Radiation-proof ultra-high performance recycled concrete and preparation method thereof

Abstract

The invention relates to anti-radiation ultra-high performance recycled concrete and a preparation method thereof, and belongs to the technical field of building materials and solid waste resource utilization. According to the concrete, a multi-source silicon-aluminum precursor mainly comprising ground blast furnace slag and an alkali activating solution are subjected to synergistic reaction, Portland cement is not contained, and a compact structure and excellent mechanical, durability and radiation protection performance are formed by combining ferronickel slag reclaimed sand with refined particle size, compounded shielding reinforcing filler (lead glass and barite) and high-performance copper-plated steel fibers. According to the method, high-valued recycling of the industrial solid waste is achieved, and the method has excellent environment friendliness, engineering adaptability and long-term stability and is suitable for high-protection-demand scenes such as nuclear facilities and radioactive places.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a method for preparing radiation-proof ultra-high-performance recycled concrete. Background Art

[0002] At present, the main way to utilize nickel-iron slag as a resource is to use the ground nickel-iron slag powder as a mineral admixture for cement concrete or as a raw material for alkali-activated cement solid precursor. A large amount of nickel-iron slag is only piled in the open air or used as backfill material.

[0003] Ultra-high-performance concrete (UHPC), a cement-based composite material with exceptional mechanical properties and excellent durability, is one of the most innovative cement-based engineering materials of the past few decades. However, its production is limited to some extent by the high amount of cementitious materials used and the high energy consumption, which contradicts the concept of low-carbon cement-based engineering materials. Alkali-activated cementitious materials are a new type of green cementitious material prepared using active raw materials containing aluminum silicates and alkali activators. Alkali-activated cementitious materials exhibit high early strength, a dense microstructure, and excellent high-temperature and corrosion resistance. They also achieve high-value utilization of industrial waste and are considered one of the most promising low-carbon cementitious materials. Combined with the early strength and dense properties of alkali-activated cementitious materials, they can best meet the development needs of engineering materials with ultra-high strength and excellent durability, and have the potential to develop and produce UHPC. At the same time, the fine aggregate currently used in UHPC is mainly quartz sand. The overly concentrated resource acquisition has led to resource shortages and high costs, hindering the development and promotion of UHPC. The steel fibers in ultra-high-performance concrete and the high iron content in nickel-iron slag reclaimed sand both act as neutron shielding agents. When used in conjunction with shielding and reinforcing fillers, they effectively enhance the material's radiation protection. Furthermore, using solid waste to prepare reclaimed sand that meets grading requirements to produce ultra-high-performance, radiation-shielding recycled concrete reduces production costs and energy consumption while also repurposing solid waste resources. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing radiation-proof ultra-high performance recycled concrete.

[0005] A radiation-proof ultra-high-performance recycled concrete, composed of the following parts by weight: 90-125 parts of silicon-aluminum precursor; 30-70 parts of alkali activation solution; 90-110 parts of regenerated sand; 14 to 16 parts of shielding reinforcement filler; Steel fiber 1% to 3% volume content; Wherein, the silicon-alumina precursor is composed of one or more of ground blast furnace slag, fly ash or silica fume; The alkali activation solution is obtained by mixing sodium hydroxide and water glass with an initial modulus of 2.6 to 3.6 and allowing to stand for aging; The regenerated sand is nickel-iron slag with a median particle size of less than 1 μm after screening; The shielding reinforcement filler includes lead glass, barite and / or iron ore; The steel fiber is a straight copper-plated steel fiber with a diameter of 0.1 to 0.15 mm, a length of 10 to 15 mm, and a tensile strength of ≥2000 MPa.

[0006] The present invention introduces a multi-source alumina-silica precursor mainly composed of ground blast furnace slag into the concrete system, which reacts synergistically with an alkali-activated liquid of a specific modulus. In the absence of silicate cement, an ultra-high performance recycled concrete with high mechanical strength, dense structure and excellent radiation protection performance is prepared.

[0007] After mechanical activation, ground blast furnace slag possesses a high specific surface area and high potential activity. The CaO, SiO₂, and Al₂O₃ rich contents within it are rapidly released by the alkaline activation solution, forming a large amount of CASH gel and a small amount of NASH gel, thereby establishing a high-strength, low-porosity three-dimensional gelled framework. Compared to systems containing only fly ash or silica fume, ground blast furnace slag provides a richer source of Ca, significantly improving the system's early strength growth rate and ultimate compressive resistance.

