A kind of steel slag-slag composite micro-powder green low-carbon concrete and preparation method thereof

Abstract

The present application relates to the field of building materials technology, and specifically discloses a green low-carbon concrete made of steel slag and slag composite micropowder and a preparation method thereof. A green low-carbon concrete made of steel slag and slag composite micropowder includes 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 admixture, and 18-30 parts of water. The steel slag microspheres are porous steel slag microspheres, and an activator is loaded in their pores and a phase change material is encapsulated. The preparation method is as follows: dry-mixing the modified steel slag microspheres, slag micropowder, and cement, adding coarse aggregate and water, stirring evenly, and then adding an admixture and stirring evenly to obtain the green low-carbon concrete made of steel slag and slag composite micropowder. The composition of the present application can be used in the fields of building structures, road engineering, and marine facilities, and has the advantages of high early strength and good mechanical properties.

Description

Technical Field

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

[0002] With the rapid development of the global construction industry, the demand for concrete, as one of the most important building materials, continues to rise. Traditional concrete uses cement as the main binder, but the cement production process consumes a lot of energy and emits a lot of carbon dioxide. According to statistics, every ton of cement produced emits about 0.8-1 ton of carbon dioxide, which puts tremendous pressure on the global environment. In this context, the development of green and low-carbon building materials has become an industry consensus. Among them, the use of 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 steel industry and ironmaking industry. Large-scale accumulation not only occupies land resources, but also may pollute the environment. Utilizing them as resources to prepare concrete can not only reduce the emission of solid waste, but also reduce the dependence of concrete production on cement, with significant environmental and economic benefits.

[0003] In the related art, although various methods have been tried to improve the utilization efficiency of steel slag and mineral slag, such as direct blending or activation treatment with a single activator, some solutions use alkaline activators (such as silicates) to enhance the reactivity of slag, or increase the steel slag dosage through physical granulation processes, these solutions have the following limitations: Due to the high free calcium oxide content, steel slag powder easily causes volume expansion, increasing the risk of late-stage cracking in concrete; Furthermore, the contact efficiency between the activator and the mineral slag is insufficient, resulting in insufficient release of active components, making it difficult to achieve a balance between early strength and long-term stability.

[0004] In response to the above problems, how to achieve efficient synergistic excitation of steel slag and mineral slag and environmentally friendly application to improve its early strength and stability has become a key challenge in improving 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, the present application provides a steel slag-slag composite micro-powder green low-carbon concrete.

[0006] In the first aspect, the present application provides a steel slag-slag composite micro-powder green low-carbon concrete, which adopts the following technical solution:

[0007] A steel slag-slag composite micro-powder green low-carbon concrete comprises the following raw materials in parts by weight:

[0008] 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, the pores of which are loaded with activators and encapsulate phase change materials.

[0009] By adopting the above technical solution and introducing modified steel slag microspheres as the core functional component, a dual breakthrough in performance and environmental protection has been achieved. The modified steel slag microspheres adopt a porous structure design. The internal pores not only serve as a carrier to load the chemical activator that can stimulate the activity of slag, but also innovatively encapsulate the phase change material. During the concrete hardening process, the activator and the slag micropowder undergo a synergistic hydration reaction, significantly improving the early strength and later durability of the concrete; while the phase change material effectively regulates the internal temperature fluctuations of the concrete through heat absorption and release, greatly reducing the risk of microcracks caused by thermal expansion and contraction, and improving the crack resistance of the concrete. In addition, the composite utilization of steel slag and slag not only reduces the amount of cement clinker and reduces carbon emissions, but the porous structure of the steel slag microspheres also gives the concrete excellent thermal 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 concrete and high performance.

[0010] Optionally, the preparation of modified steel slag microspheres includes the following steps:

[0011] (1) Steel slag powder and silica sol are mixed and stirred, and water is added to form a plastic mud ball. After granulation, the mixture is allowed to stand at room temperature to obtain microspheres with a particle size of 5-10 mm. The microspheres are heated to 600-800 ° C and sintered. The mixture is heated and kept warm for 1-1.5 hours and cooled to obtain preliminarily modified steel slag microspheres.

