Low-shrinkage impact-resistant ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses low-shrinkage and impact-resistant ultra-high performance concrete and a preparation method thereof. According to the method, # imgabs 0 is solidified in high-strength porous aggregate to serve as a shrinkage compensation carrier, self-adaption and self-adjustment of the expansion effect are achieved, the problem of uneven expansion is avoided, the total shrinkage value of the prepared ultra-high performance concrete within 28 days is smaller than or equal to 256 # imgabs 1 #, and compared with a traditional UHPC material, the volume stability is improved by 30% or above. According to the invention, the modified short-cut basalt fiber subjected to surface adsorption of a fiber dispersant is added into the premix, so that the three-dimensional uniform dispersion characteristic is further improved, steel fiber (a surface cured lithium silicate layer) can be cooperatively etched to form a multi-scale enhancement system, and through a fiber-matrix interface mechanical occlusion and energy dissipation synergistic mechanism, the drop hammer impact resistance energy is greater than or equal to 45kJ, and the impact resistance is greater than or equal to 350kJ. And the impact resistance is improved by 38.7%.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a low-shrinkage and impact-resistant ultra-high performance concrete and a preparation method thereof. Background Art

[0002] Ultra-high performance concrete (UHPC) is a new type of cement-based composite material with ultra-high strength, ultra-high toughness and ultra-high durability, providing unprecedented solutions for engineering applications in various extreme environments. How to further explore and optimize the potential of UHPC has become a forefront hot spot in materials science research.

[0003] During the setting, hardening and service process after hardening of UHPC, there will be a large autogenous shrinkage problem, the risk of early cracking is very high, and the shrinkage development speed is extremely fast, and the deformation amount can reach about 5-15 times that of ordinary concrete. Using admixtures such as expansive agents and shrinkage-reducing agents is the most effective countermeasure, but these admixtures are extremely sensitive to the water consumption of UHPC. Directly adding them to UHPC is likely to affect the fluidity of the mixture and the final strength. If the dispersion is uneven, it may also cause uneven expansion, endangering the structural safety.

[0004] In addition, the performance of UHPC under impact and tensile stresses is often insufficient. The main reasons are: (1) The surface of the steel fiber is smooth, resulting in poor anchoring and bonding effect with the UHPC matrix, affecting the overall bonding strength. (2) By increasing the dosage of steel fibers to improve the impact resistance of UHPC, the effect has certain limitations. If the addition of steel fibers is excessive, it will greatly increase the consistency of UHPC, making the mixing and pumping operations difficult, and further increasing the overall construction difficulty.

[0005] Therefore, researching a low-shrinkage and impact-resistant ultra-high performance concrete can significantly improve its performance under extreme dynamic loads and complex stress conditions. It has important practical significance for expanding the application of UHPC in fields such as bridges, tunnels, high-rise buildings and special engineering structures. Summary of the Invention

[0006] In order to effectively improve the shrinkage problem of ultra-high performance concrete and further enhance its impact resistance, the present invention has developed a low-shrinkage and impact-resistant UHPC and a preparation method thereof. This method is to Solidify in high-strength porous aggregates as a shrinkage compensation carrier to achieve self-adaptive and self-regulating expansion effects, avoid uneven expansion problems, and the total shrinkage value of the prepared ultra-high performance concrete at 28 days ≤ 256 , compared with traditional UHPC materials, the volume stability is improved by more than 30%. The present invention also adds modified chopped basalt fibers with surface-adsorbed fiber dispersant to the premix, further enhancing the three-dimensional uniform dispersion characteristics. It can cooperate with etched steel fibers (with a surface-cured lithium silicate layer) to form a multi-scale reinforcement system. Through the synergistic mechanism of mechanical interlocking and energy dissipation at the fiber-matrix interface, the drop hammer impact resistance energy is ≥45 kJ, achieving a 38.7% improvement in impact resistance performance.

[0007] The low-shrinkage and impact-resistant ultra-high performance concrete described above is composed of component A, component B, and component C in a mass ratio of 2000 - 2200:180 - 220:150 - 160. During preparation, first, mix component A and component B for 2 - 3 minutes, then add tap water and stir until the mixture completely turns into a colloidal state, and finally add component C and continue to stir for 2 - 3 minutes to obtain the product.