[0008] Secondly, in the excitation system constructed by the present invention, blast furnace slag is highly sensitive to alkaline ion reactions, and its reaction rate is much faster than that of fly ash and silica fume. Its rapid reaction can provide an ion barrier for the subsequent release of low-activity substances, inhibit pH fluctuations in the system, effectively improve the reaction stability and gelation efficiency of the composite system, and give the material better density and consistent structure.

[0009] Furthermore, because the reaction product of ground blast furnace slag is primarily layered CASH, it possesses excellent space-filling and crystal cross-linking capabilities, effectively compensating for the porosity risks associated with porous recycled aggregates. In the present invention, the gel structure formed by its reaction with low-modulus water glass and NaOH exhibits extremely high micropore dominance, resulting in a total porosity of less than 5.5% in the final material, with harmless pores with a diameter of less than 50 nm accounting for over 70%, far superior to existing technologies that do not incorporate slag or use only fly ash.

[0010] Different from the existing ultra-high performance concrete that generally uses a large amount of silicate cement, the present invention completely eliminates the use of cement and relies entirely on alkali-induced reaction to drive the coagulation and hardening reaction process. It not only reduces CO2 emissions, but also promotes the transformation of blast furnace slag from landfill treatment to high value, providing an industrial closed-loop utilization path for by-products of the steel industry, with significant environmental and economic benefits.

[0011] In addition to the excellent microstructure control capability brought about by the synergistic effect of the selected raw material system, the present invention combines the addition of refined nickel-iron slag regenerated sand and high-performance steel fiber to achieve performance coupling enhancement in three dimensions of strength-density-shielding performance, solving the problems of uneven performance and loose structure in conventional functional concrete systems, and having strong engineering adaptability.

[0012] Furthermore, the alumina-silica precursor comprises 75 to 85 parts by weight of ground blast furnace slag, 10 to 20 parts by weight of fly ash, and 5 to 20 parts by weight of silica fume.

[0013] On the basis of the synergistic reaction of multi-source siliceous and aluminous solid wastes in the present invention, by setting a specific mass fraction range for the three-component precursors of ground blast furnace slag, fly ash and silica fume, the mutual coordination mechanism between various active components in the system is further strengthened, thereby achieving the organic unity of reaction balance, structural density and performance improvement.

[0014] The present invention limits the amount of ground blast furnace slag to 75-85 parts by weight, ensuring its dominant role as a core participant in the primary gelling reaction. Meanwhile, fly ash is controlled at 10-20 parts, providing a stable source of silicon and aluminum, slowly releasing reaction heat and optimizing reaction continuity. Silica fume, a highly active nanoscale reactive component, is set at 5-20 parts. This ratio avoids system inhomogeneity or reaction competition that can result from arbitrary mixing, enhancing the integrity and stability of the gel structure.

[0015] Blast furnace slag reacts quickly, promoting early strength development; fly ash's hollow spherical particles provide excellent particle size distribution and interfacial transition buffering capabilities; and silica fume, with its extremely fine particle size and high reactivity, fills nanopores and promotes the formation of secondary gels. These three elements complement each other synergistically, creating a high-strength, low-porosity, and low-permeability solid matrix at the microstructure level.

[0016] Furthermore, the alkali activation solution is prepared by mixing 0 to 20 parts by weight of sodium hydroxide and 80 to 100 parts by weight of water glass solution, stirring the mixture, and allowing the mixture to stand and age for 24 hours.

[0017] By clearly defining the sodium hydroxide addition ratio, water glass modulus and aging time, the reaction controllability, structural coordination ability and final performance of the alkali-activated system are significantly improved.

[0018] The present invention effectively regulates the alkali excitation system by controlling the alkali excitation liquid to be a combination of 0 to 20 parts by weight of sodium hydroxide and 80 to 100 parts by weight of water glass, compared with the conventional excitation system using only NaOH or too high modulus water glass. The silicate concentration ratio allows the gelling system to achieve an appropriate pH and reactant concentration gradient, thereby avoiding premature precipitation or uneven coagulation caused by excessive activator concentration and enhancing the gel nucleation rate and growth continuity. A 24-hour aging treatment followed by pre-stirring effectively promotes ion exchange between NaOH and water glass, homogenizing the solution and forming a stable silica polymer. This reduces the free NaOH content, resulting in more controllable reactivity and viscosity behavior of the activating solution during use.

