Organic-inorganic composite ternary microspheres capable of self-riveting in a cement base body, and preparation and application thereof

Abstract

The present application relates to the technical field of building materials, and particularly relates to an organic-inorganic composite ternary microsphere capable of realizing self-riveting in a cement matrix, and a preparation and application thereof, the microsphere comprising: a microcapsule body with a repairing agent as a core and a semi-interpenetrating network hydrogel material as a shell; the shell surface is inlaid with a pozzolanic material, and the pozzolanic material is used for pozzolanic reaction with the cement matrix to realize riveting of the two. The preparation method comprises the following steps: pre-mixing the pozzolanic material and water to obtain a suspension; adding semi-interpenetrating network hydrogel prepolymers into the suspension to obtain a first mixture; mixing the first mixture, the repairing agent and an emulsifier to obtain a second mixture; and crosslinking and solidifying the second mixture by using a sharp hole-coagulation bath method to form the microsphere. The microsphere of the present application can successfully construct a self-riveting structure with the cement matrix, and solves the problems of poor interface bonding and low self-repairing efficiency caused by the water-absorbing microcapsule as the shell of the hydrogel.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to an organic-inorganic composite ternary microsphere that can achieve self-riveting in a cement matrix, its preparation and application. Background Technology

[0002] Cement-based materials are the most widely used building materials, but due to their high brittleness, they are prone to microcracks. If not repaired in time, they will induce macrocracks, which will reduce strength, cause carbonization, and affect their durability and service life.

[0003] To address the aforementioned issues, a self-healing concrete material has been proposed. This self-healing concrete mimics the healing mechanism of biological tissue damage by embedding self-healing materials within the matrix. When microcracks appear, the self-healing material is triggered, sealing the cracks and performing in-process repair to prevent their expansion into macroscopic cracks. For example, microencapsulation self-healing technology microencapsulates polymer adhesives to form a shell-core structured self-healing material, which is then embedded in a cement matrix to construct a cement-based self-healing system. This system offers advantages such as strong applicability, low cost, and easy dispersion within the cement matrix. Compared to traditional repair methods, this self-healing approach offers advantages such as good stability, high cost-effectiveness, and strong autonomy, thus attracting widespread attention from researchers both domestically and internationally.

[0004] In microcapsule self-healing technology, water-absorbing microcapsules can also be used as an "internal curing" agent in cementitious matrices. They utilize water-absorbing resins with water-absorbing swelling and water-losing shrinkage properties as wall materials. These resins are cross-linked hydrogel networks composed of water-soluble polymers, capable of absorbing large amounts of water and swelling to form an insoluble gel; when the surrounding humidity decreases, they gradually release the water. This reversible cycle allows them to function as a "reservoir" within mortar and concrete when used as an internal curing agent, reducing the auto-shrinkage of the mortar or concrete, thereby improving its volume stability, freeze-thaw resistance, and self-sealing properties, and enabling long-term, repeated self-healing effects. However, how to further improve the repair effect of microcapsule self-healing technology remains a pressing technical problem to be solved. Summary of the Invention

[0005] During the research and development process, it was discovered that water-absorbing microcapsules, due to their swelling upon absorbing water during cement / concrete mixing and their shrinkage upon water loss after cement / concrete hardening, weaken the interfacial bonding between the microcapsules and cement / concrete, and may even create voids. This reduces the response efficiency of the microcapsules to crack triggering and may even negatively affect the compactness of cement / concrete.

[0006] Based on this discovery, this invention proposes an organic-inorganic composite ternary microsphere capable of self-riveting in a cement matrix, along with its preparation and application. Specifically, it proposes a microsphere for building materials, which is an organic-inorganic composite ternary microsphere. Its structure comprises an organic-inorganic composite shell formed by combining an active pozzolanic material with a semi-interpenetrating network hydrogel, and then encapsulating a repair agent to form a ternary microsphere system. The pozzolanic material is uniformly distributed in a "rivet" shape at the submicroscopic level and embedded on the surface of the microsphere. The building material microsphere with the "rivet" structure provided by this invention retains the advantages of water-absorbing microcapsules while successfully constructing a self-riveting structure with the cement matrix. This solves the problem of poor interfacial bonding caused by the shrinkage of the hydrogel when the water-absorbing microcapsules act as the shell, hindering the full realization of self-repair efficiency.

