A multi-graded core-shell structure composite mineral admixture and its preparation process

Abstract

The present invention relates to a multi-graded core-shell structure composite mineral admixture and its preparation process. The raw materials include an activator and a mineral admixture at a mass ratio of 1:15,000 to 1:5,000. The mineral admixture includes, by mass, 300 to 500 parts of a high-iron admixture, 500 to 700 parts of an aluminum-rich admixture, and 500 to 1,000 parts of a high-calcium admixture. The activator includes, by mass, 20 to 50 parts of a functional complexing agent and 10 to 70 parts of a nano-nucleating agent. The mixed composite admixture of the present invention has a core-shell structure, excellent iron and aluminum ion dissolution, and improved utilization in cement systems. At a 30% addition, the performance of cement approaches or even exceeds that of PI52.5.

Description

Technical Field

[0001] The invention relates to the field of mineral admixtures, and in particular to a multi-graded core-shell structure composite mineral admixture and a preparation process thereof. Background Art

[0002] Modern research shows that when some Fe or Al is dissolved in the cement hydration product, the durability of the product will be significantly improved.

[0003] Industrial waste with a high iron content, such as steel slag, has high wear resistance and high grinding energy consumption. Excessively high formation temperature makes the crystal structure dense, the surface passivated, and the dissolution rate slow. At the same time, iron tailings are prone to contain impurity element phosphorus, which will form insoluble phosphate salts with cement hydration product calcium hydroxide, inhibiting the early strength development of the system. Aluminum-rich admixtures such as kaolin have low wear resistance and large specific surface area. They are rapidly hydrated and dissolve in the early stage, while inhibiting the development of later performance. There is some free calcium oxide in high-calcium admixtures such as limestone, which will bring risks such as volume expansion and cracking when added in large quantities. Therefore, the above special component mineral admixtures have usage defects and it is difficult to replace the cement dosage in large quantities. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned technical deficiencies, provide a multi-graded core-shell structure composite mineral admixture and its preparation process, and solve the technical problem in the prior art that special component mineral admixtures are difficult to replace cement in large amounts due to defects such as slow dissolution rate, inhibition of early strength of the system or inhibition of later performance.

[0005] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0006] In the first aspect, the present invention provides a multi-graded core-shell structure composite mineral admixture, the raw materials including an activator and a mineral admixture in a mass ratio of 1:15000 to 1:5000; the mineral admixture includes 300 to 500 parts of high iron admixture, 500 to 700 parts of aluminum-rich admixture and 500 to 1000 parts of high calcium admixture in parts by mass; the activator includes 20 to 50 parts of a functional complexing agent and 10 to 70 parts of a nano nucleating agent in parts by mass.

[0007] In the second aspect, the present invention provides a preparation process of a multi-graded core-shell structure composite mineral admixture, comprising the following steps: mixing and grinding an aluminum-rich admixture and an activator to obtain a first powder; mixing and grinding a high-iron admixture and a high-calcium admixture to obtain a second powder; mixing and stirring the first powder and the second powder evenly to obtain a multi-graded core-shell structure composite mineral admixture.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The present invention adopts functional complexing agent and nano nucleating agent to form efficient activator, optimizes the particle size distribution of mineral admixture, and gives play to multiple advantages such as shaping, coating and activation. The common grinding of high calcium admixture and high iron admixture utilizes the free calcium in the high calcium admixture to solidify the impurity phosphorus element in the high iron admixture, thereby improving the strength of the system. At the same time, the particle size of the high calcium admixture is small, and the surface has a very strong polar adsorption force, which can be wrapped on the surface of the coarse-grained high iron admixture, thereby forming a core-shell structure with the high iron admixture as the core and the high calcium admixture as the shell. The high alkalinity of the surface after hydration of the structure is conducive to the dissolution of the iron element. The common grinding of aluminum-rich admixture and efficient activator can promote the generation of surface bond breaking, and hydration is more rapid. At the same time, the surface-coated nucleating agent can complex calcium and iron ions, thereby promoting the generation of iron-containing and aluminum-containing hydration products. The mixed composite admixtures all have a core-shell structure and excellent dissolution of iron and aluminum ions, which improves their effective utilization in the cement system. When the admixture dosage is 30%, the performance is close to or even exceeds that of PI52.5 cement. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic flow diagram of the preparation process of the present invention;

