An activator for reducing the water expansion rate of steel slag and its preparation and use method

Abstract

The invention relates to the technical field of steel slag pretreatment, and in particular to an activator for reducing the water expansion rate of steel slag and a preparation and use method thereof. The activator is obtained by mixing a plant urease solution and a urea solution. By controlling the concentrations of the plant urease solution and the urea solution and the added volume ratio, the prepared activator can show a good effect of reducing the water expansion rate of the steel slag, and can make the water expansion rate of the steel slag reach below 1.2%, and the volume expansion rate of the steel slag-asphalt mixture reach below 0.8%. When in use, the steel slag and the activator can be directly immersed and activated, the activation time is short, no large floor space is required, the cost is low, and it is easy to promote and apply.

Description

Technical Field

[0001] The invention relates to the technical field of steel slag pretreatment, and in particular to an activator for reducing the water expansion rate of steel slag and a preparation and use method thereof. Background Art

[0002] Steel slag is an alkaline aggregate with a large number of pores on its surface, so it has very good adhesion to asphalt and can be used to prepare steel slag asphalt concrete with good properties such as high splitting strength ratio, high residual stability and anti-rutting.

[0003] There is a problem in the application of steel slag in the road field. Steel slag contains a large amount of free calcium oxide and magnesium oxide, which are prone to hydration reaction, resulting in volume expansion, accelerating the cracking of asphalt mixture pavement. The traditional method of pre-treating steel slag to reduce the water expansion rate is to age it in the natural environment, which occupies a large area and takes a long time. Summary of the invention

[0004] The purpose of the present invention is to provide an activator for reducing the water expansion rate of steel slag and a method for using the activator, in view of the problems that the existing pretreatment method for reducing the water expansion rate of steel slag has a large footprint and a long pretreatment time. The activator is obtained by mixing a plant urease solution and a urea solution. By controlling the concentrations of the plant urease solution and the urea solution and the added volume ratio, the prepared activator can show a good effect of reducing the water expansion rate of the steel slag. When in use, the steel slag and the activator can be directly immersed and activated. The activation time is short, no large floor space is required, the cost is low, and unexpected effects are shown.

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

[0006] An activator for reducing the water expansion rate of steel slag is obtained by mixing a plant urease solution and a urea solution; the volume ratio of the plant urease solution to the urea solution is 1:0.75-1.25;

[0007] The plant urease solution is a supernatant obtained by filtering and centrifuging a mixed suspension of plant seed powder and water, the mass ratio of the plant seed powder to water is 1:10-100; the concentration of the urea solution is 0.8-1.5 mol / L.

[0008] The invention provides an activator for reducing the water expansion rate of steel slag. The activator is obtained by mixing a plant urease solution and a urea solution. By controlling the concentrations of the plant urease solution and the urea solution and the added volume ratio, the prepared activator can show a good effect of reducing the water expansion rate of steel slag, and can make the water expansion rate of steel slag reach below 1.2%, and the volume expansion rate of steel slag-asphalt mixture reach below 0.8%, achieving unexpected results.

[0009] Furthermore, the volume ratio of the plant urease solution to the urea solution is 1:0.75-1.

[0010] Furthermore, the plant urease solution is the centrifuged supernatant of a mixed suspension of plant seed powder and water, and the mass ratio of the plant seed powder to water is 1:20-100.

[0011] Further, the concentration of the urea solution is 1 to 1.2 mol / L. In some embodiments, the concentration of the urea solution can be adjusted within the range of 1 to 1.2 mol / L.

[0012] Furthermore, the plant urease solution is the centrifuged supernatant of a mixed suspension of plant seed powder and water; the plant seed powder is at least one of soybean seed powder, corn seed powder, and wheat seed powder. Preferably, the plant seed powder is soybean seed powder.

[0013] Furthermore, the plant seed powder is prepared by the following method: using plant seeds as raw materials, drying and crushing to obtain the plant seed powder.

[0014] Furthermore, the pulverizing process is to grind the plant seeds into 80-120 meshes using a ball mill.

