A self-cementing steel slag graded aggregate and its preparation method

Abstract

The present invention relates to a self-cementing steel slag graded aggregate and a preparation method thereof, belonging to the technical field of solid waste treatment, and solving one of the problems such as the need for additional binder addition, large immersion expansion rate, and poor mechanical properties in the prior art for steel slag graded aggregate. The self-cementing steel slag graded aggregate disclosed in the present invention is prepared from aged steel slag aggregate activated by a surface activator. The specific composition of this surface activator is, by mass: 50-60% of tripotassium citrate, 30-40% of trisodium citrate, and 10-20% of sodium silicate, with a total of 100%. The above-mentioned steel slag graded aggregate can be formed without additional binder addition, has excellent mechanical strength, anti-deformation ability, and low immersion expansion rate, can be widely used in fields such as road surface paving and concrete preparation, and at the same time realizes the disposal of steel slag solid waste.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, and particularly relates to a self-cementing steel slag graded aggregate and a preparation method thereof. Background Art

[0002] A large amount of piled steel slag is difficult to be utilized, resulting in environmental pollution risks and resource waste; at the same time, the excavation of stone quarries is severely restricted, resulting in a serious shortage of natural aggregate supply for projects, thus making the engineering demand and natural aggregate supply form an irreconcilable contradiction. However, as a solid waste from the steelmaking activities of steel mills, steel slag has excellent mechanical properties, angularity and wear resistance, and is an excellent substitute for natural aggregates.

[0003] Through heat soaking, aging and other treatment processes, the content of free calcium oxide f-CaO in steel slag can be inhibited to a certain extent. The expansion rate of steel slag aggregate after long-term aging can meet the specification requirements and can be applied to road paving projects to replace natural aggregates, with excellent economic and environmental benefits. The mineral composition of steel slag aggregate is similar to that of cement clinker, mainly including dicalcium silicate, tricalcium silicate, dicalcium ferrite, etc. However, due to a certain amount of completely solid-solved RO phase in steel slag, the solid solution phase wraps the active minerals, making it difficult for steel slag to exhibit cementitious properties and having an extremely low hydration rate. Therefore, the existing technology needs to use binders such as cement and lime to cement and press the steel slag aggregate into shaped steel slag graded aggregate, and the mechanical properties and immersion expansion rate are poor. Summary of the Invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide a self-cementing steel slag graded aggregate and a preparation method thereof, so as to solve one of the problems that the existing steel slag graded aggregate (formed parts) needs to add additional binders, has poor mechanical properties and a high immersion expansion rate.

[0005] The "self-cementation of steel slag aggregate" described in the present invention means that "without adding binders such as cement and lime, the steel slag aggregate is cemented and hardened through its own cementitious characteristics, thereby achieving the effects of improving the bearing capacity, mechanical strength and anti-deformation ability". The above "cementitious characteristics" refer to "the property that the active minerals in the steel slag aggregate produce hydration products under excitation conditions, and the hydration products dissolve, coagulate and harden to firmly cement the steel slag aggregate together".

[0006] The present invention discloses a self-cementing steel slag graded aggregate, which is prepared from aged steel slag aggregate activated by a surface activator. The specific composition of this surface activator is, by mass: 50-60% of tripotassium citrate, 30-40% of trisodium citrate, and 10-20% of sodium silicate, with a total of 100%.

[0007] Furthermore, the specific composition of the surface activator is: 50-55% tripotassium citrate, 30-35% trisodium citrate, 13-17% sodium silicate, which is 100% in total by mass.

[0008] Furthermore, the aged steel slag aggregate is hot-suffused steel slag aggregate from a steel mill, which has been aged for no less than 6 months and has a water expansion rate of ≤2%.

[0009] Furthermore, the tripotassium citrate, trisodium citrate and sodium silicate in the surface activator are all of analytical grade or above.

[0010] The present invention also discloses a method for preparing the steel slag graded crushed stone, which is characterized by:

[0011] S1: batching the aged steel slag aggregate according to the grading requirements, and drying or airing it to make its surface dry;

[0012] S2: dissolving the surface activator in water and stirring evenly to prepare an activation solution;

[0013] S3: pouring the activation solution into the steel slag aggregate and mixing and stirring to obtain a mixture;

[0014] S4: Use a vibration compactor to form a test piece. Put the mixture of S3 into the vibration compactor to form a steel slag graded gravel test piece. After standing and demoulding, put it into a curing box for curing.

