Alkali-activated inorganic adhesive with low drying shrinkage rate as well as preparation method and application of alkali-activated inorganic adhesive

Abstract

The invention discloses an alkali-activated inorganic adhesive with low drying shrinkage rate and a preparation method and application thereof, and belongs to the technical field of inorganic adhesive modification, the alkali-activated inorganic adhesive comprises a solid component and a liquid component, the solid component comprises 15-20 parts by weight of MK, 60-80 parts by weight of BFS and 1-25 parts by weight of a modified material; the liquid component comprises the following components in parts by weight: 41.82 to 62.74 parts of an alkaline exciting agent and 9.68 to 13.68 parts of water; the alkaline exciting agent is a compound solution obtained by mixing NaOH and a water glass solution; the modified material is selected from one or more of calcium carbonate whiskers, bentonite, steel slag and polyethylene glycol. Through multi-path synergistic effects of physical filling, whisker bridging, chemical activation and interface optimization, a micro-expansion effect, reduction of surface tension of a pore solution, formation of an elastic buffer layer and the like of the shrinkage modified material, the inorganic adhesive microstructure is deeply optimized, internal pores and defects are greatly reduced, and the shrinkage resistance of the inorganic adhesive is remarkably enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic glue modification, and in particular relates to an alkali-activated inorganic glue with low drying shrinkage, and a preparation method and application thereof. Background Art

[0002] With the acceleration of urbanization and the increasing service life of buildings, the demand for structural reinforcement is increasing. Among various reinforcement technologies, fiber-reinforced plastic (FRP) reinforcement technology stands out due to its advantages such as light weight, high strength, corrosion resistance, and convenient construction. As the key link that enables FRP to work effectively with existing structures, the importance of binders is becoming increasingly prominent. Alkali-activated inorganic adhesives, with their multiple advantages such as high-temperature resistance, low carbon footprint, environmental friendliness, and fire retardancy, are becoming an ideal alternative to traditional epoxy resin-based organic adhesives. They demonstrate great potential for application in high-temperature service environments such as tunnels and bridges. The performance, mechanical properties, and drying shrinkage of alkali-activated inorganic adhesives are largely dependent on the precursors used. Blast furnace slag (BFS) and metakaolin (MK) are two commonly used precursors. Previous studies have shown that alkali-activated inorganic adhesives prepared from these two materials alone do not perform well, but the two precursors may offer complementary engineering properties. To this end, some scholars have mixed the two to prepare alkali-activated MK-BFS inorganic glue and found that after reasonable mixing, BFS quickly dissolves and reacts with OH in the system. - 、SiO3 2- A reaction occurs to generate NASH and C-(A)-SH gel, which accelerates the polymerization rate of the composite system, rationally optimizes the internal microstructure, and effectively improves the engineering performance.

[0003] However, alkali-activated MK-BFS inorganic adhesives still face many challenges brought by composite systems in actual engineering applications. The incorporation of active BFS, multiple components, and variability in the activator / water content make its performance control more difficult, especially in terms of drying shrinkage performance, where it is clearly deficient. Its large drying shrinkage can easily trigger internal stress concentration, leading to microcracks on the surface of the hardened body, thereby weakening the overall performance of the inorganic adhesive. At the same time, the cracking problem will further affect its bonding properties and toughness, making it difficult to firmly bond to the substrate and prone to peeling when subjected to deformation loads, 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 their drying shrinkage behavior and mass loss patterns, and revealing their microstructural characteristics and shrinkage reduction mechanisms have become urgent issues that need to be addressed. Summary of the Invention

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

[0005] To solve the above technical problems, the inventors obtained the technical solution of the present invention through practice and summary. The present invention discloses an alkali-activated inorganic glue with low drying shrinkage rate, which includes a solid component and a liquid component. By weight, the solid component includes 15-20 parts of MK, 60-80 parts of BFS and 1-25 parts of a modification material; the liquid component includes 41.82-62.74 parts of an 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;

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

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

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

[0009] Further, the particle size range of the MK is 0.36-66.9 μm, and the specific surface area is 188.4-220.6 m 2 / kg; the particle size range of the BFS is 0.31-76.0 μm, and the specific surface area is 208.5-225.9 m 2 / kg.

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

[0011] Further, the size of the calcium carbonate whiskers is 0.31-45.6 μm, the specific surface area is 956.3-986.8 m 2 / kg and the pH value is 8.0-10.0.

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

[0013] Further, the fineness of the steel slag is 600 - 800 mesh, and the specific surface area is 430.2 - 482.8 m 2 / kg.

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

[0015] Further, the mass proportion of the calcium carbonate whiskers in the solid components is 1.0 - 5.0%.

[0016] Further, the mass proportion of the bentonite in the solid components is 3.0 - 9.0%.

[0017] Further, the mass proportion of the steel slag in the solid components is 5.0 - 25.0%.

[0018] Further, the mass proportion of the polyethylene glycol in the solid components is 1.0 - 3.0%.

[0019] Further, for the preparation method of the alkali-activated inorganic glue with low drying shrinkage rate described above, the steps are as follows:

[0020] S1: Inject NaOH into the water glass solution, and after stirring, obtain a compound solution with a water glass modulus of 1.0 - 1.4 and a Na2O content of 8.0 - 12.0%. After standing for 1 d, obtain an alkaline activator;

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

[0022] S3: Add the modified materials to the mixed powder obtained in S2 according to the ratio, and after stirring, obtain a mixed material;

[0023] S4: Inject 41.82 - 62.74 parts of the alkaline activator prepared in S1 and 9.68 - 13.68 parts of water into 100 parts of the mixed material obtained in S3. After slow stirring and fast stirring, the alkali-activated inorganic glue with low drying shrinkage rate is obtained.

[0024] Further, the application of the alkali-activated inorganic glue with low drying shrinkage rate described above in strengthening concrete.

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

[0026] (1) The present invention modifies the shrinkage material by using calcium carbonate whiskers (CW), bentonite (CB), steel slag (SG), and polyethylene glycol (PEG). From aspects such as physical filling, whisker bridging, adsorption and microstructure regulation, micro-expansion effect, reducing the surface tension of pore solution, and forming an "elastic buffer layer", the shrinkage of alkali-activated inorganic glue is modified, significantly improving the anti-shrinkage performance of the inorganic glue and reducing its cracking risk.

[0027] (2) The incorporation of CW in the present invention can preferably reduce the gel pores and mesopore porosity, and inhibit the drying shrinkage of alkali-activated MK-BFS inorganic glue. Moreover, as the CW content increases, the drying shrinkage of the specimen decreases. The drying shrinkage value of the specimen with a CW content of 5.0% at 28 days is 87.55% of the drying shrinkage value of the blank specimen in the same period; CW realizes shrinkage reduction and strengthening in multiple aspects from pore filling, structure strengthening to stress dispersion through the synergistic action of multiple pathways such as physical filling, whisker bridging, crack deflection, whisker pull-out and fracture.

[0028] (3) The incorporation of CB in the present invention can effectively inhibit the drying shrinkage of alkali-activated MK-BFS inorganic glue. Moreover, as the CB content increases, the drying shrinkage of the specimen first decreases and then increases. The drying shrinkage of the specimen with a CB content of 3.0% at 56 days is reduced by 9.66%, 7.64%, and 9.86% compared with the blank specimen and the specimens with CB contents of 6.0% and 9.0% respectively; The tiny particle size CB particles realize shrinkage reduction and strengthening in aspects such as microstructure densification, strengthening gel products, adsorption and microstructure regulation through the synergistic action of multiple pathways such as physical filling, water absorption and expansion, chemical activation and interface optimization, and forming a "labyrinth effect".

[0029] (4) The incorporation of an appropriate amount of SG in the present invention reduces the proportion of the pore volume fraction of mesopores in alkali-activated MK-BFS inorganic glue, effectively inhibiting the drying shrinkage of the specimen. The dry shrinkage value of the specimen with an SG content of 25.0% at 56 days is reduced by 9.2% and 5.2% compared with the blank specimen and the specimen with an SG content of 5.0% respectively; SG deeply optimizes the microstructure of the inorganic glue through the triple synergistic action of its physical filling, pozzolanic reaction, and micro-expansion effect, greatly reducing its internal pores and defects, and significantly enhancing the anti-shrinkage performance and anti-chemical erosion ability of the material.