[0012] (2) The steel slag microspheres obtained by the above preliminary modification are immersed in an activator solution, vacuumed and maintained for 30 minutes, and then immersed for 1.5-2.5 hours after the vacuum is released. After being taken out and dried, they are placed in a pre-dispersed mixture of heated molten paraffin and nano-silica, vacuumed and maintained for 20-30 minutes, and then released and immersed at normal pressure for 1-1.5 hours. After draining, they are cured at 75-85°C for 2-3 hours, and then slowly cooled to room temperature to obtain modified steel slag microspheres.

[0013] By employing this technical solution, functional modification is achieved through precise two-stage control, significantly improving the overall performance of concrete. The first stage, a high-temperature sintering process, leverages the glassy network structure formed by silica sol at high temperatures to tightly bond steel slag powder particles into a porous microsphere skeleton. This structure not only imparts excellent mechanical strength to the microspheres but also creates a large number of hierarchical pores, providing an ideal carrier for subsequent functional modification. The second stage, the activator loading and phase change material encapsulation process, utilizes vacuum impregnation technology. Through a cycle of vacuum pumping and release, the activator solution and phase change material precursor (paraffin wax / nano-silica mixture) fully penetrate the microsphere pores. The activator forms a chemical anchoring layer on the pore walls, effectively addressing the activator's easy loss in traditional modification methods and significantly improving the efficiency of slag activation. The introduction of nano-silica not only strengthens the interfacial bonding between the phase change material and the pore walls but also further optimizes the microsphere pore structure through its micro-nanofilling effect. The resulting modified steel slag microspheres exhibit dual functions in concrete: the activator continuously releases active ions during the early hydration stage, promoting the hydration of the slag powder to form a dense CSH gel; the phase change material absorbs the exothermic peak of concrete hydration through phase change latent heat, reducing internal temperature fluctuations and effectively suppressing early shrinkage cracking. 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, low-carbon concrete.

[0014] Optionally, the weight ratio of the steel slag powder, silica sol and water is 16-20:2-4:4-6.

[0015] Optionally, the activator solution is a mixed solution of sodium silicate and sodium sulfate in a mass ratio of 2-3:1 and a concentration of 15-20 wt%.

[0016] By adopting the above technical solution, the activator solution, through precise mass optimization of sodium silicate and sodium sulfate and scientific concentration control, establishes a synergistic dual activation system in steel slag-slag composite micropowder green low-carbon concrete. As an alkaline activator, sodium silicate's high solubility allows for efficient dissociation of silicate and sodium ions. Through a depolymerization-polycondensation reaction with the glassy silicon-oxygen tetrahedrons in the slag, it rapidly generates a CSH gel with gelling properties. The introduction of sodium sulfate generates ettringite through a chemical reaction between sulfate ions and slag calcium ions. Its expansion effect effectively compensates for early concrete shrinkage, while its strong complexation stabilizes the active aluminum phase in the slag, significantly improving the efficiency of slag activation.

[0017] In particular, when sodium silicate and sodium sulfate form a specific ratio, the "alkali activation-sulfate activation" dual activation effect produced synergistically by the two is particularly prominent: the early rapid strength improvement mechanism dominated by sodium silicate and the later continuous strength growth mechanism guaranteed by sodium sulfate complement each other, so that the concrete can still maintain mechanical properties comparable to those of the benchmark concrete while reducing the cement content by 30%.

[0018] Optionally, nitrogen is introduced during heating in step (1).

[0019] By adopting the above technical solution, the continuous introduction of nitrogen effectively isolates oxygen, avoids the oxidation reaction of iron elements in steel slag at high temperatures, and thus inhibits the formation of impurity phases such as iron oxide, making the pore structure of the microspheres purer and significantly improving connectivity. 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 subsequent activators and phase change materials by reducing the clogging effect of oxidation products on the pores. What is particularly critical is that the reducing environment formed in the nitrogen atmosphere promotes the stable existence of low-valent iron ions in the steel slag. These iron ions can act as active centers during the hydration process, significantly accelerating the hydration reaction rate of slag micropowder and improving the early strength of concrete.

