Concrete protection unit, preparation method, protection device and application

Abstract

The invention provides a concrete protection unit, a preparation method, a protection device and application, and relates to the technical field of protection engineering materials. The concrete protection unit is in the shape of a prism, the single top face of the prism is an elastic face, the prism comprises an undisturbed area, an energy absorption area, an anti-crack area and an anti-penetration area which are wrapped layer by layer from outside to inside, and the sections of the undisturbed area, the energy absorption area, the anti-crack area and the anti-penetration area are exposed on the elastic face respectively. By combining the cavity expansion theory and gradient concrete design, different areas in the concrete protection unit are subjected to differential optimization, so that when each area faces projectile bodies with different speeds and diameters, the penetration depth can be effectively reduced, and the impact resistance can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of protective engineering materials, and in particular to a concrete protective unit, a preparation method, and a protective device and application. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Traditional concrete target design mainly focuses on increasing hardness or thickness to resist the impact of projectiles, but this approach does not fully consider the interaction between the projectile and the target.

[0004] Based on cavity expansion theory, after a projectile enters a target, it forms multiple distinct zones along its path, including a cavity zone, a crushing zone, a cracking zone, an elastic zone, and an undisturbed area of ​​the target. Each zone exhibits distinct stress and failure characteristics, and a single design approach cannot effectively enhance these characteristics, thus failing to achieve optimal protection. Consequently, existing structural designs suffer from poor targeting and unclear protection layers, making them inadequate for projectile intrusion. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a concrete protection unit, a preparation method, a protection device and its application. By combining the cavity expansion theory with the prefabricated structural design, the different areas of the target body (such as the crushing area, the cracking area, the elastic area, etc.) are targetedly strengthened, thereby significantly improving the target body's resistance to penetration by projectiles of specific speed and diameter; by stacking modular units, the adaptability and construction efficiency of the target body are further improved, thereby achieving an efficient and economical protection effect.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions: A first aspect of the present invention provides a concrete protection unit in the shape of a prism, wherein a single top surface of the prism serves as a bullet impact surface, the prism comprising an undisturbed area, an energy absorption area, a crack resistant area, and an anti-penetration area, which are layered from the outside to the inside, and wherein the undisturbed area, the energy absorption area, the crack resistant area, and the anti-penetration area respectively expose cross sections of their areas on the bullet impact surface; The raw materials for preparing the undisturbed area, the energy absorption area, the anti-cracking area and the anti-penetration area respectively include: 360-520 parts of cement, 36-52 parts of silica fume, 36-52 parts of fly ash, 800-1000 parts of fine aggregate, 120-130 parts of water and 5-10 parts of high-efficiency water reducer; The raw materials for preparing the undisturbed area include 800-1000 parts of coarse aggregate; The raw materials for preparing the energy absorption region include 2-10 parts of foamed polypropylene particles, 1-5 parts of triethanolamine and 39-78 parts of basalt fibers; The raw materials for preparing the crack-resistant region include 156-312 parts of steel fiber and 39-78 parts of basalt fiber; The raw materials for preparing the anti-penetration area include 50-100 parts of epoxy resin, 10-30 parts of curing agent and block stone, and the ratio of the mass of the block stone to the sum of the mass of other raw materials for preparing the anti-penetration area is (10-15):(2-3).

[0007] In a second aspect, the method for preparing the above-mentioned concrete protection unit comprises the following steps: S1. Prepare a casting mold of a set shape, the mold including casting devices for an undisturbed area, an energy-absorbing area, an anti-cracking area, and an anti-penetration area; S2. Mixing the raw materials for the undisturbed area and then pouring the mixture to obtain an undisturbed area; S3, using triethanolamine in the raw materials for preparing the energy absorption region to modify the surface of the foamed polypropylene particles, then sprinkling cement to coat the outside of the foamed polypropylene particles to form a core-shell structure, and then mixing with other raw materials and pouring to obtain the energy absorption region; S4, mixing the raw materials for preparing the anti-cracking region and then pouring the mixture to obtain the anti-cracking region; S5. After uniformly mixing the epoxy resin and curing agent in the raw materials for preparing the anti-penetration area, other raw materials except the stone blocks are added and mixed to obtain a grouting material. The grouting material is used as an adhesive to bond the densely packed stone blocks into a whole to obtain the anti-penetration area, thereby obtaining a concrete protection unit.

[0008] In a third aspect, a protective device includes the above-mentioned concrete protective unit, wherein a plurality of concrete protective units are closely arranged and connected by an adhesive.

[0009] Fourthly, the application of the above-mentioned protective device in the field of building protection.

