Viscosity modified material for maintaining homogeneity of self-compacting concrete, preparation method and application

Abstract

The invention discloses a viscosity modified material for keeping the homogeneity of self-compacting concrete, a preparation method and application. The material comprises the following components in parts by mass: fly ash, slag powder, metakaolin, cellulose ether, limestone powder, zeolite powder, an air entraining agent, a functional component A and a functional component B, wherein the functional component A is prepared by compounding and drying nano silica fume, modified carbon nanotubes subjected to ultrasonic dispersion by sodium dodecyl benzene sulfonate / absolute ethyl alcohol and tungsten disulfide subjected to activation-silanization-polycarboxylic acid modification treatment, and the functional component B is prepared by shearing and uniformly mixing magnesium oxide and a calcium expanding agent at a high speed. The material can improve the viscosity, delay segregation and bleeding and reduce the water use sensitivity under the condition that the yield stress is not obviously improved, meanwhile, the early strength development is promoted, the volume stability is improved, and the durability such as chloride ion permeation resistance is improved, so that the homogeneity and quality consistency of a component in the pouring process and after hardening are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of concrete slurry preparation technology, specifically to a viscosity-modifying material for maintaining the homogeneity of self-compacting concrete, its preparation method, and its application. Background Technology

[0002] Self-compacting concrete (SCC) is a type of high-performance concrete that achieves flow, filling, and self-compacting under its own weight, making it particularly suitable for casting densely reinforced, complex, or difficult-to-vibrate components. Existing SCCs typically achieve high fluidity by increasing the paste volume, optimizing aggregate gradation, and incorporating high-efficiency water-reducing agents to fully fill corners of formwork and gaps between reinforcing bars. However, compared to conventional vibrated concrete, SCC operates in a more fluid state, with more significant relative movement between the paste and aggregate. Aggregate settlement and paste floating are more likely to occur, leading to segregation, bleeding, and localized aggregate or paste enrichment. This results in significant heterogeneity along the height of the hardened concrete or in localized areas. This heterogeneity not only causes spatial fluctuations in strength and elastic modulus but also leads to uneven distribution of interface transition zones and pore structures, affecting the overall reliability and service life of the structure.

[0003] To suppress segregation and maintain the stability of the mixture, existing technologies typically introduce viscosity-modifying materials or increase the total amount of cementitious materials to delay particle stratification by improving the slurry's cohesiveness and structural retention. However, this approach often has two limitations: First, traditional viscosity-modifying materials rely on thickening the aqueous phase or increasing the static yield stress to achieve stability, which can lead to increased water sensitivity. This results in greater sensitivity to the water-cement ratio, admixture dosage, and environmental conditions at the same target flowability. Amplified field fluctuations can easily lead to risks such as reduced slump expansion, increased pumping resistance, or mixture instability. Second, increasing the amount of cementitious materials to ensure self-compacting performance significantly increases the risk of early hydration heat release and auto-shrinkage. Furthermore, without sufficient optimization of the microstructure, insufficient early strength, increased cracking tendency, and inadequate resistance to permeation and chloride ion intrusion may still occur due to water-rich areas, segregation channels, or interface defects in the slurry. Especially under high flow conditions, if the cohesiveness of the slurry is mainly obtained by increasing the yield stress, it often sacrifices the flow retention and filling capacity, resulting in the contradiction of "stability and flowability are difficult to balance". If only mineral admixtures or fine powder fillers are used to increase viscosity, the stability effect is prone to significant fluctuations under different water-cement ratios and different admixture systems, making it difficult to simultaneously meet the comprehensive requirements of low segregation, low shrinkage, early strength and improved durability.

[0004] Therefore, there is an urgent need for a viscosity modifier and its supporting functional component system for self-compacting concrete. This system should be able to effectively increase viscosity and delay segregation without significantly increasing the static and dynamic yield stress of the slurry, thereby reducing water sensitivity and improving cohesion and homogeneity retention during the pouring process. At the same time, it should also take into account early strength development and microstructure densification, reduce the risk of shrinkage cracking, and improve durability properties such as resistance to chloride ion penetration, so as to meet the requirements of structural quality consistency and long-term service reliability under non-vibration construction conditions for complex components.

