Preparation method of crack repairing mortar

Abstract

The invention relates to the field of mortar preparation, and particularly discloses a crack repair mortar preparation method which comprises the following steps: S1, preparation of a nano-enhanced alkali-activated liquid phase: S1.1, putting a preset amount of a water-based dispersion medium into a mixing container, starting a high-shear dispersion device, uniformly adding nano titanium dioxide powder under the action of continuous shear force, and uniformly stirring to obtain a nano-enhanced alkali-activated liquid phase; carrying out mechanical dispersion treatment so as to obtain primarily deagglomerated nano slurry; by constructing a nano-enhanced alkali-activated liquid phase system and adopting a step-by-step sequential addition and specific dispersion stabilization process, the problem of agglomeration of nano-materials in a liquid phase is effectively solved, uniform distribution and stable existence of nano-components in the system are ensured, and the enhancement and toughening effects of the nano-materials on a geopolymer system are fully exerted.

Description

Technical Field

[0001] This invention relates to the field of mortar preparation, specifically a method for preparing crack repair mortar. Background Technology

[0002] In the field of construction engineering, the problem of cracks in concrete structures caused by loads, deformation and environmental erosion is becoming increasingly prominent, and the performance requirements for crack repair materials are constantly being raised.

[0003] Traditional cement-based repair mortars suffer from insufficient bond strength, poor toughness, and susceptibility to shrinkage cracks. Their durability often fails to meet long-term service requirements, especially under dynamic loads or significant deformation. Geopolymer cementitious materials, as a novel type of inorganic polymer, demonstrate application potential in the repair materials field due to their advantages such as rapid strength development, good chemical corrosion resistance, and low carbon emissions. However, conventional geopolymer materials still suffer from high brittleness, susceptibility to shrinkage cracking, and relatively limited performance control methods.

[0004] In recent years, the application of nanomaterials has provided new ideas for improving the performance of geopolymers. However, nanoparticles are prone to agglomeration in the system, making it difficult to fully exert their reinforcing and toughening effects. While existing technologies have attempted to disperse nanoparticles through mechanical stirring, the lack of effective control over dispersion stability and subsequent reaction processes leads to unsatisfactory nano-modification effects and significant performance fluctuations. Therefore, how to further optimize the preparation process of geopolymer systems while ensuring the uniform dispersion and stable existence of nanomaterials, and to prepare crack repair mortars with high strength, good toughness, and durability, remains a technical problem that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing crack repair mortar to overcome the above-mentioned defects in the prior art.

[0006] According to a method for preparing crack repair mortar, the method includes the following steps: S1. Preparation of nano-reinforced alkali-activated liquid phase, specifically including: S1.1. Add a predetermined amount of aqueous dispersion medium to the mixing container, start the high shear dispersion device, and uniformly add nano titanium dioxide powder under continuous shear force to carry out mechanical dispersion treatment to obtain a preliminary de-agglomerated nano slurry. S1.2 Add cellulose ether polymer stabilizer to the nano slurry of step S1.1 and continue mechanical dispersion treatment until the cellulose ether polymer stabilizer is completely hydrated and fully adsorbed on the surface of nanoparticles in the nano slurry to form a sterically stable nano colloidal dispersion system. S1.3 Under the condition of maintaining the stirring in step S1.2, add strong alkali solid and alkali metal silicate solution to the nanocolloid dispersion system obtained in step S1.2 in sequence, control the feeding rate and continue stirring until the strong alkali solid is completely dissolved and all components are fully mixed to form a nanocomposite alkali activator. S1.4 Add a high-molecular-weight polycarboxylic acid water-reducing agent and an organic retarder to the nano-composite alkali activator in step S1.3 and stir continuously to ensure uniform distribution throughout the liquid phase system, and finally obtain a nano-reinforced alkali-activated liquid phase. S2. Add the silicon-aluminum raw materials, aggregates with different particle size distributions, and fiber toughening materials into a dry powder mixing equipment for thorough mechanical mixing until a solid mixture with uniform component distribution is obtained. S3. The nano-reinforced alkali-activated liquid phase obtained in step S1 and the solid mixture obtained in step S2 are put into a mortar mixer and stirred continuously until a paste-like geopolymer mortar is formed. S4. Place the geopolymer mortar slurry that has been mixed and formed in step S3 in a constant temperature and humidity environment for static curing to promote the full progress of the geopolymer polymerization reaction and the stabilization of the slurry microstructure. S5. The geopolymer mortar that has been cured in step S4 and has reached the predetermined performance state is transported to the automatic packaging line for precise metering, dispensing and sealing to obtain mortar that can be directly used for repairing engineering cracks.

