High-activity steel slag-mineral slag composite micro powder and preparation method thereof

Abstract

The invention discloses high-activity steel slag-slag composite micro powder and a preparation method thereof. The preparation method comprises the following steps: step 1, respectively selecting steel slag and slag; 2, selecting YT-K6 as a surfactant, wherein the doping amount of the YT-K6 is 0.06-0.08% of the total mass of the steel slag and the mineral slag; and 3, respectively weighing the steel slag and the slag, simultaneously adding an active agent, and carrying out composite grinding in a mill for 90-120 minutes until the specific surface area of the material reaches 550-680 m < 2 > / kg and the activity index reaches 110-120%, thereby obtaining the high-activity steel slag-slag composite micro powder. The composite micro powder prepared by the invention has the characteristics of good stability and high hydration activity.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource treatment, and particularly relates to a high-activity steel slag-slag composite micropowder and a preparation method thereof. Background Art

[0002] The activity of steel slag powder is typically enhanced through mechanical grinding, high-temperature activation, and chemical admixtures. Due to its high iron oxide content, steel slag has poor grindability, resulting in high energy consumption during production, which does not meet the requirements of a low-carbon, circular economy. Adding an activator during the grinding process adsorbs onto the surface of the slag, improving grindability and increasing fineness. The activator also amorphizes the slag crystals under mechanical forces, promoting hydration and thereby increasing the hydration activity of the slag.

[0003] Surface chemical modification is a common method of chemical activation, achieved through chemical reactions or chemical adsorption between surface modifiers and particle surfaces. Research has found that surfactants provide a significant grinding aid when co-grinded with steel slag. Adding surfactants to the grinding process effectively increases the specific surface area of steel slag powder at the same grinding time. The activity index of the resulting steel slag powder at all ages is significantly improved. Increasing the particle fineness of steel slag powder improves its hydration activity and volume stability. Using steel slag powder and granulated blast furnace slag as a mixed mineral admixture in concrete is an effective way to increase the utilization rate of SS. The median diameter (D50) of steel slag particles exhibits regular changes with time and modifier dosage. The grinding process can be divided into three stages: the crushing and refinement of large particles, with a rapid increase in the proportion of fine particles; the agglomeration of fine particles, resulting in particle coarsening; and the equilibrium stage of the grinding process. There is an optimal value for time and modifier dosage. The addition of modifiers causes the large amount of mechanical energy applied to be stored by changing the structure of slag particles, causing structural defects and lattice distortion.

[0004] In recent years, fly ash, silica fume, slag and other mineral admixtures have been used and consumed in large quantities. High-quality admixtures have become increasingly scarce, and their prices have continued to rise. Therefore, if high-activity composite admixtures can be prepared from steel slag and slag, the added value of steel slag will be significantly increased, promoting its large-scale utilization.

[0005] Tang Weijun, Ren Zhongxing and others found that the composite micropowder was only filled between cement stones in the early stage, acting as a filler, and gradually hydrated in the later stage. The proportion of steel slag in the composite micropowder is 20% to 30%, and the fineness of the composite micropowder is about 450m 2When it is [X] kg, the activity of the composite fine powder can reach or approach the activity requirements of S95 grade powder, which can meet the strength design requirements of concrete structures. There is a large amount of free calcium oxide in steel slag, and the content of steel slag in this composite fine powder reaches 60%-80%. During the use process, problems of poor soundness will be faced.

[0006] It has also been found in research that after mixing steel slag and slag in a certain proportion, the composite powder can accelerate the hydration process of each other. Steel slag and slag can stimulate and promote each other's hydration, producing a composite superposition effect. Zhao Jihui, Li Zhangheng and others have found that steel slag and GBFS have a significant hydration superposition effect, and the strength of the slurry is much higher when the two are used together. The early hydration of steel slag will increase the pH value and conductivity of the pore solution, promote the dissolution and pozzolanic reaction of aluminosilicate glass in GBFS. At the same time, the consumption of Ca(OH)2 will promote the further hydration of steel slag through the pozzolanic reaction. The synergistic hydration effect of the composite fine powder will promote hydration and produce more hydration products to fill the pore structure, thus obtaining good hardening properties. In this study, the ratio between steel slag and slag is 1:1 and 2:3. The large content of steel slag in the composite fine powder makes the setting time of the cementitious material system increase and the early strength increase slowly. Summary of the Invention

[0007] In order to overcome the above technical problems, the purpose of the present invention is to provide a high-activity steel slag-slag composite fine powder and its preparation method. The composite fine powder prepared by this preparation method has the characteristics of good soundness and high hydration activity.

