Preparation method of viscosity-reducing additive based on mechanism sand concrete

Abstract

The application discloses a kind of based on mechanism sand concrete's viscosity-reducing type admixture preparation method, belong to energy-saving and environment-protecting technical field.The method includes the following steps: silica sol is added to mixed solvent, after adjusting pH, 3- (methacryloyloxy) propyl trimethoxysilane is added, heating reaction obtains dispersion liquid;Acrylic acid, methoxy polyethylene glycol methacrylate, 2-acrylamide-2-methylpropane sulfonic acid, 2- (methacryloyloxy) ethyl dimethyl (3-sulfopropyl) ammonium inner salt and deionized water are mixed, pH is adjusted, ammonium persulfate is added to polymerize and obtain first mother liquor;Dispersion liquid, mercaptoacetic acid are added to first mother liquor, add heptadecafluorodecyl trimethoxysilane, heating obtains second mother liquor;The application realizes interface lubrication and dispersion stability by multi-scale composite strategy, significantly reduces mechanism sand concrete viscosity, improves pumpability and compatibility, and energy saving and environmental protection are considered.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection technology. Specifically, it relates to a method for preparing a viscosity-reducing admixture based on manufactured sand concrete. Background Technology

[0002] The aggregate structure of concrete is closely related to the rheological behavior of the slurry. With the increasing scarcity of natural river sand resources and stricter sand mining controls, manufactured sand is rapidly replacing river sand in engineering projects due to its stable source and controllable gradation. However, manufactured sand differs significantly from river sand in particle morphology, surface mineral composition, and fine powder content. This directly leads to increased water consumption in the mixture, higher plastic viscosity and yield stress, increased pumping resistance, insufficient slump retention, and increased risk of segregation and bleeding. Furthermore, its compatibility with commonly used polycarboxylate superplasticizers fluctuates significantly. Therefore, the research and development of "viscosity-reducing admixtures" for manufactured sand systems has become a key direction for improving pumpability and construction adaptability.

[0003] Manufactured sand is typically produced from the crushing and sand-making processes of parent rocks such as limestone, granite, and basalt. Compared to river sand, its main characteristics include: sharp-edged particles, a high proportion of needle-like, flaky, and irregular shapes, leading to enhanced interparticle friction and mechanical interlocking; numerous newly formed surface cracks and defects, easily absorbing moisture and organic molecules; a higher content of stone powder (fine powder smaller than 0.075 mm), and a complex mineral composition, often containing active clay minerals (such as illite / montmorillonite mixtures, kaolinite, etc.) and soluble salt ions. These factors combined significantly increase the specific surface area and interfacial adsorption sites of the mixture, resulting in a decrease in the water-cement ratio and the effective utilization rate of admixtures. This manifests as increased plastic viscosity at the same slump and insufficient shear thinning, leading to a significant increase in construction energy consumption and pumping pressure.

[0004] From a rheological perspective, the high viscosity problem of manufactured sand concrete stems from the following factors: First, geometric gradation and morphology effects. The sharp edges and rough surfaces of particles increase the static friction coefficient and rolling resistance between particles, reducing particle rearrangement efficiency and making it difficult for the paste to form a continuous lubricating film on the aggregate. Second, the effect of fine powder and fine aggregates. High stone powder content increases the powder volume fraction and interfacial adsorption of the system, easily inducing a "bridging-agglomeration" structure, leading to a simultaneous increase in yield stress and plastic viscosity. Third, chemical adsorption and compatibility effects. Clay minerals and fine powders have a significant selective adsorption and stripping effect on polycarboxylate superplasticizers, altering the surface potential and dispersion state of cement particles, resulting in insufficient early dispersibility and rapid decline in slump retention and fluidity. Fourth, electrolyte and ionic strength effects. The release of soluble salts from manufactured sand and stone powder increases the ionic strength of the system, compressing the double layer thickness and weakening electrostatic repulsion, thereby promoting flocculation and increasing viscosity. Fifth, early hydration and structural building effects. Fine powder increases heterogeneous nucleation sites, accelerates the initial formation of CSH, and superimposed thixotropic structure reconstruction, resulting in increased viscosity and yield stress after shearing after standing.

[0005] To address the aforementioned issues, existing engineering solutions primarily focus on two approaches: raw material optimization and admixture control. At the raw material level, this includes optimizing the gradation of manufactured sand, controlling the content and particle size distribution of stone powder, employing sand washing and dry dust removal, and using mineral admixtures such as fly ash, slag powder, and quartz microspheres to improve particle packing and the continuity of the lubricating film. These methods can reduce water consumption and improve rheology to some extent, but they are significantly affected by the source and fluctuations of manufactured sand, resulting in insufficient on-site consistency, and their improvement on viscosity in high-strength and low water-cement ratio systems is limited.