[0030] (5) The incorporation of PEG in the present invention can preferably inhibit the drying shrinkage of alkali-activated MK-BFS inorganic glue. Moreover, as the PEG content increases, the drying shrinkage of the specimen shows a trend of first decreasing and then increasing. When the content is 2.0%, the drying shrinkage value of the specimen reaches the lowest, and its drying shrinkage value at 28 days is only 72.4% of that of the blank specimen in the same period; PEG realizes anti-cracking and shrinkage reduction in multiple ways from physical inhibition, structure optimization to chemical compensation through the synergistic action of multiple pathways such as reducing the surface tension of pore solution, physically filling and refining pore structure, adsorbing and releasing moisture slowly, and forming an "elastic buffer layer".

[0031] (6) By mixing one or several of the above-mentioned modification materials, the present invention can effectively inhibit the drying shrinkage of the alkali-activated MK-BFS inorganic glue, give full play to the synergistic complementary effect and multi-scale effect of different modification materials, optimize the pore structure, improve the matrix compactness, effectively transfer and disperse the shrinkage stress, and reduce the cracking risk. At the same time, the reasonable mixing of different modification materials can also give full play to the multiple action mechanisms of the materials, realizing the improvement of the compressive strength while reducing the drying shrinkage. Description of the Drawings

[0032] Figure 1 It is a diagram showing the influence of different CW dosages of the present invention on the drying shrinkage of the alkali-activated MK-BFS inorganic glue;

[0033] Figure 2 It is a diagram showing the influence of different CW dosages of the present invention on the mass loss of the alkali-activated MK-BFS inorganic glue;

[0034] Figure 3 It is a diagram showing the influence of different CW dosages of the present invention on the compressive strength of the alkali-activated MK-BFS inorganic glue;

[0035] Figure 4 It is a diagram showing the influence of different CB dosages of the present invention on the drying shrinkage of the alkali-activated MK-BFS inorganic glue;

[0036] Figure 5 It is a diagram showing the influence of different CB dosages of the present invention on the mass loss of the alkali-activated MK-BFS inorganic glue;

[0037] Figure 6 It is a diagram showing the influence of different CB dosages of the present invention on the compressive strength of the alkali-activated MK-BFS inorganic glue;

[0038] Figure 7 It is a diagram showing the influence of different SG dosages of the present invention on the drying shrinkage of the alkali-activated MK-BFS inorganic glue;

[0039] Figure 8 It is a diagram showing the influence of different SG dosages of the present invention on the mass loss of the alkali-activated MK-BFS inorganic glue;

[0040] Figure 9 It is a diagram showing the influence of different SG dosages of the present invention on the compressive strength of the alkali-activated MK-BFS inorganic glue;

[0041] Figure 10 It is a diagram showing the influence of the PEG dosage of the present invention on the drying shrinkage of the alkali-activated MK-BFS inorganic glue;

[0042] Figure 11 It is a diagram showing the influence of the PEG dosage of the present invention on the mass loss of the alkali-activated MK-BFS inorganic glue;

[0043] Figure 12This is the graph showing the effect of PEG content on the compressive strength of alkali-activated MK-BFS inorganic glue in the present invention; Specific embodiments

[0044] To make the above objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with specific embodiments.

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

[0046] Among them, the metakaolin (MK / K-1100W) used comes from Inner Mongolia Chaopai New Materials Co., Ltd.; its density is 2.626 g / cm 3 ; the activity index is 130%; the specific surface area is 188.4 - 220.6 m 2 / kg; the particle size is 0.36 - 66.9 μm.

[0047] The blast furnace slag (BFS) comes from Anhui Magang Jiahua New Building Materials Co., Ltd.; its density is 2.892 g / cm 3 ; the activity index is 72.6%; the specific surface area is 208.5 - 225.9 m 2 / kg; the particle size is 0.31 - 76.0 μm.

[0048] Alkali activator raw material (sodium silicate solution): It is a commercially available industrial-grade high-purity sodium silicate solution, with a modulus of 3.22, a Baume degree of 16.5, and a density of 1.38 g / cm 3 ; the component composition weight ratio is: Na2O is 8.50%, SiO2 is 26.80%, water-insoluble matter is 0.36%, and water is 64.34%. Commercially available NaOH (density 2.13 g / cm 3 ) is used to adjust the modulus of sodium silicate (SiO2 / Na2O) and the content of Na2O, and it is reserved after aging for 1 day.

[0049] Based on the mass conservation of SiO2 and Na2O in the solution, the mass of NaOH required to prepare sodium silicate 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 sodium silicate with different moduli, G1 is the mass of Na2O in the high-modulus sodium silicate, M0 and M x are the modulus of the high-modulus sodium silicate and the modulus of the prepared sodium silicate respectively, P and A are the purity of NaOH and the content of Na2O in the sodium silicate respectively. In the present invention, P = 96% and A = 8.5%.

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

[0053] Calcium carbonate whiskers (CW) are from Macklin Co., Ltd. The density, specific surface area, and pH value of the material are 2.86 g / cm³, 956.3 - 986.8 m 2 / kg, and 8.0 - 10.0 respectively; its shape is needle-like, and the size is 0.31 - 45.6 μm.

[0054] Bentonite (CB) is from Wuxi Dingsheng Technology Co., Ltd. The main shape is granular. The density, activity index, and specific surface area of the material are 2.668 g / cm 3 , 72.6%, 395.2 - 440.6 m 2 / kg. The content of SiO2 and Al2O3 in bentonite is 83.59% - 89.45%, and the content of CaO is 1.19% - 1.35%.

[0055] Steel slag (SG) is from MaSteel Co., Ltd. The fineness is 600 - 800 mesh. The density, activity index, and specific surface area of the material are 3.318 g / cm 3 , 65.6%, 430.2 - 482.8 m 2 / kg. Its mineral composition mainly includes C3S, C2S, Ca(OH)2, and a small amount of C2F. At the same time, it also contains components such as RO phase and f-CaO. The presence of C3S and C2S gives it potential cementitious activity. SG contains spherical microbeads with a size of about 1 - 15 mm.

[0056] Polyethylene glycol (PEG) is 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, and the solid density is 1.15 - 1.26 g / cm 3 , the melting point is 50 - 55 °C, and the freezing point is 45 - 50 °C. The SEM image shows that the surface of the PEG-2000 film presents a regular lamellar crystal structure with a thickness of 100 - 200 nm.

[0057] In the examples of the present invention, the alkali-activated MK-BFS inorganic glue is cured under standard conditions.

[0058] The performance test method of the alkali-activated MK-BFS inorganic glue after shrinkage modification in the present invention is as follows:

[0059] Drying shrinkage performance: Conducted in accordance with JGJ / T70 - 2009.

[0060] Compressive strength: Conducted in accordance with GB / T 17671-2021; the specimen size is 40mm×40mm×160mm. After the specimen is cured to the designed age, the flexural strength test is first carried out using an electric flexural testing machine (model: DKZ-6000), with a loading speed of 50N / s±10N / s. Subsequently, the compressive strength test is carried out using a cement compression testing machine (model: TYE-2000), with a loading speed of 0.5~1.0MPa / s.

[0061] In the following examples, the percentage of the modified materials (such as: calcium carbonate whiskers (CW), bentonite (CB), steel slag (SG), and polyethylene glycol (PEG)) represents the proportion of the added modified substances in the entire solid component (including MK, BFS, and the modified materials).

[0062] Example 1

[0063] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 19.8 parts of MK, 79.2 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 1 part of CW.

[0064] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is as follows:

[0065] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature, and let it stand for 1d before use to obtain the alkaline activator;

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

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

[0068] (4) Pour 52.28 parts of the alkaline activator prepared in step (1) into the 100 parts of the mixed materials obtained in step (3), and use a planetary mortar mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min 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, fully contacting the reaction sites. Low-speed stirring in the early stage can prevent the splashing of the activator and water, 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 the uniform mixing of the material and the alkaline activator and avoid local material residue. Subsequently, start the planetary mortar mixer of model NJ-160B and stir quickly at a rate of 285 r / min for 2 min to accelerate the mixing rate of the composite system, completely disperse the particles, promote the violent mixing and full reaction of the activator and the material, and improve the reaction efficiency. In this process, the "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system, generating N-A-S-H and C-(A)-S-H gels. Needle-shaped CW has the characteristics of high strength and high modulus. The network structure formed when filling pores has a bridging stress effect, effectively transmitting and dispersing the shrinkage stress, and reducing the deformation caused by the concentration of shrinkage stress in the system. At the same time, CW, relying on the crack deflection mechanism, hinders the development of cracks in the matrix and guides the cracks to expand along the whisker direction when dispersing the shrinkage stress of the generated gel, 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) and stir quickly for 3 min to obtain the alkali-activated MK-BFS inorganic glue modified by incorporating CW. By adding an appropriate amount of water, the fluidity of the inorganic glue is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic glue, CW will gradually be pulled out or broken, and this process consumes a large amount of energy, which is beneficial to inhibiting the shrinkage of the material. In addition, after CW breaks, the remaining part can still play a role in physical filling and stress dispersion, restricting the further expansion of cracks and effectively alleviating the shrinkage deformation.