[0010] The beneficial effects of the present invention are as follows: 1. The present invention combines cavity expansion theory with gradient concrete design to perform differentiated optimization in different areas inside the concrete protection unit, so that each area can effectively reduce the penetration depth and improve the impact resistance when facing projectiles of different speeds and diameters. In particular, with the design of functions such as anti-penetration, anti-cracking and energy absorption, the protection performance of the target body is significantly improved, and it can cope with complex impact environments. By providing a three-dimensional coated anti-cracking area and an energy-absorbing area inside the protection unit, the target body can effectively resist crack propagation and effectively absorb and disperse energy when impacted. The toughness-reinforced material in the anti-cracking area effectively extends the service life of the target body, enabling it to maintain good structural stability and protection performance during long-term high-intensity use. 2. The protective device of this invention utilizes a modular stacking structure, making the target highly flexible and customizable. This modular design not only simplifies the construction process, improves efficiency, but also reduces maintenance costs. Damaged units can be replaced individually, avoiding large-scale dismantling and enhancing the long-term applicability and cost-effectiveness of the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0012] In order to show the positions of various parts, the distances or sizes between them are exaggerated in the figure, and the schematic diagram is for reference only.

[0013] Figure 1 It is a schematic diagram of the technical route in a specific implementation method.

[0014] Figure 2 This is a schematic diagram of the structure of the concrete protection unit in Example 1.

[0015] Figure 3 It is a schematic diagram of the cavity expansion theory in Example 1.

[0016] Figure 4 It is a structural diagram of the concrete protection unit in Example 1.

[0017] Among them, 1. Protective device; 2. Concrete protection unit; 21. Uninterrupted area; 22. Energy absorption area; 23. Anti-cracking area; 24. Anti-penetration area; 3. Bullet; 31. Uninterrupted area of ​​the target; 32. Elastic area; 33. Cracking area; 34. Crushing area. DETAILED DESCRIPTION

[0018] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0020] A concrete protection unit is shaped like a prism, wherein a single top surface of the prism is a bullet-impacting surface, the prism comprising an undisturbed area, an energy-absorbing area, a crack-resistant area, and a penetration-resistant area, which are layered from the outside to the inside, and wherein the cross-sections of the undisturbed area, the energy-absorbing area, the crack-resistant area, and the penetration-resistant area are respectively exposed on the bullet-impacting surface; The raw materials for preparing the undisturbed area, the energy absorption area, the anti-cracking area and the anti-penetration area respectively include: 360-520 parts of cement, 36-52 parts of silica fume, 36-52 parts of fly ash, 800-1000 parts of fine aggregate, 120-130 parts of water and 5-10 parts of high-efficiency water reducer; The raw materials for preparing the undisturbed area include 800-1000 parts of coarse aggregate; The raw materials for preparing the energy absorption region include 2-10 parts of foamed polypropylene particles, 1-5 parts of triethanolamine and 39-78 parts of basalt fibers; The raw materials for preparing the crack-resistant region include 156-312 parts of steel fiber and 39-78 parts of basalt fiber.

[0021] The raw materials for preparing the anti-penetration area include 50-100 parts of epoxy resin, 10-30 parts of curing agent and block stone, and the ratio of the mass of the block stone to the sum of the mass of other raw materials for preparing the anti-penetration area is (10-15):(2-3).

[0022] The above structure is designed based on cavity expansion theory, using a curved surface morphology to divide the target into an anti-penetration zone, a crack-resistant zone, an energy-absorbing zone, and an undisturbed zone. This gradient design significantly optimizes the target's structure, enhancing its comprehensive protection capabilities, including anti-penetration, crack-resistance, and energy-absorbing capabilities, ultimately reducing penetration depth.

[0023] Among them, the cement is 52.5 grade ordinary Portland cement with a specific surface area of ​​350~400m² / kg; Optionally, the mass percentage of silicon dioxide in the silica ash is not less than 97%, the pozzolanic activity index of the silica ash is greater than 95%, the specific surface area is greater than 21.0 m² / g, and the density is 2.20 g / cm³.

[0024] Optionally, the fly ash is Class I fly ash, with a loss on ignition of less than 3.0%, a specific surface area of ​​more than 1000 cm² / g, and main components including silicon oxide and aluminum oxide.

[0025] Optionally, the fine aggregate is natural river sand with a fineness modulus of 2.8 and a maximum particle size of 4.75 mm.

[0026] Optionally, the water reducing agent is a polycarboxylic acid water reducing agent with a water reduction rate of >30%.