[0011] Figure 2 This is a schematic diagram of the powder structure formed by the high calcium admixture and the high iron admixture of the present invention; wherein, 1-high calcium admixture, 2-high iron admixture;

[0012] Figure 3 This is a schematic diagram of the powder structure formed by the activator and aluminum-rich admixture of the present invention; wherein, 3-activator, 4-aluminum-rich admixture;

[0013] Figure 4 is the cumulative particle size of the composite mineral admixtures obtained in each embodiment of the present invention and the comparative example;

[0014] Figure 5 It is the compressive strength of the composite mineral admixtures obtained in various embodiments and comparative examples of the present invention at different ages. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] This invention integrates, coats, and activates low-activity mineral admixtures with specialized components to create a multi-graded core-shell structured, high-iron, aluminum-rich, and calcium-rich composite mineral admixture. This enhances the pozzolanic effect and effective utilization of the low-activity admixture. The synthesized ternary composite core-shell structured, high-activity admixture can replace cement in large quantities, dissolving abundant calcium, silicon, aluminum, and iron ions and creating a favorable hydration environment for the formation of iron- and aluminum-containing hydration products.

[0017] Specifically, the present invention provides a multi-graded core-shell structure composite mineral admixture, wherein the raw materials include an activator and a mineral admixture in a mass ratio of 1:15000 to 1:5000;

[0018] The mineral admixture comprises, by weight, 300 to 500 parts of a high iron admixture, 500 to 700 parts of an aluminum-rich admixture, and 500 to 1000 parts of a high calcium admixture;

[0019] Calculated by weight, the activator includes 20 to 50 parts of a functional complexing agent and 10 to 70 parts of a nano nucleating agent.

[0020] Furthermore, the high iron admixture is a silicon-aluminum mineral admixture with an iron oxide content of 15% to 40% and a pozzolanic effect; including one or more of steel slag, iron tailings and iron ore;

[0021] The high calcium admixture is a silica-alumina mineral admixture with a calcium oxide content of 30% to 80% and a pozzolanic effect, including one or more of limestone, fly ash, tuff and papermaking mud.

[0022] The aluminum-rich admixture is a silicon-aluminum mineral admixture with an aluminum oxide content of 20% to 60% and a volcanic ash effect; and includes one of metakaolin and alum stone or a mixture of the two in any proportion.

[0023] Furthermore, the functional complexing agent is one or a combination of triethanolamine, triisopropanolamine, diethanol monoisopropanolamine and glycerol.

[0024] Furthermore, the nano nucleating agent is a CSH nano crystal core product with a solid content of 10 to 20% produced by Jiangsu Subote New Materials Co., Ltd.

[0025] Furthermore, the highly active mineral admixtures all have a core-shell structure.

[0026] Furthermore, by grinding high-iron admixtures and high-calcium admixtures together, the free calcium in the high-calcium admixture can be used to solidify the impurity phosphorus element in the high-iron admixture and improve the early strength of the system. In addition, the surface of the coarse iron particles with high wear resistance will be coated with the easily grinded calcium fine particles to form a high alkalinity area on the surface, which is conducive to the dissolution of insoluble Fe.

[0027] Furthermore, co-grinding aluminum-rich admixtures with high-efficiency activators helps optimize particle size distribution, form surface bond breaks, and enhance hydration activity. Furthermore, the high-efficiency activator coats the surface of aluminum-rich admixture particles, forming a core-shell structure that complexes Fe and Al ions, promoting the formation of iron- and aluminum-containing products.

