Ultra-dispersed high-activity silicon mortar, preparation method and application thereof, and component

Abstract

The invention relates to the technical field of concrete admixtures, in particular to ultra-dispersed high-activity silica mortar, a preparation method and application thereof and a component, the ultra-dispersed high-activity silica mortar comprises silica mortar, the silica mortar contains polyelectrolyte, and the pH value of the silica mortar is 8-13; the polyelectrolyte is a linear carboxylic acid polymer and a salt thereof. The pH value of the silica fume slurry is adjusted to 8-13, and the dispersion effect of the polyelectrolyte containing carboxylic acid groups is combined, so that the charge property of the surfaces of silica fume particles is changed, the absolute value of the ZETA potential is increased, the highest absolute value of the ZETA potential can reach 50 mV or above, the strong negative electricity on the surfaces of the silica fume particles enables the particles to generate the electrostatic repulsion effect, and the particles are prevented from being damaged. The silicon ash particles can be effectively prevented from getting close to each other and being agglomerated by matching with the steric hindrance of the polyelectrolyte containing the carboxylic acid group, so that the dispersity of the silicon ash slurry is further improved, the dispersion stability is good, and the suspension rate in 30 days is basically 99.5% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and specifically relates to a super-dispersed high-activity silica fume slurry, its preparation method, application, and components. Background Art

[0002] In the field of modern concrete technology, silica fume, as an important mineral admixture, has many significant benefits for concrete properties. Silica fume has extremely high pozzolanic activity, and its main component is amorphous silica, which can undergo a secondary hydration reaction with calcium hydroxide generated by cement hydration to form additional calcium silicate hydrate products, thereby significantly enhancing the strength of concrete, including early strength and late strength development. At the same time, it can also effectively improve the durability of concrete, such as enhancing impermeability, resistance to chloride ion erosion, and resistance to chemical erosion, etc.

[0003] However, silica fume faces severe challenges during direct application. Silica fume particles are extremely fine, and their average particle size is usually in the nanometer range, which gives silica fume a large specific surface area and high surface energy, and thus easily causes agglomeration in the concrete mixture. Once agglomerated, silica fume is difficult to be evenly dispersed in the concrete matrix, not only unable to fully exert its positive effect on concrete properties, but also having a serious negative impact on the workability of concrete, such as significantly increasing the viscosity of the concrete mixture, reducing its fluidity and plasticity, bringing great difficulties to the construction processes of concrete mixing, transportation, pouring, and vibration, increasing construction costs and possibly affecting construction quality.

[0004] To overcome the drawbacks of direct application of silica fume, preparing silica fume into a silica fume slurry is an effective improvement approach. The silica fume slurry can, to a certain extent, improve the dispersion state of silica fume, making it easier to mix with other components in the concrete. However, the existing silica fume slurry preparation technology still has obvious deficiencies, its dispersion ability is relatively limited, it is difficult to make the silica fume particles reach an ideal dispersion degree, and the potential performance advantages of silica fume in concrete cannot be fully exploited.

[0005] Therefore, there is an urgent need to develop new dispersion technologies to further improve the dispersion of silica fume in the silica fume slurry, so as to better utilize silica fume to improve the comprehensive properties of concrete, meet the growing demand of modern concrete projects for high-performance and high-quality building materials, and promote the continuous development and innovative application of concrete technology in many fields such as construction, transportation, and water conservancy. Summary of the Invention

[0006] The purpose of the present invention is to provide a super-dispersed high-activity silica fume slurry to increase the absolute value of ZETA and the activity index of the silica fume slurry, thereby achieving the super-dispersion and stability of the silica fume slurry.

[0007] In addition, the present invention also provides a preparation method and an application of the above-mentioned super-dispersed highly active silica mortar, as well as a component containing the super-dispersed highly active silica mortar.

[0008] The present invention is achieved through the following technical solutions: A super-dispersed highly active silica mortar, including silica mortar, the silica mortar contains a polyelectrolyte, and the pH value of the silica mortar is 8-13; the polyelectrolyte is a linear carboxylic acid polymer and its salt.

[0009] The silica mortar of the present invention refers to conventional silica mortar, which directly disperses silica fume in water. However, the silica mortar prepared in this way has a relatively limited dispersion ability of silica fume in the system, and it is difficult to achieve an ideal dispersion degree of silica fume particles.

[0010] The original intention of the present invention is to improve the existing silica mortar to enhance the dispersion effect of silica fume in the silica mortar. There are mainly two points for the present invention to improve the dispersion effect of silica fume in the silica mortar: First, the present invention adjusts the pH value of the silica mortar to 8-13. The alkaline environment is the basis for realizing the dispersion of silica fume. The alkaline environment ionizes the silanol groups (Si-OH) on the surface of silica fume particles into SiO - , making the surface of silica fume particles carry negative charges. The generation of this charge creates conditions for the subsequent electrostatic repulsion.

[0011] Secondly, as Figure 2 shown, the present invention adds a polyelectrolyte to the silica mortar. The polyelectrolyte contains carboxylic acid groups. The polyelectrolyte adsorbs on the surface of silica fume particles through its carboxylic acid groups, making the surface of silica fume particles carry negative charges. According to the principle of electrostatics, electrostatic repulsion will occur between silica fume particles with the same negative charges. This repulsion can prevent silica fume particles from approaching and aggregating with each other, so that silica fume particles remain dispersed in the system; at the same time, the polyelectrolyte forms a thick steric hindrance layer on the surface of silica fume particles. When two silica fume particles approach each other, the molecular chains of the polyelectrolyte adsorbed on their surfaces will be squeezed against each other, generating a repulsive force. This steric hindrance effect further prevents the direct contact and agglomeration of silica fume particles, enabling silica fume particles to be stably dispersed in the system. Even when silica fume particles tend to approach due to Brownian motion and other reasons, the steric hindrance layer can effectively prevent their agglomeration.

