A capsule-matrix self-healing material with high compatibility and preparation method thereof

Abstract

The present invention discloses a highly compatible capsule-matrix self-healing material and a preparation method thereof, and belongs to the technical field of engineering materials. The raw materials of the capsule-matrix self-healing material of the present invention are calculated by mass and include: 30 parts of carbide slag, 5 to 15 parts of phosphogypsum, 55 to 65 parts of blast furnace slag, and 45 parts of self-healing capsule material; the self-healing capsule material is composed of a capsule core and a capsule wall; the capsule core contains carbide slag, blast furnace slag and bentonite; the capsule wall contains quartz sand and epoxy resin. In the alkali-salt activated slag system of the present invention, carbide slag serves as an alkali activator, phosphogypsum serves as a salt activator, and blast furnace slag serves as a precursor; in order to maintain high material compatibility between the capsule core and the matrix, the capsule core contains a bentonite expander and an alkali-salt activated gelling system consistent with the matrix; the anhydrous capsule wall is prepared in collaboration with epoxy resin and quartz sand to enhance the bite force between the capsule wall and the matrix.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering materials, in particular to a capsule-matrix self-healing material with high compatibility and a preparation method thereof. Background Art

[0002] During their service life, cement-based and geopolymer materials inevitably develop microcracks due to external forces or shrinkage. Without timely intervention, these microcracks can gradually expand into wide or through-cracks, significantly weakening the durability of the structure. Crack self-healing technology, as an intelligent, active repair method, can inhibit the expansion of microcracks, thereby providing an effective crack barrier. Compared to traditional passive repair processes, it offers advantages such as a high degree of automation and significantly higher repair efficiency, making it a research hotspot in materials science.

[0003] Existing self-healing systems primarily involve mechanisms such as microbial-induced calcium carbonate precipitation, superabsorbent polymer (SAP) expansion, and hydration reactions of mineral expansive agents. However, the direct incorporation of these self-healing materials can easily lead to premature reaction between the matrix and the healing agent during the pre-embedding phase. To address this, encapsulation technology protects the healing agent through physical isolation, ensuring efficient activation of the healing agent upon crack initiation. Encapsulated self-healing materials retain high reactivity even after cracks appear, significantly enhancing crack healing. For example, encapsulating bacterial spores with low-alkalinity supersulfate cement can significantly increase crack healing rates. This is because the supersulfate cement capsule effectively protects the bacteria from the alkaline matrix during the pre-embedding process, maintaining bacterial activity. Protecting the expansive material is also necessary. Some researchers have experimented with encapsulating the expansive healing agent with epoxy resin and sand (or cement particles) to enhance crack closure. This prevents premature reaction between the self-healing material and water in the matrix, ensuring effective repair after crack initiation.

[0004] However, a good crack closure effect does not necessarily mean that the strength recovery of the cracked component is ideal. This is because the strength recovery effect depends on the adhesion between the healing product and the fracture surface, which is affected by the compatibility between the healing product and the matrix. Existing research focuses more on improving the self-healing behavior by improving the capsule; although optimizing the capsule core can effectively enhance the crack healing rate, the inconsistency between the capsule core material and the matrix material will reduce the compatibility between the healing product and the fracture surface, resulting in insufficient strength recovery. The main products of mineral expanders are magnesium compounds, which are chemically different from the silica-alumina hydrates of the matrix. This shows that improving the self-healing effect of the capsule alone will have limited effect on enhancing the adhesion between the healing product and the matrix at the fracture surface.

[0005] Existing research has proposed using cement clinker as a self-healing material to create a clinker capsule-matrix system. Due to the consistency between the self-healing material and the matrix, good self-healing results have been achieved. However, the high energy consumption of cement clinker conflicts with the goal of carbon neutrality, necessitating further research into alternative capsule-matrix systems. Expansive agents are key to achieving self-release from capsules. SAP, a commonly used organic material, poses potential environmental risks, necessitating alternative research directions. Summary of the Invention

[0006] The present invention aims to provide a highly compatible capsule-matrix self-healing material and its preparation method to address the problems described in the background art. The present invention designs a highly compatible capsule-matrix self-healing material that exhibits excellent strength, crack healing, and strength recovery properties, along with significant cost and carbon emission advantages, and has promising application value.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide a self-healing capsule material, which is composed of a capsule core and a capsule wall; the capsule core contains carbide slag, blast furnace slag and bentonite; the capsule wall contains quartz sand and epoxy resin;

[0009] The mass ratio of the carbide slag, blast furnace slag and bentonite is 15-30:55-65:5-15; the mass ratio of the quartz sand and epoxy resin is 100:13-19.