[0019] Unlike single-source slag or fly ash systems, multi-source precursors have varying solubilities and reactivities. Large fluctuations in the reactivity of the stimulating solution can lead to incomplete activation or premature precipitation of some components. The stimulating solution modulus and aging process designed in this invention result in a milder and more tunable stimulating reaction, ensuring the coordinated release of various active phases and significantly improving the overall reaction efficiency and structural density of the material.

[0020] In addition, by regulating the components and aging state of the stimulating liquid, the slurry exhibits better flow stability and castability after mixing, avoiding defects such as bleeding, cracking or rapid reaction of existing concrete caused by unstable viscosity of the stimulating liquid, and improving the controllability of on-site construction and the final molding quality.

[0021] Furthermore, the particle size of the regenerated sand ranges from 0.15 to 4.75 mm.

[0022] By refining the nickel-iron slag to a particle size of 0.15-4.75 mm, especially a median particle size of less than 1 μm, the microporous structure is effectively filled and the bonding force of the interface transition zone between particles is enhanced, thereby not only improving the volume stability of the system, but also making full use of the high iron content in the solid waste to enhance the neutron protection ability of the concrete, realizing "aggregate functionalization", which is different from the current technical status quo where traditional recycled aggregates are only used for filling.

[0023] Furthermore, the shielding reinforcement filler is a compound of lead glass and barite in a mass ratio of 1:1.

[0024] By compounding lead glass and barite in a 1:1 ratio, the composite synergistic effect of high atomic number elements and high-density minerals is effectively achieved. At the same volume dosage, a better linear attenuation coefficient and energy spectrum response range can be obtained, thereby improving the comprehensive shielding capability of concrete under X-rays and gamma rays.

[0025] Lead glass is a typical high-atomic-number material that primarily absorbs low- to mid-energy radiation (30-150 keV) through the photoelectric effect. Barite (primarily composed of BaSO₄) has a high density and dense crystal arrangement, resulting in excellent Compton scattering suppression, which enhances the scattering control of mid- to high-energy radiation (150 keV). Therefore, the combination of the two forms a composite shielding mechanism, enabling the material to maintain a high linear attenuation coefficient across a wide energy range.

[0026] Secondly, due to the differences in particle density, surface morphology and particle size distribution between lead glass and barite, a mutually nested mixed distribution can be effectively formed at a 1:1 mass ratio, avoiding local density unevenness or "stratification" problems caused by the sedimentation of single high-density particles, and enhancing the consistency and long-term stability of the shielding layer structure.

[0027] In addition, barite, as a buffer filler, can improve the microstructure of the interface bonding transition zone and reduce the risk of crack initiation, thereby taking into account both shielding performance and structural strength.

[0028] Furthermore, the steel fiber content is 1.5 to 2.5% by volume.

[0029] Steel fiber additions of 1.5-2.5% by volume can form a dense, three-dimensional bridging network while maintaining good dispersion, significantly suppressing microcracks and enhancing toughness under early concrete shrinkage and load. This setting balances mechanics and construction fluidity, creating an optimal fiber mix ratio window in ultra-high performance concrete, distinct from conventional random trial mixing methods.

[0030] Furthermore, the total porosity of the concrete is no more than 5.5%, of which harmless pores with a pore size of less than 50 nm account for more than 70%.

[0031] Through the synergy of material design and process, the total porosity is controlled below 5.5%, and harmless pores (<50 nm) account for over 70%. This significantly improves the concrete's density, impermeability, and carbonization resistance, while reducing the migration pathways for radioactive particles and water vapor. Compared to conventional high-performance concrete, this technology achieves integrated function-structure control at the microscopic scale, providing a solution for constructing long-term, stable protective structures for nuclear facilities and radiation-sensitive areas.

[0032] A method for preparing the above-mentioned radiation-proof ultra-high performance recycled concrete comprises the following steps: S1: Weigh ground blast furnace slag, fly ash, and silica fume according to the ratio to prepare a silicon-alumina precursor; S2: Sodium hydroxide and water glass are mixed and stirred, and aged for 24 hours to form an alkaline excitation solution; S3: Add the silica-alumina precursor, alkali activation solution, regenerated sand, shielding reinforcement filler and steel fiber into a mixer, stir at 10-50 r / min for 1-3 minutes, and then stir at 100-200 r / min for 1-3 minutes to obtain a mixed slurry; S4: Place the slurry at 20±2℃ and 95%±3% relative humidity for preliminary curing to form a hardened body.