[0006] At the admixture level, traditional approaches include using polycarboxylate superplasticizers (PCEs) to improve initial fluidity. However, in systems with high stone powder and clay content, PCE is preferentially adsorbed by fine powder and clay, leading to a decrease in effective dosage, a shortened slump retention time, and potentially inducing the dilemma of bleeding and segregation. Introducing viscosity modifiers (VMAs) such as cellulose ethers, xanthan gum, vesyl gum, and dimeric dextran can enhance bonding and anti-segregation capabilities. However, these VMAs tend to be more focused on a steady-state viscosity increase, often raising plastic viscosity while maintaining anti-segregation, which is detrimental to reducing pumping energy consumption. Using surfactants or lubricants (siloxanes, fatty alcohol polyoxyethylene ethers, etc.) to reduce interfacial tension and improve lubrication and spreading is effective in the short term, but its stability and durability are insufficient in high ionic strength and alkaline cement systems, and its ability to alleviate structured viscosity induced by fine powder is limited. Nanomaterials, such as nano-silica, layered silicates, or graphene oxide (GO), are used to reduce viscosity and enhance structural stability through interface modulation and sheet lubrication. However, nanomaterials tend to agglomerate and settle in systems with high electrolytes, strong alkalis, and high solids content, making it difficult to guarantee dispersibility and reproducibility. Furthermore, the synergistic mechanism with organic polymer additives remains unstable. Amphoteric or zwitterionic polymers are employed to alleviate the "adsorbent-scavenging" effect of clay and fine powders through electron neutralization and ion exchange, and to provide steric hindrance stability. While this can improve compatibility to some extent, the viscosity-reducing effect under low water-to-binder ratios and pumping shear fields remains limited.

[0007] In summary, existing technologies have three main shortcomings: First, it is difficult to balance viscosity reduction and steady-state operation. Many methods are effective in preventing segregation and maintaining slump, but at the cost of increasing system viscosity, which is detrimental to pumping and energy consumption control. Second, the system lacks stability and adaptability. Admixtures are prone to failure in the presence of high alkali, high ionic strength, and fine clay powder, or have a narrow adaptability window for manufactured sand from different sources, leading to large fluctuations in the field. Third, there are significant engineering problems with the dispersion. Nanomaterials or compound admixtures are prone to agglomeration, phase separation, efficacy decay, and metering errors under actual mixing conditions and during storage and transportation.

[0008] To address the aforementioned challenges, recent research has explored a "multi-scale composite" strategy. This involves a multi-layered approach, combining inorganic nanosols, organic comb-like polymers, low-surface-energy fragments, and two-dimensional sheet materials to achieve multi-level interfacial lubrication, steric hindrance, and electrical neutralization. Specific approaches include: using silica sol as a core to provide hard particle lubrication and nucleation effects; using comb-like polymers with polyether side chains (such as MPEG-based polymers) to provide strong steric hindrance and a hydration layer, maintaining the dispersion of cement particles and fine powder; introducing amphoteric or zwitterionic groups (such as AMPS and SBMA) to alleviate flocculation caused by electrolyte compression of the electrical double layer and to achieve more robust adsorption competition on clay surfaces; reducing internal friction and adhesion work through low-surface-energy groups such as fluorosilanes to improve lubrication under pumping shear; supplementing this with the "nano-bearing / sheet slip" effect of sheet materials such as GO to reduce interparticle rolling resistance; and simultaneously using small-molecule functional additives (such as citric acid-ethylenediamine carbon dots or complexes) to enhance the exfoliation and stability of nanosheets in strong electrolyte environments. The key to this strategy lies in three aspects: first, constructing a stable organic-inorganic hybrid interface to avoid secondary agglomeration of the nanophase; second, maintaining long-term dispersion stability in alkaline and high ionic strength systems; and third, loading the active phase onto an inert or compatible carrier (such as manufactured sand powder) to prepare granular admixtures that are easy to measure, easy to transport, and highly adaptable to on-site conditions.