[0010] Preferably, the capsule core further contains phosphogypsum, and the mass ratio of the added amount of the phosphogypsum to the sum of the amounts of carbide slag and blast furnace slag is 1:4-17.

[0011] The second technical solution of the present invention is to provide a method for preparing the above-mentioned self-healing capsule material, comprising the following steps:

[0012] Grinding the raw materials, then mixing the ground raw materials for preparing the capsule core, adding water to granulate, and obtaining capsule core pellets;

[0013] The crushed raw materials for preparing the capsule wall are mixed and wrapped with capsule core balls to obtain the self-healing capsule material.

[0014] Preferably, the pulverization is pulverization to a median particle size of 10 to 70 μm.

[0015] Preferably, the amount of water added in the water granulation is 5-15% of the mass of the capsule core.

[0016] The third technical solution of the present invention is to provide a highly compatible capsule-matrix self-healing material, wherein the raw materials, calculated by weight, include:

[0017] 30 parts of carbide slag, 5-15 parts of phosphogypsum, 55-65 parts of blast furnace slag, 255 parts of quartz sand and 45 parts of the above-mentioned self-healing capsule material.

[0018] Preferably, the particle size of the self-healing capsule material is 2.36-4.75 mm.

[0019] A fourth technical solution of the present invention is to provide a method for preparing the above-mentioned highly compatible capsule-matrix self-healing material, comprising the following steps:

[0020] The raw materials are mixed, water is added, and curing is performed to obtain the capsule-matrix self-healing material with high compatibility.

[0021] Preferably, the ratio of the amount of water added to the total mass of carbide slag, phosphogypsum and blast furnace slag is 1:1.6~2.5.

[0022] The technical principles of the present invention are as follows:

[0023] Existing self-healing technologies primarily focus on improving capsule materials, neglecting the compatibility of the healing product with the matrix components. This results in poor adhesion of the healing product to the fracture surface, impairing the healing of the cracked matrix. To address this issue, the present invention proposes a novel alkali-salt-activated capsule-matrix self-healing material. Both the capsule and the matrix are constructed from cement-free clinker, offering the advantages of low carbon footprint and low cost. This capsule-matrix alkali-salt-activated composite material also exhibits excellent self-healing properties, particularly in terms of mechanical property recovery. After 90 days of healing, the maximum closed crack width ranged from 350 to 500 μm, and the minimum strength recovery rate was 85%. This is primarily due to the similarity between the self-healing material of the capsule core and the matrix material, resulting in a consistent composition of the self-healing product and the matrix hydration products. The high compatibility of new and old hydrates, such as calcium silicate hydrate (CSH) and ettringite (AFt), enhances the adhesion of the healing product to the fracture surface, promoting the recovery of self-healing properties.

[0024] The capsule material of this invention consists of a capsule core (carbide slag, phosphogypsum, blast furnace slag, and bentonite) and a capsule wall (quartz sand and epoxy resin). In the alkali-salt activated slag system of this invention, carbide slag serves as the alkali, phosphogypsum serves as the salt, and blast furnace slag serves as the precursor. To maintain high material compatibility between the capsule core and the substrate, the capsule core contains a bentonite expansion agent and an alkali-salt activated gelling system consistent with the substrate. The anhydrous capsule wall is prepared using epoxy resin and quartz sand to enhance the bond between the capsule wall and the substrate.

[0025] Because the capsules produced using the method defined in this invention are weaker than the substrate and sand, once the substrate cracks, the cracks extend in the direction of lowest strength and through the capsule, which is the prerequisite for the capsule's self-healing properties. Once the capsule ruptures, water from the surrounding environment enters the cracks. The bentonite absorbs the water, expands, and then transports the core material into the cracks, where it undergoes a healing reaction with the water, completing the crack repair.