[0027] Optionally, the block is one or more high-strength mineral blocks such as corundum block, basalt block, quartz sandstone block, etc., and its main components include minerals such as Al2O3, SiO2, Fe2O3, etc., and its particle size is 1.5 to 3 times that of the projectile.

[0028] Optionally, the epoxy resin is a medium-viscosity epoxy resin with a viscosity of 1000-10000 mPa·s.

[0029] Optionally, the curing agent is a room temperature curing agent.

[0030] Optionally, the straight steel fiber has a length of 13 mm, a diameter of 0.2 mm, and a tensile strength of ≥ 2000 MPa.

[0031] Optional, expanded polypropylene particles with a diameter of 3~5mm and an apparent density of 20~60kg / m 3 The foaming ratio in its preparation process is 15~45.

[0032] Optionally, triethanolamine, 99% pure; Optionally, basalt fibers with an average length of 13 mm and an average diameter of 10 μm; Optionally, the coarse aggregate is basalt crushed stone with a crushing value of ≤10% and a particle size of 5~8mm.

[0033] The anti-penetration area corresponds to the cavity area and crushing area in the target body. The cavity area is the tunnel area formed inside the target body after the projectile invades, and this part usually bears greater impact force and compressive stress; the crushing area is the area where local material damage is caused after the projectile enters the target body. The anti-penetration area adopts a block stone concrete structure, and uses grouting material to fill the gaps between the densely packed blocks to bond the blocks into a whole. The block stone concrete has higher strength and hardness, can withstand greater impact pressure, and prevent excessive crushing of the anti-penetration area; epoxy resin and curing agent are added to the grouting material to improve the bonding performance.

[0034] The anti-cracking area corresponds to the cracking area in the target body. During the invasion of the projectile, the cracking area of ​​the target body will experience crack expansion. A high-toughness material mixed with steel fiber and basalt fiber is used. The compounding of steel fiber and basalt fiber can increase toughness and effectively prevent the rapid expansion of cracks, reduce the propagation of cracks in the target body, and effectively improve the ductility and crack resistance of concrete.

[0035] The energy absorption area corresponds to the elastic area in the target body. The function of the elastic area is to absorb and disperse energy through elastic deformation of the material after the projectile enters the concrete. The use of foamed polypropylene concrete can absorb the impact energy transmitted after the projectile enters the target body, thereby reducing damage to the target body.

[0036] The undisturbed area corresponds to the undisturbed area of ​​the target body. The undisturbed area is the area that is not directly invaded by the projectile. The main function of this area is to support and stabilize the structure of the target body and prevent the external impact force from causing the overall instability of the target body. The high strength of the high-strength concrete material used can ensure that the target body maintains its structural stability when subjected to external force impact and provide necessary support for other areas.

[0037] Optionally, on the cross section passing through the central axis of the prism, the interfaces between the undisturbed area, the energy absorption area, the crack resistance area and the penetration resistance area are curved segments convex toward the interior of the prism, and the endpoints of the curved segments are located on the projectile-facing surface, and the curved segments are symmetrical with respect to the central axis of the prism. The overall structure is divided in a curved surface form, which is consistent with the interface shapes of various regions of the cavity expansion phenomenon caused by the impact after the projectile penetrates the target body in the cavity expansion theory, and can effectively play its design function in the actual impact process.

[0038] Optionally, the curve segment is a parabola segment, a hyperbola segment or an elliptic curve segment.

[0039] Optionally, the thickness of the anti-cracking area and the thickness of the energy absorption area are (1~2):1.

[0040] Optionally, the cross-section of the anti-penetration area on the impact surface accounts for 40-60% of the impact surface.

[0041] The method for preparing the above-mentioned concrete protection unit comprises the following steps: S1. Prepare a casting mold of a set shape, the mold including casting devices for an undisturbed area, an energy-absorbing area, an anti-cracking area, and an anti-penetration area; S2. Mixing the raw materials for the undisturbed area and then pouring the mixture to obtain an undisturbed area; S3, using triethanolamine in the raw materials for preparing the energy absorption region to modify the surface of the foamed polypropylene particles, then sprinkling cement to coat the outside of the foamed polypropylene particles to form energy-absorbing particles with a core-shell structure, and then mixing with other raw materials and pouring to obtain the energy absorption region; S4, mixing the raw materials for preparing the anti-cracking region and then pouring the mixture to obtain the anti-cracking region; S5. After uniformly mixing the epoxy resin and curing agent in the raw materials for preparing the anti-penetration area, other raw materials except the stone blocks are added and mixed to obtain a grouting material. The grouting material is used as an adhesive to bond the densely packed stone blocks into a whole to obtain the anti-penetration area, thereby obtaining a concrete protection unit.

