Ultrahigh-performance fiber-reinforced sleeve grouting material as well as preparation method and application method thereof

Abstract

The invention belongs to the technical field of grouting materials, and particularly relates to an ultrahigh-performance fiber-reinforced sleeve grouting material as well as a preparation method and an application method thereof. The grouting material is prepared from the following components in parts by weight: 100 parts of P.O62.5 ordinary Portland cement, 20 to 30 parts of nano silica fume, 30 to 40 parts of superfine quartz powder, 5 to 8 parts of nano calcium carbonate, 1.5 to 2.5 parts of a silane coupling agent, 5 to 7 parts of a third-generation polycarboxylic acid water reducing agent, 0.1 to 0.3 part of a viscosity modifier, 10 to 15 parts of a UEA expanding agent, 2 to 4 parts of an aluminum sulfate shrinkage compensating agent and 1 to 2 parts of a polyacrylic acid shrinkage reducing agent. The multi-scale fiber system is prepared from 0.8 vol% to 1.2 vol% of polyvinyl alcohol fiber, 0.4 vol% to 0.8 vol% of basalt fiber, 0.3 vol% to 0.5 vol% of steel fiber, 0.05 vol% to 0.1 vol% of nano cellulose fiber and 0.02 vol% to 0.05 vol% of carbon nanofiber. The invention provides the fiber-reinforced sleeve grouting material with ultrahigh strength and ultrahigh toughness as well as the preparation method and the application method thereof, the strain hardening characteristic is realized, and the brittle failure mode of the traditional material is fundamentally changed.

Description

An ultra-high performance fiber-reinforced sleeve grouting material and its preparation and application methods Technical Field

[0001] This invention belongs to the field of grouting materials technology, and specifically relates to an ultra-high performance fiber-reinforced sleeve grouting material and its preparation and application methods. Background Technology

[0002] Grouting materials used for rebar connections in prefabricated buildings suffer from significant lack of toughness in practical engineering applications. While traditional cement-based grouting materials can meet the basic strength requirements of the national standard JG / T408-2019 (1d≥35MPa, 3d≥60MPa, 28d≥85MPa), and high-quality products can even achieve higher strength indicators (28-day strength can reach 100-132MPa), their brittle characteristics are obvious. Under extreme or cyclic loading conditions such as earthquakes, wind loads, and fatigue loads, they are prone to sudden brittle fracture failure, leading to rebar connection failure and seriously threatening the safety and durability of prefabricated building structures.

[0003] The main drawbacks of existing technologies are: First, the materials are highly brittle and lack sufficient safety margin. The stress-strain curves of traditional sleeve grouting materials exhibit typical brittle failure characteristics: after reaching peak strength, they rapidly lose their load-bearing capacity, with extremely low fracture energy (typically <2kJ / m2). Under extreme loads such as earthquakes, brittle failure may lead to sudden failure of the reinforcing steel connections without any warning, seriously threatening structural safety. Furthermore, the flexural toughness indices (I5, I10) are generally below 5, far from meeting the requirements for areas with high seismic fortification intensity.

[0004] Second, poor impact resistance. When subjected to unexpected impacts during construction or use, brittle grouting materials are prone to cracking or even breakage, affecting the effective bond between the reinforcing steel and the sleeve. Existing materials typically have an impact energy resistance of less than 30J, making it difficult to withstand various impact loads in actual engineering projects.

[0005] Third: Short fatigue life. In structures subjected to cyclic loads, such as bridges and high-rise buildings, traditional grouting materials are prone to the accumulation and propagation of microcracks under fatigue loads, leading to a rapid decline in strength and bonding performance. After 2 million fatigue cycles, the strength retention rate is typically less than 70%.

[0006] Fourth: Limited fiber reinforcement effect. The few existing technologies involving fiber reinforcement suffer from the following problems: 1. Single fiber type: Using only one type of fiber (such as glass fiber powder) fails to achieve multi-scale synergistic toughening. 2. Insufficient fiber content: The volumetric content is typically <1%, far below the requirements for high-performance fiber-reinforced concrete (1.5-3%). 3. Poor fiber dispersion: Lacking effective dispersion technology, fibers easily agglomerate, failing to fully exert their reinforcing effect. 4. Weak interfacial bonding: The fiber surface is untreated, resulting in defects in the transition zone between the fiber and the cement matrix, making the fibers prone to pull-out.

[0007] Fifth: High fiber content leads to a sharp decrease in fluidity. While increasing fiber content can improve toughness, it significantly reduces material fluidity, making it difficult to meet the requirements of sleeve grouting construction. National standard JG / T408-2019 requires an initial fluidity ≥300mm and a 30-minute fluidity ≥260mm, while high-quality products typically achieve an initial fluidity of 340-360mm and a 30-minute fluidity ≥300mm to ensure better workability. Current technology lacks an effective way to achieve high fiber content while maintaining high fluidity.

[0008] Sixth: The cost-effectiveness ratio is not ideal. While some high-performance solutions offer excellent performance, their high material costs or complex construction processes limit their large-scale engineering applications. For example, the extensive use of high-alumina cement and nanomaterials significantly increases costs. Summary of the Invention

[0009] In order to solve the above-mentioned problems in the existing technology, the purpose of this invention is to provide a fiber-reinforced sleeve grouting material with ultra-high strength and ultra-high toughness, as well as its preparation method and application method, so as to achieve strain hardening characteristics and fundamentally change the brittle failure mode of traditional materials.