[0008] Component A includes zirconium silicate ash with a zirconium content > 3.2%, modified chopped basalt fibers with surface-adsorbed fiber dispersant, and a composite admixture. Component B is porous aggregate pre-wetted with sodium silicate hydrate and surfactant, and the cylinder compressive strength is ≥10 MPa. Component C is steel fiber with a surface etching depth of 0.02 - 0.04 mm and coated with silane coupling agent and lithium silicate.

[0009] The preparation method of component A is as follows: Mix 500 - 850 parts by mass of cement, 30 - 150 parts by mass of zirconium silicate ash, and 30 - 100 parts by mass of microbeads, then successively add 300 - 1000 parts by mass of quartz sand and 30 - 100 parts by mass of calcium powder, and stir at 200 - 300 r / min for 1 - 2 minutes; then add 5 - 20 parts by mass of the composite admixture and 10 - 30 parts by mass of ultrafine powder, increase the stirring speed to 500 r / min and stir for 2 - 3 minutes; finally add 1 - 5 parts by mass of modified chopped basalt fibers. Control the loose bulk density to be ≥1650 kg / m³.

[0010] The composite admixture is composed of 65 - 75 parts by mass of water reducer, 2 - 8 parts by mass of retarder, 15 - 25 parts by mass of viscosity reducer, 3 - 5 parts by mass of defoamer, and 1 - 3 parts by mass of crystal nucleation promoter.

[0011] The water reducer is a polycarboxylate-based water reducer, preferably a polycarboxylate water reducer of methyl methacrylate - methyl acrylate copolymer type, with a chloride ion content ≤0.01%, a slump loss of ≤12% in 120 minutes, and a water reduction rate ≥45%.

[0012] The retarder is one or several of sodium gluconate, citrate, or pyrophosphate.

[0013] The viscosity reducer is a polyether-based polymer compound.

[0014] The defoamer is a polyether-modified silicone oil or a mineral oil-based defoamer.

[0015] The nucleating agent is nano-aluminum oxide particles surface-modified with sodium dodecylbenzenesulfonate.

[0016] The modification method of the modified chopped basalt fiber is as follows: Immerse the basalt fiber in the strengthening solution for 60 - 90 minutes, and finally dry and cut it at 30 - 80 °C to obtain it. The active ingredients in the strengthening solution are composed of 2% by mass of polyethylene oxide, 0.5 - 1.5% by mass of γ-glycidoxypropyltrimethoxysilane, 1 - 3% by mass of isopropanol, 0.5 - 1.5% by mass of silicon dioxide, and 0.5 - 1.5% by mass of polyethylene glycol.

[0017] The preparation method of component B is as follows: (1) Mix 30 - 50 parts by mass of shale, 20 - 40 parts by mass of metal tailings, 10 - 30 parts by mass of fly ash, 10 - 20 parts by mass of clay, 5 - 15 parts by mass of silicon dioxide, and 5 - 15 parts by mass of carbonaceous raw material into balls, and then calcine them in a muffle furnace at 1200 - 1350 °C for 2 - 3 hours to obtain porous aggregates. (2) Immerse the porous aggregates in a mixed aqueous solution of 15% by mass of sodium silicate hydrate and 5% by mass of surfactant for 40 - 60 minutes, and stir once every 10 minutes. (3) Take out the impregnated aggregates, dry them at 40 - 120 °C for 1 - 2 hours to volatilize the residual solution on the surface and form a stable coating layer. (4) Before use, pre-wet the aggregates obtained in step (3) with sodium silicate hydrate and surfactant.

[0018] The surfactant is a compound of α-olefin sulfonate and cetyltrimethylammonium bromide in a mass ratio of 3:1.

[0019] The carbonaceous raw material is a compound of bamboo charcoal powder and coconut shell activated carbon in a mass ratio of 6:4. Among them, the particle size of the bamboo charcoal powder is 50 - 100 mesh, the carbon content is ≥85%, and the specific surface area is ≥300 m² / g; the iodine value of the coconut shell activated carbon is ≥800 mg / g, and the methylene blue adsorption value is ≥15 mL / g.

[0020] The preparation method of component C is as follows: (1) The surface etching of steel fibers adopts an electrochemical method, the etching solution is a 10 - 15% nitric acid solution, the current density is 0.5 - 1.2 A / dm², and the surface roughness Ra after etching is ≥1.6 μm. (2) Then immerse the etched steel fibers in the silane hydrolysis solution for 3 - 5 minutes and bake at 90 - 120 °C for 0.5 - 2 hours. The silane hydrolysis solution is prepared by mixing γ - aminopropyltriethoxysilane and ethanol in a mass ratio of 1:5 and hydrolyzing them. (3) Take out the steel fibers and coat them with lithium silicate solution by brushing, spraying or dipping. The coating thickness is 5 - 10 μm, and an anti - peeling interface bonding layer is formed after drying.