[0028] Furthermore, the activator includes 20 to 40 parts of a functional complexing agent and 50 to 70 parts of a nano nucleating agent in parts by mass.

[0029] Furthermore, the composite mineral admixture includes the following components, calculated as oxides: CaO3 0.67-33.92%, SiO2 19.51-22.41%, Al2O3 12.99-15.05%, Fe2O3 4.97-5.81%, MgO 3.01-4.22%, and SO3 0.24-1.89%.

[0030] See also Figure 1 The preparation process of the composite mineral admixture of the present invention is as follows:

[0031] (1) mixing the functional complexing agent and the nano nucleating agent in a certain mass ratio and stirring at 45-70° C. for 10-30 min at a stirring speed of 150-300 rpm to form a high-efficiency activator for mineral admixtures;

[0032] (2) mixing the aluminum-rich admixture and the high-efficiency activator according to a mass ratio and grinding them for 10 to 300 minutes at a mill speed of 200 to 500 rpm to form a first powder;

[0033] (3) mixing the high iron admixture and the high calcium admixture according to the mass ratio and grinding them for 10 to 300 minutes at a mill speed of 200 to 500 rpm to form a second powder;

[0034] (4) The first powder and the second powder are mixed and stirred for 30 to 120 minutes at a mixer speed of 150 to 300 rpm to obtain a high-activity, high-graded core-shell structure composite mineral admixture.

[0035] Furthermore, the mass ratio of the high-efficiency activator to the mineral admixture is between 1:15000 and 1:5000.

[0036] Furthermore, the particle size of the high iron admixture is larger than that of the high calcium admixture.

[0037] The main mechanism of action of the present invention:

[0038] (1) The present invention adopts functional complexing agent and nano nucleating agent to form a high-efficiency activator, optimizes the particle size distribution of mineral admixtures, and exerts multiple advantages such as shaping, coating and activation.

[0039] (2) The high calcium admixture and the high iron admixture are ground together, and the free calcium in the high calcium admixture is used to solidify the impurity phosphorus element in the high iron admixture, thereby improving the strength of the system. At the same time, the high calcium admixture with fine particles having a median particle size D(0.5) between 2 and 10 μm is wrapped on the surface of the high iron admixture with coarse particles D(0.5) between 10 and 18 μm, forming a core-shell structure with the high iron admixture as the core and the high calcium admixture as the shell. The high alkalinity of the surface of this structure after hydration is conducive to the dissolution of iron elements.

[0040] (3) Grinding aluminum-rich admixtures together with high-efficiency activators can promote the formation of polar chemical bonds on the surface, making hydration faster. At the same time, the surface-coated activator can complex calcium and iron ions, promoting the formation of iron and aluminum hydration products. Figure 2 and Figure 3 As shown, in the first powder formed by the present invention, the activator 3 (shell) is coated on the aluminum-rich admixture 4 (core), and in the second powder, the high calcium admixture 1 (shell) is coated on the high iron admixture 2 (core). Therefore, the mixed ternary (high iron, high calcium, rich aluminum) composite admixtures of the present invention all have a core-shell structure, and the dissolution of iron and aluminum ions is excellent.

[0041] (4) The functional complexing agent used in the present invention is an alcohol amine substance, the polar force between its molecules can make the tiny particles repel each other, avoid agglomeration, and achieve the purpose of reducing energy consumption and fully grinding. The nano nucleating agent is a CSH nano crystal core product, which contains a certain amount of polycarboxylic acid water reducer, and achieves the effect of aiding grinding and dispersion through the polar force of the molecular surface. At the same time, the nano crystal core acts as a nucleating agent for cement hydration products, greatly reducing the nucleation barrier of the hydration products of the composite cementitious material system and improving the hydration performance. The ternary composite core-shell structure mineral admixture of the present invention has a reasonable particle size distribution and rapid ion dissolution, has a high hydration activity, can significantly improve the effective utilization rate of the low-activity mineral admixture of the special component, and has a good improvement performance on the corrosion resistance of the cementitious material system.