[0010] The technical solution adopted in this invention is as follows: an ultra-high performance fiber-reinforced sleeve grouting material, comprising, by weight, 100 parts of P.O62.5 ordinary silicate cement, 20-30 parts of nano silica fume (specific surface area ≥25000m2 / kg), 30-40 parts of ultrafine quartz powder (D50<5μm), 5-8 parts of nano calcium carbonate (particle size <100nm), 1.5-2.5 parts of silane coupling agent (KH-550), 5-7 parts of third-generation polycarboxylate superplasticizer (water reduction rate ≥45%), and viscosity modifier (konjac). The product contains 0.1-0.3 parts of glucomannan, 10-15 parts of UEA expanding agent, 2-4 parts of aluminum sulfate shrinkage compensator, and 1-2 parts of polyacrylic acid shrinkage reducing agent; it also includes a multi-scale fiber system with a volume content of 1.5-2.5 vol%; the multi-scale fiber system includes 0.8-1.2 vol% polyvinyl alcohol fiber, 0.4-0.8 vol% basalt fiber, 0.3-0.5 vol% steel fiber, 0.05-0.1 vol% nanocellulose fiber, and 0.02-0.05 vol% carbon nanofiber.

[0011] As a preferred embodiment of the present invention, the amount of nano-silica fume is 25 parts, the amount of ultrafine quartz powder is 35 parts, and the amount of nano-calcium carbonate is 6 parts.

[0012] As a preferred embodiment of the present invention, the volume content of polyvinyl alcohol fiber is 1.0 vol%, the volume content of basalt fiber is 0.6 vol%, and the volume content of steel fiber is 0.4 vol.

[0013] A method for preparing an ultra-high performance fiber-reinforced sleeve grouting material includes the following steps: S1: Fiber pretreatment: Surface modification of polyvinyl alcohol fiber, basalt fiber, and steel fiber; ultrasonic dispersion of nanocellulose and carbon nanofiber in 0.5% carboxymethyl cellulose aqueous solution; S2: Dry mixing premixing: Mixing cementitious materials, aggregates, 1 / 3 volume of water-reducing agent, and expanding agent, and stirring at low speed; S3: Batch fiber addition: First adding macro-fiber and stirring, then adding interface reinforcing agent and micro / nano-fiber suspension and stirring; S4: High-shear wet mixing: Adding water and the remaining water-reducing agent and viscosity modifier mixture, stirring at high shear, adding shrinkage reducing agent and continuing stirring; S5: Ultrasonic-assisted dispersion: Intermittent ultrasonication using an ultrasonic probe; S6: Static testing: Letting stand for a certain time and testing the flowability.

[0014] As a preferred embodiment of the present invention, it also includes a fiber surface modification method: polyvinyl alcohol fiber is immersed in a 5% polyvinyl alcohol aqueous solution for 30 minutes and then dried at 60°C for 2 hours; basalt fiber is surface treated with low-temperature plasma (power 200W) for 10 minutes; steel fiber is polished with 600-grit sandpaper and soaked in a 5% hydrochloric acid solution for 5 minutes to remove rust.

[0015] As a preferred embodiment of the present invention, in step S4, the water-to-binder ratio is 0.16-0.18.

[0016] As a preferred embodiment of the present invention, in step S4, the high shear stirring speed is 650 rpm and the stirring time is 18 min.

[0017] As a preferred embodiment of the present invention, vibration is applied during grouting construction using ultra-high performance fiber-reinforced sleeve grouting material, with a vibration frequency of 50Hz, an amplitude of 5mm, and a duration of 30 seconds.

[0018] As a preferred embodiment of the present invention, the high-performance fiber-reinforced sleeve grouting material obtained meets the following properties: 1-day compressive strength ≥60 MPa, 3-day compressive strength ≥85 MPa, 24-hour compressive strength ≥90 MPa, 28-day compressive strength ≥160 MPa, 28-day flexural strength ≥25 MPa, initial flowability 320-360 mm, 30-minute flowability ≥300 mm, bleeding rate 0%, 3-hour vertical expansion rate 0.05-0.15%, flexural toughness index I5 and I10 both ≥30, fracture energy ≥20 kJ / m2, ultimate tensile strain 3-5%, impact energy ≥150 J, fatigue life strength retention rate ≥90%, steel bar bond strength ≥50 MPa, sleeve-grouting material bond strength ≥40 MPa, freeze-thaw cycle resistance ≥300 cycles.

[0019] An application method for an ultra-high performance fiber-reinforced sleeve grouting material, which is applied to prefabricated buildings in high-intensity earthquake zones, prefabricated structures subjected to dynamic or fatigue loads, steel reinforcement connections in important structural parts, and prefabricated building projects requiring high safety reserves and toughness.

[0020] The beneficial effects of this invention are as follows: 1. It is the first to propose the concept of multi-scale fiber synergistic toughening: constructing a fiber reinforcement system from the nano, micro and macro scales to achieve full-scale crack control.

[0021] 2. First realization of strain hardening characteristics of sleeve grouting material: By precisely designing the fiber type, dosage and interfacial strength, the material exhibits strain hardening behavior during tensile process, completely changing the traditional brittle failure mode.

[0022] 3. Innovative fiber dispersion process: A four-step dispersion technology of "dry mixing premixing + batch addition + high shear stirring + ultrasonic assistance" was developed to solve the problem of uniform dispersion of high fiber content.

[0023] 4. Breakthrough in interface enhancement technology: Through various means such as PVA impregnation, plasma treatment, and silane coupling agent bridging, the strength of the fiber-matrix interface is precisely controlled.

[0024] 5. Maintaining flowability under high fiber content: The introduction of konjac glucomannan rheology modifier maintains excellent flowability even with a fiber content of 1.5-2.5 vol%.