[0007] Preferably, in steps S1.1 and S1.2, the mechanical dispersion process is achieved by switching different stirring mechanisms in the same closed reaction vessel to avoid the nanomaterials coming into contact with air and agglomerating again during the transfer process.

[0008] Preferably, in step S1.2, the criterion for determining the sterically stable nanocolloid dispersion system is: The viscosity of the system was monitored by an online viscometer and the fluctuation range was less than 5% within 2 consecutive minutes.

[0009] Preferably, in step S1.3, the alkali metal silicate solution is an aqueous sodium silicate solution with a modulus in the range of 1.2 to 2.0; The controlled feeding rate refers to adding the strong alkali solid in batches, and waiting for the system temperature to rise to its peak before adding the next batch, in order to control the exothermic reaction process of alkali dissolution.

[0010] Preferably, in step S1.4, after adding the polymeric polycarboxylate superplasticizer and organic retarder, the continuous stirring time continues until the temperature difference between the nanocomposite alkali activator and the ambient temperature is within ±3℃.

[0011] Preferably, in step S3, the process of continuously stirring until a paste-like geopolymer mortar is formed is configured as follows: First, stir at a speed of 100-300 rpm to achieve initial wetting and impregnation of the solid material; The stirring speed is then increased to 800-1200 rpm to achieve intense shearing and homogenization of the slurry.

[0012] Preferably, in step S4, the static curing process is carried out in a curing room with programmable humidity and temperature control. The static curing process includes a main polymerization reaction stage that maintains high humidity, and a subsequent gradual drying stage that promotes strength growth.

[0013] The beneficial effects of this invention are: 1. By constructing a nano-reinforced alkali-activated liquid phase system and adopting a stepwise sequential addition and specific dispersion stabilization process, the agglomeration problem of nanomaterials in the liquid phase is effectively solved, ensuring the uniform distribution and stable existence of nano-components in the system, and giving full play to the reinforcing and toughening effect of nanomaterials on the geopolymer system.

[0014] 2. By optimizing the solid phase composition ratio and mixing process, and combining the liquid-solid two-phase staged mixing procedure, the uniformity and density of the slurry are effectively improved, the workability of the mortar is improved, and the final repair mortar maintains the high strength and high durability of the geopolymer material while also having good flexibility and bonding performance.

[0015] 3. The programmed static curing method effectively promotes the full progress of the geopolymer polymerization reaction and the stabilization of the microstructure, reduces the risk of shrinkage cracking, and enables the product to better adapt to the crack repair needs under dynamic loads and deformation conditions, thereby improving the long-term durability of the project. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a crack repair mortar preparation method provided by the present invention; Figure 2 This is a schematic diagram of the preparation process of nano-reinforced alkali-activated liquid phase in a crack repair mortar preparation method provided by the present invention. Detailed Implementation

[0017] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the appendix. Figure 1The orientations or positional relationships shown are merely for the purpose of simplifying the description of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0018] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is only used to describe one or more specific embodiments of this invention and does not strictly limit the scope of protection specifically claimed by this invention. As used herein, the terms up and down and left and right are not limited to their strict geometric definitions, but include tolerances for reasonable and inconsistent machining or human errors. The specific features of this crack repair mortar preparation method are described in detail below: An embodiment of the present invention: Reference Figure 1 This invention provides a method for preparing crack repair mortar, the method comprising the following steps: S1, Preparation of nano-reinforced alkali-activated liquid phase, such as Figure 2 As shown, it specifically includes: S1.1. Add a predetermined amount of aqueous dispersion medium to the mixing container, start the high shear dispersion device, and uniformly add nano titanium dioxide powder under continuous shear force to carry out mechanical dispersion treatment to obtain a preliminary de-agglomerated nano slurry. Specifically, in step S1.1, the mechanical dispersion process is achieved in a closed reaction vessel by switching between different stirring mechanisms to prevent the nanomaterials from coming into contact with air and agglomerating again during the transfer process.