[0070] Example 2

[0071] An alkali-activated inorganic glue with a low drying shrinkage rate, calculated by weight, the dosage of each component is as follows: 19.4 parts of MK, 77.6 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 3 parts of CW.

[0072] The preparation method of the above alkali-activated inorganic glue with a low drying shrinkage rate is the same as that of Example 1.

[0073] Example 3

[0074] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 19.0 parts of MK, 76.0 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 5 parts of CW.

[0075] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 1.

[0076] As Figure 1 shown, the incorporation of calcium carbonate whiskers (CW) can better inhibit the drying shrinkage of the specimen, and with the increase of the CW content, the drying shrinkage value of the specimen decreases. The drying shrinkage value of the specimen with 5.0% CW content at 28d is 87.55% of the drying shrinkage value of the blank specimen at the same age. This is mainly because the needle-shaped CW has a unique spatial structure, which can tightly fill its internal pores and form a network structure inside the system. When the material is subjected to internal shrinkage stress, CW can effectively disperse and transfer the stress, while reducing the capillary tension, playing the role of whisker bridging and stress relief, effectively delaying the formation and expansion of microcracks, thereby reducing the drying shrinkage of the specimen. In contrast, the shrinkage reduction effect of CW is more obvious in the initial stage of curing. When cured for 8h, the average shrinkage rate of the specimen with 5.0% content is only 62.00% of that of the blank specimen. This is because the diameter of CW is small, relatively dispersed in the material, easily blocks the pore channels, is not conducive to the migration of internal moisture, and at the same time the whiskers themselves have wetting properties, can adsorb part of the moisture, reduce the bleeding pores, thereby reducing its drying shrinkage. Since the main component of CW is CaCO3, the finely dispersed CaCO3 can play the role of crystal nucleus. A large amount of free Ca 2+ diffuses to the surface of CaCO3 particles and is physically adsorbed, providing a large number of initial nucleation points for the nucleation of Ca(OH)2, accelerating its generation, and then promoting the generation of C-(A)-S-H gel. With the extension of the curing age, the products such as Ca(OH)2, C-(A)-S-H, and N-A-S-H increase continuously, the internal shrinkage of the system accelerates, and the CW mainly bearing the load stress breaks, reducing its effect of inhibiting drying shrinkage. The change law of the drying shrinkage of the specimen after 120d of curing is almost the same as that after 90d of curing, which indicates that the system reaction tends to be stable and the drying shrinkage gradually tends to a constant value.

[0077] As Figure 2As shown in the figure, when curing the specimens, during the initial 8 hours of curing, the mass loss of the blank specimen is the most obvious, reaching 9.223 g / kg, while the mass loss of the specimen with a 5.0% CW dosage is only 5.395 g / kg. This is because nano-scale CW can better fill the internal pore structure, reducing the water loss due to excessive pores. As the curing age increases, the mass loss of the specimens gradually increases. When cured for 7 days, the mass loss of the specimens incorporated with CW increases significantly. Compared with the specimens cured for 3 days, the mass losses of the specimens with dosages of 1.0%, 3.0%, and 5.0% increase by 54.28%, 52.41%, and 68.18% respectively. This is mainly because CW promotes the reaction of the MK-BFS inorganic binder, and the generated C-(A)-S-H and N-A-S-H gels coat the surface of the whiskers, resulting in an increase in porosity and accelerating the evaporation and loss of water in the system. After 56 days, the mass loss of the specimens tends to be stable, and the mass loss first increases and then decreases with the increase of the CW dosage. When the CW dosage is relatively low, the mass loss of the specimens shows an increasing trend. This is because a small amount of CW is distributed inside the cementitious material, increasing the interfacial transition zone of the system, promoting the rapid evaporation and loss of water, and thus exacerbating the water loss of the specimens. In addition, when the dosage is relatively low (such as 1.0%, 3.0%), the promoting effect of CW on the internal reaction is relatively limited, resulting in serious water loss in the early stage of the system, a decrease in the content of bound water, and an increase in the mass loss of the specimens. However, when the dosage reaches 5.0%, the incorporation of excessive CW can accelerate the system reaction, facilitate the formation of gels containing bound water, and thus alleviate the mass loss of the specimens. As the curing age is further extended, the mass losses of the specimens cured for 90 days and 120 days do not change significantly compared with those cured for 56 days. This indicates that adding an appropriate amount of CW can not only effectively inhibit the mass loss during the initial curing stage but also maintain a relatively high content of bound water in the later curing stage, thereby effectively controlling the mass loss of the specimens.

[0078] As Figure 3 shown in the figure, as the CW dosage increases, the compressive strength of the specimens first increases and then decreases. Compared with the blank specimen, the 28-day compressive strengths of the specimens with CW dosages of 1.0% and 3.0% increase by 5.06% and 15.84% respectively. This is mainly because the incorporation of an appropriate amount of CW can give full play to its filling effect, optimize the pore size distribution, and improve the density inside the matrix. At the same time, CW is tightly combined with the matrix, which not only disperses the stress borne by the matrix, hinders the development of internal cracks, but also can improve the compressive strength of the material. However, the incorporation of excessive CW will have an adverse effect on the compressive strength of the specimens. Compared with the specimen with a 3.0% CW dosage, the 28-day compressive strength of the specimen with a 5.0% dosage decreases by 12.25%, confirming that the filling effect of CW on the internal pores of the structure is related to its dosage. This is mainly because when the CW dosage is too high, the agglomeration phenomenon between the whiskers is obvious, the distribution of whiskers in the matrix is uneven, and the dispersion degree is low, increasing the porosity and resulting in an uncompacted microstructure, thus reducing its compressive strength. From Figure 3It can also be found that with the extension of the curing age, the compressive strength of the specimens gradually increases. In addition, the incorporation of CW can promote the development of the compressive strength of the specimens. The 7-day compressive strength of the specimens with 3.0% CW content reaches 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] In Examples 1 to 3, CW mainly realizes shrinkage reduction and strengthening through the synergistic effects of multiple pathways such as physical filling, whisker bridging, crack deflection, whisker pulling out and fracture, and achieves shrinkage reduction and strengthening in multiple aspects from pore filling, structure strengthening to stress dispersion. First of all, the needle-shaped CW not only inhibits drying shrinkage by absorbing the free water content and reducing the capillary tension, but also can cooperate with the gel to achieve effective physical filling, refine the internal pore structure, reduce the proportion of large pores and reduce the pore connectivity, thereby reducing the shrinkage caused by water loss; Secondly, CW itself has the characteristics of high strength and high modulus. The network structure formed during pore filling has the function of bridging stress, forming numerous tiny "bridges" inside the material, connecting and supporting adjacent gel particles, effectively transmitting and dispersing the shrinkage stress, and then reducing the deformation of the system caused by the concentration of shrinkage stress; Thirdly, relying on the crack deflection mechanism, when CW disperses the shrinkage stress, it hinders the development of cracks in the matrix and guides the cracks to expand along the direction of the whiskers, consuming a large amount of shrinkage stress and improving the toughness of the material; At the same time, during the crack propagation process, CW will gradually be pulled out or fractured, and this process requires a large amount of energy, which is beneficial to inhibiting the shrinkage of the material; In addition, after CW fractures, the remaining part can still play a role in physical filling and stress dispersion to a certain extent, restricting the further expansion of cracks and effectively alleviating the shrinkage deformation of the specimens.

[0080] Example 4

[0081] An alkali-activated inorganic glue with a low drying shrinkage rate, by weight, the dosage of each component is as follows: 19.4 parts of MK, 77.6 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 3 parts of CB.

[0082] The modification method of the above alkali-activated inorganic glue with a low drying shrinkage rate is as follows:

[0083] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature and let it stand for 1 d before use to obtain the alkaline activator;

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

[0085] (3) Add 3 parts of CB and 13.68 parts of water into a beaker, and use an ultrasonic disperser model KH2200B to ultrasonically disperse for 20 min to obtain a uniform CB suspension. Ultrasonic treatment can quickly and uniformly disperse CB particles, effectively avoid particle agglomeration, improve the dispersibility and stability of CB; ultrasonically treating for 20 min, if the time is too short, the dispersion is insufficient, and if the time is too long, secondary agglomeration is likely to occur. The addition of an appropriate amount of water is conducive to the uniform dispersion of powdery CB and can also reasonably adjust the fluidity of the inorganic glue to ensure its bonding effect.