[0025] 6. Ultra-high performance matrix design: A large amount of nano-silica fume (20-30%) is combined with ultrafine quartz powder and nano-calcium carbonate to achieve ultra-high strength and ultra-low porosity of the matrix.

[0026] 7. Performance indicators significantly surpass existing technologies: bending toughness index is increased by more than 5 times, fracture energy by more than 9 times, and fatigue life by more than 30%, providing strong protection for the safety of prefabricated buildings. Attached Figure Description

[0027] Figure 1 is a schematic diagram of multi-scale fiber distribution. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0030] I. Overall Concept of Technical Solution This invention adopts a triple reinforcement strategy of "ultra-high performance matrix + multi-scale fiber toughening + interface reinforcement" to construct a revolutionary sleeve grouting material system. Figure 1: Schematic diagram of multi-scale fiber distribution.

[0031] Technical Approach: A dense, ultra-high-performance cementitious matrix is ​​constructed using ultrafine powders (nano silica fume, ultrafine quartz powder, nano calcium carbonate). A multi-scale fiber system is introduced, comprising macro-fibers (PVA fibers, basalt fibers, steel fibers), microfibers (nanocellulose), and nanofibers (carbon nanofibers). Interfacial bonding is strengthened through fiber surface modification (silanization, PVA impregnation, plasma treatment). High-shear mixing combined with ultrasonic-assisted technology ensures uniform fiber dispersion. Third-generation polycarboxylate superplasticizers and rheology modifiers are used to guarantee workability.

[0032] II. Composition of Ultra-High Performance Cementitious System 2.1 Formulation Composition (by weight) Main cementitious material: P.O62.5 ordinary Portland cement: 100 parts (standard). Function: Provides the main strength contribution. Technical requirements: Strength grade 62.5, specific surface area ≥400 m² 2 / kg.

[0033] Ultrafine active admixture: Nano silica fume: 20-30 parts (preferably 25 parts). Particle size: <1μm; Specific surface area: ≥25000m² 2 / kg; SiO2 content: ≥92%. Function: Fills micropores, undergoes pozzolanic reaction, and greatly improves the density and strength of the matrix.

[0034] Ultrafine quartz powder: 30-40 parts (preferably 35 parts). Median particle size D50: <5μm; Specific surface area: ≥450m² 2 / kg. Function: Optimizes particle size distribution, filler effect, and improves density and hardness.

[0035] Nano-calcium carbonate: 5-8 parts (preferably 6 parts). Particle size: <100nm. Function: Nanofiller, provides crystal nuclei, accelerates hydration, and enhances the interfacial region.

[0036] Mechanism of action: Ultrafine powder achieves the following through a triple effect of "filling effect + pozzolanic effect + nucleation effect": 1. Filling the gaps between cement particles, significantly reducing porosity (<3%); 2. Nano-SiO2 reacts with Ca(OH)2 to generate CSH gel, enhancing the cementitious phase; 3. Nanoparticles act as heterogeneous nuclei, promoting the refinement and uniform distribution of hydration products; 4. Improving the structure of the interfacial transition zone (ITZ) and enhancing the strength of the fiber-matrix interface.

[0037] III. Multi-scale Fiber Toughening System The core innovation of this invention lies in the construction of a three-level multi-scale fiber synergistic toughening system consisting of "macrofibers + microfibers + nanofibers". Fibers of different scales play a synergistic role during material stress: nanofibers (diameter 20-200 nm): inhibit microcrack initiation at the nanoscale; microfibers (diameter 5-20 μm): hinder microcrack propagation at the micrometer scale; macrofibers (diameter 40-200 μm): bridge visible cracks at the macroscale, providing the main toughness contribution.

[0038] 3.1 Macroscopic Fiber System (Total Dosage 1.5-2.5 vol%) A. Polyvinyl Alcohol Fiber (PVA Fiber). Dosage: 0.8-1.2 vol% (preferably 1.0 vol%); Specifications: Diameter 40 μm, Length 12 mm, Aspect Ratio 300; Tensile Strength: 1600 MPa; Elastic Modulus: 42 GPa; Surface Modification: Impregnation in 5% PVA solution for 30 minutes; Function: PVA fiber has a moderate elastic modulus, good compatibility with cement matrix, and high energy dissipation during pull-out, making it a key fiber for achieving strain hardening.

[0039] B. Basalt fiber. Dosage: 0.4-0.8 vol% (preferably 0.6 vol%); Specifications: Diameter 13 μm, length 18 mm, aspect ratio 1385; Tensile strength: 4200 MPa; Elastic modulus: 95 GPa; Surface modification: Plasma treatment for 10 minutes; Function: High strength, high modulus, effectively limits crack propagation, improves tensile strength and early strength, high temperature and corrosion resistance.

[0040] C. Steel fiber (fine type). Dosage: 0.3-0.5 vol% (preferably 0.4 vol%); Specifications: Diameter 0.2 mm, length 13 mm, aspect ratio 65; Tensile strength: 2850 MPa; Surface modification: sandpaper polishing to remove rust and improve roughness; Function: High-strength steel fibers can maintain bridging effect even when the crack width is large, significantly improving ultimate toughness and impact resistance.

[0041] Synergistic mechanism: PVA fibers dominate the strain hardening stage, generating multiple fine cracks; basalt fibers control the crack spacing and width, improving tensile strength; steel fibers provide residual load-bearing capacity during the large deformation stage, preventing sudden failure.

