Steel slag-slag composite micro-powder green low-carbon concrete and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and particularly discloses steel slag-slag composite micro powder green low-carbon concrete and a preparation method thereof. The steel slag-slag composite micropowder green low-carbon concrete is prepared from the following raw materials in parts by weight: 25-35 parts of modified steel slag microspheres, 20-30 parts of slag micropowder, 10-15 parts of cement, 30-40 parts of coarse aggregate, 1.2-2 parts of an additive and 18-30 parts of water, the steel slag microspheres are porous steel slag microspheres, an exciting agent is loaded in pores of the steel slag microspheres, and a phase change material is packaged in the pores of the steel slag microspheres; the preparation method comprises the following steps: mixing and dry-mixing the modified steel slag microspheres, the slag micro-powder and the cement, adding the coarse aggregate and the water, uniformly stirring, adding the additive, and uniformly stirring to obtain the steel slag-slag composite micro-powder green low-carbon concrete. The composition can be used in the fields of building structures, road engineering, marine facilities and the like, and has the advantages of high early strength and good mechanical properties.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and more specifically, to a steel slag-slag composite micro-powder green and low-carbon concrete and a preparation method thereof. Background Art

[0002] With the rapid development of the global construction industry, as one of the most important building materials, the demand for concrete continues to climb. Traditional concrete uses cement as the main binder, but a large amount of energy is consumed and a large amount of carbon dioxide is emitted during the cement production process. According to statistics, about 0.8 - 1 ton of carbon dioxide is emitted per ton of cement produced, which brings great pressure to the global environment. In this context, the development of green and low-carbon building materials has become an industry consensus. Among them, using industrial solid waste to replace part of the cement to prepare composite micro-powder green and low-carbon concrete has become an important research direction. Steel slag and slag are the main wastes generated by the iron and steel industry and the ironmaking industry. A large amount of stacking not only occupies land resources but may also cause environmental pollution. Recycling them to prepare concrete can not only reduce the emission of solid waste but also reduce the dependence on cement in concrete production, with significant environmental and economic benefits.

[0003] In related technologies, although various methods have been tried to improve the utilization efficiency of steel slag and slag, such as direct blending or activation treatment with a single activator, some solutions enhance the reaction activity of slag through alkaline activators (such as silicate-based), or increase the steel slag content through physical granulation processes. However, such solutions have the following limitations: due to the relatively high content of free calcium oxide in steel slag micro-powder, it is easy to cause volume expansion, increasing the risk of late cracking of concrete; at the same time, the contact efficiency between the activator and the slag is insufficient, and the release of active components is not sufficient, making it difficult to achieve the balance between early strength and long-term stability.

[0004] To address the above problems, how to achieve the efficient synergistic activation of steel slag-slag and its environmentally friendly application, and improve its early strength and stability, has become the key challenge to enhancing the comprehensive performance of green and low-carbon concrete. Summary of the Invention

[0005] In order to improve the early strength and stability of steel slag-slag composite micro-powder concrete, this application provides a steel slag-slag composite micro-powder green and low-carbon concrete.

[0006] In the first aspect, a steel slag-slag composite micro-powder green and low-carbon concrete provided by this application adopts the following technical solution: A steel slag-slag composite micro-powder green and low-carbon concrete, comprising the following raw materials in parts by weight: 25 - 35 parts of modified steel slag microspheres, 20 - 30 parts of slag powder, 10 - 15 parts of cement, 30 - 40 parts of coarse aggregate, 1.2 - 2 parts of admixture, and 18 - 30 parts of water. The steel slag microspheres are porous steel slag microspheres, and an activator is loaded in the pores and a phase change material is encapsulated.