[0015] Furthermore, the plant urease solution is prepared by the following method:

[0016] First, plant seed powder is mixed with water and stirred magnetically;

[0017] Then, the obtained suspension is filtered and centrifuged, and the supernatant is taken to obtain the plant urease solution.

[0018] Furthermore, the activator is obtained by mixing the plant urease solution with the urea solution using a pipette.

[0019] Another object of the present invention is to provide a method for preparing the activator.

[0020] The method comprises the following steps: mixing a plant urease solution with a urea solution, and stirring the mixture evenly to obtain an activator.

[0021] Another object of the present invention is to provide a method for using the activator.

[0022] The method for using the activator for reducing the water expansion rate of steel slag as mentioned above comprises the following steps:

[0023] Step 1, mixing steel slag with an activator and soaking them;

[0024] Step 2: Filter out the steel slag and air-dry it at room temperature.

[0025] The method for using the activator provided in the present application is to directly soak the steel slag and the activator for activation. The activation time is short, no large floor space is required, the cost is low, and it is easy to promote and apply.

[0026] Furthermore, in step 1, the soaking time is at least 24 hours. If the soaking time is too short, the water expansion rate of the steel slag will decrease too little, and the ideal effect cannot be achieved. Preferably, in step 1, the soaking time is 24 hours to 72 hours.

[0027] Furthermore, in step 1, the added mass of the steel slag is greater than or equal to the added mass of the activator, and a reasonable ratio can enable the steel slag to be better activated. Preferably, the mass ratio of the steel slag to the activator is 3 to 1:1.

[0028] Furthermore, the particle size of the steel slag is 4.75 to 13.2 mm.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. The present invention provides an activator for reducing the water expansion rate of steel slag. The activator is obtained by mixing a plant urease solution and a urea solution. By controlling the concentrations of the plant urease solution and the urea solution and the added volume ratio, the prepared activator can show a good effect of reducing the water expansion rate of steel slag, and can make the water expansion rate of steel slag reach below 1.2%, and the volume expansion rate of steel slag-asphalt mixture reach below 0.8%, achieving unexpected results.

[0031] 2. The method for using the activator provided in the present application is to directly soak the steel slag and the activator for activation. The activation time is short, no large floor space is required, the cost is low, and it is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a data graph of the water expansion rate of the pretreated steel slag in a specific implementation manner. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used to limit the present invention.

[0035] In the following embodiments and comparative examples, the steel slag used is from Xiangtan, Hunan, and is a converter steel slag; part of the steel slag is aged for 12 months for comparative analysis.

[0036] In the following examples and comparative examples, the base asphalt used to prepare the steel slag asphalt mixture is No. 70 road petroleum asphalt, and the aggregate is limestone crushed stone, and its gradation meets the gradation requirements in Table 1. The mineral powder used is limestone powder.

[0037] Table 1 Grading of steel slag-asphalt mixture

[0038]

[0039] Example 1

[0040] Preparation of activating agent

[0041] The plant seeds are soybean seeds; dried in an oven at 40°C for 6 hours; then crushed in a ball mill and passed through a 100-mesh sieve; the sieved soybean seed powder and deionized water were mixed at a solid-liquid ratio of 1:10 to prepare a solution with a concentration of 100 g / L, and stirred with a magnetic stirrer for 30 minutes and then allowed to stand for 24 hours, the upper suspension was filtered through gauze, and centrifuged at 3000 r / min and 4°C for 15 minutes, and the supernatant obtained was the soybean urease solution (EICP solution);

[0042] Use a pipette to mix the urease solution and 1.1 mol / L urea at a volume ratio of 1:0.75, stir evenly to obtain an activator, and incubate at room temperature for 2 h for later use;

[0043] Slag pretreatment process

[0044] The steel slag with a particle size of 4.75 to 13.2 mm after screening is immersed in an activator, the mass ratio of the steel slag to the activator is 1:1, and the immersion time is 24 hours; after the immersion is completed, the treated steel slag is air-dried at room temperature to obtain.