[0026] During the healing process, carbide slag provides alkaline conditions and Ca 2+ , blast furnace slag provides a large amount of silicon and aluminum active components (such as SiO4 4- and AlO5 4- ), and then these components polymerize into CSH under alkali catalysis. Due to the rapid dissolution of active ions, the alkali salt activation system has the disadvantage of premature setting. The present invention adds phosphogypsum to slow setting, providing more time for the self-healing material to fill the cracks and preventing the self-healing material from hardening immediately after contact with water. In addition, phosphogypsum contains a large amount of calcium sulfate, which provides SO4 for the formation of AFt. 2- Ultimately, the generated healing product adhered to the fracture surface and hardened to adhere to the crack wall. Due to the consistency of the capsule-matrix material, a mixture of new and old CSH and AFt was formed at the fracture surface, similar to the clinker healing system, thus achieving a better repair effect.

[0027] The beneficial technical effects of the present invention are as follows:

[0028] The present invention designs a highly compatible capsule-matrix self-healing material, which has excellent strength, crack healing effect and strength recovery performance, and has obvious advantages in cost and carbon emissions, and has good application value.

[0029] The capsule-core healing product of the present invention consists primarily of CSH and AFt, which are consistent with the cementitious product of the matrix, resulting in a highly compatible self-healing mortar. The cracked sample of the present invention showed a minimum strength recovery rate of 85% after 90 days of healing, demonstrating excellent interfacial adhesion at the fracture surface. The capsule-matrix self-healing material developed by the present invention offers a novel approach to addressing the compatibility issues between self-healing products and matrix products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1The characterization data of the raw materials used in the present invention are shown in Figure 1. Wherein, a is the X-ray diffraction (XRD) spectrum, and b is the particle size distribution diagram.

[0032] Figure 2 The following are the characterization results of the capsules. (a) shows the microscopic morphology of the core of capsule A (i.e., the core pellet during preparation), (b) shows the microscopic morphology of the complete capsule A, (c) shows the scanning electron microscopy (SEM) image of the core, and (d) shows the EDS analysis of the core.

[0033] Figure 3 Figure 2 shows the crack evolution process of the product of Example 2 during the crack self-healing test. (a) shows the crack width after 0, 3, 7, 28, and 90 days of healing, and (b) shows the image and binarization of the crack in the capsule-matrix composite material after 0 and 90 days of healing.

[0034] Figure 4 The self-healing quantitative results of the crack width and area of ​​the product of Example 2. Wherein, a, b, c, and d are the initial crack width and the width after healing of composite materials A, B, C, and D, respectively, e is the quantitative result of the crack area, and f is the crack area healing rate.

[0035] Figure 5 The tensile strength recovery effect of the product of Example 2 during the crack self-healing test is shown in Figure 2. In this figure, a and b are the tensile stress-strain curves after 0 and 90 days of healing, respectively, and c is the tensile strength recovery rate.

[0036] Figure 6 The results of the analysis of the interface behavior between the healing product and the matrix at the crack are shown in Figure 1. (a, b, and c are SEM images of the healing product of capsules A, B, and C, respectively; d, e, and f are EDS images corresponding to a, b, and c, respectively; g is the XRD pattern of capsules A, B, and C; and h is the XRD pattern of composites A, B, C, and D.)

[0037] Figure 7 The nanoindentation test results of the fracture surface of composite material A after 90 days of healing are shown in Figure 1. (a) is the indentation micrograph, and (b) is the load-indentation depth curve.

[0038] Figure 8 Schematic diagram of crack self-healing of the capsule-matrix self-healing material of the present invention. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0040] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art in the art to which the present invention pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. It should be noted that any details not described herein are conventional procedures in the art and are not the focus of the present invention.

[0042] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0043] The raw materials used in the present invention include carbide slag, phosphogypsum, blast furnace slag, bentonite and quartz sand; these raw materials are characterized by XRD, laser particle size analyzer and XRF. These materials are processed by ball milling process and then used as raw materials; the ball milling time of these raw materials is 30-90 minutes, and the particle size results after ball milling are as follows: Figure 1 As shown in b.

