Nano-silica sol two-component concrete repairing material, preparation method and application thereof

Abstract

The application provides a nano-silica sol two-component concrete repair material and a preparation method and application thereof, the repair material comprises a liquid material component A and a powder material component B, and the mass ratio of the two is 1: (2.5-3.5), the two components are stored separately, and are mixed in real time when used. Through nano-silica sol thickening, thixotropy control and powder material grading optimization, the slurry after mixing has excellent thixotropy and stable extrudability, and the initial flowability is adjustable in the range of 160-180 mm. Through real-time scanning of working condition details by an intelligent sensing and control system, and intelligent matching of material ratio and process parameters, the repair material can better adapt to different defect morphologies, structural curvatures and bearing requirements, significantly improves the accuracy, adaptability and overall performance reliability of repair, and provides a complete and self-adaptive material and process solution for automatic and intelligent efficient repair of tunnels, culverts and other narrow and high-risk spaces.

Description

Technical Field

[0001] This invention belongs to the field of concrete repair materials and intelligent construction technology, specifically relating to a two-component nano-silica sol concrete repair material, its preparation method, and its application. Background Technology

[0002] Concrete lining structures such as tunnels, culverts, and water conservancy facilities are prone to spalling, cracks, and honeycomb-like defects during long-term use. Furthermore, the working conditions vary significantly across different defect areas; for example, defective areas may exhibit curved or flat shapes, with variations in morphology, depth, and width. Traditional manual repair methods suffer from high-risk high-altitude operations, low construction efficiency, significant traffic disruption, and reliance on worker skill for repair quality. In recent years, 3D printing technology has developed rapidly in the construction field, but its application in the repair of existing structures, particularly vertical surfaces and arches, still faces challenges. Drones, as flexible aerial platforms, offer the possibility of non-contact 3D printing in complex spaces.

[0003] However, existing repair mortars or concrete materials are difficult to directly apply to lightweight, low-flow printing systems carried by drones. Single-component quick-repair mortars often prematurely set and clog the drone's delivery pipes, while ordinary two-component repair materials suffer from slow early strength development, easy sagging, and lack the ability to dynamically adjust for different working conditions. More importantly, existing materials lack core functional components to simultaneously achieve controllable setting, improved early strength, enhanced adhesion, and optimized thixotropy, making it difficult to meet the comprehensive performance requirements of drone 3D printing. Summary of the Invention

[0004] The purpose of this invention is to provide a two-component nano-silica sol concrete repair material, which solves the above-mentioned technical problems in the prior art and is suitable for rapid, accurate and efficient repair of different defects on the surface of structures such as tunnels and culverts.

[0005] Therefore, the technical solution provided by the present invention is as follows:

[0006] The nano-silica sol two-component concrete repair material includes liquid component A and powder component B, with a mass ratio of 1:(2.5~3.5). Liquid component A and powder component B are stored separately and mixed immediately before use.

[0007] The liquid component A is composed of the following raw materials in parts by weight: 20-35 parts water, 30-50 parts nano silica sol, 10-25 parts polymer emulsion, 0.1-0.5 parts retarder, and 0.1-0.3 parts defoamer.

[0008] The powder component B is composed of the following raw materials in parts by weight: 40-60 parts cement, 10-20 parts mineral admixtures, 20-35 parts quartz sand, 3-8 parts quick-setting agent, 0.5-1.5 parts water-reducing agent, 0.05-0.1 parts cellulose ether, and 1-3 parts redispersible latex powder.

[0009] The repair material of this invention uses nano-silica sol as the core functional component, and through the synergistic effect of other components, it achieves the basic comprehensive properties of "instant mixing and setting", rapid setting and early strength, high adhesion, anti-sagging, and easy extrusion.

[0010] Furthermore, the mass content of SiO2 in the nano-silica sol is 20%~30%, the average particle size is 10~30nm, and the pH value is 9~11.

[0011] The nano-silica sol plays the following roles in the system:

[0012] (1) Setting regulation effect: The highly active nano-sized SiO2 particles provided by the nano silica sol can work synergistically with the quick-setting agent in the powder component to accelerate the cement hydration process, promote the rapid generation of hydration products, and achieve controllable initial setting within 5 to 15 minutes after extrusion, which avoids sagging and ensures the operating window period; at the same time, it forms a balanced system with the retarder to precisely control the setting time and eliminate the problems of premature setting or slow setting.

[0013] (2) Strength enhancement effect: Through the secondary pozzolanic effect, nano-SiO2 particles react with cement hydration product Ca(OH)2 to generate more dense CSH gel, which fills the internal pores of cement stone, significantly improving the early strength (1-hour strength ≥1.5MPa) and later strength (28-day compressive strength ≥55MPa) of the material; at the same time, the micro-filling effect of nanoparticles optimizes the internal structure of the slurry, reduces porosity, and enhances density and durability.

