A high-flow-state crack-resistant ultra-high toughness cement-based composite material and its preparation method

Abstract

This invention discloses a high-flowability, crack-resistant, ultra-high toughness cement-based composite material and its preparation method. The composite material comprises fibers and the following components by weight: 18-28 parts fine sand, 15-20 parts cement, 20-30 parts fly ash, 12-15 parts micro-interface reinforcing agent, 2.8-3.2 parts composite expansion agent, 0.1-0.3 parts superplasticizer, and 15-18 parts water. Based on the percentage of fiber volume in the total volume of the ultra-high toughness cement-based composite material, the fibers include: 1.0%-1.5% toughening fiber, 0.2%-0.7% reinforcing fiber, 0.15%-0.25% crack-resistant fiber A, and 0.07%-0.09% crack-resistant fiber B. The micro-interface reinforcing agent is a composite material of silica fume and attapulgite. The high-flowability, crack-resistant, ultra-high toughness cement-based composite material obtained by this invention exhibits excellent performance, with micro-expansion throughout the plastic and hardening stages of concrete, demonstrating excellent crack control performance.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-flow-state crack-resistant ultra-high toughness cement-based composite material and its preparation method. Background Technology

[0002] Ultra-High Toughness Cementitious Composite (UHTCC) is a new type of high-performance green building material. This material exhibits strain hardening and multi-crack characteristics, possessing ultra-high toughness, the ability to disperse cracks harmlessly, and excellent durability properties such as freeze-thaw resistance, impermeability, corrosion resistance, and carbonation resistance. Compared with other concrete materials, UHTCC has a significant advantage in tensile strain hardening capacity, with its direct tensile strain consistently reaching over 2%, and crack width controllable within 0.2 mm, fundamentally improving the quasi-brittle weakness of ordinary concrete materials.

[0003] Traditional cement-based materials develop wide cracks under load, while UHTCC structures exhibit only fine cracks in the tension zone as strain hardening continues. These micro-cracks prevent corrosion of the internal reinforcing steel, effectively improving the structure's safety and durability. However, UHTCC engineering applications still present the following problems: Firstly, to achieve significant strain hardening characteristics under tensile stress, 1.5%–2% by volume of micron-sized organic fibers are typically introduced. These fibers significantly degrade the fluidity and workability of the concrete mixture. Secondly, to improve the ductility and toughness of the UHTCC matrix, only fine silica sand is used as aggregate in the material system design, along with a large amount of cementitious materials. This material system exhibits significant early plastic shrinkage deformation, later drying shrinkage deformation, and the material's own shrinkage deformation. Under strong constraints such as reinforcing steel, this can easily lead to cracking in the concrete structure, affecting its structural load-bearing capacity and durability. To address the aforementioned issues, Chinese patents CN 117003518 A, CN 106478007 A, and CN 115534102 A all disclose methods for preparing ultra-high toughness cement-based composite materials. CN 115534102 A specifically addresses the problems of excessive dust and uneven mixing during the mixing process. CN 106478007 A improves the brittleness of the matrix by introducing a high proportion of polymer emulsion, thereby increasing the initial flexural stress and initial crack strain of the material. CN 117003518 A uses rubber to modify the ultra-high toughness cement-based composite material, reducing the fracture toughness of the matrix and thus improving the ductility of the material. While these patents provide some ideas and directions for the design and preparation of ultra-high toughness cement-based composite materials, none of them solve the problems of significant influence from material flowability and large shrinkage deformation. Summary of the Invention

[0004] Objective of the Invention: To address the problems existing in the prior art, the present invention aims to provide a high-flow-state, crack-resistant, ultra-high-toughness cement-based composite material and its preparation method. This composite material exhibits excellent performance, with micro-expansion throughout the plastic and hardening stages of concrete, demonstrating superior crack control properties.

[0005] Technical Solution: To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] A high-flowability, crack-resistant, ultra-high-toughness cement-based composite material, comprising fibers and the following components in parts by weight:

[0007] 18-28 parts fine sand, 15-20 parts cement, 20-30 parts fly ash, 12-15 parts micro-interface reinforcing agent, 2.8-3.2 parts composite expanding agent, 0.1-0.3 parts superplasticizer, and 15-18 parts water;

[0008] Based on the percentage of fiber volume in the total volume of the ultra-high toughness cement-based composite material, the fibers include: toughening fibers 1.0%~1.5%, reinforcing fibers 0.2%~0.7%, crack-resistant fiber A 0.15%~0.25%, and crack-resistant fiber B 0.07%~0.09%.

