Preparation method of modified microspheres and washing machine-made sand performance optimization method based on microspheres
The use of modified polystyrene microspheres in treated manufactured sand addresses the viscosity and strength issues caused by anionic flocculants, enhancing concrete flowability and strength through cross-linking reactions.
Patent Information
- Application Number
- CN202510426291.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-07-15
AI Technical Summary
The adhesion of flocculant in water-washed sand causes the decline in concrete and the ease and strength, and the prior art is difficult to effectively optimize.
Modified porous polystyrene cationic microspheres, silane and calcium hydroxide are used to treat the washed machine sand. Through high-temperature drying and insulation treatment, silicone amide substances and cross-linking network structure are generated, and polyacrylamide is adsorbed and degraded to improve concrete fluidity and strength.
It significantly improves the slump loss and fluidity of concrete, improves the later strength of concrete, and solves the adverse impact of flocculants on concrete performance.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of building materials, and particularly to a preparation method of modified microspheres and a method for optimizing the performance of washed machine-made sand based on these microspheres. Background Art
[0002] In recent years, the rapid development of the construction industry has promoted the wide application of washed machine-made sand. This type of sand has become an effective way to solve the problem of the depletion of natural river sand resources due to its advantages such as clean appearance, less dust, and low cost, and has attracted much attention. With the booming development of the washed machine-made sand industry, the large amount of clean water required in its production process has also raised considerations for water resource conservation. For this reason, adding an appropriate amount of flocculant has become an important measure for water conservation, promoting the application and development of flocculants in this field. Flocculants attract difficult-to-separate particles with opposite charges in water through charged groups, reduce their potential stability, and use their polymerization properties to aggregate these particles, and then separate them by physical or chemical methods. However, during the cleaning process, the flocculant will adhere to the surface of the machine-made sand. When it is used in concrete production, if the content exceeds the standard, it will have a significant impact on the workability and strength of the concrete, bringing new challenges.
[0003] During the cleaning process of machine-made sand, anionic flocculants are mostly used. Through the adsorption of opposite charges, charged substances in the solution are aggregated to form precipitation nuclei and gradually accumulate into large particles. As the dosage of ionic flocculants in washed machine-made sand increases, the flocculent clusters gradually become long and flocculent under the influence of charge repulsion, resulting in an increase in the viscosity of the concrete, thus causing a decrease in the slump and slump retention performance of the concrete, and further leading to a decrease in the mechanical properties of the concrete. Therefore, it is necessary to conduct optimization research on machine-made sand based on the production process of washed machine-made sand and the adverse effects of flocculants on concrete. Summary of the Invention
[0004] In view of the problems in the background art, the present invention proposes a preparation method of modified microspheres and a method for optimizing the performance of washed machine-made sand based on these microspheres.
[0005] To achieve the above invention purposes, the present invention provides the following technical solutions:
[0006] A preparation method of modified microspheres, comprising: soaking porous polystyrene cation microspheres in an excessive amount of iron salt solution, and ultrasonically dispersing for more than 30 minutes. After being fully infiltrated, drain to obtain the modified microspheres;
[0007] The modified microspheres are modified porous polystyrene cation microspheres formed by treating the surface of porous polystyrene microspheres to attach a large number of cations;
[0008] The iron salt solution is a saturated iron salt solution, and its dosage is such that it can completely soak the porous polystyrene cation microspheres.
[0009] Furthermore, the particle size of the porous polystyrene cation microspheres in the present invention is 0.1 - 0.5 mm.
[0010] Furthermore, the iron salt in the present invention is selected from any one of iron nitrate, iron chloride, and iron sulfate.
[0011] Furthermore, the pore size of the modified porous polystyrene cation microspheres in the present invention is 20 - 50 nm, and the microsphere size is 0.1 - 0.5 mm.
[0012] Furthermore, the present invention also provides a method for optimizing the performance of washed manufactured sand based on the above-mentioned modified microspheres, including: adding silane, calcium hydroxide, and modified microspheres to the washed manufactured sand, drying at 90°C - 130°C until the moisture content is not higher than 1%, and maintaining the temperature for 6 - 8 h to obtain the manufactured sand with optimized performance;
[0013] The mass parts of each raw material component are as follows:
[0014]
[0015] Among them, the manufactured sand is the manufactured sand washed with water and polyacrylamide flocculant, and its dosage is the mass parts of the manufactured sand after removing water.
