An alkali-activated inorganic adhesive with low drying shrinkage, its preparation method and application

Abstract

This invention discloses an alkali-activated inorganic adhesive with low drying shrinkage, its preparation method, and its application, belonging to the technical field of inorganic adhesive modification. It comprises a solid component and a liquid component. By weight, the solid component includes 15-20 parts MK, 60-80 parts BFS, and 1-25 parts of modifying material; the liquid component includes 41.82-62.74 parts of an alkaline activator and 9.68-13.68 parts of water; the alkaline activator is a compound solution obtained by mixing NaOH and water glass solution; the modifying material is selected from one or more of calcium carbonate whiskers, bentonite, steel slag, and polyethylene glycol. This invention deeply optimizes the microstructure of the inorganic adhesive through multiple synergistic mechanisms, including physical filling, whisker bridging, chemical activation and interface optimization, micro-expansion effect, reduction of surface tension in the pore solution, and formation of an "elastic buffer layer," significantly reducing internal porosity and defects and substantially enhancing its anti-shrinkage properties.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic adhesive modification, and particularly relates to an alkali-activated inorganic adhesive with low drying shrinkage, its preparation method, and its application. Background Technology

[0002] With the acceleration of urbanization and the increasing service life of buildings, the demand for structural reinforcement is growing daily. Among numerous reinforcement technologies, fiber-reinforced polymer (FRP) reinforcement stands out due to its advantages such as lightweight, high strength, corrosion resistance, and convenient construction. Adhesives, as the "key link" for achieving synergistic work between FRP and existing structures, are becoming increasingly important. Alkali-activated inorganic adhesives, due to their high-temperature resistance, low carbon footprint, environmental friendliness, and fire retardancy, are gradually becoming an ideal substitute for traditional epoxy resin-based organic adhesives, demonstrating significant application potential in high-temperature service scenarios such as tunnels and bridges. The working performance, mechanical properties, and drying shrinkage properties of alkali-activated inorganic adhesives largely depend on the precursors used. Blast furnace slag (BFS) and metakaolin (MK) are two commonly used precursors. Existing research indicates that alkali-activated inorganic adhesives prepared from these two single materials do not perform ideally, but there is potential for complementarity in engineering performance between these two precursors. Therefore, some scholars have combined the two to prepare alkali-activated MK-BFS inorganic gel, and found that after proper combination, BFS dissolves rapidly and reacts with OH in the system. - SiO3 2- The reaction generates NASH and C-(A)-SH gels, which accelerates the polymerization rate of the composite system, optimizes the internal microstructure, and effectively improves the engineering performance.

[0003] However, alkali-activated MK-BFS inorganic adhesives still face numerous challenges in practical engineering applications due to their composite systems. The incorporation of active BFS, multiple components, and variability in activator / moisture content increase the difficulty of performance control, particularly in terms of drying shrinkage. Significant deficiencies are exposed in its drying shrinkage performance; the large drying shrinkage easily leads to internal stress concentration, causing microcracks on the surface of the hardened body, thus weakening the overall performance of the inorganic adhesive. Simultaneously, cracking further affects its bonding performance and toughness, making it difficult to bond firmly to the substrate and prone to peeling under deformation loads, thus restricting its large-scale engineering application and promotion. Therefore, exploring efficient shrinkage reduction strategies and shrinkage modification technologies for alkali-activated MK-BFS inorganic adhesives, analyzing its drying shrinkage behavior and mass loss patterns, and revealing its microstructural characteristics and shrinkage reduction mechanism have become urgent problems to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an alkali-activated inorganic adhesive with low drying shrinkage, its preparation method and application, so as to solve the problems mentioned in the background art or achieve better technical effects.

[0005] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention. This invention discloses an alkali-activated inorganic adhesive with low drying shrinkage, comprising a solid component and a liquid component. By weight, the solid component comprises 15-20 parts MK, 60-80 parts BFS, and 1-25 parts modified material; the liquid component comprises 41.82-62.74 parts alkaline activator and 9.68-13.68 parts water; the mass ratio of the solid component to the liquid component is 1.42-1.62:1.

[0006] The alkaline activator is a compound solution obtained by mixing NaOH and water glass solution; the mass ratio of NaOH to water glass solution is 0.16~0.25:1;

[0007] The modified material is selected from one or more of calcium carbonate whiskers, bentonite, steel slag and polyethylene glycol.

[0008] Further, by weight, the liquid component comprises 52.28 parts of alkaline activator and 13.68 parts of water; in the alkaline activator, the mass ratio of NaOH to water glass solution is 8.43:43.85.

[0009] Furthermore, the MK particles have a particle size range of 0.36~66.9μm and a specific surface area of ​​188.4~220.6m². 2 / kg; the particle size range of the BFS is 0.31~76.0μm, and the specific surface area is 208.5~225.9m². 2 / kg.

[0010] Furthermore, in the alkaline activator, the water glass modulus is 1.0~1.4 and the Na2O content is 8.0~12.0%.

[0011] Furthermore, the calcium carbonate whiskers have a size of 0.31~45.6 μm and a specific surface area of ​​956.3~986.8 m². 2 / kg and pH value is 8.0~10.0.

[0012] Furthermore, the specific surface area of ​​the bentonite is 395.2~440.6 m². 2 / kg, the SiO2 and Al2O3 content in bentonite is 83.59%~89.45%, and the CaO content is 1.19%~1.35%.

[0013] Furthermore, the steel slag has a fineness of 600-800 mesh and a specific surface area of ​​430.2-482.8 m². 2 / kg.

[0014] Furthermore, the polyethylene glycol is a linear polymer with an average molecular weight of 1900~2200 Da and a solid density of 1.15~1.26 g / cm³. 3 And the thickness is 100~200nm.

[0015] Furthermore, the calcium carbonate whiskers account for 1.0 to 5.0% of the mass of the solid component.

[0016] Furthermore, the bentonite accounts for 3.0% to 9.0% of the mass of the solid component.

[0017] Furthermore, the steel slag accounts for 5.0% to 25.0% of the mass of the solid components.

[0018] Furthermore, the polyethylene glycol accounts for 1.0 to 3.0% of the mass of the solid component.

[0019] Furthermore, the preparation method of the alkali-activated inorganic adhesive with low drying shrinkage rate described above comprises the following steps:

[0020] S1: NaOH is injected into the water glass solution, and after stirring, a compound solution with a water glass modulus of 1.0~1.4 and a Na2O content of 8.0~12.0% is obtained. After standing for 1 day, an alkaline activator is obtained.

[0021] S2: Add 15-20 parts of MK and 60-80 parts of BFS to a cement paste mixing pot, dry mix for 3 minutes to obtain a mixed powder;

[0022] S3: Add the modified material to the mixed powder obtained in S2 according to the ratio, and stir to obtain the mixture.

[0023] S4: Add 41.82~62.74 parts of alkaline activator prepared in S1 and 9.68~13.68 parts of water to 100 parts of the mixture obtained in S3. After slow stirring and fast stirring, an alkaline activated inorganic adhesive with low drying shrinkage is obtained.

[0024] Furthermore, the application of any of the above-mentioned alkali-activated inorganic adhesives with low drying shrinkage in reinforced concrete.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention utilizes calcium carbonate whiskers (CW), bentonite (CB), steel slag (SG), and polyethylene glycol (PEG) to modify shrinkage materials. It modifies the shrinkage of alkali-activated inorganic adhesives from aspects such as physical filling, whisker bridging, adsorption and microstructure regulation, micro-expansion effect, reduction of surface tension of pore solution, and formation of "elastic buffer layer". This significantly improves the shrinkage resistance of inorganic adhesives and reduces their cracking risk.

[0027] (2) The present invention effectively reduces the porosity of gel pores and mesopores and inhibits the drying shrinkage of alkali-activated MK-BFS inorganic glue by incorporating CW. As the amount of CW increases, the drying shrinkage of the sample decreases. The drying shrinkage value of the sample with a CW content of 5.0% after 28 days is 87.55% of the drying shrinkage value of the blank sample during the same period. CW works synergistically through multiple pathways such as physical filling, whisker bridging, crack deflection, whisker pull-out and fracture to achieve shrinkage reduction and enhancement from multiple aspects such as pore filling, structural strengthening and stress dispersion.

[0028] (3) The present invention effectively inhibits the drying shrinkage of alkali-activated MK-BFS inorganic gel by incorporating CB. As the amount of CB increases, the drying shrinkage of the sample first decreases and then increases. The drying shrinkage of the sample with a CB content of 3.0% after 56 days is reduced by 9.66%, 7.64%, and 9.86% compared with the blank sample and the samples with CB contents of 6.0% and 9.0%, respectively. The small-sized CB particles achieve shrinkage reduction and enhancement in terms of microstructure densification, strengthening gel products, adsorption and microstructure regulation through multiple synergistic effects such as physical filling, water absorption and swelling, chemical activation and interface optimization, and the formation of "maze effect".