[0014] (3) The high specific surface area and surface activity of nano-silica sol can form a strong chemical bond and physical adsorption between the old concrete substrate and the repair material interface. Combined with the film-forming effect of polymer emulsion, it can significantly improve the wet bonding strength (≥2.0MPa) and ensure that the repair body and the substrate are stressed together.

[0015] (4) Thixotropy and extrusion stability control: Nano silica sol, emulsion and latex powder form a three-dimensional network structure in the slurry. When standing, the viscosity of the system is increased to prevent collapse and sagging during vertical / elevation printing. The network structure is destroyed under shearing action, and the viscosity is reduced, which facilitates the small-diameter conveying and extrusion of the UAV. The network structure recovers quickly after extrusion to ensure the shape stability of the printed lines and achieve precise molding.

[0016] (5) Volume stabilization effect: The densification effect of CSH gel and the filling effect of nanoparticles effectively inhibit the drying shrinkage and plastic shrinkage of cement stone, reduce the risk of cracking, ensure the volume stability of the repair body, and work together with the original structure for a long time.

[0017] Furthermore, the polymer emulsion is selected from at least one of acrylate emulsion, styrene-acrylic emulsion, and epoxy emulsion, and has a solid content of 40% to 50%.

[0018] The role of polymer emulsions is to form an organic polymer film network inside the repair material, which significantly improves the material's bonding strength, flexibility, crack resistance, and impermeability. Different types of polymer emulsions and their dosages can be selected and adjusted according to the working conditions.

[0019] Furthermore, the retarder is selected from at least one of sodium gluconate, citric acid, and tartaric acid.

[0020] The retarder, in combination with nano silica sol and accelerator, precisely regulates the setting time of the slurry, ensuring sufficient working time. The dosage can be dynamically adjusted according to working conditions to optimize setting performance.

[0021] In some specific embodiments, the defoamer is a silicone defoamer or a polyether defoamer.

[0022] In some specific embodiments, the cement is silicate cement with a strength grade of 42.5 or 52.5, and the appropriate cement strength grade can also be selected according to the strength requirements of the area to be repaired.

[0023] Furthermore, the mineral admixture is composed of spherical fly ash microspheres and silica fume in a mass ratio of (0.5~2):1, wherein the particle size of the spherical fly ash microspheres is 1~10μm and the particle size of the silica fume is 0.1~0.3μm.

[0024] Fly ash microspheres act as ball bearing lubricants, improving fluidity; silica fume and nano silica sol work synergistically to exert the pozzolanic effect and micro-aggregate filling effect, significantly improving later strength and durability. The compounding ratio and total dosage can be adjusted according to working conditions.

[0025] In some specific embodiments, the fineness of the quartz sand is 40~100 mesh. As an aggregate, it optimizes the slurry gradation and, together with the filling effect of nano-silica sol, improves the density and packing stability of the system. Different fineness of quartz sand and the dosage can be selected and adjusted according to the working conditions.

[0026] The accelerator is an aluminate-based or alkali-free liquid accelerator in powder form, which works synergistically with nano-silica sol to ensure rapid coagulation upon contact with liquid material. The dosage can be adjusted according to working conditions to meet different coagulation rate requirements.

[0027] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate of over 28%. It ensures high fluidity and low water consumption of the slurry at extremely low dosage. The thickening effect of the nano-silica sol forms a balance and optimizes the extrusion performance. The dosage can be adjusted slightly according to the working conditions to optimize the flow and extrusion performance.

[0028] Furthermore, the cellulose ether is hydroxypropyl methylcellulose with a viscosity of 100,000 to 150,000 mPa·s.

[0029] Cellulose ethers and nano-silica sols work synergistically to provide the slurry with water retention, thickening and thixotropy, further improving printing stability. The dosage can be adjusted according to working conditions.

[0030] Furthermore, the redispersible latex powder is an ethylene-vinyl acetate copolymer or a vinyl acetate-vinyl tert-carbonate copolymer latex powder.

[0031] After redispersible latex powder emulsifies with water, it works synergistically with polymer emulsions and nano-silica sols to further enhance adhesion and cohesion. Different types and dosages can be selected according to working conditions.

[0032] This invention also provides a method for preparing a two-component nano-silica sol concrete repair material, comprising the following steps:

[0033] Step 1) Preparation of liquid component A: Mix the prescribed amount of water and nano silica sol evenly, then add the prescribed amount of polymer emulsion, retarder, and defoamer while stirring. After stirring evenly, a uniform and stable suspension is formed. Immediately seal and package for later use.

[0034] Step 2) Preparation of powder component B: Mix the cement, mineral admixtures, quartz sand, quick-setting agent, water-reducing agent, cellulose ether, and redispersible latex powder in the prescribed amounts evenly and then pack them in a moisture-proof and sealed package.