[0005] Purpose of the invention To overcome the shortcomings of existing technologies, the present invention aims to provide a viscosity-modifying material, its preparation method, and its application for maintaining the homogeneity of self-compacting concrete. The material comprises, by weight, fly ash, slag powder, metakaolin, cellulose ether, limestone powder, zeolite powder, an air-entraining agent, functional component A, and functional component B. Functional component A is prepared by compounding and drying nano-silica fume, modified carbon nanotubes ultrasonically dispersed in sodium dodecylbenzenesulfonate / anhydrous ethanol, and tungsten disulfide modified by activation-silanization-polycarboxylic acid treatment. Functional component B is obtained by high-speed shear uniform mixing of magnesium oxide and a calcium-based expanding agent. This material can increase viscosity, delay segregation and bleeding, and reduce water sensitivity without significantly increasing yield stress. Simultaneously, it promotes early strength development, improves volume stability, and enhances durability properties such as resistance to chloride ion penetration, thereby ensuring the homogeneity and quality consistency of the component during casting and after hardening.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A viscosity modifier for maintaining the homogeneity of self-compacting concrete comprises the following components by weight: 20-30 parts fly ash, 18-22 parts slag powder, 15-25 parts metakaolin, 0.1-0.3 parts cellulose ether, 11-18 parts limestone powder, 8-11 parts zeolite powder, 0.1-0.3 parts air-entraining agent, 5-8 parts functional component A, and 3-10 parts functional component B.

[0007] Preferably, the functional component A is a mixture of nano-silica fume, modified carbon nanotubes, and modified tungsten disulfide in a mass ratio of 3-4:1-2:1-2.

[0008] Preferably, the functional component A is prepared by the following steps: S11. Preparation of modified carbon nanotubes: Sodium dodecylbenzenesulfonate and anhydrous ethanol (dehydrated by 3 Å molecular sieve for 24-28 h) were weighed at a mass ratio of 0.006-0.01:10-15, respectively. The sodium dodecylbenzenesulfonate was dissolved in anhydrous ethanol to form a dispersion. The weighed carbon nanotubes were added to the dispersion, and the carbon nanotube dispersion was modified using a probe-type ultrasonic processor with an ultrasonic power of 400-450 W and an ultrasonic time of 25-45 min to obtain a modified carbon nanotube-anhydrous ethanol dispersion. S12. Preparation of modified tungsten disulfide: S121. Weigh tungsten disulfide powder and deionized water at a mass ratio of 0.005-0.02:10-15. Add the tungsten disulfide powder to the deionized water and stir mechanically for 5-10 min. Then add hydrogen peroxide solution and control the concentration of hydrogen peroxide in the system to be 0.5-2.0 wt%. Stir the reaction at 25-40℃ for 30-40 min. Centrifuge, wash, resuspend in anhydrous ethanol and centrifuge 2-3 times to obtain tungsten disulfide-ethanol wet slurry. S122. Mix ethanol and deionized water at a mass ratio of 80-85:20-25, adjust the pH to 4-5 with glacial acetic acid, stir for 15-30 min, add tungsten disulfide-ethanol wet slurry and silane coupling agent, stir and react at 40-60℃ for 1-3 h, centrifuge and wash to obtain silanized tungsten disulfide-ethanol wet slurry. S123. The silanized tungsten disulfide-ethanol wet slurry is resuspended in anhydrous ethanol to form a stirable slurry. Polycarboxylate superplasticizer is added and stirred for 30-60 min to obtain a modified tungsten disulfide-anhydrous ethanol dispersion. S13. Pre-dispersion of nano silica fume: Add the weighed nano silica fume to dehydrated anhydrous ethanol and stir mechanically for 5-10 minutes to form a pre-dispersion slurry of nano silica fume; S14. Preparation of functional material A: The modified tungsten disulfide-anhydrous ethanol dispersion and the modified carbon nanotube-anhydrous ethanol dispersion are mixed and mechanically stirred for 5-10 min for premixing. The nano silica fume pre-dispersion slurry is then added and ultrasonicated at 400-450W power for 35-40 min to obtain silica fume-modified carbon nanotube-modified tungsten disulfide dispersion. The dispersion is then placed in a slightly vacuum forced-air drying oven and dried at 65-70℃ for 1-2 h, and then dried at 75-85℃ for 2-3 h to obtain functional material A.

[0009] Preferably, in step S122, the mass ratio of the tungsten disulfide-ethanol wet slurry to the silane coupling agent is 1:1-4; in step S123, the mass ratio of the polycarboxylate superplasticizer to the silanized tungsten disulfide-ethanol wet slurry is 1-6:1; and in step S14, the vacuum degree of the forced-air drying oven is -0.02 to -0.05 MPa.

[0010] Preferably, the functional component B is a mixture of magnesium oxide and calcium expansion agent in a mass ratio of 1-2.5:3-5.

[0011] Preferably, the functional component B is prepared by the following method: Magnesium oxide and calcium expansion agent were weighed separately according to their mass fractions and mixed evenly using a continuously variable speed shear mixer to obtain the functional component B. The continuously variable speed shear mixer had an angular velocity and rotational speed of 1000-1200 r / min and a linear velocity of 10-15 m / s, thereby utilizing the generated high-speed shear mixing force to achieve uniform mixing of powder particles and minimize damage to the original structure of the raw materials.

