An activator and its application method

Abstract

The present invention relates to an activator and its application method, belonging to the technical field of solid waste treatment, and solves one of the problems in the prior art that the gelling activation effect of steel slag powder is poor, the hydration rate is slow, and the mechanical properties are relatively poor. The present invention discloses an activator, which is used for the gelling activation of steel slag powder. Its specific composition is by mass: potassium citrate 8.33 - 60.00%, sodium citrate 28.00 - 80.65%, sodium silicate 7.89 - 44.44%, with a total of 100%. The above-mentioned activator can significantly stimulate the gelling activity of steel slag powder, enabling the steel slag powder to achieve self-gelling without adding adhesives, and having excellent mechanical strength after forming and hardening. It can be widely applied to fields such as low-carbon cementitious materials and concrete, and at the same time realizes the consumption 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 an activator for steel slag powder cementitious activation and an application method thereof. Background Art

[0002] As a solid waste from the steelmaking activities of steel plants, the annual output of steel slag is nearly 100 million tons. A large amount of steel slag is difficult to dispose of and stack, occupying land resources and causing serious environmental pollution. The mineral composition of steel slag is similar to that of cement clinker, mainly including dicalcium silicate, tricalcium silicate, dicalcium ferrite, etc., and at the same time contains some iron oxides and free calcium oxide f-CaO. Due to the presence of f-CaO, there are certain soundness problems when using steel slag as an aggregate. Therefore, by grinding steel slag into steel slag powder, the specific surface area of steel slag can be effectively increased, and to a certain extent, the hydration rate and cementitious activity of steel slag powder can be improved.

[0003] However, due to the doping effect of iron oxide phases in steel slag, the hydration ability of steel slag powder is still insufficient, and its cementitious activity is still much lower than that of binders such as cement and lime. It is impossible to achieve the self-cementation of steel slag powder, and there is currently no relatively mature activator or stimulant that can be used on a large scale to enhance the cementitious activity of steel slag powder. Summary of the Invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide an activator and an application method thereof to solve one of the problems of poor cementitious activation effect, slow hydration rate, and poor mechanical properties of existing steel slag powder.

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

[0006] The present invention discloses an activator for steel slag powder cementitious activation. The specific composition is as follows by mass percentage: potassium citrate 8.33% - 60.00%, sodium citrate 28.00% - 80.65%, sodium silicate 7.89% - 44.44%, and the total is 100%.

[0007] Specifically, the steel slag powder contains one or more of dicalcium silicate, tricalcium silicate, tetracalcium aluminoferrite, and dicalcium ferrite.

[0008] Specifically, the potassium citrate, sodium citrate, and sodium silicate are all of analytical reagent grade or above.

[0009] Specifically, the specific composition of the activator is: 12.00%-22.00% tripotassium citrate, 34.00%-63.00% trisodium citrate, 20.00%-35.00% sodium silicate, which is 100% in total.

[0010] The invention also discloses an application method of the activator, and the process is as follows: dissolving the activator in water to obtain an activator solution, pouring the solution into steel slag powder and stirring to obtain an activated steel slag slurry, pouring the activated steel slag slurry into a test mold and vibrating the solution to obtain a test piece.

[0011] Specifically, the above application method includes the following steps:

[0012] S1: Take a certain amount of steel slag powder, dry it and weigh it;

[0013] S2: Weigh a certain amount of activator and dissolve it in an appropriate amount of water, and stir evenly to prepare an activator solution;

[0014] S3: first pour the steel slag powder into a mortar mixer, then pour the activator solution into the steel slag powder and stir to obtain activated steel slag slurry;

[0015] S4: Pour the excited steel slag slurry into the test mold and vibrate it, let it stand and then demould it. After demoulding, put the test piece into the curing box for curing.

[0016] Specifically, in step S2, the activator is 1%-2% of the mass of the steel slag powder after drying in step S1, in terms of mass percentage.

[0017] Specifically, in step S2, the appropriate amount of water is 15%-35% of the mass of the steel slag after drying in step S1, calculated by mass percentage.

[0018] Preferably, the specific composition of the activator is calculated by mass percentage as follows: 50.00%-60.00% tripotassium citrate, 30%.00-40.00% trisodium citrate, and 10.00%-20.00% sodium silicate, which is 100% in total.

