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

Abstract

The present application relates to a kind of anti-radiation super high performance recycled concrete and its preparation method, belong to building material and solid waste resource utilization technical field.The concrete is the synergistic reaction of the multi-source silicon-aluminum precursor of the main ground blast furnace slag and alkali activation liquid, does not contain Portland cement, combined with the nickel iron slag recycled sand of particle size refinement, the shielding reinforcing filler (lead glass and barite) of compound and high-performance copper-plated steel fiber, form dense structure and excellent mechanics, durability and radiation protection performance.The method realizes the high-value reuse of industrial solid waste, has excellent green environmental protection, engineering adaptability and long-term stability, is suitable for nuclear facilities, radioactive sites and other high protection demand scenarios.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and in particular to a preparation method of a radiation-proof super high-performance recycled concrete. BACKGROUND

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

[0003] Super high-performance concrete is a cement-based composite material with super high mechanical properties and excellent durability, and is the most innovative cement-based engineering material in the past few decades. However, the production of super high-performance concrete is limited to a certain extent by the problems of large amount of cementitious material, high energy consumption, etc., which is contrary to the concept of low-carbon cement-based engineering materials. Alkali-activated cementitious material is a new type of green cementitious material prepared by using aluminum silicate active raw materials and alkali activator. Alkali-activated cementitious material has high early strength, dense microstructure, excellent high-temperature resistance and corrosion resistance, and at the same time realizes the high-value utilization of industrial waste, and is considered as one of the most promising low-carbon cementitious materials. Combined with the early strength and dense characteristics of alkali-activated cementitious material, it can meet the development needs of engineering materials with super high strength and excellent durability to the greatest extent, and has the potential to develop and produce super high-performance concrete. At the same time, the fine aggregate used in the current super high-performance concrete is mainly quartz sand, which causes resource shortage and high cost due to excessive concentration of resource acquisition channels, which is not conducive to the development and promotion of super high-performance concrete. The high iron content in the steel fiber and nickel-iron slag recycled sand has the function of shielding neutrons, and when used in cooperation with shielding and reinforcing fillers, the radiation-proof performance of the material can be effectively improved. In addition, the use of solid waste to prepare recycled sand that meets the grading requirements to prepare radiation-proof super high-performance recycled concrete not only reduces the production cost and energy consumption, but also realizes the recycling of solid waste resources. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of a radiation-proof super high-performance recycled concrete.

[0005] A radiation-proof super high-performance recycled concrete is composed of the following components in parts by weight:

[0006] Silico-alumina precursor 90-125 parts;

[0007] Alkali-activated liquid 30-70 parts;

[0008] Recycled sand 90-110 parts;

[0009] Shielding and reinforcing filler 14-16 parts;

[0010] Steel fiber 1%~3% volume fraction;

[0011] The silico-alumina precursor is composed of one or more of ground blast furnace slag, fly ash or silica ash;

[0012] The alkali activation liquid is obtained by mixing sodium hydroxide and water glass with an initial modulus of 2.6~3.6 and standing and aging;

[0013] The regenerated sand is nickel-iron slag with a medium particle size of less than 1 mu m after screening;

[0014] The shielding reinforcing filler includes lead glass, barite and / or iron ore;

[0015] The steel fiber is a flat copper-plated steel fiber with a diameter of 0.1~0.15 mm, a length of 10~15 mm and a tensile strength of greater than or equal to 2000 MPa.

[0016] The present application introduces a multi-source silico-alumina precursor mainly composed of ground blast furnace slag into the concrete system, and cooperates with the alkali activation liquid with a specific modulus to prepare an ultra-high performance recycled concrete with high mechanical strength, dense structure and excellent radiation protection performance without the participation of Portland cement.

[0017] The ground blast furnace slag has high specific surface area and high potential activity after mechanical activation, and the internally rich CaO, SiO2 and Al2O3 can be quickly released under the action of the alkali activation liquid, so as to form a large amount of C-A-S-H gel and a small amount of N-A-S-H gel, thereby establishing a three-dimensional cementitious framework with high strength and low porosity. Compared with a single fly ash or silica ash system, the ground blast furnace slag provides more abundant Ca source, significantly improves the early strength growth rate and the final compressive performance of the system.

[0018] Secondly, in the activation system constructed in the present application, the blast furnace slag is highly sensitive to alkali ions, and the reaction rate is much faster than that of fly ash and silica ash. The rapid reaction can provide an ion barrier for the subsequent release of low-activity substances, inhibit the pH fluctuation of the system, effectively improve the reaction stability and cementing efficiency of the composite system, and give the material a more optimal density and consistent structure.

