A modified air quenched steel slag aggregate and a concrete containing the modified air quenched steel slag aggregate

Abstract

The application discloses a modified air-granulated steel slag aggregate, which is obtained by mixing and stirring air-granulated steel slag and a calcium lignosulfonate aqueous solution uniformly and then drying. The application further discloses concrete containing the modified air-granulated steel slag aggregate, which comprises the following raw materials: gravel, crushed stone, yellow sand, the modified air-granulated steel slag aggregate and cement. The modified air-granulated steel slag aggregate can effectively improve the strength of the concrete, and the concrete has good mechanical properties, so that the application of the air-granulated steel slag as a concrete aggregate is realized, which has important significance for the bulk utilization of steel slag.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource utilization of steel slag, and particularly relates to a modified air-quenching steel slag aggregate and concrete containing the modified air-quenching steel slag aggregate. BACKGROUND

[0002] Steel slag is a by-product generated in the process of steelmaking. In order to utilize the steel slag, it needs to be pretreated. According to different pretreatment processes, the pretreated steel slag can be divided into hot leaching steel slag, roller steel slag, air-quenching steel slag, hot splashing steel slag and the like. Although the steel slag has good solidity and large hardness, due to the fact that a certain amount of unstable fCaO component is contained in most of the steel slag, the steel slag cannot be used as concrete aggregate.

[0003] The air-quenching steel slag is obtained by using high-speed airflow to break the liquid steel slag falling from the air into small droplets, and then falling into a water pool for cooling. Since the fine granulation process solves the problem of difficult digestion of large blocks of lime in the slag, the fCaO content in the air-quenching slag is extremely low, and is basically below 1%, so that the air-quenching slag can be used as concrete aggregate. However, it is found in actual application that the concrete mixed with the air-quenching steel slag as the aggregate has a transition layer between the air-quenching steel slag and the cement paste, which leads to the problem of poor adhesion between the air-quenching steel slag and the cement paste, reduces the strength of the concrete, and particularly has potential risks on long-term strength and durability of the concrete, thereby limiting the bulk utilization of the air-quenching steel slag in the field of building concrete. SUMMARY

[0004] Based on the technical problems existing in the background art, the present application provides a modified air-quenching steel slag aggregate and concrete containing the modified air-quenching steel slag aggregate.

[0005] The modified air-quenching steel slag aggregate provided by the present application is obtained by uniformly mixing and stirring the air-quenching steel slag and a calcium lignosulfonate aqueous solution, and then drying.

[0006] Preferably, the mass of the calcium lignosulfonate accounts for 0.5-2% of the mass of the air-quenching steel slag; preferably, the mass of the calcium lignosulfonate accounts for 1% of the mass of the air-quenching steel slag.

[0007] Preferably, the particle size of the air-quenching steel slag is 0.1-2.5 mm, and the fCaO content in the air-quenching steel slag is ≤1 wt%.

[0008] The concrete containing the modified air-quenching steel slag aggregate comprises the following raw materials: stone, gravel, yellow sand, the modified air-quenching steel slag aggregate and cement.

[0009] Preferably, the mass ratio of the gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate, and cement is 300:(170-890):620:(240-960):(340-360); preferably, the mass ratio of the gravel, crushed stone, yellow sand, and modified air-quenched steel slag aggregate is 300:290:620:840:350.

[0010] Preferably, the water-cement ratio of the concrete is 0.35 to 0.45.

[0011] A method for preparing concrete containing modified air-quenched steel slag aggregate involves first mixing the gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate, and cement, then adding water and stirring evenly. The mixture is then poured into a mold, vibrated to form the concrete, and the resulting green concrete is then subjected to steam curing and water curing in sequence to obtain the final product.

[0012] Preferably, the steam curing temperature is 50-80℃ and the steam curing time is 6-10h; preferably, the steam curing temperature is 60℃ and the steam curing time is 8h.

[0013] Preferably, the watering and maintenance period is ≥28 days.