[0019] The present invention also discloses an application method of the activator for preparing a self-gelling steel slag graded crushed stone, and the specific steps are as follows:

[0020] S01: batching and drying the aged steel slag aggregate according to the grading requirements;

[0021] S02: dissolving the activator in water and stirring evenly to prepare an activator solution;

[0022] S03: pouring the activator solution into the steel slag aggregate and mixing and stirring to obtain a mixture;

[0023] S04: Use a vibrating compactor to form specimens. Put the mixture of S03 into the vibrating compactor to form steel slag graded crushed stone specimens. After standing and demolding, place them in a curing box for curing.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] a) Dicalcium silicate, tetracalcium aluminoferrite, dicalcium ferrite, and tricalcium silicate on the surface of steel slag powder react with tripotassium citrate, trisodium citrate, and sodium silicate in the activator to produce compounds (or compositions) such as iron citrate complex, grossular, almandine, and calcium silicoaluminate hydrate. Among them, grossular, almandine, and calcium silicoaluminate hydrate are hydrated cementitious products (i.e., cementitious substances), which can dissolve in water and coagulate and harden. Therefore, after the activator activates the cementitious activity of steel slag powder, the cementitious activity of steel slag powder is greatly improved. In the case of no binders such as cement and lime, the hydration of the minerals in steel slag powder itself is fully stimulated, realizing the self-cementation of steel slag powder, and then greatly improving the mechanical strength of the hardened steel slag powder paste specimens, and can reach the strength of P.O 42.5 grade cement mortar.

[0026] b) The present invention realizes the in-situ surface cementation of steel slag powder by adding an activator and adopting a supporting application method, etc. Since the active substances of steel slag powder are directly excited in-situ, the cementitious substances are evenly distributed on the surface of steel slag powder. Compared with adding binders such as cement and lime, the distribution of cementitious substances is more uniform, significantly reducing the possibility of local false adhesion of steel slag powder paste specimens caused by uneven mixing of binders, and improving the mechanical properties and anti-deformation ability of steel slag powder paste specimens.

[0027] c) Through the in-situ surface cementation of steel slag powder, cementitious substances can be generated on the surface of steel slag powder and wrap the steel slag powder, which can effectively reduce the water absorption of steel slag powder, improve the soundness of steel slag powder paste specimens, is conducive to expanding the uses and application fields of steel slag powder, and helps to dispose of steel slag solid waste.

[0028] d) The activator disclosed in the present invention has easily available raw materials and is simple to prepare; the application method involves common equipment and conventional operations, and the process is simple, the implementation conditions are mild, the economic cost is low, and it is suitable for large-scale production.

[0029] e) The self-cementing steel slag graded crushed stone of the present invention has self-cementing characteristics, excellent mechanical properties and anti-deformation ability (high CBR value), and low immersion expansion rate. In addition to being applicable to traditional road paving, concrete preparation and other fields, it has the potential to develop the utilization ways of steel slag aggregates, and helps to promote the disposal and reuse of steel slag solid waste materials.

[0030] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combined solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be made obvious from the description, or can be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained from the content specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs denote the same components.

[0032] Figure 1 It is a schematic flow chart of the application method of the activator of the present invention;

[0033] Figure 2 It is the microscopic morphology of the hydration products of the specimen 1-1 in the control group;

[0034] Figure 3 It is the microscopic morphology of the hydration products of the specimen 1-1 in Example 1;

[0035] Figure 4 It is the microscopic morphology of the hydration products of the specimen 1-2 in Example 1;

[0036] Figure 5 It is the XRD patterns of the specimens of the control group 1-1 and Examples 1-1, 1-2, and 1-3;

[0037] Figure 6 It is a schematic flow chart of the preparation method of self-cementitious steel slag graded aggregate;

[0038] Figure 7 It is the surface microscopic morphology of the in-situ excitation products of the steel slag aggregate in the control group 2-1;

[0039] Figure 8 It is the surface microscopic morphology of the in-situ excitation products of the steel slag aggregate in Example 2-1;

[0040] Figure 9 It is the surface microscopic morphology of the in-situ excitation products of the steel slag aggregate in Example 2-2;

[0041] Figure 10 It is the comparison chart of the hydration heat of Example 1-1 and the control group 1-1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The preferred embodiments of the present invention will be specifically described below with reference to the drawings. 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.