[0019] In this embodiment, the high-shear dispersion device specifically includes: The reaction vessel is a jacketed, sealed reactor as the core. The reactor body is preferably made of 316L stainless steel to withstand highly alkaline environments. The upper part of the reactor lid has multiple flange interfaces for installing different stirring mechanisms, feeding ports, PT100 temperature sensors, pH sensors, and online viscometer sensors. The preferred online viscometer is the Brookfield TT-100 series, whose coaxial cylindrical rotor design provides precise shear rate, accurately monitoring viscosity changes of the nano-slurry under specific shear conditions. The system is equipped with two independent stirring mechanisms, both controlled by drive motors located on top of the vessel lid, and can be switched and adjusted individually via the control panel. The first stirring mechanism is a high-shear disperser. Specifically, it is a stator-rotor type high-shear disperser head, with the gap between the stator and rotor designed to be at the micrometer level, which can generate extremely strong mechanical shear force and high-frequency hydraulic shear when the rotor rotates at high speed. This mechanism is mainly used for the primary nano-dispersion in step S1.1, and its rotation speed is adjustable from 3000 to 8000 rpm. The second stirring mechanism is a frame-type or anchor-type stirrer. The outer shape of its stirring paddle is similar to the outline of the inner wall of the vessel, with a small gap. This mechanism is mainly used for uniform stirring in step S1.2 and thereafter. It can promote the material to generate a large-scale circulation flow at a low speed (100~400 rpm), ensuring the uniform distribution of additives such as stabilizers, while avoiding damage to the formed stable colloidal structure due to excessive shear force. The feeding system specifically includes a liquid feeding system and a powder feeding system: The liquid feeding system pumps the aqueous dispersion medium (water) from the storage tank into the reaction vessel through a metering pump and pipeline system. The powder feeding system operates on the principle of vacuum feeding. First, all valves are closed, and the reactor is drawn into a slightly negative pressure by a vacuum pump. Then, the negative pressure is used to draw nano-titanium dioxide powder stored in a specific powder silo into the sealed reactor. This process completely isolates the air, effectively preventing dust from flying and pre-agglomeration caused by the introduction of external moisture. Liquid additive feeding: Liquid materials such as alkali metal silicate solution are added through a dedicated closed metering tank and valve control.

[0020] The specific process of mechanical dispersion in step S1.1 is as follows: The first step is to add the prescribed amount of deionized water into the sealed reaction vessel using a metering pump; The second step is to start the high-shear disperser and set its speed to 5000 rpm; The third step involves activating the vacuum feeding system to uniformly and slowly draw the precisely metered nano-titanium dioxide powder into the reactor over 2-4 minutes. Slow feeding is crucial to prevent the powder from rushing in and forming large, difficult-to-disperse clumps. The fourth step is to maintain high shear dispersion after all the powders are added and continue to disperse for 8-12 minutes. During this process, the strong shear force will effectively break up the agglomerates of nanoparticles to obtain "preliminary deagglomerated nano slurry". The state of the slurry can be observed through the sight glass on the lid of the vessel throughout the process, and there should be no obvious agglomerates floating.

[0021] S1.2 Add cellulose ether polymer stabilizer to the nano slurry of step S1.1 and continue mechanical dispersion treatment until the cellulose ether polymer stabilizer is completely hydrated and fully adsorbed on the surface of nanoparticles in the nano slurry to form a sterically stable nano colloidal dispersion system. Specifically, in step S1.2, the mechanical dispersion treatment is achieved in the same closed reaction vessel as in step S1.1 by switching different stirring mechanisms. The criterion for determining a sterically stable nanocolloid dispersion system is as follows: The viscosity of the system was monitored by an online viscometer and the fluctuation range was less than 5% within 2 consecutive minutes. Example