[0012] Moreover, the silica mortar of the present invention is in an alkaline environment, and the alkaline environment is also beneficial for the polyelectrolyte of the present invention to exert its dispersion effect.

[0013] In summary, in the present invention, by adjusting the pH value of the silica fume mortar to 8-13 and adding a polyelectrolyte containing carboxylic acid groups to the silica fume mortar, the surface of the silica fume in the silica fume mortar is negatively charged, so that electrostatic repulsion is generated between the silica fume particles. At the same time, combined with the steric hindrance of the polyelectrolyte, the agglomeration of the silica fume particles can be effectively reduced, the dispersibility of the silica fume in the silica fume mortar is improved, and the dispersion stability is good.

[0014] The super-dispersion of the present invention means that through a specific modification process, the agglomerated particle system in the densified silica fume is depolymerized, and the silica fume particles are dispersed to the state of a single silica fume particle size, forming a uniform and stable dispersion system (uniform and stable generally means that the suspension rate is greater than 90%), realizing super-dispersion; high activity means that the activity index of the mortar prepared from the dispersed silica fume is higher than that of the mortar prepared from the undispersed highly densified silica fume. Specifically, generally, when the activity index of the silica fume mortar is greater than 130%, it can be considered to have high activity.

[0015] Among them, the linear carboxylic acid-based polymer includes at least one of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, carboxylic acid-sulfonate copolymer, hydrolyzed polymaleic anhydride, maleic acid-acrylic acid copolymer / mixture, polyacrylic acid, polymaleic acid, and polybutenoic acid.

[0016] Among them, the salts corresponding to the linear carboxylic acid-based polymer include polyacrylate, polymaleate, maleic acid-acrylic acid copolymer salt, and polybutenoate, etc. The salts of the linear carboxylic acid-based polymer include at least one of sodium salt and potassium salt, that is, the specific salt can be sodium salt or potassium salt. For example: polyacrylate includes at least one of sodium polyacrylate and potassium polyacrylate; polymaleate includes at least one of sodium polymaleate and potassium polymaleate.

[0017] In a preferred embodiment, the pH value of the silica fume mortar is adjusted to 8-13 by a monovalent ion base and / or a divalent ion base and / or a trivalent ion base.

[0018] The monovalent ion base of the present invention means that the cation formed by the base in the solution is a monovalent cation; the divalent ion base means that the cation formed by the base in the solution is a divalent cation; the trivalent ion base means that the cation formed by the base in the solution is a trivalent cation.

[0019] Theoretically, any base can be used to adjust the pH value of the system, and the base includes organic bases and inorganic bases. However, considering the dispersion problem of the silica fume mortar system of the present invention, when selecting a base to adjust the pH value, the basicity, solubility, precipitation tendency, and ion migration ability of the base need to be considered.

[0020] The monovalent base used in the present invention has strong basicity, high solubility, low precipitation tendency, and high ion migration ability; while the divalent base and trivalent base have lower solubility and are more likely to precipitate compared to the monovalent base, which is likely to cause flocculation and sedimentation of the mortar. Therefore, it is preferred to use a monovalent base.

[0021] In a preferred embodiment, the monovalent ion base includes at least one of sodium hydroxide, potassium hydroxide, ammonia, triethylamine and tetramethylammonium hydroxide; the divalent ion base includes magnesium hydroxide; and the trivalent ion base includes aluminum hydroxide.

[0022] In a preferred embodiment, the molecular weight of the polyelectrolyte is 1000 to 10000.

[0023] A molecular weight that is too low results in weak adsorption, insufficient steric hindrance, and poor dispersion stability; a molecular weight that is too high leads to difficulty in dissolution, excessive viscosity, and bridging flocculation and coagulation. Limiting the molecular weight to 1,000-10,000 achieves an optimal balance between electrostatic repulsion, steric hindrance, solution fluidity, and process feasibility, ensuring excellent dispersibility, workability, and long-term stability of the silica ash slurry.

[0024] In a preferred embodiment, the molecular weight of the polyelectrolyte is 3000 to 10000.

[0025] In a preferred embodiment, the amount of polyelectrolyte added is 0.05% to 2% based on the weight of silica fume in the silica fume slurry.

[0026] If the concentration of polyelectrolyte is too low, the dispersion effect will be insufficient; if it is too high, agglomeration will occur.

[0027] In a preferred embodiment, the amount of polyelectrolyte added is 0.1% to 0.5% based on the weight of silica fume in the silica fume slurry.

[0028] In a preferred embodiment, the pH value of the silica slurry is 8-11.

[0029] Silica ash system composition: mainly amorphous SiO2, small amounts of Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, etc. In a preferred embodiment, the silica ash slurry contains the following components: Na + OH - 、SiO3 2- / HSiO3 - and [PAA] - According to the use of base, also selectively including K + and / or (CH3)4N + and / or (C2H5)3NH + and / or NH4 + The alkali of the present invention is used to adjust the pH value of the silica ash slurry. When adjusting the pH value, any one or more of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and tetramethylammonium hydroxide can be selected and used in combination.

[0030] In a preferred embodiment, the solid content of the silica slurry is 20-75%.

[0031] A preparation method of a super-dispersed and highly active silica fume mortar, comprising the following steps: S1. Dissolve an alkali in water to form an alkaline solution; S2. Add a polyelectrolyte to the alkaline solution to obtain a mixed solution; S3. Gradually add silica fume to the mixed solution under stirring to obtain a super-dispersed and highly active silica fume mortar; When the alkali is an organic base, step S1 is selectively carried out. Selectively carrying out step S1 means that when the alkali is an organic base, it can be operated in the order of S1, S2, and S3 in the manner of an inorganic base, or the organic base and the polyelectrolyte can be added to water together.