[0021] The grading of the quartz sand and the porous aggregate satisfies the cumulative passing rate formula: , where D max is the maximum particle size, n = 0.45 - 0.55, and the grading deviation ≤ 5%.

[0022] The advantages of the present invention are as follows: 1. In the preparation of UHPC, the present invention innovatively uses high - strength porous aggregate as the carrier for shrinkage compensation. Its unique pore structure can not only store moisture and shrinkage - reducing components to achieve uniform internal curing inside the concrete, significantly reducing autogenous shrinkage and drying shrinkage during the hardening process, but also through the gradient release and penetration of shrinkage - reducing components to react with the cement hydration products to form C - S - H gel, filling the micro - voids and cracks in the concrete, thereby achieving precise compensation for the volume change of the UHPC matrix. Compared with traditional methods, this compensation method avoids the stress concentration problem caused by uneven expansion, ensuring the stability and durability of the overall structure of UHPC. In addition, when the compensation amount reaches balance or even surplus, the remaining hydration products can seal the pores of the porous aggregate, blocking the precipitation of internal shrinkage - reducing substances, further enhancing the strength of the porous aggregate, and at the same time realizing the self - adaptation and self - regulation of the expansion effect, significantly improving the long - term performance of the concrete.

[0023] 2. By etching the steel fibers, the present invention significantly increases the contact area between the steel fibers and the UHPC matrix, enhances the grip force and mechanical interlocking effect, thus effectively improving the tensile strength of the concrete. In addition, lithium silicate adheres to the surface of the etched steel fibers. Lithium silicate can promote the formation of cement gel in the concrete, increase the calcium ion concentration, and react with the hydration products to form calcium silicate gel crystals, further enhancing the bonding ability between the steel fibers and the UHPC matrix. This dual - enhancement mechanism (mechanical interlocking + chemical bonding) not only significantly improves the mechanical properties of the concrete but also ensures the uniform dispersion and long - term stability of the steel fibers in the concrete.

[0024] 3. The chopped basalt fibers used in the present invention are surface-treated and adsorbed with fiber dispersants, and their toughness and dispersibility are significantly improved. After adding to the UHPC premix, the dispersibility of the fibers is further optimized, and they act synergistically with the etched steel fibers to form a fine and uniform three-dimensional network structure inside the UHPC. This structure not only effectively enhances the fracture energy of the material but also greatly improves the impact resistance of the structure. In addition, the synergistic effect of basalt fibers and steel fibers also significantly improves the toughness and crack resistance of the concrete, enabling it to exhibit excellent energy absorption capacity and durability under dynamic load. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the flowchart for preparing low-shrinkage and impact-resistant ultra-high performance concrete in the specific embodiment of the present invention; Figure 2 is the etched steel fiber used in the present invention. The left figure is the overall effect diagram, and the right figure is the side view; Figure 3 is the top view of the etched steel fiber used in the present invention, where A is the effective diameter of the steel fiber, B is the etching depth of the steel fiber, and C is the diameter of the steel fiber before etching; Figure 4 is the schematic diagram of the impact resistance test experimental device of the present invention, where 1 is the drop hammer, 2 is the specimen, and 3 is the support. SPECIFIC EMBODIMENTS

[0026] Example 1 I. Preparation method of component A: 1. Respectively test the particle size distributions of cement, zirconium silicate ash (zirconium content > 3.2%), microspheres, quartz sand, calcium powder, ultrafine powder and composite admixture, determine the particle size range of the UHPC matrix material, and determine the dosage of each component based on means such as the improved MAA model and wet packing density test.

[0027] 2. Calculate 850 parts by mass of cement, 40 parts of zirconium silicate ash, 60 parts of microspheres, 40 parts of calcium powder, 10 parts of ultrafine powder, 480 parts of 18 - 40 mesh quartz sand, 160 parts of 40 - 70 mesh quartz sand, 160 parts of 70 - 100 mesh quartz sand, and 10 parts of composite admixture.

[0028] The composite admixture consists of 70 parts by mass of methacrylic acid - methyl acrylate copolymer polycarboxylate water reducer, 6 parts by mass of sodium gluconate, 20 parts by mass of polyether-based polymer compound, 3 parts by mass of mineral oil-based defoamer, and 2 parts by mass of nano-aluminum oxide particles surface-modified with sodium dodecylbenzenesulfonate.