[0007] Specifically, the present invention provides microspheres for building materials, comprising: a microcapsule body with a repair agent as the core and a semi-interpenetrating network hydrogel material as the shell;

[0008] The shell surface is inlaid with volcanic ash material, which is used to react with the cement matrix to achieve the riveting of the two.

[0009] The microspheres in this invention can achieve self-riveting in a cementitious matrix. Specifically, during the mixing of the cementitious matrix or concrete, the shell of the microsphere rapidly absorbs water and swells, encapsulating some of the pozzolanic material within the hydrogel. Simultaneously, the unencapsulated pozzolanic material, evenly distributed in a "rivet" pattern on its surface, undergoes a pozzolanic reaction with the hydration products (calcium hydroxide) gradually generated in the mixing system, forming a tight bond. This is accompanied by volume expansion, thus achieving "self-riveting" of the microspheres within the cementitious matrix or concrete mix. After the cementitious matrix or concrete mix hardens, the microspheres lose water and shrink in volume, gradually exposing the pozzolanic material encapsulated in the hydrogel during the mixing stage. The water released from the hydrogel continues to undergo hydration reactions, producing hydration products (calcium hydroxide), and continues the pozzolanic reaction. The volume continues to expand, not only reinforcing the self-rivetized structure at the interface between the microspheres and the cement matrix, but also filling the pores created by the shrinkage of the microspheres with the cement hydration products, further strengthening the self-rivetized structure and enhancing the interfacial bonding between the microspheres and the matrix. When the microspheres of this invention are used as a self-healing material in cement or concrete, the hydration reaction of cement clinker releases calcium hydroxide, which then reacts with the pozzolanic material. These two reactions alternate and are mutually conditional and restrictive, thereby improving the volume stability and density of the cement or concrete, and exhibiting high responsiveness and high self-healing efficiency to microcracks in the cement matrix.

[0010] When cracks appear in cement or concrete, the microspheres are triggered by the cracks and break. The repair agent inside the microspheres flows out and bonds to repair the cracks. When the repair agent is an adhesive, it also slows down the water absorption rate of the hydrogel and reduces the water absorption and swelling rate, thereby reducing the volume change caused by swelling and shrinkage.

[0011] Preferably, the volcanic ash material is uniformly embedded in the outer surface of the shell.

[0012] Preferably, in the microspheres for building materials provided by the present invention, the volcanic ash material is also uniformly distributed in the semi-interpenetrating network hydrogel material.

[0013] The microspheres for building materials provided by the present invention are, in which the semi-interpenetrating network hydrogel material is one or more of sodium polyacrylate, acrylic acid-acrylamide copolymer and alginate hydrogel material; preferably, an alginate hydrogel material.

[0014] Preferably, in the microspheres for building materials provided by the present invention, the repair agent is a curable polymer resin adhesive, preferably one or more of epoxy resin, silicone resin, urea-formaldehyde resin, phenolic resin and unsaturated polyester resin, and more preferably epoxy resin.

[0015] Preferably, in the microspheres for building materials provided by the present invention, the volcanic ash material is one or more selected from volcanic ash, silica fume, fly ash, attapulgite, and kaolin, and more preferably one or more selected from volcanic ash, silica fume, and fly ash;

[0016] The particle size distribution of the volcanic ash material is less than 5 μm.

[0017] Silica fume possesses strong pozzolanic properties. When incorporated into cementitious materials, it first forms a silica-rich gel upon contact with mixing water, absorbing moisture. This gel aggregates between unhydrated cement particles, gradually encapsulating them. Calcium hydroxide reacts with the surface of this silica-rich gel to produce hydrated calcium silicate gel within the pores, significantly increasing structural density. In other words, the pozzolanic effect of silica fume can transform calcium hydroxide, which is detrimental to strength, into hydrated calcium silicate gel, filling the spaces between cement hydration products. Simultaneously, the reaction between silica fume and calcium hydroxide continuously consumes calcium hydroxide, accelerating the cement hydration rate.