[0035] This invention also provides an application of a nano-silica sol two-component concrete repair material in UAV 3D printing repair, comprising the following steps:

[0036] Step 1) Equipment preparation: Load the prepared liquid component A and powder component B into the dual storage tanks carried by the UAV respectively;

[0037] Step 2) Working condition scanning and information collection: The UAV flies to the area to be repaired and collects comprehensive working condition information of the area to be repaired using the onboard 3D laser scanning equipment or high-definition photogrammetry equipment;

[0038] The drone is equipped with an intelligent working condition identification and parameter adaptation system, which integrates a data acquisition module, a data analysis and processing module, a proportioning and process parameter decision module, and an execution control module.

[0039] Step 3) Working Condition Analysis and Parameter Decision: The data analysis and processing module performs 3D modeling, defect identification and quantitative analysis on the collected working condition information, and generates a detailed working condition assessment report. Then, the proportioning and process parameter decision module automatically determines the optimal composition ratio and process parameters of the repair material that are suitable for the current working condition based on the working condition assessment report, and transmits the decision instructions to the execution control module.

[0040] Step 4) Substrate treatment: The execution control module, according to the decision instructions, controls the drone or supporting equipment to clean the concrete lining substrate to be repaired;

[0041] Step 5) Material mixing and extrusion: According to the decision-made proportioning instructions, the execution control module controls the two-component precision metering pump to synchronously and accurately pump the liquid and powder materials into the mixing chamber according to the set ratio. The materials are then mixed at high speed and instantaneously in the chamber, and then extruded from the nozzle with a diameter of 3~5mm. The extrusion rate is precisely controlled according to the decision-made process parameters.

[0042] Step 6) Layered printing repair: Based on the process parameters determined by the proportioning and process parameter decision module in Step 3), layered printing repair is carried out until the entire repair body is constructed;

[0043] Step 7) Maintenance: After the construction is completed, spray the repaired area with water to keep it moist for at least 3 days, or cover it with a water-retaining film, and then allow it to grow naturally until the required age.

[0044] This invention provides a repair material adapted to an intelligent drone operating platform. It solves key technical challenges in drone 3D printing repair materials through the multifunctional synergistic effect of nano-silica sol. At the same time, it combines an intelligent adaptation system to achieve dynamic adjustment of material composition and process parameters, meeting diverse repair needs.

[0045] Furthermore, the optimal composition ratio of the repair material mentioned in step 3) includes the mixing mass ratio of liquid component A and powder component B, as well as the weight parts of each component of liquid component A and powder component B.

[0046] The process parameters mentioned in step 3) include printing path, printing layer thickness, line width, printing speed, flight height, and extrusion rate.

[0047] This invention combines an intelligent working condition recognition and parameter adaptation system. Based on the working condition information of the area to be repaired (including the three-dimensional shape, bending or flatness, morphology, depth, width, etc. of the area to be reinforced) obtained by UAV scanning, it automatically and intelligently adjusts the composition ratio and process parameters of the repair material. Ultimately, it provides an efficient preparation method and a complete UAV automated repair method that is closely coupled with material properties and working conditions.

[0048] The beneficial effects of this invention are as follows:

[0049] (1) With nano-silica sol as the core functional component, it adopts two-component separation storage and transportation, and mixes only at the moment of spraying, realizing "mixing and solidifying immediately". After contacting the substrate, it can quickly establish early strength (1h compressive strength ≥1.5MPa), which is conducive to interlayer bonding and continuous operation. It fundamentally eliminates the risk of single-component materials solidifying prematurely in the pipeline. At the same time, the multiple functions of nano-silica sol ensure that the comprehensive performance of the material meets the standards.

[0050] (2) The polymer emulsion in the liquid material and the redispersible latex powder in the powder material work together with nano silica sol to form an organic-inorganic interpenetrating polymer network in the cement stone matrix, which greatly improves the bonding strength (bonding strength ≥ 2.0 MPa), crack resistance and toughness of the material and the old concrete, and solves the problem of poor bonding and easy fall-off of traditional repair materials.

[0051] (3) The quick-setting agent in the powder and the nano silica sol in the liquid work together to achieve controllable rapid setting (adjustable initial setting time of 5-15 minutes) and early strength (compressive strength ≥25MPa in 24h); at the same time, through the secondary pozzolanic effect and micro-filling effect of ultrafine mineral admixtures and nano silica sol, the strength development of the repair body in the later stage is fully guaranteed, and the compressive strength in 28d is not less than 55MPa, which can match the performance of the original concrete structure well.