[0029] 3. Determine the dosage of modified chopped basalt fibers, which accounts for 0.2% of the powder dosage, and is 3.62 parts by mass. The preparation method is as follows: (1) The molten basalt liquid is drawn at high speed through a platinum-rhodium alloy wire-drawing bushing to form filaments with a diameter of 3 - 12 μm μm, and then cleaned and dried to ensure that the fiber surface is clean and free of impurities; (2) Prepare the strengthening solution: Prepare a poly(ethylene oxide) (PEO) solution with a mass fraction of 2%, and then compound γ-glycidoxypropyltrimethoxysilane (mass fraction 1%), isopropyl alcohol (mass fraction 2%), silicon dioxide (mass fraction 1%), and polyethylene glycol (mass fraction 1%) in the solution. Continuously stir the solution until all substances are completely dissolved; (3) Immerse the basalt filaments in step (1) into the strengthening solution in step (2) to ensure that a layer of solution uniformly covers the fiber surface, soak for 75 min, and the soaking ambient temperature > 25 °C.

[0030] (4) Drying: Dry the fiber at 60 °C for a drying time > 3 h, and it is necessary to regularly observe the drying condition of the fiber to prevent over-drying or under-drying.

[0031] (5) Fiber cutting: Cut the modified basalt filaments to prepare basalt fibers with a length of 12 ± 2 mm.

[0032] 4. Mix all the raw materials in 2 and 3 evenly, and the loose bulk density is not less than 1650 kg / m 3 (tested according to GB / T24191-2009).

[0033] II. Preparation method of component B: 1. Mix 50 parts by mass of shale, 40 parts by mass of metal tailings, 30 parts by mass of fly ash, 20 parts by mass of clay, 10 parts by mass of silicon dioxide, and 10 parts by mass of a carbonaceous raw material (the carbonaceous raw material is a compound of bamboo charcoal powder and coconut shell activated carbon in a mass ratio of 6:4, where the bamboo charcoal powder has a particle size of 50 - 100 mesh, a carbon content ≥ 85%, and a specific surface area ≥ 300 m² / g; the iodine value of the coconut shell activated carbon ≥ 800 mg / g, and the methylene blue adsorption value ≥ 15 mL / g), form into balls, and calcine in a muffle furnace at 1200 °C for 3 hours to obtain porous aggregates; By mass, select 120 parts of porous aggregates with a particle size of 18 - 40 mesh, 40 parts of porous aggregates with a particle size of 40 - 70 mesh, and 40 parts of porous aggregates with a particle size of 70 - 100 mesh, wash repeatedly with deionized water and then place in a blast drying oven at 100 - 120 °C for drying.

[0034] 2. Prepare a mixed aqueous solution of sodium silicate hydrate with a mass fraction of 15% and 5% and a surfactant (the surfactant is a compound of α-olefin sulfonate and cetyltrimethylammonium bromide in a mass ratio of 3:1).

[0035] 3. Immerse the dried porous aggregate in an aqueous solution mixture of 15% sodium silicate hydrate and 5% surfactant by volume fraction for 60 minutes, with stirring every 10 minutes during the immersion, and then place it in a forced-air drying oven at 60 °C for drying and curing.

[0036] 4. Before use, test the water absorption rate of the porous aggregate. Pre-wet the cured porous aggregate with an aqueous solution mixture of 5% sodium silicate hydrate and 5% surfactant by mass fraction to ensure that the pre-wetting amount is not less than 85% of the maximum water absorption of the porous aggregate.

[0037] III. Preparation method of component C: 1. Using an electrochemical method, etch the surface of the steel fiber perpendicular to the length direction of the steel fiber. The etching solution is a 10 - 15% nitric acid solution, the current density is 0.5 - 1.2 A / dm². After etching, the surface roughness Ra ≥ 1.6 μm, the etching depth does not exceed 0.05 mm. After removing the etching depth from the cross-section of the steel fiber, the effective diameter is not less than 0.1 mm, and the length is 10 - 25 mm.

[0038] 2. Clean and dry the etched steel fiber, then immerse it in the silane hydrolysis solution for 5 minutes, and then place it in an oven at 100 °C for baking for 1 hour to cure the silane coupling agent into a film under high-temperature conditions. The silane hydrolysis solution is prepared by mixing γ-aminopropyltriethoxysilane and ethanol in a mass ratio of 1:5 and obtaining it with a hydrolysis time ≥ 30 minutes.