[0018] For fly ash, its active components are amorphous aluminosilicates formed from clay minerals at high temperatures, namely soluble silica and alumina in the vitreous body. Under hydrothermal treatment in the presence of lime and gypsum, these undergo a series of physicochemical reactions to generate colloidal, filamentous, fibrous, and needle-like hydrated calcium silicate. These products intertwine and are bound together by the reacted vitreous body to form a composite, giving the product strength and other mechanical properties. Specifically, the silicates and aluminates in fly ash combine with hydroxide particles in water to form products such as isothermal calcium silicate and calcium aluminate. These products can fill the pores in concrete, improving its density and strength.

[0019] The volcanic ash reaction of the above-mentioned substances alters the pore structure of the slurry to a certain extent. Specifically, it reduces macropores, increases micropores, and makes the pore size finer. It also reduces the amount of calcium hydroxide in the slurry, refines the crystals, and makes the interface denser. This increases the adhesion between the microspheres used in building materials and the matrix interface, thereby changing the distribution pattern of the interface transition zone.

[0020] The present invention also provides a method for preparing microspheres for building materials as described above, comprising:

[0021] A suspension was obtained by premixing volcanic ash material with water;

[0022] The semi-interpenetrating network hydrogel precursor was added to the suspension and mixed to obtain the first mixture;

[0023] The first mixture, the repair agent, and the emulsifier are mixed to obtain a second mixture;

[0024] The second mixture was cross-linked and cured using a sharp-hole coagulation bath method to obtain the microspheres for building materials.

[0025] The experiment revealed that the order in which raw materials such as pozzolanic material and semi-interpenetrating network hydrogel prepolymer are added plays a crucial role in the successful preparation of the microspheres for the building materials. The pozzolanic material in this invention is a powder structure, and the stable existence of the "self-riveting" structure formed between it and the cement matrix is ​​largely related to the interaction force between it and the shell of the semi-interpenetrating network hydrogel material. Through the above preparation method, the pozzolanic material can be stably and densely dispersed on the shell surface of the semi-interpenetrating network hydrogel material through the adsorption effect and intermolecular forces of the semi-interpenetrating network hydrogel material, thereby achieving the stable existence of the "self-riveting" structure formed between it and the cement matrix.

[0026] Preferably, the method for preparing microspheres for building materials according to the present invention includes:

[0027] A suspension was obtained by stirring volcanic ash material and water at 15–25°C and 300–600 r / min for 10–30 min.

[0028] The semi-interpenetrating network hydrogel precursor was added to the suspension and stirred for 30-80 minutes at 55-65°C and 300-600 r / min to obtain the first mixture;

[0029] The first mixture, the repair agent, and the emulsifier are stirred at 55–65°C and 300–600 r / min for 30–80 min to obtain the second mixture;

[0030] The second mixture is added to the coagulation liquid in droplet form for cross-linking and curing, and then washed and dried to obtain the microspheres for building materials.

[0031] As the ternary microspheres are washed and dried, the semi-interpenetrating network hydrogel in the ternary microspheres loses water and shrinks, gradually exposing the volcanic ash material, which exhibits a "rivet"-like structure in the submicroscopic level. Washing typically involves using alcohol or acetone.

[0032] Semi-interpenetrating network hydrogel precursors typically require uniform dissolution at higher temperatures to achieve the preparation of the core-shell structure. If volcanic ash material is directly added to water along with the semi-interpenetrating network hydrogel precursor at this higher temperature, it will cause the volcanic ash material to aggregate, which will have a certain negative impact on the stability of the "self-riveting" structure formed between the microspheres and the cement matrix. It will also increase the construction difficulty of the sharp-pore-coagulation bath method, specifically causing pore blockage during the formation of droplets.