[0029] (4) By incorporating an appropriate amount of SG, the present invention reduces the pore volume fraction of the alkali-activated MK-BFS inorganic adhesive, effectively inhibiting the drying shrinkage of the sample. The 56-day drying shrinkage value of the 25.0% SG sample is 9.2% and 5.2% lower than that of the blank sample and the 5.0% SG sample, respectively. SG, with its triple synergistic effect of physical filling, pozzolanic reaction and micro-expansion effect, deeply optimizes the microstructure of the inorganic adhesive, greatly reduces its internal pores and defects, and significantly enhances the material's anti-shrinkage performance and chemical corrosion resistance.

[0030] (5) The present invention effectively inhibits the drying shrinkage of alkali-activated MK-BFS inorganic adhesive by incorporating PEG. As the PEG content increases, the drying shrinkage of the sample first decreases and then increases. When the content is 2.0%, the drying shrinkage value of the sample reaches the lowest value, and its 28-day drying shrinkage value is only 72.4% of that of the blank sample in the same period. PEG achieves crack resistance and shrinkage reduction through multiple pathways such as reducing the surface tension of the pore solution, physically filling and refining the pore structure, adsorbing and slowly releasing water, and forming an "elastic buffer layer".

[0031] (6) The present invention effectively suppresses the drying shrinkage of alkali-activated MK-BFS inorganic adhesive by mixing one or more of the above-mentioned modified materials, giving full play to the synergistic and complementary effects and multi-scale effects of different modified materials, optimizing the pore structure, improving the density of the matrix, effectively transferring and dispersing shrinkage stress, and reducing the risk of cracking; at the same time, the reasonable mixing of different modified materials can also give full play to the multiple action mechanisms of the materials, thereby reducing drying shrinkage while improving compressive strength. Attached Figure Description

[0032] Figure 1 This is a graph showing the effect of different CW dosages on the drying shrinkage of alkali-activated MK-BFS inorganic adhesive.

[0033] Figure 2 This is a graph showing the effect of different CW dosages on the mass loss of alkali-activated MK-BFS inorganic adhesives according to the present invention.

[0034] Figure 3 This is a graph showing the effect of different CW dosages on the compressive strength of alkali-activated MK-BFS inorganic adhesive.

[0035] Figure 4 This is a graph showing the effect of different CB dosages on the drying shrinkage of alkali-activated MK-BFS inorganic adhesive.

[0036] Figure 5 This is a graph showing the effect of different CB dosages on the mass loss of alkali-activated MK-BFS inorganic adhesives according to the present invention;

[0037] Figure 6 This is a graph showing the effect of different CB dosages on the compressive strength of alkali-activated MK-BFS inorganic adhesive.

[0038] Figure 7 This is a graph showing the effect of different SG dosages on the drying shrinkage of alkali-activated MK-BFS inorganic adhesive.

[0039] Figure 8 This is a graph showing the effect of different SG dosages on the mass loss of alkali-activated MK-BFS inorganic adhesives according to the present invention;

[0040] Figure 9 This is a graph showing the effect of different SG dosages on the compressive strength of alkali-activated MK-BFS inorganic adhesive.

[0041] Figure 10 This is a graph showing the effect of PEG dosage on the drying shrinkage of alkali-activated MK-BFS inorganic adhesive in this invention;

[0042] Figure 11 This is a graph showing the effect of PEG dosage on the mass loss of alkali-activated MK-BFS inorganic adhesive in this invention;

[0043] Figure 12This is a graph showing the effect of PEG content on the compressive strength of alkali-activated MK-BFS inorganic adhesive. Detailed Implementation

[0044] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0045] Unless otherwise specified, the raw materials or reagents used in the following examples and comparative examples are commercially available products or products prepared using conventional techniques.

[0046] The metakaolin (MK / K-1100W) used was sourced from Inner Mongolia Chaopai New Materials Co., Ltd.; its density is 2.626 g / cm³. 3 The activity index is 130%; the specific surface area is 188.4~220.6 m². 2 / kg; size ranges from 0.36 to 66.9 μm.

[0047] Blast furnace slag (BFS) is sourced from Anhui Maanshan Iron & Steel Jiahe New Building Materials Co., Ltd.; its density is 2.892 g / cm³. 3 The activity index was 72.6%; the specific surface area was 208.5~225.9 m². 2 / kg; size ranges from 0.31 to 76.0 μm.

[0048] Alkaline activator raw material (water glass solution): Commercially available industrial-grade high-purity water glass solution with a modulus of 3.22, a Baumé degree of 16.5, and a density of 1.38 g / cm³. 3 The composition by weight ratio is: Na₂O 8.50%, SiO₂ 26.80%, water-insoluble matter 0.36%, and water 64.34%. Commercially available NaOH (density 2.13 g / cm³) was used. 3 Adjust the water glass modulus (SiO2 / Na2O) and Na2O content, and age for 1 day before use.

[0049] Based on the mass conservation of SiO2 and Na2O in the solution, the mass of NaOH required to prepare water glass with different moduli can be calculated by the following formula.

[0050] (1)

[0051] In the formula: G is the mass of NaOH required to prepare water glass with different moduli, G1 is the mass of Na2O in high-modulus water glass, and M0 and M x The modulus of high-modulus water glass and the modulus of water glass after preparation are respectively. P and A are the purity of NaOH and the content of Na2O in water glass, respectively. In this invention, P=96% and A=8.5%.

[0052] The shrinkage-modified materials used in this invention are specifically as follows:

[0053] Calcium carbonate whiskers (CW) were sourced from Maclean's, with a density, specific surface area, and pH value of 2.86 g / cm³, 956.3–986.8 m², and respectively. 2 / kg and 8.0~10.0; its shape is needle-like, and its size is 0.31~45.6μm.

[0054] The bentonite (CB) is sourced from Wuxi Dingsheng Technology Co., Ltd., and is primarily in granular form. The material's density, activity index, and specific surface area are 2.668 g / cm³. 3 72.6%, 395.2~440.6m 2 / kg. The SiO2 and Al2O3 content in bentonite is 83.59%~89.45%, and the CaO content is 1.19%~1.35%.

[0055] The steel slag (SG) comes from Maanshan Iron & Steel Co., Ltd., with a fineness of 600-800 mesh. Its density, activity index, and specific surface area are 3.318 g / cm³. 3 65.6%, 430.2~482.8m 2 / kg. Its mineral composition mainly includes C3S, C2S, Ca(OH)2 and a small amount of C2F, and also contains RO phase and f-CaO. The presence of C3S and C2S gives it potential gelling activity. SG contains spherical microspheres with a size of about 1~15 mm.

[0056] Polyethylene glycol (PEG) is sourced from Shandong Yangdao Biotechnology Co., Ltd. PEG is a linear polymer with an average molecular weight of 1900-2200 Da. It is a white, waxy solid at room temperature with a solid density of 1.15-1.26 g / cm³. 3 The melting point is 50~55℃, and the freezing point is 45~50℃. SEM images show that the PEG 2000 film surface exhibits a regular lamellar crystalline structure with a thickness of 100~200nm.

[0057] In each embodiment of the present invention, the alkali-activated MK-BFS inorganic adhesive is cured using standard methods.

[0058] The performance testing method for the alkali-activated MK-BFS inorganic adhesive after shrinkage modification according to the present invention is as follows:

[0059] Drying shrinkage performance: tested according to JGJ / T70-2009.

[0060] Compressive strength: According to GB / T17671-2021; the sample size is 40mm×40mm×160mm. After the sample is cured to the design age, the flexural strength test is carried out first, using an electric flexural testing machine (model: DKZ-6000) with a loading speed of 50N / s±10N / s. Then the compressive strength test is carried out, using a cement pressure testing machine (model: TYE-2000) with a loading speed of 0.5~1.0MPa / s.

[0061] In the following embodiments, the percentage of modified materials (such as calcium carbonate whiskers (CW), bentonite (CB), steel slag (SG), and polyethylene glycol (PEG)) indicates the proportion of the added modified material in the total solid composition (including MK, BFS, and the modified material).

[0062] Example 1

[0063] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.8 parts MK, 79.2 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 1 part CW.

[0064] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0065] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0066] (2) Add 19.8 parts of MK and 79.2 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary paste mixer of model NJ-160B to mix at a speed of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0067] (3) Add 1 part of CW to the mixed powder obtained in step (2) above, and use a planetary paste mixer of model NJ-160B to stir again at a rate of 140r / min for 3min to fully mix it with the mixed powder to obtain a mixture; this process utilizes mechanical stirring to effectively achieve physical filling of CW, reduce porosity, and improve matrix density.

[0068] (4) Add 52.28 parts of the alkaline activator prepared in step (1) to the 100 parts of mixture obtained in step (3). Use a planetary paste mixer of model NJ-160B at a speed of 140r / min for 1min to initially wet and disperse the CW, MK and BFS particles. The alkaline activator can be slowly and evenly dispersed on the surface of the material particles and fully contact the reaction sites. The low speed of stirring in the early stage can prevent the activator and water from splashing out, and can also reduce internal bubbles and avoid local agglomeration. After stirring is completed, stop stirring for 1min. During this period, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and alkaline activator are mixed evenly and avoid local material residue. Then, start the planetary paste mixer of model NJ-160B. The star-shaped paste mixer is used to rapidly stir at a rate of 285 r / min for 2 minutes to accelerate the mixing rate of the composite system, thoroughly disperse the particles, promote vigorous mixing and full reaction of the activator and materials, and improve reaction efficiency. During this process, the system simultaneously undergoes "dissolution-polymerization" and geopolymerization reactions to generate NASH and C-(A)-SH gels. The needle-like CW has the characteristics of high strength and high modulus. When filling the pores, the network structure formed has a bridging stress effect, effectively transferring and dispersing shrinkage stress, and reducing the deformation of the system caused by the concentration of shrinkage stress. At the same time, CW, through the crack deflection mechanism, hinders the development of cracks in the matrix when dispersing the shrinkage stress generated by the gel and guides the cracks to extend along the whisker direction, consuming a large amount of shrinkage stress and improving the toughness of the material.