[0032] It is found through experiments that: When adjusting the pH value of the silica fume mortar with an inorganic base, if the inorganic base is not dissolved in advance and the solid inorganic base is directly added during the preparation of the silica fume mortar, the silica fume mortar will quickly thicken and the super-dispersed effect cannot be achieved; when adjusting the pH value of the silica fume mortar with an organic base, this problem does not exist.

[0033] In a preferred mode, in step S3, after the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment, then left standing and filtered to obtain a super-dispersed and highly active silica fume mortar; the equipment for high-speed dispersion treatment includes a high-speed dispersion device, a homogenizer, a sand mill, a colloid mill or a ball mill.

[0034] The high-speed dispersion treatment of the present invention further strengthens the prepared silica fume mortar with good dispersion effect. Under the strong shear force generated by high-speed stirring or the action of ball milling, the aggregates between silica fume particles are broken. The originally aggregated large particles are decomposed into smaller particles, increasing the degree of particle dispersion. At the same time, high-speed dispersion enables the alkali, polyelectrolyte and silica fume particles to be more fully and evenly mixed. This ensures that the polyelectrolyte can be quickly and evenly adsorbed on the surface of silica fume particles, making the charge distribution on the particle surface more uniform and the steric hindrance layer more complete. Moreover, the high-speed dispersion or ball milling process can also remove impurities (such as gas etc.) adsorbed on the particle surface, further optimizing the dispersion state of the particles.

[0035] Generally speaking, the alkali adjusts the pH value to create a basic chemical environment for dispersion, the polyelectrolyte containing carboxylic acid groups plays a dispersion role through electrostatic repulsion and steric hindrance, and high-speed dispersion strengthens the dispersion effect. The three work together synergistically to effectively achieve the dispersion of silica fume.

[0036] An application of a super-dispersed and highly active silica fume mortar in the preparation of concrete, the concrete includes ordinary commercial concrete, sleeper concrete or UHPC concrete; among them, the sleeper concrete includes C70 dry-hard concrete, etc.

[0037] In a preferred embodiment, based on the weight of the cementitious materials in the concrete, the addition amount of silica fume slurry in ordinary commercial concrete and sleeper concrete is 3-10%; the addition amount of silica fume slurry in UHPC concrete is 1-16%.

[0038] A component is prepared by using concrete containing the above-mentioned hyper-dispersed highly reactive silica fume slurry.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects: By adjusting the pH value of the silica fume slurry to 8-13 and combining with the dispersion effect of the polyelectrolyte containing carboxylic acid groups, the charge property on the surface of the silica fume particles is changed, the absolute value of the ZETA potential increases, and the absolute value of the ZETA potential can reach more than 50 mV at most. The strong negative charge on the surface of the silica fume particles causes electrostatic repulsion between the particles. Combining with the steric hindrance of the polyelectrolyte containing carboxylic acid groups, it can effectively prevent the silica fume particles from approaching and aggregating each other, thereby improving the dispersion of the silica fume slurry, and the dispersion stability is good. The suspension rate is basically above 99.5% in 30 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings: Figure 1 It is a comparison picture of the silica fume slurry prepared in Example 1 of the present invention and ordinary silica fume slurry; Figure 2 It is a schematic diagram of the hyper-dispersion of the silica fume slurry of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention. The following described embodiments are part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0042] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that: the present invention does not have to adopt these specific details. In other embodiments, in order to avoid obscuring the present invention, well-known structures, materials or methods are not specifically described. The materials, instruments and reagents used in the following embodiments can be obtained from commercial sources without special instructions. The technical means used in the embodiments are all conventional means well-known to those skilled in the art without special instructions.

[0043] In order to solve the problem that the dispersion effect of the existing silica fume mortar is not good and needs to be further improved, this embodiment provides a super-dispersed high-activity silica fume mortar, its preparation method and application.

[0044] The super-dispersed high-activity silica fume mortar includes silica fume mortar. The silica fume mortar contains polyelectrolyte, and the pH value of the silica fume mortar is 8-13; the polyelectrolyte contains carboxylic acid groups, linear carboxylic acid-based polymers and their salts.

[0045] Specifically, the linear carboxylic acid-based polymer includes at least one of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, carboxylic acid-sulfonate copolymer, hydrolyzed polymaleic anhydride, maleic acid-acrylic acid copolymer / mixture, polyacrylic acid, polymaleic acid and polybutenoic acid.

[0046] Among them, the salts corresponding to the linear carboxylic acid-based polymers include polyacrylate salts, polymaleate salts, maleic acid-acrylic acid copolymer salts and polybutenoate salts, etc. The salts of the linear carboxylic acid-based polymers include at least one of sodium salt and potassium salt, that is, the specific salt can be sodium salt or potassium salt. For example: polyacrylate salts include at least one of sodium polyacrylate and potassium polyacrylate; polymaleate salts include at least one of sodium polymaleate and potassium polymaleate.

[0047] The above-mentioned polyelectrolytes are all linear macromolecular electrolytes, with significant steric hindrance of the molecular chain length, high charge density, one carboxyl group per unit; excellent water solubility in alkaline environment; strong adsorption stability. Therefore, the above-mentioned polyelectrolytes (such as acrylate salts and polymaleate salts) have higher activity and higher absolute value of ZETA potential compared with other electrolytes (such as polycarboxylic acids, naphthalene series, melamine, etc.).