[0033] Multi-source aluminosilicate precursors (ground blast furnace slag, fly ash, and silica fume) exhibit varying activity release rates, leading to uneven reaction zones if not fully mixed. This step involves low-speed pre-mixing at 10-50 r / min to achieve primary wetting and physical encapsulation between the water glass-based activating liquid and the precursor materials. High-speed shearing at 100-200 r / min then disrupts particle agglomeration, promoting the deep distribution of spherical fly ash particles and nanoscale silica fume within the slag skeleton. This achieves a homogenized spatial structure and facilitates the construction of a dense, multi-scale, synergistic CASH / NASH gel network during the hardening process. Furthermore, the high-speed shearing stage allows the steel fibers to fully unfold in random orientation within the slurry, forming a fiber-matrix interface transition zone with the cementitious material and establishing multi-point anchoring bridges, effectively improving the overall crack resistance and toughness of the composite.

[0034] Secondly, the formation of CASH and NASH gels in the system requires a sufficient moist and hot environment to promote mid-term cross-linking and structural transformation. Setting a constant temperature and high humidity condition of 20±2℃ and 95%±3%RH is conducive to the release of SiO4 4- Continuous polymerization stimulates the secondary reaction of the Si / Al skeleton in the fly ash, strengthens the dense cross-linking of the internal gel, and forms a spatial network with high strength and low porosity.

[0035] Under high humidity conditions, the evaporation rate of water is controlled, suppressing the concentration of capillary stress during the slurry shrinkage process, thereby reducing the probability of microcrack formation. In particular, based on the uniform distribution of copper-coated steel fibers, early cracks are effectively passivated, and stress is released through the fiber-matrix cooperative deformation mechanism, ultimately achieving structural properties with high crack resistance and low creep.

[0036] The interfacial strength between shielding filler particles and the matrix plays a key role in radiation protection performance. High-humidity curing provides favorable conditions for interfacial recondensation, allowing a thin layer of cementing phase to form around the lead glass and barite. This strengthens their embedding stability within the hardened matrix, prevents particle loosening or delamination, and improves the shielding stability and lifespan of the material under high-radiation conditions.

[0037] Furthermore, after the initial curing is completed, the mold is removed and the curing is continued for 3 to 28 days under the same temperature and humidity conditions.

[0038] By continuing to cure in a high-humidity, constant-temperature environment for 3 to 28 days after demolding, the secondary formation of amorphous gel and pore filling are further promoted, effectively reducing the risk of shrinkage cracking in later stages and improving durability. This strategy significantly outperforms traditional 7-day or 14-day curing cycles, optimizing long-term performance while maintaining early strength.

[0039] Furthermore, the mixed slurry is poured within 60 minutes after stirring.

[0040] By explicitly requiring the slurry to be poured within 60 minutes of mixing, premature setting of the binder system during the alkali-induced reaction is avoided, ensuring slurry fluidity and compactness. Compared to existing concrete preparation methods that don't control pouring time, this solution significantly reduces the risk of structural defects and interface delamination, improving overall project quality.

[0041] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects: Green construction of zero-cement system: The present invention does not use silicate cement at all. Instead, a cementitious structure is formed by the reaction of multi-source siliceous and aluminous solid waste with alkali-activated liquid, which significantly reduces carbon emissions.

[0042] This invention utilizes a green cementitious system based on a multi-source silica-alumina precursor and an alkaline-activated solution, integrating a high-density aggregate structure with a synergistic radiation-shielding filler. This system achieves comprehensive improvements in concrete's mechanical properties, radiation protection, and durability without the use of Portland cement. This system fully utilizes industrial solid waste resources, resulting in lower carbon emissions and resource consumption. It also offers excellent structural density, crack resistance, and radiation shielding capabilities, demonstrating excellent environmental adaptability and engineering value. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the embodiments.

[0044] Example 1 Materials preparation: (1) Silicon-aluminum precursor raw materials: 75 parts of ground blast furnace slag (specific surface area of ​​about 420 m² / kg); 20 parts of fly ash; 5 parts of silica fume; The three materials are dry-mixed and used as a composite precursor.

[0045] (2) Alkali activation solution: Weigh 10 parts by weight of sodium hydroxide particles and add 90 parts by weight of industrial water glass solution with an initial modulus of 3.0 (SiO2 / Na2O mass ratio of 3.0); The mixture was stirred in a magnetic stirrer for 30 minutes to form a uniform alkaline solution, and then allowed to stand and age for 24 hours to form a stable alkaline excitation solution.

[0046] (3) Regenerated sand: The nickel-iron slag was crushed and sieved by a jaw crusher to prepare regenerated sand with a particle size range of 0.15 to 4.75 mm and a median particle size of less than 1 μm, totaling 100 parts.