[0012] Preferably, the fly ash has an average particle size of <5μm, a maximum particle size of <20μm, and a density of <2.6g / cm³. 3 The loss on ignition is less than 1.5%; the average particle size of the slag powder is <5μm, the maximum particle size is <20μm, and the density is ≥2.88g / cm³. 3 Specific surface area ≥ 420m² 2 / kg; the average particle size of the metakaolin is <3μm, and the maximum particle size is <8μm; the calcium carbonate content of the limestone powder is ≥85%, the methylene blue value is ≤0.5g / kg, and the fineness range is 800-1250 mesh.

[0013] Preferably, the cellulose ether is further defined as sodium carboxymethyl cellulose, with a pH range of 5-9 and a viscosity of 300-600 mPa·S; the air-entraining agent is further defined as a saponin-based air-entraining agent.

[0014] A method for preparing a viscosity-modified material that maintains the homogeneity of self-compacting concrete, comprising the following steps: Fly ash, slag powder, metakaolin, cellulose ether, limestone powder, zeolite powder, air-entraining agent, functional component A, and functional component B are weighed out according to their respective mass proportions. They are then mixed evenly using a continuously variable speed shear mixer to obtain the viscosity-modified material that maintains the homogeneity of self-compacting concrete. The continuously variable speed shear mixer has an angular velocity and rotational speed of 1000-1200 r / min and a linear velocity of 10-15 m / s.

[0015] Application of a viscosity-modifying material that maintains the homogeneity of self-compacting concrete in the field of concrete preparation.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a multi-scale particle size distribution and active filling system using fly ash, slag powder, metakaolin, limestone powder, and zeolite powder, and combines it with cellulose ether and saponin-based air-entraining agents to achieve slurry water retention and bubble stability. Simultaneously, functional component A adopts a composite structure of nano-silica fume, modified carbon nanotubes, and modified tungsten disulfide. The carbon nanotubes are uniformly distributed through ultrasonic dispersion using sodium dodecylbenzenesulfonate / anhydrous ethanol, while the tungsten disulfide undergoes activation, silanization, and polycarboxylic acid treatment to achieve better dispersion stability and interfacial compatibility. This allows the system to significantly increase the viscosity of the slurry without significantly increasing the static and dynamic yield stresses, thereby effectively prolonging the time for segregation and bleeding of the mixture, maintaining homogeneity during casting, and significantly reducing water sensitivity. Furthermore, the synergistic pozzolanic reaction and micro-filling effect of nano-silica fume with metakaolin and slag powder promote the generation of hydration products and densification of pore structure. Combined with the microcrack passivation and bridging effect of modified carbon nanotubes and modified tungsten disulfide, it improves early strength and crack resistance. After the magnesium oxide and calcium expansion agent in functional component B are evenly dispersed, more uniform volume compensation can be achieved, reducing shrinkage deformation and cracking risk. Under the combined effect, the present invention significantly improves the anti-segregation and bleeding performance, strength development and chloride ion penetration resistance of self-compacting concrete while ensuring high fluidity. Furthermore, the stable air-entraining system and optimized pore structure make freeze-thaw durability less susceptible to adverse effects. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation process of functional component A according to the present invention; Figure 2 This is a graph showing the viscosity test data of the reference group C1 and the test group C2 described in this invention; Figure 3 This is a graph showing the compressive strength test data of the reference group D1 and the test group D2 described in this invention; Figure 4 This is a graph showing the water sensitivity test data of test groups D1 and D2 described in this invention. Detailed Implementation

[0018] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1-4 The present invention provides a technical solution: The detailed specifications of the fly ash, slag powder, metakaolin, limestone powder, and zeolite powder used in the various embodiments of the present invention are as follows: The fly ash is ultrafine fly ash, with an average particle size of <5μm, a maximum particle size of <20μm, and a density of <2.6g / cm³. 3 The loss on ignition is less than 1.5%, the activity after 28 days is >80%, CaO (10-15)%, SiO2 (40-55)%, Al2O3 (15-25)%, and other indicators meet the requirements of GB / T1596 "Fly Ash for Cement and Concrete". The slag powder is S105 grade granulated blast furnace slag powder, with an average particle size of <5μm, a maximum particle size of <20μm, CaO (36-42)%, SiO2 (30-35)%, Al2O3 (13-17)%, and a density ≥2.88g / cm³. 3 Specific surface area ≥ 420m² 2 / kg, and other indicators meet GB / T18046 "Granulated Blast Furnace Slag Powder for Cement and Concrete"; The metakaolin has an average particle size of <3μm, a maximum particle size of <8μm, SiO2 (45-55)%, Al2O3 (35-45)%, and other indicators meet the requirements of DB53_T ​​843-2017 "Metakaolin for Concrete". The limestone powder is heavy calcium carbonate with a calcium carbonate content ≥85%, a methylene blue value ≤0.5g / kg, a fineness range of 800-1250 mesh, and other indicators meet GB35164-2017 "Limestone Powder for Cement, Mortar and Concrete". The zeolite powder is clinoptilolite, with a fineness of 325 mesh, an ammonium adsorption value ≥100 meq / 100g, and a density of 2.2-2.4 g / cm³. 3 The bulk density is 700-800 kg / m³ 3 The 28-day compressive strength of cement mortar is ≥60%. SiO2 content >70%, Al2O3 (10%-15%), alkali content <2%.