[0007] By adopting the above technical solution, the introduction of modified steel slag microspheres as the core functional component realizes a double breakthrough in performance and environmental protection. The modified steel slag microspheres adopt a porous structure design. The internal pores not only serve as carriers to load chemical activators that can stimulate the activity of slag, but also innovatively encapsulate phase change materials. During the hardening process of concrete, the activator and slag powder undergo a synergistic hydration reaction, significantly improving the early strength and late durability of concrete; while the phase change material effectively regulates the internal temperature fluctuation of concrete through heat absorption and release, greatly reducing the risk of microcracks caused by thermal expansion and contraction, and improving the crack resistance of concrete. In addition, the combined utilization of steel slag and slag not only reduces the consumption of cement clinker, reduces carbon emissions, but also the porous structure of steel slag microspheres endows concrete with excellent heat insulation and noise reduction properties, making it have significant application value in the field of building energy conservation, and realizing the coordinated development of green and high-performance concrete.

[0008] Optionally, the preparation of the modified steel slag microspheres includes the following steps: (1) Mix steel slag powder and silica sol, stir and add water to form a plastic dough. After granulation, let it stand at room temperature to obtain microspheres with a particle size between 5 - 10 mm. Heat them to 600 - 800 °C for high-temperature sintering, heat and keep warm for 1 - 1.5 h, and then cool to obtain preliminarily modified steel slag microspheres; (2) Immerse the preliminarily modified steel slag microspheres obtained above in an activator solution, keep the vacuum for 30 min, soak for 1.5 - 2.5 h after releasing the vacuum, take them out, dry them, and then put them into a pre-dispersed mixture of heated and melted paraffin and nano-silica. Keep the vacuum for 20 - 30 min, then release the vacuum and soak at normal pressure for 1 - 1.5 h. After draining, cure at 75 - 85 °C for 2 - 3 h, and slowly cool to room temperature to obtain modified steel slag microspheres.

[0009] By adopting the above technical solutions, two-stage precise regulation realizes functional modification, significantly improving the comprehensive performance of concrete. In the first stage, the high-temperature sintering process utilizes the glassy network structure formed by silica sol at high temperature to tightly bond steel slag powder particles into a porous microsphere skeleton. This structure not only endows the microspheres with excellent mechanical strength but also forms a large number of hierarchical pores, providing an ideal carrier for subsequent functional modification. In the second stage, the activator loading and phase change material encapsulation process adopts vacuum impregnation technology. Through the cyclic operation of vacuum pumping - vacuum release, the activator solution and the phase change material precursor (paraffin / nano-silica mixture) fully penetrate into the interior of the microsphere pores. Among them, the activator forms a chemical anchoring layer on the inner wall of the pores, effectively solving the problem of easy loss of the activator in traditional modification methods and greatly improving the activation efficiency of slag activity; the introduction of nano-silica not only enhances the interfacial bonding force between the phase change material and the pore wall but also further optimizes the pore structure of the microspheres through its micro-nano filling effect. The finally obtained modified steel slag microspheres exhibit dual functions in concrete: the activator continuously releases active ions in the early hydration stage, promoting the hydration of slag micro-powder to form dense C-S-H gel; the phase change material absorbs the heat release peak of concrete hydration through latent heat of phase change, reducing the internal temperature fluctuation range and effectively inhibiting early shrinkage cracks. This modification technology not only maintains the high strength of concrete but also enhances its crack resistance, providing key technical support for the development of green and low-carbon concrete.

[0010] Optionally, the weight ratio of the added steel slag powder, silica sol, and water is 16 - 20:2 - 4:4 - 6.

[0011] Optionally, the activator solution is a mixed solution of sodium silicate and sodium sulfate with a mass ratio of 2 - 3:1 and a concentration of 15 - 20 wt%.

[0012] By adopting the above technical solutions, this activator solution constructs a synergistic dual-activation system in the green and low-carbon concrete of steel slag - slag composite micro-powder through precise mass ratio optimization and scientific concentration regulation of sodium silicate and sodium sulfate. As an alkaline activator, sodium silicate can efficiently dissociate silicate ions and sodium ions due to its high solubility. Through the depolymerization - polycondensation reaction with the glassy silicon-oxygen tetrahedron in the slag, it quickly generates C-S-H gel with gelling properties; the introduction of sodium sulfate generates ettringite through the chemical reaction of sulfate ions and slag calcium ions. Its expansion effect effectively compensates for the early shrinkage of concrete, and at the same time, its strong complexing effect can stabilize the active aluminum phase in the slag, significantly improving the activation efficiency of slag activity.

