A steel slag processing method and its application in cement-based materials

Abstract

The present invention discloses a steel slag processing method and its application in cement-based materials. The steel slag processing method comprises the following steps: mixing steel slag scraps with a weak acid solution to obtain a slurry, pouring the slurry into a mold for compression molding, demoulding after molding, and curing the slag in an environment with a temperature of 25°C ± 2°C and a humidity of 60% to 80% for 1d-3d, and then crushing the slag into the desired particle size with a crusher to complete the processing. The steel slag obtained by the method is used as a steel slag aggregate in cement-based materials, and has qualified stability, high strength and low water absorption. The present invention utilizes the promoting effect of weak acid on the hydration of steel slag, and through a compression molding process and subsequent crushing, the steel slag scraps are re-cemented to obtain a steel slag aggregate with high strength, low water absorption and qualified volume stability. The steel slag aggregate is used in cement-based materials to improve the strength, wear resistance and radiation protection of cement-based materials.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and particularly relates to a steel slag processing method and application thereof in cement-based materials. Background Art

[0002] In recent years, with the continuous growth of my country's steel production capacity, the amount of steel slag generated during steel production has also increased. If steel slag is not effectively utilized as a resource, hundreds of millions of tons of steel slag will occupy arable land, pollute water sources, damage the ecology, and pose safety risks to people's production and daily life. Using steel slag as a building material is one of the most effective solutions. Not only is the demand high, allowing for rapid consumption of large quantities of steel slag, but it also helps reduce the adverse effects of mineral mining and cement production, offering both economic and ecological benefits.

[0003] The main components of steel slag are C3S, C2S, C2F and RO phase (solid solution of metal oxides such as MgO, FeO and MnO). Its composition is similar to that of cement and can be used as a mineral admixture. However, the composition of steel slag fluctuates greatly, its hydration activity is low, and its volume stability is poor, so its utilization rate in cement-based materials is low. Steel slag can also be used as aggregate, but there are still certain problems. On the one hand, the stability of massive steel slag is worse and its water absorption rate is higher. Direct use will affect the performance of cement-based materials. On the other hand, in the process of preparing aggregate, it must go through steps such as pretreatment and mechanical crushing. In this process, steel slag debris is inevitably produced. If mixed into cement-based materials, it will cause problems such as decreased fluidity, long setting time, and low early strength. Summary of the Invention

[0004] To address the above issues, the present invention discloses a method for processing steel slag and its application in cement-based materials. The resulting steel slag, when used as aggregate in cement-based materials, exhibits satisfactory stability, high strength, and low water absorption. This method utilizes the effect of weak acids on the hydration of steel slag. Through a compression molding process and subsequent crushing, the steel slag debris is re-cemented to produce a steel slag aggregate with high strength, low water absorption, and satisfactory volume stability. Using steel slag aggregate in cement-based materials can improve the strength, wear resistance, and radiation protection of cement-based materials.

[0005] The technical solution adopted by the present invention comprises the following steps:

[0006] 1) uniformly mixing steel slag chips with a weak acid solution to obtain a slurry;

[0007] 2) The slurry is poured into a mold and pressed into shape, and then demolded after forming; the molding pressure is 4-12 MPa, and the holding time is not less than 1 minute;

[0008] 3) Place in an environment with a temperature of 25℃±2℃ and a humidity of 60% to 80% for 1 to 3 days;

[0009] 4) The processing is completed after crushing with a crusher.

[0010] Preferably, in step 1), the mass ratio of the weak acid solution to the steel slag is 0.1 to 0.15.

[0011] Preferably, the particle size of the steel slag in step 1) is less than 0.178 mm.

[0012] Preferably, the weak acid is acetic acid solution with a concentration range of 1 mol / L to 6 mol / L;

[0013] As a preferred step 4), the retained particle sizes after crushing are 4.75-9.50 mm and 9.50-19.50 mm.

[0014] The steel slag treated by the steel slag treatment method can be used in cement-based materials as steel slag aggregate.

[0015] In the method of the present invention, the addition of acetic acid promotes the dissolution of calcium-containing minerals in steel slag, and the amount of calcium ions leached in the solution is significantly increased. The higher the acetic acid concentration, the higher the amount of calcium ions leached. The addition of acetic acid reduces the amount of f-CaO and f-MgO in the steel slag, ensuring volume stability. The acetic acid significantly promotes the hydration of the steel slag. Compared with the control group, the acetic acid has a dissolving effect on C3S, C2S, C2F, C3A, RO, etc., and increases amorphous substances (such as silica gel, C-(A)-SH gel, etc.).