[0042] 3.2 Micro / Nanofiber System D. Nanocellulose Fiber. Dosage: 0.05-0.1 vol% (preferably 0.08 vol%); Specifications: Diameter 20-50 nm, Length 5-20 μm; Source: Mechanical grinding of wood pulp fibers + acid hydrolysis; Function: Reinforces cement paste at the nanoscale, inhibits early microcrack formation, improves interfacial transition zone, and enhances matrix toughness.

[0043] E. Carbon nanofibers. Dosage: 0.02-0.05 vol% (preferably 0.03 vol%); Specifications: Diameter 100-200 nm, length 50-100 μm; Function: Ultra-high strength (tensile strength > 3500 MPa), bridging microcracks at the nano-micro scale, significantly improving fracture toughness.

[0044] Dispersion technique: Micro- and nanofibers are pre-mixed with a 0.5% carboxymethyl cellulose (CMC) aqueous solution; ultrasonically dispersed (frequency 20kHz, power 500W, time 10 minutes); then added to a mixer after mixing with a water-reducing agent solution.

[0045] IV. Interface Reinforcement Technology: The key to the fiber reinforcement effect lies in the bond strength at the fiber-matrix interface. An excessively weak interface leads to fiber pull-out, failing to fully realize its reinforcing effect; an excessively strong interface leads to fiber breakage, limiting the improvement in toughness. This invention optimizes the interface strength through surface modification technology.

[0046] 4.1 Interface Reinforcing Agent Silane Coupling Agent (KH-550): Dosage: 1.5-2.5 parts (preferably 2.0 parts); Chemical Name: γ-aminopropyltriethoxysilane. Mechanism of Action: After hydrolysis, the ethoxy group forms Si-O-Si bonds with cement hydration products; the amino group forms hydrogen bonds or covalent bonds with the fiber surface; molecular bridges are formed on the fiber surface, enhancing interfacial adhesion.

[0047] 4.2 Fiber Surface Modification Methods: PVA Fiber Modification: Impregnation Solution: 5% Polyvinyl Alcohol (PVA) Aqueous Solution; Impregnation Time: 30 minutes; Drying: 60°C Oven, 2 hours. Principle: PVA coating increases fiber surface roughness and has good affinity with cement matrix, improving interfacial adhesion. Basalt Fiber Modification: Method: Low-temperature plasma surface treatment; Parameters: Air plasma, power 200W, treatment time 10 minutes; Principle: Plasma etching of fiber surface increases surface roughness and active groups, improving wettability.

[0048] Steel fiber modification: Method: mechanical grinding + pickling; Process: grinding with 600-grit sandpaper → soaking in 5% hydrochloric acid solution for 5 minutes → rinsing with clean water → drying; Principle: removing surface rust and oil stains, increasing surface roughness, and improving mechanical interlocking force.

[0049] Fifth, the high fiber content in ultra-high water-reducing systems significantly increases system viscosity and reduces fluidity. This invention addresses this contradiction by employing a novel water-reducing system.

[0050] Third-generation polycarboxylate superplasticizer: Dosage: 5-7 parts (preferably 6 parts, accounting for the mass of cementitious materials); Water reduction rate: ≥45%; Molecular structure: Long side chains, high grafting density, comb-like structure. Function: Disperses cement particles through steric hindrance and electrostatic repulsion, significantly reducing the water-cement ratio while maintaining high fluidity.

[0051] Viscosity modifier (konjac glucomannan): Dosage: 0.1-0.3 parts (preferably 0.2 parts). Function: Improves the cohesiveness of the slurry, prevents fiber sedimentation and slurry floating; improves rheological properties, giving the slurry thixotropic properties; improves water retention and reduces bleeding.

[0052] VI. Expansion and contraction compensation system: Sleeve grouting requires early micro-expansion of the material to compensate for contraction, ensuring close contact between the reinforcing steel, sleeve, and grout.

[0053] UEA Expanding Agent: Dosage: 10-15 parts (preferably 12 parts); Main components: calcium sulfoaluminate, calcium oxide. Function: Hydration produces ettringite (AFt) and calcium hydroxide, resulting in expansion and compensating for shrinkage.

[0054] Aluminum sulfate shrinkage compensator: Dosage: 2-4 parts (preferably 3 parts). Function: Promotes early formation of ettringite and enhances early expansion.

[0055] Polyacrylic acid shrinkage reducing agent: Dosage: 1-2 parts (preferably 1.5 parts). Function: Reduces the surface tension of porous liquids and reduces shrinkage caused by capillary tension.

[0056] Synergistic effect: 3-hour vertical expansion rate: 0.05-0.15% (meets the standard range of 0.02-2%); 1-day vertical expansion rate: 0.025-0.035%; 28-day total shrinkage rate: <0.01%; bleeding rate: 0% (meets the standard requirements); ensures no gap between the rebar and the sleeve, and a bond strength ≥50Mpa.

[0057] VII. Fiber Dispersion Technology (Key Process) Uniform fiber dispersion is a prerequisite for the toughening effect of fibers. This invention develops a four-step dispersion process of "dry premixing + batch addition + high-shear stirring + ultrasonic assistance".

[0058] 7.1 Purpose of the dry mixing premixing stage: to premix the fibers with the aggregates and some additives, to initially disperse them, and to avoid the fibers from directly contacting water and agglomerating during the subsequent wet mixing.

[0059] Process: Mix quartz powder, aggregate (fine sand), a portion of water-reducing agent powder (1 / 3 of the amount), expansion agent, and defoamer; stir at low speed for 5 minutes (100-150 rpm); Function: The dry powder particles are adsorbed onto the fiber surface to form a protective layer and prevent fiber agglomeration.

