Prestressed duct grouting material based on superfine limestone powder and preparation method of prestressed duct grouting material

Abstract

The invention discloses a prestressed duct grouting material based on superfine limestone powder and a preparation method thereof, and relates to the technical field of prestressed duct grouting materials, the preparation method comprises the following steps: adding cement, modified superfine limestone powder, slag powder and fly ash into a stirrer, and uniformly stirring to obtain a dry mixture; sequentially adding a polycarboxylate nano-composite, diethanolisopropanolamine, sodium lignin sulfonate, diethanolamine citrate and a composite alkanolamine additive into water, and uniformly stirring to obtain a wet mixture; and adding the wet mixture into the dry mixture, and uniformly stirring to obtain the prestressed duct grouting material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of prestressed duct grouting material, in particular to a prestressed duct grouting material based on ultra-fine limestone powder and a preparation method thereof. BACKGROUND

[0002] Prestressed duct grouting material is a key material in post-tensioned prestressed structures, and its core function is to fill the gap between the prestressed duct, bond the prestressed tendon and the concrete matrix, and provide corrosion protection for the prestressed tendon, ensuring the overall stress and long-term service safety of the structure. It is widely used in prestressed concrete structures such as highway bridges and building engineering.

[0003] With the increasing requirements of modern engineering on construction efficiency, structural durability and service life, the traditional prestressed duct grouting material gradually exposes many technical shortcomings. In terms of workability, the traditional grouting material often faces the problem of difficult to balance flowability and slump retention: the initial flowability of some materials is insufficient, which easily leads to duct blockage during grouting process, and cannot realize uniform filling of long distance and narrow gap; although the initial flowability of some materials is good, the flowability loss is fast, and segregation and bleeding easily occur during construction process, forming internal cavities or layered defects, affecting the bonding effect and structural density.

[0004] In terms of mechanical property development, the traditional grouting material generally has the contradiction of poor synergy between early strength and later strength. Some early strength materials can meet the rapid tensioning demand, but often at the cost of workability or later durability, and easily appear strength reversal after long-term use; while the materials focusing on later strength have slow early strength development, which prolongs the construction period and is difficult to adapt to the construction scene under the demand of rush work or low temperature environment. At the same time, the traditional material has insufficient precision in controlling the hydration rate, and internal thermal stress is easily generated due to concentrated hydration heat, which causes microcracks.

[0005] In terms of durability and volume stability, the microstructure of the traditional grouting material is relatively loose, and the porosity is high, so the impermeability and anti-ion erosion ability are insufficient, and harmful ions in the outside world easily penetrate into the inside of the duct, causing the corrosion of the prestressed tendon and seriously affecting the service life of the structure; in addition, most materials easily produce drying shrinkage or autogenous shrinkage during hardening process, forming shrinkage cracks, damaging the sealing integrity of the duct, and further aggravating the durability risk.

[0006] In terms of component synergy, the interface compatibility of mineral admixtures and cementitious materials in the traditional grouting material is poor, and particle agglomeration easily occurs, forming interface defects and weakening the mechanical properties and durability; the synergy of chemical admixtures and mineral admixtures is insufficient, and it is difficult to simultaneously optimize multiple performance indicators such as workability, strength and volume stability.

[0007] In summary, the existing prestressed duct grouting material still needs to be improved in terms of work performance adaptability, mechanical property synergy, durability and volume stability, and a new grouting material with excellent fluidity and slump retention, reasonable hydration rate, high strength and durability, volume stability and good component synergy is urgently needed to meet the high-quality construction and long-term service requirements of modern prestressed engineering. SUMMARY