[0048] The alkaline environment ionizes the silanol groups (Si-OH) on the surface of the silica fume particles into SiO - , making the particle surface carry a negative charge; the polyelectrolyte adsorbs on the surface of the silica fume particles through its carboxylic acid groups, making the surface of the silica fume particles carry a negative charge, changing the charge property of the surface of the ash particles, increasing the absolute value of the ZETA potential, and the strong negative charge on the surface of the silica fume particles generates an electrostatic repulsion effect, which can effectively prevent the silica fume particles from approaching and agglomerating each other; at the same time, the polyelectrolyte forms a thick steric hindrance layer on the surface of the silica fume particles, further reducing the agglomeration of the silica fume in the silica fume mortar.

[0049] In a preferred embodiment, the pH value of the silica ash slurry is adjusted to 8-13 by using a monovalent ion base and / or a divalent ion base and / or a trivalent ion base, preferably a monovalent ion base. The monovalent ion base includes at least one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and tetramethylammonium hydroxide; the divalent ion base includes magnesium hydroxide; and the trivalent ion base includes aluminum hydroxide. The monovalent ion base of this embodiment can both adjust the pH value of the silica ash slurry and avoid affecting its dispersibility. In a preferred embodiment, the molecular weight of the polyelectrolyte is 1000 to 10000. More preferably, the molecular weight of the polyelectrolyte is 3000 to 10000.

[0050] In a preferred embodiment, the amount of the polyelectrolyte added is 0.05% to 2% by weight of the silica fume in the silica fume slurry. More preferably, the amount of the polyelectrolyte added is 0.1% to 0.5% by weight of the silica fume in the silica fume slurry.

[0051] In a preferred embodiment, the pH value of the silica slurry is 8-11.

[0052] The super-dispersed high-activity silica mortar of this embodiment contains the following components: Na + OH - 、SiO3 2- / HSiO3 - and [PAA] - According to the use of base, also selectively including K + and / or (CH3)4N + and / or (C2H5)3NH + and / or NH4 + .

[0053] The solid content of silica ash slurry is 20-75%. Solid content refers to the mass percentage of silica ash in silica ash slurry.

[0054] The preparation method of the super-dispersed high-activity silica slurry of this embodiment comprises the following steps: S1. Dissolve the alkali in water to form an alkaline solution: Add the weighed pH adjuster (base) to a certain amount of water and stir with a high-speed stirrer for at least 2 minutes to ensure that the base is completely dissolved to form a uniform alkaline solution; The amount of alkali used is determined based on the pH value of the silica fume itself, the expected performance of the silica fume slurry and the amount of silica fume used, and generally accounts for 0.3% to 7% of the mass of the silica fume.

[0055] S2. Add a polyelectrolyte to the alkaline solution to obtain a mixed solution; during the addition of the polyelectrolyte, keep stirring for at least 1 min to fully disperse the polyelectrolyte in the alkaline solution and form a stable mixed solution.

[0056] S3. Gradually add silica fume to the mixed solution under stirring to obtain a super-dispersed highly active silica fume slurry; the addition amount of silica fume is determined according to the required concentration of the silica fume slurry, generally accounting for 20% - 75% of the total mass of the silica fume slurry.

[0057] When the base is an organic base, step S1 is selectively carried out.

[0058] When adjusting the pH value of the silica fume slurry with an inorganic base, if the inorganic base is not dissolved in advance and solid inorganic base is directly added during the preparation of the silica fume slurry, the silica fume slurry will quickly thicken and the super-dispersed effect cannot be achieved; when adjusting the pH value of the silica fume slurry with an organic base, this problem does not exist.

[0059] In a preferred case, in step S3, after the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment for 10 - 30 min, then left standing and filtered to obtain a super-dispersed highly active silica fume slurry; the equipment for high-speed dispersion treatment includes high-speed dispersion equipment, homogenizer, sand mill, colloid mill or ball mill.

[0060] The combination of high-speed dispersion treatment and the subsequent filtration can further improve the quality of the silica fume slurry. The powerful shear force generated by high-speed dispersion quickly disperses the silica fume particles, and filtration removes large particle impurities. The finally obtained silica fume slurry has super-dispersibility, high stability and high activity, and can be widely used in building materials such as concrete and mortar, significantly improving their properties such as strength, durability and impermeability.

[0061] Moreover, the preparation method of this embodiment has clear steps, wide adaptability, simple operation and is easy to industrialize, and can be widely promoted and applied in the field of building material production.

[0062] The above super-dispersed highly active silica fume slurry can be used in the production of concrete, and the concrete includes ordinary commercial concrete, sleeper concrete or UHPC concrete. Among them, the sleeper concrete includes C70 dry-hard concrete, etc. The concrete can be used to prepare components, and the components include precast components and cast-in-place components, etc.

[0063] Specifically, based on the weight of the cementitious materials in the concrete, the addition amount of the silica fume slurry in ordinary commercial concrete and sleeper concrete is 3 - 10%; the addition amount of the silica fume slurry in UHPC concrete is 1 - 16%.

[0064] To better illustrate the technical effects of this embodiment, the following specific cases are used for illustration.

[0065] For the detection techniques of linear carboxylic acid polymers (such as sodium polyacrylate, ammonium polyacrylate, etc.) in silica fume mortar in this embodiment, combining qualitative identification and quantitative analysis, it covers conventional laboratory methods and instrumental analysis.

[0066] I. Qualitative identification method: Detection of functional groups and structural characteristics 1. Fourier transform infrared spectroscopy (FTIR) Principle: Confirm the presence of the polymer by detecting the characteristic absorption peaks of carboxylic acid groups (-COOH / -COO - )

[0067] Operation steps: Sample pretreatment: Centrifuge the silica fume mortar (10000 rpm, 15 min) to take the supernatant, and freeze-dry or spray-dry to obtain a solid powder.

[0068] Test conditions: KBr tablet, scanning range 4000 - 400 cm -1 , resolution 4 cm -1 , scanning times 32 times.