[0043] A specific embodiment of the present invention discloses an activator for the cementitious activation of steel slag powder. Its specific composition by mass is as follows: tripotassium citrate 8.33 - 60.00%, trisodium citrate 28.00 - 80.65%, sodium silicate 7.89 - 44.44%, and the total of the three is 100%.

[0044] The functions / synergistic effects and ratio basis of each component in the present invention are as follows:

[0045] Tripotassium citrate / trisodium citrate: The citrate radicals contained in tripotassium citrate and trisodium citrate have a strong complexing effect on iron impurities in the steel slag powder minerals, forming iron citrate complexes, thereby increasing the hydration reaction rate of minerals such as dicalcium silicate, tetracalcium aluminoferrite, and calcium ferrite in the steel slag powder. Among them, tripotassium citrate containing K + ions and trisodium citrate containing Na + ions have a synergistic promoting effect on the activation of steel slag powder, producing hydrated sodium aluminosilicate or hydrated potassium aluminosilicate ((K,Na)-A-S-H) hydration products, and the above hydration products are all cementitious substances. The action mechanisms of tripotassium citrate and trisodium citrate are similar. The activation effect of tripotassium citrate is slightly better, but the economic cost is higher. Therefore, an activator formula with an appropriately increased trisodium citrate ratio is selected to reduce the material cost while ensuring the excitation effect.

[0046] Through experimental tests, when tripotassium citrate is 8.33 - 60.00% and trisodium citrate is 28.00 - 80.65%, the excitation of steel slag powder can be achieved. For steel slag powder with a relatively large specific surface area, appropriately reducing the content of tripotassium citrate has little effect on the excitation effect and can significantly reduce the preparation cost. The content can be optimized to tripotassium citrate 12.00% - 22.00% and trisodium citrate 34.00% - 63.00% (refer to Examples 1-1, 1-2, 1-3, 1-4). For steel slag aggregates with a relatively small specific surface area, excessive reduction of the content of tripotassium citrate will lead to a decline in the performance of steel slag graded gravel. After testing, when the component content meets tripotassium citrate 50.00% - 60.00% and trisodium citrate 30.00% - 40.00%, the performance of steel slag graded gravel is relatively excellent.

[0047] Sodium silicate: Sodium silicate can provide a strong alkaline environment, which is beneficial to the progress of the hydration reaction. At the same time, silicate ions can undergo hydration reactions with tricalcium silicate in steel slag, and sodium silicate can react with tricalcium silicate to produce calcium silicoaluminate hydrate (a gelling substance). Potassium citrate and sodium citrate do not react with tricalcium silicate. Therefore, sodium silicate plays a supplementary role for the combination of potassium citrate and sodium citrate. After testing, controlling the sodium silicate content in the activator at a relatively low level of 7.89 - 44.44% can achieve a good activation effect. Further, for steel slag powder with a larger specific surface area, the preferred range of sodium silicate is 20.00% - 35.00%; for steel slag aggregate with a relatively small specific surface area, the preferred range of sodium silicate is 10.00% - 20.00%. It is speculated that the specific reason may be that due to the larger specific surface area of steel slag powder, tricalcium silicate can be more fully exposed, thereby enabling sodium silicate to play a greater role.

[0048] Potassium citrate / sodium citrate / sodium silicate: The three materials of potassium citrate, sodium citrate, and sodium silicate can synergistically promote the gelling activation rate of steel slag powder for different metal compound compositions on the surface of steel slag powder.

[0049] There is no relevant report in the prior art on jointly activating the activity of steel slag powder / steel slag aggregate with potassium citrate, sodium citrate, and sodium silicate. And experiments show that the activity activation performance of their synergistic effect is better than that of single components; under the same activation effect, the cost of the activator is significantly reduced.

[0050] The present invention also discloses an application method of the above activator. The activator is dissolved in water, and after preparing an activator solution, it is poured into steel slag powder and stirred to prepare an activated steel slag slurry. The activated steel slag slurry is poured into a test mold and vibrated firmly to obtain a specimen.

[0051] The above steel slag powder contains metal compounds such as dicalcium silicate, tricalcium silicate, and dicalcium ferrite.

[0052] Specifically, the application method includes the following steps:

[0053] S1: Take a certain amount of steel slag powder, dry it and weigh it.