[0052] (4) Through thickening with nano-silica sol, thixotropic regulation, and powder gradation optimization, the mixed slurry exhibits excellent thixotropy and stable extrudability. Its initial flowability is adjustable within the range of 160-180 mm, making it ideal for stable material output and precise molding on aerial mobile platforms such as drones. The separate packaging greatly facilitates the carrying and resupply of drones. The entire system provides a complete material and process solution for the automated, intelligent, and efficient repair of narrow and high-risk spaces such as tunnels and culverts.

[0053] (5) This invention achieves a leap from "fixed formula" to "dynamic adaptation" by introducing an intelligent sensing and control system. By scanning in real time to obtain working condition details and intelligently matching material ratios and process parameters, the repair material can better adapt to different defect morphologies, structural curvatures and load-bearing requirements, significantly improving the accuracy, adaptability and overall performance reliability of the repair. It provides a complete and adaptive material and process solution for the automated, intelligent and efficient repair of narrow and high-risk spaces such as tunnels and culverts. Detailed Implementation

[0054] The following specific embodiments illustrate the implementation of the invention. Those skilled in the art can easily understand other advantages and effects of the invention from the content disclosed in this specification.

[0055] Exemplary embodiments of the invention are now described; however, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments is not intended to limit the invention.

[0056] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0057] Example 1

[0058] This embodiment provides a two-component nano-silica sol concrete repair material, comprising liquid component A and powder component B, with a mass ratio of 1:3.0. Liquid component A and powder component B are stored separately and mixed immediately before use.

[0059] The liquid component A is composed of the following raw materials in parts by weight: 25 parts water, 40 parts nano silica sol, 18 parts polymer emulsion, 0.3 parts retarder, and 0.2 parts defoamer.

[0060] The powder component B is composed of the following raw materials in parts by weight: 50 parts cement, 15 parts mineral admixtures, 30 parts quartz sand, 5 parts quick-setting agent, 1.0 part water-reducing agent, 0.08 parts cellulose ether, and 2 parts redispersible latex powder.

[0061] In this embodiment, the nano-silica sol was purchased from Zhejiang Yuda Chemical Co., Ltd., model LS25; the polymer emulsion was an acrylate emulsion; the retarder was sodium gluconate; the defoamer was an organosilicon defoamer, specifically dimethyl silicone oil; the cement was 42.5 silicate cement; the accelerator was an aluminate accelerator, specifically LXSNA-50 accelerator with a sodium aluminate content of 82%; the water-reducing agent was a polycarboxylate water-reducing agent, specifically WIN-105 polycarboxylate high-performance water-reducing agent with a water reduction rate of 33%; the cellulose ether was hydroxypropyl methylcellulose ether; and the redispersible latex powder was ethylene-vinyl acetate redispersible latex powder.

[0062] Preparation process:

[0063] Step 1) Preparation of Liquid Component A: 25 parts water, 40 parts nano-silica sol (SiO2 mass content 25%, average particle size 20nm, pH 10), 18 parts acrylate emulsion (solid content 45%), 0.3 parts sodium gluconate, and 0.2 parts silicone defoamer. Add water and nano-silica sol to a mixing container and stir at 300 rpm for 4 minutes until homogeneous. Add the acrylate emulsion, sodium gluconate, and silicone defoamer sequentially, stirring for 1.5 minutes after each addition. Finally, increase the speed to 1000 rpm and stir for 8 minutes. Seal and package.

[0064] Step 2) Preparation of Powder Component B: 50 parts of 42.5 silicate cement, 15 parts of mineral admixture (spherical fly ash microspheres: silica fume = 1:1), 30 parts of quartz sand (60 mesh), 5 parts of aluminate quick-setting agent, 1.0 part of polycarboxylate superplasticizer, 0.08 parts of hydroxypropyl methylcellulose ether (viscosity 120,000 mPa·s), and 2 parts of ethylene-vinyl acetate redispersible latex powder. Add all dry powder raw materials to a high-efficiency dry powder mixer and mix at 500 rpm for 10 minutes until the color is uniform. Then, seal and package in a moisture-proof container.

[0065] Example 2

[0066] This embodiment provides a two-component nano-silica sol concrete repair material, comprising liquid component A and powder component B, with a mass ratio of 1:2.8. Liquid component A and powder component B are stored separately and mixed immediately before use.

[0067] The liquid component A is composed of the following raw materials in parts by weight: 20 parts water, 35 parts nano silica sol, 20 parts polymer emulsion, 0.2 parts retarder, and 0.15 parts defoamer.

[0068] The powder component B is composed of the following raw materials in parts by weight: 45 parts cement, 12 parts mineral admixtures, 32 parts quartz sand, 6 parts quick-setting agent, 0.8 parts water-reducing agent, 0.06 parts cellulose ether, and 1.5 parts redispersible latex powder.