[0060] 7.2 Sequence of batch addition: 1. First batch: Add macro fibers (PVA fiber, basalt fiber, steel fiber). Continue mixing with the dry mix for 5 minutes to allow the macro fibers to be initially dispersed in the aggregate.

[0061] 2. Second batch: Add microfibers (cellulose nanofibers, carbon nanofibers). Add in aqueous solution (pre-dispersed ultrasonically); mix for 3 minutes. Principle: Adding in batches avoids entanglement of fibers of different sizes, ensuring uniform dispersion.

[0062] 7.3 High-shear mixing stage equipment: High-shear mixer or planetary mixer parameters: Speed: 500-800 rpm (preferably 650 rpm); Time: 15-20 minutes (preferably 18 minutes); Blade type: Dispersion blade + anchor blade.

[0063] Functions: Strong shear force breaks down fiber aggregates; allows fibers to be randomly distributed in three dimensions in the slurry; promotes full wetting and contact between the fiber surface and the matrix.

[0064] 7.4 Ultrasonic Assisted Stage Parameters: Frequency: 20kHz; Power: 500W; Time: 2 minutes; Probe Diameter: 20mm.

[0065] Functions: Ultrasonic cavitation effect generates microjets and shock waves; further disperses nanofibers and microfibers; improves fiber surface wettability; and makes fiber dispersion more uniform.

[0066] Precautions: The ultrasound time should not be too long, otherwise it may damage the fibers or cause a temperature rise; intermittent ultrasound (working for 2 seconds and stopping for 1 second) is more effective.

[0067] VIII. Complete preparation method process Step 1: Fiber pretreatment (to be completed 1 day in advance).

[0068] PVA fiber pretreatment: 1. Prepare a 5% PVA aqueous solution (polyvinyl alcohol: water = 5:95, mass ratio); 2. Heat to 80°C and stir until completely dissolved, then cool to room temperature; 3. Immerse the PVA fiber in the solution for 30 minutes; 4. Remove and drain, then place in a 60°C oven to dry for 2 hours; 5. Cool to room temperature and store in a sealed container.

[0069] Basalt fiber pretreatment: 1. Lay the basalt fiber flat on the plasma treatment table; 2. Turn on the air plasma generator with a power of 200W; 3. Treatment time is 10 minutes, and the distance from the fiber surface is 10cm; 4. Use immediately after treatment to avoid surface activity decay.

[0070] Steel fiber pretreatment: 1. Grind the surface of the steel fiber with 600-grit sandpaper to remove rust and oil; 2. Immerse in 5% hydrochloric acid solution for 5 minutes to further remove rust; 3. Rinse thoroughly with clean water and dry; 4. Check the surface roughness and use only if it meets the requirements.

[0071] Micro / nanofiber pre-dispersion: 1. Mix nanocellulose and carbon nanofibers in a certain proportion; 2. Add 0.5% CMC (carboxymethyl cellulose) aqueous solution; 3. Ultrasonic dispersion: frequency 20kHz, power 500W, time 10 minutes; 4. Obtain the fiber suspension for step 2: dry mixing stage (10 minutes).

[0072] 1. Add P.O62.5 cement, nano silica fume, ultrafine quartz powder, and nano calcium carbonate to the mixer; 2. Add fine sand (particle size <1.18mm, continuous gradation); 3. Add 1 / 3 of the water-reducing agent powder, expanding agent, aluminum sulfate, and defoamer; 4. Mix at low speed (100-150rpm) for 10 minutes until uniform.

[0073] Step 3: Fiber addition stage (8 minutes).

[0074] First stage (5 minutes): 1. Weigh the pretreated PVA fiber, basalt fiber, and steel fiber according to the proportion; 2. Slowly add them to the mixer (addition time 1 minute); 3. Stir at low speed for 5 minutes to initially disperse the fibers.

[0075] Second stage (3 minutes): 1. Add silane coupling agent (KH-550) to the mixer; 2. Slowly add micro / nano fiber suspension while stirring; 3. Continue stirring for 3 minutes.

[0076] Step 4: High-shear wet mixing stage (13 minutes).

[0077] 1. Premix water (water-to-binder ratio 0.16-0.18, preferably 0.17) with the remaining 2 / 3 of the polycarboxylate superplasticizer and konjac glucomannan; 2. Start high-shear mode (500-800 rpm); 3. Quickly add the water + superplasticizer mixture (addition time 30 seconds); 4. Stir at high shear for 10 minutes; 5. Add shrinkage reducing agent; 6. Continue stirring for 3 minutes.

[0078] Step 5: Ultrasonic-assisted dispersion phase (2 minutes).

[0079] 1. Insert the ultrasonic probe (frequency 20kHz, power 500W) into the middle of the slurry; 2. Intermittent ultrasound: work for 2 seconds, stop for 1 second; 3. Total time: 2 minutes; 4. Move the probe slowly during the ultrasound process to ensure that the entire slurry is treated with ultrasound.

[0080] Step 6: Let stand and test (5 minutes).

[0081] 1. Let stand for 2 minutes to eliminate air bubbles introduced by stirring; 2. Test the flowability (using the slump test or slump cone test); 3. Target: initial flowability 340-380 mm; 4. If the flowability is insufficient, fine-tune the water-reducing agent or water volume (adjustment amount <2%).

[0082] Step 7: Grouting construction (operation time window 40 minutes).

[0083] A. Gravity grouting method: 1. Fix the sleeve vertically and insert the reinforcing bar into place. 2. Slowly inject grout from the grouting hole. 3. Observe the grout outlet carefully. Stop when grout comes out of the outlet and the concentration is the same as that of the inlet. 4. Seal the grouting hole and the grout outlet.

