Cement-based composite grouting material, preparation method thereof and grouting method

Abstract

This invention discloses a cement-based composite grouting material and its preparation and grouting methods, belonging to the field of building materials technology. The invention uses silicate cement, metakaolin, and silica fume as the cementitious component, and coupled elastic expandable microspheres as the core functional component, combined with aggregates and admixtures to obtain the cement-based composite grouting material. After grouting with the cement-based composite grouting material prepared by this invention, the coupled elastic expandable microspheres and the cement matrix form a strong and tough interfacial transition zone under specific curing conditions, avoiding defects caused by weak interfaces. Under stress, the material can efficiently dissipate energy through the plastic deformation of the coupled elastic expandable microspheres while maintaining high load-bearing capacity, achieving a balance between ultra-high toughness and high strength. This characteristic significantly improves the crack resistance and service life of the grout under dynamic loads and deformation, and enhances long-term volume stability.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a cement-based composite grouting material and its preparation and grouting methods. Background Technology

[0002] Cement-based grouting materials play an irreplaceable role in foundation reinforcement, tunnel engineering, and crack repair due to their wide availability of raw materials, low cost, and good compatibility with concrete structures. However, traditional cement-based grouting materials generally suffer from inherent technical bottlenecks: high brittleness and insufficient toughness, making them prone to secondary cracking under dynamic loads or deformation, resulting in poor repair durability; significant chemical shrinkage and drying shrinkage effects during hydration lead to shrinkage microcracks at the interface between the grout and the matrix, affecting the integrity and seepage prevention effect; and increasing the water-cement ratio is often necessary to achieve high fluidity, which in turn leads to decreased strength and water segregation.

[0003] To overcome the aforementioned shortcomings, existing technologies mainly focus on two aspects: incorporating polymer emulsions or fibers (such as PP fibers and steel fibers) to enhance toughness. However, polymer emulsions introduce excessive air bubbles and delay setting, while steel fibers are prone to corrosion and unsuitable for grouting fine cracks. Adding expansion agents (such as CSA-type agents) to compensate for shrinkage is another approach. However, a single expansion source often only functions at a specific point in time and cannot match the full-process shrinkage of cement-based materials from early to late stages. Furthermore, controlling the coordination between expansion and strength development is difficult. Especially for major projects with stringent durability requirements (such as underground engineering and water conservancy facilities), existing cement-based grouting materials remain insufficient in terms of long-term volume stability, crack resistance, and ability to coordinate deformation with old concrete. Summary of the Invention

[0004] This invention provides a cement-based composite grouting material and its preparation and grouting methods, which effectively solves the technical problems of poor long-term volume stability and crack resistance of existing cement-based grouting materials and insufficient synergistic deformation capacity with old concrete. At the same time, it constructs a high-performance cement-based composite grouting material that achieves full-process expansion compensation, diversified toughening mechanisms, and dense microstructure, which greatly improves the reliability and long-term effectiveness of engineering repair.

[0005] The first objective of this invention is to provide a cement-based composite grouting material made from the following raw materials in parts by weight: 650 to 700 parts silicate cement, 100 to 130 parts metakaolin, 80 to 90 parts silica fume, 20 to 35 parts coupled elastic expansion microspheres, 850 to 950 parts aggregate, and 8.9 to 13.5 parts admixture.

[0006] The coupled elastic expansion microspheres are formed by cross-linking a modified elastomer made of hydroxyl-terminated polybutadiene and polyurethane prepolymer as the core layer and a composite expansion source made of sulfoaluminate cement clinker and calcium oxide as the shell layer. The modified elastomer is wrapped with the composite expansion source and cross-linked and cured to form primary microspheres. After aging, an interpenetrating polymer network structure is formed inside the primary microspheres to obtain core-shell structured coupled elastic expansion microspheres.

[0007] The mass ratio of the core to the shell is 1:2 / 3 to 1.5.

[0008] As a preferred embodiment, the preparation method of the coupled elastic expandable microspheres includes the following steps: Using hydroxyl-terminated polybutadiene and polyurethane prepolymer as raw materials, plasticizers are added and mixed at 60℃~70℃. A modified elastomer is obtained under the action of a crosslinking agent. Using sulfoaluminate cement clinker and calcium oxide as raw materials, a hydration activator is added and mixed, then ball-milled until a specific surface area ≥400 m² is obtained. 2 / kg, to obtain the composite expansion source.

[0009] The modified elastomer is atomized into droplets, which are then encapsulated by a composite expansion source and cross-linked and cured to obtain primary microspheres. After aging, an interpenetrating polymer network structure is formed inside the primary microspheres, resulting in coupled elastic expansion microspheres with a particle size of 50 μm to 150 μm.

