] (4) after ultrasonic oscillation of the mixed solution C obtained in step (3), filter the solution, dry the obtained particulate matter to obtain particulate matter with a microsphere structure, which is the manufactured sand modifier of the present application;
[0012] Further, the mass fraction of the soluble iron salt and the soluble calcium salt in the mixed solution A in step (1) is 0.5-1 part, and the mass fraction of water is 50 parts.
[0013] The mass fraction of each raw material component in step (2) is as follows:
[0014]
[0015] The mass concentration of the sodium alginate solution in step (3) is 0.5-1%, and the mass fraction of the solution is 100 parts, which is consistent with the mass fraction in step (1) and step (2).
[0016] Further, the soluble iron salt in step (1) is one or a mixture of two of ferric chloride and ferric nitrate; and the soluble calcium salt is one or a mixture of two of calcium chloride and calcium nitrate.
[0017] Further, the sodium phosphate cellulose in step (2) is a colorless and transparent powder-like substance prepared by reaction of microcrystalline cellulose and sodium phosphate; and the specific preparation method is as follows: the microcrystalline cellulose is dispersed in a NaOH solution, ultrasonic treatment is performed at a temperature of (60±10)℃ to swell the microcrystalline cellulose, then deionized water is used to wash to a neutral pH of 7, STPP is added, sodium hydroxide solution is added dropwise to adjust the pH to 11.5, a homogeneous suspension is formed, then it is transferred to a reaction kettle, constant temperature stirring is performed at (80±5)℃ for 4 hours, then it is cooled to room temperature, dilute hydrochloric acid is used to adjust the pH to 6.5, and then it is washed with deionized water and dried to obtain;
[0018] The mass fraction of the microcrystalline cellulose is 10 parts.
[0019] The mass fraction of the NaOH solution is 200 parts, and the mass concentration of the NaOH solution is 5%.
[0020] The mass fraction of the STPP is 15 parts.
[0021] Further, the polyacrylamide decomposition bacterial group in step (2) is selected from any one or more than one mixture of Bacillus licheniformis, Bacillus amyloliquefaciens and Bacillus subtilis.
[0022] Further, the mixing solution A and the mixing solution B in step (3) are both added at a constant speed, and the adding process is ensured to be in a drop shape to avoid forming a line.
[0023] Further, the funnel pipe length in step (3) is 1-3 cm, and a length that is too long causes the reaction to occur in the pipe to form a viscous substance, thereby affecting the adding and continuous reaction.
[0024] Further, the ultrasonic oscillation frequency in step (4) is 20-50 KHZ, and the continuous ultrasonic reaction time is 2-3 h; the granular substance is dried at a temperature of 40 DEG C or below, so as to avoid affecting the survival rate of the bacterial population and avoid the decomposition of sodium bicarbonate to release carbon dioxide too early.
[0025] In the present application, after sodium phosphate cellulose solution is added with sodium bicarbonate and polyacrylamide to form a mixed solution, and then mixed with a soluble iron salt and a soluble calcium salt, the calcium ions and the iron ions replace the sodium ions in the sodium phosphate cellulose, thereby forming a calcium phosphate iron cellulose precipitate. In order to avoid the blockage of the pipe by the precipitate formed after mixing, the mixing solution A and the mixing solution B are required to be mixed for a short time before being added into the sodium alginate. Once added into the sodium alginate solution, the sodium ions in the sodium alginate replace the calcium ions in the mixed solution A and B, thereby forming a calcium alginate coating layer on the surface of the liquid droplets, so that the overall structure of the liquid droplets is a spherical liquid droplet wrapped with the calcium alginate coating layer. Inside the coating layer, the replacement of the sodium ions in the sodium phosphate cellulose with the iron and calcium ions continues to occur, and is gradually constrained by the calcium alginate coating layer, thereby gradually forming a microsphere structure. Further ultrasonic oscillation of the microspheres can stimulate the development of the fiber structure from a linear shape to a network shape, so that the overall microsphere structure is more complete, and the adhesion between the precipitate crystals is stronger. Finally, the microsphere structure containing the bacterial population is obtained, which uses the fiber in the phosphate as a network adhesive, uses the phosphate as a skeleton, and uses the sodium bicarbonate as a filler.