[0020] Optionally, the admixture is obtained by mixing a polycarboxylate water reducer, a sodium gluconate retarder and a sodium lauryl sulfate air entraining agent in a weight ratio of 0.8-1.2:0.3-0.5:0.1-0.3.

[0021] Optionally, 3-5 parts of polyphosphoric acid are also added to the raw materials.

[0022] By adopting the above-mentioned technical solution, the introduction of polyphosphoric acid significantly improves the comprehensive performance of steel slag-slag composite micropowder green low-carbon concrete. Its core role lies in strengthening the concrete's hydration reaction and microstructural stability through multiple mechanisms. Polyphosphoric acid exerts three key effects in the concrete system: First, its strong chelating ability can chelate the calcium and aluminum ions in slag and steel slag to form soluble complexes, significantly increasing the dissolution rate of active components and shortening the induction period of the slag hydration reaction; second, polyphosphoric acid chemically reacts with silicate hydration products to form phosphate phases. These microcrystalline phases can fill the pores of cement paste and enhance the strength of the interfacial transition zone, improving the mechanical properties of concrete; third, polyphosphoric acid gradually hydrolyzes into phosphate ions in an alkaline environment, continuously participating in the secondary crystallization process of the hydration products, optimizing the chain structure of the CSH gel, and further improving the strength of the concrete. In particular, polyphosphoric acid provides rapid strength growth in the early stage of concrete through the dynamic equilibrium mechanism of complexation-hydrolysis, and ensures strength stability in the later stage through the continuous formation of phosphate phase. This dual effect enables concrete to maintain mechanical properties comparable to those of benchmark concrete while reducing cement content.

[0023] In a second aspect, the present application provides a method for preparing steel slag-slag composite micro-powder green low-carbon concrete, which adopts the following technical solution:

[0024] A method for preparing steel slag-slag composite micropowder green low-carbon concrete comprises the following steps:

[0025] The modified steel slag microspheres, slag powder and cement are dry-mixed, coarse aggregate and water are added and stirred evenly, and then an admixture is added and stirred evenly to obtain the steel slag-slag composite powder green low-carbon concrete.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. This application adopts a porous structure design of modified steel slag microspheres, which, on the one hand, avoids the expansion and bursting of steel slag in concrete. On the other hand, the activator loaded inside can undergo a synergistic hydration reaction with the slag micropowder, significantly improving the early strength. At the same time, the encapsulated phase change material (paraffin wax / nano-SiO2) regulates the temperature fluctuations inside the concrete through the latent heat of phase change, reducing the risk of microcracks caused by temperature stress, and achieving a dual breakthrough in high strength and high crack resistance.

[0028] 2. In this application, by composite utilization of steel slag microspheres and slag micropowder, the active components such as iron and calcium in steel slag and the silicon and aluminum components of slag work synergistically during the concrete hydration process, significantly reducing the amount of cement clinker, thereby greatly reducing carbon dioxide emissions.

[0029] 3. This application utilizes the synergistic effect of an activator and polyphosphoric acid to construct a three-stage control mechanism: "alkali activation - sulfate activation - phosphate complexation," achieving precise control of the concrete hydration reaction. The precise ratio of sodium silicate to sodium sulfate forms highly active hydration products early on, rapidly increasing strength. The complexation-hydrolysis process of the polyphosphoric acid continuously optimizes the CSH gel structure, ensuring later strength stability. Furthermore, the temperature control function of the phase change material further extends the service life of the concrete. DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to the embodiments.

[0031] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0032] The cement is silicate cement purchased from Lingshou County Qianfu Mineral Products Processing Plant, with a strength grade of 32.5; the coarse aggregate is crushed stone with a particle size of 5mm-10mm and a particle size of 10mm-20mm, with a mass ratio of 3:17, and a crushing value of ≤12%; the slag powder is granulated blast furnace slag powder with a glass content of ≥85% and a specific surface area of ​​≥450m 2 / kg, of which CaO 35%-45%, SiO230%-38%, Al2O38%-15%, MgO≤8%, sulfide≤2%; steel slag powder is converter steel slag powder, with free CaO≤1.5%, FeO≤10%, specific surface area≥500m 2 / kg, and the chemical composition meets the following requirements: CaO 40%-50%, SiO2 12%-20%, FeO+Fe2O3 15%-25%, MgO ≤ 8%; polyphosphoric acid was purchased from Shandong Yukang Chemical Co., Ltd., 8017-16-1.