[0069] Characteristic peak reference: 1700 - 1720 cm -1 (carbonyl stretching vibration of free - COOH); 1550 - 1600 cm -1 (-COO - antisymmetric stretching vibration, sodium salt characteristic); 2920 - 2960 cm -1 (alkyl chain C-H stretching vibration).

[0070] 2. Proton nuclear magnetic resonance spectroscopy ( 1 ¹H-NMR) Principle: Confirm the structure by the chemical shift of hydrogen atoms in the polymer backbone.

[0071] Sample preparation: Dissolve the supernatant with D2O and filter through a 0.45 μm filter membrane.

[0072] Characteristic shift: δ = 2.4 - 2.6 ppm (acrylic unit -CH2- proton); δ = 1.8 - 2.0 ppm (terminal methyl proton, if there is a capping agent); Advantage: Can distinguish linear and branched structures (the peak broadening of the branched structure is more obvious).

[0073] II. Quantitative analysis method: Content and molecular weight characterization 1. High performance liquid chromatography (HPLC) Principle: Quantify by the retention behavior of the polymer in the reversed-phase chromatographic column.

[0074] Chromatographic conditions: Chromatographic column: C18 column (250 mm × 4.6 mm, 5 μm); Mobile phase: 0.1% phosphoric acid aqueous solution - methanol (volume ratio 90:10); Flow rate: 1.0 mL / min, Column temperature 30 °C, UV detection wavelength 210 nm.

[0075] Standard curve: Prepare a series of solutions (10 - 100 mg / L) with a known concentration of sodium polyacrylate standard (molecular weight 5000 - 10000 Da), and establish the relationship between concentration and peak area.

[0076] Sample treatment: Dilute the supernatant 10 times, and inject the sample after passing through a 0.22 μm filter membrane.

[0077] 2. Gel Permeation Chromatography (GPC) Principle: Separate according to the molecular volume of the polymer, and determine the molecular weight and distribution (auxiliary quantification).

[0078] Condition settings: Chromatographic column: TSK-GEL G3000PWXL (300 mm × 7.8 mm); Mobile phase: 0.1 mol / L NaNO3 aqueous solution, Flow rate 1.0 mL / min.

[0079] Detector: Differential refractive index detector (RI) + Ultraviolet detector (UV).

[0080] Quantification basis: Draw a molecular weight - retention time curve with standard sodium polyacrylate (Mw = 5000, 10000, 50000 Da), and calculate the sample concentration by peak area integration.

[0081] 3. Acid-base titration method (semi-quantitative) Principle: Determine the total acid amount through the neutralization reaction of carboxylic acid groups.

[0082] Operation steps: Take 10 mL of the supernatant, add 2 drops of phenolphthalein indicator; Titrate with 0.1 mol / L NaOH standard solution until it turns slightly red (pH ≈ 8.2), and record the consumption volume V; Calculation formula: Polymer content (g / L) = (c(NaOH) * V * M) / 10; where M is the average molar mass of the polymer, assuming it is sodium polyacrylate, M ≈ 72n, n is the degree of polymerization, and usually the average value 7000 g / mol is taken.

[0083] Precautions: It is necessary to exclude the interference of other acidic substances such as citric acid (it can be confirmed by FTIR that there are no interference peaks first).

[0084] III. Special scenario detection: Desorption and analysis of adsorbed polymers. If the polymer is adsorbed on the surface of silica fume particles, it needs to be desorbed first and then detected 1. Desorption method pH adjustment method: Add 0.1 mol / L HCl to the silica fume slurry to adjust the pH to 2, and perform ultrasonic treatment (300 W, 15 min) to protonate and shed the polymer. Then, use 0.1 mol / L NaOH to adjust the pH back to 7, and centrifuge to obtain the supernatant.

[0085] Ion exchange method: Add an excessive amount of NaCl (0.5 mol / L), and the polymer is desorbed through Na + competitive adsorption.

[0086] 2. Coupling techniques FTIR-ATR (attenuated total reflection): Directly detect the polymer adsorbed on the surface of silica fume particles without desorption, and semi-quantify the adsorption amount through the peak intensity at 1550 cm -1 .

[0087] Thermogravimetric analysis (TGA): Heat the silica fume sample to 800 °C at a rate of 10 °C / min in an N2 atmosphere, and the proportion of weight loss due to polymer decomposition (in the range of 600 - 700 °C) is the adsorption amount (other organic matters need to be deducted).

[0088] Example 1: The super-dispersed highly active silica fume slurry includes silica fume slurry. The solid content of the silica fume slurry is 50%, that is, the mass ratio of silica fume to water is 1:1. Based on the weight of silica fume in the silica fume slurry, 0.1% of sodium polyacrylate (molecular weight: 3000) and 0.15% of sodium hydroxide are added to the silica fume slurry, and the pH value of the silica fume slurry is 8.9.

[0089] The preparation method of the super-dispersed highly active silica fume slurry in this example includes the following steps: S1. Dissolve the alkali in water to form an alkaline solution: Add the weighed sodium hydroxide to a certain amount of water. The specific amount of water is determined according to the solid content of 50% and the amount of silica fume. At the same time, use a high-speed stirrer to stir for 2 min to ensure that the sodium hydroxide is completely dissolved to form a uniform alkaline solution; S2. Add sodium polyacrylate to the alkaline solution to obtain a mixed solution; keep stirring during the addition of sodium polyacrylate for 1 min to fully disperse sodium polyacrylate in the alkaline solution to form a stable mixed solution.

[0090] S3. Gradually add silica fume to the mixed solution under stirring to obtain a super-dispersed highly active silica fume slurry; the addition rate of silica fume is 5 kg / min to avoid agglomeration caused by too fast addition; S4. After the addition of silica fume is completed, perform high-speed dispersion treatment (1500 r / min) on the mixed system for 10 min, then let it stand and filter to obtain the super-dispersed highly active silica fume slurry.