[0042] Optionally, in S1, 3D printing technology is used to prepare curved surface molds of the interfaces of various functional areas (including energy absorption areas, anti-cracking areas and anti-penetration areas) using energy-absorbing materials; at the same time, a cubic mold with the same external dimensions as the concrete protection unit is made; then the curved surface molds of each functional area are placed into the cubic mold in turn, and suspended and fixed by support rods, so that the curved surface molds do not contact each other, and finally form an overall mold system.

[0043] Optionally, in S2, cement, silica fume, fly ash, fine aggregate and coarse aggregate are mixed, dry-mixed at a stirring speed of 100-150 rpm for 4-6 min, water and a water reducer are added, wet-mixed at a stirring speed of 50-80 rpm until uniform, and then poured into a mold to obtain an undisturbed area.

[0044] Optionally, in S3, energy-absorbing granular cement, silica fume, fly ash and fine aggregate are dry-mixed and then water and a water-reducing agent are added. Subsequently, basalt fiber is added during a wet mixing process, and the mixture is evenly mixed before pouring.

[0045] Optionally, in S3, the stirring speed in the dry mixing stage is 100-150 rpm, and the dry mixing time is 4-6 min; the stirring speed in the wet mixing stage is 50-80 rpm; and after adding basalt fiber, the stirring speed is 30-50 rpm.

[0046] Optionally, in S4, cement, silica fume, fly ash and fine aggregate are dry-mixed and then water and a water reducing agent are added. Then, steel fiber and basalt fiber are sequentially added during a wet mixing process, and the mixture is evenly mixed before pouring.

[0047] Optionally, in S4, the stirring speed in the dry mixing stage is 100-150 rpm, and the dry mixing time is 4-6 min; the stirring speed in the wet mixing stage is 50-80 rpm; and after adding the steel fiber and basalt fiber, the stirring speed is 30-50 rpm.

[0048] Optionally, in S5, first, epoxy resin and curing agent are mixed evenly to obtain an epoxy mixture; then, cement, silica fume, fly ash and fine aggregate are dry-mixed, water and a water reducer are added, and wet-mixed until uniform; then, the epoxy mixture is slowly added to the mixer to ensure that the grouting materials are evenly mixed.

[0049] Optionally, in S5, the stirring speed in the dry mixing stage is 100-150 rpm, and the dry mixing time is 4-6 minutes; and the stirring speed in the wet mixing stage is 50-80 rpm.

[0050] Optionally, the method further includes step S6, curing the concrete protection unit for a set time under standard curing conditions.

[0051] A protective device comprises the above-mentioned concrete protective unit, wherein a plurality of concrete protective units are closely arranged and connected by adhesive.

[0052] Optionally, it includes multiple layers of concrete protection units, which are arranged in a layer-by-layer staggered manner, and the staggered amount of adjacent layers is 1 / 2 of the side length of the concrete protection unit in that direction.

[0053] The application of the above-mentioned protective devices is mainly suitable for places that require strong protection and impact resistance, especially for military shooting ranges, bulletproof facilities, building protection, and structural protection in high-risk areas.

[0054] Example 1 Based on the cavity expansion theory, after the projectile enters the target, it will form multiple different areas along its path, such as Figure 3 As shown, it includes the cavity area, crushing area 34, cracking area 33, elastic area 32 and undisturbed area 31 of the target. The stress and failure characteristics of each area are different. A single design method cannot effectively strengthen according to these characteristics, thus failing to achieve the best protection effect.

[0055] A protective device 1, such as Figure 2 As shown, it includes three layers of concrete protection unit layers, each layer of concrete protection unit layer includes a plurality of closely packed concrete protection units 2 of the same shape and material. The concrete protection unit 2 used is a cube with a side length of 300 mm. The offset of adjacent layer units is 1 / 2 of the unit side length. The overall outer dimensions of the protection device are 900 mm × 900 mm × 900 mm. The orientation of each concrete protection unit 2 is the same, and the anti-penetration area faces the bullet 3, which is the bullet-facing surface.