[0009] The micro-interface reinforcing agent is a composite material of silica fume and attapulgite.

[0010] In a specific implementation scheme, the toughening fiber is ultra-high molecular weight polyethylene fiber with a bulk density of 0.90-1.00 g / cm³. 3 Fiber length 12~18mm, monofilament diameter 20~25μm, tensile strength ≥3000MPa, elongation at break ≥3%;

[0011] The reinforcing fiber is copper-plated microfiber steel fiber with a bulk density of 7.5-8.0 g / cm³. 3 Fiber aspect ratio 60~85, tensile strength ≥2800MPa;

[0012] The crack-resistant fiber A is a lignin fiber with a bulk density of 1.1~1.3 g / cm³. 3 The fiber has a cotton-like appearance, is white or grayish-white, and has a moisture content of ≤2%.

[0013] The crack-resistant fiber B is a water-dispersible chopped glass fiber. This fiber can disperse into single fibers upon contact with water, with a single filament diameter of 14-16 μm, a zirconium oxide content of ≥16%, a water content of ≤0.6%, and a bulk density of 2.7 g / cm³. 3 .

[0014] As a specific implementation scheme, in the micro-interface reinforcing agent, silica fume SiO2 ≥ 92% with an average particle size of 0.1 ± 0.05; attapulgite is a powder particle with a particle size of 150-250 mesh.

[0015] As a specific implementation scheme, the mass ratio of silica fume to attapulgite in the micro-interface reinforcing agent is (1-3):1.

[0016] As a specific implementation plan:

[0017] The fine sand is quartz sand with a particle size of 40-140 mesh, a silica content of ≥98%, and a moisture content of ≤1%.

[0018] The cement is PII525 or PO525 silicate cement;

[0019] The fly ash is Grade I, with a loss on ignition ≤ 5.0%; fineness (residue on a 0.045mm square-hole sieve) ≤ 20%; water requirement ≤ 95%; and moisture content ≤ 1.0%.

[0020] The superplasticizer is a high-performance powdered polycarboxylate superplasticizer with a water reduction rate of ≥30% and a moisture content of ≤1%.

[0021] As a specific implementation scheme, the composite expanding agent is a mixture of plastic expanding agent, calcium expanding agent and magnesium expanding agent, with a mixing ratio of 1:8:8 to 1:10:10.

[0022] As a further option:

[0023] The plastic expanding agent is a mixture of p-nitrobenzene difluoroborate and iminodiacetonitrile in any proportion;

[0024] The calcium-based expanding agent is a mixture of free calcium oxide clinker, zeolite powder, fly ash, and bentonite in any proportion, and the free calcium oxide content in the calcium-based expanding agent is not less than 55%.

[0025] The magnesium-based expansion agent has an active reaction time of 90s to 200s, and the self-generated volume deformation of the concrete after shrinkage compensation is ≥0.015% after 7 days and ≥0.005% after 28 days.

[0026] This invention also provides a method for preparing the aforementioned high-fluidity, crack-resistant, ultra-high-toughness cement-based composite material, comprising the following steps:

[0027] (1) Weigh out fine sand, cement, fly ash, micro-interface reinforcing agent, composite expansion agent and superplasticizer according to the weight ratio and set aside;

[0028] (2) Put the weighed materials into the mixer for pre-dry mixing, then slowly add a portion of the water and continue mixing until the slurry has a good flow state.

[0029] (3) Add toughening fibers slowly in batches. After all the fibers have been added, continue stirring. During the addition process, ensure that the fibers that are in bundles are fully dispersed.

[0030] (4) After the toughening fibers are completely dispersed in the slurry, add the reinforcing fibers and stir.

[0031] (5) Add the crack-resistant fiber A and crack-resistant fiber B, along with the remaining amount of water, and stir quickly for 30-60 seconds to ensure that the fiber and slurry are mixed evenly without agglomeration. Then remove from the pot.

[0032] As a specific implementation plan, in step (2), the mixer is a vertical shaft planetary mixer.

[0033] As a specific implementation plan:

[0034] In step (2), the pre-dry mixing time is 1~2 minutes, then 4 / 5 of the water is slowly added, and the mixing time is continued for 4~5 minutes;

[0035] In step (3), the stirring time is 3-4 minutes;

[0036] In step (4), the time for adding reinforcing fibers and stirring is 2-3 minutes;

[0037] In step (5), the remaining water is 1 / 5 of the total water volume; the rapid stirring time is 30-60 seconds.