[0039] 3. Uniformly coat the surface of the steel fiber with the attached silane coupling agent with lithium silicate solution by spraying, and the coating thickness is 5 μm; 4. Place the coated steel fiber in a ventilated and dry place to allow the lithium silicate solution to dry naturally or accelerate drying at a suitable temperature.

[0040] The preparation method of low-shrinkage and impact-resistant ultra-high performance concrete is as Figure 2 shown, and specifically includes the following steps: Step 1: Add 2000 parts by mass of component A and 200 parts by mass of component B to a mixer, and stir at a low speed of 500 r / min for 3 minutes until uniform; Step 2: Slowly add all 185 parts by mass of tap water to the mixer, and stir at a low speed of 500 r / min until the mixture changes from a granular state to a colloidal state; Step 3: Slowly add component C to the mixer through a square-hole sieve to prevent agglomeration between the fibers; Step 4: After all of component C is added, stir at a high speed of 1400 r / min for 2 minutes and then pour and mold.

[0041] Pour the finished mixture into molds of 100×100×100 mm, 50×100 corrugated pipes, and 150×150×550 mm respectively. During the pouring process, air bubbles can be removed by low-frequency vibration for about 1-2 minutes.

[0042] Comparative Example 1 Comparative Example 1 is a common UHPC material in foreign markets, with a compressive strength of over 150 MPa, and is used in both bridge and protection projects. There are 2200 kg of powder and 200 kg of steel fiber.

[0043] Comparative Example 2 Comparative Example 2 is a common UHPC material in the Chinese market, with a compressive strength of over 150 MPa, and is commonly used in precast components and repair and reinforcement projects.

[0044] Comparative Example 3 Comparative Example 3 is a low-shrinkage UHPC material sold in the Chinese market, with a compressive strength grade of UC150, and is commonly used in bridge projects. There are 2200 kg of powder and 200 kg of steel fiber.

[0045] Standardly cure the UHPC materials of the above examples and comparative examples for 28 days, and then conduct compressive strength, autogenous shrinkage, and dynamic impact tests. The results are shown in Table 1.

[0046] Table 1 Test Results

[0047]

[0048] Result analysis: As can be seen from the results in Table 1 above, both the examples and the comparative examples meet the requirements of UC150. The total shrinkage of Example 28d is 256 , which is 86 less than that of Comparative Example 3 , with a reduction of about 25%; the impact energy of the example is 45.5 KJ, which is 12.7 KJ higher than that of Comparative Example 1, with an increase of about 38.7%.

[0049] Matters not covered in this invention are well-known technologies. The above examples are only used to illustrate the technical concept and characteristics of this invention. The purpose is to enable those who are familiar with this technology to understand the content of this invention and implement it accordingly, and it cannot be used to limit the protection scope of this invention. Any equivalent changes or modifications made according to the spirit and essence of this invention should be covered within the protection scope of this invention.

Claims

1. A low-shrinkage, impact-resistant ultra-high performance concrete, characterized in that, It is composed of component A, component B and component C in a mass ratio of 2000-2200:180-220:150-160; during preparation, first stir and mix component A and component B for 2-3 min, then add tap water and stir until the mixture is completely transformed into a colloidal state, and finally add component C and continue to stir for 2-3 min to obtain it; The component A includes zirconium silicate ash with a zirconium content > 3.2%, modified short-cut basalt fibers with a surface adsorbed fiber dispersant, and a composite admixture; The component B is a porous aggregate pre-wetted with sodium silicate hydrate and a surfactant, and the cylinder compressive strength ≥ 10 MPa; The component C is steel fibers with a surface etching depth of 0.02-0.04 mm and coated with a silane coupling agent and lithium silicate.

2. The low-shrinkage, impact-resistant ultra-high performance concrete according to claim 1, characterized in that, The preparation method of the component A is: mix 500-850 parts by mass of cement, 30-150 parts by mass of zirconium silicate ash, and 30-100 parts by mass of microspheres, then sequentially add 300-1000 parts by mass of quartz sand and 30-100 parts by mass of calcium powder, and stir at 200-300 r / min for 1-2 min; then add 5-20 parts by mass of the composite admixture and 10-30 parts by mass of ultrafine powder, increase the speed to 500 r / min and stir for 2-3 min; finally add 1-5 parts by mass of modified short-cut basalt fibers.