[0091] In order to verify the difference in dispersion effect of adjusting the pH value of silica slurry with different monovalent ion bases, the following Examples 2 to 5 were carried out.

[0092] The silica slurry prepared in this embodiment contains the following components: OH - 、Na + 、 SiO3 2- , H2O, polyacrylate ion [PAA] - .

[0093] The comparison between the silica mortar prepared in this embodiment and the ordinary silica mortar is shown in the figure below. Figure 1 As shown, Depend on Figure 1 It can be seen that the silica ash slurry prepared in this embodiment does not stick to the wall and has better fluidity than ordinary silica ash slurry.

[0094] Example 2: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: Based on the weight of silica fume in silica fume slurry, 0.25% potassium hydroxide was used to adjust the pH value of silica fume slurry to 8.8. The silica slurry prepared in this embodiment contains the following components: OH - 、Na + , K + 、SiO3 2- , H2O, polyacrylate ion [PAA] - .

[0095] Example 3: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The pH value of the silica ash slurry was adjusted to 9.0 using 0.3% tetramethylammonium hydroxide based on the weight of the silica ash in the silica ash slurry.

[0096] The silica slurry prepared in this embodiment contains the following components: OH - 、Na + 、 SiO3 2- , H2O, polyacrylate ion [PAA] - 、(CH3)4N + .

[0097] Example 4: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The pH value of the silica ash slurry was adjusted to 8.9 using 0.4% triethylammonium based on the weight of the silica ash in the silica ash slurry.

[0098] The silica fume mortar prepared in this example contains the following components: OH - , Na + , SiO3 2- , H2O, polyacrylate ion [PAA] - , (C2H5)3NH + .

[0099] Example 5: This example is based on Example 1, and the difference from Example 1 is that: Based on the weight of silica fume in the silica fume mortar, 0.5% ammonia water is used to adjust the pH value of the silica fume mortar to 9.0.

[0100] The silica fume mortar prepared in this example contains the following components: OH - , Na + , SiO3 2- , H2O, polyacrylate ion [PAA] - , NH4 + .

[0101] The D50, ZETA value, activity index and 30-day suspension rate of the silica fume mortar in Examples 1 - 5 were tested respectively. The results are shown in Table 1: Table 1

[0102] The D50 was tested using an Omec particle size analyzer; the ZETA value was tested using a Dandong Baite ZETA analyzer; the activity index was tested with reference to the test method for the activity index of silica fume for mortar and concrete in GB / T 27690 - 2023. The test method for the 30-day suspension rate is as follows: Take 100 mL of silica fume mortar (the initial solid content is based on the actual formula, such as 20 - 30%), pour it into a 250 mL stoppered graduated cylinder (the scale is accurate to 1 mL), and let it stand at room temperature (25 ± 1°C) for 30 days, avoiding vibration during this period; after 30 days, record the volume of the upper liquid (V1) and the volume of the lower settled object (V2), and the suspension rate is equal to V1 / 100 * 100%.

[0103] From the data in Table 1, it can be seen that: In Examples 1 - 5, different monovalent ion bases were used to adjust the pH value of the silica fume mortar. The difference in pH value is not significant, and the difference in the ZETA value and activity index of the prepared silica fume mortar is not significant, but there are differences in D50 and the 30-day suspension rate; this shows that adjusting the pH value with different monovalent ion bases has little effect on the dispersibility of the silica fume mortar.

[0104] To verify the influence of different polyelectrolytes on the dispersibility of silica fume mortar, it is illustrated through the following specific examples.

[0105] Example 6: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, potassium polyacrylate (molecular weight 3000) is used.

[0106] Example 7: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, sodium polymaleate (molecular weight 3000) is used.

[0107] Example 8: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, potassium polymaleate (molecular weight 3000) is used.

[0108] Example 9: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, acrylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer (molecular weight 3000) is used.

[0109] Example 10: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, carboxylic acid-sulfonate copolymer (molecular weight 3000) is used.

[0110] Example 11: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, hydrolyzed polymaleic anhydride (molecular weight 3000) is used.

[0111] Example 12: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, maleic acid-acrylic acid copolymer (molecular weight 3000) is used.

[0112] Example 13: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolyte used is different. In this example, sodium maleic acid-acrylic acid copolymer (molecular weight 3,000) is used.

[0113] Example 14: This example is based on Example 1, and the difference from Example 1 is that: The polyelectrolytes used are different. In this example, polyacrylic acid (molecular weight 3000) is used.

[0114] Example 15: This example is based on Example 1. The difference from Example 1 is that: The polyelectrolytes used are different. In this example, sodium polybutene sulfonate (molecular weight 3000) is used.

[0115] Comparative Example 1: This comparative example is based on Example 1. The difference from Example 1 is that: The polyelectrolytes used are different. In this comparative example, sodium poly(naphthalene formaldehyde sulfonate) (molecular weight 3000) is used.

[0116] Comparative Example 2: This comparative example is based on Example 1. The difference from Example 1 is that: The polyelectrolytes used are different. In this comparative example, melamine is used.

[0117] Comparative Example 3: This comparative example is based on Example 1. The difference from Example 1 is that: The polyelectrolytes used are different. In this comparative example, polycarboxylic acid (molecular weight 3000) is used.

[0118] Comparative Example 4: This comparative example is based on Example 1. The difference from Example 1 is that: No electrolyte is added, and no alkali is added to adjust the pH.

[0119] Comparative Example 5:

[0120] This comparative example is based on Example 1. The difference from Example 1 is that: No electrolyte is added.