[0054] S2: Weigh a certain amount of activator and dissolve it in an appropriate amount of water, and stir evenly to prepare an activator solution.

[0055] S3: First pour the steel slag powder into a mortar mixer, then pour the activator solution into the steel slag powder and stir for a period of time to prepare an activated steel slag slurry.

[0056] In this process, most of tripotassium citrate, trisodium citrate, sodium silicate react with metal compounds such as dicalcium silicate, tricalcium silicate, dicalcium ferrite, etc. to generate compounds such as citrate iron complex, grossular garnet, almandine, and hydrated calcium aluminosilicate (gelling substances), and evenly wrap the steel slag powder;

[0057] S4: Pour the excited steel slag slurry into the test mold and vibrate it, let it stand and then demould it. After demoulding, put the test piece into the curing box for curing.

[0058] In this process, the steel slag powder that has been evenly wrapped by the gelling material adheres to each other through the vibration and static process to form a uniform and relatively stable slurry 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 gelling material.

[0059] Specifically, the certain amount of activator in step S2 is 1-2% of the mass of the steel slag (after drying) in step S1. According to relevant experimental data, adding 1-2% of activator can fully activate the activity of steel slag powder. Adding more activator does not significantly improve the activation effect and increases economic costs.

[0060] Specifically, the appropriate amount of water in step S2 is 15-35% of the mass of the steel slag (after drying) in step S1. According to industry common sense and experimental observations, adding too little water will result in the inability to form a uniform slurry, while adding too much water will cause water separation, both of which are not conducive to the molding of the test piece and will affect the performance of the test piece.

[0061] Specifically, the stirring time in step S3 is ≥100s, so that the activator and the steel slag powder are evenly mixed and fully reacted.

[0062] Specifically, the step S4 is performed by demoulding after the standing time is 24 hours.

[0063] The specific embodiments of the application method correspond to the numbered embodiments 1-1 to 1-4 and the control groups 1-1 to 1-6.

[0064] The present invention also discloses a method for using the above activator to prepare a self-gelling steel slag graded crushed stone, the specific steps of which are as follows:

[0065] S01: batching the aged steel slag aggregate according to the grading requirements, and drying or airing it to make its surface dry;

[0066] S02: dissolving the activator in water and stirring evenly to obtain an activator solution;

[0067] S03: pouring the activator solution into the steel slag aggregate and mixing and stirring to obtain a mixture;

[0068] During this process, most of the 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 form compounds (cementitious substances) such as ferric citrate complex, grossular, almandine, and calcium silicoaluminate hydrate, achieving surface activation of the steel slag aggregate and uniformly coating the surface of the steel slag aggregate;

[0069] S04: Use a vibrating compactor to form specimens. Put the mixture of S03 into the vibrating compactor to form steel slag graded aggregate specimens, and place them in a curing box for curing after standing and demolding.

[0070] During this process, the steel slag aggregates that have been uniformly coated with cementitious substances bond to each other through the processes of vibration compaction and standing to form uniform and relatively stable steel slag graded aggregate specimens. At the same time, the tripotassium citrate, trisodium citrate, and sodium silicate that have not completely reacted and components such as dicalcium silicate, tricalcium silicate, and dicalcium ferrite can still further react to form cementitious substances.

[0071] Specifically, the aged steel slag aggregate is the thermally steamed steel slag aggregate from the steel mill, and after being aged for no less than 6 months, the immersion expansion rate ≤ 2%.

[0072] Specifically, the grading requirements for the aged steel slag aggregate are as follows: 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%. This grading standard strictly limits the distribution ratio of steel slag gravel with different particle sizes, helps to form a framework dense structure, realizes 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 finally formed parts.

[0073] Specifically, the composition of the mixture in S03 is, by weight, 100 parts of graded and aged steel slag aggregate, 0.5 - 2.0 parts of activator, and 1.5 - 3.5 parts of water. While ensuring the activation effect, reduce the addition amount of the activator and the amount of water to ensure that the graded aggregate reaches the maximum density as much as possible while reducing the economic cost.

[0074] Specifically, the stirring time in step S03 ≥ 100 s to ensure the mixing effect.

[0075] Specifically, the specific steps of step S04 are to put the stirred material in step 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 it, 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 crushed stone formed parts.