[0013] In particular, when sodium silicate and sodium sulfate form a specific ratio, the "alkali activation-sulfate activation" dual activation effect produced by their synergy is particularly prominent: the mechanism of rapid early strength improvement dominated by sodium silicate and the mechanism of continuous late strength growth guaranteed by sodium sulfate complement each other, enabling the concrete to maintain mechanical properties comparable to those of the reference concrete even when the cement dosage is reduced by 30%.

[0014] Optionally, nitrogen is introduced while heating in the step (1).

[0015] By adopting the above technical solution, the continuous introduction of nitrogen effectively isolates oxygen, avoids the oxidation reaction of iron elements in the steel slag at high temperature, thus inhibiting the formation of impurity phases such as iron oxide, and making the pore structure of the microspheres more pure and the connectivity significantly improved. This protection mechanism not only retains the original chemical activity of the active components in the steel slag, but also improves the loading efficiency of the subsequent activator and phase change material by reducing the blockage effect of oxidation products on the pores. Particularly crucial is that the reducing environment formed under the nitrogen atmosphere promotes the stable existence of low-valent iron ions in the steel slag, and these iron ions can serve as active centers during the hydration process, significantly accelerating the hydration reaction rate of the slag powder and improving the early strength of the concrete.

[0016] Optionally, the admixture is obtained by mixing a polycarboxylate water reducer, a sodium gluconate retarder, and a sodium dodecyl sulfate air-entraining agent in a weight ratio of 0.8-1.2:0.3-0.5:0.1-0.3.

[0017] Optionally, 3-5 parts of polyphosphoric acid are also added to the raw materials.

[0018] By adopting the above technical solution, the introduction of polyphosphoric acid significantly improves the comprehensive performance of the steel slag-slag composite micro-powder green and low-carbon concrete. Its core role lies in strengthening the hydration reaction and microstructural stability of the concrete through multiple mechanisms. Polyphosphoric acid plays three key effects in the concrete system: First, its strong complexing ability can chelate calcium and aluminum ions in the slag and steel slag to form soluble complexes, significantly increasing the dissolution rate of the active components and shortening the induction period of the slag hydration reaction; Second, polyphosphoric acid reacts chemically with the hydration products of silicate to generate phosphate phases, and these microcrystalline phases can fill the pores of the cement stone and enhance the strength of the interfacial transition zone, improving the mechanical properties of the concrete; Third, polyphosphoric acid gradually hydrolyzes into phosphate ions in an alkaline environment and continuously participates in the secondary crystallization process of the hydration products, optimizing the chain structure of the C-S-H gel and further improving the strength of the concrete. Particularly, polyphosphoric acid provides the driving force for rapid strength growth in the early stage of the concrete through the dynamic balance mechanism of complexation-hydrolysis, and then guarantees the strength stability through the continuous formation of phosphate phases in the later stage. This dual effect enables the concrete to maintain mechanical properties comparable to those of the reference concrete even when the cement dosage is reduced.

[0019] In a second aspect, the present application provides a method for preparing green and low-carbon concrete with steel slag-slag composite fine powder, adopting the following technical solution: A method for preparing green and low-carbon concrete with steel slag-slag composite fine powder includes the following steps: Mix the modified steel slag microspheres, slag fine powder and cement dry, add coarse aggregate and water and stir evenly, then add admixture and stir evenly to obtain the green and low-carbon concrete with steel slag-slag composite fine powder.

[0020] In summary, the present application has the following beneficial effects: 1. Through the porous structure design of the modified steel slag microspheres, on the one hand, the situation of steel slag expanding and bursting in concrete is avoided, and on the other hand, the activator loaded inside can have a synergistic hydration reaction with the slag fine powder, significantly improving the early strength; at the same time, the encapsulated phase change material (paraffin / nano-SiO2) regulates the internal temperature fluctuation of the concrete through the latent heat of phase change, reducing the risk of microcracks caused by temperature stress, and achieving a double breakthrough in high strength and high crack resistance.