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

[0087] (5) Inject 52.28 parts of the alkaline activator prepared in step (1) into the mixed materials obtained in step (4), and use a planetary mortar 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 mixed liquid and the particles. Low-speed stirring in the early stage can prevent the splashing of the activator and water, 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 the uniform mixing of the materials and the alkaline activator and avoid local material residue. Subsequently, start the mortar mixer and stir quickly at a rate of 285 r / min for 2 min to accelerate the mixing rate of the mixing system, thoroughly disperse the particles, further make the materials mix evenly and improve the fluidity, and at the same time shorten the total stirring time, that is, obtain the alkali-activated MK-BFS inorganic glue modified with CB. In this process, "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system to generate N-A-S-H and C-(A)-S-H gels. The CB lamellae are dispersed in the matrix to form a "labyrinth effect", hindering the migration channels of water and ions, reducing permeability, and thus refining the pore structure. In addition, during the crack propagation process of the prepared inorganic glue, the CB particles can be adsorbed on the surfaces of the unreacted MK and BFS particles, reducing the interfacial pores between the gelling phase and the aggregate, enhancing the interfacial bonding force, reducing the weakness of the interfacial transition zone, and at the same time its lamellar structure can induce crack deflection and play a role in inhibiting cracks.

[0088] Example 5

[0089] An alkali-activated inorganic glue with low drying shrinkage rate, calculated by weight parts, the dosage of each component is as follows: 18.8 parts of MK, 75.2 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 6 parts of CB.

[0090] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 4.

[0091] Example 6

[0092] An alkali-activated inorganic glue with low drying shrinkage rate, calculated by weight parts, the dosage of each component is as follows: 18.2 parts of MK, 72.8 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 9 parts of CB.

[0093] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 4.

[0094] As Figure 4As shown in the figure, the addition of CB can effectively inhibit the drying shrinkage of the sample. However, as the CB content increases, the drying shrinkage of the sample decreases first and then increases. The 56-day drying shrinkage of the sample with a 3.0% content is 10.69%, 10.93%, and 8.27% lower than that of the blank sample and the samples with 6.0% and 9.0% content, respectively. This is mainly because the montmorillonite in CB has a typical layered crystal structure. When an appropriate amount of CB is added, the ionic bonds in the structure (such as Na + Damage, fractures, deflections, defects, or irregular stacking of crystal layers generate variable charges. Appropriate variable charges generate electrostatic repulsion between particles, which prevents them from approaching each other during drying, thereby suppressing specimen shrinkage. Furthermore, exposed hydroxyl groups (such as Fe-OH, Al-OH, and Si-OH) at the edges of the crystal lattice undergo protonation and deprotonation in solution, increasing their surface potential and the electrostatic repulsion between particles. Furthermore, the hydrophilicity and irregular macrostructure of CB give it strong adhesion when mixed with water, tightly agglomerating the CB particles. When water begins to dissipate, the bonding forces prevent them from separating, further suppressing specimen shrinkage. With the appropriate amount of CB incorporated, the material forms a gel network structure, enhancing specimen strength and stability. However, excessive CB incorporation can result in numerous CB particles being intercalated, disrupting this continuous structure. Furthermore, the uneven distribution of CB particles within the material can also lead to structural changes in localized regions. When the material is affected by external factors (such as temperature changes, humidity changes, etc.), microcracks appear in these weak areas and gradually expand with the extension of curing age, thereby increasing the drying shrinkage of the specimen.

[0095] In addition, by Figure 4 It can also be seen that the addition of CB significantly inhibits the early drying shrinkage of the specimen. The sample with a 3.0% CB addition experienced a drying shrinkage of 64.40% of the blank sample after 8 hours, while its drying shrinkage after 56 days reached 90.34%. This is primarily because as the reaction progresses, the attractive forces within the system bring the particles together, causing shrinkage, while the repulsive forces generated by the particle surface charges hinder their proximity. The attractive and repulsive forces between the particles gradually reach equilibrium, limiting specimen shrinkage to a certain extent.

[0096] like Figure 5As shown, the incorporation of an appropriate amount of CB can reduce the mass loss of specimens at different ages, but the incorporation of an excessive amount of CB will increase the mass loss of specimens. The mass loss of the blank specimen at 56 days reached 25.92 g / kg, while the mass loss of the specimen with a 3.0% dosage was 21.77 g / kg, only 83.98% of that of the blank specimen. However, when the CB dosage increased from 3.0% to 9.0%, the mass loss of the specimen increased by 31.14%. Since the main components of CB are montmorillonite and a small amount of other minerals, the incorporation of an appropriate amount of CB can fill the internal pores of the material; CB has a strong adsorption effect on water. When it is mixed with water, a large amount of adsorbed water will be replenished into the system, slowing down the loss rate of free water; at the same time, the water adsorbed by CB can maintain the humidity environment inside the specimen, preventing the specimen from generating microcracks due to drying, thereby reducing the mass loss of the specimen. However, the incorporation of an excessive amount of CB leads to an increase in the mass loss of the specimen, which is related to the strong water absorption of CB. Due to its layered lattice, water molecules can be adsorbed between the crystal layers and exist in the form of hydrated cations. In a dry environment, the water molecules are removed from between the crystal layers, reducing the mass of the specimen. In addition, as the CB dosage increases, montmorillonite forms a thixotropic gel and gradually transforms into a sol. The sol has a large density and is repulsive to water, resulting in the loss of water from CB and the destruction of its original properties. The adhesiveness and plasticity decrease, the internal structure is damaged, and some products fall off, further increasing the mass loss of the specimen.

[0097] It is not difficult to find that with the increase of the curing age, the mass loss of the specimen gradually increases. After 56 days, the mass losses of the blank specimen and the specimen with CB dosage both tend to be stable. This is because the residual water inside the specimen is the strongly bound water adsorbed on the particle surface. The polar water molecules in this strongly bound water are not only covalently bonded to the oxygen atoms and OH - on the basal plane of the clay mineral, but also undergo a hydration reaction with the cations on the surface and between the crystal layers of the clay mineral, forming a cation hydration shell. Due to the extremely strong adsorption of the strongly bound water, the mass loss of the specimen tends to be stable.

[0098] As Figure 6As shown in the figure, the addition of CB has no obvious effect on improving the compressive strength of the sample, and may even reduce the compressive strength of the sample at 1d. The addition of an appropriate amount of CB can slightly increase the compressive strength of the samples at 3d, 7d and 28d, but the addition of excessive CB will have an adverse effect on its compressive strength. The compressive strength of the sample with a CB content of 3.0% at 28d is 4.27% higher than that of the blank sample, while the compressive strength of the samples with CB content of 6.0% and 9.0% at 28d is 1.57% and 31.3% lower than that of the blank sample, respectively. The addition of an appropriate amount of CB can enhance the compressive strength, mainly because the reaction will generate colloidal particles with montmorillonite as the main body. These particles have a large specific surface area and surface energy, and can absorb a large amount 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. At the same time, the silicon-aluminum tetrahedron and aluminum-oxygen octahedron in the montmorillonite lattice in CB can be partially dissolved in an alkaline environment, and the released Si 4+ and Al 3+ With the Na in the alkaline activator + Combined with each other, NASH gel is formed, thereby improving the compressive strength of the sample. However, excessive CB incorporation will cause the montmorillonite to absorb water excessively and swell, affecting the internal microstructure; in addition, it will increase the number of fine particles in the system, reduce the friction between particles, and make it difficult to form a tight stack during the molding process. This poor particle stacking leads to an increase in the internal porosity of the sample and the generation of more harmful macropores. When subjected to pressure, these pores will become stress concentration points, leading to the generation of microcracks and reducing the compressive strength of the sample. Figure 6 It can also be found that with the extension of curing age, the compressive strength of the sample gradually increases. It is worth noting that the addition of CB is not conducive to the development of the early compressive strength of the sample. The compressive strength of the sample added with CB at 1 day is lower than that of the blank sample. The compressive strength of the sample with 3.0%, 6.0% and 9.0% addition at 1 day is 92.05%, 74.87% and 59.23% of that of the blank sample respectively. This is mainly due to the Na in the activator. + and SiO3 2- This is crucial for the reaction of silica-alumina raw materials such as BFS. In the early stages of the reaction, CB adsorbs these ions, resulting in a reduction in the excitation dose actually participating in the reaction of the silica-alumina raw materials, which 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 specimen.