[0019] In addition, since the reaction product of the ground blast furnace slag is mainly layered C-A-S-H, it has good space filling and crystal crosslinking ability, which can effectively compensate for the porosity risk brought by the porous recycled aggregate. In the present application, the gel structure formed by the reaction of the ground blast furnace slag with low modulus water glass and NaOH shows extremely high micropore dominance, so that the total porosity of the final material is less than 5.5%, and the harmless pores with a pore size of less than 50 nm account for more than 70%, which is much better than the prior art without introducing slag or using only fly ash system.

[0020] Different from the existing ultra-high performance concrete which generally uses a large amount of Portland cement, the application completely cancels the use of cement and completely relies on alkali-activated reaction to drive the setting and hardening reaction process, thereby not only reducing CO2 emission, but also promoting the transformation of blast furnace slag from landfill treatment to high value, providing an industrial closed-loop utilization path for steel industry byproducts, and having significant environmental protection and economic benefits.

[0021] In addition to the excellent microstructure control ability brought by the selected raw material system, the application further combines the addition of refined nickel-iron slag regenerated sand and high-performance steel fibers to realize the performance coupling enhancement of strength, density and shielding performance in three dimensions, and solves the problems of uneven performance and loose structure in the conventional functional concrete system, and has strong engineering adaptability.

[0022] Further, the siliceous and aluminous precursor includes 75-85 parts by weight of finely ground blast furnace slag, 10-20 parts by weight of fly ash, and 5-20 parts by weight of silica fume.

[0023] On the basis of the multi-source siliceous and aluminous solid waste synergistic reaction in the application, by setting specific mass fraction ranges for the three-component precursor of finely ground blast furnace slag, fly ash and silica fume, the mutual coordination mechanism between various active components in the system is further strengthened, and the organic unity of reaction balance, structure density and performance improvement is realized.

[0024] The application limits the finely ground blast furnace slag to 75-85 parts by weight, ensuring that it participates in the reaction as the main gelling reaction core participant and occupies the reaction advantage; at the same time, the fly ash is controlled at 10-20 parts to provide a stable Si and Al source, release reaction heat and optimize reaction sustainability; the silica fume is set at 5-20 parts as a highly active nanoscale reaction component that can promote the generation of gel nuclei, fill micropores and improve the structural continuity in the early stage. This ratio structure avoids the non-uniformity or reaction competition that may be caused by arbitrary mixing, and enhances the integrity and stability of the gel structure.

[0025] The blast furnace slag has a fast reaction rate, which is beneficial to the formation of early strength; the hollow spherical particles in the fly ash have good particle grading and interface transition buffering capacity; the silica fume has an extremely fine particle size and high reaction activity, which can fill nanopores and promote the generation of secondary gel. The three complement each other and jointly build a high-strength, low-porosity and low-permeability solid matrix in the microstructure.

[0026] Further, the alkali-activated liquid is prepared by mixing and stirring 0-20 parts by weight of sodium hydroxide with 80-100 parts by weight of water glass solution, and standing for 24 hours.

[0027] By clearly limiting the addition ratio of sodium hydroxide, the modulus of water glass and the aging time, the reaction control, structure adjustment ability and final performance of the alkali-activated system are significantly improved.

[0028] The present application effectively controls the modulus of the alkali-activated solution to 0-20 parts by weight of sodium hydroxide and 80-100 parts by weight of water glass, compared with the conventional activation system using NaOH or excessively high modulus water glass alone, effectively controls The ratio of the silicate concentration is controlled to obtain a suitable pH and reactant concentration gradient for the gel system, thereby avoiding early precipitation or uneven condensation caused by excessive concentration of the activator, and enhancing the gel nucleation rate and continuity. The pre-mixing and aging for 24 hours effectively promotes the ion exchange between NaOH and water glass and the uniformity of the solution, forms a stable silicon-oxygen polymer, and reduces the free NaOH content, so that the activation solution has more controllable reaction activity and viscosity behavior when used.

[0029] Unlike single slag or fly ash systems, the solubility and reactivity of multiple source precursors are different. If the reactivity of the activation solution fluctuates greatly, it is easy to cause insufficient activation or early precipitation of some components. The modulus and aging process of the activation solution in the present application make the activation reaction more moderate and the process adjustable, ensuring the coordinated release of various active components, and significantly improving the overall reaction efficiency and structural density of the material.