[0016] Beneficial effects: Compared with the existing technology, this method has the following advantages:

[0017] 1. Higher utilization rate of steel slag. Under the stimulation of acetic acid, the content of f-CaO in steel slag is reduced to 0.16%, and f-MgO is reduced to 0.63%. The stability meets the use requirements.

[0018] 2. The process is simple and does not generate waste. As time goes by, the hydration of the aggregate will continue, which can reduce the unilateral growth effect and improve the performance of the interface transition zone.

[0019] 3. The steel slag aggregate obtained by the present invention is similar to natural basalt aggregate and lower than the original steel slag aggregate, so its mechanical properties are better than the original steel slag aggregate; the water absorption rate is 3.8%, which is higher than that of natural basalt aggregate, but the water absorption rate is lower than that of the original steel slag aggregate.

[0020] The present invention provides a method for treating steel slag with a weak acid, thereby improving the resource utilization rate of steel slag. The weak acid is used to dissolve f-CaO and f-MgO in the steel slag and stimulate the hydration activity of the steel slag, thereby improving the mechanical properties and stability of the steel slag aggregate. The resulting steel slag aggregate has high strength, low water absorption, and qualified volume stability. This method has the advantages of a simple process and no waste generation, effectively solving the problems of poor volume stability and low hydration activity of the steel slag, and improving the resource utilization rate of the steel slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the prepared steel slag aggregate.

[0022] Figure 2 This is the effect of acetic acid concentration on Ca leaching in steel slag in Example 2.

[0023] Figure 3 This is the effect of acetic acid concentration on the strength of steel slag aggregate parent rock in Example 2.

[0024] Figure 4 3 is a QXRD diagram comparing the aggregate mineral compositions in Example 3 and Comparative Example 3.

[0025] Figure 5 is the FT-IR graph of the aggregate in Example 3 and Comparative Example 3.

[0026] Figure 6 This is the microscopic morphology of the aggregate in Comparative Example 3.

[0027] Figure 7 This is the microscopic morphology of aggregate 28d in Example 3.

[0028] Figure 8 This is the result of the stability characterization of the cement test block prepared using the aggregate in Example 3. DETAILED DESCRIPTION

[0029] The following examples are carried out with reference to the following steps:

[0030] 1. Use glacial acetic acid and deionized water to prepare acetic acid solutions of different concentrations.

[0031] 2. Add steel slag into a mixing pot, pour in acetic acid solution, stir evenly, put into a mold, and press into shape.

[0032] 3. De-mould immediately after forming and place in an environment with a temperature of 25℃±2℃ and a humidity of 60% to 80% for 1-3 days.

[0033] 4. Crush and screen the test blocks to obtain steel slag aggregate.

[0034] Unlike aggregates whose mechanical properties are determined by their crushing values, the present invention uses steel slag scraps to prepare aggregate. Before crushing and screening, the resulting slag specimens are structurally regular and complete, serving as the parent rock for the slag aggregate, and their compressive strength can be directly measured. The compressive strength of the parent rock can be used to determine the dynamics of the slag aggregate's strength development after acetic acid treatment.

[0035] Aggregate properties were tested and analyzed, revealing that acetic acid concentration has a positive effect on Ca leaching; the higher the acetic acid concentration, the greater the amount of Ca leached; acetic acid can promote hydration of steel slag, providing it with higher early strength; when the acetic acid concentration is higher than 2 mol / L, the 1-day strength of the parent rock exceeds 10 MPa, with the highest strength at 3d, 7d, and 28d after treatment with 3 mol / L acetic acid.

[0036] The appendix in the manual Figure 1 The prepared steel slag aggregates are of different particle sizes; Figure 2 and Figure 3 The effect of acetic acid concentration on the leaching of Ca from steel slag and the change in aggregate parent rock strength in Example 2; Figure 4-Figure 7 is a comparison of the aggregate mineral composition in Example 3 and Comparative Example 3; Figure 8 The stability of cement blocks made from the steel slag aggregate obtained in Example 3 was tested using a cooking method. Acetic acid stimulates the hydration activity of steel slag, promoting the dissolution of minerals such as f-CaO, f-MgO, C3S, C2S, C2F, C3A, and RO phases, increasing the amount of calcium released and generating larger silica gel and CSH, thereby improving the mechanical properties and stability of the steel slag aggregate.