[0008] The purpose of the present application is to provide a prestressed duct grouting material based on ultra-fine limestone powder and a preparation method thereof to solve the problems in the prior art.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A preparation method of a prestressed duct grouting material based on ultra-fine limestone powder comprises the following steps: S1: crushing and ball-milling natural limestone ore, and sieving to obtain a base powder; adding nano-silica particles to anhydrous ethanol, and ultrasonic dispersion to obtain a nano-silica suspension; Further, the base powder has a specification D50=3.8-4.5μm; Further, the nano-silica has a particle size of 20-50nm; Further, the nano-silica suspension has a concentration of 5-6wt%; S2: adding the base powder to anhydrous ethanol, stirring uniformly, adding KH570, heating to 80-85℃ and stirring for 1-2h, cooling to 60-65℃, adding polyethylene glycol-poly-caprolactone copolymer and ammonium persulfate, constant temperature stirring for 1-1.5h, adding the nano-silica suspension, stirring uniformly, filtering to collect solid particles, vacuum drying at 80-85℃, grinding, and sieving through 120μm to obtain modified ultra-fine limestone powder; Further, the modified ultra-fine limestone powder has a component ratio, by mass percentage, comprising: 100 parts of base powder, 5-8 parts of KH570, 0.5-2.5 parts of polyethylene glycol-poly-caprolactone copolymer, 0.005-0.0125 parts of ammonium persulfate, and 15-20 parts of nano-silica suspension; S3: adding anhydrous calcium sulfate and sodium silicate nonahydrate to deionized water, stirring uniformly to obtain a mixed solution, adding isopentylen polyoxyethylene ether type polycarboxylate ether aqueous solution, ball-milling, adjusting the pH of the system to 11.6-11.8 using 30wt% sodium hydroxide solution under nitrogen atmosphere, stirring at room temperature for 30-35min, filtering, ultrasonic dispersion, vacuum drying, and grinding to obtain a polycarboxylate nanocomposite; Furthermore, the components of the polycarboxylate nanocomposite, by mass percentage, include 10-15 parts anhydrous calcium sulfate, 8-12 parts sodium silicate nonahydrate, and 20-25 parts an aqueous solution of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether; the concentration of the mixed solution is 0.5 mol / L; and the concentration of the isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution is 20-25 wt%. Furthermore, the polycarboxylate nanocomposite has an average particle size ≤60nm and a solid content of 30-40%. Furthermore, the preparation method of the isopentenol polyoxyethylene ether type polycarboxylate ether aqueous solution includes the following steps: adding isopentenol polyoxyethylene ether and diethyl ether to a reaction vessel, adding triethoxyvinylsilane and hydrogen peroxide, stirring evenly, adding auxiliary solution, stirring evenly, stirring at room temperature for 30-45 min, adjusting pH to 8-9, and obtaining the isopentenol polyoxyethylene ether type polycarboxylate ether aqueous solution; Furthermore, the components in the isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, by mass percentage, include: 100-105 parts isopentenyl alcohol polyoxyethylene ether, 0.23-0.27 parts diethyl ether, 2.2-2.3 parts triethoxyvinylsilane, 0.98-1.04 parts hydrogen peroxide, and 30-32 parts auxiliary solution; Furthermore, the isopentenyl alcohol polyoxyethylene ether has a weight-average molecular weight of 42,000-45,000. Furthermore, the hydrogen peroxide concentration is 30 wt%. Furthermore, the components in the auxiliary solution, by mass percentage, include: 0.38-0.42 parts vitamin C, 0.4-0.44 parts thioglycolic acid, 6-6.4 parts acrylic acid, and 24-26 parts deionized water; S4: Add cement, modified ultrafine limestone powder, slag powder, and fly ash to a mixer and stir at 15-30℃ for 3-5 minutes to obtain a dry mixture; add polycarboxylate nanocomposite, diethanolamine monoisopropanolamine, sodium lignosulfonate, diethanolamine citrate, and composite alkanolamine admixture to water in sequence and stir evenly to obtain a wet mixture; add the wet mixture to the dry mixture and stir evenly to obtain prestressed duct grouting material; Furthermore, the preparation method of the diethanolamine citrate includes the following steps: adding diethanolamine and citric acid into a reaction vessel, heating to 130-135℃ and reacting for 4-4.5h, cooling to 70-75℃, adding an ethanol solution of 20% w / w sodium ethoxide, maintaining the temperature for 2-2.5h, and cooling to room temperature to obtain diethanolamine citrate; Furthermore, in the preparation process of the diethanolamine citrate, the mass ratio of diethanolamine to citric acid is 3:1; Furthermore, the composite alkanolamine admixture is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of (0.5-2):1; Furthermore, the proportions of each component in the dry mix, by mass percentage, include: 60-70 parts cement, 15-20 parts modified ultrafine limestone powder, 5-8 parts slag powder, and 3-5 parts fly ash. Furthermore, the proportions of each component in the wet mixture, by mass percentage, include: 3-5 parts of polycarboxylate nanocomposite, 0.03-0.08 parts of diethanolamine monoisopropanolamine, 0.2-0.5 parts of sodium lignosulfonate, 0.02-0.05 parts of diethanolamine citrate, 0.01-0.03 parts of compound alkanolamine additive, and 10-15 parts of water.