[0099] In Examples 4 - 6, the CB mainly realizes shrinkage reduction and strengthening through the synergistic effects of multiple ways such as physical filling, water absorption and swelling, chemical activation and interface optimization, and formation of "labyrinth effect", achieving shrinkage reduction and strengthening in terms of microstructural 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, reduce the porosity, optimize the particle size distribution, improve the matrix density. At the same time, due to its water absorption and swelling, the volume increases, filling the microcracks generated by shrinkage, offsetting the drying shrinkage stress, and reducing the total shrinkage rate of the specimen. Second, the montmorillonite in CB is rich in active SiO2 and Al2O3, which is partially dissolved under the action of the alkali activator, releasing silicate monomers and participating in the formation of C-(A)-S-H gel, increasing the content of the gelling phase and strengthening the three-dimensional network structure of the gelling products. Third, the CB particles in the system can be adsorbed on the surfaces of unreacted MK and BFS particles, reducing the interfacial pores between the gelling phase and the aggregate, enhancing the interfacial bonding force, reducing the weakness of the interfacial transition zone. At the same time, its lamellar structure can induce crack deflection, playing a role in inhibiting cracks. Finally, the layered structure and surface negative charge of CB can adsorb free water molecules in the system, reducing the shrinkage caused by evaporation, and at the same time adsorbing harmful ions such as Cl - , SO4 2- and other harmful ions, reducing their migration rates. Its lamellae disperse in the matrix to form a "labyrinth effect", hindering the migration channels of water and ions, reducing the permeability, and thus refining the pore structure.

[0100] Example 7

[0101] An alkali-activated inorganic glue with a low drying shrinkage rate, by weight, the dosage of each component is as follows: 19 parts of MK, 76 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 5 parts of SG.

[0102] The preparation method of the above alkali-activated inorganic glue with a low drying shrinkage rate is as follows:

[0103] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature and let it stand for 1 d for later use to obtain the alkaline activator;

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

[0105] (3) Add 5 parts of SG to the above-mentioned mixed powder, and use a planetary mortar mixer of model NJ-160B to stir again at a rate of 140 r / min for 3 min to fully mix SG with the mixed powder, obtaining a mixed material; during this process, mechanical stirring is used to fully mix, enabling the fine particles of SG to effectively fill the gaps between the particles of MK and BFS, achieving physical filling, improving the density of the mixed material, and providing a more stable matrix structure for subsequent reactions;

[0106] (4) Inject 52.28 parts of the alkaline activator prepared in step (1) into 100 parts of the mixed material obtained in step (3), and use a planetary mortar mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min, enabling the alkaline activator to slowly and evenly disperse on the surface of the material particles, fully contact the reaction sites, reduce bubbles and control the reaction rate, avoid caking of local mixed materials, and at the same time prevent the splashing of the activator; 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 the uniform mixing of the material and the alkaline activator and avoid local material residues; subsequently, start the planetary mortar mixer of model NJ-160B to stir quickly at a rate of 285 r / min for 2 min to accelerate the mixing rate of the mixing system, thoroughly disperse the particles, promote the violent mixing of the activator and the material, make the reaction more complete, and improve the reaction efficiency; during this process, "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system, generating N-A-S-H and C-(A)-S-H gels. The rough microstructure on the surface of SG can provide more nucleation sites for the gel reaction, promote the heterogeneous nucleation of the gel, accelerate the formation and curing of the gel network, and indirectly enhance the early strength and structural stability;

[0107] (5) Add 13.68 parts of water to the gel obtained in step (4), and after quickly stirring for 3 min, the alkali-activated MK-BFS inorganic glue modified by adding SG is obtained; by adding an appropriate amount of water, the fluidity of the inorganic glue is reasonably adjusted to ensure its bonding effect. The high fineness (large specific surface area) and grading characteristics of SG particles enable them to fill the pores between particles, form a more compact 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 glue with a low drying shrinkage rate, by weight, the dosage of each component is as follows: 17 parts of MK, 68 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 15 parts of SG.

[0110] The preparation method of the above-mentioned alkali-activated inorganic glue with a low drying shrinkage rate is the same as that of Example 7.

[0111] Example 9

[0112] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 15 parts of MK, 60 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 25 parts of SG.

[0113] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 7.

[0114] As Figure 7 shown, the incorporation of SG can better inhibit the drying shrinkage of the specimen, and with the increase of the SG dosage, the drying shrinkage of the specimen decreases. When the dosage is 25.0%, the drying shrinkage value of the specimen is the lowest, and its 56-day drying shrinkage is 9.938 mm / m, which is 9.19% and 5.24% lower than that of the blank sample and the specimen with 5.0% dosage respectively. Since SG contains mineral phases such as C3S and C2S, its reaction generates crystals such as Ca(OH)2. The crystals themselves hardly undergo drying shrinkage. At the same time, due to the relatively high hardness of SG particles, the unhydrated SG particles and the crystallization products together play a role similar to the skeleton inside the system, better inhibiting the drying shrinkage of the specimen. Obviously, with the prolongation of the curing age, the drying shrinkage values of specimens with different SG dosages gradually increase, and the drying shrinkage of all specimens tends to be stable at 90 days. This is attributed to two aspects. On the one hand, the pore structure inside the specimen is continuously refined, the capillary network gradually closes, and the dense microstructure forms resistance to water migration, reducing the capillary tension caused by water evaporation. On the other hand, the humidity inside the specimen tends to balance with the environmental humidity, and the water gradient disappears. At this time, the shrinkage process driven by the humidity difference stops due to the loss of driving force.

[0115] As Figure 8As shown, the incorporation of SG can effectively reduce the mass loss of specimens. Compared with the blank specimen, the mass loss of the specimen with 25.0% SG content is reduced by 29.2%. With the increase of SG content, the mass loss of the specimen gradually decreases. Compared with the specimen with 5.0% content, the mass loss of the specimen with 25.0% content is reduced by 12.5%. On the one hand, the SG particles have a small particle size and a wide distribution, which can effectively fill the capillary pores and microcracks in the internal structure, reduce the internal porosity, and thus improve the matrix density. On the other hand, the dense internal structure reduces the penetration paths of water and harmful ions, thereby delaying their deterioration and reducing the mass loss caused by water evaporation or chemical erosion. At the same time, it can also be found from the figure that with the increase of the curing age, the mass loss of the specimen gradually increases. The mass loss of the specimen with 15.0% content at 120 d is 14.34% higher than that at 7 d. The gradual increase of the specimen mass loss with the increase of the age may be due to various factors. During the curing process, the system continues to hydrate, some substances are consumed in the chemical reaction, and gas escapes, resulting in a decrease in the mass of the specimen. At the same time, the evaporation of water is also an important reason. The internal water of the specimen continuously loses during long-term curing, especially a large amount of free water generated in the early reaction, which gradually volatilizes with the extension of the age, resulting in the mass loss of the specimen. It should be noted that the mass loss of the blank specimen and specimens with different SG contents is relatively obvious in the early stage, while the mass of the specimen tends to be stable after 56 d. This is because the free water on the surface and in the pores of the specimen evaporates rapidly in the early stage of the reaction, resulting in a significant decrease in mass loss. With the increase of the age, the pore structure of the system has been refined, the connectivity has decreased, the water migration is limited, and the mass tends to be stable. By comparing the effects of SG content on the mass loss and drying shrinkage of the specimen, it can be found that there is an approximately positive correlation between the drying shrinkage and the change of mass loss. When the drying shrinkage is small, the corresponding mass loss of the specimen is also small.