[0084] B. Pumping grouting method (suitable for high-level or batch construction): 1. Load the grouting material into the grouting pump. 2. Pumping pressure: 0.3-0.5MPa. 3. Pumping speed: 2-4L / min. 4. Continuous pumping during the grouting process to avoid interruption.

[0085] C. Vibration Assistance (Optional, for improving compaction): 1. Apply vibration to the outside of the sleeve after grouting. 2. Vibration parameters: frequency 50Hz, amplitude 5mm, time 30 seconds. 3. Promote the filling of all voids in the sleeve with grout and remove residual air bubbles.

[0086] IX. Key Parameter Optimization Table 1 is the key parameter optimization table.

[0087]

[0088] 10. Mechanism of action of the technical solution 10.1 Multi-scale synergistic toughening mechanism Nanoscale (10-100nm): Nanocellulose and carbon nanofibers form a nanoscale reinforcing network inside the cement gel; inhibit the initiation of nanocracks and enhance the cohesion of the matrix; improve the structure of the interfacial transition zone (ITZ) and reduce microscopic defects.

[0089] Micrometer scale (1-100μm): Basalt fibers (13μm in diameter) bridge microcracks at the micrometer scale; limit microcrack propagation, reduce crack spacing; and improve the tensile strength of the matrix.

[0090] Macroscale (>100μm): PVA fibers and steel fibers play a bridging role in macroscopic cracks; during crack propagation, the fibers are gradually pulled out, continuously dissipating energy; achieving strain hardening: when strain increases, the stress does not decrease but increases, forming multiple fine cracks.

[0091] 10.2 Path to Strain Hardening Behavior Traditional Concrete: Single Crack Propagation → Stress Concentration → Brittle Fracture.

[0092] The material of this invention has the following characteristics: uniform distribution of multiple cracks → stress dispersion → strain hardening → high toughness.

[0093] Strain hardening conditions: 1. Fiber bridging stress σ > matrix cracking stress σ0 2. Fiber content is high enough (Vf > 1.5%) 3. Fiber-matrix interface bonding is moderate (able to transmit force and dissipate pull-out energy).

[0094] The implementation of this invention is as follows: PVA fiber: elastic modulus of 42 GPa, which is close to that of cement matrix (30-40 GPa), and the interfacial bonding is moderate; high dosage: total fiber content 1.5-2.5 vol%, PVA fiber 0.8-1.2 vol%; interface optimization: PVA impregnation treatment, silane coupling agent reinforcement, to achieve a "moderate" interface.

[0095] Typical stress-strain curve characteristics: 1. Elastic stage (strain <0.01%): linear relationship, E=40-45GPa 2. Crack initiation stage (strain 0.01-0.2%): the first crack forms, and the stress reaches σ0≈8MPa 3. Strain hardening stage (strain 0.2-3%): multiple cracks form, and the stress continues to rise to σmax≈25MPa 4. Strain softening stage (strain >3%): the main controlling crack expands, the stress decreases, but still maintains a high residual strength (>15MPa) 5. Ultimate strain: 3-5% (ordinary concrete <0.02%) 10.3 Ultra-high strength realization mechanism: dense filling: multi-level filling of nano-silica fume, ultrafine quartz powder, and nano-calcium carbonate; porosity reduced to <3% (ordinary concrete 12-15%); dense structure, and significantly improved strength.

[0096] Volcanic ash effect: Nano-SiO2 + Ca(OH)2 → CSH gel (high-strength hydration product); consumes alkaline substances and reduces the orientation weakness of Ca(OH)2 crystals in the interfacial transition zone.

[0097] Fiber reinforcement: Fibers provide secondary stress transmission paths; inhibit microcrack propagation and delay strength loss.

[0098] Low water-cement ratio: W / B=0.16-0.18, far lower than ordinary concrete (0.4-0.6); high-performance water-reducing agent ensures high fluidity under low water-cement ratio.

[0099] Results: 24-hour compressive strength ≥90 MPa; 28-day compressive strength ≥160 MPa; 28-day flexural strength ≥25 MPa.

[0100] XI. Summary Table 2 is a summary table of technical effects.

[0101]

[0102] Note: The standard only specifies the basic strength and flowability indicators. This invention, while meeting the standard, significantly improves key safety indicators not covered by the standard, such as toughness, durability, and seismic performance. It achieves ultra-high toughness while maintaining construction flowability, which is the core technological breakthrough of this invention.

[0103] Key technical points of this invention: Key point 1: Construction of a multi-scale fiber synergistic toughening system. Through the composite of macro-fibers (PVA fiber 0.8-1.2 vol%, basalt fiber 0.4-0.8 vol%, steel fiber 0.3-0.5 vol%), micro-fibers (nanocellulose 0.05-0.1 vol%), and nanofibers (carbon nanofibers 0.02-0.05 vol%), synergistic suppression of cracks at different scales is achieved, endowing the material with strain hardening characteristics.

[0104] Unlike existing technologies using single fibers or low-dosage fibers, the multi-scale fiber system of this invention achieves three levels of protection: "nanoscale inhibition of initiation, microscale inhibition of propagation, and macroscopic bridging of cracks," which is the core of achieving ultra-high toughness.

[0105] Key Point 2: Fiber Surface Modification and Interface Reinforcement Technology. PVA solution impregnation of PVA fibers, plasma surface treatment of basalt fibers, and mechanical polishing of steel fibers, combined with the interface bridging effect of silane coupling agent (KH-550, dosage 1.5-2.5 parts), enable the fiber-matrix interface bonding strength to reach the optimal value.