[0010] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, modified ultrafine limestone powder forms a micron-nano multi-level filling system through a base powder and a nano-silica suspension, filling the hydration pores of cement. KH570 improves the interfacial compatibility with the cement matrix through chemical bonding, while polyethylene glycol-polycaprolactone copolymer reduces particle agglomeration and improves dispersion uniformity. Nano-silica acts as hydration nucleation sites, promoting CSH gel formation. This significantly reduces slurry porosity, improves microstructure density, enhances interfacial bonding strength, avoids defects caused by agglomeration, strengthens impermeability and resistance to ion leaching, and helps improve mechanical strength.

[0011] 2. This invention utilizes the comb-like structure of isopentenyl alcohol polyoxyethylene ether-type polycarboxylate ether to disperse cement particles through electrostatic repulsion and steric hindrance effects; anhydrous calcium sulfate reacts with sodium silicate nonahydrate to generate a CSH-like precursor, which acts as a hydration seed to accelerate hydration; the nanoscale increases the specific surface area and enhances the interfacial adsorption with hydration products. This further optimizes the slurry's fluidity and slump retention, reduces the water-cement ratio, inhibits segregation and bleeding, ensures uniform grouting, accelerates early strength development, and improves the density of the hardened structure.

[0012] 3. This invention accelerates early strength development by activating the hydration reaction of C3A and C4AF in cement with diethanolamine; citric acid chelates Ca... 2+ Moderately delaying the hydration process balances early strength and the construction window; chelation stabilizes free Ca. 2+ Concentration reduces crystallization stress and synergistically activates C3A hydration with triethanolamine, achieving early rapid hardening; triisopropanolamine focuses on activating C4AF and later hydration, promoting long-term strength growth; achieving early rapid hardening and later high strength to meet the requirements of rapid tensioning and long-term load bearing; optimizing the structure of hydration products enhances erosion resistance; regulating the release of hydration heat reduces thermal stress cracking; and enhancing the bond strength between the slurry and the reinforcing steel and duct walls.

[0013] 4. This invention utilizes the dispersion effect of polycarboxylate nanocomposites to create uniform spaces for the multi-level filling of modified ultrafine limestone powder, maximizing the densification effect; the hydration activation of composite alkanolamines and the hydration regulation of diethanolamine citrate synergistically balance early strength and crack resistance; the interfacial modification of the limestone powder, the interfacial adsorption of the nanocomposites, and the ion stabilization of citrate synergistically reduce interfacial defects. The prepared pore slurry exhibits excellent slurry fluidity and slump retention, making it suitable for grouting in long-distance narrow pores; early strength meets the requirements of rapid tensioning, and later strength continues to increase, resulting in strong adhesion; the microstructure is dense, improving impermeability and corrosion resistance; low shrinkage rate and no hardening cracks ensure the integrity of the pore seal. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The following examples illustrate the preparation method of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, which includes the following steps: adding 100 parts of isopentenyl alcohol polyoxyethylene ether and 0.23 parts of diethyl ether to a reaction vessel, adding 2.2 parts of triethoxyvinylsilane and 0.98 parts of 30wt% hydrogen peroxide, stirring evenly, adding 30 parts of auxiliary solution, stirring evenly, stirring at room temperature for 30 min, adjusting the pH to 8, and obtaining isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution; The components in the auxiliary solution, by mass percentage, include: 0.38 parts vitamin C, 0.4 parts thioglycolic acid, 6 parts acrylic acid, and 24 parts deionized water.