[0009] Furthermore, from an engineering application perspective, the evaluation of viscosity-reducing admixtures should simultaneously consider workability indicators (slump, spread, etc.), rheological parameters (yield stress, plastic viscosity, thixotropic recovery), pumping energy consumption (pipeline pressure-flow curve), stability (segregation index, bleeding rate, air content), strength and durability retention (early strength, shrinkage, freeze-thaw cycles, and sulfate attack), and compatibility window with water-reducing agents. An ideal viscosity-reducing admixture should reduce plastic viscosity and pumping pressure without significantly increasing air entrainment or sacrificing strength, while maintaining good slump retention and anti-segregation capabilities; it should also be adaptable to manufactured sand systems with different parent rock types, stone powder content, and particle size distributions, with a wide dosage window and high field tolerance.

[0010] In summary, the challenges of "high viscosity, high energy consumption, and poor compatibility" in manufactured sand concrete are the result of a coupling of material structure, interfacial chemistry, and rheological physics. Existing single-dimensional modification methods are insufficient to simultaneously address multiple constraints such as geometric morphology, interfacial adsorption, ionic strength, and nanoscale dispersion stability. The approach of preparing viscosity-reducing admixtures based on multi-scale composite and in-situ construction can provide interfacial lubrication and dispersion stability at the micro- and nano-scale, while achieving pumpability and molding friendliness at the macro-scale, thus possessing significant engineering application value and widespread potential. Summary of the Invention

[0011] To address the problems of high plastic viscosity, high pumping resistance, insufficient slump retention, poor compatibility with polycarboxylate superplasticizers, easy agglomeration of nanoparticles, and weak engineering adaptability of admixtures in existing manufactured sand concrete technologies, this invention provides a viscosity-reducing admixture based on manufactured sand concrete and its preparation method. This method constructs a multi-scale composite system consisting of "inorganic nanosol-organic comb-low surface energy functional segments-two-dimensional lamellar materials-inert particulate carriers." Through the synergistic effects of interfacial lubrication, steric hindrance, electrical neutralization, and lamellar slip, it significantly reduces the rheological resistance of concrete mixtures and improves pumpability without sacrificing stability and strength.

[0012] The present invention adopts the following technical solution: a method for preparing a viscosity-reducing admixture based on manufactured sand concrete, comprising the following steps: (S1) preparing a sol: adding silica sol to a mixed solvent of 3-6 times its mass, adjusting the pH to 4.0-5.5, and then adding 3-(methacryloyloxy)propyltrimethoxysilane, wherein the mass ratio between silica sol and 3-(methacryloyloxy)propyltrimethoxysilane is 100:(1-5), followed by heating to react, to obtain To the dispersion; (S2) Preparation of the first mother liquor: Take 15-25 parts of acrylic acid, 8-18 parts of methoxy polyethylene glycol methacrylate, 2-6 parts of 2-acrylamide-2-methylpropanesulfonic acid, 1-5 parts of 2-(methacryloyloxy)ethyl dimethyl(3-sulfopropyl)ammonium inner salt and 40-60 parts of deionized water, adjust the pH to 6.0-7.5, add 0.2-0.6 parts of ammonium persulfate and carry out the polymerization reaction to obtain the first mother liquor; (S3) In-situ treatment: Take the first mother liquor from step (S 1) The obtained dispersion and mercaptoacetic acid are added to the first mother liquor and mixed well. The mass ratio of the dispersion, mercaptoacetic acid and the first mother liquor is (5-10):(10-20):(100-150). Heptadecafluorodecyltrimethoxysilane, which is 2-3 times the mass of the dispersion, is added and heated to obtain the second mother liquor. (S4) Preparation of nano-dispersion: Graphene oxide is added to the second mother liquor, which is 30-60 times its mass. The pH is adjusted to 6-7. Then graphene oxide is added. Add 5-10 times the amount of additives to the nano-dispersion by ultrasonic shearing to obtain a nano-dispersion; (S5) Compound preparation: Add 2-4 times the mass of the obtained nano-dispersion to the manufactured sand powder, then melt blend it, and then cure it for 15-25 minutes at a vacuum degree of 0.01-0.05MPa and a temperature of 80-100℃ to obtain cured particles. Then add 10-20 times the mass of the cured particles as a surface modifier, soak for 24-48 hours, and dry at 60℃ to obtain a viscosity-reducing additive.

[0013] Preferably, the parameters of the silica sol in step (S1) are as follows: average particle size 10-30nm, solid content 30-40wt%; the mixed solvent in step (S1) is a solution of ethanol and water mixed in a mass ratio of (50-70):(30-50).

[0014] Preferably, the parameters for the heating reaction in step (S1) are as follows: heating the reactor at 40-60℃ for 2-4 hours.

[0015] Preferably, the polymerization parameters in step (S2) are as follows: polymerization at 50-60℃ under nitrogen protection for 3-5 hours.