[0069] In this embodiment, the nano-silica sol was purchased from Zhejiang Yuda Chemical Co., Ltd., model LS20; the polymer emulsion was styrene-acrylic emulsion, the retarder was citric acid, the defoamer was a polyether-based defoamer, model PPE-600; the cement was 52.5 silicate cement, the accelerator was an alkali-free accelerator powder, specifically SBT®-N(Ⅲ) powder accelerator with an alkali content of 0.2%; the water-reducing agent was a polycarboxylate-based water-reducing agent, specifically WIN-105 type polycarboxylate high-performance water-reducing agent with a water reduction rate of 33%; the cellulose ether was hydroxypropyl methylcellulose ether, and the redispersible latex powder was vinyl acetate-vinyl tert-carbonate redispersible latex powder.

[0070] Preparation process:

[0071] Step 1) Preparation of Liquid Component A: 20 parts water, 35 parts nano-silica sol (SiO2 mass content 20%, average particle size 15nm, pH value 9), 20 parts styrene-acrylic emulsion (solid content 40%), 0.2 parts citric acid, and 0.15 parts polyether defoamer. Add water and nano-silica sol to a mixing container, mix the water and nano-silica sol, and stir at 250 rpm for 3.5 minutes; then add styrene-acrylic emulsion, citric acid, and polyether defoamer sequentially, stirring for 1 minute for each ingredient; increase the speed to 900 rpm and stir for 7 minutes, then seal and package.

[0072] Step 2) Preparation of Powder Component B: 45 parts of 52.5 silicate cement, 12 parts of mineral admixture (spherical fly ash microspheres: silica fume = 0.8:1), 32 parts of quartz sand (40 mesh), 6 parts of alkali-free liquid quick-setting agent powder, 0.8 parts of polycarboxylate superplasticizer, 0.06 parts of hydroxypropyl methylcellulose ether (viscosity 100,000 mPa·s), and 1.5 parts of vinyl acetate-vinyl tert-carbonate redispersible latex powder. Add all dry powder raw materials to a high-efficiency dry powder mixer and mix at 450 rpm for 11 minutes until the color is uniform. Then, seal and package in a moisture-proof container.

[0073] Example 3

[0074] This embodiment provides a two-component nano-silica sol concrete repair material, comprising liquid component A and powder component B, with a mass ratio of 1:3.5. Liquid component A and powder component B are stored separately and mixed immediately before use.

[0075] The liquid component A is composed of the following raw materials in parts by weight: 35 parts water, 50 parts nano silica sol, 25 parts polymer emulsion, 0.5 parts retarder, and 0.3 parts defoamer.

[0076] The powder component B is composed of the following raw materials in parts by weight: 60 parts cement, 20 parts mineral admixtures, 20 parts quartz sand, 8 parts quick-setting agent, 1.5 parts water-reducing agent, 0.1 parts cellulose ether, and 3 parts redispersible latex powder.

[0077] In this embodiment, the nano-silica sol was purchased from Zhejiang Yuda Chemical Co., Ltd., model LS30; the polymer emulsion was an epoxy emulsion; the retarder was tartaric acid; the defoamer was a polyether-based defoamer, model PPE-600; the cement was 52.5 silicate cement; the accelerator was an alkali-free accelerator powder, specifically SBT®-N(Ⅲ) powder accelerator with an alkali content of 0.2%; the water-reducing agent was a polycarboxylate-based water-reducing agent, specifically WIN-105 type polycarboxylate high-performance water-reducing agent with a water reduction rate of 33%; the cellulose ether was hydroxypropyl methylcellulose ether; and the redispersible latex powder was ethylene-vinyl acetate redispersible latex powder.

[0078] Preparation process:

[0079] Step 1) Preparation of Liquid Component A: 35 parts water, 50 parts nano-silica sol (SiO2 mass content 30%, average particle size 30nm, pH value 11), 25 parts epoxy emulsion (solid content 50%), 0.5 parts tartaric acid, and 0.3 parts polyether defoamer. Add water and nano-silica sol to a mixing container, mix the water and nano-silica sol, and stir at 250 rpm for 3.5 minutes; then add epoxy emulsion, tartaric acid, and polyether defoamer sequentially, stirring for 1 minute for each ingredient; increase the speed to 900 rpm and stir for 7 minutes, then seal and package.

[0080] Step 2) Preparation of Powder Component B: 45 parts of 60 silicate cement, 20 parts of mineral admixture (spherical fly ash microspheres: silica fume = 2:1), 20 parts of quartz sand (100 mesh), 8 parts of alkali-free liquid quick-setting agent powder, 1.5 parts of polycarboxylate superplasticizer, 0.1 parts of hydroxypropyl methylcellulose ether (viscosity 150,000 mPa·s), and 3 parts of ethylene-vinyl acetate redispersible latex powder. Add all dry powder raw materials to a high-efficiency dry powder mixer and mix at 450 rpm for 11 minutes until the color is uniform. Then, seal and package in a moisture-proof container.