[0026] Further, the present application also provides a method for modifying machine-made sand based on the above-mentioned modifier, which comprises:
[0027] The above-mentioned machine-made sand modifier microspheres are first sprayed with a sodium citrate solution to wet the surface, and then placed for a period of time, and then added into the machine-made sand, and the aggregate is pre-wetted with water, stirred and placed to obtain modified machine-made sand for standby use;
[0028] The mass concentration of the sodium citrate solution is 3-5%;
[0029] The surface wetting and placing time is 20-30 min.
[0030] The stirring time is 8-10 min, and the standing time after stirring is 6-8 h.
[0031] Further, the microsphere content is 0.5-1% of the mass of the manufactured sand, and the water content is 5-10% of the mass of the manufactured sand.
[0032] In the preparation reaction of the modifier, a polyacrylamide decomposition bacterial group is incorporated. When the modifier microspheres are used, they are wetted with sodium citrate, which promotes the dissolution of the surface calcium alginate, thereby releasing the bacterial group. Further, the microsphere structure is mixed and stirred with the manufactured sand, so that the iron and calcium ions in the microspheres can quickly adsorb and enrich the polyacrylamide in the manufactured sand, and the polyacrylamide decomposition bacterial group further decomposes the polyacrylamide in the manufactured sand, reducing the adverse effects of polyacrylamide on concrete. The decomposition product acrylamide has high synergy with polycarboxylate superplasticizer, which is beneficial to the improvement of the performance of the concrete mixture and the improvement of the mechanical properties.
[0033] Further, the microsphere structure modifier can significantly improve the performance of the concrete mixture, and the phosphate cellulose formed by the modifier has extremely strong water absorption, can absorb a large amount of water, and plays an internal curing role, which is beneficial to the improvement of the strength and volume stability of the concrete.
[0034] In the hydration process of the concrete, as the hydration process intensifies, the internal temperature of the concrete gradually rises. Under this condition, the internal sodium bicarbonate gradually decomposes to form calcium carbonate crystalline precipitate to block the pores of the microspheres, and the carbon dioxide generated by the decomposition reacts with the calcium hydroxide formed in the hydration process to also generate calcium carbonate crystals, achieving further filling and reinforcement of the pores and gaps, which is beneficial to the improvement of the strength and volume stability of the concrete.
[0035] Compared with the prior art, the present application has the following beneficial effects:
[0036] The present application solves the problem of increased viscosity and decreased slump retention of the concrete mixture caused by the manufactured sand by using a microsphere for modifying manufactured sand, and the synergistic effect of the microsphere morphology and its attachments, and improves the mechanical properties and volume stability of the concrete. DETAILED DESCRIPTION
[0037] The present application will be further described below in conjunction with various embodiments.
[0038] Example 1
[0039] A specific preparation method of a manufactured sand modifier includes the following steps:
[0040] (1) The soluble iron salt and the soluble calcium salt are mixed in a mass ratio of 1:4, 1 part of which is added to 50 parts of water to form a mixed solution A;
[0041] (2) 3 parts of sodium phosphate cellulose, 2 parts of sodium bicarbonate, and 0.01 parts of a polyacrylamide decomposing bacterial group are dissolved in 50 parts of water to form a mixed solution B;
[0042] (3) More than 100 parts of a 1% sodium alginate solution are placed in a container, a funnel is set up above the container, and the solution A and the solution B are slowly added to the funnel for mixing, and then are added to the sodium alginate solution, the length of the funnel pipeline is 1 cm; after mixing, the solution A and the solution B are added dropwise at the same speed, and the dropwise addition process is in the form of drops to avoid linear addition;
[0043] (4) After the mixed solution is added to the sodium alginate solution, the sodium alginate solution is ultrasonically oscillated at 20 kHz, the reaction is continued for 3 h, the solution is filtered, and the particulate matter is dried at a temperature of 25°C to obtain microspheres, which are the modified agent for machine-made sand.