[0033] Preferably, in the method for preparing microspheres for building materials provided by the present invention, the concentration of volcanic ash material in the suspension is 0.0008 g / mL to 0.0525 g / mL;

[0034] And / or, the mass ratio of the pozzolanic material to the semi-interpenetrating network hydrogel precursor in the first mixture is 1:20 to 1.5:1; preferably, the concentration of the semi-interpenetrating network hydrogel precursor in the first mixture is 0.015 g / mL to 0.035 g / mL;

[0035] And / or, the mass ratio of the semi-interpenetrating network hydrogel precursor to the repair agent in the second mixture is 1:5 to 1:10;

[0036] And / or, the concentration of the crosslinking agent in the coagulation solution is 0.01–0.03 g / mL;

[0037] And / or, the mass ratio of the second mixture to the coagulated liquid is 1.5:1 to 10:1.

[0038] Preferably, in the method for preparing microspheres for building materials provided by the present invention, the emulsifier is sodium dodecylbenzenesulfonate;

[0039] Preferably, the amount of emulsifier added to the second mixture is 0.5 to 2.5 wt% of the repair agent.

[0040] The present invention also provides the application of the microspheres for building materials as described above, wherein the microspheres for building materials are added to the cement or concrete mixing system during mixing.

[0041] The microspheres for building materials of the present invention can maintain a tight bond with the interface during the hardening process of cement or concrete, thereby significantly improving the interfacial bonding strength and increasing the flexural and compressive strength of the resulting specimens. In particular, compared with microspheres without the addition of pozzolanic materials, the bonding strength between the microspheres of the present invention and the interface is increased by more than 90%. Moreover, the microspheres of the present invention have excellent repair properties for cement or concrete materials, with a permeability pressure recovery rate of more than 115% and a compressive strength recovery rate of more than 100%.

[0042] This invention provides an organic-inorganic composite ternary microsphere capable of self-riveting in a cement matrix, its preparation and application, and its beneficial effects include at least the following:

[0043] (1) By using microspheres for building materials with a "rivet" structure, the advantages of water-absorbing microcapsules are retained on the one hand; on the other hand, the volcanic ash reaction and expansion of the volcanic ash material that is evenly distributed in the shape of "rivets" are utilized to successfully construct a self-rivetized structure between the microspheres and the cement matrix, which solves the problem of poor interfacial bonding caused by the water loss and shrinkage of the hydrogel that serves as the shell of the water-absorbing microcapsule, making it difficult to fully exert the self-repair efficiency.

[0044] (2) Microspheres for building materials with a “rivet” structure have water absorption swelling-water loss shrinkage characteristics, which can provide “internal curing” for cement matrix, inhibit early cracking and drying shrinkage of cement matrix; after water absorption swelling, they can seal cracks and promote self-repair of cement matrix.

[0045] (3) The adhesive in the microspheres for building materials will not only flow out to bond and repair the cracks after the microspheres are mechanically triggered to break, thus improving the self-healing efficiency, but also slow down the water absorption rate of the semi-interpenetrating network hydrogel, reduce the water absorption swelling rate, and reduce the interfacial voids caused by water loss and shrinkage.

[0046] (4) Microspheres for building materials combine inorganic volcanic ash materials with organic semi-interpenetrating network hydrogels and adhesives. The mechanical strength is higher than that of ordinary microcapsules, which can prevent the microspheres from breaking during cement mixing. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 A schematic diagram of the structure of the organic-inorganic composite ternary microspheres that can achieve self-riveting in a cement matrix, provided by the present invention;

[0049] Figure 2 The results are the interfacial bond strength test results between GH-100 prepared in Example 3 and the cement matrix;

[0050] Figure 3 The results are the test results of the impermeability recovery performance of GH-100 prepared in Example 3 and the cement matrix;

[0051] Figure 4 The results are the compressive strength recovery performance test results of FMH-100 prepared in Example 4 and the cement matrix;

[0052] Figure 5 The results of the flexural strength test of GH-100 prepared in Example 3 and the cement matrix are shown.