[0020] Example 1 This embodiment provides a formulation for a viscosity modifier that maintains the homogeneity of self-compacting concrete. The formulation comprises the following components by weight, as shown in Table 1 (one part by weight is defined as 10g): Table 1. Component ratio of viscosity modifier 1 The cellulose ether is further specified as sodium carboxymethyl cellulose, which is a white, odorless, non-toxic, free-flowing fibrous powder that is hygroscopic, has a pH range of 5.0-9.0, and a viscosity of 300-600 mPa·S. The air-entraining agent is further specified as a saponin-based air-entraining agent, the main component of which is triterpenoid saponin, an organic compound extracted from the natural wild plant Gleditsia sinensis. It is powdery, brown in color, has a specific gravity of 1.3, is easily soluble in water, and has strong chemical stability to acids, alkalis and hard water.

[0021] The functional component A is prepared through the following steps: S11. Preparation of modified carbon nanotubes: Sodium dodecylbenzenesulfonate and anhydrous ethanol (dehydrated by 3Å molecular sieve for 24 hours) were weighed at a mass ratio of 0.006:10. The sodium dodecylbenzenesulfonate was dissolved in anhydrous ethanol to form a dispersion. The weighed carbon nanotubes were added to the dispersion. The carbon nanotube dispersion was modified using a probe-type ultrasonic processor with an ultrasonic power of 400W and an ultrasonic time of 30min to obtain a modified carbon nanotube-anhydrous ethanol dispersion. S12. Preparation of modified tungsten disulfide: S121. Weigh tungsten disulfide powder and deionized water at a mass ratio of 0.005:10. Add tungsten disulfide powder to deionized water and stir mechanically for 5 min. Then add hydrogen peroxide solution and control the concentration of hydrogen peroxide in the system to 1 wt%. Stir the reaction at 25°C for 30 min. Centrifuge, wash, resuspend in anhydrous ethanol and centrifuge twice to obtain tungsten disulfide-ethanol wet slurry. S122. Mix ethanol and deionized water at a mass ratio of 80:20, adjust the pH to 4 with glacial acetic acid, stir for 15 min, add tungsten disulfide-ethanol wet slurry and silane coupling agent, stir and react at 40℃ for 3 h, centrifuge and wash to obtain silanized tungsten disulfide-ethanol wet slurry. S123. The silanized tungsten disulfide-ethanol wet slurry is resuspended in anhydrous ethanol to form a stirable slurry. Polycarboxylate superplasticizer is added and stirred for 60 min to obtain a modified tungsten disulfide-anhydrous ethanol dispersion. S13. Pre-dispersion of nano silica fume: The weighed nano silica fume is first added to dehydrated anhydrous ethanol and mechanically stirred for 5 minutes to form a pre-dispersion slurry of nano silica fume; S14. Preparation of functional material A: The modified tungsten disulfide-anhydrous ethanol dispersion and the modified carbon nanotube-anhydrous ethanol dispersion are mixed and mechanically stirred for 5 min for premixing. The nano silica fume pre-dispersion slurry is then added and ultrasonicated at 400W for 35 min to obtain silica fume-modified carbon nanotube-modified tungsten disulfide dispersion. The dispersion is then placed in a slightly vacuum forced-air drying oven and dried at 65℃ for 1 h, and then dried at 75℃ for 2 h to obtain functional material A.

[0022] The carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of 5-50 nm, an outer diameter of 0.5-20 μm, a carbon content of ≥95%, an ash content of ≤2.0%, and a specific surface area of ​​120-400 m² / g. The nano-silica fume is an amorphous silica powder with a SiO2 content ≥90%, a primary particle size of 10-300 nm, an aggregate D50 of 0.2-5 μm, a specific surface area of ​​50-250 m² / g, and a loss on ignition ≤3.0%. The tungsten disulfide is a layered tungsten disulfide powder with the main crystalline phase being 2H-WS2. Its purity (as WS2) is ≥90%, the secondary particle size D50 is 0.2-10μm, the specific surface area is 5-80 m² / g, the moisture content is ≤2.0%, and the oxygen content (as O) is ≤5.0%. In step S122, the mass ratio of the tungsten disulfide-ethanol wet slurry to the silane coupling agent is 1:4; the type of the silane coupling agent is KH-570. In step S123, the mass ratio of the polycarboxylate superplasticizer to the silanized tungsten disulfide-ethanol wet slurry is 3:1, and the polycarboxylate superplasticizer is model PCE-201. In step S14, the vacuum degree of the blower oven is -0.02MPa.