3. The low-shrinkage and impact-resistant ultra-high performance concrete according to claim 1, wherein The composite admixture is composed of 65-75 parts by mass of a water reducing agent, 2-8 parts by mass of a retarder, 15-25 parts by mass of a viscosity reducing agent, 3-5 parts by mass of an antifoaming agent, and 1-3 parts by mass of a crystal nucleus promoter; The water reducing agent is a polycarboxylate-based water reducing agent, preferably a polycarboxylate water reducing agent of methyl methacrylate-methyl acrylate copolymer, with a chloride ion content ≤ 0.01%, a slump loss of ≤ 12% in 120 min, and a water reducing rate ≥ 45%; The retarder is one or more of sodium gluconate, citrate, or pyrophosphate; The viscosity reducing agent is a polyether-based polymer compound; The antifoaming agent is a polyether-modified silicone oil or a mineral oil-based antifoaming agent; The crystal nucleus promoter is nano-aluminum oxide particles surface-modified with sodium dodecylbenzenesulfonate.

4. The low shrinkage, impact-resistant ultra-high performance concrete according to claim 1, characterized in that, The modification method of the modified short-cut basalt fibers is: immerse the basalt fibers in the strengthening solution for 60-90 min, and finally dry and cut at 30-80 °C to obtain them; The effective components in the strengthening solution are composed of 2% by mass of polyethylene oxide, 0.5-1.5% by mass of γ-glycidoxypropyltrimethoxysilane, 1-3% by mass of isopropanol, 0.5-1.5% by mass of silicon dioxide, and 0.5-1.5% by mass of polyethylene glycol.

5. The low-shrinkage, impact-resistant ultra-high performance concrete according to claim 1, characterized in that, The preparation method of the component B is: (1) Mix 30-50 parts by mass of shale, 20-40 parts by mass of metal tailings, 10-30 parts by mass of fly ash, 10-20 parts by mass of clay, 5-15 parts by mass of silicon dioxide, and 5-15 parts by mass of carbonaceous raw materials into balls, and calcine in a muffle furnace at 1200-1350 °C for 2-3 hours to obtain a porous aggregate; (2) Immerse the porous aggregate in an aqueous solution mixture of 15% by mass of sodium silicate hydrate and 5% by mass of surfactant for 40 - 60 minutes, and stir every 10 minutes; (3) Take out the impregnated aggregate, dry it at 40 - 120 °C for 1 - 2 hours to volatilize the residual solution on the surface and form a stable coating layer; (4) Before use, pre-wet the aggregate obtained in step (3) with sodium silicate hydrate and surfactant.

6. The low-shrinkage, impact-resistant ultra-high performance concrete according to claim 5, characterized in that, The surfactant is a compound of α-olefin sulfonate and cetyltrimethylammonium bromide in a mass ratio of 3:

1.

7. The low shrinkage and impact resistant ultra-high performance concrete according to claim 5, characterized in that, The carbonaceous raw material is a compound of bamboo charcoal powder and coconut shell activated carbon in a mass ratio of 6:

4. Among them, the particle size of the bamboo charcoal powder is 50 - 100 mesh, the carbon content is ≥85%, and the specific surface area is ≥300 m² / g; the iodine value of the coconut shell activated carbon is ≥800 mg / g, and the methylene blue adsorption value is ≥15 mL / g.

8. The low-shrinkage, impact-resistant ultra-high performance concrete according to claim 1, characterized in that, The preparation method of the C component is as follows: (1) Electrochemical method is used for surface etching of steel fibers. The etching solution is 10 - 15% nitric acid solution, the current density is 0.5 - 1.2 A / dm², and the surface roughness Ra after etching is ≥1.6 μm; (2) Then immerse the etched steel fibers in the silane hydrolysis solution for 3 - 5 minutes and bake at 90 - 120 °C for 0.5 - 2 hours. The silane hydrolysis solution is formed by mixing and hydrolyzing γ-aminopropyltriethoxysilane and ethanol in a mass ratio of 1:5; (3) Take out the steel fibers, and coat the lithium silicate solution by brushing, spraying or dipping. The coating thickness is 5 - 10 μm, and an anti-peeling interfacial bonding layer is formed after drying.

9. The low-shrinkage, impact-resistant ultra-high performance concrete according to claim 2, wherein, The grading of the quartz sand and the porous aggregate satisfies the cumulative passing rate formula: ， wherein, D max is the maximum particle size, n = 0.45 - 0.55, and the grading deviation ≤ 5%.

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