[0033] Preparation examples of raw materials and / or intermediates:

[0034] Preparation Example 1

[0035] A modified steel slag microsphere, the preparation of which comprises the following steps:

[0036] (1) 50 kg of steel slag powder and 5.4 kg of silica sol were mixed and stirred, and 13.5 kg of water was added to form a plastic mud ball. After granulation, it was allowed to stand at room temperature to obtain microspheres with a particle size of 5-10 mm. The temperature was raised to 700 ° C at 5 ° C / min under nitrogen protection and sintered. The temperature was kept at this temperature for 1.5 h and cooled with the furnace to obtain the preliminarily modified steel slag microspheres.

[0037] (2) The steel slag microspheres obtained by the above preliminary modification are immersed in an alkaline activator solution of 15wt% sodium silicate and sodium sulfate (mass ratio of 2:1), evacuated to -0.095MPa and maintained for 30min, and then immersed at normal pressure for 2h after releasing the vacuum, taken out and dried, and immersed in a pre-dispersed mixture of 80℃ molten paraffin and 5% nano-silica, evacuated to -0.08MPa and maintained for 30min, and then released the vacuum and immersed at normal pressure for 1.5h, drained and solidified at 80℃ for 2h, and slowly cooled 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 the molten paraffin into the 80℃ molten paraffin, and processed by a high-speed shear disperser at a speed of 2000rpm for 30min until the mixture is uniform milky white and no visible agglomerated particles are obtained.

[0038] Preparation Example 2

[0039] A modified steel slag microsphere, the preparation of which comprises the following steps:

[0040] (1) 50 kg of steel slag powder and 7.5 kg of silica sol were mixed and stirred, and 10 kg of water was added to form a plastic mud ball. After granulation, it was allowed to stand at room temperature to obtain microspheres with a particle size of 5-10 mm. The temperature was raised to 600 ° C at 5 ° C / min under nitrogen protection and sintered. The temperature was kept at this temperature for 1 hour and cooled with the furnace to obtain the preliminarily modified steel slag microspheres.

[0041] (2) The steel slag microspheres obtained by the above preliminary modification are immersed in an alkaline activator solution of 20wt% sodium silicate and sodium sulfate (3:1 mass ratio), evacuated to -0.095MPa and maintained for 30min, and then immersed at normal pressure for 1.5h. They are taken out and dried, and immersed in a pre-dispersed mixed solution of 80℃ molten paraffin and 5% nano-silica, evacuated to -0.08MPa and maintained for 20min, and then released and immersed at normal pressure for 1h. After draining, they are solidified at 85℃ for 2.5h and slowly cooled to room temperature to obtain modified steel slag microspheres; the pre-dispersed mixed solution is prepared by pre-adding 5% nano-SiO2 based on the total mass of the molten paraffin into the 80℃ molten paraffin, and treating it with a high-speed shear disperser at a speed of 2000rpm for 30min until the mixed solution is uniform milky white and no visible agglomerated particles are obtained.

[0042] Preparation Example 3

[0043] A modified steel slag microsphere, the preparation of which comprises the following steps:

[0044] (1) 50 kg of steel slag powder and 5.4 kg of silica sol were mixed and stirred, and 13.5 kg of water was added to form a plastic mud ball. After granulation, it was allowed to stand at room temperature to obtain microspheres with a particle size of 5-10 mm. The temperature was raised to 800 ° C at 5 ° C / min under nitrogen protection and sintered. The temperature was kept at this temperature for 1 hour and cooled with the furnace to obtain the preliminarily modified steel slag microspheres.

[0045] (2) The steel slag microspheres obtained by the above preliminary modification are immersed in an alkaline activator solution of 18wt% sodium silicate and sodium sulfate (mass ratio of 2:1), evacuated to -0.095MPa and maintained for 30min, and then immersed at normal pressure for 2.5h. They are taken out and dried, and immersed in a pre-dispersed mixture of 80℃ molten paraffin and 5% nano-silica, evacuated to -0.08MPa and maintained for 25min, and then released and immersed at normal pressure for 1h. After draining, they are solidified at 75℃ for 3h and slowly cooled 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 the molten paraffin into the 80℃ molten paraffin, and processing it with a high-speed shear disperser at a speed of 2000rpm for 30min until the mixture is uniform milky white and no visible agglomerated particles are obtained.