[0038] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0039] This invention abandons the conventional practice of using high-volume (1.5%~2.0%) hydrophilic polyvinyl alcohol fiber as toughening fiber in ultra-high toughness cement-based composites, replacing it with low-volume (1.0~1.5%) hydrophobic polyethylene fiber. Combined with superplasticizers and ultrafine sand, a high-toughness cement-based composite material with a large flowability can be obtained. To compensate for the potential reduction in material ductility and toughness caused by the use of hydrophobic fibers and the reduced fiber volume content, a micro-interface reinforcing agent is introduced to enhance the interfacial bonding performance between the fiber and the matrix. The silica fume in the micro-interface reinforcing agent is a micro / nano material; its extremely small particle size and large specific surface area can optimize the particle size distribution of the powder system and improve the slurry... The liquid has cohesive force and excellent ball bearing effect, which increases the free water content of the powder system, improves the density of the matrix, and improves the interfacial bonding between the matrix and the fiber. The attapulgite powder in the micro-interface reinforcing agent has a special rod-shaped microstructure. After being fully dispersed in the matrix, it can strengthen the overlap between the matrix and the fiber. The synergistic effect of silica fume and attapulgite powder can significantly improve the interfacial bonding strength between the fiber and the matrix. At the same time, the introduction of high-strength micro-copper-plated steel fibers further achieves the effect of matrix reinforcement and toughening. Moreover, the addition of steel fibers has almost no deterioration effect on the fresh mixing performance of the slurry. It can meet the requirement that high-toughness cement-based composite materials have significant strain hardening characteristics, and the ultimate tensile strain can be stably achieved at more than 2%.

[0040] To address the issues of high shrinkage and cracking in traditional ultra-high toughness cement-based composite materials, this invention employs a synergistic approach involving both the matrix and fibers. On the matrix side, a plastic expansion agent and a calcium-magnesium composite expansion agent are introduced to compensate for shrinkage. The plastic expansion agent reacts with the alkaline environment during cement hydration, slowly releasing gases (such as a mixture of nitrogen and acetylene) to form uniformly distributed bubbles. These bubbles continue to expand before the material hardens, compensating for shrinkage and reducing the risk of cracking in the high-toughness composite material. The calcium expansion agent primarily acts in the early stages of hardening after the high-toughness cement-based material has hardened, while the magnesium expansion agent acts in the middle and later stages. The coupled effect of these three agents significantly reduces the shrinkage deformation of the matrix itself. On the fiber side, wood fibers are incorporated... Cellulose fibers and water-dispersible chopped glass fibers are used as crack-resistant fibers. Cellulose fibers have a unique three-dimensional network structure, and their flat strip structure contains many capillary channels. These channels can guide the free water in the matrix to be evenly distributed, reducing matrix cracking. Water-dispersible chopped glass fibers have the characteristic of dispersing into single fibers when exposed to water. When these fibers are added together with some of the mixing water in the final stage of mixing, the dispersion effect of the fibers in the slurry can be significantly improved. At the same time, strict control of the mixing time can ensure that the fibers have a good dispersion effect without adversely affecting the fluidity of the slurry. The dispersed chopped glass fibers not only significantly improve the plasticity and crack resistance of high-toughness cement-based composite materials after hardening, but also have a positive effect on improving the toughness of high-toughness materials.

[0041] Using the above-mentioned technical means, a high-flow, crack-resistant, ultra-high toughness cement-based composite material can be prepared. This material has an initial expansion ≥450mm, a flexural strength ≥15MPa, an ultimate tensile strain ≥5%, and exhibits micro-expansion throughout the plastic and hardening stages of concrete, thus demonstrating excellent crack control performance. Attached Figure Description

[0042] Figure 1 The tensile stress-strain curves of the composite materials obtained in Examples 1-6 are shown.