[0016] In the present invention, adding silane and calcium hydroxide to the washed manufactured sand can cause the polyacrylamide to undergo an imidization reaction at 90°C - 130°C. The polyacrylamide will have intramolecular and intermolecular crosslinking, and insoluble substances are generated during the crosslinking process, reducing the solubility of the polyacrylamide. Applying the manufactured sand to concrete can greatly alleviate the hydrolysis of polyacrylamide under dissolution conditions, thereby absorbing a large amount of free water and material particles, reducing the slump and slump loss of concrete over time, and reducing the adverse effects on the strength of concrete. At the same time, the polyacrylamide reacts with silane to form silicone amide substances, which have a surface-active effect, facilitating the surface modification of the manufactured sand particles and reducing the adverse effects of stone powder and flaky particles of the manufactured sand on the viscosity of the concrete mixture. All in all, through the incorporation of certain components of silane and calcium hydroxide, and utilizing the high-temperature modification and catalytic effect in the process of drying the washed manufactured sand, the adverse effects of polyacrylamide on the slump of concrete, especially the slump loss over time, are greatly improved, turning the harmful effects into beneficial effects, and instead enhancing the state and fluidity of the concrete mixture.
[0017] The modified porous polystyrene cationic microspheres are designed to improve the fluidity of cement paste due to their structure. Additionally, the porous polystyrene cationic microspheres can actively adsorb anionic polyacrylamide, causing the polyacrylamide to detach from the manufactured sand. Meanwhile, they adsorb a large amount of iron ions on their own, which can promote the degradation of the polyacrylamide molecular chains adsorbed on the surface of the microspheres by the porous polystyrene cationic microspheres, facilitating absorption into the interior of the microspheres. Further, in concrete, the structure of the porous polystyrene cationic microspheres can rely on the polyacrylamide structure to absorb a large amount of water, forming an internal curing structure, which effectively promotes the improvement of the late strength of concrete.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] (1) The manufactured sand improved by using the performance optimization method of the present invention can effectively solve the problem of increased viscosity caused by it, and at the same time can alleviate problems such as large slump loss and decreased mechanical properties of concrete caused by the flocculant polyacrylamide;
[0020] (2) The manufactured sand obtained by using the method of the present invention significantly improves the state and fluidity of the concrete mixture, and can effectively promote the improvement of the late strength of concrete. Specific Embodiments
[0021] The following details the embodiments of the present invention. Implementations are carried out on the premise of the technical solution of the present invention, providing detailed implementation methods and operation processes, but the protection scope of the present invention is not limited to the following embodiments.
[0022] Example 1
[0023] A method for optimizing the performance of washed manufactured sand, the specific steps are as follows:
[0024] Weigh 100 parts by mass of the washed manufactured sand (mass after removing water), add 0.02 parts of silane, 0.2 parts of calcium hydroxide, and 0.2 parts of modified porous polystyrene cationic microspheres, dry it at 120 °C until the moisture content is 1%, and keep it at this temperature for 8 h to obtain modified manufactured sand;
[0025] The washed manufactured sand is the manufactured sand washed with polyacrylamide as a flocculant;
[0026] The preparation method of the modified porous polystyrene cationic microspheres is as follows: soak the porous polystyrene cationic microspheres with a size of 0.1 - 0.5 mm in an excessive saturated iron nitrate solution, and ultrasonically disperse for 30 min. After sufficient infiltration, drain and set aside;
[0027] The pore size of the modified porous polystyrene cationic microspheres is 20 - 50 nm.
[0028] Example 2
[0029] A method for optimizing the performance of washed machine-made sand, the specific steps are as follows:
[0030] Weigh 100 parts by mass of the washed machine-made sand (the mass after removing water), add 0.04 part of silane, 0.1 part of calcium hydroxide, and 0.5 part of modified porous polystyrene cationic microspheres, dry it at 90 °C until the moisture content is 0.6%, and keep it warm at this temperature for 6 hours to obtain modified machine-made sand;
[0031] The washed machine-made sand is the machine-made sand washed with polyacrylamide as a flocculant;
[0032] The preparation method of the modified porous polystyrene cationic microspheres is to soak the porous polystyrene cationic microspheres with a size of 0.1 - 0.5 mm in an excessive saturated iron chloride solution, and ultrasonically disperse for 35 minutes. After sufficient infiltration, drain and set aside;
[0033] The pore size of the modified porous polystyrene cationic microspheres is 20 - 50 nm.
[0034] Example 3
[0035] A method for optimizing the performance of washed machine-made sand, the specific steps are as follows:
[0036] Weigh 100 parts by mass of the washed machine-made sand (the mass after removing water), add 0.03 part of silane, 0.15 part of calcium hydroxide, and 0.3 part of modified porous polystyrene cationic microspheres, dry it at 90 °C until the moisture content is 0, and keep it warm at this temperature for 7 hours to obtain modified machine-made sand;
[0037] The washed machine-made sand is the machine-made sand washed with polyacrylamide as a flocculant;
[0038] The preparation method of the modified porous polystyrene cationic microspheres is to soak the porous polystyrene cationic microspheres with a size of 0.1 - 0.5 mm in an excessive saturated iron sulfate solution, and ultrasonically disperse for 40 minutes. After sufficient infiltration, drain and set aside;
[0039] The pore size of the modified porous polystyrene cationic microspheres is 20 - 50 nm.