[0016] Preferably, the parameters for the heating treatment in step (S3) are as follows: under a nitrogen atmosphere, at a temperature of 70-90℃, and at a stirring speed of 400-600 r / min, the reaction is carried out for 2-4 hours.

[0017] Preferably, the preparation method of the auxiliary agent in step (S4) is as follows: citric acid and ethylenediamine are mixed at a mass ratio of 15:1, diluted with deionized water to a concentration of 10-20wt%, placed in a microwave reactor, with a power of 700-800W, a temperature of 170-190℃, and a time of 12-18min. After the reaction, the mixture is allowed to cool naturally, and impurities are removed by dialyzing at 1500Da for 48h to obtain the product.

[0018] Preferably, the parameters for ultrasonic shearing in step (S4) are as follows: 200W ultrasound for 10-20 minutes and shearing at 8000-12000 rpm for 15-30 minutes.

[0019] Preferably, the parameters for melt blending in step (S5) are as follows: a twin-screw extruder is used, the screw length-to-diameter ratio is (40-50):1, the temperature is 160-200℃, the rotation speed is 300-500rpm, and the time is 20-30min.

[0020] Preferably, the surface modifier in step (S5) is a mixed solution of isothiazolinone and polyether-modified polysiloxane in a mass ratio of 1:(2-4).

[0021] The raw materials used in step (S1) are as follows: silica sol, CAS No.: 7631-86-9; 3-(methacryloyloxy)propyltrimethoxysilane, CAS No.: 2530-85-0.

[0022] The raw materials used in step (S2) are as follows: Acrylic acid, CAS No.: 79-10-7; Methoxylated polyethylene glycol methacrylate, CAS No.: 26915-72-0; 2-Acrylamido-2-methylpropanesulfonic acid, CAS No.: 15214-89-8; 2-(Methacryloxy)ethyldimethyl(3-sulfopropyl)ammonium inner salt, CAS No.: 3637-26-1; Ammonium persulfate, CAS No.: 7727-54-0.

[0023] The raw materials used in step (S3) are as follows: mercaptoacetic acid, CAS No.: 68-11-1; heptadecafluorodecyltrimethoxysilane, CAS No.: 83048-65-1.

[0024] The raw materials in step (S4) are as follows: graphene oxide, CAS No.: 1034343-98-0, appearance: black or brownish-yellow powder, morphology: single-layer or few-layer graphene oxide flakes, thickness: 0.8-1.2nm, particle size: 1-15μm wide, single-layer flake ratio up to 80% or more, surface area: 120-247 square meters / gram, purity: ≥95%, specific gravity (density): approximately 2.259g / cm³. 3 (20℃). Citric acid, CAS No.: 77-92-9. Ethylenediamine, CAS No.: 107-15-3.

[0025] The raw materials used in step (S5) are as follows: isothiazolinone, CAS No.: 26172-55-4; polyether-modified polysiloxane, model BYK-333, purchased from BYK Chemicals, appearance: light brown liquid, density (20℃): approximately 1.04 g / cm³. 3 Viscosity (20℃): 15-20 mPa·s, Non-volatile content: 97-100 wt%, Flash point: about 101℃ (PMCC method), Water solubility: completely miscible, pH (10% aqueous solution): about 6, Shelf life: 5 years (60 months) under original packaging.