[0015] Specifically, the grading requirements of the aged slag aggregate are: the percentage passing through the sieve hole size of 31.5 mm is 100%, the percentage passing through the sieve hole size of 26.5 mm is 95-100%, the percentage passing through the sieve hole size of 19.0 mm is 68-86%, the percentage passing through the sieve hole size of 9.5 mm is 38-58%, the percentage passing through the sieve hole size of 4.75 mm is 22-32%, the percentage passing through the sieve hole size of 2.36 mm is 16-28%, the percentage passing through the sieve hole size of 0.6 mm is 8-15%, and the percentage passing through the sieve hole size of 0.075 mm is 0-3%.

[0016] Specifically, the mixture composition of S3 is 100 parts by weight of aged steel slag aggregate (after grading), 0.5-2.0 parts of surfactant, and 1.5-3.5 parts of water.

[0017] Specifically, the mixture composition of S3 is 100 parts by weight of aged steel slag aggregate (after grading), 1.0-1.5 parts of surfactant, and 2.5-3 parts of water.

[0018] Specifically, the stirring time in step S3 is ≥100 s.

[0019] Specifically, step S4 comprises placing the material stirred in S3 into a vibrating compactor, adjusting the parameters to a vibration frequency of 30 Hz, an exciting force of 6.8-6.9 kN, and an amplitude of 1.2 mm to form the mixture, demolding the mixture after standing for 2-6 hours, and then placing the specimen in a curing box for curing.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] a) The dicalcium silicate, tetracalcium aluminoferrate, dicalcium ferrite, and tricalcium silicate on the surface of the steel slag aggregate react with the tripotassium citrate, trisodium citrate, and sodium silicate in the surface activator to produce compounds (or compositions) such as ferric citrate complex, grossular garnet, almandine, and hydrated calcium aluminosilicate. Among them, grossular garnet, almandine, and hydrated calcium aluminosilicate are typical hydrated gelling products (i.e., gelling substances), which can be dissolved in water and solidify and harden, thereby firmly bonding the steel slag aggregate together. The self-gelling of steel slag graded crushed stone is achieved without the need to add additional binders such as cement and lime.

[0022] b) The present invention realizes in-situ surface gelling of steel slag aggregate by adding surface activators and adopting supporting treatment processes. Since the surface active substances of steel slag are directly activated in-situ, the gelling substances are evenly distributed on the surface of steel slag aggregate. Compared with adding cement, lime and other binders, the distribution of gelling substances is more uniform, which significantly reduces the possibility of false adhesion of steel slag graded crushed stone caused by uneven mixing of binders, and improves the mechanical properties and deformation resistance of steel slag graded crushed stone.

[0023] c) Through the in-situ surface gelation of steel slag aggregate, gelling material can be produced on the surface of steel slag and wrap the steel slag aggregate, which can effectively reduce the water expansion rate of the graded steel slag mixture and improve the stability of the steel slag aggregate.

[0024] d) The self-gelling steel slag graded crushed stone of the present invention has self-gelling characteristics, excellent mechanical properties and deformation resistance (high CBR value), and low water expansion rate. In addition to being applicable to traditional road paving, concrete preparation and other fields, it has the potential to explore the utilization of steel slag aggregates, which is helpful to promote the disposal and reuse of steel slag solid waste materials.

[0025] e) The preparation method of the present invention has simple process, relevant raw materials and equipment are easily available, the product performance is excellent and stable, and it is conducive to large-scale production and application.

[0026] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. Brief Description of the Drawings

[0027] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation of the present invention. Throughout the drawings, the same reference signs denote the same components.

[0028] Figure 1 It is a schematic flow chart of the preparation method of self-cementitious steel slag graded aggregate.

[0029] Figure 2 It is the surface microscopic morphology of the in-situ excitation product of the steel slag aggregate in Control Group 1.

[0030] Figure 3 It is the surface microscopic morphology of the in-situ excitation product of the steel slag aggregate in Example 1.