[0045] Preparation process of steel slag-asphalt mixture

[0046] According to the designed mix ratio, limestone crushed stones and treated steel slag of various particle sizes are screened out and preheated in an oven at 180°C for 4 hours; before mixing, 50% of the limestone with a particle size of 4.75-13.2 mm is replaced with treated steel slag according to the principle of equal volume replacement; the replaced aggregates are mixed with asphalt in a mixer at 180°C; and the steel slag-asphalt mixture is obtained by compaction.

[0047] Example 2

[0048] Preparation of activating agent

[0049] The plant seeds are soybean seeds; dried in an oven at 40°C for 6 hours; then crushed in a ball mill and passed through a 100-mesh sieve; the sieved soybean seed powder and deionized water were mixed at a solid-liquid ratio of 1:50 to prepare a solution with a concentration of 20 g / L, and stirred with a magnetic stirrer for 30 minutes and then allowed to stand for 24 hours, the upper suspension was filtered through gauze, and centrifuged at 3000 r / min and 4°C for 15 minutes, and the supernatant obtained was the soybean urease solution (EICP solution);

[0050] Use a pipette to mix the urease solution and 1.2 mol / L urea in a volume ratio of 1:1, stir evenly to obtain an activator, and incubate at room temperature for 2 h for later use;

[0051] Slag pretreatment process

[0052] The steel slag with a particle size of 4.75 to 13.2 mm after screening is immersed in an activator, the mass ratio of the steel slag to the activator is 2:1, and the immersion time is 24 hours; after the immersion is completed, the treated steel slag is air-dried at room temperature to obtain.

[0053] Preparation process of steel slag-asphalt mixture

[0054] According to the designed mix ratio, limestone crushed stones and treated steel slag of various particle sizes are screened out and preheated in an oven at 180°C for 4 hours; before mixing, 50% of the limestone with a particle size of 4.75-13.2 mm is replaced with treated steel slag according to the principle of equal volume replacement; the replaced aggregates are mixed with asphalt in a mixer at 180°C; and the steel slag-asphalt mixture is obtained by compaction.

[0055] Example 3

[0056] Preparation of activating agent

[0057] The plant seeds are soybean seeds; dried in an oven at 40°C for 6 hours; then crushed in a ball mill and passed through a 100-mesh sieve; the sieved soybean seed powder and deionized water were mixed at a solid-liquid ratio of 1:100 to prepare a solution with a concentration of 10 g / L, and stirred with a magnetic stirrer for 30 minutes and then allowed to stand for 24 hours, the upper suspension was filtered through gauze, and centrifuged at 3000 r / min and 4°C for 15 minutes, and the supernatant obtained was the soybean urease solution (EICP solution);

[0058] Use a pipette to mix the urease solution and 1 mol / L urea at a volume ratio of 1:1.25, stir evenly to obtain an activator, and incubate at room temperature for 2 h for later use;

[0059] Slag pretreatment process

[0060] The steel slag with a particle size of 4.75 to 13.2 mm after screening is immersed in an activator, the mass ratio of the steel slag to the activator is 3:1, and the immersion time is 24 hours; after the immersion is completed, the treated steel slag is air-dried at room temperature to obtain.

[0061] Preparation process of steel slag-asphalt mixture

[0062] According to the designed mix ratio, limestone crushed stones and treated steel slag of various particle sizes are screened out and preheated in an oven at 180°C for 4 hours; before mixing, 50% of the limestone with a particle size of 4.75-13.2 mm is replaced with treated steel slag according to the principle of equal volume replacement; the replaced aggregates are mixed with asphalt in a mixer at 180°C; and the steel slag-asphalt mixture is obtained by compaction.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 1 is that the steel slag obtained after screening is immersed in the EICP solution for 48 hours; the steel slag treated in this embodiment is used to prepare the steel slag-asphalt mixture.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1; the steel slag obtained after screening is immersed in the EICP solution for 48 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0067] Example 6

[0068] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:100 to obtain a solution with a concentration of 10 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1.25; the steel slag obtained after screening is immersed in the EICP solution for 48 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that the steel slag obtained after screening is immersed in the EICP solution for 72 hours; the steel slag treated in this embodiment is used to prepare the steel slag-asphalt mixture.