[0037] Example 1

[0038] Step 1: Take 100 parts by mass of steel slag powder and 12 parts by mass of 1 mol / L acetic acid solution, mix them evenly, press them at molding pressures of 4 MPa, 8 MPa, and 12 MPa for 2 minutes, demold them, and obtain the mother rock of steel slag aggregate.

[0039] Step 2: After curing for 3 days in an environment with a temperature of 25℃±2℃ and a humidity of 60%, test the compressive strength of the parent rock.

[0040] Table 1 Changes in compressive strength of parent rock with changes in forming pressure in Example 1

[0041]

[0042] Example 2

[0043] Step 1: Take 100 parts by mass of steel slag powder and 10-15 parts by mass of acetic acid solution, with acetic acid concentrations of 0 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L and 6 mol / L, mix them evenly, press them at a molding pressure of 8 MPa for 2 minutes, and demold to obtain the mother rock of steel slag aggregate.

[0044] Step 2: Test the compressive strength of the slag matrix after curing for 1 day, 3 days, 7 days and 28 days in an environment with a temperature of 25℃±2℃ and a humidity of 70%. Figure 3 The strength of steel slag is the highest under the action of 3 mol / L acetic acid.

[0045] Example 3

[0046] Step 1: Take 100 parts by mass of steel slag powder and 12 parts by mass of 3 mol / L acetic acid solution, mix them evenly, press them at a molding pressure of 8 MPa for 2 minutes, and demold to obtain the mother rock of steel slag aggregate.

[0047] Step 2: After curing for 1 day in an environment with a temperature of 25℃±2℃ and a humidity of 80%, crushing is performed to obtain steel slag aggregate with a size of 4.75-9.50mm.

[0048] Step 3: Continue curing until the age of 3 days and then test the crushing value and water absorption rate of the aggregate. The crushing value is 9.4% and the water absorption rate is 6.4%.

[0049] Step 4: The crushing value and water absorption rate of the aggregate cured to 28 days were tested. The crushing value was 7.1% and the water absorption rate was 3.8%.

[0050] Example 4

[0051] Step 1: Take 100 parts by mass of steel slag powder and 12 parts by mass of 1 mol / L acetic acid solution, mix them evenly, press them at a molding pressure of 8 MPa for 2 minutes, and demold to obtain the mother rock of steel slag aggregate.

[0052] Step 2: After curing for 1 day in an environment with a temperature of 25℃±2℃ and a humidity of 60%, crushing is performed to obtain steel slag aggregate with a particle size of 4.75-9.50mm.

[0053] Step 3: Continue curing until the age of 28 days and then test the crushing value and water absorption rate of the aggregate. The crushing value is 9.9% and the water absorption rate is 6.8%.

[0054] Comparative Example 1

[0055] A method for preparing steel slag aggregate by vibration molding

[0056] Step 1: Take 100 parts by mass of steel slag powder and 25 parts by mass of 1 mol / L acetic acid solution, mix them evenly, and vibrate to form them.

[0057] Step 2: Curing for 3 days in an environment with a temperature of 25°C ± 2°C and a humidity of 60% and then demoulding to obtain the parent rock of the steel slag aggregate.

[0058] Step 3: Test the 3d compressive strength of the parent rock, which is 1.2 MPa.

[0059] Comparative Example 2

[0060] A method for preparing steel slag aggregate by pressing and forming

[0061] Step 1: Take 100 parts by mass of steel slag powder and 25 parts by mass of 1 mol / L acetic acid solution, mix them evenly, and vibrate them under a pressure of 16 MPa.

[0062] Step 2: Curing for 1 day in an environment with a temperature of 25°C ± 2°C and a humidity of 60% and then demoulding to obtain the mother rock of the steel slag aggregate.

[0063] Step 3: After continuing to maintain for 3 days, the 3d compressive strength of the parent rock was tested and found to be 15.2 MPa.