[0016] The preparation method of diethanolamine citrate includes the following steps: adding diethanolamine and citric acid into a reaction vessel, heating to 130°C and reacting for 4 hours, cooling to 70°C, adding 20% ​​w / w sodium ethoxide ethanol solution, keeping the temperature for 2 hours, and cooling to room temperature to obtain diethanolamine citrate. In the preparation of the diethanolamine citrate, the mass ratio of diethanolamine to citric acid is 3:1; Example 1: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S1: crushing natural limestone ore, ball milling and sieving to obtain basic powder; adding nano-silica particles to anhydrous ethanol and ultrasonically dispersing to obtain a 5wt% nano-silica suspension; S2: Add 100 parts of the base powder to anhydrous ethanol, stir evenly, add 5 parts of KH570, heat to 80℃ and stir for 1 hour, cool to 60℃, add 0.5 parts of polyethylene glycol-polycaprolactone copolymer and 0.005 parts of ammonium persulfate, stir at constant temperature for 1 hour, add 15 parts of nano silica suspension, stir evenly, filter to collect solid particles, vacuum dry at 80℃, grind, and sieve through 120μm to obtain modified ultrafine limestone powder; S3: Add 10 parts of anhydrous calcium sulfate and 8 parts of sodium silicate nonahydrate to deionized water, stir evenly to obtain a 0.5 mol / L mixed solution, add 20 parts of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, ball mill, adjust the pH of the system to 11.6 with 30 wt% sodium hydroxide solution under nitrogen atmosphere, stir at room temperature for 30 min, filter, ultrasonically disperse, vacuum dry, grind to obtain polycarboxylate nanocomposite; S4: Add 65 parts cement, 18 parts modified ultrafine limestone powder, 6 parts slag powder, and 5 parts fly ash to a mixer and stir at 25°C for 3 minutes to obtain a dry mixture; add 4 parts polycarboxylate nanocomposite, 0.05 parts diethanolamine monoisopropanolamine, 0.3 parts sodium lignosulfonate, 0.03 parts diethanolamine citrate, and 0.2 parts composite alkanolamine admixture to 10 parts water in sequence and stir evenly to obtain a wet mixture; add the wet mixture to the dry mixture and stir evenly to obtain prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 1:1.

[0017] Example 2: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S4: 65 parts cement, 18 parts modified ultrafine limestone powder, 6 parts slag powder, and 5 parts fly ash are added to a mixer and stirred at 25°C for 3 minutes to obtain a dry mixture; 4 parts polycarboxylate nanocomposite, 0.05 parts diethanolamine monoisopropanolamine, 0.3 parts sodium lignosulfonate, 0.03 parts diethanolamine citrate, and 0.2 parts composite alkanolamine admixture are sequentially added to 10 parts water and stirred evenly to obtain a wet mixture; the wet mixture is added to the dry mixture and stirred evenly to obtain the prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 2:1.

[0018] The remaining steps are the same as in Example 1.

[0019] Example 3: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S4: 62 parts of cement, 20 parts of modified ultrafine limestone powder, 7 parts of slag powder, and 4 parts of fly ash are added to a mixer and stirred at 25°C for 3 minutes to obtain a dry mixture; 4 parts of polycarboxylate nanocomposite, 0.05 parts of diethanolamine monoisopropanolamine, 0.3 parts of sodium lignosulfonate, 0.03 parts of diethanolamine citrate, and 0.2 parts of composite alkanolamine admixture are sequentially added to 10 parts of water and stirred evenly to obtain a wet mixture; the wet mixture is added to the dry mixture and stirred evenly to obtain the prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 1:1.

[0020] The remaining steps are the same as in Example 1.

[0021] Comparative Example 1: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S1: crushing natural limestone ore, ball milling, and sieving to obtain basic powder; S2: Add 10 parts of anhydrous calcium sulfate and 8 parts of sodium silicate nonahydrate to deionized water, stir evenly to obtain a 0.5 mol / L mixed solution, add 20 parts of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, ball mill, adjust the pH of the system to 11.6 with 30 wt% sodium hydroxide solution under nitrogen atmosphere, stir at room temperature for 30 min, filter, ultrasonically disperse, vacuum dry, grind to obtain polycarboxylate nanocomposite; S3: Add 65 parts cement, 18 parts base powder, 6 parts slag powder, and 5 parts fly ash to a mixer and stir at 25°C for 3 minutes to obtain a dry mix; add 4 parts polycarboxylate nanocomposite, 0.05 parts diethanolamine monoisopropanolamine, 0.3 parts sodium lignosulfonate, 0.03 parts diethanolamine citrate, and 0.2 parts composite alkanolamine admixture to 10 parts water in sequence and stir evenly to obtain a wet mix; add the wet mix to the dry mix and stir evenly to obtain prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 1:1.