[0014] The beneficial effects of this invention are as follows:

[0015] Air-quenched steel slag is obtained by breaking liquid steel slag into fine droplets using a high-speed airflow, resulting in mostly spherical shapes and relatively smooth surfaces. This leads to a transition layer between the slag and cement paste, resulting in poor adhesion. Therefore, when air-quenched steel slag is used as concrete aggregate, the poor adhesion between it and the cement paste causes a decrease in concrete strength. This invention addresses this issue by mixing and drying air-quenched steel slag with an aqueous solution of calcium lignosulfonate. The resulting modified air-quenched steel slag aggregate has a calcium lignosulfonate coating layer on its surface, which increases its adhesion to the cement paste, thereby improving concrete strength. This invention provides a simple and inexpensive method to eliminate the transition layer between air-quenched steel slag aggregate and cement paste, solving the problem of poor adhesion between the aggregate and cement paste, improving the strength of air-quenched steel slag aggregate concrete, and giving the concrete good mechanical properties. This realizes the application of air-quenched steel slag as concrete aggregate and is of great significance for the large-scale utilization of steel slag. Attached Figure Description

[0016] Figure 1 This is an optical microscope image (200×) of concrete in Embodiment 1 of the present invention. Figure 1 In the middle: 1-air-quenched steel slag; 2-hydration product matrix; 3-pebbles.

[0017] Figure 2 This is an optical microscope image (200×) of the concrete in Comparative Example 1 of the present invention.Figure 2 Mixture: 1 - Air-quenching steel slag; 2 - Hydration product matrix; 3 - Stone; 4 - Transition layer. DETAILED DESCRIPTION

[0018] Hereinafter, the technical solutions of the present application will be described in detail through specific examples.

[0019] In the following examples, the air-quenching steel slag is produced by Ma Steel Company; the particle size of the stone is 5-20 mm; the particle size of the gravel is 1-5 mm; the particle size of the yellow sand is <1 mm; and the cement is P.O 42.5 cement.

[0020] Example 1

[0021] Preparation of modified air-quenching steel slag aggregate:

[0022] Take 4.2 kg of calcium lignosulfonate, dissolve it in water to obtain a calcium lignosulfonate aqueous solution; mix and stir the above calcium lignosulfonate aqueous solution with 840 kg of air-quenching steel slag with a particle size of 0.1-2.5 mm uniformly, and dry to obtain the modified air-quenching steel slag aggregate.

[0023] Preparation of concrete containing modified air-quenching steel slag aggregate:

[0024] Mix 840 kg of modified air-quenching steel slag aggregate with 300 kg of stone, 290 kg of gravel, 620 kg of yellow sand, and 350 kg of cement, add 140 kg of water and stir uniformly, then pour into a mold, vibrate to form, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d, to obtain the concrete.

[0025] Example 2

[0026] Preparation of modified air-quenching steel slag aggregate:

[0027] Take 8.4 kg of calcium lignosulfonate, dissolve it in water to obtain a calcium lignosulfonate aqueous solution; mix and stir the above calcium lignosulfonate aqueous solution with 840 kg of air-quenching steel slag with a particle size of 0.1-2.5 mm uniformly, and dry to obtain the modified air-quenching steel slag aggregate.

[0028] Preparation of concrete containing modified air-quenching steel slag aggregate:

[0029] Mix 840 kg of modified air-quenching steel slag aggregate with 300 kg of stone, 290 kg of gravel, 620 kg of yellow sand, and 350 kg of cement, add 140 kg of water and stir uniformly, then pour into a mold, vibrate to form, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d, to obtain the concrete.

[0030] Example 3

[0031] Preparation of modified air-quenching steel slag aggregate:

[0032] Take 16.8 kg of calcium lignosulfonate, dissolve in water to obtain a calcium lignosulfonate aqueous solution; mix the above calcium lignosulfonate aqueous solution with 840 kg of air quenched steel slag with particle size of 0.1-2.5 mm, stir uniformly, and dry to obtain modified air quenched steel slag aggregate.

[0033] Preparation of concrete containing modified air quenched steel slag aggregate:

[0034] Mix 840 kg of modified air quenched steel slag aggregate with 300 kg of stone, 290 kg of gravel, 620 kg of yellow sand and 350 kg of cement, add 140 kg of water and stir uniformly, then pour into a mold, vibrate and shape, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d to obtain the product.