[0022] The specific process of mechanical dispersion treatment in step S1.2 is as follows: First, after step S1.1 is completed, reduce the speed of the high-shear disperser to zero and stop it from running; The second step is to start the frame mixer and set the speed to 200 rpm. The third step involves adding cellulose ether polymer stabilizers (such as hydroxypropyl methylcellulose) to the continuously stirred nano-slurry through a solid feeding port (which is immediately sealed after feeding) or a liquid additive feeding system. The fourth step is to maintain the stirring of the frame stirrer for 15 to 25 minutes. During this period, the polymer stabilizer is fully dissolved and hydrated, and its long-chain molecules are physically adsorbed and wrapped on the surface of the nanoparticles to form a stable steric hindrance layer. The fifth step is to monitor the viscosity changes of the system using an online viscometer connected to the reactor. When the viscosity reading fluctuates by less than 5% within 2 consecutive minutes, it can be determined that the system has reached a stable state and formed a "sterically stable nanocolloid dispersion system".

[0023] In this embodiment, since the surface charge characteristics of nano-titanium dioxide powder may change in a strongly alkaline environment, there is a risk of re-agglomeration. To address this issue, this step uses a cellulose ether polymer stabilizer (preferably hydroxypropyl methylcellulose). The ether bonds and hydroxyl groups on its molecular chain can still be firmly adsorbed onto the surface of nano-titanium dioxide particles under strongly alkaline conditions through hydrogen bonds, van der Waals forces, and other interactions. These adsorbed polymer chains fully extend in the alkaline aqueous medium, forming a stable three-dimensional hydration layer. Through a strong steric hindrance effect, the van der Waals attraction between particles and the potential problem of insufficient electrostatic repulsion are effectively overcome, thereby ensuring the long-term stability of the nano-colloidal dispersion system in the subsequent alkaline activation step and throughout the entire storage period.

[0024] It should be noted that although high alkalinity and ionic strength generally pose challenges to the stability of cellulose ethers, this risk is effectively mitigated under the specific formulation and process sequence described in this invention. Preferably, the cellulose ether polymeric stabilizer is alkali-resistant hydroxypropyl methylcellulose (HPMC). This type of HPMC, after a specific etherification process, exhibits significantly better solubility and stability in strongly alkaline environments than ordinary types. Furthermore, the process sequence of this invention—first forming a sterically stabilizing system and then introducing an alkali activator—allows the polymer chains to be fully adsorbed and fixed on the surface of the nanoparticles before the pH value gradually increases, forming a more robust protective layer. This layer is sufficient to resist the 'salting-out' effect caused by Na⁺ ions in the subsequent sodium silicate aqueous solution, ensuring the stability of the system throughout the entire preparation and storage process.

[0025] S1.3 Under the condition of maintaining the stirring in step S1.2, add strong alkali solid and alkali metal silicate solution to the nanocolloid dispersion system obtained in step S1.2 in sequence, control the feeding rate and continue stirring until the strong alkali solid is completely dissolved and all components are fully mixed to form a nanocomposite alkali activator. Specifically, in step S1.3, the alkali metal silicate solution is an aqueous sodium silicate solution with a modulus in the range of 1.2 to 2.0; Controlling the feeding rate means adding strong alkali solids in batches, and waiting for the system temperature to rise to its peak before adding the next batch, in order to control the exothermic reaction process of alkali dissolution.

[0026] In this embodiment, the strong alkali solid is industrial-grade flake sodium hydroxide (NaOH), which is pre-crushed into small pieces of 1-3 cm³ to increase the specific surface area and accelerate dissolution; The alkali metal silicate solution is an aqueous solution of sodium silicate (water glass) with a modulus of 1.5 (the modulus falls within the preferred range of 1.2 to 2.0). This solution needs to be prepared in advance and kept at a constant temperature in a storage tank for later use. Step S1.3 is carried out in the same closed reactor used in step S1.2, maintaining the frame / anchor stirrer at a speed of 150-250 rpm to ensure that the reaction heat energy is distributed in a timely and uniform manner, while avoiding the introduction of excessive shear force; The specific steps are as follows: Batch addition and heat management of strong alkali solids: The first step is to add small pieces of sodium hydroxide, about one-third of the total alkali volume, through the solid feed port of the reactor; The second step is to immediately close the feed inlet and closely monitor the reading of the PT100 temperature sensor connected to the reactor. Sodium hydroxide dissolution is a strongly exothermic process, and the system temperature will rise rapidly. Wait until the temperature reading reaches a peak and begins to decline (usually, the temperature will drop 1-3°C from its peak before the next addition), indicating that the main exothermic reaction caused by this alkali addition has essentially ended. The third step is to repeat the above process, adding about one-third more and then the remaining amount. Each addition must be done after the temperature peak caused by the previous addition has passed. The entire alkali addition process may last 10-20 minutes.