[0022] Comparative Example 2: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S1: crushing natural limestone ore and then ball milling and sieving to obtain basic powder; adding nano-silica particles to anhydrous ethanol and ultrasonically dispersing to obtain a 5wt% nano-silica suspension. S2: Add 100 parts of the base powder to anhydrous ethanol, stir evenly, add 5 parts of KH570, heat to 80℃ and stir for 1 hour, cool to 60℃, add 0.5 parts of polyethylene glycol-polycaprolactone copolymer and 0.005 parts of ammonium persulfate, stir at constant temperature for 1 hour, add 15 parts of nano silica suspension, stir evenly, filter to collect solid particles, vacuum dry at 80℃, grind, and sieve through 120μm to obtain modified ultrafine limestone powder; S3: Add 10 parts of anhydrous calcium sulfate and 8 parts of sodium silicate nonahydrate to deionized water, stir evenly to obtain a 0.5 mol / L mixed solution, add 20 parts of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, ball mill, adjust the pH of the system to 11.6 with 30 wt% sodium hydroxide solution under nitrogen atmosphere, stir at room temperature for 30 min, filter, ultrasonically disperse, vacuum dry, grind to obtain polycarboxylate nanocomposite; S4: Add 65 parts cement, 18 parts modified ultrafine limestone powder, 6 parts slag powder, and 5 parts fly ash to a mixer and stir at 25°C for 3 minutes to obtain a dry mixture; add 0.05 parts diethanolamine monoisopropanolamine, 0.3 parts sodium lignosulfonate, 0.03 parts diethanolamine citrate, and 0.2 parts composite alkanolamine admixture to 14 parts water and stir evenly to obtain a wet mixture; add the wet mixture to the dry mixture and stir evenly to obtain prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 1:1.

[0023] Comparative Example 3: A method for preparing prestressed duct grouting material based on ultrafine limestone powder: including the following steps: S1: crushing natural limestone ore, ball milling and sieving to obtain basic powder; adding nano-silica particles to anhydrous ethanol and ultrasonically dispersing to obtain a 5wt% nano-silica suspension. S2: Add 100 parts of the base powder to anhydrous ethanol, stir evenly, add 5 parts of KH570, heat to 80℃ and stir for 1 hour, cool to 60℃, add 0.5 parts of polyethylene glycol-polycaprolactone copolymer and 0.005 parts of ammonium persulfate, stir at constant temperature for 1 hour, add 15 parts of nano silica suspension, stir evenly, filter to collect solid particles, vacuum dry at 80℃, grind, and sieve through 120μm to obtain modified ultrafine limestone powder; S3: Add 10 parts of anhydrous calcium sulfate and 8 parts of sodium silicate nonahydrate to deionized water, stir evenly to obtain a 0.5 mol / L mixed solution, add 20 parts of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, ball mill, adjust the pH of the system to 11.6 with 30 wt% sodium hydroxide solution under nitrogen atmosphere, stir at room temperature for 30 min, filter, ultrasonically disperse, vacuum dry, grind to obtain polycarboxylate nanocomposite; S4: Add 65 parts cement, 18 parts modified ultrafine limestone powder, 6 parts slag powder, and 5 parts fly ash to a mixer and stir at 25°C for 3 minutes to obtain a dry mixture; add 4 parts polycarboxylate nanocomposite, 0.05 parts diethanolamine monoisopropanolamine, 0.3 parts sodium lignosulfonate, and 0.03 parts diethanolamine citrate to 10.2 parts water and stir evenly to obtain a wet mixture; add the wet mixture to the dry mixture and stir evenly to obtain a prestressed duct grouting material; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of 1:1.

[0024] Performance testing: The prestressed grouting materials in the examples and comparative examples were tested according to the methods of JTG / T F50 and GB / T17671. The specific results are shown in Table 1 below: Table 1 Performance Test Data of Prestressed Duct Grouting Material

[0025] Conclusion: The performance parameters of the prestressed duct grouting material prepared by this invention meet the performance index requirements of grouting material in the "Technical Specification for Construction of Highway Bridges and Culverts" (JTG / T 3650-2020).

[0026] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing prestressed duct grouting material based on ultrafine limestone powder, characterized in that: Includes the following steps: Cement, modified ultrafine limestone powder, slag powder, and fly ash are added to a mixer and stirred evenly to obtain a dry mixture. Polycarboxylate nanocomposite, diethanolamine monoisopropanolamine, sodium lignosulfonate, diethanolamine citrate, and composite alkanolamine admixture are added to water in sequence and stirred evenly to obtain a wet mixture. The wet mixture is added to the dry mixture and stirred evenly to obtain a prestressed duct grouting material.

2. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The preparation method of the modified ultrafine limestone powder includes the following steps: adding the base powder to anhydrous ethanol, stirring evenly, adding KH570, heating to 80-85℃ and stirring for 1-2 hours, cooling to 60-65℃, adding polyethylene glycol-polycaprolactone copolymer and ammonium persulfate, stirring at a constant temperature for 1-1.5 hours, adding nano-silica suspension, stirring evenly, filtering to collect solid particles, vacuum drying at 80-85℃, grinding, and sieving to obtain modified ultrafine limestone powder; The modified ultrafine limestone powder comprises the following components by mass percentage: 100 parts base powder, 5-8 parts KH570, 0.5-2.5 parts polyethylene glycol-polycaprolactone copolymer, 0.005-0.0125 parts ammonium persulfate, and 15-20 parts nano silica suspension.

3. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The preparation method of the basic powder includes the following steps: crushing natural limestone ore, ball milling, and sieving to obtain the basic powder; The basic powder specification D50 is 3.8-4.5μm.

4. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The preparation method of the nano-silica suspension includes the following steps: adding nano-silica particles to anhydrous ethanol and dispersing them by ultrasonication to obtain a nano-silica suspension; The concentration of the nano-silica suspension is 5-6 wt%.

5. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The preparation method of the polycarboxylate nanocomposite includes the following steps: adding anhydrous calcium sulfate and sodium silicate nonahydrate to deionized water, stirring evenly to obtain a mixed solution, adding isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution, ball milling, adjusting the pH of the system to 11.6-11.8 with 30wt% sodium hydroxide solution under nitrogen atmosphere, stirring at room temperature for 30-35 min, filtering, ultrasonic dispersion, vacuum drying, and grinding to obtain the polycarboxylate nanocomposite; The polycarboxylate nanocomposite comprises, by mass percentage, 10-15 parts anhydrous calcium sulfate, 8-12 parts sodium silicate nonahydrate, and 20-25 parts an aqueous solution of isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether.

6. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 5, characterized in that: The method for preparing the isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution includes the following steps: adding isopentenyl alcohol polyoxyethylene ether and diethyl ether to a reaction vessel, adding triethoxyvinylsilane and hydrogen peroxide, stirring evenly, adding auxiliary solution, stirring evenly, stirring at room temperature for 30-45 min, adjusting pH to 8-9, and obtaining the isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution. The components in the isopentenyl alcohol polyoxyethylene ether type polycarboxylate ether aqueous solution are, by mass percentage: 100-105 parts isopentenyl alcohol polyoxyethylene ether, 0.23-0.27 parts diethyl ether, 2.2-2.3 parts triethoxyvinylsilane, 0.98-1.04 parts hydrogen peroxide, and 30-32 parts auxiliary solution; The components in the auxiliary solution, by mass percentage, include: 0.38-0.42 parts vitamin C, 0.4-0.44 parts thioglycolic acid, 6-6.4 parts acrylic acid, and 24-26 parts deionized water.

7. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The preparation method of the diethanolamine citrate includes the following steps: adding diethanolamine and citric acid into a reaction vessel, heating to 130-135℃ and reacting for 4-4.5h, cooling to 70-75℃, adding 20% ​​w / w sodium ethoxide ethanol solution, keeping the reaction at the temperature for 2-2.5h, and cooling to room temperature to obtain diethanolamine citrate. In the preparation of diethanolamine citrate, the mass ratio of diethanolamine to citric acid is 3:1; The composite alkanolamine additive is prepared by mixing triethanolamine and triisopropanolamine in a mass ratio of (0.5-2):

1.

8. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The dry mix comprises the following components by mass percentage: 60-70 parts cement, 15-20 parts modified ultrafine limestone powder, 5-8 parts slag powder, and 3-5 parts fly ash.

9. The method for preparing a prestressed duct grouting material based on ultrafine limestone powder according to claim 1, characterized in that: The wet mixture comprises the following components by mass percentage: 3-5 parts polycarboxylate nanocomposite, 0.03-0.08 parts diethanolamine monoisopropanolamine, 0.2-0.5 parts sodium lignosulfonate, 0.02-0.05 parts diethanolamine citrate, 0.01-0.03 parts compound alkanolamine additive, and 10-15 parts water.

10. The prestressed grouting material prepared by the method for preparing prestressed duct grouting material based on ultrafine limestone powder according to any one of claims 1-9.

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