[0044] A machine-made sand modification method based on the above-mentioned modified agent, comprising:
[0045] The microspheres are first sprayed with a 3% sodium citrate solution to wet them, and then are placed for 30 min, and after wetting, are added to the machine-made sand, 10% of the mass of the machine-made sand is added as water pre-wetted aggregate, and after stirring for 8 min, the mixture is placed for 8 h for standby;
[0046] The microsphere content is 0.8% of the machine-made sand content;
[0047] The soluble iron salt is ferric chloride;
[0048] The soluble calcium salt is calcium chloride;
[0049] The polyacrylamide decomposing bacterial group is Bacillus licheniformis;
[0050] The dropping speed of the solution A and the solution B is 50 g / min.
[0051] The ultrasonic oscillation frequency is 50 Hz.
[0052] Example 2
[0053] A specific preparation method of a machine-made sand modification agent comprises the following steps:
[0054] (1) The soluble iron salt and the soluble calcium salt are mixed in a mass ratio of 1:6, 0.5 parts of which are added to 50 parts of water to form a mixed solution A;
[0055] (2) Take 5 parts of sodium phosphate cellulose, 1 part of sodium bicarbonate, and 0.03 parts of polyacrylamide decomposition bacteria group, dissolve in 50 parts of water to form a mixed solution B;
[0056] (3) Take 100 parts of sodium alginate solution with a concentration of 0.5% above, place it in a container, set up a funnel above the container, slowly drop mixed solution A and solution B into the funnel, then drop into the sodium alginate solution, the length of the funnel pipe is 3 cm; After mixing, drop into the sodium alginate solution at the same speed of solution A and solution B, ensure that the mixed solution drops into the sodium alginate solution in the form of drops to avoid affecting the shape of the microspheres in the sodium alginate solution during the dropping process;
[0057] (4) After the mixed solution is dropped into the sodium alginate solution, ultrasonic oscillation is performed on the sodium alginate solution at a frequency of 50 kHz, and the reaction is continued for 2 hours. Then, the solution is filtered, and the particulate matter is dried at a temperature of 40°C to obtain microspheres, which are the modified agent for manufactured sand.
[0058] A method for modifying manufactured sand based on the above-mentioned modified agent, comprising:
[0059] First, the microspheres are sprayed with a 5% sodium citrate solution for 20 minutes, then added to the manufactured sand, and 5% water is added to the pre-wetted aggregate, stirred for 10 minutes, and then placed for 6 hours for standby;
[0060] The microsphere content is 0.8% of the manufactured sand content;
[0061] The soluble iron salt is ferric nitrate;
[0062] The soluble calcium salt is calcium nitrate;
[0063] The polyacrylamide decomposition bacteria group is a mixture of Bacillus licheniformis, Bacillus amyloliquefaciens, and Bacillus subtilis in a mass ratio of 1:1:1;
[0064] The dropping speed of solution A and solution B is 80 g / min;
[0065] The ultrasonic oscillation frequency is 20 HZ.
[0066] Example 3
[0067] A specific preparation method of a modified agent for manufactured sand includes the following steps:
[0068] (1) Mix the soluble iron salt and the soluble calcium salt in a mass ratio of 1:5, then take 0.8 parts and add to 50 parts of water to form a mixed solution A;
[0069] (2) Take 4 parts of sodium phosphate cellulose, 1.5 parts of sodium bicarbonate, and 0.02 parts of polyacrylamide decomposition bacteria group, dissolve in 50 parts of water to form a mixed solution B;
[0070] (3) Take 100 parts of a sodium alginate solution with a concentration of 0.8% and place it in a container. Set up a funnel above the container, and slowly drop solution A and solution B into the funnel at the same time. After mixing, drop them into the sodium alginate solution. The length of the funnel pipe should be 2 cm. After mixing, drop the solution into the sodium alginate solution. Solution A and solution B should be dropped at the same speed. During the dropping process, ensure that the mixture is dropped in a drop shape to avoid forming a line.
[0071] (4) After the mixed solution is dropped into the sodium alginate solution, ultrasonically shake the sodium alginate solution at 30 kHz for 2.5 hours. Then filter the solution and dry the particulate matter at a temperature of 30°C to obtain microspheres, which are the manufactured sand modifier.