[0053] Figure 6 The results are the compressive strength test results of GH-100 prepared in Example 3 and the cement matrix. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0055] The following is combined with Figures 1-6 This invention describes an organic-inorganic composite ternary microsphere capable of self-riveting in a cement matrix, its preparation, and its application.

[0056] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0057] Example 1: Preparation of microspheres GH-5

[0058] A method for preparing microspheres for building materials, comprising the following steps:

[0059] (1) A suspension was obtained by stirring volcanic ash material (silica fume with a particle size distribution of less than 2.6 μm) and water at 20 °C and 400 r / min for 15 min; wherein the concentration of silica fume in the suspension was 0.0008 g / mL.

[0060] (2) Add the semi-interpenetrating network hydrogel precursor (solid sodium alginate) to the suspension obtained in step (1) and stir for 60 min at 60°C and 400 r / min to obtain the first mixture; wherein the mass ratio of silica fume to sodium alginate in the first mixture is 1:20.

[0061] (3) The first mixture obtained in step (2), the repair agent (adhesive E-51 bisphenol A type epoxy resin) and the emulsifier (sodium dodecylbenzene sulfonate) are stirred at 60°C and 400 r / min for 60 min to obtain the second mixture; wherein, the mass ratio of sodium alginate solid to repair agent in the second mixture is 1:7.5; and the amount of emulsifier added in the second mixture is 1.5 wt% of the mass of repair agent.

[0062] (4) The second mixture obtained in step (3) is added in droplet form to the coagulation solution formed by calcium chloride through a disposable syringe and a medical 25G needle tip, and allowed to stand for 3 hours to crosslink and solidify. The concentration of calcium chloride in the coagulation solution is 0.024 g / mL; the mass ratio of the second mixture to the coagulation solution is 5:1.

[0063] (5) Pour off the upper layer of solidified liquid from the mixture obtained in step (4), soak the microspheres in anhydrous ethanol and ultrasonically clean them three times after solidification and molding, dry them in a 40°C forced-air drying oven for 48 hours, and then take them out to obtain microspheres for building materials.

[0064] The microspheres used in the obtained building materials are designated as GH-5. Figure 1 As shown, the microspheres for building materials are microcapsule bodies with a repair agent as the core and a semi-interpenetrating network hydrogel material as the shell; the surface of the shell is uniformly inlaid with volcanic ash material, and the volcanic ash material is used to react with the cement matrix to achieve the bonding between the two. At the same time, the volcanic ash material is also uniformly distributed in the semi-interpenetrating network hydrogel material.

[0065] Tests showed that GH-5 has an average particle size of 1.25 mm, with a silica fume content of 3.97% and an adhesive content of 49%.

[0066] Example 2: Preparation of microspheres FMH-10

[0067] The process is essentially the same as in Example 1, except that silica fume is replaced with fly ash with a particle size distribution of less than 5 μm, and the mass ratio of fly ash to sodium alginate solid in the first mixture is 10:1. The resulting microspheres for building materials are designated FMH-10. Testing showed that FMH-10 has an average particle size of 1.31 mm, with a fly ash content of 22% and a binder content of 40%.

[0068] Example 3: Preparation of microspheres GH-100

[0069] The process is essentially the same as in Example 1, except that the concentration of silica fume in the suspension in step (1) is increased to 0.016 g / mL. The obtained microspheres for building materials are designated GH-100. Testing showed that the average particle size of GH-100 was 1.46 mm, with a silica fume content of 13.69% and an adhesive content of 52%.

[0070] Example 4: Preparation of microspheres FMH-100

[0071] The process is essentially the same as in Example 2, except that the concentration of fly ash in the suspension in step (1) is increased to 0.016 g / mL. The obtained microspheres for building materials are designated FMH-100. Testing showed that the average particle size of FMH-100 was 1.32 mm, with a fly ash content of 17.48% and a binder content of 48%.