[0064] Comparative Example 3

[0065] A method for preparing aggregate by treating steel slag with water

[0066] Step 1: Take 100 parts by mass of steel slag powder and 12 parts by mass of water, mix them evenly, press them at a molding pressure of 8 MPa for 2 minutes, and demold to obtain the mother rock of steel slag aggregate.

[0067] Step 2: After curing for 3 days in an environment with a temperature of 25℃±2℃ and a humidity of 80%, crushing is performed to obtain steel slag aggregate with a size of 4.75-9.50mm.

[0068] Step 3: Continue curing until the aggregate reaches 28 days old and test its crushing value and water absorption rate. The crushing value is 17.2% and the water absorption rate is 12.9%.

[0069] Comparative Example 4

[0070] A natural aggregate: basalt is crushed to 4.75-9.50 mm as a natural aggregate. The crushing value is 6.8% and the water absorption rate is 0.9%.

[0071] Comparative Example 5

[0072] Untreated steel slag aggregate: Untreated lump steel slag is directly crushed to 4.75-9.50 mm as steel slag aggregate. The crushing value is 9.7% and the water absorption rate is 4.9%.

[0073] The 28-day-old aggregate in Example 3 and the natural aggregate in Comparative Example 4 were used to prepare cement-based materials. The specific operation was as follows: 180 g of cement was put into a mixing pot, stirred evenly, and then 72 g of water was poured in. After continuing to stir evenly, 360 g of natural aggregate or steel slag aggregate with a particle size of 4.75-9.50 mm was poured in. After stirring evenly, the mixture was poured into a 40×40×40 mm mold and vibrated to produce cement test blocks, 3 blocks per group.

[0074] Table 2 Cement steel slag test block mix ratio

[0075]

[0076] After curing for 24 hours in an environment with a temperature of 25℃±2℃ and a humidity of 60%, the specimens were demoulded and cured for another 48 hours under the same conditions. The compressive strength of the specimens was tested and the stability of the specimens was characterized by the cooking method.

[0077] Table 3 Compressive strength and soundness of cement steel slag test blocks

[0078]

[0079] As shown in Example 1 and Comparative Example 1, press molding can increase the strength of the matrix of steel slag aggregate by more than 10 times, thereby ensuring the mechanical properties of the aggregate. Comparative Example 2 used a molding pressure exceeding 12 MPa to prepare the matrix. Excessive pressure not only makes demolding difficult but also creates microcracks, thereby reducing the strength of the matrix.

[0080] Examples 2 and 3 demonstrate the strength-enhancing effect of acetic acid on steel slag aggregate. The changes in water absorption in Example 3 demonstrate its excellent repair effect on microcracks caused by crushing. Compared to the untreated steel slag aggregate in Comparative Example 5, the 28-day-old aggregate prepared in Example 3 exhibits a low crushing value, high strength, and low water absorption. Comparative Example 3, which uses water-treated steel slag, demonstrates low aggregate strength and high water absorption, inferior to the acetic acid-treated steel slag aggregate.

[0081] Aggregates produced from weakly acid-activated steel slag debris are used in cement-based materials, resulting in superior mechanical properties and stability that meets usage requirements. This invention addresses the issues of low hydration activity and poor stability of steel slag, and improves the utilization rate of steel slag.

Claims

1. A method for treating steel slag, characterized in that: The steps include: 1) uniformly mixing steel slag chips with a weak acid solution to obtain a slurry; 2) The slurry is poured into a mold and pressed into shape, and then demolded after forming; the molding pressure is 4-12 MPa, and the holding time is not less than 1 minute; 3) Place in an environment with a temperature of 25℃±2℃ and a humidity of 60% to 80% for 1-3 days; 4) The processing is completed after crushing with a crusher; In step 1), the mass ratio of the weak acid solution to the steel slag is 0.1 to 0.

15.

2. The method according to claim 1, characterized in that In step 1), the particle size of the steel slag is less than 0.178 mm.

3. The method according to claim 1, characterized in that The weak acid is acetic acid solution with a concentration range of 1 mol / L to 6 mol / L.

4. The method according to claim 1, characterized in that After step 4), the retained particle sizes are 4.75-9.50 mm and 9.50-19.50 mm.

5. Application of the treated steel slag obtained by the method according to claims 1-4, characterized in that: Used in cement-based materials as steel slag aggregate.

Images