[0030] In addition, by adjusting the components of the activation solution and the aging state, the slurry shows better flow stability and workability after mixing, avoiding the defects such as bleeding, cracking or rapid reaction of existing concrete caused by unstable viscosity of the activation solution, and improving the controllability of on-site construction and the final forming quality.

[0031] Further, the particle size of the recycled sand is 0.15-4.75 mm.

[0032] By refining the nickel-iron slag to a particle size of 0.15-4.75 mm, especially with a median particle size of less than 1 μm, the microporous structure is effectively filled and the bonding force of the interfacial 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 solid waste to improve the neutron shielding ability of the concrete, realizing the "functionalization of aggregate", which is different from the current technical situation of traditional recycled aggregate only used for filling.

[0033] Further, the shielding and reinforcing filler is a 1:1 mixture of lead glass and barite by mass.

[0034] By mixing lead glass and barite at a ratio of 1:1, the composite synergistic effect of high atomic number elements and high density minerals is effectively realized, and better linear attenuation coefficient and energy spectrum response range can be obtained at the same volume dosage, improving the comprehensive shielding ability of the concrete under x-ray and γ-ray.

[0035] Lead glass is a typical high-atomic-number material, which mainly absorbs low-energy radiation (30-150 keV) through photoelectric effect; while barite (main component BaSO4) has high density and compact crystal arrangement, and has excellent Compton scattering suppression capability, which can enhance the scattering control of medium-high energy radiation (150 keV). Therefore, the combination of the two can form a composite shielding mechanism, so that the material can maintain a high linear attenuation coefficient under a wide range of energy.

[0036] Secondly, due to the differences in particle density, surface morphology and particle size distribution between lead glass and barite, a mutual nesting mixed distribution can be effectively formed under a mass ratio of 1:1, avoiding the problem of local density unevenness or "layering" caused by the settlement of single high-density particles, and enhancing the consistency and long-term stability of the shielding layer structure.

[0037] In addition, as a buffer filler, barite can improve the microstructure of the interface bonding transition zone and reduce the risk of crack initiation, thereby balancing the shielding performance and structural strength.

[0038] Further, the steel fiber content is 1.5-2.5% by volume.

[0039] 1.5-2.5% by volume of steel fiber can form a dense three-dimensional bridging network structure under the premise of maintaining good dispersibility, and play a significant role in inhibiting micro-cracks and enhancing toughness under early shrinkage and load of concrete. This setting takes into account the mechanics and construction fluidity, forming an optimal fiber ratio window in ultra-high performance concrete, which is different from the conventional random trial mixing mode.

[0040] Further, the total porosity of the concrete is not more than 5.5%, and the harmless pores with a pore size of less than 50 nm account for more than 70%.

[0041] Through material design and process coordination, the total porosity is controlled to be less than 5.5%, and the harmless pores (<50 nm) account for more than 70%, which significantly improves the compactness and carbonation resistance of the concrete, and reduces the migration channels of radiation particles and water vapor. Compared with conventional high-performance concrete, this technology realizes functional-structural integrated control at the microstructure scale, providing a solution for building long-term stable protective structures for nuclear facilities and radiation-sensitive areas.

[0042] A preparation method of the above-mentioned radiation-proof ultra-high performance recycled concrete, comprising the following steps:

[0043] S1: Prepare a silico-alumina precursor by weighing and mixing ground blast furnace slag, fly ash and silica fume according to the ratio;

[0044] S2: Mix sodium hydroxide and water glass and stir, and form an alkali-activated liquid after aging for 24 hours;

[0045] S3: Put the siliceous and aluminous precursor, alkali activator, recycled sand, shielding and reinforcing filler and steel fiber into the mixer, first 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;

[0046] S4: The slurry is placed in a 20±2℃, 95%±3% relative humidity environment for preliminary curing to form a hardened body.

[0047] The multi-source siliceous and aluminous precursor (ground blast furnace slag, fly ash, silica fume) has different active release rates, and if not mixed well, it can easily lead to uneven reaction areas. This step uses low-speed pre-stirring at 10-50 r / min to form primary wetting and physical wrapping of the water glass-based activator and the precursor material. Then, high-speed shearing at 100-200 r / min breaks the particle agglomeration state, promotes the deep distribution of fly ash spherical particles and nano-silica between the slag framework, and realizes the uniformization of the spatial structure hierarchy, which is conducive to building a dense and multi-scale collaborative C-A-S-H / N-A-S-H gel network during the hardening process. Moreover, the high-speed shearing stage can make the steel fiber randomly oriented and fully expanded in the slurry, forming a fiber-matrix interface transition zone with the cementitious material and establishing a multi-point anchoring bridge, effectively improving the overall crack resistance and toughness of the composite material.