[0047] (4) Shielding reinforcement filler: Lead glass and barite are compounded in a mass ratio of 1:1, totaling 15 parts.

[0048] (5) Steel fiber: Straight copper-plated steel fibers with a diameter of 0.12 mm, a length of 13 mm, and a tensile strength of not less than 2000 MPa are used, with the addition amount being 2% of the total volume of concrete.

[0049] This embodiment provides a method for preparing radiation-proof ultra-high performance recycled concrete, comprising the following steps: S1: Weighed ground blast furnace slag, fly ash and silica fume are premixed in a dry state.

[0050] Use a horizontal forced dry powder mixer or a three-dimensional motion mixer for 2-5 minutes to ensure the three components are fully dispersed and their particle sizes are complementary, which improves the subsequent encapsulation and reaction uniformity of the alkaline activating solution. During the mixing process, be careful to avoid agglomerations. If necessary, use a screen to help break up agglomerates to obtain a uniformly composed silicon-aluminum precursor powder.

[0051] S2: Add the appropriate amount of sodium silicate solution to an alkali-resistant container. Start the stirring device and slowly add sodium hydroxide granules while stirring continuously (to avoid localized excessive concentration and resulting in sticky clumping). Continue stirring until the sodium hydroxide is completely dissolved and the liquid is clear or slightly turbid. Stir for at least 30 minutes. After stirring, seal the container and allow it to age at room temperature for 24 hours. Stir again before use to ensure uniform viscosity.

[0052] S3: Add the silicon-aluminum precursor, the screened nickel-iron slag regenerated sand, the premixed shielding reinforcement filler and the steel fiber into a horizontal or vertical forced mixer in sequence.

[0053] Finally, slowly add the aged alkaline activating solution, start the mixer, and begin the two-stage stirring process: The first stage (low-speed premixing): Mix at 50 r / min for 2 minutes to complete the initial wetting, aggregate coating and coarse distribution; The second stage (high-speed shear): switch to 150 r / min and continue stirring for 2 minutes to break up any agglomerates and achieve fine-scale uniform dispersion of fillers, fibers and matrix.

[0054] S4: After mixing, pour the concrete paste into the mold within 60 minutes. During the process, light vibration or tamping can be used to remove bubbles and improve the compaction density. Then, perform preliminary curing for 26 hours at 20±2℃ and 95%±3% relative humidity. After demoulding, continue to cure under the same conditions for up to 28 days.

[0055] The difference between Examples 2 to 4 and Example 1 is that the proportions of the components in the silicon-aluminum precursor are different, as shown in Table 1 below.

[0056] Table 1 The differences between Examples 5 to 10 and Example 1 are the amount of alkali activation solution added, the ratio of sodium hydroxide to water glass in the alkali activation solution, and the initial modulus of the water glass, as shown in Table 2 below.

[0057] Table 2 The difference between Example 11 and Example 1 is that the shielding reinforcement filler is only lead glass.

[0058] The difference between Example 12 and Example 1 is that the shielding reinforcement filler is only barite.

[0059] The difference between Example 13 and Example 1 is that the shielding reinforcement filler is only iron ore.

[0060] The difference between Example 14 and Example 1 is that the steel fiber content is 1% of the total volume of concrete.

[0061] The difference between Example 15 and Example 1 is that the steel fiber content is 3% of the total volume of concrete.

[0062] The difference between Example 16 and Example 1 is that in step S3, the stirring procedure is to adopt 120 r / min and continue stirring for 4 minutes.

[0063] The difference between Comparative Example 1 and Example 1 is that no steel fiber is added.

[0064] The difference between Comparative Example 2 and Example 1 is that the ground blast furnace slag, fly ash and silica fume in the alumina-silica precursor are 30 parts by weight, 40 parts by weight and 40 parts by weight, respectively.

[0065] The difference between Comparative Example 3 and Example 1 is that after the mixing is completed in step S4, the concrete slurry is poured into the mold after waiting for 70 minutes.

[0066] Detection method 1. Compressive strength test method: (1) Cure standard-sized (100 mm × 100 mm × 100 mm) cubic specimens to the specified age (3 days, 28 days); (2) Use an electric hydraulic pressure testing machine to apply axial pressure at a loading rate of 0.5 MPa / s and record the maximum load at failure; (3) Calculate the compressive strength (MPa) based on the failure load and the compressive area.