[0026] The above process generally requires key equipment such as a jacketed glass reactor (refluxable and nitrogen-introducible), an ultrasonic dispersion and high-shear equipment, a twin-screw extruder, and a vacuum oven / vacuum pump to cover the entire process of sol-polymerization-dispersion-melt blending-curing. At the same time, a chemical fume hood and an inert gas protection system should be configured, supplemented by purification devices such as centrifugation / rotary evaporation / dialysis and some characterization instruments to ensure performance and safety compliance. Reaction and synthesis: Jacketed glass reactor / basic chemical reaction system: Used for acid-catalyzed silane hydrolysis condensation and monomer polymerization of silica sol, and needs to have functions such as temperature control, stirring, reflux condensation, and inlet and outlet ports. Reflux condensation and solvent recovery accessories: The condenser and collection bottle配套 with the reactor are used to control the volatilization and reflux operation of ethanol / water, and ensure stable temperature and solvent management. Inert gas (nitrogen) protection and replacement system: Nitrogen cylinder, pressure reducing valve and inlet pipeline are used to control the oxygen-free environment for free radical polymerization and silane treatment. Stirring and temperature control unit: The oil bath / water bath or electric heating temperature control system cooperates with the reactor drive motor to meet the stability of long-term reaction in the range of 40-90 °C. Dispersion and exfoliation: Ultrasonic processor (probe type, about 200W): Used for ultrasonic exfoliation and dispersion of graphene oxide, and a typical 200W device such as UP200St is suitable for small to medium-sized samples. High-shear homogenizer / disperser (about 8000-12000 rpm): Combined with ultrasonic to improve the dispersion efficiency and scale feasibility of GO and nanophase. Rotary evaporator and centrifuge: Used for the rotary evaporation and centrifugation steps of solvent aging and ion / impurity removal after partial dispersion / functionalization. Forming and curing: Twin-screw extruder (L / D≈40-50): Meets the process requirements of melt blending, dispersion, exhaust and granulation, and is suitable for hot processing in the range of 160-200 °C. Vacuum drying / curing system: The vacuum oven is equipped with a rotary vane vacuum pump to achieve curing at 80-100 °C under a negative pressure of about 0.01-0.05 MPa and subsequent drying at 60 °C. Vacuum measurement and valve accessories: Vacuum gauge, valve group and inert gas interface are used for vacuum stability and inert replacement operation. Purification and post-treatment: Dialysis device: Select a dialysis membrane tube with a low molecular weight cut-off (such as 1-2 kDa level) to remove small molecule impurities, salts and unreacted components. Filtering and washing appliances: Combine centrifugation / washing process to remove impurities and purify the dispersion, and improve the stability of the nano-dispersion. Ventilation and safety: Chemical fume hood: Weighing and preparation of volatile / combustible / irritating substances such as ethanol, silane and isothiazolinone should be carried out in the fume hood to reduce the risk of steam accumulation and exposure. Inert gas facility safety: Nitrogen replacement and protection should be implemented in a reaction system with reflux condensation and compliant pipelines to avoid oxidation, side reactions and safety hazards.

[0027] Compared to existing technologies, this invention utilizes a multi-scale composite strategy to construct a viscosity-reducing admixture that significantly reduces plastic viscosity and pumping resistance in manufactured sand concrete systems, improving slump retention, anti-segregation ability, and compatibility with water-reducing agents, while simultaneously maintaining strength and engineering adaptability. The beneficial effects are described below from three aspects: performance indicators, synergistic mechanisms, and application advantages. Performance Indicator Improvement: Under typical manufactured sand concrete mix proportions (standard conditions such as cementitious material dosage and sand ratio), the admixture of this invention exhibits excellent rheological and pumping properties: plastic viscosity is controlled at 0.58-0.71 Pa·s, a reduction of approximately 50-65% compared to the comparative example's 1.38-1.55 Pa·s, significantly improving the shear thinning behavior and workability of the mixture. Yield stress is 14.2-16.9 Pa, a decrease of approximately 50-60% compared to the comparative example's 31.2-33.8 Pa, reducing interparticle interlocking and rearrangement resistance. The pumping pressure is reduced to 2.1-2.5 MPa, a decrease of approximately 50-60% compared to the comparative example's 4.6-5.2 MPa, effectively controlling pumping energy consumption and pipeline wear. The bleeding rate is 1.6-2.1%, a decrease of approximately 60% compared to the comparative example's 5.1-5.7%, enhancing anti-segregation stability. The 1-hour slump loss is 7.4-9.5%, an improvement of approximately 60-70% compared to the comparative example's 21.8-24.3%, extending the working time window. The 28-day compressive strength remains at 48-49 MPa, an increase of approximately 18-23% compared to the comparative example's 39-41 MPa, without sacrificing structural durability. These quantitative improvements, based on test data, verify the comprehensive superiority of this invention in multiple performance dimensions. Synergistic Mechanism: The beneficial effects stem from the multi-scale synergy of "inorganic nanosol-organic comb polymer-low surface energy functional segments-two-dimensional sheet materials-inert particle carrier": Silica sol provides hard core lubrication and nucleation effect, reducing interparticle rolling resistance and improving the interfacial transition zone. Methoxy polyethylene glycol side chains form a stable hydration layer and steric hindrance, maintaining dispersion and resisting fine powder adsorption. 2-Acrylamide-2-methylpropanesulfonic acid and zwitterionic monomers achieve electroneutrality buffering, mitigating ionic strength and flocculation induction of clay minerals. Heptadecafluorodecyltrimethoxysilane constructs a low surface energy interface, reducing adhesion work and internal friction. Graphene oxide sheets are stabilized and exfoliated by additives, achieving a "nano-bearing" slip effect, further reducing viscosity. The particle loading of manufactured sand powder ensures uniform release of the active phase, avoiding nanophase agglomeration and dosage deviation. This synergistic mechanism effectively covers multiple challenges such as the geometry, surface adsorption, and ionic effects of manufactured sand, surpassing the limitations of single-dimensional modification technologies.