[0048] Secondly, the formation of C-A-S-H and N-A-S-H gel in the system requires sufficient humid environment to promote the intermediate crosslinking and structure transformation. Setting a constant temperature and high humidity condition of 20±2℃, 95%±3% RH helps the SiO4 4- continuous polymerization, while stimulating the secondary reaction of Si / Al skeleton in fly ash, strengthening the dense crosslinking of internal gel, and forming a spatial network with high strength and low porosity.

[0049] Under high humidity conditions, the water evaporation rate is controlled, which inhibits the capillary stress concentration in the shrinkage process of the slurry, thereby reducing the probability of micro-crack generation. Especially on the basis of uniform distribution of copper-coated steel fibers, early cracks are effectively passivated, and stress release is achieved through the fiber-matrix collaborative deformation mechanism, ultimately obtaining high crack resistance and low creep structural performance.

[0050] The interfacial strength between shielding filler particles and the matrix plays a key role in radiation protection performance. High humidity curing provides good conditions for interfacial recondensation reactions, allowing a thin layer of cemented phase to form around the lead glass and heavy spar, enhancing its embedded stability in the hardened body, preventing particle "loosening" or delamination, and improving the shielding stability and life of the material under high radiation conditions.

[0051] Further, after the preliminary curing is completed, the mold is removed, and the curing is continued for 3-28 days under the same temperature and humidity conditions.

[0052] By continuing to maintain in a high-humidity constant-temperature environment for 3-28 days after demolding, the secondary generation of amorphous gel and the filling of pores are further promoted, the risk of late drying shrinkage cracks is effectively reduced, and the durability is improved. This strategy is obviously better than the traditional 7-day or 14-day curing cycle. On the basis of ensuring early strength, the long-term service performance is optimized.

[0053] Further, the mixed slurry is completed pouring within 60 minutes after completion of stirring.

[0054] By explicitly limiting the pouring time of the slurry within 60 minutes after completion of stirring, the binder system can be prevented from prematurely setting during the alkali activation reaction, ensuring the flowability and compaction density of the slurry. Compared with existing concrete preparation schemes that do not control the pouring time, this scheme significantly reduces the structural defect rate and interface peeling risk, improving the overall engineering quality.

[0055] Compared with the prior art, the beneficial effects of the present application mainly lie in the following aspects:

[0056] Zero-cement green construction: The present application does not use Portland cement at all. By reacting multi-source silicon-aluminum solid waste with alkali activation liquid to form a cementing structure, carbon emissions are significantly reduced.

[0057] By constructing a green cementitious system based on multi-source silicon-aluminum precursors and alkali activation liquid, and integrating high-density aggregate structure and synergistic radiation shielding filler, the present application achieves comprehensive improvement of the mechanical properties, radiation shielding properties and durability of concrete without using Portland cement. This system makes full use of industrial solid waste resources, has lower carbon emissions and resource consumption, and has excellent structural density, crack resistance and radiation shielding ability, showing good environmental adaptability and engineering promotion value. DETAILED DESCRIPTION

[0058] The present application will be described in detail below with reference to examples.

[0059] Example 1

[0060] Material preparation:

[0061] (1) Silicon-aluminum precursor raw materials:

[0062] Ground blast furnace slag 75 parts (specific surface area about 420 m² / kg);

[0063] Fly ash 20 parts;

[0064] Silica fume 5 parts;

[0065] The above three materials are dry mixed uniformly and used as composite precursors.

[0066] (2) Alkali activation liquid:

[0067] Weigh 10 parts of sodium hydroxide particles, and add 90 parts of an initial modulus of 3.0 water glass solution (SiO2 / Na2O mass ratio of 3.0);

[0068] After stirring for 30 minutes in a magnetic stirrer, a uniform alkali solution is formed, and then it is left to stand and age for 24 hours to form a stable alkali-activated solution.

[0069] (3) Recycled sand:

[0070] The nickel-iron slag is crushed by a jaw crusher and sieved to prepare recycled sand with a particle size range of 0.15-4.75 mm and a median particle size of less than 1 μm, accounting for 100 parts.