[0069] (5) Add 13.68 parts of water to the gel obtained in step (4), stir rapidly for 3 minutes, and the alkali-activated MK-BFS inorganic adhesive modified with CW is obtained. By adding an appropriate amount of water, the fluidity of the inorganic adhesive is reasonably adjusted to ensure its bonding effect. During the crack propagation process, the CW will be gradually pulled out or broken. This process requires a lot of energy, which is beneficial to suppressing the shrinkage of the material. In addition, after the CW breaks, the remaining part can still play a role in physical filling and stress dispersion, limiting the further propagation of cracks and effectively alleviating shrinkage deformation.

[0070] Example 2

[0071] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.4 parts MK, 77.6 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 3 parts CW.

[0072] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 1.

[0073] Example 3

[0074] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.0 parts MK, 76.0 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 5 parts CW.

[0075] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 1.

[0076] like Figure 1 As shown, the incorporation of calcium carbonate whiskers (CW) effectively inhibits the drying shrinkage of the samples, and the drying shrinkage value decreases with increasing CW content. The drying shrinkage value of the sample with 5.0% CW content after 28 days is 87.55% of that of the blank sample at the same age. This is mainly because the needle-like CW has a unique spatial structure that can tightly fill its internal pores and form a network structure within the system. When the material is subjected to internal shrinkage stress, CW can effectively disperse and transfer the stress, while reducing capillary tension, playing a role in whisker bridging and stress relief, effectively delaying the formation and propagation of microcracks, thereby reducing the drying shrinkage of the sample. In comparison, the shrinkage reduction effect of CW is more obvious in the early stage of curing. After 8 hours of curing, the average shrinkage rate of the sample with 5.0% CW content is only 62.00% of that of the blank sample. This is because the CW has a small diameter and is relatively dispersed in the material, easily clogging pore channels and hindering internal moisture migration. At the same time, the whiskers themselves have wetting properties and can adsorb some moisture, reducing water seepage pores and thus reducing drying shrinkage. Since the main component of CW is CaCO3, the finely dispersed CaCO3 can act as a crystal nucleus, and a large amount of free Ca in the system... 2+ Diffusion onto the surface of CaCO3 particles and physical adsorption provide numerous initial nucleation sites for Ca(OH)2 nucleation, accelerating its formation and thus promoting the formation of C-(A)-SH gel. With prolonged curing time, the products such as Ca(OH)2, C-(A)-SH, and NASH increase, accelerating internal shrinkage. The CW, which mainly bears the load stress, fractures, reducing its effectiveness in inhibiting drying shrinkage. The drying shrinkage pattern of the sample after 120 days of curing is almost identical to that after 90 days of curing, indicating that the system reaction tends to stabilize and the drying shrinkage gradually approaches a constant value.

[0077] like Figure 2As shown, during the initial 8 hours of curing, the blank sample exhibited the most significant mass loss, reaching 9.223 g / kg, while the sample with 5.0% CW doping only lost 5.395 g / kg. This is because nano-sized CW can effectively fill the internal pore structure, reducing water loss due to excessive porosity. With prolonged curing, the mass loss of the samples gradually increased. At 7 days of curing, the mass loss of the CW-doped samples significantly increased, with increases of 54.28%, 52.41%, and 68.18% for samples with 1.0%, 3.0%, and 5.0% doping, respectively, compared to the 3-day samples. This is mainly because CW promotes the reaction of the MK-BFS inorganic gel, generating C-(A)-SH and NASH gels that coat the whisker surface, leading to increased porosity and accelerated evaporation and loss of moisture within the system. After 56 days, the mass loss of the samples tended to stabilize, showing a trend of first increasing and then decreasing with increasing CW doping. When the CW content is low, the sample mass loss tends to increase. This is because a small amount of CW is distributed inside the cementitious material, increasing the interfacial transition zone of the system and promoting rapid evaporation and loss of water, thus exacerbating sample water loss. Furthermore, at relatively low content (e.g., 1.0%, 3.0%), the promoting effect of CW on the internal reaction is relatively limited, leading to severe water loss in the early stages, reduced bound water content, and increased sample mass loss. However, when the content reaches 5.0%, the excessive incorporation of CW can accelerate the system reaction, which is beneficial to the formation of bound hydrogels, thereby alleviating sample mass loss. With further extension of the curing period, the mass loss of the 90-day and 120-day samples did not change significantly compared to the 56-day sample. This indicates that adding an appropriate amount of CW can not only effectively inhibit mass loss in the early stages of curing but also maintain a high bound water content in the later stages of curing, thus effectively controlling sample mass loss.

[0078] like Figure 3 As shown, the compressive strength of the samples initially increases and then decreases with increasing CW content. Compared to the blank sample, the 28-day compressive strength of samples with CW content of 1.0% and 3.0% increased by 5.06% and 15.84%, respectively. This is mainly because the appropriate amount of CW can fully utilize its filling effect, optimize pore size distribution, and improve the internal density of the matrix; at the same time, CW is tightly bonded to the matrix, not only dispersing the stress on the matrix and hindering the development of internal cracks, but also improving the compressive strength of the material. However, excessive CW content will have an adverse effect on the compressive strength of the samples. Compared to the sample with 3.0% CW content, the 28-day compressive strength of the sample with 5.0% CW content decreased by 12.25%, confirming that the filling effect of CW on the internal pores of the structure is related to its content. This is mainly because when the CW content is too high, the agglomeration phenomenon between whiskers is obvious, the whisker distribution in the matrix is ​​uneven and the dispersion is low, increasing the porosity and resulting in a less dense microstructure, thereby reducing its compressive strength. Figure 3It was also observed that the compressive strength of the specimens gradually increased with the extension of the curing period. Furthermore, the incorporation of CW promoted the development of the specimens' compressive strength; the 7-day compressive strength of the specimen with a CW content of 3.0% reached 96.12% of its 28-day compressive strength. This indicates that the incorporation of CW can accelerate the system reaction and improve the early compressive strength of the specimens.

[0079] The CW in Examples 1-3 mainly achieves shrinkage reduction and enhancement through multiple synergistic effects of physical filling, whisker bridging, crack deflection, whisker pull-out and fracture, from pore filling, structural strengthening to stress dispersion. First, the needle-like CW not only inhibits drying shrinkage by absorbing free water and reducing capillary tension, but also works synergistically with the gel to achieve effective physical filling, refine the internal pore structure, reduce the proportion of macropores, and decrease pore connectivity, thereby reducing shrinkage caused by water loss. Second, CW itself has high strength and high modulus. The network structure formed when filling pores has a bridging stress effect, forming numerous tiny "bridges" inside the material to connect and support adjacent gel particles, effectively transferring and dispersing shrinkage stress, thereby reducing deformation caused by stress concentration. Third, through the crack deflection mechanism, CW, while dispersing shrinkage stress, hinders crack development in the matrix and guides crack propagation along the direction of whiskers, consuming a large amount of shrinkage stress and improving material toughness. At the same time, during crack propagation, CW is gradually pulled out or fractured, a process that consumes a large amount of energy, which helps to inhibit material shrinkage. In addition, after CW fractures, the remaining part can still play a certain role in physical filling and stress dispersion, limiting further crack propagation and effectively alleviating sample shrinkage deformation.

[0080] Example 4

[0081] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.4 parts MK, 77.6 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 3 parts CB.

[0082] The modification method for the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0083] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0084] (2) Add 19.4 parts of MK and 77.6 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary paste mixer of model NJ-160B to mix at a speed of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0085] (3) Add 3 parts CB and 13.68 parts water to a beaker and ultrasonically disperse for 20 minutes using a KH2200B ultrasonic disperser to obtain a uniform CB suspension. Ultrasonic treatment can quickly and uniformly disperse CB particles, effectively prevent particle agglomeration, and improve the dispersibility and stability of CB; 20 minutes of ultrasonic treatment is too short and the dispersion is insufficient, while too long a time can easily cause secondary agglomeration. The addition of an appropriate amount of water is beneficial to the uniform dispersion of powdered CB and can also reasonably adjust the flowability of inorganic adhesive to ensure its bonding effect.

[0086] (4) Inject the CB suspension prepared in step (3) into the mixed powder obtained in step (2), and stir at a rate of 140 r / min for 3 min using a cement paste mixer of model NJ-160B. After the materials are uniformly mixed, a mixture is obtained. In this process, mechanical stirring ensures that the prepared CB suspension and the mixture are in full contact. Based on the micro-size effect, CB fills and embeds itself in the micropores better, improving the density of the matrix.