[0028] The admixture of this invention is produced in granular form, which facilitates storage, transportation, and on-site metering. It is adaptable to manufactured sand systems with different parent rock types and stone powder contents, has a wide process parameter window (covering both endpoints and intermediate values), and exhibits strong robustness. Compared with traditional admixtures, it has higher stability in high-alkali, high-ionic-strength, and clay-containing environments, and has great potential for widespread application. It also balances energy conservation and environmental protection (such as reducing pumping energy consumption) with economic efficiency (reducing water consumption and admixture dosage). Attached Figure Description

[0029] Figure 1 This is an appearance diagram of the viscosity-reducing admixture prepared in Example 1 of this invention.

[0030] Figure 2 This is a scanning electron microscope image of the viscosity-reducing admixture prepared in Example 1 of this invention.

[0031] Figure 3 This is a physical image of the specimen prepared by the viscosity-reducing admixture in Example 1 of this invention. Detailed Implementation

[0032] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of mass is grams (g).

[0033] Example 1

[0034] Preparation of the sol: 100g of silica sol (average particle size 20nm, solid content 35wt%) was added to a mixed solvent (ethanol and water mixed at a mass ratio of 60:40) at 4.5 times its mass. After adjusting the pH to 4.75, 3g of 3-(methacryloyloxy)propyltrimethoxysilane was added (the mass ratio of silica sol to 3-(methacryloyloxy)propyltrimethoxysilane was 100:3). The mixture was then heated in a reactor at 50℃ for 3 hours to obtain a dispersion. Preparation of the first mother liquor: 20g of acrylic acid, 13g of methoxy polyethylene glycol methacrylate, 4g of 2-acrylamido-2-methylpropanesulfonic acid, 3g of 2-(methacryloyloxy)ethyldimethyl(3-sulfopropyl)ammonium inner salt, and 50g of deionized water were taken, the pH was adjusted to 6.75, 0.4g of ammonium persulfate was added, and polymerization was carried out at 55℃ under nitrogen protection for 4 hours to obtain the first mother liquor. In-situ treatment: The above dispersion and mercaptoacetic acid were added to the first mother liquor and mixed well. The mass ratio of the dispersion, mercaptoacetic acid and the first mother liquor was 7.5:15:125. Heptadecafluorodecyltrimethoxysilane was added at 2.5 times the mass of the dispersion. The mixture was reacted for 3 hours under a nitrogen atmosphere, at a temperature of 80°C and a stirring speed of 500 r / min to obtain the second mother liquor. Preparation of nano-dispersions: Graphene oxide was added to a second mother liquor at a mass ratio of 45, and the pH was adjusted to 6.5. Then, an auxiliary agent at a mass ratio of 7.5 was added. The mixture was sonicated at 200W for 15 min and sheared at 10000 rpm for 22.5 min to obtain nano-dispersions. The auxiliary agent was prepared as follows: Citric acid and ethylenediamine were mixed at a mass ratio of 15:1, diluted with deionized water to a concentration of 15 wt%, and placed in a microwave reactor at a power of 750W, a temperature of 180℃, and a time of 15 min. After the reaction, the mixture was allowed to cool naturally and dialyzed at 1500 Da for 48 h to remove impurities, thus obtaining the product. Compound preparation: Three times the mass of the obtained nano-dispersion was added to the nano-dispersion, followed by melt blending using a twin-screw extruder with a screw length-to-diameter ratio of 45:1, a temperature of 180℃, a rotation speed of 400 rpm, and a time of 25 min. The mixture was then cured under a vacuum of 0.03 MPa and a temperature of 90℃ for 20 min to obtain cured particles. Next, 15 times the mass of the cured particles was added to a surface modifier (a 1:3 mass ratio mixture of isothiazolinone and polyether-modified polysiloxane), and the mixture was soaked for 36 h and dried at 60℃ to obtain a viscosity-reducing admixture. The appearance of the prepared viscosity-reducing admixture is as follows. Figure 1 As shown, its scanning electron microscope image is as follows: Figure 2 As shown.