[0044] Table 1 Chemical composition of raw materials

[0045]

[0046] Figure 1 The characterization data of the raw materials used in the present invention are shown in Figure 1. Wherein, a is the XRD spectrum and b is the particle size distribution diagram.

[0047] like Figure 1 As shown in a and Table 1, the main component of carbide slag is portlandite (CH), phosphogypsum contains a large amount of elemental calcium and sulfur, blast furnace slag is amorphous and rich in calcium, silicon and aluminum, the main component of bentonite is montmorillonite, which has the property of water absorption and expansion, and quartz sand mainly becomes quartz, which acts as fine aggregate.

[0048] Depend on Figure 1 As can be seen from b, the median particle sizes of the five materials are distributed between 10 and 70 μm, which is conducive to the contact and reaction between particles.

[0049] The epoxy resin used in the present invention was purchased from Kunshan Chemical Co., Ltd.

[0050] Example 1

[0051] A self-healing capsule material is prepared from carbide slag, phosphogypsum, blast furnace slag, bentonite, quartz sand and epoxy resin, and the formula is shown in Table 2.

[0052] Table 2 Capsule composition (mass fraction)

[0053]

[0054] The preparation method of this self-healing capsule material is as follows:

[0055] 1) Prepare the raw materials based on the core ratios listed in Table 2. Mix the solid waste materials in a mixing pot and dry-mix for 1 minute to obtain a dry material. Pour the dry material into the disc of a disc granulator (Model: ZL05, 50 cm diameter). The disc is tilted at 45° and rotated at a constant speed of 60 rpm. A prescribed amount of deionized water is then evenly sprayed onto the dry material, which is then rotated to promote granulation. This process ensures that sufficient unhydrated raw material remains after the core micro-granulation to allow for the self-healing reaction.

[0056] 2) After the capsule core is granulated, epoxy resin is evenly poured into the pellets to coat them. Once the resin completely covers the pellet surface, quartz sand is added to promote the formation of anhydrous capsule walls. To replace some fine aggregate with microcapsules during the subsequent embedment process, microcapsules with a particle size distribution of 2.36 to 4.75 mm are sieved and placed at 25°C to promote capsule wall hardening, resulting in a self-healing capsule material.

[0057] Example 2

[0058] A highly compatible capsule-matrix self-healing material, the formula of which is shown in Table 3.

[0059] Table 3 Composition of self-healing composite material substrate (mass fraction)

[0060]

[0061] The capsule-matrix self-healing composite material was prepared using a mixing kettle (model: NJ-160) based on the material composition shown in Table 3. To impart self-healing properties to the mortar, capsules were added at a rate equivalent to 15% of the quartz sand by weight to replace some of the quartz sand. The remaining preparation process was the same as for conventional composite materials. The specific steps were as follows: First, carbide slag, phosphogypsum, blast furnace slag, quartz sand, and capsules were dry-mixed for 1 minute. Deionized water was then added and stirred for 3 minutes. The mixed slurry was poured into a 40 mm × 40 mm × 160 mm mold and cured in a standard curing room (20 ± 1°C, relative humidity > 95%). The mold was then removed after 24 hours.

[0062] Effect verification

[0063] 1. Test Method

[0064] 1. Crack self-healing test

[0065] The two-point method was used to introduce cracks, and the maximum crack width was controlled by a displacement sensor to be within 600 μm. After the cracks were created, tape was used to seal the cracked sample to prevent further natural expansion. The crack healing effect was evaluated using local (width) and complete (area) evaluation methods. 50 points along the upper surface of the crack were marked with a marker pen, and the entire crack surface was photographed using a digital microscope (model: RoHS). The photography time was 0, 3, 7, 28, and 90 days after healing. The crack width at the marked points was measured using Photoshop software. The crack width healing rate was calculated using formula (1). The crack area healing was analyzed using ImageJ software. The threshold was adjusted to 0–155 so that only black and white colors were present in the image, which was used to distinguish the crack (black) from the matrix (white). The software automatically counted the pixels and obtained the crack area value. The area healing rate was calculated using formula (2).