[0031] Figure 4 It is the surface microscopic morphology of the in-situ excitation product of the steel slag aggregate in Example 2. Detailed Embodiments

[0032] The following will specifically describe the preferred embodiments of the present invention in conjunction with the drawings, wherein the drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, and are not used to limit the scope of the present invention.

[0033] The present invention discloses a self-cementitious steel slag graded aggregate, and the steel slag graded aggregate is prepared from aged steel slag aggregate activated by a surface activator. The specific composition of this surface activator is, by mass: potassium citrate 50 - 60%, sodium citrate 30 - 40%, sodium silicate 10 - 20%, and the total of the three is 100%.

[0034] The functions / synergistic effects and ratios of the components in the present invention are as follows:

[0035] Potassium citrate / sodium citrate;

[0036] Potassium citrate has outstanding activation efficiency for coarse steel slag aggregate, but its price is relatively high; sodium citrate has excellent activation effect on fine steel slag aggregate and low price. Potassium citrate and sodium citrate act synergistically, and can greatly activate products such as dicalcium silicate, tetracalcium aluminoferrite, and dicalcium ferrite on the surface of coarse and fine steel slag aggregates, generating calcium-aluminum garnet and iron-aluminum garnet (cementitious substances), and producing a more excellent cementitious activation effect. Considering factors such as the relatively high content of coarse aggregate (about 60%) in the steel slag graded aggregate and economic costs, the composition of the surface activator is adjusted to potassium citrate 50 - 60% and sodium citrate 30 - 40%.

[0037] Sodium silicate: Sodium silicate can provide a strong alkaline environment, which is conducive to the hydration reaction. At the same time, silicate can react with tricalcium silicate in steel slag to produce hydrated calcium aluminosilicate (gelling material). Tripotassium citrate and trisodium citrate do not react with tricalcium silicate, so sodium silicate complements the combination of tripotassium citrate and trisodium citrate. For steel slag aggregates with a relatively small specific surface area, the preferred range of sodium silicate is 13.00%-17.00%. It is speculated that the specific reason may be that the specific surface area of the steel slag aggregate is small, the tricalcium silicate is not fully exposed, and a lower content of sodium silicate can meet the stimulation requirements.

[0038] The present invention also discloses a method for preparing the steel slag graded crushed stone, which is characterized by comprising the following steps:

[0039] S1: batching the aged steel slag aggregate according to the grading requirements, and drying or airing it to make its surface dry;

[0040] S2: dissolving the surface activator in water and stirring evenly to prepare an activation solution;

[0041] S3: pouring the activation solution into the steel slag aggregate and mixing and stirring to obtain a mixture;

[0042] In this process, most of tripotassium citrate, trisodium citrate and sodium silicate react with metal compounds such as dicalcium silicate, tricalcium silicate and dicalcium ferrite on the surface of the steel slag aggregate to generate compounds such as ferric citrate complex, grossular garnet, almandine and hydrated calcium aluminosilicate (cementitious substances), thereby activating the surface of the steel slag aggregate and uniformly coating the surface of the steel slag aggregate.

[0043] S4: Use a vibration compactor to form a test piece. Put the mixture of S3 into the vibration compactor to form a steel slag graded gravel test piece. After standing and demoulding, put it into a curing box for curing.

[0044] In this process, the steel slag aggregates that have been uniformly wrapped by the cementitious material are bonded to each other through the vibration and static process to form a uniform and relatively stable steel slag graded gravel specimen. At the same time, the components such as tripotassium citrate, trisodium citrate, sodium silicate, dicalcium silicate, tricalcium silicate, dicalcium ferrite, etc. that have not yet reacted completely can still react further to form cementitious materials.