[0071] (4) Shielding and reinforcing filler:

[0072] The lead glass and barite are compounded in a mass ratio of 1:1, accounting for 15 parts in total.

[0073] (5) Steel fiber:

[0074] A flat copper-plated steel fiber with a diameter of 0.12 mm, a length of 13 mm, and a tensile strength of not less than 2000 MPa is used, and the dosage is 2% of the total volume of the concrete.

[0075] The embodiment provides a kind of preparation method of radiation-proof ultra-high performance recycled concrete, comprising the following steps:

[0076] S1: the finely ground blast furnace slag, fly ash and silica ash weighed are pre-mixed in a dry state.

[0077] Mix for 2-5 minutes using a horizontal forced dry powder mixer or a three-dimensional motion mixer to ensure that the three components are fully dispersed, the particle sizes are complementary, and the subsequent alkali activation solution is improved in terms of encapsulation and reaction uniformity. During the mixing process, attention should be paid to avoid clumping, and if necessary, a screen can be used to assist in breaking up the agglomerates, resulting in a uniformly composed silica-alumina precursor powder.

[0078] S2: In an alkali-resistant container, add water glass solution in proportion, start the stirring device, and slowly add sodium hydroxide particles under continuous stirring (avoid local concentration too high causing sticky clumps). Continue stirring until all the sodium hydroxide is dissolved, and the liquid appears clear or slightly turbid. The total stirring time is not less than 30 minutes. After completing the stirring, seal and age at room temperature for 24 hours. Stir again before use to ensure uniform viscosity.

[0079] S3: Add the silica-alumina precursor, the sieved nickel-iron slag recycled sand, the pre-mixed shielding and reinforcing filler, and the steel fiber into a horizontal or vertical forced stirrer in sequence.

[0080] Finally, the aged alkali activator solution is added slowly, and the stirrer is started to begin the two-stage stirring procedure:

[0081] First stage (low speed premixing): 50 r / min for 2 minutes, mainly to complete the initial wetting, aggregate coating and coarse distribution;

[0082] Second stage (high speed shearing): switch to 150 r / min, continue stirring for 2 minutes, break up the possible agglomerates, and achieve fine-scale uniform dispersion of fillers, fibers and matrix.

[0083] S4: The stirred concrete slurry is poured into the mold within 60 minutes, and light vibration or tamping can be used to remove air bubbles and improve the molding density during the process. Then, the preliminary curing is carried out at 20±2℃ and 95%±3% relative humidity for 26 hours;

[0084] After demolding, continue to cure under the same conditions for 28 days.

[0085] Examples 2-4 differ from Example 1 in that the proportions of the components in the silico-alumina precursor are different, as shown in Table 1 below.

[0086] Table 1

[0087]

[0088] Examples 5-10 differ from Example 1 in that the amount of alkali activator solution added, the ratio of sodium hydroxide to water glass in the alkali activator solution, and the initial modulus of the water glass are different, as shown in Table 2 below.

[0089] Table 2

[0090]

[0091] Example 11 differs from Example 1 in that the shielding and reinforcing filler is only lead glass.

[0092] Example 12 differs from Example 1 in that the shielding and reinforcing filler is only barite.

[0093] Example 13 differs from Example 1 in that the shielding and reinforcing filler is only iron ore.

[0094] Example 14 differs from Example 1 in that the steel fiber content is 1% of the total volume of the concrete.

[0095] Example 15 differs from Example 1 in that the steel fiber content is 3% of the total volume of the concrete.

[0096] Example 16 differs from Example 1 in that in step S3, the stirring procedure is 120 r / min for 4 minutes.

[0097] The difference between Comparative Example 1 and Example 1 is that no steel fiber is added.

[0098] The difference between Comparative Example 2 and Example 1 is that in the silico-alumina precursor, the ground blast furnace slag is 30 parts by weight, the fly ash is 40 parts, and the silica ash is 40 parts.

[0099] The difference between Comparative Example 3 and Example 1 is that after the stirring in step S4 is completed, the concrete slurry is poured into the mold after waiting for 70 minutes.

[0100] Detection method

[0101] 1. Compressive strength test

[0102] Method:

[0103] (1) The standard size (100 mm × 100 mm × 100 mm) cubic test piece is cured to the specified age (3 days, 28 days);

[0104] (2) An electric hydraulic pressure testing machine is used to apply axial pressure at a loading rate of 0.5 MPa / s, and the maximum load at failure is recorded;

[0105] (3) The compressive strength (MPa) is calculated according to the failure load and the pressure area.