[0010] In the preparation of coupled elastic expandable microspheres, a fluidized bed granulation and coating machine was used to construct the core-shell structure. Modified elastomers were sprayed into the fluidized bed of the composite expansion source through a pressure atomizing nozzle. The atomized modified elastomers acted as "seeds," colliding, adhering to, and encapsulating the rapidly moving composite expansion source particles. By precisely controlling the fluidizing airflow (20 m³ / h–40 m³ / h), atomization pressure (0.2 MPa–0.4 MPa), and bed temperature (70℃–80℃), the surface of the modified elastomers was gradually coated with a uniform shell powder of the composite expansion source, and preliminary cross-linking and solidification occurred, forming stable core-shell structured microspheres. Curing and sieving: The obtained microspheres were transferred to a curing chamber and aged at 48℃–52℃ for 24 hours to ensure complete cross-linking of the core layer, forming a stable interpenetrating polymer network (IPN) structure. Finally, coupled elastic expansion microspheres with a particle size of 50μm to 150μm were screened out by a vibrating sieve and sealed for later use.

[0011] In a preferred embodiment, the mass ratio of the sulfoaluminate cement clinker to calcium oxide is 1 to 3:1, and the hydration activator accounts for 5% to 10% of the mass of the composite expansion source.

[0012] In a preferred embodiment, the mass ratio of the hydroxyl-terminated polybutadiene to the polyurethane prepolymer is 1:0.5 to 1.5; the mass percentage of the plasticizer is 5% to 15% based on the mass of the modified elastomer, and the mass percentage of the crosslinking agent is 0.5% to 1.5%.

[0013] The hydration activator is sodium sulfate, potassium sulfate, or gypsum; the plasticizer is dioctyl phthalate, dibutyl phthalate, or tributyl acetyl citrate; and the crosslinking agent is toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), or hexamethylene diisocyanate (HDI).

[0014] In a preferred embodiment, the water-cement ratio of the cement-based composite grouting material is 0.20 to 0.23.

[0015] In a preferred embodiment, the silicate cement is 52.5 silicate cement, and the metakaolin has a specific surface area ≥15m². 2 / g, the specific surface area of ​​the silica fume is ≥12m² 2 / g, wherein the aggregate is quartz sand with a particle size D≤150μm.

[0016] In a preferred embodiment, the admixture is composed of the following raw materials in parts by weight: 8 to 12 parts of viscosity-reducing polycarboxylate superplasticizer, 0.2 to 0.5 parts of silicone defoamer, and 0.7 to 1.0 parts of sodium gluconate retarder.

[0017] The viscosity-reducing polycarboxylate superplasticizer used above was purchased from China Building Materials Zhongyan Technology Co., Ltd.; the silicone defoamer was purchased from Henan Qimeng Chemical Technology Co., Ltd.; and the sodium gluconate coagulant was purchased from Xilong Scientific Co., Ltd.

[0018] A second objective of this invention is to provide a method for preparing the cement-based composite grouting material described in any one of the above claims, comprising the following steps: Silicate cement, metakaolin, silica fume, and aggregates are dry-mixed at 300 rpm. Coupled elastic expansion microspheres are added, and the mixture is stirred at 150 rpm to obtain a dry-mix semi-finished product.

[0019] Add mixing water containing admixtures to the dry-mixed semi-finished product and stir at a speed of 800 rpm to obtain a cement-based composite grouting material with a slump extension of 660 mm to 700 mm.

[0020] In the preparation process of the aforementioned cement-based composite grouting material, under factory conditions, silicate cement, metakaolin, silica fume, and aggregates are added to a large planetary mixer (CMP vertical shaft planetary mixer (brand: Conneler)) and dry-mixed at 300 rpm for 10 minutes until the color is uniform. Then, coupled elastic expansion microspheres are slowly and evenly added to the mixer, and the mixer speed is adjusted to 150 rpm, continuing mixing for 15 minutes. This low-speed mixing process aims to fully and gently coat the microspheres with a large amount of inorganic dry powder, preventing the microspheres from clumping due to collision or moisture absorption during storage and transportation, ensuring their flowability and reactivity. After uniform mixing, the dry-mix semi-finished product is obtained.

[0021] At the grouting construction site, the dry-mix semi-finished product is put into a high-speed mixer (GZJ high-speed slurry mixer). According to the designed water-cement ratio, the mixing water containing the additives is added all at once. The mixture is stirred at 800 rpm for 3-5 minutes until the slurry reaches a homogeneous, viscous, and glossy flow state, thus obtaining the cement-based composite grouting material. The slump spread meets the technical requirement of 660mm-700mm. It is worth noting that due to the presence of coupled elastic expansion microspheres, the cement-based composite grouting material exhibits superior thixotropy, being viscous when still and possessing excellent fluidity when stirred, making it highly suitable for pressure grouting.

[0022] The third objective of this invention is to provide a grouting method, which uses the cement-based composite grouting material described in any of the above-mentioned claims, performs grouting at a pressure of 0.5 MPa to 1.0 MPa, and after grouting is completed, cures the grouting body by means of programmed temperature control.