[0116] It can be seen from Figure 9 that the incorporation of SG has no obvious effect on improving the compressive strength of the 1-day specimen in the early stage. In the early stage of the reaction, due to the presence of inert minerals such as RO in SG itself, it basically does not participate in the hydration reaction, reduces the overall reaction activity, and decreases the reaction rate of the composite system, resulting in a large number of pores in the specimen due to insufficient reaction and insufficient matrix density. However, the incorporation of SG can better improve the compressive strength of the specimen at 3 d, 7 d and 28 d, and with the increase of SG content, the later compressive strength shows a trend of first increasing and then decreasing. Compared with the blank specimen, the 28-day compressive strengths of the specimens with 5.0% and 15.0% SG contents are increased by 4.38% and 11.35% respectively. This is mainly because the reaction of BFS is faster in the early stage, and there is a lack of Ca 2+ in the later stage of hydration. And the SG itself has a high CaO content, and the Ca(OH)2 generated by its reaction can increase the alkali equivalent in the solution, thereby accelerating the hydration of BFS, and Ca 2+Absorption by BFS further promotes the dissociation and hydration of SG, creating a benign synergistic hydration effect between SG and BFS, generating a large amount of C-(A)-SH zeolite-like products. These products fill the pores formed in the initial reaction, improve the internal structure, and enhance the density. However, the incorporation of excessive SG can adversely affect the compressive strength of the specimen. This is because the free MgO and CaO in the system slowly undergo hydration under alkaline conditions, resulting in volume expansion. This hydration expansion can cause microcracks within the matrix, destroying the structural integrity and thus affecting its compressive strength.

[0117] The SG in Examples 7-9, primarily through the synergistic effects of physical filling, pozzolanic reaction, and micro-expansion, deeply optimizes the microstructure of the cementitious material, significantly reducing internal porosity and defects, significantly enhancing the material's shrinkage resistance, and effectively reducing material mass loss. First, in terms of physical filling, the SG particles exhibit ultra-fine particle size and a globally dispersed distribution. These extremely small SG particles are able to effectively fill the intricate capillary pores and microcracks within the specimen. As the filling process progresses, the porosity within the specimen continuously decreases, significantly improving the overall density of the material, reducing the permeation channels for free water and harmful ions, minimizing mass loss due to water evaporation and chemical attack, and effectively inhibiting drying shrinkage. Second, the active silicates and aluminates contained in the SG (such as CS, CS, and CA) undergo a complex series of pozzolanic reactions in an alkaline environment, generating a large amount of C-(A)-SH gel. These gels interweave to form a dense gel network structure, further enhancing the density of the matrix. Furthermore, the volcanic ash reaction consumes a significant amount of Ca(OH)2 produced during the reaction. Ca(OH)2 is highly susceptible to shrinkage during drying. Reducing its content can effectively reduce the material's shrinkage tendency, thereby improving its structural stability. Finally, regarding the micro-expansion effect, the f-CaO and f-MgO in SG accelerate their hydration in a high-alkaline environment, generating Ca(OH)2 and Mg(OH)2. The expansion effect generated during the reaction is fully absorbed by the microporous structure of the system and cleverly converted into micro-expansion, effectively compensating for the shrinkage that occurs during sample drying.

[0118] Example 10

[0119] The invention discloses an alkali-activated inorganic adhesive with low drying shrinkage. The amounts of the components are as follows, calculated by weight: 19.8 parts of MK, 79.2 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, and 1 part of PEG.

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

[0121] (1) Preparation of alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature, and let it stand for 1 day for later use to obtain the alkaline activator;

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

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

[0124] (4) Inject the mixed solution prepared in step (3) into the mixed powder in step (2), and use a planetary cement paste mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min to wet and disperse the MK and BFS particles, ensuring sufficient contact between the mixed solution and the particles. Low-speed stirring can prevent the splashing of the activator and water, and also reduce internal bubbles and avoid local caking; 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 uniform mixing of the material and the alkaline activator and avoid local material residue; Subsequently, start the planetary cement paste mixer and stir quickly at a rate of 285 r / min for 2 min. By accelerating the collision and cross-linking of gel particles, the material is further mixed evenly, promoting the preliminary formation of a three-dimensional network structure and shortening the total stirring time; During this process, "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system to generate N-A-S-H and C-(A)-S-H gels. The PEG molecular chain binds to the gel through hydrogen bonds or physical entanglement, endowing the gel with flexibility and forming an "elastic buffer layer" to absorb 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), and quickly stir for 3 min to obtain the alkali-activated MK-BFS inorganic glue modified with PEG; By adding an appropriate amount of water, the fluidity of the inorganic glue is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic glue, the PEG molecular chain can play a skeleton support role and better prevent the shrinkage of the pore wall 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 relieve the shrinkage cracking caused by rigid constraints.

[0126] Example 11

[0127] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 19.4 parts of MK, 77.6 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 3 parts of PEG.

[0128] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 10.

[0129] Example 12

[0130] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 19.0 parts of MK, 76.0 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 5 parts of PEG.

[0131] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is the same as that of Example 10.

[0132] Such as Figure 10As shown, the incorporation of PEG can better alleviate the drying shrinkage of the specimens, and with the increase of the PEG dosage, the drying shrinkage of the specimens shows a trend of first decreasing and then increasing. When the PEG dosage is 2.0%, the drying shrinkage value of the specimens reaches the lowest, and its 28-day drying shrinkage value is only 72.43% of that of the blank specimen in the same period. The drying shrinkage of the alkali-activated BFS specimens is related to the dosage and molecular weight of PEG. Appropriate incorporation of PEG can achieve good shrinkage reduction effect, but excessive incorporation of PEG 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 the surface tension during the drying process of the specimens helps to reduce the capillary stress generated by water evaporation, thus reducing the drying shrinkage. At the same time, PEG molecules can fill the internal pores. When the specimens are dried, the PEG molecules filled in the pores can play a role of skeleton support and better prevent the pore walls from shrinking due to capillary negative pressure. However, too high a PEG dosage will lead to uneven internal pore structure and increased porosity of the specimens. Due to the moisture retention effect, the shrinkage of the specimens is not obvious in the early stage, but with the prolongation of the curing age, the water gradually evaporates, and the increased pores will exacerbate the shrinkage deformation during the drying process of the specimens. In addition, excessive PEG will form an isolation layer between MK, BFS and the alkali activator, weakening the interfacial bonding force between them, making the specimens prone to microcracks and defects during the shrinkage process and increasing their shrinkage deformation. In comparison, the shrinkage reduction effect of PEG is more obvious in the early stage of curing. When cured for 8 h, the drying shrinkage value of the specimen with a dosage of 2.0% is 58.45% of that of the blank specimen. This may be because PEG has an obvious influence on the reaction rate of the system in the early stage of curing. PEG adsorbs on the surfaces of MK and BFS particles, slowing down the contact between the active components and the activator, being unfavorable for the effective collision between the reactants, and reducing the generation amount of the C-(A)-S-H gel product with larger shrinkage.

[0133] As Figure 11As shown, when cured for 8 h, the mass loss of the blank sample is the most obvious, reaching 9.223 g / kg, while the mass loss of the sample with a 2.0% dosage is only 3.598 g / kg. The incorporation of PEG can effectively reduce the early mass loss of the sample. This is mainly because the chain-like molecular structure of PEG can effectively fill the particle gaps, reduce the accelerated water loss due to excessive pores, and at the same time, the water retention effect of PEG reduces the water loss of the system to a certain extent. With the extension of the curing age, the mass loss of the sample gradually increases. When cured for 7 d, the mass loss of the sample incorporated with PEG increases significantly. Compared with the 3-d sample, the mass losses of the samples with dosages of 1.0%, 2.0%, and 3.0% increase by 67.75%, 91.15%, and 108.61% respectively. At this time, the mass losses of the samples incorporated with PEG are all greater than that of the blank sample. This is mainly because the PEG molecules are wrapped inside the C-(A)-S-H gel, weakening its water retention ability, thus accelerating the water loss and resulting in an increase in the mass loss of the sample. It is also found from the figure that after 7 d, the mass loss of the sample increases with the increase of the PEG dosage. Compared with the sample with a 1% dosage, the mass losses of the samples with PEG dosages of 2.0% and 3.0% at 56 d increase by 28.62% and 54.55% respectively. This is mainly because a high PEG dosage will interfere with the normal crystallization process of the reaction products, making their structure loose. At the same time, PEG will adsorb on the surface of the reaction products, hinder the close combination between the products, and weaken the integrity of the system. In addition, too high a PEG dosage will increase the pores inside the matrix and the connectivity of the pores, providing a more favorable channel for the water loss of the system, resulting in an increase in the mass loss of the sample.