[0043] Figure 2 The tensile stress-strain curves of the composite materials obtained in Comparative Examples 1 to 6 are shown. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Examples 1-6

[0046] The components and contents of each cement-based composite material are shown in Tables 1 and 2:

[0047] Table 1. Components and content (wt%) of cement-based composite powder system

[0048]

[0049] The cement used in Examples 1-6 above is PII525 silicate cement; the fine sand is 40-140 mesh quartz sand with a silica content ≥98% and a moisture content ≤1%; the fly ash is Grade I fly ash with a loss on ignition ≤5.0%, fineness (0.045mm square hole sieve residue) ≤20%, water requirement ≤95%, and moisture content ≤1.0%; the micro-interface reinforcing agent is a composite of silica fume and attapulgite in a 2:1 ratio, wherein the silica fume has SiO2 ≥92% and an average particle size of 0.1; the attapulgite is a powder with a particle size of 200 mesh; the composite expanding agent is a plastic expanding agent. The mixture comprises three components: calcium-based expansion agent, magnesium-based expansion agent, and plastic expansion agent. The plastic expansion agent is a mixture of p-nitrobenzene difluoroborate and iminodiacetonitrile. The calcium-based expansion agent is a mixture of free calcium oxide clinker, zeolite powder, fly ash, and bentonite, with a free calcium oxide content of not less than 55%. The magnesium-based expansion agent has an active reaction time of 90s to 200s, and its autogenous volume deformation after 7 days of concrete shrinkage compensation is ≥0.015%, and its autogenous volume deformation after 28 days is ≥0.005%. The superplasticizer is a high-performance powder polycarboxylate superplasticizer with a water reduction rate of ≥30% and a moisture content of ≤1%.

[0050] Table 2. Components and content (vol%) of the cement-based composite fiber system in Examples 1-6

[0051]

[0052] The toughening fiber in Examples 1-6 above is ultra-high molecular weight polyethylene fiber with a bulk density of 0.97 g / cm³. 3 The fiber length is 12mm, the monofilament diameter is 20μm, the tensile strength is 3100MPa, and the elongation at break is 3.5%; the reinforcing fiber is copper-plated microfiber steel fiber with a bulk density of 7.8g / cm³. 3 The fiber aspect ratio is 70, and the tensile strength is 2850 MPa; the crack-resistant fiber A is a lignin fiber with a bulk density of 1.2 g / cm³. 3 The fiber has a grayish-white, cotton-like appearance and a moisture content of 1.5%. Crack-resistant fiber B is a water-dispersible chopped glass fiber. This fiber disperses into single fibers upon contact with water, with a single filament diameter of 15 μm, a zirconium oxide content of 16.5%, a moisture content of 0.3%, and a bulk density of 2.7 g / cm³. 3 .

[0053] Table 3. Components and contents (wt%) of micro-interface reinforcing agents in Examples 1-6

[0054]

[0055] Table 4. Components and content (wt%) of the composite expanding agent in Examples 1-6

[0056]

[0057] Table 5. Components and contents (wt%) of the plastic expansion agent in Examples 1-6

[0058]

[0059] Table 6. Components and content (wt%) of calcium-based expanding agents in Examples 1-6

[0060]

[0061] To verify the superior performance of the cement-based composite material of the present invention, the following comparative experiments were conducted. These comparative experiments used the composition of the cement-based composite material in Example 3 as a baseline, with Comparative Examples 1-4 varying the composition and proportion of the fiber system; Comparative Examples 5-6 lacked the micro-interface reinforcing agent and the composite expanding agent, respectively, and the missing mass was added to the cement content. The corresponding compositions and contents of Comparative Examples 1-6 are shown in Tables 7 and 8.

[0062] Table 7. Components and contents (wt%) of cement-based composite powder systems in Comparative Examples 1-6

[0063]

[0064] Table 8. Components and content (vol%) of the cement-based composite fiber system in Comparative Examples 1-6

[0065]

[0066] The preparation methods of Examples 1-6 and Comparative Examples 1-6 are as follows:

[0067] (1) Use a mortar wetting mixer with the same mix ratio as the cement-based composite material, mix for 3 minutes and scrape off the excess mortar;

[0068] (2) Add fine sand, cement, fly ash, micro-interface strengthening agent, composite expansion agent and superplasticizer in sequence according to the feeding order and pre-dry mix for 1-2 minutes. The mixer is a vertical shaft planetary type. Then slowly add 4 / 5 of the water and continue mixing for 4-5 minutes until the slurry has a good flow state.

[0069] (3) Add toughening fibers slowly in batches. After all the fibers have been added, continue stirring for 3-4 minutes. During the addition process, ensure that the fibers in some bundles are fully dispersed. If necessary, a fiber disperser can be used.