[0071] Example 8

[0072] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0073] Example 9

[0074] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:100 to obtain a solution with a concentration of 10 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1.25; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0075] Example 10

[0076] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:0.75; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0077] Embodiment 11

[0078] The difference between this embodiment and embodiment 1 lies in that, in the preparation process of plant urease, the sieved soybean powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1.25; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0079] Example 12

[0080] The difference between this embodiment and embodiment 1 is that the plant seeds used in the preparation process of plant urease are corn seeds, and the sieved corn seed powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0081] Example 13

[0082] The difference between this embodiment and Embodiment 1 is that the plant seeds used in the preparation process of plant urease are wheat seeds, and the sieved corn seed powder and deionized water are prepared at a solid-liquid ratio of 1:50 to obtain a solution with a concentration of 20 g / L; when obtaining the EICP solution, a pipette is used to mix the urease solution prepared in this embodiment with 1.1 mol / L urea at a volume ratio of 1:1; the steel slag obtained after screening is immersed in the EICP solution for 72 hours; and the steel slag treated in this embodiment is used to prepare steel slag-asphalt mixture.

[0083] Comparative Example 1

[0084] The difference between the comparative example and Example 1 is that plant urease is not prepared; in order to strictly control the variables and ensure the rigor of the present invention, the steel slag is still treated according to the pretreatment steps in Example 1, except that the steel slag after particle size screening is immersed in a 1.1 mol / L urea solution according to a mass volume ratio, the mass volume ratio of steel slag to urea solution is 1:1, and the immersion time is 72h; after the immersion is completed, the treated steel slag is air-dried at room temperature; the steel slag treated in this comparative example is used to prepare steel slag-asphalt mixture.

[0085] Comparative Example 2

[0086] Comparative Example 2 is different from Example 1 in that there is no process of preparing plant urease and obtaining EICP solution. Steel slag that has been naturally aged for 12 months is used, and after cleaning and removing dust and impurities on the surface, a steel slag-asphalt mixture is prepared according to the method of preparing a mixture in Example 1.

[0087] Comparative Example 3

[0088] Comparative Example 3 is different from Example 1 in that there is no process of preparing plant urease and obtaining EICP solution. Unlike Comparative Example 2, steel slag without aging treatment is used, and after cleaning and removing dust and impurities on the surface, the steel slag-asphalt mixture is prepared according to the method of preparing the mixture in Example 1.

[0089] Comparative Example 4

[0090] The difference between Comparative Example 4 and Example 1 is that the urease solution and the urea solution are mixed in a volume ratio of 1:0.1, and the other conditions are the same as those in Example 1.

[0091] Comparative Example 5

[0092] The difference between Comparative Example 5 and Example 1 is that when preparing the activator, the sieved soybean seed powder and deionized water are prepared into a solution at a solid-liquid ratio of 1:1000, and the concentration is 1 g / L. Other conditions are the same as those in Example 1.

[0093] test

[0094] (I) Water expansion test

[0095] The steel slag obtained in Examples 1-13 and Comparative Examples 1-5 was tested for water expansion rate according to the "Steel Slag Stability Test Method" (GB / T 24175-2009). The specific test method is to put the steel slag into a cylindrical test mold, compact it, and then put it into a constant temperature water bath for water bath heating at 90°C for 6 hours. After heating, it is cooled naturally, and the expansion data is recorded according to the dial indicator for ten days. The test results are shown in Table 2.

[0096] Volume stability test

[0097] The steel slag-asphalt concrete obtained in Examples 1-13 and Comparative Examples 1-5 was subjected to a volume stability test on the prepared standard Marshall specimens according to the specification of "JTG E42-2005 Highway Engineering Aggregate Test Procedure". The specimens were immersed in a constant temperature water tank at 60°C for 72 hours, and the volume expansion rate was calculated by obtaining the volume of the specimens after immersion. The experimental results are shown in Table 2.

[0098] Table 2 Slag water expansion rate and slag-asphalt mixture volume expansion rate

[0099]

[0100]

[0101] The specification requires that the expansion rate of steel slag upon immersion in water is less than 2%, and the volume expansion rate of the mixture is less than 1.5%. From the data in Table 2, it can be seen that the volume expansion rate of the prepared steel slag-asphalt mixture has a large correlation with the expansion rate of steel slag upon immersion in water.