[0045] Specifically, the grading requirements for the aged steel slag aggregate are as follows: the percentage passing through a sieve with a mesh size of 31.5 mm is 100%, the percentage passing through a sieve with a mesh size of 26.5 mm is 95 - 100%, the percentage passing through a sieve with a mesh size of 19.0 mm is 68 - 86%, the percentage passing through a sieve with a mesh size of 9.5 mm is 38 - 58%, the percentage passing through a sieve with a mesh size of 4.75 mm is 22 - 32%, the percentage passing through a sieve with a mesh size of 2.36 mm is 16 - 28%, the percentage passing through a sieve with a mesh size of 0.6 mm is 8 - 15%, and the percentage passing through a sieve with a mesh size of 0.075 mm is 0 - 3%. This grading standard strictly limits the distribution ratio of steel slag gravel with different particle sizes, helps to form a framework dense structure, realizes the relatively tight filling of the steel slag aggregate, is conducive to the shaping of the steel slag aggregate, and improves the bearing capacity of the final shaped part.

[0046] Specifically, the composition of the mixture in S3 is, by weight, 100 parts of the graded and aged steel slag aggregate, 0.5 - 2.0 parts of the surface activator, and 1.5 - 3.5 parts of water. While ensuring the activation effect, the addition amount of the surface activator and the amount of water are reduced to ensure that the graded gravel reaches the maximum density as much as possible while reducing the economic cost.

[0047] Specifically, the preferred composition of the mixture in S3 is, by weight, 100 parts of the graded and aged steel slag aggregate, 1.0 - 1.5 parts of the surface activator, and 2.5 - 3 parts of water.

[0048] Specifically, the stirring time in step S3 is ≥100 s to ensure the mixing effect and the relatively sufficient reaction of the surface activator with metal compounds such as dicalcium silicate, tricalcium silicate, and dicalcium ferrite.

[0049] Specifically, the specific steps of step S4 are to put the stirred material in S03 into a vibrating compactor, adjust the parameters to a vibration frequency of 30 Hz, an exciting force of 6.8 - 6.9 kN, and an amplitude of 1.2 mm to form the mixture. After standing for 2 - 6 h, demold, and then put the specimen into a curing box for curing. The specific operation method and parameters are common processes in the industry, ensuring the reliability of the steel slag graded gravel shaped part.

[0050] Example 1:

[0051] 1000 g of steel slag aggregate, 15 g of activator, and 31 g of water. The composition of the surface activator, by mass, is 9.0 g of tripotassium citrate, 4.5 g of trisodium citrate, and 1.5 g of sodium silicate. The composition ratio of the steel slag aggregate, by weight percentage, includes: 26% of material 1 with a particle size of 20 - 30 mm, 18% of material 2 with a particle size of 10 - 20 mm, 31% of material 3 with a particle size of 5 - 10 mm, and 25% of material 4 with a particle size of 0 - 5 mm.

[0052] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 30 Hz, exciting force 6.9 kN, and amplitude 1.2 mm to obtain Example 1 of activated steel slag graded crushed stone.

[0053] Example 2:

[0054] 1000 g of steel slag aggregate, 5 g of activator, and 28 g of water. The surface activator consists of 2.5 g of tripotassium citrate, 1.5 g of trisodium citrate, and 1 g of sodium silicate by mass. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0055] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 30 Hz, exciting force 6.9 kN, and amplitude 1.2 mm to obtain Example 2 of activated steel slag graded crushed stone.

[0056] Example 3:

[0057] 1000 g of steel slag aggregate, 10 g of activator, and 27 g of water. The surface activator consists of 5 g of tripotassium citrate, 3.3 g of trisodium citrate, and 1.7 g of sodium silicate by mass. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0058] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 29 Hz, exciting force 6.8 kN, and amplitude 1.2 mm to obtain Example 3 of activated steel slag graded crushed stone.

[0059] Example 4:

[0060] 1000 g of steel slag aggregate, 10 g of activator, and 26 g of water. The surface activator consists of 5.5 g of tripotassium citrate, 3.5 g of trisodium citrate, and 1.0 g of sodium silicate by mass. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0061] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 29 Hz, exciting force 6.8 kN, and amplitude 1.2 mm to obtain Example 4 of activated steel slag graded gravel.

[0062] Example 5:

[0063] 1000 g of steel slag aggregate, 12 g of activator, and 28 g of water. The activator composition by mass is 6.6 g of tripotassium citrate, 3.6 g of trisodium citrate, and 1.8 g of sodium silicate. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0064] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 29 Hz, exciting force 6.9 kN, and amplitude 1.2 mm to obtain Example 5 of activated steel slag graded gravel.