[0070] (4) After the toughening fiber is completely dispersed in the slurry, add the reinforcing fiber and stir for 2-3 minutes;

[0071] (5) Add the crack-resistant fibers A and B and the remaining 1 / 5 of the water all at once, stir quickly for 30~60s to make the fibers and slurry mix evenly without agglomeration, and then remove from the pot.

[0072] (6) Pour the mixed ultra-high toughness cement-based composite material into a container, fill it at once, vibrate for 2 minutes, scrape the surface smooth, cover with a film for 24 hours and then remove the mold. Cure in a standard curing environment (temperature 20±2℃, humidity ≥95%) until the age to be tested and carry out performance testing.

[0073] The cement-based composite materials of Examples 1-6 and Comparative Examples 1-6 were tested for their scalar expansion, 28-day flexural strength, 28-day tensile strength, 28-day ultimate tensile strain, and autogenous volumetric deformation at 6 hours, 24 hours, and 28 days. The scalar expansion test method was based on GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the flexural strength test method was based on GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete", the tensile strength and ultimate tensile strain test methods were based on JC / T 2461-2018, and the autogenous volumetric deformation test method was based on GB / T 50082-2024.

[0074] The test results of various properties of cement-based composite materials are shown in Table 9.

[0075] Table 9 Test results of ultra-high toughness cement-based composite materials

[0076]

[0077] Note: Positive values ​​represent slight overall expansion, while negative values ​​represent overall contraction.

[0078] As can be seen from the data in Examples 1-6 in Table 9, the high-flow-state crack-resistant ultra-high toughness cement-based composite material provided by the present invention can meet the requirements of initial expansion ≥450mm, flexural strength ≥15MPa, ultimate tensile strain ≥5%, and micro-expansion throughout the plastic and hardening stages of concrete, exhibiting excellent crack control performance.

[0079] Comparing the test data of Comparative Examples 1-6 in Table 9 with the data of Example 3, it can be seen that the organic toughening fiber volume content in Comparative Example 1 is 1.8%. While the mechanical properties, ultimate tensile strain, and deformation properties of the high-toughness cement-based material are similar to those in Example 3, the high proportion of organic toughening fiber significantly reduces the spread of the fresh grout, affecting its workability. Comparative Example 2 lacks reinforcing fibers, which are copper-plated micro-steel fibers. The absence of these fibers reduces the overall fiber content of the material system, increasing the initial spread of the grout, but significantly deteriorates the mechanical properties. Simultaneously, the decrease in the total fiber content reduces the ultimate tensile strain to some extent, weakening the material's toughness. Comparative Examples 3 and 4 lack crack-resistant fibers A and B, respectively. The absence of crack-resistant fibers results in greater shrinkage deformation during the plastic stage (6h) of the high-toughness material, while the autogenous volume deformation during the hardening stage is reduced by more than 100 micro-strains compared to Example 3. Furthermore, the mechanical properties and ultimate tensile strain indicators also show a slight decrease. Comparative Example 5 lacked a micro-interface reinforcing agent. The micro-interface reinforcing agent primarily improves the bonding performance between the fiber and the interface, fully utilizing the bridging and reinforcing effects of the fiber. Without this substance, the ultimate tensile strain and flexural strength of the cement-based material decreased significantly. Comparative Example 6 lacked a composite expansive agent. The early and later autogenous volume deformation of the cement-based material were much lower than in Example 3. Simultaneously, the reduced volume stability of the material also affected its mechanical properties.

[0080] It is evident that the ultra-high toughness cement-based composite material of the present invention achieves high initial flowability, high crack resistance, excellent toughness and mechanical properties of high toughness cement-based material with low organic toughening fiber content through the synergistic effect of matrix design, fiber system design and fiber-matrix interface improvement. These components influence each other in combination rather than existing independently.