[0134] As can be seen from Figure 12It can be seen that the incorporation of PEG can better improve the early compressive strength of the specimens. The compressive strengths of the specimens with different dosages at 1d and 3d are higher than those of the blank specimens in the same period. The compressive strength of the specimen with a dosage of 1.0% at 3d is increased by 35.51% compared with the blank specimen. This is because the PEG molecule contains -OH, which reacts with the active groups on the surface of MK or BFS, can accelerate the formation of gel products, is beneficial to refining pores and reducing connected pores, and optimizing the pore size distribution. In addition, an appropriate amount of PEG molecules can play a role in filling pores and densifying the structure in the system. However, with the increase of the PEG dosage, the compressive strengths of the specimens at different ages show a downward trend, and the compressive strengths of the specimens with dosages of 2.0% and 3.0% at 7d and 28d are lower than those of the blank specimens in the same period. The compressive strengths of the specimens with PEG dosages of 2.0% and 3.0% at 28d are reduced by 9.21% and 15.62% respectively compared with the blank specimens in the same period. This is mainly because too high PEG incorporation will form aggregates inside the material, generating large pores. Stress concentration is likely to occur in these aggregates and the weak areas around the pores, reducing their compressive strength. At the same time, too much PEG will cover the particle surface, hindering the effective bonding of gel products between particles, being unfavorable for the reaction to proceed, reducing the generation amount of gel products, and affecting the continuity and integrity of the gel network, thus resulting in the reduction of the compressive strength of the specimens.

[0135] In Examples 10 to 12, PEG mainly realizes the multi-faceted anti-cracking and shrinkage-reducing effects from physical inhibition, structure optimization to chemical compensation through the synergistic action of multiple ways 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". First of all, as a surfactant, PEG significantly reduces the surface tension of the pore solution and reduces the capillary pressure, thereby alleviating the shrinkage stress caused by water evaporation or self-drying. Especially in a dry environment, it can effectively inhibit the shrinkage deformation caused by capillary negative pressure. Secondly, PEG refines the pore structure through physical filling and the interaction with reaction products (such as N-A-S-H gel), reduces the proportion of large pores and the pore connectivity, forms a more uniform micropore distribution to disperse the shrinkage stress, delays the water migration rate, and reduces the shrinkage caused by rapid water loss. Thirdly, the hydrophilic property of PEG can adsorb and slowly release water, maintain the internal humidity of the system, delay the occurrence of self-shrinkage, and at the same time promote the continuous reaction of BFS in the later stage to generate a dense gel structure to compensate for the chemical shrinkage. In addition, the PEG molecular chain binds to the N-A-S-H gel through hydrogen bonds or physical entanglement, endows the gel with flexibility and forms an "elastic buffer layer" to absorb the shrinkage stress to inhibit the initiation and expansion of microcracks. Finally, the incorporation of PEG slightly reduces the elastic modulus of the material, but can significantly improve the strain capacity and relieve the shrinkage cracking caused by rigid constraints.

[0136] Example 13

[0137] An alkali-activated inorganic glue with low drying shrinkage rate. By weight, the dosage of each component is as follows: 18.6 parts of MK, 74.4 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 2 parts of PEG, and 5 parts of CW.

[0138] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is as follows:

[0139] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature, and let it stand for 1 d for later use to obtain the alkaline activator;

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

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

[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 140 r / min for 3 min to fully stir it with the mixed powder to obtain a mixed material; In this process, mechanical stirring is used to effectively achieve the physical filling of CW, reduce the porosity, and improve the matrix density;

[0143] (5) Inject the mixed solution prepared in step (3) into the mixed materials obtained in step (4), and use a planetary mortar mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min, so that the mixed solution 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 caking of local mixed materials, and at the same time prevent the splashing of the activator; 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 the uniform mixing of the materials and the alkaline activator, and avoid local material residues; then, start the planetary mortar mixer of model NJ-160B and stir quickly at a rate of 285 r / min for 2 min to break the aggregates and promote the dissolution of ions and the formation of gels; during this process, the "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system, generating N-A-S-H and C-(A)-S-H gels. The PEG molecular chains are combined with the gels through hydrogen bonds or physical entanglement, endowing the gels with flexibility and forming an "elastic buffer layer" to absorb the shrinkage stress to inhibit the initiation and propagation of microcracks. CW, relying on the crack deflection mechanism, hinders the development of cracks in the matrix and guides the cracks to expand along the direction of the whiskers when dispersing the shrinkage stress of the generated gels, 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), and quickly stir for 3 min to obtain the alkali-activated MK-BFS inorganic glue modified by incorporating PEG and CW; by adding an appropriate amount of water, the fluidity of the inorganic glue is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic glue, the PEG molecular chains can play a skeleton support role and preferably prevent the shrinkage of the pore wall 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 relieve the shrinkage cracking caused by rigid constraints; in addition, CW will gradually be pulled out or broken, and this process requires a large amount of energy, which is beneficial to inhibiting the shrinkage of the matrix; after CW is broken, the remaining part can still play a role in physical filling and stress dispersion, restricting the further expansion of cracks and effectively relieving the shrinkage deformation.

[0145] This example makes full use of the functions of PEG to reduce the surface tension of the pore solution, refine the pore structure, adsorb and slowly release water, form an "elastic buffer layer", and the shrinkage reduction effects of CW such as physical filling, whisker bridging, crack deflection, whisker pulling out and breaking. Through the reasonable compounding of the two, the synergistic shrinkage reduction of the MK-BFS inorganic glue is effectively achieved.

[0146] Example 14

[0147] An alkali-activated inorganic glue with low drying shrinkage rate, by weight, the dosage of each component is as follows: 14.6 parts of MK, 58.4 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 2 parts of PEG and 25 parts of SG.

[0148] The preparation method of the above alkali-activated inorganic glue with low drying shrinkage rate is as follows:

[0149] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature and let it stand for 1 d for later use to obtain the alkaline activator;

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

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

[0152] (4) Add 25 parts of SG to the above-mentioned (2) mixed powder, and use a planetary paste mixer of model NJ-160B to stir again at a speed of 140 r / min for 3 min to fully mix SG and the mixed powder to obtain a mixed material; In this process, mechanical stirring is used to fully mix. The fine particles of SG can effectively fill the particle gaps between MK and BFS, realizing physical filling, improving the density of the mixed material, and providing a more stable matrix structure for subsequent reactions;

[0153] (5) Inject the mixed liquid obtained in step (3) into the mixed material obtained in step (4), and use a planetary mortar mixer of model NJ-160B to stir at a rate of 140 r / min for 1 min, so that the mixed liquid 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 caking of local mixed materials, and at the same time prevent the splashing of the activator; after stirring, stop stirring for 1 min, and 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 the uniform mixing of the material and the alkaline activator and avoid local material residues; then, start the planetary mortar mixer of model NJ-160B and stir quickly at a rate of 285 r / min for 2 min to break the aggregates and promote ion dissolution and gel formation; during this process, "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system to generate N-A-S-H and C-S-H gels. The PEG molecular chains are combined with the gels through hydrogen bonds or physical entanglements, endowing the gels with flexibility and forming an "elastic buffer layer" to absorb the shrinkage stress and inhibit the initiation and propagation of microcracks; the rough microstructure of the SG surface can provide more nucleation sites for the gel reaction, promote the heterogeneous nucleation of the gels, accelerate the formation and curing of the gel network, and indirectly improve the early strength and structural stability.

[0154] (6) Add 13.68 parts of water to the gel obtained in step (5), and after rapid stirring for 3 min, the alkali-activated MK-BFS inorganic glue modified by incorporating PEG and SG is obtained; by adding an appropriate amount of water, the fluidity of the inorganic glue is reasonably adjusted to ensure its bonding effect. During the crack propagation process of the prepared inorganic glue, the PEG molecular chains can play a role in skeleton support and better prevent the shrinkage of the pore wall 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 relieve the shrinkage cracking caused by rigid constraints; the high fineness (large specific surface area) and grading characteristics of the SG particles enable them to fill the pores between the particles, form a denser particle packing structure, improve the contact between the matrix particles, and provide a more uniform internal environment for the gel reaction.

[0155] This example makes full use of the above-mentioned functions of PEG to reduce the surface tension of the pore solution, refine the pore structure, adsorb and release moisture slowly, form an "elastic buffer layer", and the shrinkage reduction effects of SG such as physical filling, pozzolanic reaction, and micro-expansion effect. Through the reasonable compounding of the two, the synergistic shrinkage reduction of the inorganic glue is effectively achieved.

[0156] Example 15

[0157] An alkali-activated inorganic glue with a low drying shrinkage rate, and the dosage of each component is as follows according to the weight parts: 18.4 parts of MK, 73.6 parts of BFS, 43.85 parts of water glass, 8.43 parts of sodium hydroxide, 13.68 parts of water, 3 parts of CB and 5 parts of CW.