[0065] Control Group 1:

[0066] 1000 g of steel slag aggregate and 30 g of water. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0067] Add water to the steel slag aggregate and stir for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 30 Hz, exciting force 6.9 kN, and amplitude 1.2 mm to obtain uncemented graded steel slag mixture as Control Group 1.

[0068] Control Group 2:

[0069] 1000 g of steel slag aggregate, 15 g of activator, and 2.8 g of water. The surface activator includes 2.2 g of tripotassium citrate and 11.8 g (excessive) of trisodium citrate, and 1.0 g of sodium silicate. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of No. 1 material with a particle size of 20 - 30 mm, 18% of No. 2 material with a particle size of 10 - 20 mm, 31% of No. 3 material with a particle size of 5 - 10 mm, and 25% of No. 4 material with a particle size of 0 - 5 mm.

[0070] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 30 Hz, exciting force 6.9 kN, and amplitude 1.2 mm to obtain the activated steel slag graded crushed stone control group 2.

[0071] Control group 3:

[0072] 1000 g of steel slag aggregate, 25 g of activator, and 28 g of water. The surface activator includes 15 g of tripotassium citrate, 7.5 g of trisodium citrate, and 1.5 g of sodium silicate. The composition ratio of the steel slag aggregate by weight percentage includes: 26% of #1 material with a particle size of 20 - 30 mm, 18% of #2 material with a particle size of 10 - 20 mm, 31% of #3 material with a particle size of 5 - 10 mm, and 25% of #4 material with a particle size of 0 - 5 mm.

[0073] Dissolve the surface activator in water, add the activation solution to the steel slag aggregate and stir well for 100 s. Put the stirred material into a vibrating compactor with pressure parameters of vibration frequency 29 Hz, exciting force 6.8 kN, and amplitude 1.2 mm to obtain the activated steel slag graded crushed stone control group 3.

[0074] For the above - mentioned examples and control groups, use a vibrating compactor to form specimens, and then conduct CBR tests and immersion expansion rate tests to measure the anti - deformation ability and stability of the graded steel slag mixture, and compare the influence of in - situ surface cementation of steel slag aggregate on the mechanical strength and stability of steel slag aggregate; meanwhile, use a scanning electron microscope to observe the microscopic morphology of the in - situ surface - activated products of steel slag aggregate.

[0075] Through testing, the following test data are obtained:

[0076] The CBR value (i.e., California Bearing Ratio) is an index for evaluating the bearing capacity of subgrade and pavement materials. It is defined by the ability of the material to resist the indentation deformation of local loads, and uses the bearing capacity of standard crushed stone as the standard, and expresses the CBR value as a percentage of the relative value. The higher the CBR value, the stronger the bearing capacity and anti - deformation ability.

[0077] Table 1 CBR test results of control groups and examples

[0078]

[0079]

[0080] The immersion expansion rate refers to the volume expansion rate of the steel slag graded crushed stone soaked in a 90 °C water bath for 10 d. The specific data are shown in Table 2:

[0081] Table 2 Immersion expansion test results of control groups and examples

[0082]

[0083] As can be seen from the above test results, the surface activator compounded with tripotassium citrate, trisodium citrate and sodium silicate can effectively activate the active substances on the in-situ surface of the steel slag aggregate, causing a large amount of cementitious substances to be generated on the steel slag surface and exhibiting cementitious properties, thus showing excellent mechanical strength and anti-deformation ability (the CBR value is significantly increased). The CBR value can reach 324%-355% (7 days), 357%-378% (14 days), 368%-396% (28 days), and 374%-411% (90 days).

[0084] Meanwhile, the generated cementitious products wrap the surface of the steel slag aggregate, thereby reducing the immersion expansion rate of the steel slag mixture and improving the soundness of the steel slag aggregate. According to the experimental data, the immersion expansion rate (10 days) of the example is reduced to 1.24%-1.34%, which is significantly lower than that of the comparative example.

[0085] Comparing the control group 2 and the example, when the content of trisodium citrate in the surface activator is too high, the activation effect of the activator is poor, and the mechanical properties and immersion expansion rate of the formed parts are not ideal. Comparing the control group 3 and the example, when the content of tripotassium citrate in the surface activator is too high (more than 60%), the mechanical properties and immersion expansion rate of the formed parts are comparable to those of the example, without significant improvement, but the economic cost increases significantly, which is not the recommended content composition range of the present invention.