[0046] Preparation Example 4

[0047] A modified steel slag microsphere is different from Preparation Example 1 in that nitrogen is not introduced during the temperature-raising sintering in this Preparation Example, and the sintering is carried out in air.

[0048] Preparation Example 5

[0049] A modified steel slag microsphere is different from Preparation Example 1 in that the activator solution in this Preparation Example is a 15 wt % sodium silicate solution.

[0050] Preparation Example 6

[0051] A modified steel slag microsphere is different from Preparation Example 1 in that the activator solution in this Preparation Example is a 15 wt % sodium sulfate solution.

[0052] Comparative Preparation Example 1

[0053] A modified steel slag microsphere, which is different from Preparation Example 1 in that

[0054] Example

[0055] Example 1

[0056] A steel slag-slag composite micro-powder green low-carbon concrete, the preparation of which includes the following steps:

[0057] Take 30 kg of modified steel slag microspheres prepared in Preparation Example 1, 25 kg of slag 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 reducer, 0.5 kg of sodium lauryl sulfate air entraining agent and 0.3 kg of sodium gluconate retarder and stir evenly to obtain the steel slag-slag composite micropowder green low-carbon concrete.

[0058] Example 2

[0059] A steel slag-slag composite micro-powder green low-carbon concrete, the preparation of which includes the following steps:

[0060] Take 25 kg of modified steel slag microspheres prepared in Preparation Example 2, 30 kg of slag 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 reducer, 0.3 kg of sodium lauryl sulfate air entraining agent and 0.2 kg of sodium gluconate retarder and stir evenly to obtain the steel slag-slag composite micropowder green low-carbon concrete.

[0061] Example 3

[0062] A steel slag-slag composite micro-powder green low-carbon concrete, the preparation of which includes the following steps:

[0063] Take 35 kg of modified steel slag microspheres prepared in Preparation Example 3, 20 kg of slag 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 reducer, 0.4 kg of sodium lauryl sulfate air entraining agent and 0.2 kg of sodium gluconate retarder and stir evenly to obtain the steel slag-slag composite micropowder green low-carbon concrete.

[0064] Example 4

[0065] A steel slag-slag composite micropowder 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.

[0066] Example 5

[0067] A steel slag-slag composite micropowder 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.

[0068] Example 6

[0069] A steel slag-slag composite micropowder green low-carbon concrete, which is different from Example 1 in that the modified steel slag microspheres prepared in Preparation Example 6 are used in this example.

[0070] Example 7

[0071] A green low-carbon concrete made of steel slag-slag composite micropowder, which differs from Example 1 in that 3 kg of polyphosphoric acid is further added in this embodiment, comprises the following steps:

[0072] Take 30 kg of modified steel slag microspheres prepared in Preparation Example 1, 25 kg of slag 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 polycarboxylic acid water reducer, 0.5 kg of sodium lauryl sulfate air entraining agent, 3 kg of polyphosphoric acid and 0.3 kg of sodium gluconate retarder and stir evenly to obtain the steel slag-slag composite micropowder green low-carbon concrete.

[0073] Example 8

[0074] A steel slag-slag composite micro-powder green low-carbon concrete, which is different from Example 7 in that 4 kg of polyphosphoric acid is added in this example.

[0075] Example 9

[0076] A steel slag-slag composite micro-powder green low-carbon concrete, which is different from Example 7 in that 5 kg of polyphosphoric acid is added in this example.

[0077] Comparative Example

[0078] Comparative Example 1

[0079] A steel slag-slag composite micropowder green low-carbon concrete is different from Example 1 in that an equal amount of ordinary steel slag powder is used to replace modified steel slag microspheres in this comparative example.