[0072] Comparative Example 1

[0073] The process is essentially the same as in Example 1, except that step (1) is omitted, and in step (2), a semi-interpenetrating network hydrogel precursor (solid sodium alginate) is added to water to obtain a first mixture, the content of sodium alginate in the first mixture being the same as in Example 1. The obtained microspheres for building materials are denoted as MC. Testing showed that the average particle size of MC was 1.26 mm, and the binder content was 64.9%.

[0074] Experimental Example 1: Test of the interfacial bonding between microspheres and the matrix

[0075] Weigh 1000g of bonding mortar and 250g of water, and mix them. Fill half of the mold (50mm×50mm×50mm) with the mixed bonding mortar, level it using a vibrating table, and evenly sprinkle 1.2g of the microspheres to be tested onto the surface. Then fill the mold completely with bonding mortar. After casting, cure the specimen under standard curing conditions (relative humidity above 95%, temperature 20℃±2℃) for 24 hours. After curing, remove the mold and continue standard curing for 28 days. Prepare 6 specimens using this method, and test their tensile strength using a universal tensile testing machine. The average value of the 6 specimens is used as the characterization of the interfacial bonding strength.

[0076] GH-100 (prepared in Example 3) and MC (prepared in Comparative Example 1) were used as microspheres for the above tests. The test results are as follows: Figure 2 As shown, the interfacial bond strength of MC is 0.418 MPa, and that of GH-100 is 0.814 MPa. It can be seen that the interfacial bond strength of microsphere GH-100 is significantly higher than that of the water-absorbing microcapsule (MC) without the "rivet" structure. This indicates that the self-rivetized structure greatly enhances the interfacial bonding between the microspheres and the matrix.

[0077] Experiment Example 2: Self-healing performance test

[0078] Preparation method of cement mortar specimens: Weigh 450g of ordinary Portland cement and 225g of water, and mechanically mix for 60s at low speed (60rpm) with a mixing paddle. Continue mixing for another 60s, uniformly adding 1350g of standard sand. Then, add the microspheres to be tested at 4% of the cement mass and the binder / curing agent tetraethylenepentamine at 15% of the microsphere mass, and continue mixing for 120s. Pour the mixed cement into a mold (40mm×40mm×160mm). After casting, cure the specimens under standard curing conditions (relative humidity above 95%, temperature 20℃±2℃) for 24 hours. After curing, remove the mold and cure under standard conditions for 28 days to obtain cement mortar specimens.

[0079] (1) Several specimens were prepared by using GH-100 (prepared in Example 3) and MC (prepared in Comparative Example 1) as microspheres to be tested according to the above method, and used for testing the water pressure damage resistance and self-healing performance of mortar.

[0080] Cement mortar specimens were cured for 28 days before the first impermeability pressure test was conducted, and the pressure at which seepage occurred in each specimen was recorded. The test was stopped when all six specimens showed signs of seepage. The pressure at which seepage occurred in the third specimen was reduced by 0.1 MPa and recorded as the first impermeability pressure of the reference mortar or the tested mortar. The six reference mortar and tested mortar specimens that showed signs of seepage were placed in a standard curing room (20℃, RH=95%±5%) for 14 days, and then the specimens were removed for a second impermeability test. The pressure at which seepage occurred in the third specimen was reduced by 0.1 MPa and recorded as the second impermeability pressure of the reference mortar or the tested mortar. The ratio of the second impermeability pressure to the first impermeability pressure was recorded as the impermeability pressure recovery rate. The test results are as follows: Figure 3 As shown, the specific data is shown in the table below:

[0081] Table 1

[0082]

[0083] from Figure 3As shown in the table above, the addition of GH-100 has an excellent repair effect on the impermeability of mortar specimens after water pressure penetration. Compared with the control group mortar specimens (without microspheres), its impermeability recovery rate increased by 54%, and compared with the mortar specimens containing MC, its impermeability recovery rate increased by 15%. This indicates that the organic-inorganic composite ternary microspheres can effectively repair water pressure damage in the mortar matrix and restore the impermeability of mortar specimens after water pressure penetration. This demonstrates that the self-riveting structure of the organic-inorganic composite ternary microspheres successfully enhances the bonding effect with the matrix and improves the impermeability recovery rate of cement mortar specimens.