[0042] In summary, the present invention can realize the large-scale utilization of special component low-activity mineral admixtures in the construction industry, which is conducive to achieving low cost and low carbonization in the building materials industry.

[0043] The present invention is further described in detail below through specific examples.

[0044] Firstly, four high-efficiency activators were prepared using triethanolamine and triisopropanolamine as functional complexing agents and CSH nanocrystal cores as nanonucleating agents, and were named high-efficiency activator ①, high-efficiency activator ②, high-efficiency activator ③, and high-efficiency activator ④ respectively.

[0045] High-efficiency Activator ①: The following reagents are used in parts by mass: triethanolamine: 15 parts, triisopropanolamine: 15 parts, CSH nanocrystal core: 60 parts. Preparation of High-efficiency Activator ①: Mix triethanolamine and triisopropanolamine at room temperature and stir for 20 minutes. Slowly add CSH nanocrystal core, heat to 55°C, and stir for 20 minutes. Keep the stirring vessel sealed throughout the entire process.

[0046] Specifically, compared to conventional methods that use only triethanolamine and / or triisopropanolamine, the CSH nanocrystalline core not only contains polycarboxylate superplasticizer molecules, which aid grinding and dispersion through the polar forces of their molecular surfaces, but more importantly, act as nucleators for cement hydration products, significantly reducing the nucleation barrier of hydration products in composite cementitious materials, increasing the degree of ion dissolution in the cementitious material, improving hydration performance, and promoting the formation of hydration products such as Ca(OH)2. However, the dosage of CSH nanocrystalline cores has a significant impact on the admixture: a low dosage results in a weak nucleation effect, while a high dosage maintains a low nucleation barrier, but the excess polycarboxylate superplasticizer molecules can lead to water exudation and segregation in the cementitious material, resulting in a decrease in strength.

[0047] High-efficiency activator ②: The reagents and mass fractions used are the same as those of high-efficiency activator ①, except that the preparation process is different, that is, triethanolamine, triisopropanolamine and CSH nanocrystal cores are mixed and stirred at room temperature for 20 minutes, and then heated to 55°C and stirred for 20 minutes. The stirring container is sealed during the entire process.

[0048] High-efficiency activator ③: Triethanolamine and triisopropanolamine were used as functional complexing agents, without the addition of CSH nanocrystal cores. The weight percentages of each reagent used were as follows: triethanolamine: 15 parts, triisopropanolamine: 15 parts. High-efficiency activator ③ was prepared as follows: triethanolamine and triisopropanolamine were mixed and stirred at room temperature for 20 minutes, then heated to 55°C and stirred for 20 minutes. The stirring vessel was sealed throughout the entire process.

[0049] High-efficiency activator ④: Triethanolamine and triisopropanolamine are used as functional complexing agents, and CSH nanocrystal cores are used as nanonucleating agents. The weight percentages of each reagent used are as follows: triethanolamine: 15 parts, triisopropanolamine: 15 parts, CSH nanocrystal cores: 80 parts. The preparation process for high-efficiency activator ④ is the same as that for high-efficiency activator ①.

[0050] The above-mentioned high-efficiency activators are statistically analyzed, and their raw material dosages and main process conditions are shown in Table 1 below.

[0051] Table 1 Raw material dosage and main process conditions of high-efficiency activators ①~④

[0052]

[0053] Example 1

[0054] Take 600 parts of metakaolin (Al2O3 content is 41.3%, the metakaolin in the following examples and comparative examples is the same, and the same applies to other raw materials) and high-efficiency activator ① and grind them at 300 rpm for 40 minutes to form a first powder, and the mass ratio of the high-efficiency activator ① to metakaolin is 1:6000; take 400 parts of steel slag (Fe2O3 content is 28.2%) and 800 parts of limestone (CaO content is 53.1%) and mix them, and grind them at 300 rpm for 60 minutes to form a second powder; finally, the first powder and the second powder are fully mixed and ball-milled at 220 rpm for 70 minutes to form a composite mineral admixture.