[0023] In the above grouting scheme, the prepared grout, namely cement-based composite grouting material, is injected into a wear-resistant screw grouting pump (GSZB-6A screw grouting pump). The grouting operation is carried out through the preset grouting holes in a low-pressure, slow-injection, bottom-up manner. After the grout overflows from the inspection hole, it is sealed one by one until the design grouting pressure of 0.3MPa~1.2MPa is reached and the pressure is stabilized.

[0024] As a preferred embodiment, the curing process specifically involves: curing at 38℃~42℃ for 4 hours within 1 hour of grouting completion, curing at 58℃~62℃ for 6 hours, and then curing at 78℃~82℃ for 48 hours.

[0025] After grouting, a stepped temperature-controlled curing process is implemented within 1 hour to precisely activate the dual functions of the coupled elastic expansion microspheres. Initial curing (38℃~42℃ for 4 hours) involves maintaining the grouting area temperature at 40℃ by laying insulation blankets and using low-power hot air equipment. This initial curing stimulates rapid hydration of sulfoaluminate cement clinker in the microsphere shell, generating ettringite and causing early expansion, effectively compensating for the plastic shrinkage and early autogenous shrinkage of the grout. Simultaneously, the cement matrix also begins normal hydration. Intermediate curing (58℃~62℃ for 6 hours) steadily raises the grouting area temperature to 60℃. The purpose of intermediate curing is to activate the hydration activity of calcium oxide (CaO) in the microsphere shell, initiating the intermediate expansion process; furthermore, it softens the elastomer of the microsphere core layer, causing it to transition from a glassy state to a highly elastic state, preparing for subsequent interfacial fusion. Late curing (78℃~82℃ for 48 hours) is the core stage of functional coupling. By controlling the temperature at 80℃, the expansion reaction of the coupled elastic expansion microsphere shell layer proceeds continuously and stably, perfectly compensating for the later chemical shrinkage and drying shrinkage of the grout. The elastomer of the coupled elastic expansion microsphere core layer softens fully, slightly expands in volume, and generates strong mechanical interlocking and physicochemical fusion with the surrounding hydrated cement matrix, forming an "anchoring" effect. Ultimately, a large number of uniformly distributed "micro-reinforcing points" with both expansion capacity and excellent flexibility are formed inside the grout. When the grout is subjected to stress, these points can efficiently dissipate energy through their own plastic deformation, thereby endowing the material with ultra-high toughness and post-cracking load-bearing capacity. The above-mentioned stepped temperature-controlled curing process can be achieved by laying insulation blankets, circulating hot water, or adjusting the power of the heat source. After the above steps are completed, the heating equipment can be removed, and subsequent natural curing can be carried out.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a cement-based composite grouting material, comprising silicate cement, metakaolin, and silica fume as the cementitious component, coupled with coupled elastic expandable microspheres as the core functional component, and supplemented with aggregates and admixtures. Compared with existing technologies that use physically compounded polymers, fibers, or single expandable agents, this invention introduces core-shell structured coupled elastic expandable microspheres as the core functional component, achieving an integrated design of expansion and toughening. These microspheres, with a modified elastomer as the core and a composite expansion source as the shell, overcome the technical limitations of traditional technologies where functional components are difficult to coordinate in physically compounded polymers, fibers, or single expandable agents. Furthermore, this invention optimizes the microstructure through active fillers (metakaolin and silica fume) and combines a stepped programmed temperature curing system with the sequential activation of microsphere functions, achieving effective control over the performance of the cement-based composite grouting material.

[0027] At the materials level, this invention integrates the expansion source of the shell layer (compensating for shrinkage) with the toughening phase of the core layer (absorbing energy) at the micrometer scale. This means integrating the two functions of shrinkage compensation (shell layer) and energy absorption toughening (core layer) within a coupled elastic expansion microsphere at the micrometer scale. The modified elastomer in the core layer absorbs and transforms expansion stress, avoiding stress concentration. Simultaneously, the modified elastomer provides a buffer space for expansion, making the expansion effect more continuous and stable, achieving a synergistic effect of expansion and toughening. At the system level, a dense and tough composite structure is constructed through active fillers filling pores, optimizing interfaces, and the skeletal support of aggregates. At the process level, a specific curing regime is designed, activating the gradient function of the microspheres through temperature sequence, thereby precisely matching the performance development of cement-based materials throughout the entire process from early to late stages.