[0087] (5) Inject 52.28 parts of the alkaline activator prepared in step (1) into the mixture obtained in step (4). Use a planetary paste mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min to initially wet and disperse the MK and BFS particles, ensuring full contact between the mixture and the particles. Low-speed stirring in the early stage can prevent the activator and water from splashing out, and can also reduce internal bubbles and avoid local agglomeration. After stirring is completed, stop stirring for 1 min. During this period, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and alkaline activator are mixed evenly and avoid local material residue. Then, start the paste mixer to stir quickly at a rate of 285 r / min for 2 min to accelerate the mixing rate of the mixture system, thoroughly disperse the particles, further mix the material evenly and improve the fluidity, and shorten the total stirring time to obtain the alkali-activated MK-BFS inorganic glue modified with CB. This process involves simultaneous "dissolution-polymerization" and geopolymerization reactions, generating NASH and C-(A)-SH gels. The CB sheets disperse in the matrix, forming a "maze effect" that hinders the migration channels of water and ions, reduces permeability, and thus refines the pore structure. In addition, during the crack propagation process of the prepared inorganic gel, CB particles can be adsorbed on the surface of unreacted MK and BFS particles, reducing the interfacial porosity between the cementitious phase and the aggregate, enhancing the interfacial bonding force, reducing the weakness of the interfacial transition zone, and at the same time, its sheet structure can induce crack deflection, thus inhibiting cracking.

[0088] Example 5

[0089] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 18.8 parts MK, 75.2 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 6 parts CB.

[0090] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 4.

[0091] Example 6

[0092] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 18.2 parts MK, 72.8 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 9 parts CB.

[0093] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 4.

[0094] like Figure 4As shown, the incorporation of CB effectively suppressed the drying shrinkage of the samples, but with the increase of CB dosage, the drying shrinkage of the samples showed a trend of first decreasing and then increasing. The drying shrinkage of the 3.0% CB-doped sample after 56 days was reduced by 10.69%, 10.93%, and 8.27% compared with the blank sample and the samples with CB dosages of 6.0% and 9.0%, respectively. This is mainly because montmorillonite in CB has a typical layered crystal structure, and when an appropriate amount is incorporated, the ionic bonds in the structure (such as Na+) are reduced. + Due to damage, fracture, bending, defects, or irregular stacking of crystal layers, variable charges are generated. Appropriate variable charges lead to electrostatic repulsion between particles. During drying, this repulsion prevents particles from approaching each other, thus inhibiting sample drying shrinkage. Furthermore, exposed Fe-OH, Al-OH, and Si-OH hydroxyl groups at the lattice edges increase their surface potential in solution due to protonation and deprotonation, increasing the electrostatic repulsion between particles. Combined with the hydrophilicity and irregular macroscopic structure of CB, it exhibits strong adhesion when mixed with water, causing CB particles to tightly aggregate. As moisture begins to evaporate, the adhesion between particles prevents separation, further inhibiting sample shrinkage. Appropriate CB incorporation forms a gel network structure, thereby improving sample strength and stability. However, excessive CB incorporation leads to a large number of CB particles being trapped within, disrupting this continuous structure. Simultaneously, uneven distribution of CB particles within the material can also cause structural changes in localized areas. When materials are affected by external factors (such as temperature changes, humidity changes, etc.), microcracks appear in these weak areas and gradually expand as the curing period increases, thereby increasing the drying shrinkage of the sample.

[0095] In addition, by Figure 4 It was also found that the incorporation of CB had a more significant inhibitory effect on the early drying shrinkage of the sample. The 8-hour drying shrinkage of the 3.0% CB sample was 64.40% of that of the blank sample, while its 56-day drying shrinkage reached 90.34% of that of the blank sample. This is mainly because, as the reaction progresses, the attractive forces within the system bring the particles closer together, causing shrinkage, while the repulsive forces are generated by the surface charge of the particles, hindering the particles from approaching each other. The attractive and repulsive forces between the particles gradually reach a balance, which to some extent limits the shrinkage of the sample.

[0096] like Figure 5As shown, the addition of appropriate amounts of CB can reduce the mass loss of samples at different ages, but excessive CB addition will increase the mass loss of the samples. The mass loss of the blank sample at 56 days reached 25.92 g / kg, while the mass loss of the sample with 3.0% CB was 21.77 g / kg, only 83.98% of that of the blank sample. However, when the CB content increased from 3.0% to 9.0%, the mass loss of the sample increased by 31.14%. Since the main components of CB are montmorillonite and a small amount of other minerals, appropriate CB addition can fill the internal pores of the material; CB has a strong adsorption effect on water, and when it is mixed with water, a large amount of adsorbed water will be added to the system, slowing down the loss rate of free water; at the same time, the water adsorbed by CB can maintain the internal humidity environment of the sample, preventing the sample from developing microcracks due to drying, thereby reducing the mass loss of the sample. However, excessive CB doping leads to increased sample mass loss, which is related to CB's strong hygroscopicity. Due to its layered crystal lattice, water molecules can be adsorbed between the crystal layers, existing in the form of hydrated cations. When exposed to a dry environment, these water molecules are removed from the crystal layers, reducing the sample mass. Furthermore, with increasing CB doping, montmorillonite forms a thixotropic gel, gradually transforming into a sol. The sol has a high density and is water-repellent, causing CB to lose water and damaging its original properties. Its adhesiveness and plasticity decrease, its internal structure is destroyed, and some products detach, further increasing sample mass loss.

[0097] It is not difficult to observe that the mass loss of the samples gradually increases with the increase of the curing period. After 56 days, the mass loss of both the blank sample and the CB-doped sample tends to stabilize. This is because the residual water inside the sample is strongly bound water adsorbed on the particle surface. The polar water molecules in this strongly bound water not only bind with oxygen atoms and OH groups on the clay mineral matrix surface, but also... - The covalent bonds between the molecules also lead to hydration reactions with cations on the surface and between crystal layers of clay minerals, forming a cation hydration shell. Due to the extremely strong adsorption of the strongly bound water, the sample mass loss tends to stabilize.

[0098] like Figure 6As shown, the addition of CB has no significant effect on improving the compressive strength of the samples, and may even reduce the compressive strength at 1 day. Appropriate CB addition can slightly improve the compressive strength at 3 days, 7 days, and 28 days, but excessive CB addition will have an adverse effect on the compressive strength. The 28-day compressive strength of the sample with 3.0% CB addition is 4.27% higher than that of the blank sample, while the 28-day compressive strength of the samples with 6.0% and 9.0% CB addition is 1.57% and 31.3% lower than that of the blank sample, respectively. The addition of appropriate CB can enhance the compressive strength mainly because the reaction generates colloidal particles mainly composed of montmorillonite. These particles have a large specific surface area and surface energy, and can adsorb a large number of water molecules to form a viscous gel-like substance. They can react with the products in the system to form a complex and stable three-dimensional network structure, thereby improving the compressive strength. Simultaneously, the silicon-aluminum tetrahedra and aluminum-oxygen octahedra within the montmorillonite lattice in CB can partially dissolve in an alkaline environment, releasing Si... 4+ And Al 3+ With Na in the alkaline activator + The β-carbohydrate (CB) binds to form a NASH gel, thereby improving the compressive strength of the sample. However, excessive CB incorporation can cause montmorillonite to absorb too much water and swell, affecting its internal microstructure. Furthermore, it increases the number of fine particles in the system, reducing interparticle friction and making it difficult to form a tight packing during molding. This poor particle packing leads to increased porosity within the sample, resulting in more harmful macropores. Under pressure, these pores become stress concentration points, leading to microcracks and reducing the compressive strength of the sample. Figure 6 It was also observed that the compressive strength of the samples gradually increased with the extension of the curing period. Notably, the incorporation of CB was detrimental to the early development of compressive strength; the 1-day compressive strength of CB-incorporated samples was lower than that of the blank sample. The 1-day compressive strength of samples with CB incorporation at dosages of 3.0%, 6.0%, and 9.0% were 92.05%, 74.87%, and 59.23% of that of the blank sample, respectively. This is mainly due to the presence of Na in the activator. + and SiO3 2- The reaction of silica-alumina raw materials such as BFS is crucial. In the early stages of the reaction, CB adsorbs these ions, resulting in a reduction in the amount of excitation actually participating in the reaction of silica-alumina raw materials. This is not conducive to the "dissolution-condensation" and geopolymerization reactions, thereby reducing the formation of gel products and affecting the early strength development of the sample.