[0056] The cross-sectional structure of a single concrete protection unit along the central axis is as follows: Figure 4 As shown, it includes an undisturbed area 21, an energy-absorbing area 22, an anti-cracking area 23 and an anti-penetration area 24 that are wrapped layer by layer from the outside to the inside, and the undisturbed area 21, the energy-absorbing area 22, the anti-cracking area 23 and the anti-penetration area 24 expose their areas on the impact surface respectively, and the interface shape of each area is a parabolic segment. The depth of the anti-penetration area 24 extending from the impact surface to the inside is 100 mm, and the maximum width is 120 mm. The layer thickness of the anti-cracking area 23 is 50 mm and the tip is appropriately thickened to 60 mm. The layer thickness of the energy-absorbing area 22 is 40 mm and the tip is appropriately thickened to 50 mm.

[0057] The structure of the concrete protection unit corresponds to the target structure of the cavity expansion theory, such as Figure 3 and Figure 4As shown, the anti-penetration area 24 corresponds to the cavity area and the crushing area 34 in the target body, the anti-cracking area 23 corresponds to the cracking area 33 in the target body; the energy absorption area 22 corresponds to the elastic area 32 in the target body, and the undisturbed area 21 corresponds to the undisturbed area 31 of the target body.

[0058] The mass fractions of raw materials prepared in each region are shown in Table 1.

[0059] Table 1. Mass fraction of raw materials prepared in each region

[0060] Among them, the cement is 52.5 grade ordinary Portland cement with a specific surface area of ​​350~400m² / kg; The mass percentage of silicon dioxide in the silica fume is not less than 97%, the pozzolanic activity index of the silica fume is greater than 95%, the specific surface area is greater than 21.0m² / g, and the density is 2.20g / cm³; The fly ash is Class I fly ash, with a loss on ignition of less than 3.0%, a specific surface area greater than 1000 cm² / g, and its main components include: silicon oxide and aluminum oxide; The fine aggregate is natural river sand with a fineness modulus of 2.8 and a maximum particle size of 4.75 mm; The block is corundum block, the main component is Al2O3, the density is 3800kg / m 3 , elastic modulus is 400Gpa, hardness HRA is 86~92, particle size is 100~150mm; The straight steel fiber has a length of 13mm and a diameter of 0.2mm, and a tensile strength of ≥2000MPa; Foamed polypropylene particles, diameter 3~5mm, apparent density 20~60kg / m 3 , the foaming ratio is 15~45; triethanolamine, 99% purity; Basalt fiber, with an average length of 13 mm and an average diameter of 10 μm; The coarse aggregate is basalt crushed stone with a crushing value of ≤10% and a particle size of 5~8mm; The water reducing agent is polycarboxylic acid water reducing agent with a water reducing rate of >30%.

[0061] Preparation method Figure 1 As shown, pour from the outside to the inside, remove the mold layer by layer after solidification to prevent the mold from being left in the concrete protection unit. The specific steps include: S1. Use 3D printing technology and energy-absorbing materials to prepare curved surface molds of the interfaces between functional areas (including energy-absorbing areas, anti-cracking areas, and anti-penetration areas); at the same time, make a cubic mold that is consistent with the external dimensions of the concrete protection unit; then place the curved surface molds of each functional area into the cubic mold in turn, and hang and fix them through support rods. The curved surface molds do not contact each other, and finally form an integral mold system; prepare a casting mold of a set shape, which includes casting devices for the undisturbed area, energy-absorbing area, anti-cracking area, and anti-penetration area.

[0062] S2. According to the components shown in Table 1, the cement, silica fume, fly ash, fine aggregate and coarse aggregate in the preparation raw materials of the undisturbed area were mixed, and dry-mixed at a stirring speed of 100 rpm for 4 minutes; then water and a water reducer were added and stirred at a stirring speed of 50 rpm until uniform, and then poured into a mold to obtain an undisturbed area. Since the undisturbed area does not include a curved surface, the overall mold of this protective device was removed after solidification.

[0063] S3. According to the components shown in Table 1, triethanolamine in the raw materials for preparing the energy absorption region was sprayed on the foamed polypropylene particles for surface modification. The spraying thickness was 250±50 μm. Cement was then sprinkled on the outside of the foamed polypropylene particles to form energy-absorbing particles with a core-shell structure. The energy-absorbing particles, cement, silica fume, fly ash and fine aggregate were dry-mixed at a stirring speed of 100 rpm for 4 minutes. Water and a water reducer were then added and wet-mixed at a stirring speed of 50 rpm until uniform. The basalt fiber was then evenly spread on the surface of the slurry through a vibrating screen. The mixture was continued to be stirred at a stirring speed of 50 rpm until uniform. After uniform mixing, the mixture was poured to obtain the energy absorption region. The curved mold of the energy absorption region was removed after solidification.