[0027] Introducing an alkali metal silicate solution: The first step is to pump a predetermined amount of sodium silicate aqueous solution with a modulus of 1.5 into the reactor in a uniform and slow manner over 3-5 minutes after the last addition of sodium hydroxide and the peak temperature. The second step is to continue stirring until the system can be observed to change from a milky white nanocolloid solution to a translucent, slightly opalescent gel-like liquid. This indicates that the alkali activator has initially interacted with the surface of the nanoparticles, and the "nanocomposite alkali activator" has been formed.

[0028] S1.4 Add a high-molecular-weight polycarboxylic acid water-reducing agent and an organic retarder to the nano-composite alkali activator in step S1.3 and stir continuously to ensure uniform distribution throughout the liquid phase system, and finally obtain a nano-reinforced alkali-activated liquid phase. Specifically, in step S1.4, after adding the high-molecular-weight polycarboxylate superplasticizer and organic retarder, the stirring is continued until the temperature difference between the nanocomposite alkali activator and the ambient temperature is within ±3℃.

[0029] In this embodiment, step S1.4 is carried out continuously in the same closed reaction vessel as step S1.3, maintaining the frame stirrer at a speed of 180-220 rpm.

[0030] First, 1.0-1.5% of the total solid mass of a polycarboxylate superplasticizer is slowly added through a liquid feeding system. This superplasticizer is a commercially available liquid product with a concentration of 40% and a water reduction rate of not less than 25%. After the water-reducing agent is added, continue to add 1.5-2.0% of sodium gluconate as an organic retarder. Sodium gluconate is a white crystalline powder with a purity of ≥98%. The total addition time of the two additives should be controlled within 3-5 minutes, and the stirring should be kept continuous and stable during the addition process. After the addition is complete, continue stirring and start timing. Cool the system through the circulating cooling water system of the reactor jacket. The cooling water temperature is set to 20±2℃. During this process, a calibrated PT100 temperature sensor was used to continuously monitor the system temperature, while an ambient temperature monitoring point was set up 2 meters away from the reactor in the same workshop. The process endpoint was determined to have been reached when the difference between the system temperature and the ambient temperature stabilized within ±3℃ and remained stable for at least 2 minutes. The entire stirring and cooling process usually takes 20-40 minutes. The resulting nano-enhanced alkali activation solution is homogeneous, without stratification or precipitation, and its pH value should be maintained within the range of 13.2-13.8. This specific implementation method ensures that all components are fully dispersed and reach thermal equilibrium, guaranteeing the stability of process performance during subsequent mixing with the solid phase.

[0031] S2. Add the silicon-aluminum raw materials, aggregates with different particle size distributions, and fiber toughening materials into a dry powder mixing equipment for thorough mechanical mixing until a solid mixture with uniform component distribution is obtained. In this embodiment, step S2 uses a dual-motion mixer to mix solid materials. This equipment has the functions of rotating the cylinder and independent movement of the internal stirring paddle.