[0121] The D50, ZETA value, activity index, and 30-day suspension rate of the silica fume mortar of Examples 6 - 15 and Comparative Examples 1 - 5 were tested respectively. The results are shown in Table 2: Table 2

[0122] From the data in Table 2, it can be seen that: Using different polyelectrolytes exemplified in the present invention has little effect on the D50, ZETA value, activity index, and 30-day suspension rate of the prepared silica fume mortar.

[0123] In order to verify the influence of different dosages of polyelectrolytes on the dispersibility of silica fume mortar, it is illustrated through the following specific examples.

[0124] Example 16: This example is based on Example 1, and the difference from Example 1 is as follows: The dosage of sodium polyacrylate is 0.5%.

[0125] Example 17: This example is based on Example 1, and the difference from Example 1 is as follows: The dosage of sodium polyacrylate is 1.0%.

[0126] Example 18: This example is based on Example 1, and the difference from Example 1 is as follows: The dosage of sodium polyacrylate is 2.0%.

[0127] Comparative Example 6: This example is based on Example 1, and the difference from Example 1 is as follows: The dosage of sodium polyacrylate is 2.5%.

[0128] Comparative Example 7: This example is based on Example 1, and the difference from Example 1 is as follows: The dosage of sodium polyacrylate is 3.0%.

[0129] The D50, ZETA value, activity index and 30-day suspension rate of silica fume mortar in Examples 16 - 18 and Comparative Examples 6 - 7 were tested respectively. The results are shown in Table 3: Table 3

[0130] It can be seen from the data in Table 3 that: In silica fume mortar, as the dosage of sodium polyacrylate increases, the ZETA value increases slightly, the D50 and activity index do not change significantly, but the 30-day suspension rate shows a downward trend.

[0131] In order to verify the influence of different pH values on the dispersibility of silica fume mortar, it is illustrated through the following specific examples.

[0132] Comparative Example 8: This comparative example is based on Example 1, and the difference from Example 1 is as follows: Sodium hydroxide is not added to adjust the pH value.

[0133] Comparative Example 9: This comparative example is based on Example 1, and the difference from Example 1 is as follows: The addition amount of sodium hydroxide is reduced, specifically to 0.05%.

[0134] Example 19: This example is based on Example 1, and the difference from Example 1 is as follows: The addition amount of sodium hydroxide is increased, specifically 0.22%.

[0135] Example 20: This example is based on Example 1, and the difference from Example 1 is that: The addition amount of sodium hydroxide is increased, specifically 0.35%.

[0136] The D50, ZETA value, activity index and 30-day suspension rate of silica fume mortar in Examples 19 - 20 and Comparative Examples 8 - 9 were tested respectively. The results are shown in Table 4: Table 4

[0137] It can be seen from the data in Table 4 that: The pH value of silica fume mortar has a great influence on its D50, ZETA value, activity index and 30-day suspension rate. When the silica fume mortar is alkaline, the D50 decreases significantly, and the absolute value of ZETA and the activity index increase significantly.

[0138] When the pH value of silica fume mortar is between 8 - 13, there is no obvious change in D50 and activity index, the absolute value of ZETA increases with the increase of pH value, and the 30-day suspension rate decreases slightly with the increase of pH value; that is, a high pH value affects the charge, causes chemical dissolution, destroys the colloid balance, and has an impact on stability.

[0139] To verify the influence of polyelectrolytes with different molecular weights on the dispersibility of silica fume mortar, it is illustrated by the following specific examples.

[0140] Example 21: This example is based on Example 1, and the difference from Example 1 is that: The molecular weight of sodium polyacrylate is different. In this example, the molecular weight of sodium polyacrylate is 1000.

[0141] Example 22: This example is based on Example 1, and the difference from Example 1 is that: The molecular weight of sodium polyacrylate is different. In this example, the molecular weight of sodium polyacrylate is 10000.

[0142] Comparative Example 10: This example is based on Example 1, and the difference from Example 1 is that: The molecular weight of sodium polyacrylate is different. In this example, the molecular weight of sodium polyacrylate is 15000.

[0143] Comparative Example 11: This example is based on Example 1, and the difference from Example 1 is that: The molecular weights of sodium polyacrylate are different. In this example, the molecular weight of sodium polyacrylate is 20,000.

[0144] The D50, ZETA value, activity index, and 30-day suspension rate of the silica fume mortar in Examples 21 - 22 and Comparative Examples 10 - 11 were tested respectively. The results are shown in Table 5 as follows: Table 5

[0145] To verify the influence of different valence state ion bases on the dispersibility of silica fume mortar, it is illustrated through the following specific cases.

[0146] Example 23: This comparative example is based on Example 13, and the difference from Example 13 is that: A divalent ion base is used to adjust the pH, specifically magnesium hydroxide.

[0147] Example 24: This comparative example is based on Example 13, and the difference from Example 13 is that: A trivalent ion base is used to adjust the pH, specifically aluminum hydroxide.

[0148] The D50, ZETA value, activity index, and 30-day suspension rate of the silica fume mortar in Examples 23 - 24 were tested respectively. The results are shown in Table 6 as follows: Table 6

[0149] Comparative Example 12: This comparative example is based on Example 13, and the difference from Example 13 is that: During the preparation of the silica fume mortar, the high-speed dispersion operation in step S4 is not carried out.

[0150] Comparative Example 13: This comparative example is based on Example 13, and the difference from Example 13 is that: During the preparation of the silica fume mortar, sodium hydroxide is not dissolved in advance. The specific preparation process of the silica fume mortar in this comparative example includes the following steps: S1. Add sodium polyacrylate to a certain amount of water to obtain a mixed solution; keep stirring during the addition of sodium polyacrylate for 1 min to fully disperse sodium polyacrylate in water and form a stable mixed solution.