[0081] Example 4

[0082] An application of a two-component nano-silica sol concrete repair material in UAV 3D printing repair is provided, including the following steps:

[0083] Step 1) Equipment preparation: Load the prepared liquid component A and powder component B into the dual storage tanks carried by the UAV respectively;

[0084] Step 2) Working condition scanning and information collection: The UAV flies to the area to be repaired and collects comprehensive working condition information of the area to be repaired using the onboard 3D laser scanning equipment or high-definition photogrammetry equipment;

[0085] The drone is equipped with an intelligent working condition identification and parameter adaptation system, which integrates a data acquisition module, a data analysis and processing module, a proportioning and process parameter decision module, and an execution control module.

[0086] Step 3) Working Condition Analysis and Parameter Decision: The data analysis and processing module performs 3D modeling, defect identification and quantitative analysis on the collected working condition information, and generates a detailed working condition assessment report. Then, the proportioning and process parameter decision module automatically determines the optimal composition ratio and process parameters of the repair material that are suitable for the current working condition based on the working condition assessment report, and transmits the decision instructions to the execution control module.

[0087] Step 4) Substrate treatment: The execution control module, according to the decision instructions, controls the drone or supporting equipment to clean the concrete lining substrate to be repaired;

[0088] Step 5) Material mixing and extrusion: According to the decision-made proportioning instructions, the execution control module controls the two-component precision metering pump to synchronously and accurately pump the liquid and powder materials into the mixing chamber according to the set ratio. The materials are then mixed at high speed and instantaneously in the chamber, and then extruded from the nozzle with a diameter of 3~5mm. The extrusion rate is precisely controlled according to the decision-made process parameters.

[0089] Step 6) Layered printing repair: Based on the process parameters determined by the proportioning and process parameter decision module in Step 3), layered printing repair is carried out until the entire repair body is constructed;

[0090] Step 7) Maintenance: After the construction is completed, spray the repaired area with water to keep it moist for at least 3 days, or cover it with a water-retaining film, and then allow it to grow naturally until the required age.

[0091] The repair material prepared in Example 1 was used to simulate two typical working conditions of 3D printing repair of drones, demonstrating the intelligent dispensing process:

[0092] Condition A (Wide and Deep Cracks): The scan identified cracks with an average width > 5mm and a depth > 30mm. The intelligent control module, based on model calculations, outputs adjustment instructions: slightly increase the liquid content to improve fluidity and ensure deep filling; fine-tune the A:B mixing ratio to 1:2.7; temporarily add 0.5 parts of 3mm long polypropylene fiber powder to the B component hopper to enhance crack resistance; and simultaneously reduce the printing speed to ensure sufficient material deposition.

[0093] Condition B (Curved Arch Detachment): Scanning identifies detachment in the arch area, with a large curvature of the curved surface. The intelligent control module outputs the following instructions: slightly increase the powder ratio to improve the slurry's cohesiveness and thixotropy; fine-tune the A:B mixing ratio to 1:3.2; simultaneously increase the hydroxypropyl methylcellulose ether content to 0.1 parts to enhance anti-sagging ability; and plan a denser short-path printing strategy to adapt to the curved surface morphology.

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 1 is that the nano-silica sol in component A is replaced with an equal amount of water.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 1 is that the amount of nano-silica sol in component A is set to 10 parts and the amount of water to 55 parts.

[0098] Comparative Example 3

[0099] Comparative Example 3 differs from Example 1 in that the nano-silica sol in component A is replaced with an equal amount of ordinary silica sol, wherein the average particle size of SiO2 particles is 80 μm. The preparation process of ordinary silica sol is as follows: First, prepare industrial-grade water glass (modulus 3.1-3.3, solid content 28%), 37% hydrochloric acid, and deionized water. Dilute the water glass with deionized water to a SiO2 mass concentration of 10% and stir evenly. Slowly add hydrochloric acid to adjust the pH of the system to 2-3. Stir at room temperature for 30 minutes to form a silica gel precursor. Then, age the silica gel at 50℃ for 24 hours to form a dense gel block. Crush the block into particles with a particle size of 100-200 μm using a mechanical crushing device. Wash the gel particles repeatedly with deionized water to remove chloride ions until the conductivity of the washing solution is ≤50 μS / cm. Then, add 0.5% polyethylene glycol by weight of the gel as a dispersant and stir at 500 rpm for 1 hour to obtain an ordinary silica sol suspension with an average particle size of 80 μm. Finally, adjust the SiO2 mass content in the suspension to 25% by vacuum concentration.

[0100] Comparative Example 4

[0101] The difference between Comparative Example 4 and Example 1 is that no polymer emulsion was added.