[0032] First, accurately weigh each component according to the formula: the silicon-aluminum raw material is metakaolin with an activity index of not less than 105%, accounting for 35-40% of the total solid phase mass; The aggregate system consists of 40-70 mesh quartz sand, 70-140 mesh quartz sand and 140-200 mesh quartz sand in a mass ratio of 4:3:3, with the total aggregate accounting for 54-58% of the total solid mass. The fiber-reinforcing material is made of polyvinyl alcohol fibers with a length of 6-12 mm and a diameter of 20-40 μm, and the addition amount is 0.5-1.0% of the total solid phase mass. The feeding sequence is as follows: first, put the three types of quartz sand into the mixer and mix them at a cylinder speed of 15-20 rpm for 3-5 minutes. Then, add metakaolin and continue mixing for 5-8 minutes. Finally, while the equipment is running, slowly add PVA fiber through a special feed port to avoid fiber clumping. Throughout the mixing process, maintain the cylinder speed at 15-20 rpm and the internal stirring paddle speed at 80-120 rpm, with the total mixing time controlled at 20-30 minutes. The criterion for judging the uniformity of mixing is: take samples from different locations in the mixer three times, measure their titanium dioxide content, and the coefficient of variation is not greater than 5%; Meanwhile, the fiber distribution is observed by image analysis. The fiber quantity difference per unit area should not exceed 10%. The final solid mixture should be uniform in color, free of lumps, and have uniformly dispersed fibers. The particle size distribution of each component should meet the design requirements through standard sieve analysis. The specific implementation steps of the above image analysis method are as follows: The first step is to randomly select 5 samples from different locations in the mixed material, take 3±0.5g of each sample, and place them in a standard sample tray to spread them evenly into a single layer of particles. The second step involves using a Keyence VHX-6000 digital microscope or an equivalent device for image acquisition. It is equipped with a 20-megapixel CMOS sensor and a 20-200x continuous zoom lens. During image acquisition, the illumination conditions are set to coaxial incident illumination, the light source intensity is set to 75%, and the exposure time is automatically optimized to ensure that the contrast between the fiber and the background reaches a recognizable threshold. In this process, 10 fields of view were randomly selected for each sample for shooting, with a field size of 2mm×2mm and a resolution of 5μm / pixel; The third step involves image processing using Image-Pro Plus 10.0 software or equivalent image analysis software. The processing flow includes: First, Gaussian filtering is used for noise reduction. Then, Otsu's adaptive thresholding method is used for binarization. Finally, morphological opening operation is used to eliminate fine noise. When identifying fibers in the binary image, the identification parameters are set as follows: aspect ratio ≥ 5, equivalent diameter in the range of 20-40μm, and length in the range of 6-12mm. Secondly, the fibers identified in each field of view are counted and their area percentage is calculated. The uniformity criteria are: the coefficient of variation of the number of fibers in 10 fields of view is not greater than 10%, and the range of fiber area percentage is not greater than 0.5%. Finally, the fiber orientation analysis function is used to calculate the orientation distribution of fibers in the mixture, requiring that the difference in the number of fibers in each direction does not exceed 15%. All analytical data are automatically recorded and a distribution uniformity report is generated, serving as an important basis for the compliance of the mixing process.

[0033] S3. The nano-reinforced alkali-activated liquid phase obtained in step S1 and the solid mixture obtained in step S2 are put into a mortar mixer and stirred continuously until a paste-like geopolymer mortar is formed. Specifically, in step S3, the mixture is continuously stirred until a paste-like geopolymer mortar is formed. This process is configured as follows: First, stir at a speed of 100-300 rpm to achieve initial wetting and impregnation of the solid material; The stirring speed is then increased to 800-1200 rpm to achieve intense shearing and homogenization of the slurry.

[0034] In this embodiment, Step S3 employs a UJZ-15 type forced single-shaft mortar mixer to implement the liquid-solid two-phase mixing process. This equipment is equipped with a continuously variable speed motor and a power monitoring system, and specifically includes the following steps: First, put all the solid mixture obtained in step S2 into a mixing pot; The second step involves slowly adding the nano-composite alkali activator prepared in step S1 at a uniform rate, with the liquid-to-solid mass ratio controlled within the range of 0.14-0.16 and the total feeding time controlled within 60±10 seconds. The third step involves precise control of the mixing process in two stages: The first stage involves low-speed stirring at 150±50 rpm for 90±15 seconds. During this stage, the propulsion of the impeller ensures thorough wetting of the solid material and uniform impregnation of the liquid phase. Simultaneously, the power monitoring system should display that the motor load remains stable within 40%-60% of the rated power. The second stage immediately increases the speed to 1000±200 rpm for high-speed stirring for 180±30 seconds. This stage utilizes the strong shearing action between the impeller and the liner to achieve thorough homogenization of the slurry. During this period, the motor load should be maintained at 70%-85% of the rated power. The fourth step involves monitoring the viscosity change of the system during the mixing process using an online viscometer installed on the side wall of the mixing pot. The process endpoint is reached when the viscosity reaches 18000±2000 mPa·s. At this point, the slurry should have a uniform paste-like form with a glossy and dense surface. When checked with a scraper, there should be no dry material accumulation and the slurry should have good cohesiveness. The resulting geopolymer mortar should complete the subsequent processes within 30 minutes. The ambient temperature during the entire process should be controlled at 20±5℃ and the relative humidity should not be lower than 50%.