[0028] After grouting with the cement-based composite grouting material prepared according to this invention, the coupled elastic expansion microspheres and the cement matrix form a strong and tough interfacial transition zone under specific curing conditions. Metakaolin and silica fume are used as active fillers, undergoing a pozzolanic reaction to fill the pores, resulting in a denser microstructure and improved later-stage strength and durability. Aggregate (quartz sand) acts as a skeleton, stabilizing volume, reducing shrinkage, and lowering costs. Admixtures synergistically ensure high fluidity, low porosity, and controllable working time, thus achieving high-performance grouting while avoiding defects caused by weak interfaces. Under stress, the material can efficiently dissipate energy through the plastic deformation of the coupled elastic expansion microspheres while maintaining high load-bearing capacity, achieving a balance between ultra-high toughness and high strength. This characteristic significantly improves the crack resistance and service life of the grout under dynamic loads and deformation, enhances long-term volume stability, and effectively solves the technical problems of poor long-term volume stability and crack resistance of existing cement-based grouting materials, as well as insufficient synergistic deformation capacity with old concrete. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation process and grouting method of the cement-based composite grouting material of the present invention.

[0030] Figure 2 The image shows the microstructure of the cement-based composite grouting material prepared in Example 2 of this invention, where (a) is the grouting material in the initial stage of the reaction, and (b) is the final cement-based composite grouting material. Detailed Implementation

[0031] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0032] To address current methods for improving the performance of grouting materials, incorporating polymer emulsions or fibers can enhance toughness. However, polymer emulsions introduce excessive air bubbles and delay setting, while steel fibers are prone to corrosion and unsuitable for grouting fine cracks. Adding expansion agents to compensate for shrinkage is also problematic, as a single expansion source often only works at a specific point in time and cannot match the full-process shrinkage of cement-based materials from early to late stages. Furthermore, controlling the coordination between expansion and strength development is difficult. Moreover, for major projects with stringent durability requirements, existing cement-based grouting materials still fall short in terms of long-term volume stability, crack resistance, and ability to deform in tandem with existing concrete. Based on these technical problems, this invention provides a cement-based composite grouting material, its preparation method, and its grouting method.

[0033] The technical solution of the present invention will be analyzed and described in detail below.

[0034] The present invention first provides a cement-based composite grouting material, which is made of the following raw materials in parts by weight: 650 to 700 parts of silicate cement, 100 to 130 parts of metakaolin, 80 to 90 parts of silica fume, 20 to 35 parts of coupled elastic expansion microspheres, 850 to 950 parts of aggregate, and 8.9 to 13.5 parts of admixture.

[0035] The coupled elastic expansion microspheres are formed by cross-linking a modified elastomer made of hydroxyl-terminated polybutadiene and polyurethane prepolymer as the core layer and a composite expansion source made of sulfoaluminate cement clinker and calcium oxide as the shell layer. The modified elastomer is wrapped with the composite expansion source and cross-linked and cured to form primary microspheres. After aging, an interpenetrating polymer network structure is formed inside the primary microspheres to obtain core-shell structured coupled elastic expansion microspheres.

[0036] The mass ratio of the core to the shell is 1:2 / 3 to 1.5.

[0037] For the core-shell structured coupled elastic expandable microspheres mentioned above, if the shell mass ratio is less than 2 / 3 (i.e., the shell is too thin), the expansion component is insufficient, which cannot effectively compensate for the shrinkage throughout the process, resulting in poor volume stability; moreover, the shell is easily damaged and cannot effectively protect the core layer. If the shell mass ratio is greater than 1.5 (i.e., the shell is too thick), the overall rigidity of the microsphere is too strong, limiting the toughening effect of the core layer; the expansion efficiency per unit mass decreases, and excessive expansion stress will have an adverse effect on the matrix.

[0038] In the above technical solution, by constructing coupled elastic expansion microspheres with a core-shell structure, the expansion source that compensates for the shrinkage of the shell layer and the toughening phase that absorbs energy in the core layer are integrated at the micrometer scale. This allows the expansion stress to be absorbed and transformed by the elastic core layer, thereby avoiding stress concentration. At the same time, the modified elastomer provides a buffer space for expansion, making the expansion effect more continuous and stable, fundamentally solving the problem of the difficulty in synergistic effects of functional components in traditional physical compounding. After grouting with the cement-based composite grouting material prepared by this invention, the coupled elastic expansion microspheres and the cement matrix form a strong and tough interface transition zone under specific curing conditions, avoiding defects caused by weak interfaces. When the material is under stress, it can efficiently dissipate energy through the plastic deformation of the coupled elastic expansion microspheres while maintaining high load-bearing capacity, achieving a unity of ultra-high toughness and high strength. This characteristic significantly improves the crack resistance and service life of the grout under dynamic loads and deformation, and enhances long-term volume stability.

[0039] The technical effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0040] Example 1 A cement-based composite grouting material is made from the following raw materials in parts by weight: 680 parts of PO 52.5 silicate cement, 115 parts of metakaolin (specific surface area ≥18m² / g), 85 parts of silica fume (specific surface area ≥15m² / g), 28 parts of coupled elastic expansion microspheres (shell to core mass ratio of 55:45, sulfoaluminate cement clinker to calcium oxide mass ratio of 2:1 in the shell, particle size range of 50μm~150μm), 900 parts of ultrafine quartz sand (D≤150μm), and admixtures (10 parts of viscosity-reducing polycarboxylate superplasticizer, 0.3 parts of organosilicon defoamer, and 0.8 parts of sodium gluconate retarder).