[0102] To further illustrate the effects of the present invention, performance tests were conducted on the repair materials prepared in Examples 1-3 and the concrete materials prepared in Comparative Examples 1-4. The test results are shown in Tables 1 and 2.

[0103] 1. Initial fluidity: Tested according to the current national standard GB / T 2419-2005 "Determination of fluidity of cement mortar";

[0104] 2. Setting time: Tested according to the current national standard GB / T 1346-2024, "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement".

[0105] 3. Compressive strength: Tested according to the current national standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" with specimen size of 40mm×40mm×160mm;

[0106] 4. Tensile bond strength with concrete substrate: Tested in accordance with the current national standard "Code for Acceptance of Construction Quality of Strengthening Engineering of Building Structures" GB 50550-2010.

[0107] 5. Extrudability and support: Tested according to the current China Engineering Construction Standardization Association standard "Technical Specification for Concrete 3D Printing" T / CECS 786-2020.

[0108] 6. For the intelligent dispensing verification example, additional tests were conducted on its fill density and surface printing shape retention rate under simulated working conditions.

[0109] Table 1

[0110]

[0111] Table 2

[0112]

[0113] As shown in Tables 1 and 2, the repair materials of Examples 1, 2, and 3 exhibit excellent performance in all aspects: initial flowability is 170 mm, 165 mm, and 162 mm, respectively, which is suitable for the extrusion requirements of the UAV printing system; the initial setting time is controlled within 8-10 minutes, avoiding sagging while ensuring the operating window; the compressive strength reaches 1.6-1.9 MPa at 1 hour, 26-30 MPa at 24 hours, and as high as 57-63 MPa at 28 days, with a reasonable strength development rhythm; the tensile bond strength with the concrete substrate is 2.1-2.5 MPa, indicating a strong bond; and it also possesses good extrudability and support, fully meeting the construction requirements of UAV 3D printing tunnel repair. Comparative analysis shows that the excellent performance of the materials in these examples stems from the reasonable ratio and synergistic effect of nano-silica sol with other components, fully leveraging the core functions of nano-silica sol in terms of coagulation control, strength enhancement, bond strengthening, thixotropic optimization, and volume stability.

[0114] In contrast, Comparative Example 1 (without nano-silica sol) exhibited a significantly prolonged initial setting time (35 min), extremely low early strength (compressive strength of only 0.3 MPa at 1 h), and insufficient later strength and bond strength (compressive strength of 42 MPa and bond strength of 0.8 MPa at 28 days). Furthermore, its morphology was difficult to maintain after extrusion, failing to meet the requirements of UAV 3D printing operations. Comparative Example 2 (insufficient nano-silica sol dosage) showed better initial flowability than Comparative Example 1, but its setting time and strength performance were significantly inferior to the example, with insufficient support. Comparative Example 3 (using ordinary silica sol with an average particle size of 80 μm) suffered from excessively large silica sol particle size, failing to leverage the synergistic effect at the nanoscale. It was significantly inferior to the example in terms of setting time, strength, and bond performance, and its support also failed to meet requirements. Comparative Example 4 (without polymer emulsion) lacked the synergistic effect of the organic phase, resulting in a significant decrease in bond strength (only 1.0 MPa). Its 28-day compressive strength and support were also significantly inferior to the example, with localized tearing, failing to guarantee the long-term collaborative work between the repair and the substrate.

[0115] The results of the intelligent mixing verification example show that, under the premise that the basic formula (Example 1) has excellent performance, by dynamically adjusting the mixing ratio or introducing trace amounts of functional additives according to specific working conditions (wide and deep cracks, arch surface detachment), the key performance of the material under the working conditions (such as filling density and anti-sagging properties) can be further optimized by using the intelligent control module. This achieves a high-precision match between material performance and repair requirements, and verifies the effectiveness and advancement of the intelligent application method of the present invention.

[0116] In summary, the present invention is applicable to UAV 3D printing repair materials and meets the following key requirements: (1) good extrudability and pumpability to adapt to the lightweight, small-diameter printing system of UAVs; (2) controllable setting time, requiring rapid initial setting after extrusion to prevent sagging, but also requiring sufficient operating window to complete mixing and positioning; (3) excellent thixotropy and stacking ability, with high viscosity when stationary to maintain shape, reduced viscosity during shearing for easy extrusion, and rapid recovery after extrusion to ensure stable stacking of printed lines on vertical or inclined surfaces without collapse; (4) good wet bonding performance with old concrete substrates to ensure that the repair body and the substrate work together; (5) early strength, high strength and volume stability, able to quickly build strength to support continuous printing or early load-bearing, with later strength matching the substrate, and low shrinkage and good crack resistance. More importantly, the material needs to be adjustable to adjust performance parameters according to different working conditions.

[0117] The examples above are merely illustrative of the invention and do not constitute a limitation on the scope of protection of the invention. Any design that is the same as or similar to the invention falls within the scope of protection of the invention.