[0055] Example 2

[0056] Take 500 parts of alum stone (Al2O3 content is 25.86%) and high-efficiency activator ① and grind them at 200rpm for 10 minutes to form a first powder, and the mass ratio of the high-efficiency activator ① to the alum stone is 1:5000; take 300 parts of iron tailings (Fe2O3 content is 16.4%) and 500 parts of fly ash (CaO content is 39.4%) and mix them, and grind them at 10rpm for 200 minutes to form a second powder; finally, the first powder and the second powder are fully mixed, and ball milled at 150rpm for 30 minutes to form a composite mineral admixture.

[0057] Example 3

[0058] Take 700 parts of alum stone and high-efficiency activator ① and grind them at 500 rpm for 300 minutes to form a first powder, where the mass ratio of the high-efficiency activator ① to the alum stone is 1:7000; take 500 parts of iron ore (Fe2O3 content is 38.52%) and 1000 parts of tuff (CaO content is 30.39%) and mix them, and grind them at 500 rpm for 300 minutes to form a second powder; finally, the first powder and the second powder are fully mixed, and ball milled at 300 rpm for 120 minutes to form a composite mineral admixture.

[0059] Example 4

[0060] Take 600 parts of metakaolin and high-efficiency activator ① and grind them at 300 rpm for 120 minutes to form a first powder, where the mass ratio of the high-efficiency activator ① to the metakaolin is 1:6000; take 400 parts of steel slag and iron tailings and mix them with 700 parts of papermaking white mud (CaO content is 52.02%), where the mass ratio of steel slag to papermaking white mud is 1:1, and grind them at 300 rpm for 120 minutes to form a second powder; finally, fully mix the first powder and the second powder, and ball mill them at 190 rpm for 60 minutes to form a composite mineral admixture.

[0061] Example 5

[0062] Take 650 parts of metakaolin and alum stone and grind them with high-efficiency activator ① at 280rpm for 90 minutes to form a first powder, the mass ratio of metakaolin to alum stone is 1:1, and the mass ratio of the high-efficiency activator ① to metakaolin and alum stone is 1:6500; take 420 parts of iron ore and mix them with 900 parts of limestone and tuff, the mass ratio of limestone to tuff is 1:1, and grind them at 400rpm for 180 minutes to form a second powder; finally, fully mix the first powder and the second powder, and ball mill at 280rpm for 90 minutes to form a composite mineral admixture.

[0063] Comparative Example 1

[0064] The high-efficiency activator ① in Example 1 was replaced with the high-efficiency activator ②, and the other materials, dosages and grinding mechanisms remained unchanged, that is: 600 parts of metakaolin and high-efficiency activator ② were ground at 300 rpm for 40 minutes to form a first powder, and the mass ratio of the high-efficiency activator ② to metakaolin was 1:6000; 400 parts of steel slag and 800 parts of limestone were mixed and ground at 300 rpm for 60 minutes to form a second powder; finally, the first powder and the second powder were fully mixed and ball-milled at 220 rpm for 70 minutes to form a composite mineral admixture.

[0065] Comparative Example 2

[0066] The high-efficiency activator ① in Example 1 was replaced with the high-efficiency activator ③, and the other materials, dosages and grinding mechanisms remained unchanged, that is: 600 parts of metakaolin and high-efficiency activator ③ were ground at 300 rpm for 40 minutes to form a first powder, and the mass ratio of the high-efficiency activator ③ to metakaolin was 1:6000; 400 parts of steel slag and 800 parts of limestone were mixed and ground at 300 rpm for 60 minutes to form a second powder; finally, the first powder and the second powder were fully mixed and ball-milled at 220 rpm for 70 minutes to form a composite mineral admixture.