[0067] 2. Flexural strength method: (1) Prepare a beam specimen of 100 mm × 100 mm × 400 mm and cure it to the age; (2) Using the three-point loading method, load at a rate of 0.05 MPa / s on an electronic universal testing machine until fracture; (3) Calculate the flexural strength σ = (3FL) / (2bh²).

[0068] 3. Linear attenuation coefficient method: (1) Prepare the concrete specimen into a Φ50 mm × 10 mm cylinder or equivalent thin slice; (2) Using an X-ray detection system (energy range 30-200 keV), measure the incident intensity I0 and the post-penetration intensity I under different energy conditions; (3) Calculated according to the Beer–Lambert law: μ = ln(I0 / I) / x; (4) The results are expressed as linear attenuation coefficient intervals (unit: 1 / cm).

[0069] The linear attenuation coefficient μ is given in the form of "low energy end ~ high energy end", indicating the range of linear attenuation coefficient under the test energy range of 30 ~ 200 keV, so as to reflect the comprehensive protection capability of the material in the wide spectrum radiation field.

[0070] 4. Pore structure characteristics method: (1) Take a cubic concrete specimen after 28 days of curing and dry it to constant weight; (2) Use a mercury intrusion porosimeter (such as PoreMaster GT60) to measure the pore size distribution in the pressure range of 0.1 to 400 MPa; (3) Analysis of total porosity (%) and the proportion of each pore size segment (≤20 nm, 20–50 nm, 50–200 nm, ≥200 nm); (4) The results are used to characterize the microstructural density and harmless pore ratio of the material.

[0071] The above test results are shown in Table 3, Table 4 and Table 5.

[0072] Table 3 Table 4 Table 5 The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A radiation-proof ultra-high performance recycled concrete, characterized in that: Composition according to the following parts by weight: 90-125 parts of silicon-aluminum precursor; 30-70 parts of alkali activation solution; 90-110 parts of regenerated sand; 14 to 16 parts of shielding reinforcement filler; Steel fiber 1% to 3% volume content; Wherein, the silicon-alumina precursor is composed of one or more of ground blast furnace slag, fly ash or silica fume; The alkali activation solution is obtained by mixing sodium hydroxide and water glass with an initial modulus of 2.6 to 3.6 and allowing to stand for aging; The regenerated sand is nickel-iron slag with a median particle size of less than 1 μm after screening; The shielding reinforcement filler includes lead glass, barite and / or iron ore; The steel fiber is a straight copper-plated steel fiber with a diameter of 0.1 to 0.15 mm, a length of 10 to 15 mm, and a tensile strength of ≥2000 MPa.

2. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The alumina-silica precursor comprises 75-85 parts by weight of ground blast furnace slag, 10-20 parts by weight of fly ash, and 5-20 parts by weight of silica fume.

3. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The alkali activation solution is prepared by mixing 0 to 20 parts by weight of sodium hydroxide and 80 to 100 parts by weight of water glass solution, stirring the mixture, and allowing the mixture to stand and age for 24 hours.

4. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The particle size of the regenerated sand ranges from 0.15 to 4.75 mm.

5. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The shielding reinforcement filler is a mixture of lead glass and barite in a mass ratio of 1:

1.

6. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The steel fiber content is 1.5-2.5% by volume.

7. The radiation-proof ultra-high performance recycled concrete according to claim 1, characterized in that: The total porosity of the concrete is no more than 5.5%, of which harmless pores with a pore size of less than 50 nm account for more than 70%.

8. A method for preparing radiation-proof ultra-high performance recycled concrete according to any one of claims 1 to 7, characterized in that: The steps include: S1: Weigh ground blast furnace slag, fly ash, and silica fume according to the ratio to prepare a silicon-alumina precursor; S2: Sodium hydroxide and water glass are mixed and stirred, and aged for 24 hours to form an alkaline excitation solution; S3: Put the silicon-aluminum precursor, alkaline activating solution, regenerated sand, shielding reinforcement filler and steel fiber into a mixer, first stir at 10-50 r / min for 1-3 minutes, then stir at 100-200 r / min for 1-3 minutes to obtain a mixed slurry; S4: Place the slurry at 20±2℃ and 95%±3% relative humidity for preliminary curing to form a hardened body.

9. The method for preparing radiation-proof ultra-high performance recycled concrete according to claim 8, characterized in that: After the initial curing is completed, the mold is removed and curing is continued for 3 to 28 days under the same temperature and humidity conditions.

10. The method for preparing radiation-proof ultra-high performance recycled concrete according to claim 8, characterized in that: The mixed slurry was poured within 60 minutes after stirring.

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