[0041] The preparation method of the above-mentioned cement-based composite grouting material includes the following steps: S1, Preparation of Coupled Elastic Expansion Microspheres: Using 6.3g of hydroxyl-terminated polybutadiene and 6.3g of polyurethane prepolymer (mass ratio 1:1) as raw materials, 1.26g of plasticizer was added, and the mixture was stirred at 66℃. With the addition of 0.126g of crosslinking agent, a modified elastomer was obtained. Using 10.27g of sulfoaluminate cement clinker and 5.13g of calcium oxide (mass ratio 2:1) as raw materials, 1.232g of hydration activator (sodium sulfate, accounting for 8% of the composite expansion source) was added, and the mixture was ball-milled until the specific surface area was ≥400m². 2 / kg, to obtain the composite expansion source. A core-shell structure was constructed using a fluidized bed granulation and coating machine. The modified elastomer was sprayed into the fluidized bed of the composite expansion source through a pressure atomizing nozzle. The atomized modified elastomer, acting as "seeds," collided, adhered, and coated the shell powder particles of the composite expansion source, which were in a state of vigorous motion. By precisely controlling the fluidizing airflow (28 m³ / h), atomizing pressure (0.3 MPa), and bed temperature (75℃), the surface of the modified elastomer was gradually coated with a uniform layer of the composite expansion source shell powder, and preliminary cross-linking and solidification occurred, forming stable core-shell structured microspheres. Curing and sieving: The obtained microspheres were transferred to a curing chamber and aged at 50℃ for 24 hours to ensure that the cross-linking reaction inside the core layer of the microspheres was fully completed, forming a stable interpenetrating polymer network (IPN) structure. Finally, a vibrating sieve was used to screen out coupled elastic expansion microspheres with a particle size of 50 μm to 150 μm.

[0042] S2. In a factory environment, according to the mass fraction of each raw material, silicate cement, metakaolin, silica fume, and aggregate are added to a CMP vertical shaft planetary mixer (brand: Connele) and dry-mixed at 300 rpm for 10 minutes until the color is uniform. Then, coupled elastic expansion microspheres are slowly and evenly added to the mixer, and the mixer speed is adjusted to 150 rpm, continuing mixing for 15 minutes. This low-speed mixing process aims to fully and gently coat the microspheres with a large amount of inorganic dry powder, preventing the microspheres from clumping due to collision or moisture absorption during storage and transportation, ensuring their fluidity and reactivity. After uniform mixing, a dry-mix semi-finished product is obtained. At the grouting construction site, the dry-mix semi-finished product is added to a GZJ high-speed slurry mixer. At the designed water-cement ratio of 0.22, mixing water containing dissolved additives is added all at once, and the mixture is stirred at 800 rpm for 5 minutes until the slurry reaches a homogeneous, viscous, and glossy flowability with an extension of 690 mm, thus obtaining a cement-based composite grouting material.

[0043] The cement-based composite grouting material prepared above is used for pressure grouting. Specifically, the cement-based composite grouting material is injected into a GSZB-6A screw grouting pump. The grouting operation is carried out through the preset grouting holes using a low-pressure, slow-injection method from bottom to top. After the grout overflows from the inspection holes, they are sealed one by one until the design grouting pressure (1.2MPa) is reached and stabilized. After grouting is completed, curing should begin as soon as possible (no more than 1 hour after grouting is completed). The curing temperature is 40℃ for 4 hours, 60℃ for 6 hours, and then 80℃ for 48 hours to obtain the grouting body.

[0044] Figure 2 The image shown is a microstructure characterization diagram of the cement-based composite grouting material prepared in Example 1. Figure 2(a) shows the expanded microspheres that were not fully hydrated in the early stages of the reaction, demonstrating the tight bond between the microspheres and the gel particles. As the reaction progresses, the microspheres and the remaining gel particles are fully hydrated, and the resulting hydration product, CASH gel, is tightly bound together, forming a stable network structure, such as... Figure 2 As shown in (b), this further ensures the overall toughness of the cement-based composite grouting material.

[0045] Example 2 A cement-based composite grouting material is made from the following raw materials in parts by weight: 700 parts of PO 52.5 silicate cement, 100 parts of metakaolin (specific surface area ≥18m² / g), 90 parts of silica fume (specific surface area ≥15m² / g), 25 parts of functionally coupled elastic expansion microspheres (the proportion of the microsphere shell layer is slightly increased to 58%, that is, the mass ratio of the shell layer to the core layer is 58:42, the mass ratio of sulfoaluminate cement clinker to calcium oxide is 2.5:1, and the particle size range is 50μm~150μm to enhance early expansion), 880 parts of ultrafine quartz sand, and admixtures (11 parts of viscosity-reducing polycarboxylate superplasticizer, 0.4 parts of organosilicon defoamer, and 0.7 parts of sodium gluconate retarder).