[0084] (2) Using FMH-100 (prepared in Example 4) as the microspheres to be tested, several specimens were made according to the above method for testing the self-healing performance of compressive strength.

[0085] During testing, at 40% f max (f max A preload of 75 kN was set, and a force of 200 N / s was applied to reach the set preload. The pressure was held for 120 seconds and then unloaded. After 7 days of drying and curing, the compressive strength was tested again. The ratio of the compressive strength after preloading and repair to the compressive strength without preloading was taken as the compressive strength recovery rate. The test results are as follows: Figure 4 As shown, the compressive strength of the control group mortar specimen (without microspheres) without preloading was 44.33 MPa, and the compressive strength after preloading and repair was 42.66 MPa, with a compressive strength recovery rate of 96%. The compressive strength of FMH-100 without preloading was 48.73 MPa, and the compressive strength after preloading and repair was 52.39 MPa, with a compressive strength recovery rate of 107%. It can be seen that when the preload is 40%... max In the case of cement mortar specimens with added microspheres (FMH-100), the compressive strength after repair was higher than that of the uncompressed specimens. This indicates that the organic-inorganic composite ternary microspheres can effectively repair cracks in the matrix and restore and enhance the compressive strength of the matrix. The compressive strength of the cement mortar specimens with added microspheres was higher than that of the control group before and after preloading, and the recovery rate was 11% higher than that of the blank group. This indicates that the self-riveting structure of the organic-inorganic composite ternary microspheres successfully enhances the bonding effect with the matrix and improves the self-repair efficiency of the cement mortar's compressive strength.

[0086] Experiment 3 Interface bonding performance test

[0087] Weigh 450g of ordinary Portland cement and 225g of water, and mechanically mix for 60s at low speed (60rpm) with a mixing paddle. Continue mixing for another 60s, uniformly adding 1350g of standard sand. Then, add the microspheres to be tested at 4% of the cement mass and the binder / curing agent tetraethylenepentamine at 15% of the microsphere mass, and continue mixing for 120s. Pour the freshly mixed cement into a mold (40mm×40mm×160mm). After casting, cure the specimens under standard curing conditions (relative humidity above 95%, temperature 20℃±2℃) for 24 hours. After curing, remove the mold and cure under standard conditions for 3d, 7d, and 28d, and test the strength of the cement mortar specimens at each age.

[0088] Several specimens were prepared using GH-100 (obtained in Example 3) as the microspheres to be tested, and the above tests were performed. The test results are as follows. Figures 5-6 As shown, the specific data is shown in the table below:

[0089] Table 2

[0090]

[0091] Table 3

[0092]

[0093] from Figures 5-6 As shown in the table above, the 7-day and 28-day flexural and compressive strengths of the mortar samples with added microspheres (GH-100) were improved compared to the control group without microspheres. This indicates that the organic-inorganic composite ternary microspheres are tightly bonded to the interface, and the reaction products of the "rivet" structured pozzolanic material fill the gaps left by the microspheres after water loss and shrinkage, improving the volume stability and density of the cement matrix and enhancing its mechanical properties.

[0094] In summary, this invention, through organic-inorganic composite design, creates self-riveting organic-inorganic composite ternary microspheres within a cement matrix, constructing a novel cement-based self-healing system with high volume stability. The surface of these organic-inorganic composite ternary microspheres is uniformly distributed and embedded with pozzolanic "rivets." These pozzolanic "rivets" react and expand, achieving "self-riveting" of the microspheres within the cement matrix. The microspheres exhibit a tight interface with the cement matrix, demonstrating high responsiveness and self-healing efficiency to microcracks generated within the cement matrix. Furthermore, the preparation process is simple, the microspheres possess certain mechanical strength, are easily dispersed in cement paste, and provide an "internal curing" effect, improving the volume stability and density of concrete.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of microsphere for building materials, characterized in that, include: The microcapsule body consists of a repair agent as the core and a semi-interpenetrating network hydrogel material as the shell; The shell surface is inlaid with volcanic ash material, which is also uniformly distributed in the semi-interpenetrating network hydrogel material; the volcanic ash material is used to react with the cement matrix to achieve the riveting of the two.