Claims

1. A two-component nano-silica sol concrete repair material, characterized in that: It includes liquid component A and powder component B, with a mass ratio of 1:(2.5~3.5). Liquid component A and powder component B are stored separately and mixed immediately before use. The liquid component A is composed of the following raw materials in parts by weight: 20-35 parts water, 30-50 parts nano silica sol, 10-25 parts polymer emulsion, 0.1-0.5 parts retarder, and 0.1-0.3 parts defoamer. The powder component B is composed of the following raw materials in parts by weight: 40-60 parts cement, 10-20 parts mineral admixtures, 20-35 parts quartz sand, 3-8 parts quick-setting agent, 0.5-1.5 parts water-reducing agent, 0.05-0.1 parts cellulose ether, and 1-3 parts redispersible latex powder.

2. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The nano-silica sol has a SiO2 content of 20% to 30%, an average particle size of 10 to 30 nm, and a pH value of 9 to 11.

3. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The polymer emulsion is selected from at least one of acrylate emulsion, styrene-acrylic emulsion, and epoxy emulsion, and has a solid content of 40% to 50%.

4. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The retarder is selected from at least one of sodium gluconate, citric acid, and tartaric acid.

5. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The mineral admixture is composed of spherical fly ash microspheres and silica fume in a mass ratio of (0.5~2):

1. The particle size of the spherical fly ash microspheres is 1~10μm, and the particle size of the silica fume is 0.1~0.3μm.

6. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The cellulose ether is hydroxypropyl methylcellulose with a viscosity of 100,000 to 150,000 mPa·s.

7. The nano-silica sol two-component concrete repair material according to claim 1, characterized in that: The redispersible latex powder is an ethylene-vinyl acetate copolymer or a vinyl acetate-vinyl tert-carbonate copolymer latex powder.

8. A method for preparing a two-component nano-silica sol concrete repair material as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1) Preparation of liquid component A: Mix the prescribed amount of water and nano silica sol evenly, then add the prescribed amount of polymer emulsion, retarder, and defoamer while stirring. After stirring evenly, a uniform and stable suspension is formed. Immediately seal and package for later use. Step 2) Preparation of powder component B: Mix the cement, mineral admixtures, quartz sand, quick-setting agent, water-reducing agent, cellulose ether, and redispersible latex powder in the prescribed amounts evenly and then pack them in a moisture-proof and sealed package.

9. The application of a two-component nano-silica sol concrete repair material as described in any one of claims 1-7 in UAV 3D printing repair, characterized in that, Includes the following steps: Step 1) Equipment preparation: Load the prepared liquid component A and powder component B into the dual storage tank carried by the UAV respectively; Step 2) Working condition scanning and information collection: The UAV flies to the area to be repaired and collects comprehensive working condition information of the area to be repaired using the onboard 3D laser scanning equipment or high-definition photogrammetry equipment; The drone is equipped with an intelligent working condition identification and parameter adaptation system, which integrates a data acquisition module, a data analysis and processing module, a proportioning and process parameter decision module, and an execution control module. Step 3) Working Condition Analysis and Parameter Decision: The data analysis and processing module performs 3D modeling, defect identification and quantitative analysis on the collected working condition information, and generates a detailed working condition assessment report. Then, the proportioning and process parameter decision module automatically determines the optimal composition ratio and process parameters of the repair material that are suitable for the current working condition based on the working condition assessment report, and transmits the decision instructions to the execution control module. Step 4) Substrate treatment: The execution control module, according to the decision instructions, controls the drone or supporting equipment to clean the concrete lining substrate to be repaired; Step 5) Material mixing and extrusion: According to the decision-made proportioning instructions, the execution control module controls the two-component precision metering pump to synchronously and accurately pump the liquid and powder materials into the mixing chamber according to the set ratio. The materials are then mixed at high speed and instantaneously in the chamber, and then extruded from the nozzle with a diameter of 3~5mm. The extrusion rate is precisely controlled according to the decision-made process parameters. Step 6) Layered printing repair: Based on the process parameters determined by the proportioning and process parameter decision module in Step 3), layered printing repair is carried out until the entire repair body is constructed; Step 7) Maintenance: After the construction is completed, spray the repaired area with water to keep it moist for at least 3 days, or cover it with a water-retaining film, and then allow it to grow naturally until the required age.

10. The application of the nano-silica sol two-component concrete repair material according to claim 9 in UAV 3D printing repair, characterized in that: The optimal composition ratio of the repair material mentioned in step 3) includes the mixing mass ratio of liquid component A and powder component B, as well as the weight parts of each component of liquid component A and powder component B. The process parameters mentioned in step 3) include printing path, printing layer thickness, line width, printing speed, flight height, and extrusion rate.

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