[0046] The preparation method of the above-mentioned cement-based composite grouting material includes the following steps: S1, Preparation of Coupled Elastic Expansion Microspheres: Using 5.25g of hydroxyl-terminated polybutadiene and 5.25g of polyurethane prepolymer (mass ratio 1:1) as raw materials, 1.25g of plasticizer was added, and the mixture was stirred at 68℃. With the addition of 0.125g of crosslinking agent, a modified elastomer was obtained. Using 10.36g of sulfoaluminate cement clinker and 4.14g of calcium oxide (mass ratio 2.5:1) as raw materials, 1.16g of hydration activator (sodium sulfate, accounting for 8% of the composite expansion source by mass) was added, and the mixture was ball-milled until the specific surface area was ≥400m². 2 / kg, to obtain the composite expansion source. A fluidized bed granulation and coating machine was used to construct the core-shell structure. The modified elastomer was sprayed into the fluidized bed of the composite expansion source through a pressure atomizing nozzle. The atomized modified elastomer, acting as "seeds," collided, adhered, and coated the shell powder particles of the composite expansion source, which were in a state of vigorous motion. By precisely controlling the fluidizing air volume (30 m³ / h), atomizing pressure (0.2 MPa), and bed temperature (72℃), the surface of the modified elastomer was gradually coated with a uniform shell powder of the composite expansion source, and preliminary cross-linking and solidification occurred, forming stable core-shell structured microspheres. Curing and sieving: The obtained microspheres were transferred to a curing chamber and aged at 48℃ for 24 hours to ensure that the cross-linking reaction inside the core layer of the microspheres was fully completed, forming a stable interpenetrating polymer network (IPN) structure. Finally, a vibrating sieve was used to screen out coupled elastic expansion microspheres with a particle size of 50 μm to 150 μm.

[0047] S2. In a factory environment, according to the mass fraction of each raw material, silicate cement, metakaolin, silica fume, and aggregate are added to a CMP vertical shaft planetary mixer (brand: Connele) and dry-mixed at 300 rpm for 10 minutes until the color is uniform. Then, coupled elastic expansion microspheres are slowly and evenly added to the mixer, and the mixer speed is adjusted to 150 rpm, continuing mixing for 15 minutes. This low-speed mixing process aims to fully and gently coat the microspheres with a large amount of inorganic dry powder, preventing the microspheres from clumping due to collision or moisture absorption during storage and transportation, ensuring their fluidity and reactivity. After uniform mixing, a dry-mix semi-finished product is obtained. At the grouting construction site, the dry-mix semi-finished product is added to a GZJ high-speed slurry mixer. At the designed water-cement ratio of 0.22, mixing water containing dissolved additives is added all at once, and the mixture is stirred at 800 rpm for 3 minutes until the slurry reaches a homogeneous, viscous, and glossy flowability with an extension of 690 mm, thus obtaining a cement-based composite grouting material.

[0048] The cement-based composite grouting material prepared above is used for pressure grouting. Specifically, the cement-based composite grouting material is injected into a GSZB-6A screw grouting pump. The grouting operation is carried out through the preset grouting holes using a low-pressure, slow-injection method from bottom to top. After the grout overflows from the inspection holes, they are sealed one by one until the design grouting pressure (1.0MPa) is reached and stabilized. After the grouting is completed, curing should begin as soon as possible (no more than 1 hour after the completion of grouting). The curing temperature is 40℃ for 4 hours, 60℃ for 6 hours, and then 80℃ for 48 hours to obtain the grouting body.

[0049] Example 3 A cement-based composite grouting material is made from the following raw materials in parts by weight: 650 parts of PO 52.5 silicate cement, 130 parts of metakaolin (specific surface area ≥18m² / g), 80 parts of silica fume (specific surface area ≥15m² / g), 32 parts of functionally coupled elastic expansion microspheres (significantly increasing the amount of microspheres and increasing the core layer ratio to 48%, i.e., the mass ratio of shell layer to core layer is 52:48, the mass ratio of sulfoaluminate cement clinker to calcium oxide in the shell layer is 2:1, and the particle size range is 50μm~150μm, to provide a more significant toughening effect), 950 parts of ultrafine quartz sand, and admixtures (9 parts of viscosity-reducing polycarboxylate superplasticizer, 0.2 parts of organosilicon defoamer, and 1.0 part of sodium gluconate retarder).