[0076] The specific embodiments of the application method of the above activator for the activation of steel slag powder are shown in the specific parameters of group 1 - X (X is the number of the embodiment and the control group):

[0077] Example 1 - 1:

[0078] 1000 g of steel slag powder, 2 g of tripotassium citrate, 11.5 g of trisodium citrate, 3 g of sodium silicate, and 190 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The vibration conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. After standing for 24 h, demold it, and then put the specimen into a curing box for curing to obtain Example 1 - 1.

[0079] Example 1 - 2:

[0080] 1000 g of steel slag powder, 5 g of tripotassium citrate, 4 g of trisodium citrate, 2.5 g of sodium silicate, and 160 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The vibration conditions are a vibration frequency of 30 Hz, an exciting force of 6.9 kN, and an amplitude of 1.2 mm. After standing for 24 h, demold it, and then put the specimen into a curing box for curing to obtain Example 1 - 2.

[0081] Example 1 - 3:

[0082] 1000 g of steel slag powder, 2.5 g of tripotassium citrate, 5 g of trisodium citrate, 4 g of sodium silicate, and 150 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The vibration conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. After standing for 24 h, demold it, and then put the specimen into a curing box for curing to obtain Example 1 - 3.

[0083] Example 1 - 4:

[0084] 1000 g of steel slag powder, 2.5 g of tripotassium citrate, 9 g of trisodium citrate, 3 g of sodium silicate, and 210 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The vibration conditions are a vibration frequency of 30 Hz, an exciting force of 6.9 kN, and an amplitude of 1.2 mm. After standing for 24 h, demold it, and then put the specimen into a curing box for curing to obtain the activated steel slag specimen Example 1 - 4.

[0085] Examples 1 - 5:

[0086] 1000 g of steel slag powder, 5.5 g of tripotassium citrate, 13.0 g of trisodium citrate, 4.5 g of sodium silicate, and 180 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Examples 1 - 5.

[0087] Control Group 1 - 1:

[0088] 1000 g of steel slag powder, 160 g of water, without adding an activator. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Control Group 1 - 1.

[0089] Control Group 1 - 2:

[0090] 1000 g of steel slag powder, 10 g of tripotassium citrate, 175 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.9 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Control Group 1 - 2.

[0091] Control Group 1 - 3:

[0092] 1000 g of steel slag powder, 17.5 g of trisodium citrate, 180 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Control Group 1 - 3.

[0093] Control Group 1 - 4:

[0094] 1000 g of steel slag powder, 14 g of sodium silicate, 170 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it to compact. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.9 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Control Group 1 - 4.

[0095] Control Group 1 - 5:

[0096] 1000 g of steel slag powder, 1 g of tripotassium citrate, 2.5 g of trisodium citrate, 1 g of sodium silicate, and 150 g of water. Stir the steel slag powder with water for 100 s. Pour the stirred slurry into a test mold and vibrate it until it is compacted. The compaction conditions are a vibration frequency of 30 Hz, an exciting force of 6.8 kN, and an amplitude of 1.2 mm. Demold after standing for 24 h, and then place the specimen in a curing box for curing to obtain Control Groups 1-5.

[0097] For the above-mentioned examples and control groups, referring to the "Test Method for Strength of Cement Mortar (ISO Method)" (GBT 17671-1999), prismatic specimens with dimensions of 40 mm×40 mm×160 mm were molded, and flexural strength and compressive strength tests were carried out; meanwhile, core samples were taken to observe the microscopic morphology of the specimens and test their phase compositions. The following test data were obtained:

[0098] Mechanical strength test results of the control groups and examples

[0099]

[0100] It can be seen from the above test results that the use of an activator compounded with tripotassium citrate, trisodium citrate, and sodium silicate can significantly stimulate the hydration rate of steel slag powder (as Figure 10 shown), and greatly improve the mechanical strength of the hardened steel slag powder paste specimens. Compared with Control Group 1 (blank sample), the 28-day compressive strength and flexural strength of the specimens increased by more than 300%. Without binders such as cement, the hardening and setting of the steel slag powder paste can be achieved, and the strength can reach the strength of P.O 42.5 grade cement mortar (28-day compressive strength ≥ 42.5 MPa).