[0040] Comparative Example 1
[0041] Compared with Example 3, the difference is that silane is not incorporated.
[0042] Comparative Example 2
[0043] Compared with Example 3, the difference is that 0.1 part of silane is incorporated.
[0044] Comparative Example 3
[0045] Compared with Example 3, the difference is that calcium hydroxide is not incorporated.
[0046] Comparative Example 4
[0047] Compared with Example 3, the difference is that 0.5 part of calcium hydroxide is incorporated.
[0048] Comparative Example 5
[0049] Compared with Example 3, the difference is that the modified porous polystyrene cation microspheres are not incorporated.
[0050] Comparative Example 6
[0051] Compared with Example 3, the difference is that porous polystyrene cation microspheres are incorporated without modification.
[0052] Comparative Example 7
[0053] Compared with Example 3, the difference is that the pore size of the incorporated modified porous polystyrene cation microspheres is 5 - 20 nm.
[0054] Comparative Example 8
[0055] Compared with Example 3, the difference is that the pore size of the incorporated modified porous polystyrene cation microspheres is 60 - 100 nm.
[0056] Comparative Example 9
[0057] Compared with Example 3, the difference is that drying is carried out at 60 °C.
[0058] Comparative Example 10
[0059] Compared with Example 3, the difference is that drying is carried out until the water content is 3%.
[0060] Comparative Example 11
[0061] Compared with Example 3, the difference is that the manufactured sand is only dried without modification.
[0062] Comparative Example 12
[0063] Compared with Example 3, the difference is that the manufactured sand is incorporated with porous polystyrene cation microspheres without modification.
[0064] The concrete mix proportion design is carried out according to the provisions of JGJ 55. The specific mix proportion is that the amount of ordinary Portland cement is 360 kg / m 3 , and the amount of the manufactured sand with improved performance in each example and comparative example is 780 kg / m 3 , the amount of crushed stone is 1050 kg / m 3 , and the water consumption is 165 kg / m 3, the dosage of polycarboxylate superplasticizer is 2% of the manufacturer's recommended dosage. During the calculation, the water content in the polycarboxylate superplasticizer and sand is calculated into the water consumption, and the concrete properties are shown in Table 1.
[0065] Table 1 Concrete Properties
[0066]
[0067]
[0068] Comparing Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 11, the slump, slump retention performance and compressive strength of the concrete are significantly deteriorated. This is mainly because the main purpose of silane is to react with the amide group during the imidization reaction with polyacrylamide at high temperature to generate silicone amide substances, thereby promoting the imidization reaction and the formation of insoluble substances such as silicone amide, so as to eliminate the flocculation effect generated by polyacrylamide during the cement hydration process. When silane is not added or the silane dosage is too low, the imidized polyacrylamide at high temperature is prone to further decomposition in the alkaline solution, thus having flocculation and water absorption effects, resulting in a rapid decrease in the slump of the concrete and an increase in the slump loss over time. And the lack of silicone amide generated by the reaction of silane with the amide group. As a hydrophobic surfactant, silicone amide can disperse cement particles, effectively increase the fluidity of the concrete, and reduce the adverse effect of the stone powder content on the fluidity of the concrete. The reason for using silane instead of other silane materials is that silane is soluble in water and can react with polyacrylamide relatively quickly in the manufactured sand, while other silane materials cannot produce the effect.
[0069] Comparing Example 3 with Comparative Example 3, Comparative Example 4 and Comparative Example 11, it can be seen that not adding calcium hydroxide will cause a decrease in the slump, slump retention performance and compressive strength of the concrete, and adding excessive calcium hydroxide will cause a decrease in the concrete strength. The purpose of calcium hydroxide is to provide an alkaline solution environment and calcium ions, facilitating the hydrolysis of polyacrylamide and its enrichment under calcium salt conditions, so as to facilitate its further amidation, imidization and reaction with silane. Without the catalytic action of the alkaline solution, under the influence of low concentration and a large amount of manufactured sand, the imidization reaction of polyacrylamide and the formation of silicone amide will be affected to a certain extent. Therefore, when calcium hydroxide is not added, the slump decreases to a certain extent, the slump loss over 1h increases to a certain extent, and the compressive strength increases. When excessive calcium hydroxide is added, the slump decreases, the slump loss over time decreases to a certain extent, and the concrete strength decreases. This is because although the addition of calcium hydroxide is beneficial to the decomposition of polyacrylamide, in the process of optimizing the manufactured sand, modified porous polystyrene cation microspheres are added. The modified porous polystyrene cation microspheres contain iron ions, which form a gel with hydroxide ions, causing the decomposition effect of iron ions on polyacrylamide to fail. Therefore, the dosage of calcium hydroxide should not be too much.