[0106] Achieving "moderate" interfacial strength is crucial for strain hardening: if the interface is too weak, fibers are easily pulled out and cannot transfer stress; if the interface is too strong, fibers break directly and cannot dissipate energy through pull-out. This invention optimizes interfacial strength by precisely controlling surface modification conditions.

[0107] Key Point 3: The efficient fiber dispersion process uses a four-step dispersion technology of "dry premixing + batch addition + high shear stirring (500-800 rpm, 15-20 min) + ultrasonic assistance (20 kHz, 500 W, 2 min)" to solve the problem of uniform dispersion under high fiber content.

[0108] The innovation of this process lies in: dry premixing coats the fiber surface with aggregate powder to prevent agglomeration during wet mixing; batch addition avoids the entanglement of fibers of different sizes; high shear stirring provides strong shear force to break up fiber clumps; and ultrasonic assistance further disperses nanofibers to improve microstructure distribution. Key point 4: Ultra-high performance cementitious system design. The combination of P.O62.5 cement (100 parts) + nano silica fume (20-30 parts) + ultrafine quartz powder (30-40 parts) + nano calcium carbonate (5-8 parts) achieves ultra-high strength (compressive strength ≥160MPa) and ultra-low porosity (<3%) of the matrix through the triple effect of "filling + volcanic ash + crystal nucleation".

[0109] The high doping content of nano-silica fume (20-30%, far higher than the conventional 5-15%) is the key to achieving ultra-high performance, and it is also an important difference between this invention and existing technologies.

[0110] Key Point 5: High Fiber Content Flowability Maintenance Technology. Using third-generation polycarboxylate superplasticizer (water reduction rate ≥45%, dosage 5-7 parts) and konjac glucomannan viscosity modifier (0.1-0.3 parts), the initial flowability is maintained at 340-380 mm under the condition of total fiber content of 1.5-2.5 vol%, which meets the requirements of sleeve grouting construction.

[0111] The introduction of konjac glucomannan is a key innovation: it not only improves the cohesiveness of the slurry to prevent fiber sedimentation, but also improves the rheology and imparts thixotropic properties to the slurry, making the material have high viscosity when at rest (to maintain its shape) and low viscosity when subjected to shear (to flow easily).

[0112] Example 1: High-toughness formulation (toughness priority) Raw material ratio (by weight): P.O62.5 cement: 100 parts; Nano silica fume: 25 parts; Ultrafine quartz powder: 35 parts; Nano calcium carbonate: 6 parts; Fine sand (<1.18mm): 80 parts; Polycarboxylate superplasticizer: 6 parts; Konjac glucomannan: 0.2 parts; UEA expansion agent: 12 parts; Aluminum sulfate: 3 parts; Shrinkage reducing agent: 1.5 parts; Silane coupling agent: 2.0 parts; Water: 28 parts (water-binder ratio 0.17); Fiber ratio (by volume) (Fractions): PVA fiber: 1.2 vol%; Basalt fiber: 0.6 vol%; Steel fiber: 0.4 vol%; Nanocellulose: 0.08 vol%; Carbon nanofiber: 0.03 vol%; Total fiber content: 2.23 vol%; Performance test results: Initial flowability: 365 mm; 24h compressive strength: 95 MPa; 28d compressive strength: 165 MPa; 28d flexural strength: 27 MPa; Flexural toughness index I5: 35; Fracture energy: 23 kJ / m 2 Impact resistance energy: 165J.

[0113] Example 2: Strength-Toughness Balanced Formula (Excellent Overall Performance) Raw Material Ratio (by weight): P.O62.5 cement: 100 parts; Nano silica fume: 28 parts; Ultrafine quartz powder: 38 parts; Nano calcium carbonate: 7 parts; Fine sand: 75 parts; Polycarboxylate superplasticizer: 6.5 parts; Konjac glucomannan: 0.25 parts; UEA expanding agent: 13 parts; Aluminum sulfate: 3.5 parts; Shrinkage reducing agent: 1.8 parts; Silane coupling agent: 2.2 parts; Water: 27 parts (water-binder ratio 0.16); Fiber Ratio: PVA fiber: 1.0 vol%; Basalt fiber: 0.7 vol%; Steel fiber: 0.45 vol%; Nanocellulose: 0.09 vol%; Carbon nanofiber: 0.04 vol%; Total fiber content: 2.28 vol%.

[0114] Performance test results: Initial flowability: 355 mm; 24-hour compressive strength: 102 MPa; 28-day compressive strength: 175 MPa; 28-day flexural strength: 26 MPa; flexural toughness index I5: 32; fracture energy: 21 kJ / m 2 Impact energy: 158J; Fatigue life (2 million cycles) strength retention rate: 93%.

[0115] Example 3: Ultra-high strength formula (strength priority) Raw material ratio (by weight): P.O62.5 cement: 100 parts; Nano silica fume: 30 parts; Ultrafine quartz powder: 40 parts; Nano calcium carbonate: 8 parts; Fine sand: 70 parts; Polycarboxylate superplasticizer: 7 parts; Konjac glucomannan: 0.3 parts; UEA expanding agent: 15 parts; Aluminum sulfate: 4 parts; Shrinkage reducing agent: 2 parts; Silane coupling agent: 2.5 parts; Water: 26 parts (water-binder ratio 0.15); Fiber ratio: PVA fiber: 0.9 vol%; Basalt fiber: 0.8 vol%; Steel fiber: 0.5 vol%; Nanocellulose: 0.1 vol%; Carbon nanofiber: 0.05 vol%; Total fiber content: 2.35 vol%.