[0021] 2. Through the combined utilization of steel slag microspheres and slag fine powder in the present application, the active components such as iron and calcium in the steel slag and the silicon and aluminum components of the slag play a synergistic role during the hydration process of the concrete, significantly reducing the dosage of cement clinker, thereby greatly reducing carbon dioxide emissions.

[0022] 3. Through the synergistic effect of the activator and polyphosphoric acid, a three-level regulation mechanism of "alkali activation - sulfate activation - phosphate complexation" is constructed, realizing precise control of the concrete hydration reaction. The precise ratio of sodium silicate and sodium sulfate forms highly active hydration products in the early stage, rapidly increasing the strength; the complexation-hydrolysis process of polyphosphoric acid continuously optimizes the C-S-H gel structure, ensuring the strength stability in the later stage. In addition, the temperature regulation function of the phase change material further extends the service life of the concrete. Specific embodiments

[0023] The following further elaborates on the present application with reference to embodiments.

[0024] For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0025] The cement is Portland cement, purchased from Qianfu Mineral Products Processing Factory in Lingshou County, with a strength grade of 32.5; the coarse aggregate is a mixture of gravel with particle sizes of 5 mm to 10 mm and 10 mm to 20 mm in a mass ratio of 3:17, and the crushing value ≤ 12%; the slag fine powder is granulated blast furnace slag powder, with a vitreous content ≥ 85% and a specific surface area ≥ 450m 2 / kg, where CaO is 35% - 45%, SiO₂ is 30% - 38%, Al₂O₃ is 8% - 15%, MgO ≤ 8%, and sulfide ≤ 2%; the steel slag powder is converter steel slag powder, with free CaO ≤ 1.5%, FeO ≤ 10%, and specific surface area ≥ 500 m 2 / kg, and its chemical composition meets: CaO 40% - 50%, SiO₂ 12% - 20%, FeO + Fe₂O₃ 15% - 25%, MgO ≤ 8%; the polyphosphoric acid is purchased from Shandong Yukang Chemical Co., Ltd., 8017 - 16 - 1.

[0026] Preparation examples of raw materials and / or intermediates: Preparation Example 1 A modified steel slag microsphere, the preparation includes the following steps: (1) Mix 50 kg of steel slag powder with 5.4 kg of silica sol, stir and add 13.5 kg of water to form a plastic dough. After granulation, let it stand at room temperature to obtain microspheres with a particle size between 5 - 10 mm. Under nitrogen protection, heat up to 700 °C at a rate of 5 °C / min for high-temperature sintering, heat and keep warm for 1.5 h, and cool with the furnace to obtain preliminarily modified steel slag microspheres; (2) Immerse the preliminarily modified steel slag microspheres obtained above in an alkaline activator solution of 15 wt% sodium silicate and sodium sulfate (mass ratio 2:1), evacuate to -0.095 MPa and keep for 30 min, release the vacuum and soak at normal pressure for 2 h, take out and dry. Immerse them in a pre-dispersed mixture of molten paraffin at 80 °C and 5% nano-silica, evacuate to -0.08 MPa and keep for 30 min, then release the vacuum and soak at normal pressure for 1.5 h, drain, and cure at 80 °C for 2 h, and slowly cool to room temperature to obtain modified steel slag microspheres; the pre-dispersed mixture is prepared by pre-adding 5% nano-SiO₂ based on the total mass of molten paraffin to 80 °C molten paraffin, and treating it with a high-speed shear disperser at a speed of 2000 rpm for 30 min until the mixture is uniformly milky white and has no visible agglomerated particles.