[0099] In Examples 4-6, CB mainly achieves shrinkage reduction and enhancement through multiple synergistic effects such as physical filling, water absorption and swelling, chemical activation and interface optimization, and the formation of the "maze effect," thereby achieving shrinkage reduction and enhancement from multiple aspects, including microstructure densification, strengthening of gel products, adsorption, and microstructure regulation. First, the lamellar structure and fine particles of CB can fill the pores in the matrix, reducing porosity, optimizing particle size distribution, and improving matrix density. Simultaneously, due to its water absorption and expansion, its volume increases, filling microcracks caused by shrinkage, offsetting drying shrinkage stress, and reducing the total shrinkage rate of the sample. Second, the montmorillonite in CB is rich in active SiO2 and Al2O3, which partially dissolve under the action of an alkaline activator, releasing aluminosilicate monomers to participate in the formation of C-(A)-SH gel, increasing the content of the cementitious phase and strengthening the three-dimensional network structure of the cementitious products. Third, CB particles in the system can adsorb onto the surface of unreacted MK and BFS particles, reducing interfacial porosity between the cementitious phase and aggregate, enhancing interfacial bonding, and reducing the weakness of the interfacial transition zone. Simultaneously, its lamellar structure can induce crack deflection, playing a role in crack suppression. Finally, the layered structure and negative surface charge of CB can adsorb free water molecules in the system, reducing shrinkage caused by evaporation, while also adsorbing Cl... - SO4 2- Harmful ions are reduced, their migration rate is decreased, and their plates disperse in the matrix to form a "maze effect," which hinders the migration channels of water and ions, reduces permeability, and thus refines the pore structure.

[0100] Example 7

[0101] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19 parts MK, 76 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 5 parts SG.

[0102] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0103] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0104] (2) Add 19 parts of MK and 76 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary paste mixer of model NJ-160B to mix at a speed of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0105] (3) Add 5 parts of SG to the above mixed powder and stir again at a speed of 140r / min for 3min using a planetary paste mixer of model NJ-160B to fully mix SG with the mixed powder to obtain a mixture. This process uses mechanical stirring to ensure that the fine particles of SG can effectively fill the gaps between the particles of MK and BFS, achieve physical filling, improve the density of the mixture, and provide a more stable matrix structure for subsequent reactions.

[0106] (4) Add 52.28 parts of the alkaline activator prepared in step (1) to 100 parts of the mixture obtained in step (3). Use a planetary paste mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min, so that the alkaline activator can be slowly and evenly dispersed on the surface of the material particles, fully contact the reaction sites, reduce bubbles and control the reaction rate, avoid local agglomeration of the mixture, and prevent the activator from splashing out. After stirring, stop stirring for 1 min. During this period, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and alkaline activator are mixed evenly. To avoid local material residue, a planetary paste mixer (model NJ-160B) was then started and rapidly stirred at 285 r / min for 2 minutes to accelerate the mixing rate of the mixture, thoroughly disperse the particles, promote vigorous mixing of the activator and the material, make the reaction more complete, and improve the reaction efficiency. During this process, the system simultaneously undergoes "dissolution-polymerization" and geopolymerization reactions to generate NASH and C-(A)-SH gels. The rough microstructure of the SG surface can provide more nucleation sites for the gel reaction, promote heterogeneous nucleation of the gel, accelerate the formation and solidification of the gel network, and indirectly improve early strength and structural stability.

[0107] (5) Add 13.68 parts of water to the gel obtained in step (4), stir rapidly for 3 minutes, and the alkali-activated MK-BFS inorganic adhesive modified with SG is obtained; by adding an appropriate amount of water, the fluidity of the inorganic adhesive is reasonably adjusted to ensure its bonding effect. The high fineness (large specific surface area) and gradation characteristics of SG particles enable them to fill the pores between particles, form a denser particle packing structure, improve the contact between matrix particles, and provide a more uniform internal environment for the gel reaction.

[0108] Example 8

[0109] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 17 parts MK, 68 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 15 parts SG.

[0110] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 7.

[0111] Example 9

[0112] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 15 parts MK, 60 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 25 parts SG.

[0113] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 7.

[0114] like Figure 7 As shown, the incorporation of SG effectively suppresses the drying shrinkage of the samples. Furthermore, the drying shrinkage decreases with increasing SG dosage, reaching its lowest value at 25.0%, with a 56-day drying shrinkage of 9.938 mm / m, representing a reduction of 9.19% and 5.24% compared to the blank sample and the 5.0% dosage sample, respectively. Because SG contains mineral phases such as C3S and C2S, it reacts to form crystals such as Ca(OH)2. These crystals themselves undergo almost no drying shrinkage. Simultaneously, due to the high hardness of SG particles, the unhydrated SG particles and the crystallized products act as a framework within the system, effectively suppressing the drying shrinkage of the samples. Clearly, with the extension of the curing period, the drying shrinkage values ​​of samples with different SG dosages gradually increase, and the drying shrinkage of all samples tends to stabilize at 90 days. This is due to two factors. First, the pore structure inside the sample becomes increasingly refined, and the capillary network gradually closes. The dense microstructure creates resistance to moisture migration, reducing capillary tension caused by moisture evaporation. Second, the humidity inside the sample tends to be in equilibrium with the ambient humidity, and the moisture gradient disappears. At this point, the shrinkage process driven by the humidity difference stops due to the loss of driving force.

[0115] like Figure 8As shown, the incorporation of SG effectively reduces sample mass loss. Compared with the blank sample, the mass loss of the sample with 25.0% SG content is reduced by 29.2%. With increasing SG content, the mass loss of the sample gradually decreases. Compared with the sample with 5.0% SG content, the mass loss of the sample with 25.0% SG content is reduced by 12.5%. This is because, on the one hand, SG particles are smaller and more widely distributed, effectively filling the capillary pores and microcracks in the internal structure, reducing internal porosity and thus increasing matrix density; on the other hand, the dense internal structure reduces the penetration paths of moisture and harmful ions, thereby delaying deterioration and reducing mass loss caused by moisture evaporation or chemical corrosion. Meanwhile, the figure also shows that the mass loss of the sample gradually increases with the curing age. The mass loss of the 15.0% SG content sample at 120 days is 14.34% greater than that of the 7-day sample. The gradual increase in sample mass loss with increasing age may be due to multiple factors. During curing, the system continuously hydrates, chemical reactions consume some substances, and gas escapes, leading to a reduction in sample mass. Meanwhile, moisture evaporation is also a significant factor. During prolonged curing, the internal moisture of the sample continuously dissipates, especially the large amount of free water generated in the early stages of the reaction. This free water gradually evaporates with increasing curing time, resulting in sample mass loss. It is noteworthy that the blank sample and samples with different SG dosages showed relatively significant mass loss in the early stages, while the sample mass tended to stabilize after 56 days. This is because the rapid evaporation of free water on the sample surface and in the internal pores during the early stages of the reaction led to a significant decrease in mass loss. As the curing time increases, the pore structure of the system becomes refined, connectivity decreases, moisture migration is restricted, and the mass tends to stabilize. Comparing the effects of SG dosage on sample mass loss and drying shrinkage reveals an approximately positive correlation between drying shrinkage and mass loss; the smaller the drying shrinkage, the smaller the corresponding sample mass loss.

[0116] Depend on Figure 9 It can be seen that the incorporation of SG has no significant effect on improving the compressive strength of the early 1-day samples. In the early stage of the reaction, due to the presence of inert minerals such as RO phase in SG, it basically does not participate in the hydration reaction, reducing the overall reactivity and the reaction rate of the composite system. This results in a large number of pores in the samples due to incomplete reaction, leading to insufficient matrix compactness. However, the incorporation of SG can significantly improve the compressive strength of the samples at 3 days, 7 days, and 28 days. Moreover, with the increase of SG content, the later compressive strength shows a trend of first increasing and then decreasing. Compared with the blank sample, the 28-day compressive strength of samples with SG content of 5.0% and 15.0% increased by 4.38% and 11.35%, respectively. This is mainly because the BFS reaction is faster in the early stage and lacks Ca in the later stage of hydration. 2+ SG itself has a high CaO content, and the Ca(OH)2 generated in its reaction can increase the base equivalent in the solution, thereby accelerating the hydration of BFS. The Ca in the system... 2+The absorption by BFS further promotes the dissociation and hydration of SG, resulting in a beneficial synergistic hydration effect between SG and BFS. This generates a large amount of C-(A)-SH zeolite-like products, filling the pores formed in the early stages of the reaction, improving the internal structure, and increasing density. However, excessive SG incorporation can adversely affect the compressive strength of the sample. This is because the free MgO and CaO in the system undergo a slow hydration reaction under alkaline activation conditions, resulting in volume expansion. This hydration expansion can cause microcracks in the matrix, disrupting structural integrity and thus affecting its compressive strength.

[0117] In Examples 7-9, SG (Sterile Acid) primarily achieves deep optimization of the microstructure of the cementitious material through the synergistic effects of physical filling, pozzolanic reaction, and micro-expansion, significantly reducing internal porosity and defects, enhancing the material's shrinkage resistance, and effectively minimizing material mass loss. Firstly, regarding physical filling, SG particles exhibit ultra-fine particle size and a globally dispersed distribution. These extremely small SG particles effectively fill the intricate capillary pores and microcracks within the sample. As the filling process continues, the porosity within the sample decreases, significantly improving the overall density of the material, reducing the penetration channels for free water and harmful ions, minimizing mass loss due to moisture evaporation and chemical corrosion, and effectively inhibiting material drying shrinkage. Secondly, the active silicates and aluminates (such as C2S, C3S, and CA) contained in SG undergo a series of complex pozzolanic reactions under alkaline conditions, generating a large amount of C-(A)-SH gel. These gels intertwine, gradually forming a dense gel network structure, further enhancing the matrix's density. Furthermore, the volcanic ash reaction consumes a large amount of Ca(OH)₂ generated during the reaction. Ca(OH)₂ is prone to water loss and shrinkage during drying. Reducing its content can effectively reduce the material's shrinkage tendency, thereby improving the material's structural stability. Finally, regarding the micro-expansion effect, f-CaO and f-MgO in SG accelerate the hydration process in a highly alkaline environment, generating Ca(OH)₂ and Mg(OH)₂. The expansion effect generated during the reaction can be fully absorbed by the microporous structure of the system and cleverly transformed into micro-expansion, effectively compensating for the shrinkage generated during sample drying.