[0116] Performance test results: Initial flowability: 348 mm; 24h compressive strength: 108 MPa; 28d compressive strength: 182 MPa; 28d flexural strength: 25 MPa; flexural toughness index I5: 30; fracture energy: 20 kJ / m 2 .

[0117] Table 3 shows the advantages of this invention compared to existing technologies.

[0118]

[0119] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A high-performance fiber-reinforced sleeve grouting material, characterized in that: It includes, by weight, 100 parts of P.O62.5 ordinary silicate cement, 20-30 parts of nano silica fume, 30-40 parts of ultrafine quartz powder, 5-8 parts of nano calcium carbonate, 1.5-2.5 parts of silane coupling agent, 5-7 parts of third-generation polycarboxylate superplasticizer, 0.1-0.3 parts of viscosity modifier, 10-15 parts of UEA expansion agent, 2-4 parts of aluminum sulfate shrinkage compensator, and 1-2 parts of polyacrylic acid shrinkage reducing agent; it also includes a multi-scale fiber system with a volume content of 1.5-2.5 vol%; the multi-scale fiber system includes 0.8-1.2 vol% polyvinyl alcohol fiber, 0.4-0.8 vol% basalt fiber, 0.3-0.5 vol% steel fiber, 0.05-0.1 vol% nanocellulose fiber, and 0.02-0.05 vol% carbon nanofiber.

2. The ultra-high performance fiber-reinforced sleeve grouting material according to claim 1, characterized in that: The amount of nano-silica fume is 25 parts, the amount of ultrafine quartz powder is 35 parts, and the amount of nano-calcium carbonate is 6 parts.

3. The ultra-high performance fiber-reinforced sleeve grouting material according to claim 1, characterized in that: The volume fraction of polyvinyl alcohol fiber is 1.0 vol, the volume fraction of basalt fiber is 0.6 vol, and the volume fraction of steel fiber is 0.4 vol.

4. A method for preparing an ultra-high performance fiber-reinforced sleeve grouting material, using the ultra-high performance fiber-reinforced sleeve grouting material according to any one of claims 1 to 3, characterized in that: Includes the following steps: S1: Fiber pretreatment: Polyvinyl alcohol fiber, basalt fiber, and steel fiber were surface modified respectively; Nanocellulose and carbon nanofibers were ultrasonically dispersed in a 0.5% carboxymethyl cellulose aqueous solution; S2: Dry premixing: Mix the cementitious material, aggregate, 1 / 3 of the water-reducing agent, and expanding agent, and stir at low speed; S3: Batch addition of fibers: First add macro-fibers and stir, then add interface reinforcing agent and micro / nano-fiber suspension and stir; S4: High-shear wet mixing: Add water and the remaining water-reducing agent and viscosity modifier mixture, stir at high shear, add shrinkage reducing agent and continue stirring; S5: Ultrasonic-assisted dispersion: Use an ultrasonic probe for intermittent ultrasonication; S6: Static test: Let stand for a certain period of time and test the flowability.

5. The method for preparing an ultra-high performance fiber-reinforced sleeve grouting material according to claim 4, characterized in that: It also includes a fiber surface modification method: after impregnating polyvinyl alcohol fibers with a 5% polyvinyl alcohol aqueous solution for 30 minutes, they are dried at 60°C for 2 hours; Basalt fiber is surface treated with low-temperature plasma (power 200W) for 10 minutes; steel fiber is sanded with 600-grit sandpaper and soaked in 5% hydrochloric acid solution for 5 minutes to remove rust.

6. The method for preparing an ultra-high performance fiber-reinforced sleeve grouting material according to claim 4, characterized in that: In step S4, the water-to-glue ratio is 0.16-0.

18.

7. The method for preparing an ultra-high performance fiber-reinforced sleeve grouting material according to claim 4, characterized in that: In step S4, the high-shear stirring speed is 650 rpm and the stirring time is 18 min.

8. The method for preparing an ultra-high performance fiber-reinforced sleeve grouting material according to claim 4, characterized in that: When using ultra-high performance fiber-reinforced sleeve grouting material for grouting construction, vibration is applied with a frequency of 50Hz, an amplitude of 5mm, and a duration of 30 seconds.

9. The method for preparing an ultra-high performance fiber-reinforced sleeve grouting material according to claim 4, characterized in that: The high-performance fiber-reinforced sleeve grouting material obtained meets the following properties: 1-day compressive strength ≥60MPa, 3-day compressive strength ≥85MPa, 24-hour compressive strength ≥90MPa, 28-day compressive strength ≥160MPa, 28-day flexural strength ≥25MPa, initial flowability 320-360mm, 30-minute flowability ≥300mm, bleeding rate 0%, 3-hour vertical expansion rate 0.05-0.15%, flexural toughness index I5 and I10 both ≥30, fracture energy ≥20kJ / m2, ultimate tensile strain 3-5%, impact energy ≥150J, fatigue life strength retention rate ≥90%, steel bar bond strength ≥50MPa, sleeve-grouting material bond strength ≥40MPa, freeze-thaw cycle resistance ≥300 cycles.

10. A method for applying an ultra-high performance fiber-reinforced sleeve grouting material, comprising using the ultra-high performance fiber-reinforced sleeve grouting material according to any one of claims 1 to 3, characterized in that: Ultra-high performance fiber-reinforced sleeve grouting material is used in prefabricated buildings in high-intensity earthquake zones, prefabricated structures subjected to dynamic or fatigue loads, steel reinforcement connections in important structural parts, and prefabricated building projects requiring high safety reserves and toughness.

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