[0027] Preparation Example 2 A modified steel slag microsphere, the preparation includes the following steps: (1) Mix 50 kg of steel slag powder with 7.5 kg of silica sol, stir and add 10 kg of water to form a plastic dough. After granulation, let it stand at room temperature to obtain microspheres with a particle size between 5 - 10 mm. Under nitrogen protection, heat up to 600 °C at a rate of 5 °C / min for high-temperature sintering, heat and keep warm for 1 h, and cool with the furnace to obtain preliminarily modified steel slag microspheres; (2) Immerse the steel slag microspheres obtained from the above preliminary modification into an alkaline activator solution of 20 wt% sodium silicate and sodium sulfate (mass ratio of 3:1), evacuate to -0.095 MPa and hold for 30 min, soak under normal pressure for 1.5 h after releasing the vacuum, take out and dry, then immerse into a pre-dispersed mixture of molten paraffin at 80 °C and 5% nano-silica, evacuate to -0.08 MPa and hold for 20 min, then soak under normal pressure for 1 h after releasing the vacuum, drain, and cure at 85 °C for 2.5 h, and slowly cool to room temperature to obtain modified steel slag microspheres; the pre-dispersed mixture is prepared by adding 5% nano-SiO₂ based on the total mass of molten paraffin into molten paraffin at 80 °C in advance, and treating with a high-speed shear disperser at a speed of 2000 rpm for 30 min until the mixture becomes uniformly milky white and has no visible agglomerated particles.

[0028] Preparation Example 3 A kind of modified steel slag microspheres, the preparation comprises the following steps: (1) Mix 50 kg of steel slag powder and 5.4 kg of silica sol, stir and add 13.5 kg of water to form a plastic dough, granulate and let stand at room temperature to obtain microspheres with a particle size between 5 - 10 mm, sinter at a high temperature of 800 °C with a heating rate of 5 °C / min under nitrogen protection, heat and hold for 1 h, and cool with the furnace to obtain preliminarily modified steel slag microspheres; (2) Immerse the steel slag microspheres obtained from the above preliminary modification into an alkaline activator solution of 18 wt% sodium silicate and sodium sulfate (mass ratio of 2:1), evacuate to -0.095 MPa and hold for 30 min, soak under normal pressure for 2.5 h after releasing the vacuum, take out and dry, then immerse into a pre-dispersed mixture of molten paraffin at 80 °C and 5% nano-silica, evacuate to -0.08 MPa and hold for 25 min, then soak under normal pressure for 1 h after releasing the vacuum, drain, and cure at 75 °C for 3 h, and slowly cool to room temperature to obtain modified steel slag microspheres; the pre-dispersed mixture is prepared by adding 5% nano-SiO₂ based on the total mass of molten paraffin into molten paraffin at 80 °C in advance, and treating with a high-speed shear disperser at a speed of 2000 rpm for 30 min until the mixture becomes uniformly milky white and has no visible agglomerated particles.

[0029] Preparation Example 4 A kind of modified steel slag microspheres, different from Preparation Example 1 in that nitrogen is not introduced during the heating and sintering in this preparation example, and sintering is carried out in air.

[0030] Preparation Example 5 A kind of modified steel slag microspheres, different from Preparation Example 1 in that the activator solution in this preparation example is a 15 wt% sodium silicate solution.

[0031] Preparation Example 6 A kind of modified steel slag microspheres, different from Preparation Example 1 in that the activator solution in this preparation example is a 15 wt% sodium sulfate solution.

[0032] Comparative Preparation Example 1 A modified steel slag microsphere, which is different from Preparation Example 1 in that in this preparation example Example

[0033] Example 1

[0034] A steel slag - slag composite micro - powder green low - carbon concrete, the preparation of which comprises the following steps: Take 30 kg of the modified steel slag microspheres prepared in Preparation Example 1, 25 kg of slag micro - powder and 15 kg of cement, mix them dry, add 30 kg of coarse aggregate and 24 kg of water, stir evenly, then add 1.2 kg of polycarboxylate water - reducing agent, 0.5 kg of sodium dodecyl sulfate air - entraining agent and 0.3 kg of sodium gluconate retarder, and stir evenly to obtain the steel slag - slag composite micro - powder green low - carbon concrete.

[0035] Example 2

[0036] A steel slag - slag composite micro - powder green low - carbon concrete, the preparation of which comprises the following steps: Take 25 kg of the modified steel slag microspheres prepared in Preparation Example 2, 30 kg of slag micro - powder and 10 kg of cement, mix them dry, add 35 kg of coarse aggregate and 18 kg of water, stir evenly, then add 0.8 kg of polycarboxylate water - reducing agent, 0.3 kg of sodium dodecyl sulfate air - entraining agent and 0.2 kg of sodium gluconate retarder, and stir evenly to obtain the steel slag - slag composite micro - powder green low - carbon concrete.