[0066] R w = (w0-w t ) / w0 × 100% (1)

[0067] Where R w represents the crack width healing rate, w0 represents the initial crack width, w t Indicates the crack width at 90 days of healing.

[0068] R a = (a0-a t ) / a0 × 100% (2)

[0069] Where R a represents the crack area healing rate, a0 represents the initial crack area, a t It represents the crack area at 90 days of healing.

[0070] 2. Testing of capsules and their healing products

[0071] The capsule is the key to the performance advantages of the capsule-matrix self-healing material of the present invention. Therefore, the capsule and its healing product were subjected to microscopic and chemical analysis. The analysis methods mainly include SEM-EDS, FTIR, and XRD.

[0072] SEM-EDS analysis of the granulated capsule core material and healing products was performed using a Hitachi Regulus 8100 SEM instrument. The samples were cut into 2 cm × 2 cm × 5 cm sections, with test sizes of 5 μm and 20 μm. For FTIR and XRD analysis, the samples were ground to a powder size of less than 200 mesh. FTIR was used to analyze the chemical bonds in the capsule core material over a range of 400–4000 cm. -1 XRD instrument was used to analyze the phase of the healing product, with the test range of 5~55℃ and the test speed of 2° / min.

[0073] 3. Nanoindentation Measurement

[0074] Micromechanical testing was performed on the fracture surface of Composite Material A sample from Verification 2, 90 days after healing, using a nanoindenter (Hysitron TI 950). Due to the rough surface of the fracture surface, it was polished with epoxy resin before testing. Nanoindentation testing was performed on the healing product-matrix composite layer using a Berkovich indenter. A maximum load of 200 mN was applied, with loading and unloading times of 30 s each, a hold time of 5 s, and an acquisition frequency of 10 Hz. After testing, the indentation point was scanned using an atomic force microscope (AFM) to obtain the topography of the indentation location.

[0075] 2. Test Results

[0076] 1. Capsule Characterization

[0077] Figure 2 The characterization results of the capsules are shown in Figure 5. Figure a is the microscopic morphology of the core of capsule A (i.e., the core pellet during preparation), b is the microscopic morphology of the complete capsule A, c is the SEM image of the core, and d is the EDS image of the core.

[0078] exist Figure 2 During the test of a, it was found that due to the spraying of a small amount of water during the production process, the unencapsulated capsule core balls had weak cohesion. Figure 2 The black, anhydrous capsule wall in (b) is made of a mixture of quartz sand and epoxy resin, preventing water from entering the matrix. The intact capsule wall protects the self-healing material, preventing premature contact with water and the subsequent self-healing reaction. Figure 2 Figures c and d show the microstructure and elemental composition of the capsule core. SEM results indicate that a large number of unhydrated material particles remain in the capsule core, demonstrating that the capsule core retains the ability to rehydrate after granulation, enabling self-healing behavior. EDS analysis reveals an Al / Ca atomic ratio of 0.31 (less than 0.33) and a Si / Ca atomic ratio of 0.39 (outside the range of 0.4–0.7), indicating that only a small amount of CSH and AFt are present in the capsule core, while the unhydrated material predominates.

[0079] 2. Evaluation of crack self-healing performance

[0080] Figure 3 Figure 2 shows the crack evolution process of the product of Example 2 during the crack self-healing test. (a) shows the crack width after 0, 3, 7, 28, and 90 days of healing, and (b) shows the image and binarization of the crack in the capsule-matrix composite material after 0 and 90 days of healing.

[0081] Figure 3 The crack width evolution results of a show that the cracked alkali salt stimulates the matrix to gradually heal over time. After 28 days of healing of composite material A, a jet-like white product can be observed around the crack. This is because the bentonite in the capsule core absorbs water and expands, releasing self-healing materials. This proves that the capsule has a self-release function and can achieve self-healing behavior. After the cracked sample healed for 7 days, a large amount of white precipitate was observed on the surface of the sample. This is due to the carbonization of the matrix surface and water during the healing process. Overall, the four composite samples had obvious crack sealing effects after 28 days and 90 days of healing, which preliminarily showed that the capsule can achieve crack self-healing after the matrix cracks. In addition, the complete upper surface cracks were binarized to visualize the overall crack healing degree. The test results are shown in Figure 3 b; Comparing the binarization results, it can be clearly seen that the cracks in the sample are significantly reduced after 90 days of healing.