[0118] Example 10

[0119] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.8 parts MK, 79.2 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 1 part PEG.

[0120] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0121] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0122] (2) Add 19.8 parts of MK and 79.2 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary mortar mixer of model NJ-160B to mix at a rate of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0123] (3) Add 1 part of PEG to the 52.28 parts of alkaline activator prepared in step (1), stir thoroughly to obtain a mixture;

[0124] (4) Inject the mixed liquid prepared in step (3) into the mixed powder of step (2), and stir at a speed of 140 r / min for 1 min using a planetary paste mixer of model NJ-160B to wet and disperse the MK and BFS particles, and ensure that there is sufficient contact between the mixed liquid and the particles. Low-speed stirring can prevent the splashing of activator and water, and can also reduce internal bubbles and avoid local agglomeration. After stirring is completed, stop stirring for 1 min. During this period, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and alkaline activator are mixed evenly. To avoid local material residue, a planetary paste mixer was then started and rapidly stirred at 285 r / min for 2 min. This accelerated the collision and cross-linking of gel particles, further ensuring uniform mixing of the materials, promoting the initial formation of a three-dimensional network structure, and shortening the total stirring time. During this process, the system simultaneously undergoes "dissolution-polymerization" and geopolymerization reactions to generate NASH and C-(A)-SH gels. PEG molecular chains are bonded to the gel through hydrogen bonds or physical entanglement, giving the gel flexibility and forming an "elastic buffer layer" that absorbs shrinkage stress to inhibit the initiation and propagation of microcracks.

[0125] (5) Add 13.68 parts of water to the gel obtained in step (4), stir quickly for 3 minutes, and the alkali-activated MK-BFS inorganic adhesive modified with PEG is obtained. By adding an appropriate amount of water, the fluidity of the inorganic adhesive is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic adhesive, the PEG molecular chain can play a skeleton support role and better prevent the pore wall from shrinking due to capillary negative pressure. In addition, the incorporation of PEG will slightly reduce the elastic modulus of the material, but can significantly improve the strain capacity and alleviate the shrinkage cracking caused by rigid constraints.

[0126] Example 11

[0127] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.4 parts MK, 77.6 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 3 parts PEG.

[0128] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 10.

[0129] Example 12

[0130] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 19.0 parts MK, 76.0 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, and 5 parts PEG.

[0131] The preparation method of the alkali-activated inorganic adhesive with low drying shrinkage is the same as in Example 10.

[0132] like Figure 10As shown, the incorporation of PEG can effectively alleviate the drying shrinkage of the sample, and the drying shrinkage of the sample shows a trend of first decreasing and then increasing with the increase of PEG content. When the PEG content is 2.0%, the drying shrinkage value of the sample reaches the lowest value, and its 28-day drying shrinkage value is only 72.43% of that of the blank sample during the same period. The drying shrinkage of the alkaline-activated BFS sample is related to the PEG content and molecular weight. Appropriate PEG incorporation can obtain a good shrinkage reduction effect, but excessive PEG incorporation will reduce its shrinkage reduction effect. This is because PEG, as a surfactant, can significantly reduce the surface tension of the solution and effectively regulate the internal pore structure. The reduction of surface tension during the sample drying process helps to reduce the capillary stress caused by water evaporation, thereby reducing drying shrinkage. At the same time, PEG molecules can fill the internal pores. When the sample dries, the PEG molecules filled in the pores can play a skeletal support role, effectively preventing the pore walls from shrinking due to capillary negative pressure. However, excessive PEG content leads to uneven pore structure and increased porosity within the sample. While early shrinkage is minimal due to its moisturizing effect, as the curing period lengthens and moisture evaporates, the increased porosity exacerbates shrinkage deformation during drying. Furthermore, excessive PEG forms an isolation layer between MK, BFS, and the alkali activator, weakening their interfacial bonding and making the sample more prone to microcracks and defects during shrinkage, thus increasing shrinkage deformation. Comparatively, the shrinkage reduction effect of PEG is more pronounced in the early curing stages. After 8 hours of curing, the drying shrinkage of the 2.0% PEG sample was 58.45% of the blank sample. This may be because PEG significantly affects the reaction rate in the early curing stages. PEG adsorbs on the surface of MK and BFS particles, slowing down the contact between the active ingredients and the activator, hindering effective collisions between reactants, and reducing the formation of the larger shrinkage C-(A)-SH gel product.

[0133] like Figure 11As shown, after 8 hours of curing, the blank sample showed the most significant mass loss, reaching 9.223 g / kg, while the sample with 2.0% PEG content only lost 3.598 g / kg. The incorporation of PEG effectively reduced early mass loss, mainly because the chain-like molecular structure of PEG effectively fills the interparticle gaps, reducing water loss caused by excessive porosity. Simultaneously, the water-retaining effect of PEG also reduces water loss to some extent. With prolonged curing time, the mass loss of the samples gradually increased. After 7 days of curing, the mass loss of the PEG-incorporated samples increased significantly. Compared to the 3-day samples, the mass losses of samples with 1.0%, 2.0%, and 3.0% PEG content increased by 67.75%, 91.15%, and 108.61%, respectively. At this point, the mass loss of the PEG-incorporated samples was greater than that of the blank sample. This is mainly because PEG molecules are encapsulated within the C-(A)-SH gel, weakening its water-retaining capacity and thus accelerating water loss, leading to increased sample mass loss. The figure also shows that after 7 days, the mass loss of the samples increased with increasing PEG content. Compared with the 1% PEG-doped sample, the 56-day mass loss of samples with 2.0% and 3.0% PEG doping was increased by 28.62% and 54.55%, respectively. This is mainly because high PEG doping interferes with the normal crystallization process of the reaction products, making their structure more porous. Simultaneously, PEG adsorbs onto the surface of the reaction products, hindering the tight bonding between products and weakening the overall system integrity. Furthermore, excessive PEG doping increases the internal pore size and connectivity of the matrix, providing more favorable channels for moisture loss and leading to increased sample mass loss.

[0134] Depend on Figure 12It can be seen that the incorporation of PEG can effectively improve the early compressive strength of the samples. The compressive strength of samples with different PEG dosages at 1d and 3d is higher than that of the control sample at the same time. The 3d compressive strength of the sample with 1.0% PEG dosage is 35.51% higher than that of the control sample. This is because the PEG molecule contains -OH, which interacts with the active groups on the surface of MK or BFS, which can accelerate the formation of gel products, which is beneficial to refine the pores and reduce the interconnected pores, thus optimizing the pore size distribution. In addition, an appropriate amount of PEG molecules in the system can fill the pores and compact the structure. However, with the increase of PEG dosage, the compressive strength of samples at different ages all show a downward trend, and the compressive strength of samples with 2.0% and 3.0% PEG dosages at 7d and 28d is lower than that of the control sample at the same time. The 28-day compressive strength of samples with 2.0% and 3.0% PEG dosages is 9.21% and 15.62% lower than that of the control sample at the same time, respectively. This is mainly because excessive PEG incorporation can form aggregates within the material, creating larger pores. These aggregates and the weak areas around the pores are prone to stress concentration, reducing the compressive strength. At the same time, too much PEG can coat the particle surface, hindering the effective bonding of gel products between particles, which is detrimental to the reaction, reduces the amount of gel products generated, and affects the continuity and integrity of the gel network, thus leading to a decrease in the compressive strength of the sample.

[0135] In Examples 10-12, PEG mainly works through multiple pathways such as reducing the surface tension of the pore solution, physically filling and refining the pore structure, adsorbing and slowly releasing water, and forming an "elastic buffer layer" to achieve multi-faceted crack resistance and shrinkage reduction effects from physical inhibition, structural optimization to chemical compensation. First, as a surfactant, PEG significantly reduces the surface tension of the pore solution and decreases capillary pressure, thereby alleviating shrinkage stress caused by water evaporation or self-drying. It is particularly effective in suppressing shrinkage deformation caused by negative capillary pressure in dry environments. Second, PEG refines the pore structure through physical filling and interaction with reaction products (such as NASH gel), reducing the proportion of macropores and decreasing pore connectivity, forming a more uniform micropore distribution to disperse shrinkage stress, slowing down water migration rates, and reducing shrinkage caused by rapid water loss. Third, PEG's hydrophilic properties adsorb and slowly release water, maintaining internal humidity and delaying self-shrinkage. Simultaneously, it promotes the continued reaction in the later stages of BFS to generate a dense gel structure, compensating for chemical shrinkage. Furthermore, PEG molecular chains bind to NASH gel through hydrogen bonds or physical entanglement, endowing the gel with flexibility and forming an "elastic buffer layer" that absorbs shrinkage stress to inhibit the initiation and propagation of microcracks. Finally, the incorporation of PEG slightly reduces the material's elastic modulus but significantly improves strain capacity, alleviating shrinkage cracking caused by rigid constraints.