[0101] Comparing Control Groups 1-2, 1-3, 1-4 with Examples 1-1 to 1-5, when the dosages of tripotassium citrate, trisodium citrate, and sodium silicate are outside the recommended range of the present invention, the 28-day compressive strength of the steel slag powder paste specimens cannot reach the strength of P.O 42.5 cement.

[0102] It can be seen from the examples that the mechanical strength of the steel slag powder paste specimens prepared by the method disclosed in the present invention is excellent. The flexural strength can reach 2.15 MPa - 2.65 MPa (3 days), 3.94 MPa - 4.95 MPa (7 days), 5.83 MPa - 6.94 MPa (28 days); the compressive strength can reach 8.78 MPa - 10.47 MPa (3 days), 25.42 MPa - 30.84 MPa (7 days), 43.96 MPa - 50.13 MPa (28 days).

[0103] The above activator compounded with tripotassium citrate, trisodium citrate, and sodium silicate can significantly stimulate the gelling activity of steel slag powder and promote the hydration rate (as Figure 10As shown in the figure, it significantly improves the mechanical strength of the steel slag slurry, has a simple preparation process, can be widely applied to scenarios such as low-carbon cementitious materials and concrete, and at the same time realizes the consumption of steel slag solid waste.

[0104] The specific implementation example parameters of the application method of using the above activator to prepare a self-cementitious graded steel slag gravel are as shown in Group 2-X (X is the number of the example and the control group):

[0105] Example 2-1:

[0106] 1000 g of steel slag aggregate, 15 g of activator, and 31 g of water. The activator composition 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 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.

[0107] Dissolve the 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 graded steel slag gravel of Example 2-1.

[0108] Example 2-2:

[0109] 1000 g of steel slag aggregate, 5 g of activator, and 28 g of water. The activator composition by mass is 2.5 g of tripotassium citrate, 1.5 g of trisodium citrate, and 1 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.

[0110] Dissolve the 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 graded steel slag gravel of Example 2-2.

[0111] Example 2-3:

[0112] 1000 g of steel slag aggregate, 10 g of activator, and 27 g of water. The composition of the activator by mass is 5 g of tripotassium citrate, 3.3 g of trisodium citrate, and 1.7 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.

[0113] Dissolve the 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, excitation force 6.8 kN, and amplitude 1.2 mm to obtain Activated Steel Slag Graded Aggregate Example 2 - 3.

[0114] Example 2 - 4:

[0115] 1000 g of steel slag aggregate, 10 g of activator, and 26 g of water. The composition of the activator by mass is 5.5 g of tripotassium citrate, 3.5 g 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.

[0116] Dissolve the 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, excitation force 6.8 kN, and amplitude 1.2 mm to obtain Activated Steel Slag Graded Aggregate Example 2 - 4.

[0117] Example 2 - 5:

[0118] 1000 g of steel slag aggregate, 12 g of activator, and 28 g of water. The composition of the activator 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.

[0119] Dissolve the 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, excitation force 6.9 kN, and amplitude 1.2 mm to obtain Activated Steel Slag Graded Aggregate Example 2 - 5.

[0120] Example 2 - 6:

[0121] 1000 g of steel slag aggregate, 25 g of activator, and 28 g of water. The 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.

[0122] Dissolve the 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 Activated Steel Slag Gradation Crushed Stone Example 2 - 6.

[0123] Control Group 2 - 1:

[0124] 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 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.

[0125] 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 2 - 1.

[0126] Control Group 2 - 2:

[0127] 1000 g of steel slag aggregate, 15 g of activator, and 2.8 g of water. The activator includes 2.2 g of tripotassium citrate, 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 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.

[0128] Dissolve the in - situ 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 Activated Steel Slag Gradation Crushed Stone Control Group 2 - 2.

[0129] For the said embodiments and the control group, vibration compaction was used to form specimens, and then CBR tests and immersion expansion rates were conducted to test the deformation resistance and stability of the graded steel slag mixture, and to compare the influence of in-situ surface cementitious of steel slag aggregates on the mechanical strength and stability of steel slag aggregates; meanwhile, scanning electron microscopy was used to observe the micro-morphology of the in-situ surface excitation products of steel slag aggregates (such as Figures 7 - 9 ). Through testing, the following test data were obtained:

[0130] The CBR value (i.e., California Bearing Ratio) is an index for evaluating the bearing capacity of subgrades and pavement materials. It is defined by the ability of the material to resist the indentation deformation of local loads, and the bearing capacity of standard crushed stones is used as the standard, and the CBR value is expressed as a percentage of the relative value. The higher the CBR value, the stronger the bearing capacity and deformation resistance.