[0064] S4. According to the components shown in Table 1, cement, silica fume, fly ash and fine aggregate were mixed and dry-mixed at a stirring speed of 100 rpm for 4 minutes; then water and water reducer were added and stirred at a stirring speed of 50 rpm until uniform; then straight steel fiber was added three times through a vibrating screen, with an interval of 1 minute between each addition; then basalt fiber was evenly spread on the surface of the slurry through a vibrating screen and stirred at a stirring speed of 50 rpm until uniform; after uniform mixing, it was poured into a mold to obtain a crack-resistant area, and the curved mold of the crack-resistant area was removed after solidification.

[0065] S5. According to the components shown in Table 1, the epoxy resin and curing agent in the raw materials for preparing the anti-penetration area are mixed in proportion and stirred thoroughly until a uniform solution is formed. Then, the cement, silica fume, fly ash and fine aggregate are mixed and dry-mixed at a stirring speed of 100 rpm for 4 minutes. Then, water and a water reducer are added and stirred at a stirring speed of 50 rpm until uniform. After that, the pre-mixed epoxy resin and curing agent mixture is gradually added to the mixer to ensure uniform mixing with the slurry. The stirred cement slurry is used as a binder and evenly applied to the surface of the corundum block. The corundum blocks are arranged tightly and evenly in a stacked manner. Finally, the binder is poured to fill the gaps to obtain an anti-penetration area, thereby obtaining a concrete protective unit.

[0066] S6. Cure the prepared concrete protective unit for 28 days under standard curing conditions (temperature 20±2℃, RH>90%).

[0067] S7. Apply the epoxy resin-based interface agent evenly on the contact surface by brushing or spraying, with a spraying thickness of 250±50μm. After coating, wait for 15 minutes; then stack according to the set interlayer staggered method, and obtain the protective device after curing.

[0068] Comparative Example 1 An ultra-high performance concrete target is made of a single material, has no stacking structure and no gradient structure, has a size of 900 mm × 900 mm × 900 mm, and is prepared from raw materials including the following raw materials in parts by weight: 500 parts of cement, 50 parts of silica fume, 50 parts of fly ash, 900 parts of fine aggregate, 156 parts of steel fiber, 125 parts of water, and 8 parts of water reducer.

[0069] The difference from the anti-cracking region in Example 1 is that no basalt fiber is added; other raw material requirements and preparation steps are the same as those of the anti-cracking region in Example 1.

[0070] Comparative Example 2 A three-layer conventional functionally graded concrete target, measuring 900 mm × 900 mm × 900 mm, consists of a surface layer (fiber-reinforced concrete), a middle layer (high-strength concrete), and a bottom layer (fiber-reinforced concrete). The raw materials, mass fractions, and layer thicknesses for each layer are shown in Table 2.

[0071] Table 2 Composition and thickness of each layer

[0072] The difference between the surface layer and the bottom layer and the anti-cracking area in Example 1 is that there is no basalt fiber. The other raw material requirements and preparation steps are the same as those of the anti-cracking layer in Example 1.

[0073] The raw material requirements and preparation steps of the intermediate layer are the same as those of the undisturbed layer in Example 1.

[0074] Comparative Example 3 A composite protective device, measuring 900mm×900mm×900mm, includes three composite protective plates with a thickness of 300mm, the composite protective plates including an undisturbed layer of 100mm, an energy-absorbing layer of 60mm, an anti-cracking layer of 60mm, and an anti-penetration layer of 80mm; wherein the material and preparation method of the undisturbed layer are the same as those of the undisturbed area of ​​Example 1, the material and preparation method of the energy-absorbing layer are the same as those of the energy-absorbing area of ​​Example 1, the material and preparation method of the anti-cracking layer are the same as those of the anti-cracking area of ​​Example 1, and the material and preparation method of the anti-penetration layer are the same as those of the anti-penetration area of ​​Example 1.

[0075] The difference from Example 1 is that this comparative example does not design the concrete protection unit according to the combination of cavity expansion theory and prefabricated structure, but arranges the same material into a plane layer.

[0076] Experimental example The products obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested for their resistance to high-speed projectile penetration.

[0077] The test conditions in the method for testing the performance of resisting high-speed projectile penetration include: preparing the test object into a prismatic target, using a pointed egg-shaped projectile with a diameter of 28 mm, and the projectile material is 30CrMnSiNi2A high-strength alloy steel (yield strength of 1370-1466 MPa, ultimate strength of 1770 MPa, Rockwell hardness of 55 HRC); the test device mainly includes a barrel, a high-speed camera and a target body, the barrel is used to launch the projectile and hit the target body in front, the set projectile impact speed is 400 m / s, and the high-speed camera is installed on the side of the trajectory to capture the movement process of the projectile; then, the degree of damage to the concrete target body by the high-speed projectile is evaluated by measuring the penetration depth, crater diameter and crater volume of the target body.