[0070] Comparing Comparative Example 3 with Comparative Example 5 and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete all deteriorate significantly. The purpose of the modified porous polystyrene cationic microspheres is to complex and adsorb amide group molecules, and at the same time decompose the enriched polyacrylamide into smaller molecular structures by using the iron ions filled inside, and further absorb it into the pores of the microspheres to form a cross-linked network structure with the iron ions. On the one hand, it can improve the water absorption and water retention of the porous polystyrene cationic microspheres and enhance their internal curing effect in the concrete. On the other hand, by using their microsphere morphology, it can improve the lubricity between the concrete material particles and increase the fluidity of the concrete mixture. Therefore, without adding the modified porous polystyrene cationic microspheres, the polyacrylamide in the concrete will still cause flocculation, reduce the slump of the concrete, increase the slump loss of the concrete over time, and reduce the strength of the concrete.
[0071] Comparing Comparative Example 3 with Comparative Example 6 and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete all deteriorate significantly. If the porous polystyrene cationic microspheres are not modified and not sufficiently soaked in the iron solution, although they can adsorb a certain amount of polyacrylamide, they cannot carry out a degradation reaction on the adsorbed polyacrylamide and cannot be quickly absorbed into the pores of the microsphere structure, which affects the further absorption of polyacrylamide and also affects the water retention and internal curing effect of the porous polystyrene cationic microspheres.
[0072] Comparing Comparative Example 3 with Comparative Example 7, Comparative Example 8, and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete all deteriorate significantly. This is because the purpose of the pore size of the porous polystyrene cationic microspheres is to absorb amide molecules and water molecules. When the size is controlled between 5 and 20 nm, if the size is too small, it cannot adsorb water molecules and amide molecules well. Therefore, the modification effect is poor. If the size is too large, the capillary adsorption effect on water molecules decreases, and the storage performance after absorbing hydrated amide molecules is poor. Therefore, the modification effect is also poor.
[0073] Comparing Comparative Example 3 with Comparative Example 9 and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete all deteriorate significantly. Because when the temperature is insufficient, the amidation reaction and the silicone amide production reaction are insufficient, resulting in insufficient modification effect on the manufactured sand.
[0074] Comparing Comparative Example 3 with Comparative Example 10 and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete all deteriorate significantly. This is because the purpose of controlling the moisture content is to reduce the solubility of polyacrylamide through too low moisture control, which is beneficial to the generation amount of insoluble substances and reduces the adverse effects of polyacrylamide. Too high moisture content will cause a small amount of polyacrylamide to still dissolve and adsorb on the surface of the manufactured sand, affecting the workability of the concrete.
[0075] Comparing Example 3 with Comparative Example 12 and Comparative Example 11, the slump, slump retention performance, and compressive strength of the concrete are all significantly deteriorated. Since no modification is carried out, the fluidity can only be improved through the morphological effect of the porous microspheres, and the polyacrylamide is not rationally treated, so the adverse effects of the polyacrylamide cannot be avoided. Therefore, the improvement of the concrete fluidity is limited, the slump retention performance improvement is limited, and the strength enhancement effect is limited.
Claims
1. A method for preparing modified microspheres, characterized in that, Comprising: Soaking the porous polystyrene cation microspheres in an excessive amount of iron salt solution, and ultrasonically dispersing for more than 30 min. After sufficient infiltration, draining to obtain the modified microspheres; The modified microspheres are modified porous polystyrene cation microspheres formed by attaching a large number of cations on the surface of porous polystyrene microspheres through treatment; The iron salt solution is a saturated iron salt solution, and its dosage is such that it can completely soak the porous polystyrene cation microspheres.
2. The preparation method of a modified microsphere according to claim 1, characterized in that, The particle size of the porous polystyrene cation microspheres is 0.1 - 0.5 mm.
3. The preparation method of a modified microsphere according to claim 1, wherein The iron salt is selected from any one of ferric nitrate, ferric chloride, and ferric sulfate.
4. The preparation method of a modified microsphere according to claim 2, characterized in that The pore size of the modified porous polystyrene cation microspheres is 20 - 50 nm, and the microsphere size is 0.1 - 0.5 mm.
5. A method for optimizing the performance of washed manufactured sand of modified microspheres prepared by the method according to any one of claims 1 to 4, characterized in that, Comprising: Adding silane, calcium hydroxide, and modified microspheres to the washed manufactured sand, drying at 90°C - 130°C until the moisture content is not higher than 1%, and maintaining the temperature for 6 - 8 h to obtain the manufactured sand with optimized performance; The mass fractions of each raw material component are as follows: Among them, the manufactured sand is the manufactured sand washed with water and polyacrylamide flocculant, and its dosage is the mass fraction of the manufactured sand after removing water.