[0035] Example 4

[0036] Preparation of modified air quenched steel slag aggregate according to the method of Example 1.

[0037] Preparation of concrete containing modified air quenched steel slag aggregate:

[0038] Mix 960 kg of modified air quenched steel slag aggregate with 300 kg of stone, 180 kg of gravel, 620 kg of yellow sand and 340 kg of cement, add 130 kg of water and stir uniformly, then pour into a mold, vibrate and shape, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d to obtain the product.

[0039] Example 5

[0040] Preparation of modified air quenched steel slag aggregate according to the method of Example 1.

[0041] Preparation of concrete containing modified air quenched steel slag aggregate:

[0042] Mix 240 kg of modified air quenched steel slag aggregate with 300 kg of stone, 880 kg of gravel, 620 kg of yellow sand and 360 kg of cement, add 150 kg of water and stir uniformly, then pour into a mold, vibrate and shape, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d to obtain the product.

[0043] Comparative Example 1

[0044] Preparation of concrete containing air quenched steel slag:

[0045] Mix 840 kg of air quenched steel slag with particle size of 0.1-2.5 mm with 300 kg of stone, 290 kg of gravel, 620 kg of yellow sand and 350 kg of cement, add 140 kg of water and stir uniformly, then pour into a mold, vibrate and shape, then steam the obtained green body at 60°C for 8 h, and then water curing for 28 d to obtain the product.

[0046] Comparative Example 2

[0047] Preparation of concrete containing air-quenched steel slag and calcium lignosulfonate:

[0048] Mix 840 kg of air-quenched steel slag with a particle size of 0.1–2.5 mm, 4.2 kg of calcium lignosulfonate, 300 kg of gravel, 290 kg of crushed stone, 620 kg of yellow sand, and 350 kg of cement. Add 140 kg of water and stir evenly. Pour the mixture into a mold and vibrate to form the green body. Then, steam-cur the green body at 60°C for 8 hours and water-cur for 28 days to obtain the final product.

[0049] Comparative Example 3

[0050] Preparation of modified air-quenched steel slag aggregate:

[0051] Weigh 3.36 kg of calcium lignosulfonate, dissolve it in water to obtain an aqueous solution of calcium lignosulfonate; mix the above aqueous solution of calcium lignosulfonate with 840 kg of air-quenched steel slag with a particle size of 0.1-2.5 mm, stir evenly, and dry to obtain modified air-quenched steel slag aggregate.

[0052] Preparation of concrete containing modified air-quenched steel slag aggregate:

[0053] Mix 840 kg of modified air-quenched steel slag aggregate with 300 kg of gravel, 290 kg of crushed stone, 620 kg of yellow sand and 350 kg of cement, add 140 kg of water and stir evenly, then pour into a mold and vibrate to form. Then, steam-cur the resulting green body at 60℃ for 8 hours and then water-cur for 28 days to obtain the final product.

[0054] Comparative Example 4

[0055] Preparation of modified air-quenched steel slag aggregate:

[0056] Weigh 21 kg of calcium lignosulfonate, dissolve it in water to obtain an aqueous solution of calcium lignosulfonate; mix the above aqueous solution of calcium lignosulfonate with 840 kg of air-quenched steel slag with a particle size of 0.1-2.5 mm, stir evenly, and dry to obtain modified air-quenched steel slag aggregate.

[0057] Preparation of concrete containing modified air-quenched steel slag aggregate:

[0058] Mix 840 kg of modified air-quenched steel slag aggregate with 300 kg of gravel, 290 kg of crushed stone, 620 kg of yellow sand and 350 kg of cement, add 140 kg of water and stir evenly, then pour into a mold and vibrate to form. Then, steam-cur the resulting green body at 60℃ for 8 hours and then water-cur for 28 days to obtain the final product.