[0078] The test results of the resistance to high-speed projectile penetration performance are shown in Table 3.

[0079] Table 3 Test results

[0080] Comparing experimental data, Example 1 (stacked structure) achieved a penetration depth of 320mm, significantly superior to Comparative Examples 1 (580mm) and 2 (450mm). The stacked structure, through its modular design and integration of gradient materials, effectively reduces the concentration of impact energy and enhances the target's penetration resistance. While traditional monolithic and functionally graded structures offer some improvement in penetration resistance, they still fail to effectively disperse impact energy compared to stacked structures, resulting in greater penetration depths.

[0081] The pit diameter in Example 1 is 120 mm, significantly smaller than that in Comparative Example 1 (180 mm) and Comparative Example 2 (160 mm). The stacked structure effectively disperses the energy generated by the projectile impact through a gradient design between layers and modular stacking, reducing the pit diameter. In contrast, the single-material structure in Comparative Example 1 lacks effective energy dispersion, resulting in a larger pit diameter. While Comparative Example 2, with its functional gradient design, incorporates a transitional design between layers, the pit diameter remains relatively large due to the lack of a stacked structure transition.

[0082] In terms of pit volume, Example 1 achieved a pit volume of 490,432 mm³, significantly reducing the pit volume of the stacked structure compared to Comparative Example 1 (758,753 mm³) and Comparative Example 2 (684,782 mm³). The stacked structure's rational energy absorption and dispersion design prevents concentrated energy release, effectively reducing the pit volume. This demonstrates that the stacked structure better distributes and dissipates impact energy during projectile impact, reducing structural damage. In contrast, traditional homogeneous concrete and functionally graded structures, due to incomplete energy absorption, have larger pit volumes, resulting in more severe structural damage.

[0083] Furthermore, test data for Comparative Example 3 (planar layer structure) showed a penetration depth of approximately 500 mm, a crater diameter of approximately 170 mm, a crater volume of approximately 724,389 mm³, and a crack propagation length exceeding 180 mm. These data indicate that although Comparative Example 3 utilizes the same protective material as Example 1, due to its exclusive planar layer structure, it fails to achieve modular stacking and gradient distribution, resulting in poor energy dispersion and absorption, and consequently, lower protective performance.

[0084] The crack propagation length in Example 1 was controlled to ≤50 mm, while that in Comparative Examples 1 and 2 exceeded 200 mm and 150 mm, respectively. The stacked structure effectively limits crack propagation through the staggered design and material gradient transition between units, significantly improving the impact resistance and durability of the overall structure. On the other hand, Comparative Example 3, due to its structural design consisting of only planar layers, lacks an effective crack control mechanism, resulting in rapid crack propagation and widespread damage.

[0085] Finally, in terms of maintainability, the modular stacking design of Example 1 enables the replacement of individual modules of the protection unit when damaged, thereby significantly reducing maintenance costs and construction difficulty; while Comparative Examples 1, 2, and 3 all require overall reconstruction, and the maintenance cost is relatively high.

[0086] In summary, the stacked structure (Example 1) demonstrates significant advantages in terms of penetration resistance, energy absorption, crack control, and maintainability. Each unit of the stacked structure effectively disperses energy when impacted by a high-speed projectile, reducing crater volume and crack propagation, significantly improving the target's protective effectiveness. In comparison, while traditional homogeneous concrete (Comparative Example 1), functionally graded concrete (Comparative Example 2), and planar layer structures (Comparative Example 3) also offer some protection, their performance in terms of penetration resistance, crack control, and maintainability is relatively weak due to their insufficient energy absorption and dispersion capabilities.

[0087] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A concrete protection unit in the shape of a prism, characterized in that: The single top surface of the prism is the impact surface, and the prism includes an undisturbed area, an energy-absorbing area, a crack-resistant area, and a penetration-resistant area that are layered from the outside to the inside, and the cross-sections of the undisturbed area, the energy-absorbing area, the crack-resistant area, and the penetration-resistant area are respectively exposed on the impact surface; The raw materials for preparing the undisturbed area, the energy absorption area, the anti-cracking area and the anti-penetration area respectively include: 360-520 parts of cement, 36-52 parts of silica fume, 36-52 parts of fly ash, 800-1000 parts of fine aggregate, 120-130 parts of water and 5-10 parts of high-efficiency water reducer; The raw materials for preparing the undisturbed area include 800-1000 parts of coarse aggregate; The raw materials for preparing the energy absorption region include 2-10 parts of foamed polypropylene particles, 1-5 parts of triethanolamine and 39-78 parts of basalt fibers; The raw materials for preparing the crack-resistant region include 156-312 parts of steel fiber and 39-78 parts of basalt fiber; The raw materials for preparing the anti-penetration area include 50-100 parts of epoxy resin, 10-30 parts of curing agent and block stone, and the ratio of the mass of the block stone to the sum of the mass of other raw materials for preparing the anti-penetration area is (10-15):(2-3).