[0158] The preparation method of the alkali-activated inorganic glue with low drying shrinkage rate is as follows:

[0159] (1) Preparation of the alkaline activator: Slowly inject NaOH with a density of 2.13 g / cm 3 into the water glass solution, and continuously stir 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%. Place the prepared compound solution in a beaker, cool it to room temperature, and let it stand for 1 day for later use to obtain the alkaline activator;

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

[0161] (3) Add 3 parts of CB and 13.68 parts of water to a beaker, and use an ultrasonic disperser of model KH2200B to ultrasonically disperse for 20 min to obtain a uniform CB suspension. Ultrasonic treatment can quickly and uniformly disperse CB particles, effectively avoid particle agglomeration, improve the dispersibility and stability of CB; Ultrasonic treatment for 20 min, too short time will result in insufficient dispersion, and too long time will 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 fluidity of the inorganic glue to ensure its bonding effect;

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

[0163] (5) Inject the prepared CB suspension in step (3) into the mixed powder obtained in step (4), and use a cement paste mixer of model NJ-160B to stir at a rate of 140 r / min for 3 min. After the materials are uniformly mixed, a mixed material is obtained. This process makes the prepared CB suspension fully contact with the mixture through mechanical stirring. Based on the micro-size effect, CB better fills and embeds into the micro-pores to improve the matrix density;

[0164] (6) Inject the alkaline activator prepared in step (1) into the mixed material obtained in step (5), and use a planetary mortar 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 caking of local mixed materials, and at the same time prevent the splashing of the activator; 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 the uniform mixing of the material and the alkaline activator and avoid local material residues; then, start the planetary mortar mixer of model NJ-160B and stir quickly at a rate of 285 r / min for 2 min to break the aggregates and promote ion dissolution and gel formation; during this process, "dissolution-polymerization" and geopolymerization reactions occur simultaneously in the system to generate N-A-S-H and C-(A)-S-H gels. The CB lamellae are dispersed in the matrix to form a "labyrinth effect", hindering the migration channels of water and ions, reducing permeability, and refining the pore structure; at the same time, the CB particles can be adsorbed on the surface of unreacted MK and BFS particles, reducing the interfacial pores between the gelling phase and the aggregate, reducing the weakness of the interfacial transition zone. Its lamellar structure can induce crack deflection and play a role in inhibiting cracks; in the matrix, CW hinders the development of cracks and guides the cracks to expand along the direction of the whiskers by virtue of the crack deflection mechanism when dispersing and generating gel shrinkage stress, consuming a large amount of shrinkage stress and improving the toughness of the material; in addition, a large amount of energy is consumed during the process of CW being gradually pulled out or broken, which is beneficial to inhibiting the shrinkage of the material; after CW breaks, the remaining part can still play a role in physical filling and stress dispersion, restricting the further expansion of cracks and effectively alleviating shrinkage deformation.

[0165] In this example, the above-mentioned shrinkage reduction effects such as physical filling, chemical activation, interface optimization, adsorption regulation of CB and whisker bridging, crack deflection, whisker pulling out and breaking of CW are fully utilized. Through the reasonable compounding of the two, the synergistic shrinkage reduction of inorganic glue is better realized.

[0166] Comparative Example 1

[0167] An alkali-activated MK-BFS inorganic glue, by weight, the dosage of each component is as follows:

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

[0169] The preparation method of the above alkali-activated MK-BFS inorganic glue is as follows:

[0170] (1) Preparation of the alkaline activator: The density is 2.13 g / cm 3The NaOH was slowly poured into the water glass solution, and a glass rod was used to continuously stir 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 standing for 1 day for later use to obtain an alkaline activator.

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

[0172] (3) Inject 52.28 parts of the alkaline activator and 13.68 parts of water prepared in step (1) into 100 parts of the mixed powder obtained in step (2), and 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 full contact between the mixed liquid and the particles. Low-speed stirring can prevent the splashing of the activator and water, and can also reduce internal bubbles and avoid local caking; Subsequently, start the cement paste mixer and stir rapidly at a rate of 285 r / min for 2 min to thoroughly disperse the particles, further mix the materials evenly, accelerate the system reaction and improve the fluidity, and at the same time shorten the total stirring time, that is, an alkali-activated MK-BFS inorganic glue is obtained.

[0173] The drying shrinkage test and compressive strength test were respectively carried out on the alkali-activated MK-BFS inorganic glue prepared in the above Examples 1 to 15 and Comparative Example 1, and the test results are shown in Table 1 below. It can be seen from the table that in Examples 1 to 15 of the present invention, by incorporating CW, CB, SG, and PEG modification materials, the drying shrinkage value of the alkali-activated MK-BFS inorganic glue is preferably reduced from aspects such as physical filling, whisker bridging, chemical activation and interface optimization, pozzolanic reaction, micro-expansion effect, reducing the surface tension of the pore solution, and forming an "elastic buffer layer", and its compressive strength is improved. And Example 13 has the best improvement effect on the drying shrinkage of the alkali-activated MK-BFS inorganic glue.

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

[0175]

[0176] It can be seen from the comparison between the above Examples 1 to 12 and Examples 13 to 15 that, compared with the separate incorporation of the modified materials, the incorporation of different modified materials in a reasonable range has a more obvious effect on reducing the drying shrinkage and increasing the compressive strength of the alkali-activated MK-BFS inorganic glue. This is mainly due to the synergistic complementary effect and multi-scale effect of different modified materials. Reasonable incorporation can better optimize the pore structure, improve the matrix densification, effectively transfer and disperse the shrinkage stress, and reduce the cracking risk. At the same time, the reasonable incorporation of different modified materials can also give full play to the multiple action mechanisms of the materials, realizing the improvement of the compressive strength while reducing the drying shrinkage.

[0177] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment 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 glue with a low drying shrinkage rate, characterized in that, It includes a solid component and a liquid component. By weight parts, the solid component includes 15 - 20 parts of MK, 60 - 80 parts of BFS, and 1 - 25 parts of a modification material; The liquid component includes 41.82 - 62.74 parts of an 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 alkaline activator is a compound solution obtained by mixing NaOH and a water glass solution; the mass ratio of NaOH to the water glass solution is 0.16 - 0.25:1; The modification material is selected from one or more of calcium carbonate whiskers, bentonite, steel slag, and polyethylene glycol.

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

85.

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

4. The alkali-activated inorganic glue with low drying shrinkage rate according to claim 1, characterized in that In the alkaline activator, the water glass modulus is 1.0 - 1.4 and the Na₂O content is 8.0 - 12.0%.

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

0.

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

7. The alkali-activated inorganic glue with low drying shrinkage rate according to claim 1, characterized in that The fineness of the steel slag is 600 - 800 mesh, and the specific surface area is 430.2 - 482.8 m 2 / kg.

8. The alkali-activated inorganic adhesive with low drying shrinkage rate 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 / cm 3 and the thickness is 100-200 nm.

9. The alkali-activated inorganic glue with low drying shrinkage rate according to claim 1, characterized in that, The mass proportion of the calcium carbonate whiskers in the solid component is 1.0 - 5.0%.

10. The alkali-activated inorganic adhesive with low drying shrinkage rate according to claim 1, characterized in that, The mass proportion of the bentonite in the solid component is 3.0 - 9.0%.

11. The alkali-activated inorganic glue with low drying shrinkage rate according to claim 1, characterized in that, The mass proportion of the steel slag in the solid component is 5.0 - 25.0%.

12. The alkali-activated inorganic glue with low drying shrinkage rate according to claim 1, characterized in that, The mass proportion of the polyethylene glycol in the solid component is 1.0 - 3.0%.

13. The preparation method of the alkali-activated inorganic glue with low drying shrinkage rate according to any one of claims 1 to 12, characterized in that, The steps are as follows: S1: Inject NaOH into the water glass solution, and after stirring, obtain a compound solution with a water glass modulus of 1.0 - 1.4 and a Na₂O content of 8.0 - 12.0%. After standing for 1 d, obtain the alkaline activator; S2: Add 15 - 20 parts of MK and 60 - 80 parts of BFS to a cement paste mixing pan, and after dry mixing for 3 min, obtain a mixed powder; S3: Add the modification material to the mixed powder obtained in S2 according to the ratio, and after stirring, obtain a mixed material; S4: Inject 41.82 - 62.74 parts of the alkaline activator prepared in S1 and 9.68 - 13.68 parts of water into 100 parts of the mixed material obtained in S3. After slow stirring and fast stirring, an alkali-activated inorganic glue with a low drying shrinkage rate is obtained.

14. Application of the alkali-activated inorganic glue with a low drying shrinkage rate according to any one of claims 1 - 12 in strengthening concrete.

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