[0035] Examples 2-8 and Comparative Examples 1-8

[0036] Based on Example 1, the specific parameters of Examples 2-8 and Comparative Examples 1-8 are listed in the following tables. The tables are designed according to the progress of the steps, and each table reflects different parameter values ​​of the examples / comparative examples, covering all endpoint values ​​and intermediate values.

[0037] Table 1: Parameters for sol preparation (S1)

[0038]

[0039] Table 2: Parameters for preparing sol (S1, comparative example)

[0040]

[0041] Table 3: Parameters for the preparation of the first mother liquor (S2)

[0042]

[0043] Table 4: Parameters for the preparation of the first mother liquor (S2, comparative example)

[0044]

[0045] Table 5: Parameters for in-situ processing (S3)

[0046]

[0047] Table 6: Parameters of in-situ treatment (S3, comparative example)

[0048]

[0049] Table 7: Parameters for preparing nanodispersions (S4)

[0050]

[0051] Table 8: Parameters for preparing nanodispersions (S4, comparative example)

[0052]

[0053] Table 9: Parameters of composite modulation (S5)

[0054]

[0055] Table 10: Parameters of composite modulation (S5, comparative example)

[0056]

[0057] To verify the performance of the viscosity-reducing admixture for manufactured sand concrete described in this invention, multi-dimensional tests were conducted on the products prepared in Examples 1-8 and Comparative Examples 1-8. The tests included rheological properties (plastic viscosity Pa·s and yield stress Pa), pumpability (pumping pressure MPa), stability (bleeding rate %), strength retention (28-day compressive strength MPa), and slump retention (1-hour slump loss %). All test data were based on actual material properties (e.g., plastic viscosity of 0.5-1.0 Pa·s is considered excellent; bleeding rate <3% is considered stable). The test methods are as follows: Rheological property test: Plastic viscosity and yield stress were measured using a rotational viscometer (model: Brookfield DV-II) with a rotational speed range of 10-100 s. -1 Pumping performance test: A concrete pump (model: SanyHBT60) was used to simulate pumping, and the pipeline pressure (MPa) was recorded. Stability test: Bleeding rate (%) was measured according to GB / T50080-2016 standard. Strength retention test: Specimens were molded according to GB / T50081-2019 standard. The specimen prepared in Example 1 is shown below. Figure 3 As shown, the compressive strength (MPa) was tested after 28 days of curing. Slump retention test: the initial slump and the slump after 1 hour were measured, and the loss rate (%) was calculated.

[0058] Table 11: Performance Test Results

[0059]

[0060] Table 12: Performance Test Results II

[0061]

[0062] The technical effects of this invention are that it significantly reduces the plastic viscosity and pumping resistance of manufactured sand concrete through a multi-scale composite strategy, improves slump retention, segregation resistance and compatibility with water-reducing agents, while maintaining or enhancing the concrete strength, taking into account energy conservation, environmental protection and engineering adaptability.

[0063] Based on test data, this admixture exhibits excellent performance in standard manufactured sand concrete mixes: plastic viscosity is reduced to 0.58-0.71 Pa·s, a 50-65% decrease compared to the comparative example (1.38-1.55 Pa·s), improving shear thinning behavior and workability. Yield stress is reduced to 14.2-16.9 Pa, a 50-60% decrease compared to the comparative example (31.2-33.8 Pa), reducing interparticle interlocking resistance. Pumping pressure is reduced to 2.1-2.5 MPa, a 50-60% decrease compared to the comparative example (4.6-5.2 MPa), controlling pumping energy consumption and pipeline wear. Bleeding rate is reduced to 1.6-2.1%, approximately 60% lower than the comparative example (5.1-5.7%), enhancing segregation resistance. 1-hour slump loss is reduced to 7.4-9.5%, a 60-70% improvement compared to the comparative example (21.8-24.3%), extending the working time window. The 28-day compressive strength increased to 48-49 MPa, a 18-23% improvement compared to the comparative example (39-41 MPa), without sacrificing structural durability. The synergistic mechanism stems from a multi-scale synergy involving "inorganic nanosol-organic comb-low surface energy functional segments-two-dimensional sheet materials-inert particle carrier": silica sol provides hard core lubrication and nucleation effects, reducing rolling resistance. Polyether side chains form a hydration layer and steric hindrance, maintaining dispersion and resisting fine powder adsorption. Zwitterionic groups provide an electrically neutral buffer, mitigating ionic strength and clay flocculation. Fluorosilanes construct low surface energy interfaces, reducing adhesion work and internal friction. Graphene oxide sheets are stabilized and exfoliated by additives, achieving a "nano-bearing" slip effect. Mechanized sand powder loading ensures uniform release of the active phase, avoiding agglomeration and dosage deviation. This mechanism addresses multiple challenges related to geometry, surface adsorption, and ionic effects. The advantages of this application are as follows: the admixture is produced in granular form, which facilitates storage, transportation, and on-site metering; it is adaptable to different types of manufactured sand and stone powder content; it has a wide process parameter window and strong robustness; it exhibits high stability in high-alkali, high-ionic-strength, and clay-containing environments, and has great potential for widespread application; at the same time, it reduces pumping energy consumption and water usage, achieving energy conservation, environmental protection, and economic improvement.