[0059] Test case

[0060] The 28d compressive strength of the concrete in Example 1-3 and Comparative Example 1-4 was tested (test method referred to JGJ / T384-2016), and the results are shown in Table 1:

[0061] Table 1 28d compressive strength of the concrete obtained in the examples and comparative examples

[0062] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Compressive strength / MPa 33.56 39.74 32.03 28.82 26.12 29.76 28.70

[0063] As can be seen from Table 1, by comparing the compressive strength of Example 1 and Comparative Example 1, it can be found that after the calcium lignosulfonate is used to coat the air quenched steel slag in a suitable proportion, the strength of the concrete is significantly improved. This is because the adhesion of the calcium lignosulfonate makes the adhesion between the air quenched steel slag and the cement paste stronger, which can be closely combined with the hydration products, and the strength of the concrete is significantly improved. In Comparative Example 2, the calcium lignosulfonate and the air quenched steel slag are added to the concrete separately instead of being coated, and the strength of the concrete is reduced, which shows that adding the calcium lignosulfonate alone in this proportion has a negative impact on the strength of the concrete. The amount of calcium lignosulfonate in Comparative Example 3 is too low, and the coating is not sufficient, so the improvement effect on the strength is not good. In Comparative Example 4, the amount of calcium lignosulfonate is too high, and under the action of mechanical force during mixing, the calcium lignosulfonate adhered to the surface of the air quenched steel slag will fall off, and after dispersion, it will have an adverse effect on the strength of the concrete.

[0064] The concrete in Example 1 and Comparative Example 1 was analyzed by optical microscope at a magnification of 200X, and the photos are shown in Figure 1 and Figure 2 It can be seen that when the air quenched steel slag is directly used as aggregate, there is a thin transition zone between the spherical air quenched slag and the hydration product matrix. This shows that when the air quenched steel slag is directly used as aggregate, there is a transition layer between the air quenched steel slag and the surrounding cement paste. This transition layer will lead to a decrease in the strength of the concrete. That is to say, there is a problem of poor adhesion between the air quenched steel slag aggregate and the cement paste. When the modified air quenched steel slag obtained by coating with calcium lignosulfonate in Example 1 is used as aggregate, the transition layer around the air quenched steel slag disappears, and the hydration product matrix wraps the air quenched steel slag. This shows that after the modification treatment according to the present application, the transition layer between the air quenched steel slag aggregate and the cement paste disappears, and the problem of poor adhesion between the air quenched steel slag aggregate and the cement paste is solved, which significantly improves the strength of the concrete.

[0065] The above description is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes within the technical scope disclosed in the present application according to the technical solution and inventive concept of the present application, which should be covered within the protection scope of the present application.

Claims

1. A type of concrete containing modified air-quenched steel slag aggregate, characterized in that, It is composed of the following raw materials: gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate, and cement; the mass ratio of the gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate, and cement is 300:(170~890):620:(240~960):(340~360); the particle size of the gravel is 5~20mm, and the particle size of the crushed stone is 1~5mm; The modified air-quenched steel slag aggregate is obtained by mixing and stirring air-quenched steel slag with an aqueous solution of calcium lignosulfonate until homogeneous, followed by drying; the calcium lignosulfonate accounts for 0.5-2% of the mass of the air-quenched steel slag. The method for preparing concrete containing modified air-quenched steel slag aggregate is as follows: First, mix the gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate and cement, add water and stir evenly, then pour into a mold, vibrate to form, and then the resulting green embryo is successively steam-cured and water-cured to obtain the final product.

2. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The mass of the calcium lignosulfonate accounts for 1% of the mass of the air-quenched steel slag.

3. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The particle size of the air-quenched steel slag is 0.1~2.5mm, and the fCaO content in the air-quenched steel slag is ≤1wt%.

4. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The mass ratio of the gravel, crushed stone, yellow sand, modified air-quenched steel slag aggregate, and cement is 300:290:620:840:350; the particle size of the gravel is 5~20mm, and the particle size of the crushed stone is 1~5mm.

5. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The water-cement ratio of the concrete is 0.35~0.

45.

6. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The steam curing temperature is 50~80℃, and the steam curing time is 6~10 h; The watering and maintenance period is ≥28 days.

7. The concrete containing modified air-quenched steel slag aggregate according to claim 1, characterized in that, The steam curing temperature is 60℃, and the steam curing time is 8 hours.

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