[0072] A method for modifying manufactured sand based on the above-mentioned modifier, comprising:
[0073] First, spray the microspheres with a 4% sodium citrate solution for 28 minutes to wet them. After wetting, add the manufactured sand to the mixture, and add 8% water to the pre-wetted aggregate. Stir for 9 minutes, then let it stand for 7 hours before use.
[0074] The microsphere content is 0.8% of the manufactured sand content.
[0075] The soluble iron salt is a mixture of ferric chloride and ferric nitrate in a mass ratio of 1:1.
[0076] The soluble calcium salt is a mixture of calcium chloride and calcium nitrate in a mass ratio of 1:1.
[0077] The polyacrylamide-degrading bacterial population is Bacillus subtilis.
[0078] The dropping speed of solution A and solution B is 60 g / min.
[0079] The ultrasonic shaking frequency is 25 HZ.
[0080] Comparative Example 1
[0081] Compared with Example 3, no soluble iron salt is added in step (1) of the method for preparing the manufactured sand modifier, only calcium salt is added.
[0082] Comparative Example 2
[0083] Compared with Example 3, no soluble calcium salt is added in step (1) of the method for preparing the manufactured sand modifier, only iron salt is added.
[0084] Comparative Example 3
[0085] Compared with Example 3, the ratio of iron salt to calcium salt in step (1) of the method for preparing the manufactured sand modifier is 1:10.
[0086] Comparative Example 4
[0087] Compared with Example 3, no sodium phosphate cellulose is used in step (2) of the manufactured sand modifier preparation method.
[0088] Comparative Example 5
[0089] Compared with Example 3, no sodium phosphate cellulose is used in step (2) of the manufactured sand modifier preparation method, and an equal amount of sodium phosphate and cellulose is used instead.
[0090] Comparative Example 6
[0091] Compared with Example 3, no sodium bicarbonate is used in step (2) of the manufactured sand modifier preparation method.
[0092] Comparative Example 7
[0093] Compared with Example 3, no ultrasonic oscillation is performed in step (4) of the manufactured sand modifier preparation method.
[0094] Comparative Example 8
[0095] Compared with Example 3, the drying temperature in step (4) of the manufactured sand modifier preparation method is 60°C.
[0096] Comparative Example 9
[0097] Compared with Example 3, the modifier is directly used after being wetted with water in the manufactured sand modification method.
[0098] Comparative Example 10
[0099] Compared with Example 3, no decomposition bacterial population is added in step (2) of the manufactured sand modifier preparation method.
[0100] Comparative Example 11
[0101] Compared with Example 3, the manufactured sand modifier microspheres are directly incorporated into the concrete for use, and no specific modification method steps are performed.
[0102] The reference concrete mix proportion is: P.O42.5 cement 380 kg / m 3 , manufactured sand dosage 780 kg / m 3 , sand dosage 1080 kg / m 3 , water 155 kg / m 3 , and the polycarboxylic acid water reducing agent dosage is the manufacturer's recommended dosage (1% of the cement dosage).
[0103] On the basis of the above concrete mix proportion, 0.8% of the microspheres by mass of the manufactured sand are incorporated.
[0104] The concrete performance is shown in Table 1:
[0105] Table 1 Concrete performance of manufactured sand modified by each example and comparative example
[0106]
[0107] Compared with Example 3, the performance of the mixture of Comparative Example 1 is reduced more. Because of the lack of calcium salt, the total sodium salt of sodium cellulose phosphate cannot be replaced to form calcium phosphate crystalline precipitate, resulting in the lack of sufficient support points in the network fiber structure formed, the poor strength of the microsphere structure formed, and the poor form effect of the concrete mixed into the concrete, so that the performance of the concrete mixture is not improved enough.
[0108] Compared with Example 3, the performance of the mixture of Comparative Example 2 is reduced more. Because of the lack of iron salt, the adsorption of polyacrylamide in machine-made sand is reduced, and the adverse effects of polyacrylamide cannot be completely eliminated, so that the performance of the concrete mixture is not improved enough.
[0109] The main problem of Comparative Example 3 is that the microsphere formation efficiency is low. Because the calcium salt is too much, the replacement speed with sodium ions in sodium cellulose phosphate is too fast, which will cause the rapid reaction of A and B after mixing to adhere to the funnel wall, and cannot be quickly dropped into the sodium alginate solution to form microspheres with low efficiency. Moreover, the microsphere structure is irregular, and the improvement effect on the performance of the concrete mixture is limited.