[0136] Example 13

[0137] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 18.6 parts MK, 74.4 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, 2 parts PEG and 5 parts CW.

[0138] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0139] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0140] (2) Add 18.6 parts of MK and 74.4 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary mortar mixer of model NJ-160B to mix at a rate of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0141] (3) Add 2 parts of PEG to the 52.28 parts of alkaline activator prepared in step (1), stir thoroughly to obtain a mixture;

[0142] (4) Add 5 parts of CW to the mixed powder obtained in step (2) above, and use a planetary paste mixer of model NJ-160B to stir again at a rate of 140r / min for 3min to fully mix it with the mixed powder to obtain a mixture; this process utilizes mechanical stirring to effectively achieve physical filling of CW, reduce porosity, and improve matrix density.

[0143] (5) Inject the mixture prepared in step (3) into the mixture obtained in step (4), and stir it for 1 minute at a rate of 140 r / min using a planetary paste mixer of model NJ-160B. This allows the mixture to be slowly and evenly dispersed on the surface of the material particles, fully contacting the reaction sites, reducing bubbles and controlling the reaction rate, avoiding local agglomeration of the mixture, and also preventing splashing of the activator. After stirring, stop stirring for 1 minute. During this time, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and the alkaline activator are mixed evenly and to avoid local material residue. Then, start the NJ-160B planetary paste mixer. A planetary paste mixer of type 60B was used to rapidly stir the paste at a rate of 285 r / min for 2 min to break up agglomerates and promote ion dissolution and gel formation. During this process, the system simultaneously undergoes "dissolution-polymerization" and geopolymerization reactions to generate NASH and C-(A)-SH gels. PEG molecular chains are combined with the gel through hydrogen bonds or physical entanglement, giving the gel flexibility and forming an "elastic buffer layer" to absorb shrinkage stress and inhibit the initiation and propagation of microcracks. CW, through the crack deflection mechanism, hinders the development of cracks in the matrix and guides cracks to propagate along the direction of whiskers when dispersing the shrinkage stress generated by the gel, consuming a large amount of shrinkage stress and improving the toughness of the material.

[0144] (6) Add 13.68 parts of water to the gel obtained in step (5), stir rapidly for 3 minutes, and the alkali-activated MK-BFS inorganic adhesive modified with PEG and CW is obtained. By adding an appropriate amount of water, the fluidity of the inorganic adhesive is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic adhesive, the PEG molecular chain can play a skeleton support role, which can better prevent the pore wall from shrinking due to capillary negative pressure. At the same time, the incorporation of PEG will slightly reduce the elastic modulus of the material, but can improve the strain capacity and alleviate the shrinkage cracking caused by rigid constraints. In addition, CW will be gradually pulled out or broken. This process requires a lot of energy, which is beneficial to suppress the shrinkage of the matrix. After the CW breaks, the remaining part can still play a physical filling and stress dispersion role, limiting the further propagation of cracks and effectively alleviating shrinkage deformation.

[0145] This embodiment fully utilizes the shrinkage reduction effects of PEG, such as reducing the surface tension of the pore solution, refining the pore structure, adsorbing and slowly releasing water, forming an "elastic buffer layer", and CW physical filling, whisker bridging, crack deflection, whisker pull-out and fracture. Through the reasonable compounding of the two, the synergistic shrinkage reduction of MK-BFS inorganic adhesive is effectively achieved.

[0146] Example 14

[0147] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 14.6 parts MK, 58.4 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, 2 parts PEG and 25 parts SG.

[0148] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0149] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0150] (2) Add 14.6 parts of MK and 58.4 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary mortar mixer of model NJ-160B to mix at a rate of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0151] (3) Add 2 parts of PEG to the 52.28 parts of alkaline activator prepared in step (1), stir thoroughly to obtain a mixture;

[0152] (4) Add 25 parts of SG to the mixed powder in (2) above, and stir again at a speed of 140 r / min for 3 min using a planetary paste mixer of model NJ-160B to fully mix SG with the mixed powder to obtain a mixture. This process utilizes mechanical stirring to effectively fill the gaps between MK and BFS particles, achieving physical filling, improving the density of the mixture, and providing a more stable matrix structure for subsequent reactions.

[0153] (5) Inject the mixture obtained in step (3) into the mixture obtained in step (4), and stir it for 1 minute at a rate of 140 r / min using a planetary paste mixer of model NJ-160B. This allows the mixture to be slowly and evenly dispersed on the surface of the material particles, fully contacting the reaction sites, reducing bubbles and controlling the reaction rate, avoiding local agglomeration of the mixture, and also preventing splashing of the activator. After stirring, stop stirring for 1 minute. During this time, use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot to further ensure that the material and the alkaline activator are mixed evenly and to avoid local material residue. Then, start the NJ-160B planetary paste mixer. A planetary paste mixer of type -160B is used to rapidly stir the paste at 285 rpm for 2 minutes to break up agglomerates and promote ion dissolution and gel formation. During this process, the system undergoes both dissolution-polymerization and geopolymerization reactions to generate NASH and CSH gels. PEG molecular chains are bonded to the gel through hydrogen bonds or physical entanglement, giving the gel flexibility and forming an "elastic buffer layer" that absorbs shrinkage stress to inhibit the initiation and propagation of microcracks. The rough microstructure of the SG surface provides more nucleation sites for the gel reaction, promotes heterogeneous nucleation of the gel, accelerates the formation and solidification of the gel network, and indirectly improves early strength and structural stability.

[0154] (6) Add 13.68 parts of water to the gel obtained in step (5), stir quickly for 3 minutes, and the alkali-activated MK-BFS inorganic adhesive modified with PEG and SG is obtained. By adding an appropriate amount of water, the fluidity of the inorganic adhesive is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic adhesive, the PEG molecular chain can play a skeleton support role and better prevent the pore walls from shrinking due to capillary negative pressure. At the same time, the incorporation of PEG will slightly reduce the elastic modulus of the material, but can improve the strain capacity and alleviate the shrinkage cracking caused by rigid constraints. The high fineness (large specific surface area) and gradation characteristics of SG particles enable them to fill the pores between particles, form a denser particle packing structure, improve the contact between matrix particles, and provide a more uniform internal environment for the gel reaction.

[0155] This embodiment fully utilizes the shrinkage reduction effects of PEG, such as reducing the surface tension of the pore solution, refining the pore structure, adsorbing and slowly releasing water, forming an "elastic buffer layer", and SG physical filling, volcanic ash reaction, and micro-expansion effect. Through the reasonable compounding of the two, the synergistic shrinkage reduction of inorganic adhesives is effectively achieved.

[0156] Example 15

[0157] An alkali-activated inorganic adhesive with low drying shrinkage has the following components in parts by weight: 18.4 parts MK, 73.6 parts BFS, 43.85 parts water glass, 8.43 parts sodium hydroxide, 13.68 parts water, 3 parts CB and 5 parts CW.

[0158] The preparation method of the above-mentioned alkali-activated inorganic adhesive with low drying shrinkage rate includes the following steps:

[0159] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3 NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and left to stand for 1 day before use to obtain an alkaline activator.

[0160] (2) Add 18.4 parts of MK and 73.6 parts of BFS to the cement paste mixing pot, raise it to the fixed position, and use a planetary mortar mixer of model NJ-160B to mix at a speed of 140r / min for 3 minutes to make MK and BFS fully mixed. Controlling the low speed of mixing can avoid material splashing while ensuring that the two materials are mixed evenly to obtain mixed powder.

[0161] (3) Add 3 parts CB and 13.68 parts water to a beaker and ultrasonically disperse for 20 minutes using an ultrasonic disperser (model KH2200B) to obtain a uniform CB suspension. Ultrasonic treatment can quickly and uniformly disperse CB particles, effectively prevent particle agglomeration, and improve the dispersibility and stability of CB; 20 minutes of ultrasonic treatment is too short and the dispersion is insufficient, while too long a time can easily cause secondary agglomeration. The addition of an appropriate amount of water is beneficial to the uniform dispersion of powdered CB and can also reasonably adjust the flowability of inorganic adhesive to ensure its bonding effect;

[0162] (4) Add 5 parts of CW to the mixed powder obtained in step (2) above, and use a planetary paste mixer of model NJ-160B to stir again at a rate of 140r / min for 3min to fully mix it with the mixed powder to obtain a mixture; this process utilizes mechanical stirring to effectively achieve physical filling of CW, reduce porosity, and improve matrix density.

[0163] (5) Inject the CB suspension prepared in step (3) into the mixed powder obtained in step (4), and stir at a rate of 140 r / min for 3 min using a cement paste mixer of model NJ-160B. After the materials are uniformly mixed, a mixture is obtained. In this process, mechanical stirring ensures that the prepared CB suspension and the mixture are in full contact. Based on the micro-size effect, CB fills and embeds itself in the micropores better, improving the density of the matrix.