[0082] Figure 4 The self-healing quantitative results of the crack width and area of ​​the product of Example 2. Wherein, a, b, c, and d are the initial crack width and the width after healing of composite materials A, B, C, and D, respectively, e is the quantitative result of the crack area, and f is the crack area healing rate.

[0083] like Figure 4 As shown in Figures a, b, c, and d, the initial crack widths for all samples that were fully closed ranged from 100 to 500 μm. Further analysis of the data point distribution reveals that composites B, C, and D showed excellent crack repair, with closure rates ranging from 24% to 56%. However, composite A achieved a closure rate of only 16%. This result is related to the phosphogypsum content. Phosphogypsum has a retarding effect, so self-healing materials with low phosphogypsum content harden more quickly, resulting in a lower closure rate.

[0084] Figure 4 As can be seen in Figures e and f, the crack area gradually decreases with healing time, while the area healing rate gradually increases, consistent with the crack width healing pattern. Overall healing is poor between 3 and 7 days, with area healing rates below 30.03%. At 90 days, the area healing rates for all samples ranged from 46.15% to 73.06%, but this did not show a clear linear relationship with the sample ratio.

[0085] 3. Strength recovery effect

[0086] Figure 5 The tensile strength recovery effect of the product of Example 2 during the crack self-healing test is shown in Figure 2. In this figure, a and b are the tensile stress-strain curves after 0 and 90 days of healing, respectively, and c is the tensile strength recovery rate.

[0087] The strength recovery effect of the samples after the cracks were introduced in effect verification 2 was statistically analyzed. Strength recovery is an important indicator for evaluating the healing performance of cracked samples. Figure 5 The results showed that the lowest strength recovery rate for the four composite materials was 88.5%. This result is inconsistent with the crack width healing rate results, indicating that good surface crack closure does not necessarily mean good strength recovery in the cracked samples. This may be because poor healing of internal cracks can reduce strength recovery results. In addition, the crack self-healing effect depends on the number and location of capsules exposed at the fracture surface, resulting in a certain degree of discreteness in the recovery of tensile strength. After 90 days of healing, it was observed that all samples still failed brittlely, consistent with the failure mode of the pre-cracked samples. This is because the self-healing material in the capsules is similar to the matrix, and the product properties are consistent, resulting in the unchanged failure mode of the healed mortar.

[0088] 4. Micromorphology and Chemical Composition Analysis of Healing Products

[0089] Figure 6 The results of the analysis of the interface behavior between the healing product and the matrix at the crack are shown in Figures a, b, and c. The SEM images of the healing product at different locations of capsules A, B, and C are shown, respectively. The EDS images corresponding to a, b, and c are shown, respectively. The XRD patterns of capsules A, B, and C are shown in Figures g, h, and D.

[0090] Figure 6 a shows the microstructure of the healing products in the cracks, which are mainly needle-shaped and flocculent. Figure 6 The SEM test results are consistent with those in the Observation Figure 6 From b and c, it can be found that a large amount of CSH and AFt are attached to the inner wall of the crack, and these products effectively block the crack. Figure 6 The EDS results in d~f are respectively Figure 6 It can be observed that the atomic proportions of the elements at the crack wall are similar ( Figure 6 e~f); In contrast, the element ratios in the healing products of capsule A core changed, and the peak intensity decreased ( Figure 6d). Specifically, the Al / Ca atomic ratios of the crack wall components are 0.35 and 0.48, and the Si / Ca atomic ratios are 0.12 and 0.78. For the healing product itself, these atomic ratios are 0.15 and 0.13, respectively. Clearly, the composition at the crack wall is closer to the atomic ratios of CSH and AFt (Al / Ca atomic ratios of 0.33 and 0.5, and Si / Ca atomic ratios between 0.4 and 0.7). This result indicates that the crack wall is primarily composed of a mixture of hydration products from the matrix and healing products from the capsule. Both CSH and AFt products are formed during secondary hydration of the matrix and during the healing reaction of the capsule core, demonstrating the high compatibility of the healing product with the matrix at the interface transition zone.