[0023] The functional component B is prepared through the following steps: Magnesium oxide and calcium expansion agent were weighed separately according to their mass fractions and mixed evenly using a continuously variable speed shear mixer to obtain the functional component B. The continuously variable speed shear mixer had an angular velocity of 1000 r / min and a linear velocity of 10 m / s, thereby utilizing the generated high-speed shear mixing force to achieve uniform mixing of powder particles and minimize damage to the original structure of the raw materials.

[0024] The magnesium oxide is further specified as R-type magnesium oxide, obtained by calcining first-grade magnesite raw material at 600-800℃, with MgO content ≥90%, active MgO content ≥85%, free CaO <1%, and specific surface area >400m². 2 / kg, 7-day limited expansion rate in water at 20℃ ≥0.020%, 28-day limited expansion rate ≥0.10%; The calcium-based expansive agent is a type I calcium oxide concrete expansive agent, which, after being mixed with cement and water, undergoes a hydration reaction to generate calcium hydroxide, with a specific surface area >300 m². 2 / kg, 7-day limiting expansion rate in water ≥0.035%, 21-day limiting expansion rate in air ≥-0.015%.

[0025] This embodiment also provides a method for preparing a viscosity-modifying material that maintains the homogeneity of self-compacting concrete, comprising the following steps: Fly ash, slag powder, metakaolin, cellulose ether, limestone powder, zeolite powder, air-entraining agent, functional component A, and functional component B are weighed out according to their respective weight proportions. They are then mixed evenly using a continuously variable speed shear mixer to obtain the viscosity-modified material that maintains the homogeneity of self-compacting concrete. The continuously variable speed shear mixer has an angular velocity of 1000 r / min and a linear velocity of 10 m / s.

[0026] Example 2 Example 2 differs from Example 1 in that, in Example 2, the viscosity modifier for maintaining the homogeneity of self-compacting concrete comprises the following components by weight, as shown in Table 2 (one part by weight is defined as 10g): Table 2. Component ratio of viscosity modifier 2 The remaining steps are exactly the same as in Example 2 and Example 1.

[0027] Example 3 Example 3 differs from Example 1 in that, in Example 3, the viscosity modifier for maintaining the homogeneity of self-compacting concrete comprises the following components by weight, as shown in Table 3 (one part by weight is defined as 10g): Table 3. Component ratio of viscosity modifier 3 The remaining steps are exactly the same as in Example 3 and Example 1.

[0028] Performance testing Cement paste viscosity test: The viscosity of cement paste was tested according to the method specified in GB / T 10247. The composition of the reference group cement paste is shown in Group C1 of Table 4. The viscosity modifiers added to the test groups C2, C3, and C4 were prepared using the formulations and preparation methods provided in Examples 1, 2, and 3, respectively. The relevant test results are as follows: Figure 2 And as shown in Table 6: Table 4. Cement paste viscosity ratio test mix proportions Performance testing of self-compacting concrete: The spread and water sensitivity of self-compacting concrete were tested according to the methods specified in GB / T 50080-2016; the early strength of self-compacting concrete was tested according to the methods specified in GB / T 50081-2019; and the crack resistance, chloride ion diffusion / migration coefficient, electrical flux, and freeze-thaw resistance of self-compacting concrete were tested according to the methods specified in GB / T 50082-2024. The mix proportions of the C40 and C60 self-compacting concrete reference groups are shown in groups D1 and E1 of Table 5, respectively. The viscosity modifiers incorporated into test groups D2, D3, D4, and E2 were prepared using the formulations and preparation methods provided in Examples 1, 2, and 3. The test results are as follows: Figure 3 , 4 And as shown in Table 6: Table 5. Test mix proportions of self-compacting concrete Table 6. Test results of cement paste viscosity and self-compacting concrete performance. The viscosity data of the cement paste show that the viscosity-modifying material of this invention has a clear and repeatable effect on the rheological regulation of the paste. Under the same water volume (145 mL), the viscosity of the baseline cement paste C1 is 878 cP; after incorporating the viscosity-modifying materials obtained in Examples 1, 2, and 3, the viscosities of C2, C3, and C4 increase to 1932, 1714, and 2327 cP, respectively, equivalent to approximately 220%, 195%, and 265% of the baseline. This indicates that the material, through the synergistic effect of aqueous phase thixotropic viscosity enhancement (hydration entanglement and structural recovery of sodium carboxymethyl cellulose) and the improvement of solid volume fraction / interfacial friction by the high specific surface area fine powder system, enables the paste to exhibit higher viscosity and stronger structural retention capacity on a macroscopic scale, thus providing a direct rheological basis for delaying segregation and bleeding. Applying this rheological regulation to the spreadability results of self-compacting concrete can further verify the process effect that "viscosity enhancement does not equal flow loss". With a D1 spread of 650 mm in the C40 baseline group, the D2, D3, and D4 spreads after incorporating viscosity modifiers 1, 2, and 3 were 660, 630, and 650 mm, respectively. Overall, these spreads remained within the high spread range suitable for filling self-compacting concrete, and no significant spread limitation due to viscosity enhancement was observed. Particularly noteworthy is that Example 3 (C4=2327 cP), with the highest paste viscosity, still maintained a concrete spread of 650 mm (D4), indicating that the viscosity-enhancing mechanism of this invention is more inclined towards "increasing viscosity / thixotropic recovery" rather than simply raising the yield threshold. This phenomenon is consistent with the dispersion and gradation effect of limestone powder in the formulation, the shear thinning / structural recovery characteristics of cellulose ether, and the microscopic reversible network formed by modified carbon nanotubes and modified tungsten disulfide: it partially offsets the increase in yield stress during the high-shear flow stage, keeping the mixture fluid, but recovers cohesiveness more quickly during the static stage, thus balancing filling performance and anti-segregation stability.