[0164] (6) Inject the alkaline activator prepared in step (1) into the mixture obtained in step (5), and stir at a rate of 140 r / min for 1 min using a planetary paste mixer of model NJ-160B, so that the alkaline activator can be slowly and evenly dispersed on the surface of the material particles, fully contact the reaction sites, reduce bubbles and control the reaction rate, avoid local agglomeration of the mixture, and also prevent the activator from splashing out; after stirring is completed, stop stirring for 1 min, during which time use a rubber scraper to scrape the mortar on the blades and the pot wall into the middle of the pot, further ensuring that the material and alkaline activator are mixed evenly and avoiding local material residue; then, start the planetary paste mixer of model NJ-160B at a rate of 285 r / min for 2 min to break the agglomerates and promote ion dissolution and gel formation; in this process, the system simultaneously undergoes "dissolution-polymerization" and ground The polymerization reaction generates NASH and C-(A)-SH gels. CB sheets disperse in the matrix, forming a "maze effect" that hinders the migration channels of water and ions, reduces permeability, and refines the pore structure. Simultaneously, CB particles can adsorb onto the surface of unreacted MK and BFS particles, reducing interfacial porosity between the cementitious phase and aggregate, and lowering the weakness of the interfacial transition zone. Its sheet structure can induce crack deflection, thus inhibiting cracking. In the matrix, CW, through the crack deflection mechanism, hinders crack development and guides crack propagation along the direction of whiskers when generating gel shrinkage stress, consuming a large amount of shrinkage stress and improving material toughness. Furthermore, the gradual pull-out or fracture of CW requires a large amount of energy, which helps to inhibit material shrinkage. After CW fractures, the remaining portion can still play a role in physical filling and stress dispersion, limiting further crack propagation and effectively alleviating shrinkage deformation.

[0165] This embodiment makes full use of the shrinkage reduction effects of physical filling, chemical activation, interface optimization, adsorption regulation of CB and the bridging, crack deflection and whisker pull-out and fracture of CW, and achieves better synergistic shrinkage reduction of inorganic adhesive through reasonable compounding of the two.

[0166] Comparative Example 1

[0167] An alkali-activated MK-BFS inorganic adhesive, with the following component amounts by weight:

[0168] 20 parts MK, 80 parts BFS, 43.85 parts water glass, 8.43 parts NaOH and 13.68 parts water.

[0169] The preparation method of the above-mentioned alkali-activated MK-BFS inorganic adhesive includes the following steps:

[0170] (1) Preparation of alkaline activator: A substance with a density of 2.13 g / cm³ was prepared. 3NaOH was slowly injected into the water glass solution, and the solution was continuously stirred with a glass rod to obtain a compound solution with a water glass modulus (SiO2 / Na2O) of 1.2 and a Na2O content of 10%. The prepared compound solution was placed in a beaker, cooled to room temperature, and allowed to stand for 1 day before use to obtain an alkaline activator.

[0171] (2) Add 20 parts MK and 80 parts BFS to the cement paste mixing pot, raise it to the fixed position, and use a cement paste mixer of model NJ-160B to mix at a speed of 140r / min for 3 minutes to ensure that MK and BFS are fully mixed. Low-speed mixing can avoid material splashing and can also ensure that the two materials are mixed evenly to obtain a mixed powder.

[0172] (3) Add 52.28 parts of alkaline activator and 13.68 parts of water prepared in step (1) to 100 parts of mixed powder obtained in step (2). Use a cement paste mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min to initially wet and disperse the MK and BFS particles, ensuring sufficient contact between the mixture and the particles. Low-speed stirring can prevent the activator and water from splashing out, and can also reduce internal air bubbles and avoid local agglomeration. Then, start the cement paste mixer to stir quickly at a rate of 285 r / min for 2 min to thoroughly disperse the particles, further make the material uniformly mixed, accelerate the system reaction and improve fluidity, and shorten the total stirring time to obtain alkali-activated MK-BFS inorganic adhesive.

[0173] The alkali-activated MK-BFS inorganic adhesives prepared in Examples 1-15 and Comparative Example 1 were subjected to drying shrinkage and compressive strength tests, respectively. The test results are shown in Table 1 below. As can be seen from the table, Examples 1-15 of this invention, by incorporating CW, CB, SG, and PEG-modified materials, effectively reduced the drying shrinkage value and improved the compressive strength of the alkali-activated MK-BFS inorganic adhesive through physical filling, whisker bridging, chemical activation and interface optimization, pozzolanic reaction, micro-expansion effect, reduction of pore solution surface tension, and formation of an "elastic buffer layer." Example 13 showed the best improvement effect on the drying shrinkage of the alkali-activated MK-BFS inorganic adhesive.

[0174] Table 1. Comparison of test results of alkali-activated MK-BFS inorganic adhesives prepared in Examples 1-15 and Comparative Example 1

[0175]

[0176] As can be seen from the comparison between Examples 1-12 and Examples 13-15, compared with the addition of the modified material alone, the mixing of different modified materials within a reasonable range has a more significant effect on reducing the drying shrinkage and improving the compressive strength of alkali-activated MK-BFS inorganic adhesive. This is mainly due to the synergistic and complementary effects and multi-scale effects of different modified materials. Reasonable mixing can better optimize the pore structure, improve the density of the matrix, effectively transfer and disperse shrinkage stress, and reduce the risk of cracking. At the same time, the reasonable mixing of different modified materials can also give full play to the multiple action mechanisms of the materials, so as to reduce the drying shrinkage while improving the compressive strength.

[0177] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This method of description is merely for clarity, and those skilled in the art should consider the specification as a whole. The technical solutions in the various embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An alkali-activated inorganic adhesive with low drying shrinkage, characterized in that, It includes a solid component and a liquid component, wherein the solid component includes 15-20 parts MK, 60-80 parts BFS and a modified material; The liquid component comprises 41.82-62.74 parts of alkaline activator and 9.68-13.68 parts of water; the mass ratio of the solid component to the liquid component is 1.42-1.62:

1. The MK is metakaolin, and the BFS is blast furnace slag; The alkaline activator is a compound solution obtained by mixing NaOH and water glass solution; the mass ratio of NaOH to water glass solution is 0.16~0.25:1; The modified material is selected from one of polyethylene glycol + calcium carbonate whiskers, polyethylene glycol + steel slag, and calcium carbonate whiskers + bentonite. The calcium carbonate whiskers constitute 1.0~5.0% of the solid composition by mass. The bentonite accounts for 3.0% to 9.0% of the total mass of the solid components. The steel slag accounts for 5.0% to 25.0% of the total solid content by mass. The polyethylene glycol accounts for 1.0 to 3.0% of the mass of the solid component.

2. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The liquid component comprises 52.28 parts of alkaline activator and 13.68 parts of water; in the alkaline activator, the mass ratio of NaOH to water glass solution is 8.43:43.

85.

3. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The MK particles have a particle size range of 0.36~66.9μm and a specific surface area of ​​188.4~220.6m². 2 / kg; the particle size range of the BFS is 0.31~76.0μm, and the specific surface area is 208.5~225.9m². 2 / kg.

4. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The alkaline activator has a water glass modulus of 1.0 to 1.4 and a Na2O content of 8.0 to 12.0%.

5. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The calcium carbonate whiskers have a size of 0.31~45.6 μm and a specific surface area of ​​956.3~986.8 m². 2 / kg and pH value is 8.0~10.

0.

6. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The specific surface area of ​​the bentonite is 395.2~440.6 m². 2 / kg, the SiO2 and Al2O3 content in bentonite is 83.59%~89.45%, and the CaO content is 1.19%~1.35%.

7. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The steel slag has a fineness of 600-800 mesh and a specific surface area of ​​430.2-482.8 m². 2 / kg.

8. The alkali-activated inorganic adhesive with low drying shrinkage according to claim 1, characterized in that, The polyethylene glycol is a linear polymer with an average molecular weight of 1900-2200 Da and a solid density of 1.15-1.26 g / cm³. 3 And the thickness is 100~200nm.

9. The method for preparing an alkali-activated inorganic adhesive with low drying shrinkage according to any one of claims 1 to 8, characterized in that, Here are the steps: S1: NaOH is injected into the water glass solution, and after stirring, a compound solution with a water glass modulus of 1.0~1.4 and a Na2O content of 8.0~12.0% is obtained. After standing for 1 day, an alkaline activator is obtained. S2: Add 15-20 parts of MK and 60-80 parts of BFS to a cement paste mixing pot, dry mix for 3 minutes to obtain a mixed powder; S3: Add the modified material to the mixed powder obtained in S2 according to the ratio, and stir to obtain the mixture. S4: Add 41.82~62.74 parts of alkaline activator prepared in S1 and 9.68~13.68 parts of water to 100 parts of the mixture obtained in S3. After slow stirring and fast stirring, an alkaline activated inorganic adhesive with low drying shrinkage is obtained.

10. The application of the alkali-activated inorganic adhesive with low drying shrinkage as described in any one of claims 1 to 8 in reinforced concrete.

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