[0064] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing a viscosity-reducing type of admixture based on a manufactured sand concrete, characterized by: The method comprises the following steps: (S1) preparing a sol: adding a silica sol into a mixed solvent with a mass of 3-6 times of the silica sol, adjusting the pH value to 4.0-5.5, and then adding 3-(methacryloyloxy) propyl trimethoxysilane, wherein the mass ratio of the silica sol to the 3-(methacryloyloxy) propyl trimethoxysilane is 100:(1-5), and then heating and reacting to obtain a dispersion liquid; (S2) preparing a first mother liquor: taking 15-25 parts of acrylic acid, 8-18 parts of methoxy polyethylene glycol methacrylate, 2-6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 1-5 parts of 2-(methacryloyloxy) ethyl dimethyl (3-sulfopropyl) ammonium inner salt and 40-60 parts of deionized water, adjusting the pH value to 6.0-7.5, adding 0.2-0.6 parts of ammonium persulfate, and performing a polymerization reaction to obtain the first mother liquor; (S3) in-situ treatment: adding the dispersion liquid obtained in the step (S1) and mercaptoacetic acid into the first mother liquor and uniformly mixing, wherein the mass ratio of the dispersion liquid, the mercaptoacetic acid and the first mother liquor is (5-10):(10-20):(100-150), adding 2-3 times of the mass of the dispersion liquid of heptadecafluorodecyl trimethoxysilane, and heating and treating to obtain a second mother liquor; (S4) preparing a nanodispersion: adding graphene oxide into the second mother liquor with a mass of 30-60 times of the graphene oxide, adjusting the pH value to 6-7, and then adding an additive with a mass of 5-10 times of the graphene oxide, and performing ultrasonic shearing treatment to obtain the nanodispersion; (S5) compounding and modulating: adding 2-4 times of the mass of the nanodispersion of machine-made sand powder into the obtained nanodispersion, and then performing melt blending, and then solidifying for 15-25 min under a vacuum degree of 0.01-0.05 MPa and a temperature of 80-100 DEG C to obtain solidified particles, and then adding a surface modifier with a mass of 10-20 times of the mass of the solidified particles, soaking for 24-48 h, and drying at 60 DEG C to obtain a viscosity-reducing type admixture.

2. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: In the step (S1), the silica sol has the following parameters: an average particle size of 10-30 nm and a solid content of 30-40 wt%.

3. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: In the step (S1), the heating and reaction has the following parameters: heating a reaction kettle for 2-4 h at 40-60 DEG C.

4. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: In the step (S2), the polymerization reaction has the following parameters: polymerizing for 3-5 h at 50-60 DEG C under nitrogen protection.

5. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: In the step (S3), the heating and treatment has the following parameters: reacting for 2-4 h under the conditions of a nitrogen atmosphere, a temperature of 70-90 DEG C and a stirring speed of 400-600 r / min.

6. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: In the step (S4), the additive is prepared in the following manner: mixing citric acid and ethylenediamine according to a mass ratio of 15:1, diluting with deionized water to a concentration of 10-20 wt%, placing in a microwave reactor, setting a power of 700-800 W, a temperature of 170-190 DEG C and a time of 12-18 min, naturally cooling after the reaction, removing impurities by dialysis for 48 h at 1500 Da, and obtaining the product.

7. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: The parameters of ultrasonic shearing treatment in step (S4) are as follows: 200W ultrasonic for 10-20min and shearing at 8000-12000rpm for 15-30min.

8. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: The parameters of melt blending in step (S5) are as follows: using a twin-screw extruder, the screw length-diameter ratio is (40-50):1, the temperature is 160-200℃, the rotating speed is 300-500rpm, and the time is 20-30min.

9. The method of producing a viscosity-reducing admixture based on concrete with manufactured sand according to claim 1, characterized in that: The surface modifier in step (S5) is a mixed solution with a mass ratio of isothiazolinone to polyether-modified polysiloxane being 1:(2-4).

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