[0081] The embodiments of the present invention have been described in detail above with reference to specific examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A high-flowability, crack-resistant, ultra-high-toughness cement-based composite material, characterized in that, Includes fibers and the following components in parts by weight: The mixture comprises 18-28 parts fine sand, 15-20 parts cement, 20-30 parts fly ash, 12-15 parts micro-interface reinforcing agent, 2.8-3.2 parts composite expansive agent, 0.1-0.3 parts superplasticizer, and 15-18 parts water. The composite expansive agent is a mixture of plastic expansive agent, calcareous expansive agent, and magnesian expansive agent in a ratio of 1:8:8 to 1:10:

10. The calcareous expansive agent is a mixture of free calcium oxide clinker, zeolite powder, fly ash, and bentonite in any proportion, and the free calcium oxide content in the calcareous expansive agent is not less than 55%. Based on the percentage of fiber volume in the total volume of the ultra-high toughness cement-based composite material, the fibers include: toughening fibers 1.0%~1.5%, reinforcing fibers 0.2%~0.7%, crack-resistant fiber A 0.15%~0.25%, and crack-resistant fiber B 0.07%~0.09%. The toughening fiber is ultra-high molecular weight polyethylene fiber with a bulk density of 0.90-1.00 g / cm³. 3 Fiber length 12~18mm, monofilament diameter 20~25μm, tensile strength ≥3000MPa, elongation at break ≥3%; The reinforcing fiber is copper-plated microfiber steel fiber with a bulk density of 7.5-8.0 g / cm³. 3 Fiber aspect ratio 60~85, tensile strength ≥2800MPa; The crack-resistant fiber A is lignin fiber with a bulk density of 1.1~1.3 g / cm³. 3 The fiber has a cotton-like appearance, is white or grayish-white, and has a moisture content of ≤2%. The crack-resistant fiber B is a water-dispersible chopped glass fiber. This fiber can disperse into single fibers upon contact with water, with a single filament diameter of 14-16 μm, a zirconium oxide content of ≥16%, a water content of ≤0.6%, and a bulk density of 2.7 g / cm³. 3 ; The micro-interface reinforcing agent is a composite material of silica fume and attapulgite.

2. The high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 1, characterized in that, In the micro-interface reinforcing agent, silica fume (SiO2) ≥ 92% has an average particle size of 0.1 ± 0.05; attapulgite is a powder with a particle size of 150-250 mesh.

3. The high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 1, characterized in that, In the micro-interface reinforcing agent, the mass ratio of silica fume to attapulgite is (1-3):

1.

4. The high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 1, characterized in that, The fine sand is quartz sand with a particle size of 40-140 mesh, a silica content of ≥98%, and a moisture content of ≤1%. The cement is PII525 or PO525 silicate cement; The fly ash is Grade I, with a loss on ignition ≤ 5.0%; a residue of ≤ 20% on a 0.045mm square-hole sieve; a water requirement ratio ≤ 95%; and a moisture content ≤ 1.0%. The superplasticizer is a high-performance powdered polycarboxylate superplasticizer with a water reduction rate of ≥30% and a moisture content of ≤1%.

5. The high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 1, characterized in that, The plastic expanding agent is a mixture of p-nitrobenzene difluoroborate and iminodiacetonitrile in any proportion; The magnesium-based expansion agent has an active reaction time of 90s to 200s, and the self-generated volume deformation of the concrete after shrinkage compensation is ≥0.015% after 7 days and ≥0.005% after 28 days.

6. The method for preparing the high-flow-state crack-resistant ultra-high toughness cement-based composite material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Weigh out fine sand, cement, fly ash, micro-interface reinforcing agent, composite expansion agent and superplasticizer according to the weight ratio and set aside; (2) Put the weighed materials into the mixer for pre-dry mixing, then slowly add a portion of the water and continue mixing until the slurry has a good flow state. (3) Add toughening fibers slowly in batches. After all the fibers have been added, continue stirring. During the addition process, ensure that the fibers that are in bundles are fully dispersed. (4) After the toughening fibers are completely dispersed in the slurry, add the reinforcing fibers and stir. (5) Add the crack-resistant fiber A and crack-resistant fiber B, along with the remaining amount of water, and stir quickly for 30-60 seconds to ensure that the fiber and slurry are mixed evenly without agglomeration. Then remove from the pot.

7. The preparation method of the high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 6, characterized in that, In step (2), the mixer is a vertical shaft planetary mixer.

8. The preparation method of the high-flow-state crack-resistant ultra-high toughness cement-based composite material according to claim 6, characterized in that: In step (2), the pre-dry mixing time is 1~2 minutes, then 4 / 5 of the water is slowly added, and the mixing time is continued for 4~5 minutes; In step (3), the stirring time is 3-4 minutes; In step (4), the time for adding reinforcing fibers and stirring is 2-3 minutes; In step (5), the remaining amount of water is 1 / 5 of the total amount of water; the rapid stirring time is 30~60s.

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