[0131] Table 2-1 CBR test results of the control group and the embodiments

[0132]

[0133] 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 days. The specific data are shown in Table 2-2:

[0134] Table 2-2 Immersion expansion test results of the control group and the embodiments

[0135]

[0136]

[0137] It can be seen from the above test results that the activator composed of potassium citrate, sodium citrate and sodium silicate can effectively activate the active substances on the in-situ surface of steel slag aggregates, 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 deformation resistance (the CBR value is significantly improved). The CBR value can reach 324%-355% (7 days), 357%-378% (14 days), 368%-396% (28 days), 374%-411% (90 days).

[0138] At the same time, the generated cementitious products wrap the surface of the steel slag aggregates, thereby reducing the immersion expansion rate of the steel slag mixture and improving the stability of the steel slag aggregates. According to the experimental data, the immersion expansion rate (10 days) of the embodiments is reduced to 1.24%-1.34%, which is significantly lower than that of the comparative examples.

[0139] Comparing the control group 2-2 and the embodiments, when the content of sodium citrate in the 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.

[0140] Comparing Comparative Example 2-(1-5) with Example 2-6, when the content of tripotassium citrate in the activator is too high, the mechanical properties of the formed parts do not increase significantly, the immersion expansion rate is comparable to that of the example, and even increases, and the economic cost increases significantly. Therefore, too high a content of potassium citrate is not an optimal range for using this activator to prepare self-cementitious steel slag graded aggregate.

[0141] The above-mentioned steel slag graded aggregate can be formed without adding additional binders, has excellent mechanical strength, anti-deformation ability and low immersion expansion rate, can be widely used in fields such as road paving and concrete preparation, and at the same time realizes the disposal of steel slag solid waste.

[0142] The above is only a 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 by the protection scope of the present invention.

Claims

1. An activator, characterized in that: The activator is used for gelling and activating steel slag powder, and its specific composition is as follows by mass: 12.00%-22.00% of tripotassium citrate, 34.00%-63.00% of trisodium citrate, and 20.00%-35.00% of sodium silicate, which is 100% in total.

2. The activator according to claim 1, wherein: The steel slag powder contains one or more of dicalcium silicate, tricalcium silicate, tetracalcium aluminoferrite and dicalcium ferrite.

3. The activator according to claim 1, characterized in that: The tripotassium citrate, trisodium citrate and sodium silicate are all of analytical grade or above.

4. A method for applying the activator according to any one of claims 1-3, characterized in that: The activator is dissolved in water to obtain an activator solution, which is then poured into steel slag powder and stirred to obtain an activated steel slag slurry. The activated steel slag slurry is poured into a test mold and compacted to obtain a test piece.

5. The application method according to claim 4, wherein: The application method comprises: S1: Take a certain amount of steel slag powder, dry it and weigh it; S2: Weigh a certain amount of activator and dissolve it in an appropriate amount of water, and stir evenly to prepare an activator solution; S3: first pour the steel slag powder into a mortar mixer, then pour the activator solution into the steel slag powder and stir to obtain activated steel slag slurry; S4: Pour the excited steel slag slurry into the test mold and vibrate it, let it stand and then demould it. After demoulding, put the test piece into the curing box for curing.

6. The application method according to claim 5, characterized in that: In step S2, the activator is 1%-2% of the mass of the steel slag powder after drying in step S1, in terms of mass percentage.

7. The application method according to claim 5, characterized in that: In step S2, the appropriate amount of water is 15%-35% of the mass of the steel slag after drying in step S1, calculated by mass percentage.

8. A method for applying the activator according to any one of claims 1-3, characterized in that: The activator is used to prepare a self-gelling steel slag graded crushed stone, and the specific steps are as follows: S01: batching and drying the aged steel slag aggregate according to the grading requirements; S02: dissolving the activator in water and stirring the mixture to obtain an activator solution; S03: pouring the activator solution into the steel slag aggregate and mixing and stirring to obtain a mixture; S04: Use a vibration compactor to form a test piece. Put the mixture of S03 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.

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