[0086] The above steel slag graded crushed stone can be formed without additional binder, has excellent mechanical strength, anti-deformation ability and low immersion expansion rate, and can be widely used in fields such as road paving and concrete preparation, while realizing the disposal of steel slag solid waste.

[0087] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A self-gelling steel slag graded gravel, characterized by: The steel slag graded crushed stone is prepared by activating aged steel slag aggregate with a surface activator, wherein the specific composition of the surface activator is: 50-60% tripotassium citrate, 30-40% trisodium citrate, 10-20% sodium silicate, which is 100% in total; The aged steel slag aggregate is hot-suffused steel slag aggregate from a steel mill, which has been aged for no less than 6 months and has a water expansion rate of ≤2%; The grading requirements of the aged steel slag aggregate are: the percentage passing through the sieve hole size of 31.5 mm is 100%, the percentage passing through the sieve hole size of 26.5 mm is 95-100%, the percentage passing through the sieve hole size of 19.0 mm is 68-86%, the percentage passing through the sieve hole size of 9.5 mm is 38-58%, the percentage passing through the sieve hole size of 4.75 mm is 22-32%, the percentage passing through the sieve hole size of 2.36 mm is 16-28%, the percentage passing through the sieve hole size of 0.6 mm is 8-15%, and the percentage passing through the sieve hole size of 0.075 mm is 0-3%.

2. The steel slag graded aggregate according to claim 1, wherein: The specific composition of the surfactant is as follows by mass: 50-55% tripotassium citrate, 30-35% trisodium citrate, and 13-17% sodium silicate, which is 100% in total.

3. The steel slag graded crushed stone according to claim 1 or 2, wherein: The tripotassium citrate, trisodium citrate and sodium silicate in the surfactant are all of analytical grade or above.

4. A method for preparing the slag graded crushed stone according to any one of claims 1 to 3, characterized in that: S1: batching the aged steel slag aggregate according to the grading requirements, and drying or airing it to make its surface dry; S2: dissolving the surface activator in water and stirring evenly to prepare an activation solution; S3: pouring the activation solution into the steel slag aggregate and mixing and stirring to obtain a mixture; S4: Use a vibration compactor to form a test piece. Put the mixture of S3 into the vibration compactor to form a steel slag graded gravel test piece. After standing and demoulding, put it into a curing box for curing.

5. The preparation method according to claim 4, characterized in that: The grading requirements of the aged steel slag aggregate are: the percentage passing through the sieve hole size of 31.5 mm is 100%, the percentage passing through the sieve hole size of 26.5 mm is 95-100%, the percentage passing through the sieve hole size of 19.0 mm is 68-86%, the percentage passing through the sieve hole size of 9.5 mm is 38-58%, the percentage passing through the sieve hole size of 4.75 mm is 22-32%, the percentage passing through the sieve hole size of 2.36 mm is 16-28%, the percentage passing through the sieve hole size of 0.6 mm is 8-15%, and the percentage passing through the sieve hole size of 0.075 mm is 0-3%.

6. The preparation method according to claim 4, characterized in that: The mixture composition S3 is composed of 100 parts by weight of graded aged steel slag aggregate, 0.5-2.0 parts by weight of surfactant, and 1.5-3.5 parts by weight of water.

7. The preparation method according to claim 4, characterized in that: The mixture composition S3 is composed of 100 parts by weight of graded aged steel slag aggregate, 1.0-1.5 parts by weight of surfactant, and 2.5-3 parts by weight of water.

8. The preparation method according to claim 4, characterized in that: The stirring time in step S3 is ≥100s.

9. The preparation method according to claim 4, characterized in that: The specific steps of step S4 are as follows: put the stirred material in step S3 into a vibrating compactor, and adjust the parameters to a vibration frequency of 28 - 30 Hz, an exciting force of 6.8 - 6.9 kN, and an amplitude of 1.2 mm; form the mixture, demold it after standing for 2 - 6 h, and then put the specimen into a curing box for curing.

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