[0035] S4. Place the geopolymer mortar slurry that has been mixed and formed in step S3 in a constant temperature and humidity environment for static curing to promote the full progress of the geopolymer polymerization reaction and the stabilization of the slurry microstructure. Specifically, in step S4, the static curing process is carried out in a curing room with programmable humidity and temperature control. The static curing process includes a main polymerization reaction stage that maintains high humidity, and a subsequent gradual drying stage that promotes strength growth.

[0036] In this embodiment, step S4 uses an HBY-40B type cement concrete constant temperature and humidity curing chamber to implement the static curing process. This equipment is equipped with a microcomputer program control system, an ultrasonic humidifier, and a dual-path temperature control system of compressor refrigeration / electric heating tube heating. The specific steps include: The first step is to inject the geopolymer mortar slurry obtained in step S3 into a triple mold of 40mm×40mm×160mm and carry out programmed curing in the curing box. The second step, the main polymerization reaction stage, is set to be continuously cured for 72±2 hours under the conditions of temperature 20±1℃ and relative humidity ≥95%. During this stage, a saturated humidity environment is maintained by an ultrasonic humidifier to promote the full formation of the three-dimensional network structure of the geopolymer and the further bonding of nanoparticles. The third step is the gradual drying stage, which uses a segmented dehumidification program: first, the humidity is reduced to 80±5% at a uniform rate within 24 hours, and then it continues to be reduced to 60±5% within the next 48 hours. The temperature is always maintained at 20±1℃. Throughout the curing process, the equipment automatically records the temperature and humidity data and ensures that the fluctuation range meets the set requirements. The fourth step is to measure the strength of the specimen using a TSY-300 compression testing machine after curing. The 3-day compressive strength should not be less than 35 MPa, and the formation of a dense and uniform microstructure inside the slurry can be confirmed by scanning electron microscopy. S5. The geopolymer mortar that has been cured in step S4 and has reached the predetermined performance state is transported to the automatic packaging line for precise metering, dispensing and sealing to obtain mortar that can be directly used for repairing engineering cracks.

[0037] In this embodiment, the DCS-50 fully automatic dry mortar packaging machine is used to complete the finished product packaging. This system consists of a storage silo, a screw metering feeder, a heat-sealing packaging machine, and a conveyor belt. Specific steps include: The first step is to transport the geopolymer mortar slurry that has reached the predetermined performance state (its performance standards are 3-day compressive strength ≥35MPa, initial setting time ≥60 minutes, and final setting time ≤90 minutes) to the storage silo, and maintain a dry environment with a temperature of 20±5℃ and a relative humidity of ≤40% inside the silo. The second step involves metering and packaging the bags at a rate of 25±5 kg / bag using a precision screw feeder. The metering accuracy error is controlled within ±0.5%. Aluminum foil-coated composite packaging bags are used to ensure moisture-proof and light-proof performance. An automatic weighing feedback system is used during the packaging process to monitor the net weight of each bag in real time and automatically adjust the feeding speed. When the metering deviation exceeds the allowable range three times in a row, the system will automatically stop and adjust. The third step, the heat sealing process, sets the sealing temperature at 180±10℃, the sealing pressure at 0.4±0.1MPa, and the pressure holding time at 2±0.5 seconds to ensure a sealing strength of not less than 4.5N / 15mm. Each bag of finished product is affixed with a unique identification code, recording information such as production batch, curing time, and performance indicators. After packaging, the finished products are stacked vertically in a warehouse with a temperature ≤30℃ and relative humidity ≤50%, with a stacking height not exceeding 6 layers, and a shelf life of not less than 6 months.