[0102] Comparing Examples 1-9 in Table 2, it can be found that the concentration of soybean urease and the treatment time of steel slag in the EICP solution are important factors affecting the slag immersion expansion rate. And the higher the soybean urease concentration, the higher the volume ratio of soybean urease to urea solution, and the longer the treatment time, the faster the immersion expansion rate decreases. From Examples 1-9, it can be found that when the urease concentration increases from 20g / L to 100g / L, the concentration increases significantly, while the slag immersion expansion rate decreases insignificantly, which is related to the activity of plant urease extraction. From Examples 8, 10, and 11, it can be found that the volume ratio when soybean urease is mixed with urea solution is also a factor affecting the slag treatment effect. When the volume ratio increases from 1:0.75 to 1:1, the slag immersion expansion rate decreases significantly, and continues to increase to 1:1.25 without obvious effect. Therefore, from the perspective of economic benefits, the optimal concentration for preparing urease solution is 20g / L, and the optimal mixing volume ratio of urease solution to urea solution is 1:1.

[0103] From Examples 12 and 13, it can be found that the plant urease extracted from corn seeds and wheat seeds is not as effective as soybean seeds in treating steel slag. However, the water swelling rate of the treated steel slag is about 1.52%, which is lower than the 2% required by the specification, and can also replace aggregates to prepare steel slag-asphalt mixture. From Comparative Example 1, it can be found that the steel slag treated with urea solution without preparing plant urease cannot significantly reduce the water swelling rate of the steel slag.

[0104] By comparing the examples and comparative examples in Table 2, it can be found that the water swelling rate of the steel slag pretreated for 72 hours using the method of the present invention is basically the same as or even lower than that of the steel slag aged for one year. This shows that after the steel slag is treated with the EICP solution obtained by plant urease, the free calcium oxide and magnesium oxide contained in the steel slag are consumed by the reaction, and the volume stability of the prepared steel slag-asphalt mixture meets the requirements.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An activator for reducing the water expansion rate of steel slag, characterized in that: The method comprises mixing a plant urease solution and a urea solution; the volume ratio of the plant urease solution to the urea solution is 1:0.75-1.25; The plant urease solution is a supernatant obtained by filtering and centrifuging a mixed suspension of plant seed powder and water, and the mass ratio of the plant seed powder to water is 1:10-100; The concentration of urea solution is 0.8~1.5 mol / L.

2. The activator for reducing the water expansion rate of steel slag according to claim 1, characterized in that: The volume ratio of the plant urease solution to the urea solution is 1:0.75-1.

3. The activator for reducing the water expansion rate of steel slag according to claim 1, characterized in that: The plant urease solution is the centrifuged supernatant of a mixed suspension of plant seed powder and water, and the mass ratio of the plant seed powder to water is 1:20-100.

4. The activator for reducing the water expansion rate of steel slag according to claim 1, characterized in that: The concentration of the urea solution is 1 to 1.2 mol / L.

5. The activator for reducing the water expansion rate of steel slag according to claim 1, characterized in that: The plant urease solution is the centrifuged supernatant of a mixed suspension of plant seed powder and water; the plant seed powder is at least one of soybean seed powder, corn seed powder and wheat seed powder.

6. The activator for reducing the water expansion rate of steel slag according to claim 5, characterized in that: The plant seed powder is soybean seed powder.

7. The method for preparing an activator for reducing the water expansion rate of steel slag according to any one of claims 1 to 6, characterized in that: The following steps are involved: The plant urease solution and the urea solution are mixed and stirred evenly to obtain an activator.

8. The method for using the activator for reducing the water expansion rate of steel slag according to any one of claims 1 to 6, characterized in that: The following steps are included: Step 1, mixing steel slag with an activator and soaking them; Step 2: Filter out the steel slag and air-dry it at room temperature.

9. The method of use according to claim 8, characterized in that: In step 1, the soaking time is at least 24 hours.

10. The method of use according to claim 8, characterized in that: In the step 1, the added mass of the slag is greater than or equal to the added mass of the activator.

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