2. The concrete protection unit according to claim 1, characterized in that: On a cross section passing through the central axis of the prism, the interfaces between the undisturbed area, the energy-absorbing area, the anti-crack area, and the anti-penetration area are curved segments convex toward the interior of the prism, and the endpoints of the curved segments are located on the bullet-facing surface, and the curved segments are symmetrical with respect to the central axis of the prism; Or, the curve segment is a parabola segment, a hyperbola segment or an elliptic curve segment; Or, the thickness of the anti-cracking region and the thickness of the energy absorption region are (1-2): 1; Alternatively, the cross-section of the anti-penetration area on the impact surface accounts for 40-60% of the impact surface.

3. The concrete protection unit according to claim 1, characterized in that: The cement is 52.5 grade ordinary Portland cement; Or, the mass percentage of silicon dioxide in silica fume is not less than 97%; Or, the fly ash is Class I fly ash with a loss on ignition of less than 3.0%; Alternatively, the fine aggregate is natural river sand; Or, the water reducer is a polycarboxylate water reducer; Or, the block is one or more high-strength mineral blocks such as corundum block, basalt block, quartz sandstone block, etc.; Or, a straight steel fiber with a steel fiber length of 13 mm and a diameter of 0.2 mm; Alternatively, expanded polypropylene particles having a diameter of 3 to 5 mm and an expansion ratio of 15 to 45 during the preparation process; or, basalt fibers, with an average length of 13 mm and an average diameter of 10 μm; Alternatively, the coarse aggregate is basalt crushed stone with a crushing value of ≤10% and a particle size of 5~8mm.

4. A method for preparing a concrete protection unit according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Prepare a casting mold of a set shape, the mold including casting devices for an undisturbed area, an energy-absorbing area, an anti-cracking area, and an anti-penetration area; S2. Mixing the raw materials for the undisturbed area and then pouring the mixture to obtain an undisturbed area; S3, using triethanolamine in the raw materials for preparing the energy absorption region to modify the surface of the foamed polypropylene particles, then sprinkling cement to coat the outside of the foamed polypropylene particles to form energy-absorbing particles with a core-shell structure, and then mixing with other raw materials and pouring to obtain the energy absorption region; S4, mixing the raw materials for preparing the anti-cracking region and then pouring the mixture to obtain the anti-cracking region; S5. After uniformly mixing the epoxy resin and curing agent in the raw materials for preparing the anti-penetration area, other raw materials except the stone blocks are added and mixed to obtain a grouting material. The grouting material is used as an adhesive to bond the densely packed stone blocks into a whole to obtain the anti-penetration area, thereby obtaining a concrete protection unit.

5. The method for preparing a concrete protection unit according to claim 4, characterized in that: In S1, 3D printing technology is used to prepare curved surface molds of the interfaces of various functional areas using energy-absorbing materials.

6. The method for preparing a concrete protection unit according to claim 4, characterized in that: In S3, energy-absorbing granular cement, silica fume, fly ash and fine aggregate are dry-mixed, and then water and a water-reducing agent are added. Basalt fiber is then added during the subsequent wet mixing process, and the mixture is uniformly mixed before pouring. Alternatively, in S4, cement, silica fume, fly ash and fine aggregate are dry-mixed and then water and a water reducing agent are added. Subsequently, steel fiber and basalt fiber are sequentially added during a wet mixing process, and the mixture is evenly mixed before pouring.

7. The method for preparing a concrete protection unit according to claim 4, characterized in that: The method comprises step S6 of curing the concrete protection unit for a set time under standard curing conditions.

8. A protective device, characterized in that: The concrete protection unit comprises the concrete protection unit according to any one of claims 1 to 3, wherein a plurality of concrete protection units are closely arranged and connected by adhesive.

9. The protective device according to claim 8, characterized in that The invention comprises multiple layers of concrete protection units, which are arranged in an inter-layer staggered manner.

10. Use of the protective device according to any one of claims 8 to 9 in the field of building protection.

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