[0110] Compared with Example 3, the slump of the concrete of Comparative Example 4 decreases obviously, the slump loss increases, the emptying time of the inverted slump cone extends, and the strength decreases. This is because sodium cellulose phosphate mainly provides network structure support for the formation of microspheres, and the lack of sodium cellulose phosphate makes the microsphere structure unable to form, and the effect is not obvious. Only rely on the decomposition and absorption of bacteria to polyacrylamide, the efficiency is low, and the improvement effect is limited.
[0111] Compared with Example 3, the slump of the concrete of Comparative Example 5 decreases obviously, the slump loss increases, the emptying time of the inverted slump cone extends, the strength decreases, and the shrinkage rate increases. This is because the separate use of sodium phosphate and cellulose lacks the network structure support of cellulose, the microspheres formed lack pores and water absorption, and the microsphere structure is incomplete. In this way, the form effect of the microspheres is lacking, and the internal curing effect after porous water absorption is lacking, so that the performance of the mixture and the strength decrease. Cellulose increases the viscosity, which is not conducive to the improvement of the performance of the concrete mixture.
[0112] Compared with Example 3, the mechanical properties and volume stability of the concrete of Comparative Example 6 decrease obviously. This is because sodium bicarbonate mainly acts to provide carbon dioxide, react with calcium hydroxide to form crystalline blockage holes, improve the density, and thus be beneficial to the improvement of the strength and the volume stability. The lack of use limits the improvement of the mechanical properties and the volume stability.
[0113] Compared with Example 3, the slump of the concrete of Comparative Example 7 decreased obviously, the slump loss increased, the emptying time of the inverted slump cone prolonged, the strength decreased, and the shrinkage increased. The purpose of ultrasonic oscillation is to promote the formation of the cellulose network structure. Without the ultrasonic oscillation, the fiber network structure is not formed well, and the microsphere structure is poor. Thus, the microsphere lacks the morphological effect and the internal curing effect after water absorption, so the performance and strength of the mixture decrease.
[0114] Compared with Example 3, the slump, the slump loss, the emptying time of the inverted slump cone, the compressive strength, and the shrinkage of the concrete of Comparative Example 8 improved only a little. This is mainly because the high temperature causes the bacteria to be inactivated to some extent, and causes sodium bicarbonate to decompose to produce carbon dioxide too early, so that the internal reinforcement effect in the later stage is lost.
[0115] Compared with Example 3, the slump, the slump loss, and the emptying time of the inverted slump cone of the concrete of Comparative Example 9 improved only a little. This is because the polyacrylamide in the machine-made sand lacks the time for being absorbed by calcium ions and decomposed by bacteria after being wetted and directly used, so that the adverse effect of the polyacrylamide still exists, and the performance of the concrete mixture decreases.
[0116] Compared with Example 3, the slump, the slump loss, the emptying time of the inverted slump cone, the compressive strength, and the shrinkage of the concrete of Comparative Example 10 improved only a little. This is mainly because the decomposition bacteria are not mixed, so that the polyacrylamide cannot be decomposed and accommodated, and the adverse effect of the polyacrylamide on the performance of the concrete mixture cannot be eliminated.
[0117] Compared with Example 3, the slump, the slump loss, the emptying time of the inverted slump cone, the compressive strength, and the shrinkage of the concrete of Comparative Example 11 improved only a little. This is mainly because the microspheres are directly mixed, so that the decomposition of the bacteria, the adsorption of the microspheres, and the internal curing effect of the microspheres cannot be realized, and the microspheres are directly used without being wetted, so that water is absorbed. Although the effect of the microspheres can improve the slump and reduce the slump loss of the concrete, the slump loss of the concrete increases obviously because of the water absorption of the microspheres in the concrete mixture.