[0067] Comparative Example 3

[0068] The high-efficiency activator ① in Example 1 was replaced with the high-efficiency activator ④, and the other materials, dosages and grinding mechanisms remained unchanged, that is: 600 parts of metakaolin and high-efficiency activator ④ were ground at 300 rpm for 40 minutes to form a first powder, and the mass ratio of the high-efficiency activator ④ to metakaolin was 1:6000; 400 parts of steel slag and 800 parts of limestone were mixed and ground at 300 rpm for 60 minutes to form a second powder; finally, the first powder and the second powder were fully mixed and ball-milled at 220 rpm for 70 minutes to form a composite mineral admixture.

[0069] Comparative Example 4

[0070] Take 2000 parts of limestone and high-efficiency activator ① and grind them thoroughly according to the grinding mechanism of Example 1. The mass ratio of the high-efficiency activator ① to the limestone is 1:20000.

[0071] Comparative Example 5

[0072] 2000 parts of metakaolin and high-efficiency activator ① were fully ground according to the grinding mechanism of Example 1. The mass ratio of the high-efficiency activator ① to the metakaolin was 1:20000.

[0073] Comparative Example 6

[0074] Take 2000 parts of steel slag and high-efficiency activator ① and grind them thoroughly according to the grinding mechanism of Example 1. The mass ratio of the high-efficiency activator ① to the steel slag is 1:20000.

[0075] The particle size distribution of each admixture after grinding was tested, and its ion dissolution rate in 1 mol / L NaOH solution for 4 hours was monitored. Due to the limitations of special component admixtures in replacing cement dosage, Examples 1 to 5 and Comparative Examples 1 to 6 were used to replace 30 wt% P·Ⅰ52.5 cement. Mortar test blocks were prepared in accordance with GB / T17671-2021, and the compressive strength of the mortar blocks after standard curing to different ages was tested, in an effort to reduce production costs while maintaining compressive strength.

[0076] Table 2 Oxide composition of each sample / wt%

[0077]

[0078]

[0079] Table 3 Ion dissolution degree of each sample / mg·L -1

[0080]

[0081] From the chemical composition in Table 2 and Figure 4 It can be seen from the cumulative particle size that the composite mineral admixture of the present invention optimizes the components and particle grading.

[0082] According to the ion dissolution results in Table 3 and Figure 5 The compressive strength at different ages shows that the composite mineral admixture of the present invention has higher dissolution performance, especially in the dissolution capacity of Al and Fe elements. After replacing part of the cement, it has high compressive strength and growth rate. In particular, the composite mineral admixture obtained in Example 2 has a 28-day compressive strength exceeding PI 52.5. After the admixture is treated by the present invention, the activity gap between the admixture and cement is significantly shortened.

[0083] Comparative Examples 1-3 use high-efficiency activators ② to ④ to replace high-efficiency activator ①, respectively, and the compressive strength and growth rate are reduced compared with Example 1. It can be seen from Example 1 and Comparative Example 1 that the high-efficiency activator is better when mixed in steps than when mixed directly. Comparative Example 2 does not contain CSH nanocrystalline cores, which is not as good as the high-efficiency activator in Example 1 with CSH nanocrystalline cores. In Comparative Example 3, the amount of CSH nanocrystalline cores is increased compared with that in Example 1, but the 28-day compressive strength and growth rate of the mortar specimens are significantly reduced, indicating that excessive or insufficient use of CSH nanocrystalline cores will have adverse effects.

[0084] Comparative Examples 4-6 use a single type of mineral admixture. When the high-efficiency activator is added in the same proportion, the effect is not as good as the composite mineral admixture in Example 1. This shows that the present invention uses multiple mineral admixtures for compounding, which can improve the ion dissolution activity and maximize the effective utilization rate of low-grade mineral admixtures.