2. The microspheres for building materials according to claim 1, characterized in that, The semi-interpenetrating network hydrogel material is one or more of sodium polyacrylate, acrylic acid-acrylamide copolymer, and alginate hydrogel material.

3. The microspheres for building materials according to claim 1, characterized in that, The repair agent is a curable polymer resin adhesive.

4. The microspheres for building materials according to claim 3, characterized in that, The repair agent is one or more of epoxy resin, silicone resin, urea-formaldehyde resin, phenolic resin, and unsaturated polyester resin.

5. The microspheres for building materials according to claim 1, characterized in that, The volcanic ash material is one or more of the following: volcanic ash, silica fume, fly ash, attapulgite, and kaolin.

6. The microspheres for building materials according to claim 5, characterized in that, The particle size distribution of the volcanic ash material is less than 5 μm.

7. The method for preparing microspheres for building materials according to any one of claims 1 to 6, characterized in that, include: A suspension was obtained by premixing volcanic ash material with water; The semi-interpenetrating network hydrogel precursor was added to the suspension and mixed to obtain a first mixture; The first mixture, the repair agent, and the emulsifier are mixed to obtain a second mixture; The second mixture was cross-linked and cured using a sharp-hole coagulation bath method to obtain the microspheres for building materials.

8. The method for preparing microspheres for building materials according to claim 7, characterized in that, include: The volcanic ash material and water were stirred at 15-25℃ and 300-600 r / min for 10-30 min to obtain a suspension. The semi-interpenetrating network hydrogel precursor was added to the suspension and stirred for 30-80 minutes at 55-65°C and 300-600 r / min to obtain the first mixture; The first mixture, the repair agent, and the emulsifier are stirred at 55-65°C and 300-600 r / min for 30-80 min to obtain the second mixture; The second mixture is added to the coagulation liquid in droplet form for cross-linking and curing, and then washed and dried to obtain the microspheres for building materials.

9. The method for preparing microspheres for building materials according to claim 7 or 8, characterized in that, The concentration of volcanic ash material in the suspension is 0.0008 g / mL to 0.0525 g / mL; And / or, the mass ratio of pozzolanic material to semi-interpenetrating network hydrogel prepolymer in the first mixture is 1:20 to 1.5:1; And / or, the mass ratio of the semi-interpenetrating network hydrogel precursor to the repair agent in the second mixture is 1:5 to 1:10; And / or, the concentration of the crosslinking agent in the coagulation solution is 0.01~0.03 g / mL; And / or, the mass ratio of the second mixture to the coagulated liquid is 1.5:1 to 10:

1.

10. The method for preparing microspheres for building materials according to claim 9, characterized in that, The concentration of the semi-interpenetrating network hydrogel prepolymer in the first mixture is 0.015 g / mL to 0.035 g / mL.

11. The method for preparing microspheres for building materials according to any one of claims 7, 8, and 10, characterized in that, The emulsifier is sodium dodecylbenzenesulfonate.

12. The method for preparing microspheres for building materials according to claim 11, characterized in that, The amount of emulsifier added in the second mixture is 0.5 to 2.5 wt% of the repair agent.

13. The method for preparing microspheres for building materials according to claim 9, characterized in that, The emulsifier is sodium dodecylbenzenesulfonate.

14. The method for preparing microspheres for building materials according to claim 13, characterized in that, The amount of emulsifier added in the second mixture is 0.5 to 2.5 wt% of the repair agent.

15. The application of microspheres for building materials according to any one of claims 1 to 6, characterized in that, The building material is added to the cement or concrete mixing system using microspheres during the mixing process.

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