[0106] 2. Flexural strength

[0107] Method:

[0108] (1) A beam-shaped test piece of 100 mm × 100 mm × 400 mm is prepared and cured to the age;

[0109] (2) The three-point loading method is used to load to fracture on an electronic universal testing machine at a rate of 0.05 MPa / s;

[0110] (3) The flexural strength σ = (3FL) / (2bh²) is calculated.

[0111] 3. Linear attenuation coefficient

[0112] Method:

[0113] (1) The concrete test block is prepared into a Φ50 mm × 10 mm cylinder or an equivalent sheet;

[0114] (2) An X-ray detection system (energy range 30-200 keV) is used to measure the incident intensity I0 and the intensity I after penetration under different energy conditions;

[0115] (3) Calculate according to Beer-Lambert law: μ = ln(I0 / I) / x;

[0116] (4) Results are expressed as linear attenuation coefficient interval (unit: 1 / cm).

[0117] Linear attenuation coefficient μ is given in the form of "low-energy end ~ high-energy end", indicating the linear attenuation coefficient range under the condition of 30-200 keV test energy range, to reflect the comprehensive protection ability of the material in the wide spectrum radiation field.

[0118] 4. Pore structure characteristics

[0119] Method:

[0120] (1) Take the cubic concrete test block after 28 days of curing, dry to constant weight;

[0121] (2) Use a mercury porosimeter (such as PoreMaster GT60) to test the pore size distribution in the pressure range of 0.1-400 MPa;

[0122] (3) Analyze the total porosity (%) and the proportion of each pore size range (≤20 nm, 20-50 nm, 50-200 nm, ≥200 nm);

[0123] (4) The results are used to characterize the microstructure density and harmless pore proportion of the material.

[0124] The above test results are shown in Tables 3, 4, and 5.

[0125] Table 3

[0126]

[0127] Table 4

[0128]

[0129] Table 5

[0130]

[0131] The above only describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical solutions falling within the concept of the present application shall be considered as falling within the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also be considered as falling within the protection scope of the present application.

Claims

1. A radiation-resistant ultra-high performance recycled concrete, characterized in that, Composed of the following parts by weight: 90–125 parts of aluminosilicate precursor; 30-70 parts of alkali activation solution; 90-110 parts recycled sand; 14-16 parts of shielding reinforcement filler; Steel fiber volume content of 1% to 3%; The silica-aluminate precursor comprises 75-85 parts by weight of finely ground blast furnace slag, 10-20 parts by weight of fly ash, and 5-20 parts by weight of silica fume. The alkaline activation solution is obtained by mixing sodium hydroxide with water glass with an initial modulus of 2.6 to 3.6 and allowing it to stand and age. The recycled 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 0.1-0.15 mm, a length of 10-15 mm, and a tensile strength of ≥2000 MPa.

2. The radiation-resistant ultra-high performance recycled concrete according to claim 1, characterized in that, The alkaline activation solution is prepared by mixing and stirring 0-20 parts by weight of sodium hydroxide with 80-100 parts by weight of water glass solution, and then allowing it to stand and age for 24 hours.

3. The radiation-resistant ultra-high performance recycled concrete according to claim 1, characterized in that, The particle size range of the recycled sand is 0.15 to 4.75 mm.

4. The radiation-resistant 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.

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

6. The radiation-resistant 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 diameter of less than 50 nm account for more than 70%.

7. A method for preparing radiation-resistant ultra-high performance recycled concrete according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Weigh and grind blast furnace slag, fly ash and silica fume according to the proportions to prepare a silica-alumina precursor; S2: Sodium hydroxide and water glass are mixed and stirred, and aged for 24 hours to form an alkaline activation solution; S3: Add the silica-alumina precursor, alkali activation solution, recycled sand, shielding reinforcement filler and steel fiber into the mixer, 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 initial curing to form a hardened body.

8. The method for preparing radiation-resistant ultra-high performance recycled concrete according to claim 7, characterized in that, After the initial curing is completed, the mold is removed, and the mold is continued to be cured for 3 to 28 days under the same temperature and humidity conditions.

9. The method for preparing radiation-resistant ultra-high performance recycled concrete according to claim 7, characterized in that, The mixed slurry was poured within 60 minutes after mixing.

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