[0038] Those skilled in the art will appreciate that various modifications to the above embodiments can be made without departing from the overall spirit and concept of the present invention. All such modifications fall within the protection scope of the present invention. The protection scheme of the present invention is defined by the appended claims.

Claims

1. A method for preparing crack repair mortar, characterized in that: The method includes the following steps: S1. Preparation of nano-reinforced alkali-activated liquid phase, specifically including: S1.

1. Add a predetermined amount of aqueous dispersion medium to the mixing container, start the high shear dispersion device, and uniformly add nano titanium dioxide powder under continuous shear force to carry out mechanical dispersion treatment to obtain a preliminary de-agglomerated nano slurry. S1.2 Add cellulose ether polymer stabilizer to the nano slurry of step S1.1 and continue mechanical dispersion treatment until the cellulose ether polymer stabilizer is completely hydrated and fully adsorbed on the surface of nanoparticles in the nano slurry to form a sterically stable nano colloidal dispersion system. S1.3 Under the condition of maintaining the stirring in step S1.2, add strong alkali solid and alkali metal silicate solution to the nanocolloid dispersion system obtained in step S1.2 in sequence, control the feeding rate and continue stirring until the strong alkali solid is completely dissolved and all components are fully mixed to form a nanocomposite alkali activator. S1.4 Add a high-molecular-weight polycarboxylic acid water-reducing agent and an organic retarder to the nano-composite alkali activator in step S1.3 and stir continuously to ensure uniform distribution throughout the liquid phase system, and finally obtain a nano-reinforced alkali-activated liquid phase. S2. Add the silicon-aluminum raw materials, aggregates with different particle size distributions, and fiber toughening materials into a dry powder mixing equipment for thorough mechanical mixing until a solid mixture with uniform component distribution is obtained. S3. The nano-reinforced alkali-activated liquid phase obtained in step S1 and the solid mixture obtained in step S2 are put into a mortar mixer and stirred continuously until a paste-like geopolymer mortar is formed. S4. Place the geopolymer mortar slurry that has been mixed and formed in step S3 in a constant temperature and humidity environment for static curing to promote the full progress of the geopolymer polymerization reaction and the stabilization of the slurry microstructure. The static curing process is carried out in a curing room with programmable humidity and temperature control. The static curing process includes a main polymerization reaction stage that maintains high humidity, and a subsequent gradual drying stage that promotes strength growth. S5. The geopolymer mortar that has been cured in step S4 and has reached the predetermined performance state is transported to the automatic packaging line for precise metering, dispensing and sealing to obtain mortar that can be directly used for repairing engineering cracks.

2. The method for preparing crack repair mortar according to claim 1, characterized in that: In steps S1.1 and S1.2, the mechanical dispersion process is achieved by switching different stirring mechanisms in the same closed reaction vessel to prevent the nanomaterials from coming into contact with air and agglomerating again during the transfer process.

3. The method for preparing crack repair mortar according to claim 1, characterized in that: In step S1.2, the criterion for determining the sterically stable nanocolloid dispersion system is: The viscosity of the system was monitored by an online viscometer and the fluctuation range was less than 5% within 2 consecutive minutes.

4. The method for preparing crack repair mortar according to claim 1, characterized in that: In step S1.3, the alkali metal silicate solution is an aqueous sodium silicate solution with a modulus in the range of 1.2 to 2.0; The controlled feeding rate refers to adding the strong alkali solid in batches, and waiting for the system temperature to rise to its peak before adding the next batch, in order to control the exothermic reaction process of alkali dissolution.

5. The method for preparing crack repair mortar according to claim 4, characterized in that: In step S1.4, after adding the polymeric polycarboxylate superplasticizer and organic retarder, the stirring is continued until the temperature difference between the nanocomposite alkali activator and the ambient temperature is within ±3℃.

6. The method for preparing crack repair mortar according to claim 1, characterized in that: In step S3, the process of continuously stirring until a paste-like geopolymer mortar is formed is configured as follows: First, stir at a speed of 100-300 rpm to achieve initial wetting and impregnation of the solid material; The stirring speed is then increased to 800-1200 rpm to achieve intense shearing and homogenization of the slurry.

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