[0029] The strength data further demonstrates that this invention does not "trade stability for increased viscosity," but rather achieves a simultaneous improvement in stability and early / long-term strength, with a significant increase. In the C40 system, the 3d / 7d / 28d compressive strength of the baseline D1 is 32.9 / 37.7 / 45.9 MPa; after the addition of the material, D2 increases to 45.4 / 61.5 / 69.3 MPa, D3 increases to 48.2 / 66.3 / 72.1 MPa, and D4 increases to 40.1 / 56.2 / 65.3 MPa. In the C60 system, E1 is 48.5 / 64.5 / 74.7 MPa, and E2 increases to 54.3 / 70.9 / 80.0 MPa. Crucially, in this experimental mix design, the viscosity-modified material replaced a portion of the cement in equal amounts while maintaining the total powder content unchanged, yet the overall strength increased. This strength gain can be attributed to improved system reaction and microstructure efficiency: the pozzolanic reaction and nucleation effect of metakaolin, slag powder, and nano-silica fume promoted early gel formation and accelerated structural development; more importantly, the modified carbon nanotubes, in a dispersed state without significant agglomeration or fracture, provided microcrack bridging and stress transfer pathways, making it difficult for early defects to develop into through cracks; the modified tungsten disulfide, after activation-silanization-polycarboxylate treatment, could be stably dispersed, playing a role in lamellar hindrance and interface densification, reducing the weakness of the interface transition zone and inhibiting microcrack penetration. The combination of these three factors resulted in higher strength and more stable strength development under the same water content, and even with lower cement content.

[0030] The differences between the different embodiments also have clear formulation implications. The D3 corresponding to Example 2 has the highest strength in the C40 system (3d 48.2, 7d 66.3, 28d 72.1 MPa), while the spread is slightly lower (630 mm) and the water sensitivity index is the lowest (15 kg / m³). Its formulation characteristics are a higher proportion of kaolin and slag powder and a lower proportion of fly ash, which is more conducive to the early reaction rate and gel formation, resulting in higher early strength and lower transport channel connectivity. However, the reaction and adsorption effect of fine powder may make the workings relatively "tight", which is reflected in a slight decrease in spread. Example 3 corresponds to D4 paste with the highest viscosity (C4=2327 cP) and a spread of 650 mm, but the strength improvement is slightly weaker than that of D2 / D3. Considering its higher proportion of fly ash and zeolite powder and lower proportion of kaolin, it can be explained that it is more inclined to improve viscosity stability through adsorption and structure building, while the relatively lower proportion of reactive components makes the "early strength drive" weaker than that of Example 2. This also explains why "the highest viscosity does not necessarily correspond to the highest strength", because viscosity mainly reflects the fresh mix structure network and water film state, while strength depends more on the quantity and distribution of hydration / secondary reaction products, the degree of ITZ densification, and whether microcracks are connected.

[0031] The water sensitivity and shrinkage results reflect a mutually reinforcing relationship between the formulation components of this invention in terms of "stability—volume stability—interfacial defect control". The baseline D1 shrinkage is 362 × 10⁻⁶. -6 D2, D3, and D4 are respectively 30, 52, 22×10 -6 The C60 system also evolved from the E1's 420×10 -6 Reduced to E2 12×10 -6 The shrinkage decreased significantly from a positive value and even turned into micro-expansion, indicating that functional component B (R-type magnesium oxide + calcium expansion agent) achieved effective and more uniform volume compensation in the system. This compensation did not occur in isolation, but was coupled with the "lower bleeding / fewer stratified weak areas" brought about by the increase in viscosity. The more homogeneous mixture means that the expansion reaction is more consistent with the constraint conditions, and the compensation is more likely to be uniformly applied on the volume scale, thereby reducing local tensile stress concentration and early microcrack initiation. The water sensitivity data (D2=24, D3=15, D4=30 kg / m³; E2=24 kg / m³) also showed the same trend: Example 2 had the lowest sensitivity while maintaining high strength, which usually means that the system's rheological response to water fluctuations is more "passivated". This is related to its faster formation of highly active fine powder and microstructure, and the more robust water film / particle network formed by cellulose ether and multi-scale powder. The higher sensitivity of Example 3 (30) is consistent with its stronger viscosity (C4 is the highest) and the higher proportion of fly ash and zeolite powder, which makes it more sensitive to changes in adsorption and water film requirements.