[0151] S2. Gradually add silica fume and sodium hydroxide to the mixed solution under stirring to obtain a super-dispersed and highly active silica fume mortar; the addition rate of silica fume is 5 kg / min to avoid agglomeration caused by too fast addition; S3. After the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment (1500 r / min), and the time of high-speed dispersion treatment is 10 min. Then, it is allowed to stand and filtered to obtain a super-dispersed and highly active silica fume slurry.

[0152] S4. After the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment (1500 r / min). Example 25: This example is based on Example 3. When preparing the silica fume slurry in Example 3, tetramethylammonium hydroxide was not dissolved in advance. The specific preparation process of the silica fume slurry in this comparative example includes the following steps: S1. Sodium polyacrylate is added to a certain amount of water to obtain a mixed solution; stirring is maintained during the addition of sodium polyacrylate, and the stirring continues for 1 min to fully disperse sodium polyacrylate in water to form a stable mixed solution.

[0153] S2. Under the stirring state, silica fume and tetramethylammonium hydroxide are gradually added to the mixed solution to obtain a super-dispersed and highly active silica fume slurry; the addition rate of silica fume is 5 kg / min to avoid agglomeration caused by too fast addition. S3. After the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment (1500 r / min), and the time of high-speed dispersion treatment is 10 min. Then, it is allowed to stand and filtered to obtain a super-dispersed and highly active silica fume slurry.

[0154] The D50, ZETA value, activity index, and 30-day suspension rate of the silica fume slurries of Comparative Example 12 - Comparative Example 13 and Example 25 are tested respectively. The results are shown in Table 7: Table 7

[0155] It can be seen from the data in Table 7 that: 1) When an organic base is used to adjust the pH value, it is not necessary to dissolve in advance; when an inorganic base is used to adjust the pH value, it needs to be dissolved in advance, otherwise the prepared silica fume slurry will agglomerate and cannot be used normally. 2) The activity of the silica fume slurry without high-speed dispersion treatment is relatively low, and its stability is poor.

[0156] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A super-dispersed high-activity silica mortar, including silica mortar, characterized in that, The silica slurry contains a polyelectrolyte, and the pH value of the silica slurry is 8 - 13; the polyelectrolyte is a linear carboxylic acid-based polymer and its salt; the molecular weight of the polyelectrolyte is 1000 - 10000.

2. The super-dispersed highly active silica mortar according to claim 1, characterized in that, The linear carboxylic acid-based polymer includes at least one of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, carboxylic acid-sulfonate copolymer, hydrolyzed polymaleic anhydride, maleic acid-acrylic acid copolymer / mixture, polyacrylic acid, polymaleic acid, and polybutenoic acid.

3. The super-dispersed highly active silica mortar according to claim 1, characterized in that, The pH value of the silica slurry is adjusted to 8 - 13 by a monovalent ion base and / or a divalent ion base and / or a trivalent ion base.

4. The super-dispersed highly active silica mortar according to claim 3, wherein The monovalent ion base includes at least one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine, and tetramethylammonium hydroxide; the divalent ion base includes magnesium hydroxide; the trivalent ion base includes aluminum hydroxide.

5. The super-dispersed highly active silica mortar according to claim 1, wherein The molecular weight of the polyelectrolyte is 3000 - 10000.

6. The hyper-dispersed highly active silica mortar according to claim 1, characterized in that, The salt of the linear carboxylic acid-based polymer includes at least one of sodium salt and potassium salt.

7. The highly dispersed and highly active silica mortar according to claim 1, wherein Based on the weight of silica fume in the silica slurry, the addition amount of the polyelectrolyte is 0.05% - 2%.

8. The super-dispersed highly active silica mortar according to claim 7, characterized in that, Based on the weight of silica fume in the silica slurry, the addition amount of the polyelectrolyte is 0.1% - 0.5%.

9. A super-dispersed high-activity silica mortar according to any one of claims 1 to 8, characterized in that, The pH value of the silica slurry is 8 - 11.

10. The super-dispersed highly active silica mortar according to claim 9, characterized in that, The silica slurry contains the following components: Na + 、OH - 、SiO3 2- / HSiO3 - and [PAA] - ; Optionally includes K + and / or (CH3)4N + and / or (C2H5)3NH + and / or NH4 + .

11. A super-dispersed high-activity silica mortar according to claim 9, characterized in that, The solid content of the silica slurry is 20 - 75%.

12. The preparation method of a super-dispersed and highly active silica mortar according to any one of claims 1 to 11, characterized in that, Including the following steps: S1. Dissolve the base in water to form an alkaline solution; S2. Add the polyelectrolyte to the alkaline solution to obtain a mixed solution; S3. Gradually add silica fume to the mixed solution under stirring to obtain the super-dispersed highly active silica slurry; When the base is an organic base, step S1 is selectively performed.

13. According to the preparation method described in claim 12, characterized in that: In step S3, after the addition of silica fume is completed, the mixed system is subjected to high-speed dispersion treatment, then left standing and filtered to obtain the super-dispersed highly active silica slurry; the equipment for high-speed dispersion treatment includes high-speed dispersion equipment, homogenizer, sand mill, colloid mill, or ball mill.

14. Use of a super-dispersed and highly active silica mortar according to any one of claims 1 to 11 in the preparation of concrete, characterized in that: The concrete includes ordinary commercial concrete, sleeper concrete, or UHPC concrete.

15. The application according to claim 14, wherein: Based on the weight of the cementitious material in the concrete, the addition amount of the silica slurry in the ordinary commercial concrete and the sleeper concrete is 3 - 10%; the addition amount of the silica slurry in the UHPC concrete is 1 - 16%.

16. A component, characterized in that: Prepared from concrete containing the super-dispersed highly active silica slurry described in any one of claims 1 - 11.

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