[0091] Furthermore, the XRD analysis results of the healing product and the matrix are as follows Figure 6 As shown in g and h. By comparison, it can be found that the physical composition of the healing product and the matrix is ​​very similar, and peaks appear at the same diffraction angle. The phosphogypsum content in the capsule enhances the peak intensity of AFt, proving that phosphogypsum plays a key role in the generation of AFt. In the process of generating AFt, the CaSO4 in the phosphogypsum is gradually consumed, so the peak intensity of gypsum is inversely related to that of AFt, and this law is also observed in the matrix. Whether it is a capsule or a matrix, the peak width and peak intensity of calcium hydroxide in samples with different ratios are not significantly different. For the healing product, the peak of calcite at 29.4° is not obvious, and there is a peak there in the matrix. This may be because the healing product is exposed to the air for a short time, and Ca 2+ Has not yet been combined with CO3 in ambient water 2- These results demonstrate that the healing product has a high material similarity with the matrix.

[0092] 6. Nanoindentation test results

[0093] Figure 7 The nanoindentation test results of the fracture surface of composite material A after 90 days of healing are shown in Figure 1. (a) is the indentation micrograph, and (b) is the load-indentation depth curve.

[0094] The solid image of the indentation is as follows Figure 7 As shown in a, the position of the box in the figure represents the indentation. It can be seen that there is a small triangle with a darker color in the box, which is the mark left by the indenter, indicating that the indentation test result is correct. Figure 7 As shown in b, the P marked in the figure max, S refers to the maximum indenter load and stiffness. The trends of the four indentation curves all have the following three stages: the first stage is the pressure stage, the indentation depth increases with the load, and the curve shows an upward trend. When the load reaches the maximum load of 200mN, the curve enters the constant pressure stage (the second stage). Under the constant pressure state, the curve trend is horizontal for 5s, and then enters the pressure relief stage (the third stage). The indentation depth corresponding to the initial pressure relief stage is h max , and the indentation depth corresponding to the end of pressure relief is h c It should be noted that the curve did not rebound at the end of pressure relief, indicating that the composite layer of the healing product-matrix is ​​brittle.

[0095] The nanomechanical performance parameters obtained from the load and penetration depth curves are shown in Table 4.

[0096] Table 4 Nanomechanical performance parameters

[0097]

[0098] From Table 4, we can see that h c and h max The fluctuation of h is large, which is mainly affected by the loading rate. The thickness of the healing product on the crack surface that the sample contacts during the loading stage is inconsistent, which affects the slope of the pressure curve and thus significantly increases h. c The similarity of the slope of the unloading curves leads to a small fluctuation of the S value, which is distributed between 544.8 and 629.4 μN / nm. This indicates that the healing products CSH and AFt are well integrated with the fracture surface and can effectively resist external deformation. In addition, the Young's modulus (E r ) is distributed in the range of 17.2~33.3GPa, and the hardness (H) is distributed in the range of 0.19~0.71GPa. r It is closely related to the type of material and the degree of polymerization. The similarity between the healing product of the alkali-activated complex of the present invention and the matrix component enhances the E r Value. High E of the fault layer r The values ​​also indicate that the interfacial bonding between the new and old products (CSH and AFt) is strong, which also proves that the adhesion of the healing products on the fracture surface is strong.

[0099] 7. Self-healing mechanism of the capsule-matrix self-healing material of the present invention

[0100] Figure 8 Schematic diagram of crack self-healing of the capsule-matrix self-healing material of the present invention.

[0101] like Figure 8As shown, the quartz sand was replaced by an equal mass of capsules graded from 2.36 to 4.75 mm to create a composite. Because the capsules are weaker than the matrix and sand, once the matrix cracks, the cracks extend along the direction of lowest strength and through the capsules, which is the prerequisite for the capsules to self-heal. Once the capsules rupture, water from the environment enters the cracks. The bentonite absorbs the water, expands, and transports the capsule core material into the cracks. The self-healing material then reacts with the water to complete the crack repair.