[0050] The preparation method of the above-mentioned cement-based composite grouting material includes the following steps: S1, Preparation of Coupled Elastic Expansion Microspheres: Using 7.68g of hydroxyl-terminated polybutadiene and 7.68g of polyurethane prepolymer (mass ratio 1:1) as raw materials, 1.54g of plasticizer was added, and the mixture was stirred at 70℃. With the addition of 0.154g of crosslinking agent, a modified elastomer was obtained. Using 11.09g of sulfoaluminate cement clinker and 5.55g of calcium oxide (mass ratio 2:1) as raw materials, 1.331g of hydration activator (sodium sulfate, accounting for 8% of the composite expansion source by mass) was added, and the mixture was ball-milled until the specific surface area was ≥400m². 2 / kg, to obtain the composite expansion source. A fluidized bed granulation and coating machine was used to construct the core-shell structure. The modified elastomer was sprayed into the fluidized bed of the composite expansion source through a pressure atomizing nozzle. The atomized modified elastomer, acting as "seeds," collided, adhered, and coated the shell powder particles of the composite expansion source, which were in a state of vigorous motion. By precisely controlling the fluidizing airflow (25 m³ / h), atomizing pressure (0.35 MPa), and bed temperature (80℃), the surface of the modified elastomer was gradually coated with a uniform layer of the composite expansion source shell powder, and preliminary cross-linking and solidification occurred, forming stable core-shell structured microspheres. Curing and sieving: The obtained microspheres were transferred to a curing chamber and aged at 52℃ for 24 hours to ensure that the cross-linking reaction inside the core layer of the microspheres was fully completed, forming a stable interpenetrating polymer network (IPN) structure. Finally, a vibrating sieve was used to screen out coupled elastic expansion microspheres with a particle size of 50 μm to 150 μm.

[0051] S2. In a factory environment, according to the mass fraction of each raw material, silicate cement, metakaolin, silica fume, and aggregate are added to a CMP vertical shaft planetary mixer (brand: Connele) and dry-mixed at 300 rpm for 10 minutes until the color is uniform. Then, coupled elastic expansion microspheres are slowly and evenly added to the mixer, and the mixer speed is adjusted to 150 rpm, continuing mixing for 15 minutes. This low-speed mixing process aims to fully and gently coat the microspheres with a large amount of inorganic dry powder, preventing the microspheres from clumping due to collision or moisture absorption during storage and transportation, ensuring their fluidity and reactivity. After uniform mixing, a dry-mix semi-finished product is obtained. At the grouting construction site, the dry-mix semi-finished product is added to a GZJ high-speed slurry mixer. At the designed water-cement ratio of 0.22, mixing water containing dissolved additives is added all at once, and the mixture is stirred at 800 rpm for 5 minutes until the slurry reaches a homogeneous, viscous, and glossy flowability with an extension of 690 mm, thus obtaining a cement-based composite grouting material.

[0052] The cement-based composite grouting material prepared above is used for pressure grouting. Specifically, the cement-based composite grouting material is injected into a GSZB-6A screw grouting pump. The grouting operation is carried out through the preset grouting holes using a low-pressure, slow-injection method from bottom to top. After the grout overflows from the inspection holes, the holes are sealed one by one until the design grouting pressure (0.85MPa) is reached and stabilized. After grouting is completed, curing should begin as soon as possible (no more than 1 hour after grouting is completed). The curing temperature is 40℃ for 4 hours, 60℃ for 6 hours, and then 80℃ for 48 hours to obtain the grouting body.

[0053] To further illustrate the technical effects of the present invention, comparative examples are also provided, as follows: Comparative Example 1 Compared with Example 1, the difference is that 28 parts of coupled elastic expandable microspheres were replaced with a physically mixed mixture of 5.5 parts of CSA expander + 55 parts of lightly calcined magnesium oxide + 15 parts of silane-modified TPU powder.

[0054] The on-site grouting and curing methods adopted conventional curing. After grouting, the grouting was cured under standard curing conditions (20±5℃) until the specified age.

[0055] The performance of the cement-based composite grouting materials prepared in Examples 1 to 3 and Comparative Example 1 of this invention was tested, and the results are shown in Table 1.

[0056] Table 1 Performance Index Test Table of Embodiments and Comparative Examples of the Invention As shown in Table 1, the cement-based composite grouting material of the comparative example of the present invention, due to the absence of any expansion component, exhibits significant shrinkage during the hardening process, visible cracks appear at the interface with the matrix, the 28-day restricted expansion rate is only 0.018%, and the bond strength is only 65% ​​of that of Example 1.

[0057] After grouting is completed, the present invention adopts a stepped temperature control method for curing. The above curing system is highly synergistic with the characteristics of the coupled elastic expansion microspheres. Its temperature curve can sequentially activate the gradient expansion and toughening function of the coupled elastic expansion microspheres. This active regulation ensures the volume stability of the grouting body throughout the entire process from the early stage to the later stage, so that it is tightly bonded to the matrix and effectively overcomes the inherent shrinkage problem of cement-based materials.