[0080] Performance testing

[0081] Test methods

[0082] Compressive strength: Using 100mm×100mm×100mm cubic specimens, with a loading rate of 1Mpa / s, the compressive strength of the specimens was tested at 3d and 28d according to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete";

[0083] Durability: The test was conducted in accordance with the relevant testing methods of GB / T 50082-2024 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete". The freezing and melting temperatures of the specimens were -20°C to -15°C and 6°C to 8°C, respectively. The freeze-thaw cycle lasted for 4 hours and was repeated 200 times. The mass of the specimens before and after the test was measured, and the mass loss rate was calculated.

[0084] Shrinkage rate: According to the shrinkage test in 50082-2024 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete", the shrinkage performance of concrete is tested at 56 days to obtain the 56-day drying shrinkage rate of concrete.

[0085] Table 1 Test data

[0086]

[0087] Combining 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 of concrete and the density of the interface transition zone through the synergistic effect of the porous structure-loaded activator and the encapsulated phase change material, thereby improving the mechanical properties of concrete.

[0088] Combining Example 1 with Example 4 and Table 1, it can be seen that the test data of Example 1 are better than those of Example 4, indicating that nitrogen can inhibit the Fe 2+ Oxidized to Fe 3+ The resulting volume expansion of the microspheres is beneficial to maintaining the stability of concrete and improving the mechanical properties of concrete.

[0089] Combining Example 1 with Examples 5-6 and Table 1, it can be seen that the various test data of Example 1 are better than those of Examples 5-6, indicating that the dual excitation system can greatly improve the mechanical properties of concrete, and sodium silicate and sodium sulfate have a good complementary effect.

[0090] Combining Example 1 with Examples 7-9 and Table 1, it can be seen that the test data of Examples 7-9 are better than those of Example 1, indicating that the addition of polyphosphoric acid can complex Fe in steel slag. 3+ 、Al 3+ The plasma forms soluble complexes, accelerates the dissolution of slag, and refines the pore structure by generating calcium phosphate nanocrystalline nuclei, thereby improving the compressive strength of concrete.

[0091] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A steel slag-slag composite micro-powder green low-carbon concrete, characterized in that: It includes 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, wherein the modified steel slag microspheres are porous steel slag microspheres, the pores of which are loaded with an activator and encapsulate a phase change material; The preparation of modified steel slag microspheres comprises the following steps: (1) Steel slag powder and silica sol are mixed and stirred, and water is added to form a plastic mud ball. After granulation, the mixture is allowed to stand at room temperature to obtain microspheres with a particle size of 5-10 mm. The microspheres are heated to 600-800 ° C and sintered. The mixture is heated and kept warm for 1-1.5 hours and cooled to obtain preliminarily modified steel slag microspheres. (2) The steel slag microspheres obtained by the above preliminary modification are immersed in an activator solution, vacuumed and maintained for 30 minutes, and then immersed for 1.5-2.5 hours after the vacuum is released. After being taken out and dried, they are placed in a pre-dispersed mixture of heated molten paraffin and nano-silica, vacuumed and maintained for 20-30 minutes, and then released and immersed at normal pressure for 1-1.5 hours. After draining, they are cured at 75-85°C for 2-3 hours, and then slowly cooled to room temperature to obtain modified steel slag microspheres.

2. The steel slag-slag composite micro-powder green low-carbon concrete according to claim 1, characterized in that: The weight ratio of the steel slag powder, silica sol and water is 16-20:2-4:4-6.

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

4. The steel slag-slag composite micro-powder green low-carbon concrete according to claim 1, characterized in that: In the step (1), nitrogen is introduced while heating.

5. The 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 lauryl sulfate air entraining agent in a weight ratio of 0.8-1.2:0.3-0.5:0.1-0.

3.

6. The steel slag-slag composite micro-powder green low-carbon concrete according to claim 1, characterized in that: 3-5 parts of polyphosphoric acid are also added to the raw materials.

7. A method for preparing the steel slag-slag composite micropowder green low-carbon concrete according to any one of claims 1 to 5, characterized in that: The steps include: The modified steel slag microspheres, slag powder and cement are dry-mixed, coarse aggregate and water are added and stirred evenly, and then an admixture is added and stirred evenly to obtain the steel slag-slag composite powder green low-carbon concrete.

Images