[0102] During the healing process, carbide slag provides alkaline conditions and Ca 2+ , blast furnace slag provides a large amount of silicon and aluminum active components (such as SiO4 4- and AlO5 4- ), and then these components are polymerized into CSH under alkali catalysis. Phosphogypsum contains a large amount of calcium sulfate, which provides SO4 for the formation of AFt 2- Ultimately, the generated healing product adhered to the fracture surface and hardened to adhere to the crack wall. Due to the consistency of the capsule-matrix material, a mixture of new and old CSH and AFt was formed at the fracture surface, similar to the clinker healing system, thus achieving a better repair effect.

[0103] 8. Product advantages

[0104] Existing research on crack self-healing has focused more on improving the capsule. However, in some cases, optimizing only the self-healing material has limitations, especially in terms of material compatibility. The compatibility between the healing product and the matrix depends on the chemical composition, but the same composition does not necessarily mean that they are highly compatible. For example, the products of alkali-salt-activated self-healing materials and clinker matrices are both CSH and Aft, but they are generated by polymerization and hydration, respectively. The different reaction pathways lead to significant differences in the crystal density, microstructure, and number distribution of the products, reducing the compatibility of the healing product with the matrix. In addition, the reaction degree is difficult to reach 100%, whether for the self-healing material or the matrix. Residual silicon aluminum oxide and calcium sulfate in the alkali-activated material and residual C2S and C3S in the clinker will also reduce the compatibility of the healing product with the matrix.

[0105] Therefore, the consistency of the self-healing material and the matrix material is crucial. Therefore, the present invention has developed an alkali-salt-activated capsule-matrix material that is free of cement clinker and chemical reagents. This material uses all-solid waste materials to produce the capsule core and matrix, offering the advantages of low cost and reduced carbon emissions.

[0106] The mix ratio of the self-healing material (capsules) of this invention is similar to that of the matrix material, differing primarily in the presence or absence of bentonite. Although bentonite participates in the reaction, the inventors have found that its minimal addition primarily serves to expand the material and has little impact on the overall healing reaction. XRD analysis also shows that the phase composition of the capsule core product and the matrix product is consistent, demonstrating the high material compatibility of the self-healing mortar.

[0107] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A highly compatible capsule-matrix self-healing material, characterized in that: The raw materials are calculated by mass as follows: 30 parts of carbide slag, 5-15 parts of phosphogypsum, 55-65 parts of blast furnace slag, 255 parts of quartz sand and 45 parts of self-healing capsule material; The self-healing capsule material consists of a capsule core and a capsule wall; the capsule core contains carbide slag, blast furnace slag and bentonite; the capsule wall contains quartz sand and epoxy resin; The mass ratio of carbide slag, blast furnace slag and bentonite in the capsule core is 15-30:55-65:5-15; the mass ratio of quartz sand and epoxy resin in the capsule wall is 100:13-19; The capsule core also contains phosphogypsum, and the mass ratio of the added amount of the phosphogypsum to the sum of the amounts of carbide slag and blast furnace slag is 1:4-17.

2. The capsule-matrix self-healing material according to claim 1, characterized in that: The preparation method of the self-healing capsule material comprises the following steps: Grinding the raw materials, then mixing the ground raw materials for preparing the capsule core, adding water to granulate, and obtaining capsule core pellets; The crushed raw materials for preparing the capsule wall are mixed and wrapped with capsule core pellets to obtain the self-healing capsule material; The amount of water added in the water granulation is 5-15% of the mass of the capsule core.

3. The capsule-matrix self-healing material according to claim 2, characterized in that: The pulverization is to pulverize to a median particle size of 10 to 70 μm.

4. The capsule-matrix self-healing material according to claim 1, characterized in that: The particle size of the self-healing capsule material is 2.36-4.75 mm.

5. A method for preparing the highly compatible capsule-matrix self-healing material according to claim 1, characterized in that: The following steps are involved: The raw materials are mixed, water is added, and curing is performed to obtain the capsule-matrix self-healing material with high compatibility.

6. The preparation method according to claim 5, characterized in that The ratio of the mass of the water to the total mass of carbide slag, phosphogypsum and blast furnace slag is 1:1.6~2.5.

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