[0085] The present invention discloses a multi-graded core-shell structure composite mineral admixture and a preparation process thereof. Different activators are used for graded grinding of mineral admixtures with different chemical compositions and physical properties, and the mineral admixtures are activated and particles are optimized to form a core-shell structure composite admixture with high hydration activity. The composition of the multi-graded core-shell structure composite mineral admixture is as follows by weight: high iron admixture: 300-500 parts; aluminum-rich admixture: 500-700 parts; high calcium admixture: 500-1000 parts; functional complexing agent: 20-50 parts; nano nucleating agent: 50-100 parts. The preparation process thereof is as follows: (1) the functional complexing agent and the nano nucleating agent are mixed in a certain mass ratio, and then stirred at 45-70° C. for 10-30 minutes at a stirring speed of 150-300 rpm to form a high-efficiency activator for the mineral admixture. (2) The aluminum-rich admixture and the high-efficiency activator are mixed and ground for 10 to 300 minutes at a mill speed of 200 to 500 rpm to form a first powder; (3) The high-iron admixture and the high-calcium admixture are mixed and ground for 10 to 300 minutes at a mill speed of 200 to 500 rpm to form a second powder; (4) The first powder and the second powder are mixed and stirred for 30 to 120 minutes at a mixer speed of 150 to 300 rpm to obtain a high-activity, high-grade core-shell structure composite mineral admixture. The present invention adopts a treatment method of high-efficiency activator modification and graded grinding to improve the chemical composition of the composite mineral admixture, optimize the particle grading, improve the ion dissolution activity, and maximize the effective utilization rate of low-grade mineral admixtures.

[0086] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A multi-graded core-shell structure composite mineral admixture, characterized in that: The raw materials include an activator and a mineral admixture in a mass ratio of 1:15000 to 1:5000; The mineral admixture comprises, by weight, 300 to 500 parts of a high iron admixture, 500 to 700 parts of an aluminum-rich admixture, and 500 to 1000 parts of a high calcium admixture; The activator comprises 20 to 50 parts of a functional complexing agent and 10 to 70 parts of a nano nucleating agent in parts by mass; The median particle size of the high iron admixture is 10-18 μm; the median particle size of the high calcium admixture is 2-10 μm; The nano nucleating agent is a CSH nanocrystal nucleus with a solid content of 10 to 20%; The preparation process of the multi-graded core-shell structure composite mineral admixture comprises the following steps: The aluminum-rich admixture and the activator are mixed and ground to obtain a first powder; the first powder has a core-shell structure with the aluminum-rich admixture as the core and the activator as the shell; The high iron admixture and the high calcium admixture are mixed and ground to obtain a second powder; the second powder has a core-shell structure with the high iron admixture as a core and the high calcium admixture as a shell; The first powder and the second powder are mixed and stirred evenly to obtain a multi-graded core-shell structure composite mineral admixture; The functional complexing agent adopts at least two of triethanolamine, triisopropanolamine, diethanol monoisopropanolamine and glycerol; the activator is prepared by first mixing the functional complexing agent uniformly at room temperature, then adding the nano nucleating agent, heating to 40-60 DEG C and mixing uniformly.

2. The multi-graded core-shell structure composite mineral admixture according to claim 1, characterized in that: The high iron admixture is a silicon-aluminum mineral admixture with an iron oxide content of 15% to 40% and a volcanic ash effect.

3. The multi-graded core-shell structure composite mineral admixture according to claim 2, characterized in that: The high iron admixture includes one or more of steel slag, iron tailings and iron ore.

4. The multi-graded core-shell structure composite mineral admixture according to claim 1, characterized in that: The high calcium admixture is a silicon-aluminum mineral admixture with a calcium oxide content of 30% to 80% and a pozzolanic effect.

5. The multi-graded core-shell structure composite mineral admixture according to claim 4, characterized in that: The high calcium admixture includes one or more of limestone, fly ash, tuff and papermaking white mud.

6. The multi-graded core-shell structure composite mineral admixture according to claim 1, characterized in that: The aluminum-rich admixture is a silicon-aluminum mineral admixture with an aluminum oxide content of 20% to 60% and a volcanic ash effect.

7. The multi-graded core-shell structure composite mineral admixture according to claim 6, characterized in that: The aluminum-rich admixture includes one of metakaolin and alum stone or a mixture of the two in any proportion.

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