[0032] The improvement in durability indicators shows a high degree of consistency with strength and shrinkage control, thus supporting the existence of a mechanism of "pore structure densification + crack channel reduction + interface homogenization" in this invention from a data perspective. Taking the C40 system as an example, the 28d RCM coefficient increased from 8.4 × 10⁻⁶ for D1. - ¹² m² / s decreased to 4.2 for D2, 3.6 for D3, and 4.4 × 10⁻⁶ for D4. - The current density was reduced by approximately 48%–57% to 1226 m² / s; the electric flux decreased from 2375 C to 1575, 1226, and 1830 C, with Example 2 (D3) showing the largest reduction. The C60 system showed even more significant improvement, with the electric flux decreasing from 1684 C to 614 C (E2) and the RCM decreasing from 4.0 to 2.4 × 10⁻⁶ m² / s. -¹² m² / s. Such improvements can generally be attributed to: the secondary reaction of slag powder and metakaolin reducing the proportion of interconnected pores; the micro-filling and nucleation of nano-silica fume promoting more uniform gel deposition; modified carbon nanotubes and modified tungsten disulfide inhibiting microcrack propagation and enhancing ITZ compaction; and volume compensation reducing the number of early microcracks induced by self-shrinkage. When microcracks and weak interfacial zones are reduced, the "fast channels" for chloride ion migration are weakened, achieving a simultaneous decrease in diffusion / migration coefficients and electrical flux even if the spread remains high. Among the different embodiments, Example 2 (D3) generally exhibits the best strength and durability (RCM, electrical flux), which, along with its higher proportion of reactive components and lower shrinkage, points to the combined advantage of "faster and more complete structural compaction + fewer crack channels." Example 3 (D4) maintains improved durability while significantly increasing viscosity, but its strength and electrical flux improvements are slightly weaker, consistent with its relatively low reactive component ratio, higher fly ash ratio, and milder early reaction structural evolution characteristics.

[0033] The freeze-thaw resistance results show that while significantly improving strength and impermeability, this invention does not adversely affect freeze-thaw durability and maintains a high level of stability in the data. In the C40 system, the mass loss rate after 300 freeze-thaw cycles is no higher than 0.4%, and the relative dynamic elastic modulus remains between 99% and 100%. In the C60 system, the E1 and E2 mass loss rates are 0.2% and 0.1%, respectively, and the relative dynamic elastic modulus is 100% for both. In high-powder, high-viscosity systems, freeze-thaw risks often stem from instability of the gas-containing system or unreasonable pore structure. However, this invention, through the synergy of a non-ionic air-entraining agent and system dispersion / viscosity control, makes the gas-containing structure easier to maintain. Simultaneously, densification and crack suppression reduce the risk of moisture migration and local saturation fluctuations. Therefore, it can improve durability such as resistance to chloride ion penetration while maintaining freeze-thaw performance without deterioration.

[0034] Based on the above data and comparative relationships, it can be concluded that the key effect of this invention is not "single viscosity enhancement," but rather a repeatable synergistic system formed through the thixotropic regulation of cellulose ether, the construction of multi-scale fine powders, the balancing effect of limestone powder on yielding and dispersion, the micro-nano reinforcement and interface densification of nano-silica fume-modified carbon nanotubes-modified tungsten disulfide, and the volume compensation of MgO / calcareous expanding agent. This system significantly improves slurry viscosity, enhances homogeneity, and simultaneously increases early strength, reduces shrinkage, significantly improves RCM and electrical flux, while maintaining stable freeze-thaw performance, all while maintaining self-compacting expansion.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A viscosity-modifying material that maintains the homogeneity of self-compacting concrete, characterized in that, The components, by weight, are as follows: 20-30 parts fly ash, 18-22 parts slag powder, 15-25 parts metakaolin, 0.1-0.3 parts cellulose ether, 11-18 parts limestone powder, 8-11 parts zeolite powder, 0.1-0.3 parts air-entraining agent, 5-8 parts functional component A, and 3-10 parts functional component B.

2. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 1, characterized in that, The functional component A is a mixture of nano-silica fume, modified carbon nanotubes, and modified tungsten disulfide in a mass ratio of 3-4:1-2:1-2.

3. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 2, characterized in that, The functional component A is prepared through the following steps: S11. Preparation of modified carbon nanotubes: Sodium dodecylbenzenesulfonate and anhydrous ethanol (dehydrated by 3 Å molecular sieve for 24-28 h) were weighed at a mass ratio of 0.006-0.01:10-15, respectively. The sodium dodecylbenzenesulfonate was dissolved in anhydrous ethanol to form a dispersion. The weighed carbon nanotubes were added to the dispersion, and the carbon nanotube dispersion was modified using a probe-type ultrasonic processor with an ultrasonic power of 400-450 W and an ultrasonic time of 25-45 min to obtain a modified carbon nanotube-anhydrous ethanol dispersion. S12. Preparation of modified tungsten disulfide: S121. Weigh tungsten disulfide powder and deionized water at a mass ratio of 0.005-0.02:10-15. Add the tungsten disulfide powder to the deionized water and stir mechanically for 5-10 min. Then add hydrogen peroxide solution and control the concentration of hydrogen peroxide in the system to be 0.5-2.0 wt%. Stir the reaction at 25-40℃ for 30-40 min. Centrifuge, wash, resuspend in anhydrous ethanol and centrifuge 2-3 times to obtain tungsten disulfide-ethanol wet slurry. S122. Mix ethanol and deionized water at a mass ratio of 80-85:20-25, adjust the pH to 4-5 with glacial acetic acid, stir for 15-30 min, add tungsten disulfide-ethanol wet slurry and silane coupling agent, stir and react at 40-60℃ for 1-3 h, centrifuge and wash to obtain silanized tungsten disulfide-ethanol wet slurry. S123. The silanized tungsten disulfide-ethanol wet slurry is resuspended in anhydrous ethanol to form a stirable slurry. Polycarboxylate superplasticizer is added and stirred for 30-60 min to obtain a modified tungsten disulfide-anhydrous ethanol dispersion. S13. Pre-dispersion of nano silica fume: Add the weighed nano silica fume to dehydrated anhydrous ethanol and stir mechanically for 5-10 minutes to form a pre-dispersion slurry of nano silica fume; S14. Preparation of functional material A: The modified tungsten disulfide-anhydrous ethanol dispersion and the modified carbon nanotube-anhydrous ethanol dispersion are mixed and mechanically stirred for 5-10 min for premixing. The nano silica fume pre-dispersion slurry is then added and ultrasonicated at 400-450W power for 35-40 min to obtain silica fume-modified carbon nanotube-modified tungsten disulfide dispersion. The dispersion is then placed in a slightly vacuum forced-air drying oven and dried at 65-70℃ for 1-2 h, and then dried at 75-85℃ for 2-3 h to obtain functional material A.

4. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 3, characterized in that, In step S122, the mass ratio of the tungsten disulfide-ethanol wet slurry to the silane coupling agent is 1:1-4; in step S123, the mass ratio of the polycarboxylate superplasticizer to the silanized tungsten disulfide-ethanol wet slurry is 1-6:1; in step S14, the vacuum degree of the forced-air drying oven is -0.02~-0.05MPa.

5. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 1, characterized in that, The functional component B is a mixture of magnesium oxide and calcium expansion agent in a mass ratio of 1-2.5:3-5.

6. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 5, characterized in that, The functional component B is prepared by the following method: Magnesium oxide and calcium expansion agent were weighed separately according to their mass fractions and mixed evenly using a continuously variable speed shear mixer to obtain the functional component B. The continuously variable speed shear mixer had an angular velocity and rotational speed of 1000-1200 r / min and a linear velocity of 10-15 m / s, thereby utilizing the generated high-speed shear mixing force to achieve uniform mixing of powder particles and minimize damage to the original structure of the raw materials.

7. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 1, characterized in that, The fly ash has an average particle size of <5μm, a maximum particle size of <20μm, and a density of <2.6g / cm³. 3 The loss on ignition is less than 1.5%; the average particle size of the slag powder is <5μm, the maximum particle size is <20μm, and the density is ≥2.88g / cm³. 3 Specific surface area ≥ 420m² 2 / kg; the average particle size of the metakaolin is <3μm, and the maximum particle size is <8μm; the calcium carbonate content of the limestone powder is ≥85%, the methylene blue value is ≤0.5g / kg, and the fineness range is 800-1250 mesh.

8. The viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to claim 1, characterized in that, The cellulose ether is further specified as sodium carboxymethyl cellulose, with a pH range of 5-9 and a viscosity of 300-600 mPa·S; the air-entraining agent is further specified as a saponin-based air-entraining agent.

9. A method for preparing a viscosity-modified material that maintains the homogeneity of self-compacting concrete, used to prepare the viscosity-modified material that maintains the homogeneity of self-compacting concrete as described in any one of claims 1-8, characterized in that, Includes the following steps: Fly ash, slag powder, metakaolin, cellulose ether, limestone powder, zeolite powder, air-entraining agent, functional component A, and functional component B are weighed out according to their respective mass proportions. They are then mixed evenly using a continuously variable speed shear mixer to obtain the viscosity-modified material that maintains the homogeneity of self-compacting concrete. The continuously variable speed shear mixer has an angular velocity and rotational speed of 1000-1200 r / min and a linear velocity of 10-15 m / s.

10. The application of a viscosity-modifying material for maintaining the homogeneity of self-compacting concrete according to any one of claims 1-8 in the field of concrete preparation.

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