[0037] Example 3

[0038] A steel slag - slag composite micro - powder green low - carbon concrete, the preparation of which comprises the following steps: Take 35 kg of the modified steel slag microspheres prepared in Preparation Example 3, 20 kg of slag micro - powder and 12.5 kg of cement, mix them dry, add 40 kg of coarse aggregate and 30 kg of water, stir evenly, then add 1 kg of polycarboxylate water - reducing agent, 0.4 kg of sodium dodecyl sulfate air - entraining agent and 0.2 kg of sodium gluconate retarder, and stir evenly to obtain the steel slag - slag composite micro - powder green low - carbon concrete.

[0039] Example 4

[0040] A steel slag - slag composite micro - powder green low - carbon concrete, which is different from Example 1 in that the modified steel slag microspheres prepared in Preparation Example 4 are used in this example.

[0041] Example 5

[0042] A steel slag - slag composite micro - powder green low - carbon concrete, which is different from Example 1 in that the modified steel slag microspheres prepared in Preparation Example 5 are used in this example.

[0043] Example 6

[0044] A green and low-carbon concrete with steel slag-slag composite micro-powder, which is different from that in Example 1 in that the modified steel slag microspheres prepared in Preparation Example 6 are used in this example.

[0045] Example 7

[0046] A green and low-carbon concrete with steel slag-slag composite micro-powder, which is different from that in Example 1 in that 3 kg of polyphosphoric acid is further added in this example, and it includes the following steps: Take 30 kg of the modified steel slag microspheres prepared in Preparation Example 1, 25 kg of slag micro-powder and 15 kg of cement and mix them dry, add 30 kg of coarse aggregate and 24 kg of water and stir evenly, then add 1.2 kg of polycarboxylate superplasticizer, 0.5 kg of sodium dodecyl sulfate air-entraining agent, 3 kg of polyphosphoric acid and 0.3 kg of sodium gluconate retarder and stir evenly to obtain the green and low-carbon concrete with steel slag-slag composite micro-powder.

[0047] Example 8

[0048] A green and low-carbon concrete with steel slag-slag composite micro-powder, which is different from that in Example 7 in that 4 kg of polyphosphoric acid is added in this example.

[0049] Example 9

[0050] A green and low-carbon concrete with steel slag-slag composite micro-powder, which is different from that in Example 7 in that 5 kg of polyphosphoric acid is added in this example.

[0051] Comparative Example Comparative Example 1 A green and low-carbon concrete with steel slag-slag composite micro-powder, which is different from that in Example 1 in that the same amount of ordinary steel slag powder is used to replace the modified steel slag microspheres in this comparative example.

[0052] Performance Detection Test Test Method

[0053] Compressive strength: Use 100 mm×100 mm×100 mm cube specimens, the loading rate is 1 Mpa / s, and the compressive strength of the test blocks at 3 d and 28 d is respectively tested according to the Standard for Test Methods of Mechanical Properties of Ordinary Concrete (GB / T50081-2002); Durability: Test was conducted according to the relevant test methods of GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The freezing temperature and melting temperature of the specimen were -20°C to -15°C and 6°C - 8°C respectively. The time for one freeze-thaw cycle was 4h, and the freeze-thaw cycle was carried out 200 times. The mass of the test block before and after the test was measured, and the mass loss rate was calculated. Shrinkage rate: According to the shrinkage test in 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the shrinkage performance of concrete at 56d was tested to obtain the drying shrinkage rate of concrete at 56d.

[0054] Table 1 Test and Detection Data

[0055] Combined with Examples 1-3 and Comparative Example 1 and Table 1, it can be seen that the experimental data of Examples 1-3 are all higher than those of Comparative Example 1, indicating that the modified steel slag microspheres can significantly improve the early hydration rate and the density of the interfacial transition zone of concrete through the synergistic effect of loading activators and encapsulating phase change materials by the porous structure, thereby improving the mechanical properties of concrete.