[0058] This invention replaces multiple single functional components with coupled elastic expandable microspheres, simplifying the formulation. Factory prefabrication ensures uniform dispersion and stability of the functional components, solving the material agglomeration problem at the source of the process. On-site construction requires only the addition of water and mixing, significantly reducing reliance on complex processes and guaranteeing consistent and repeatable project quality.

[0059] This invention introduces the design concept of ultra-high performance concrete (UHPC) into the field of grouting. The resulting cement-based composite grouting material has the comprehensive advantages of ultra-high strength, ultra-high toughness, micro-expansion characteristics and good fluidity. Its durability is significantly better than that of traditional grouting materials. It is particularly suitable for the reinforcement and repair of major projects with high durability and high crack resistance requirements, such as cross-sea tunnels, deep mines, and hydropower dams.

[0060] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A cement-based composite grouting material, characterized in that, It is made from the following raw materials in parts by weight: 650 to 700 parts silicate cement, 100 to 130 parts metakaolin, 80 to 90 parts silica fume, 20 to 35 parts coupled elastic expansion microspheres, 850 to 950 parts aggregate, and 8.9 to 13.5 parts admixture. The coupled elastic expansion microspheres are formed by cross-linking a modified elastomer made of hydroxyl-terminated polybutadiene and polyurethane prepolymer as the core layer and a composite expansion source made of sulfoaluminate cement clinker and calcium oxide as the shell layer. The modified elastomer is wrapped with the composite expansion source and cross-linked and cured to form primary microspheres. After aging, an interpenetrating polymer network structure is formed inside the primary microspheres to obtain core-shell structure coupled elastic expansion microspheres. The mass ratio of the core to the shell is 1:2 / 3 to 1.

5.

2. The cement-based composite grouting material according to claim 1, characterized in that, The preparation method of the coupled elastic expandable microspheres includes the following steps: Using hydroxyl-terminated polybutadiene and polyurethane prepolymer as raw materials, plasticizers are added and mixed at 60℃~70℃. Under the action of a crosslinking agent, a modified elastomer is obtained. Using sulfoaluminate cement clinker and calcium oxide as raw materials, a hydration activator was added, mixed, and ball-milled to obtain a composite expansion source; The modified elastomer is atomized into droplets, which are then encapsulated by a composite expansion source and cross-linked and cured to obtain primary microspheres. After aging, an interpenetrating polymer network structure is formed inside the primary microspheres, resulting in coupled elastic expansion microspheres with a particle size of 50 μm to 150 μm.

3. The cement-based composite grouting material according to claim 2, characterized in that, The mass ratio of the sulfoaluminate cement clinker to calcium oxide is 1 to 3:1, and the hydration activator accounts for 5% to 10% of the mass of the composite expansion source.

4. The cement-based composite grouting material according to claim 2, characterized in that, The mass ratio of the hydroxyl-terminated polybutadiene to the polyurethane prepolymer is 1:0.5 to 1.5; the mass percentage of the plasticizer is 5% to 15% based on the mass of the modified elastomer, and the mass percentage of the crosslinking agent is 0.5% to 1.5%.

5. The cement-based composite grouting material according to claim 1, characterized in that, The water-cement ratio of the cement-based composite grouting material is 0.20 to 0.

23.

6. The cement-based composite grouting material according to claim 1, characterized in that, The silicate cement is 52.5 silicate cement, and the metakaolin has a specific surface area ≥15m². 2 / g, the specific surface area of ​​the silica fume is ≥12m² 2 / g, wherein the aggregate is quartz sand with a particle size D≤150μm.

7. The cement-based composite grouting material according to claim 1, characterized in that, The additive is composed of the following raw materials in parts by weight: 8 to 12 parts of viscosity-reducing polycarboxylate superplasticizer, 0.2 to 0.5 parts of silicone defoamer, and 0.7 to 1.0 parts of sodium gluconate retarder.

8. A method for preparing a cement-based composite grouting material according to any one of claims 1 to 7, characterized in that, Includes the following steps: Silicate cement, metakaolin, silica fume and aggregate are dry-mixed at 300 rpm, coupled elastic expansion microspheres are added, and stirring is continued at 150 rpm to obtain a dry-mix semi-finished product. Add mixing water containing admixtures to the dry-mixed semi-finished product and stir at a speed of 800 rpm to obtain a cement-based composite grouting material with a slump extension of 660 mm to 700 mm.

9. A grouting method, characterized in that, The cement-based composite grouting material according to any one of claims 1 to 7 is used for grouting at a pressure of 0.5 MPa to 1.0 MPa. After grouting is completed, the grouting body is cured by programmed temperature control.

10. The grouting method according to claim 9, characterized in that, The curing process specifically involves: curing at 38℃~42℃ for 4 hours within 1 hour of grouting completion, curing at 58℃~62℃ for 6 hours, and then curing at 78℃~82℃ for 48 hours.

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