Claims
1. A method for preparing a machine-made sand modifier, characterized in that: The steps include: (1) mixing a soluble iron salt and a soluble calcium salt and adding the mixture to water to form a mixed solution A; The mass ratio of the soluble iron salt to the soluble calcium salt is 1:4-6; (2) dissolving sodium cellulose phosphate, sodium bicarbonate, and polyacrylamide decomposing bacterial flora in water to form a mixed solution B; (3) Weighing a sodium alginate solution and placing it in a container, setting up a funnel above the container, slowly dropping the mixed solution A obtained in step (1) and the mixed solution B obtained in step (2) into the funnel at the same time, mixing them, and then dropping them into the sodium alginate solution to obtain a mixed solution C; (4) After ultrasonically vibrating the mixed solution C obtained in step (3), the solution is filtered and the obtained particles are dried to obtain particles with a microsphere structure, which is the machine-made sand modifier.
2. The method for preparing a machine-made sand modifier according to claim 1, wherein: The mixed solution A in step (1) contains 0.5 to 1 parts by weight of soluble iron salt and soluble calcium salt, and 50 parts by weight of water; The mass fractions of each raw material component in step (2) are as follows: The mass concentration of the sodium alginate solution in step (3) is 0.5-1%, and the mass fraction of the solution is 100 parts, which is consistent with that in step (1) and step (2).
3. The method for preparing a machine-made sand modifier according to claim 1, characterized in that: The soluble iron salt in step (1) is one or a mixture of ferric chloride and ferric nitrate; The soluble calcium salt is one of calcium chloride and calcium nitrate or a mixture of the two.
4. The method for preparing a machine-made sand modifier according to claim 1, wherein: The sodium phosphate cellulose in step (2) is a colorless, transparent powdery substance prepared by reacting microcrystalline cellulose and sodium phosphate.
5. The method for preparing a machine-made sand modifier according to claim 4, characterized in that: The specific preparation method of the sodium phosphate cellulose described in step (2) is as follows: dispersing microcrystalline cellulose in a NaOH solution, controlling the temperature at (60±10)°C, ultrasonically treating the microcrystalline cellulose to swell, washing with deionized water to a neutral pH of 7, adding STPP, and dropping sodium hydroxide solution to adjust the pH to 11.5 to form a homogeneous suspension, which is then transferred to a reactor, reacting at a constant temperature of (80±5)°C with stirring for 4 hours, cooling to room temperature, adjusting the pH to 6.5 with dilute hydrochloric acid, washing with deionized water, and drying to obtain the product; The mass fraction of the microcrystalline cellulose is 10 parts; The mass fraction of the NaOH solution is 200 parts, and the mass concentration of the NaOH solution is 5%; The mass fraction of the STPP is 15 parts.
6. The method for preparing a machine-made sand modifier according to claim 1, characterized in that: The polyacrylamide decomposing bacteria in step (2) is selected from any one of Bacillus licheniformis, Bacillus amyloliquefaciens and Bacillus subtilis or a mixture of more than one of them.
7. The method for preparing a machine-made sand modifier according to claim 1, characterized in that: In step (3), the mixed solution A and the mixed solution B are both added dropwise at a constant rate, and the dropping speed of the mixed solution A and the mixed solution B is 50 to 80 g / min; The length of the funnel pipe in step (3) is 1 to 3 cm.
8. The method for preparing a machine-made sand modifier according to claim 1, characterized in that: The ultrasonic oscillation frequency in step (4) is 20 to 50 kHz, and the continuous ultrasonic reaction time is 2 to 3 hours; The particles are dried at a temperature of 40° C. or below.
9. A method for modifying machine-made sand using the modifier obtained by the method according to any one of claims 1 to 8, characterized in that: include: First, spray the above-mentioned machine-made sand modifier microspheres with sodium citrate solution until the surface is moistened and then leave it for a period of time. Then, add it to the machine-made sand, add water to pre-wet the aggregate, stir and let it stand to obtain the modified machine-made sand for use. The mass concentration of the sodium citrate solution is 3-5%; The surface is left standing for 20 to 30 minutes after being wetted; The stirring time is 8 to 10 minutes, and the standing time after stirring is 6 to 8 hours.
10. The method according to claim 9, characterized in that: The amount of the machine-made sand modifier microspheres is 0.5% to 1% of the mass of the machine-made sand, and the amount of water added is 5% to 10% of the mass of the machine-made sand.