[0056] Combined with Example 1 and Example 4 and Table 1, it can be seen that the experimental data of Example 1 are all better than those of Example 4, indicating that nitrogen can inhibit the volume expansion of microspheres caused by the oxidation of Fe 2+ to Fe 3+ which is beneficial to maintaining the stability of concrete and improving the mechanical properties of concrete.

[0057] Combined with Example 1 and Examples 5-6 and Table 1, it can be seen that the experimental data of Example 1 are all better than those of Examples 5-6, indicating that the double-activator system can greatly improve the mechanical properties of concrete, and sodium silicate and sodium sulfate have a good complementary effect.

[0058] Combined with Example 1 and Examples 7-9 and Table 1, it can be seen that the experimental data of Examples 7-9 are all better than those of Example 1, indicating that the addition of polyphosphoric acid can form soluble complexes by chelating Fe 3+ , Al 3+ and other ions in the steel slag, accelerate the dissolution of slag, and refine the pore structure by generating calcium phosphate nanocrystals, thereby improving the compressive strength of concrete.

[0059] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A green and low-carbon concrete made of steel slag-slag composite fine powder, characterized in that It comprises the following raw materials in parts by weight: 25-35 parts of modified steel slag microspheres, 20-30 parts of slag micro-powder, 10-15 parts of cement, 30-40 parts of coarse aggregate, 1.2-2 parts of admixture and 18-30 parts of water. The steel slag microspheres are porous steel slag microspheres, and an activator is loaded in the pores and a phase change material is encapsulated.

2. The green and low-carbon concrete made of steel slag-slag composite micro powder according to claim 1, characterized in that The preparation of the modified steel slag microspheres comprises the following steps: (1) Mix steel slag powder with silica sol, stir and add water to form a plastic dough. Granulate and let stand at room temperature to obtain microspheres with a particle size between 5-10 mm. Heat them to 600-800 °C for high-temperature sintering, heat and keep warm for 1-1.5 h, and then cool to obtain preliminarily modified steel slag microspheres; (2) Immerse the preliminarily modified steel slag microspheres obtained above in an activator solution, keep the vacuum for 30 min, soak for 1.5-2.5 h after releasing the vacuum, take out and dry, then put them into a pre-dispersed mixture of heated and melted paraffin and nano-silica. Keep the vacuum for 20-30 min, then release the vacuum and soak at normal pressure for 1-1.5 h, drain, and cure at 75-85 °C for 2-3 h, and slowly cool to room temperature to obtain modified steel slag microspheres.

3. The green and low-carbon concrete made of steel slag-slag composite micro-powder according to claim 2, characterized in that: The weight ratio of the added steel slag powder, silica sol and water is 16-20:2-4:4-6.

4. The green low-carbon concrete made of steel slag-slag composite micro-powder according to claim 2, wherein: The activator solution is a mixed solution of sodium silicate and sodium sulfate with a mass ratio of 2-3:1 and a concentration of 15-20 wt%.

5. The green and low-carbon concrete made of steel slag-slag composite micro-powder according to claim 2, wherein: In the step (1), nitrogen is introduced while heating.

6. A steel slag-slag composite micro-powder green low-carbon concrete according to claim 1, characterized in that: The admixture is obtained by mixing a polycarboxylate water reducer, a sodium gluconate retarder and a sodium dodecyl sulfate air-entraining agent according to a weight ratio of 0.8-1.2:0.3-0.5:0.1-0.

3.

7. A green and low-carbon concrete made of steel slag-slag composite fine powder according to claim 1, characterized in that: 3-5 parts of polyphosphoric acid are also added to the raw materials.

8. A preparation method of steel slag-slag composite micro-powder green low-carbon concrete according to any one of claims 1-7, characterized in that, It comprises the following steps: Mix the modified steel slag microspheres, slag micro-powder and cement for dry mixing, add the coarse aggregate and water, stir evenly, and then add the admixture and stir evenly to obtain the steel slag-slag composite micro-powder green low-carbon concrete.

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