[0008] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A high-activity steel slag-slag composite fine powder, including steel slag and slag, and the steel slag and slag are compounded according to a mass ratio of 3:7.

[0010] When steel slag and slag are compounded, the Ca dissolved from steel slag 2+ is for the utilization of slag. The silicon-aluminum vitreous body in slag and its "secondary hydration reaction" with the hydration products Ca(OH)2 of steel slag and cement generate low-calcium type hydrated calcium silicate gel; the unhydrated steel slag particles fill the pores, increasing the density of the system and cross-linking with the hydrated calcium silicate gel network.

[0011] The pore size distribution of the high-activity composite fine powder cement system is uniform and continuous, and the pore size is mainly concentrated in the range of 5-20 nm, indicating that its microstructure is dense.

[0012] A preparation method of a high-activity steel slag-slag composite fine powder, including the following steps;

[0013] Step 1: Select steel slag and slag respectively;

[0014] Step 2: Select YT-K6 as the surfactant, and the dosage is 0.06%-0.08% of the total mass of steel slag and slag;

[0015] Step 3: Weigh steel slag and slag respectively, add the surfactant at the same time, and perform combined grinding in a mill for 90-120 min. Wait until the specific surface area of the material reaches 550-680 m 2 / kg and the activity index reaches 110%-120%, then high-activity steel slag-slag composite fine powder is obtained.

[0016] In the said Step 3, the mass ratio of steel slag to slag is 3:7.

[0017] The high-activity steel slag-slag composite fine powder has small particle size, high dispersibility, few and uniform coarse particles, few edges and corners on the surface of the fine powder particles, and the particle morphology tends to be spherical. These microscopic characteristics determine that the high-activity steel slag-slag composite fine powder has good micro-aggregate effect and pozzolanic effect, thus showing high activity.

[0018] Using the high-activity steel slag-slag composite fine powder as a high-quality mineral admixture in concrete production is beneficial to enhancing the workability and durability of concrete.

[0019] The beneficial effects of the present invention:

[0020] The present invention can develop a low-cost preparation technology for steel slag-slag composite fine powder, form the optimal proportion design of the composite fine powder, realize the improvement of the workability, mechanical properties and durability of concrete, and its large-scale production and application have significant economic and social benefits.

[0021] The present invention forms the optimal proportion of the composite fine powder (the mass ratio of steel slag to slag is 3:7, and the dosage of the surfactant is 0.06%-0.08%). Before adding the surfactant, the 7-day and 28-day activity indexes of the composite fine powder with this proportion are both greater than the 7-day and 28-day activity indexes of other proportion composite powders with the same fineness, and at the same time, the activity index is also better than that of pure slag powder with the same fineness. After adding 0.06% of the surfactant based on the total mass of steel slag and slag, the 7-day and 28-day activity indexes of the composite fine powder increase from 79.8% and 104.5% to 95% and 121.3% respectively, and the activity of the composite powder at each age has a greater improvement. And through the hydration heat test, it can be known that at this dosage, the hydration process of the composite powder will accelerate into the induction period and acceleration period, the acceleration period is steeper and the heat flow peak value is significantly higher than that of the composite powder system without adding the surfactant. The surfactant with this dosage can promote the early hydration of steel slag and slag and improve the reaction process of the composite system. Description of the Drawings

[0022] Figure 1 It is a SEM schematic diagram of high-activity steel slag-slag composite fine powder.

[0023] Figure 2It is the mechanical strength diagram of the high-activity steel slag-slag composite powder cement system.

[0024] Figure 3 It is the schematic diagram of the hydration heat of the composite micro-powder cement system.

[0025] Figure 4 It is the mercury intrusion graph of the composite micro-powder cement system. Specific implementation manners

[0026] The present invention will be further described in detail below with reference to the accompanying drawings.

[0027] As Figures 1-4 shown, a preparation method of high-activity steel slag-slag composite micro-powder includes the following steps;

[0028] Step 1: Select steel slag and slag respectively;

[0029] Step 2: Select the product YT-K6 of Shaanxi Yitianjian as the surfactant, and the dosage is 0.06%-0.08% of the total mass of steel slag and slag;

[0030] Step 3: Weigh steel slag and slag respectively, add the surfactant at the same time, and perform composite grinding in a mill for 90-120 min. When the specific surface area of the material reaches 550-680 m 2 / kg and the activity index reaches 110%-120%, high-activity steel slag-slag composite micro-powder is obtained.

[0031] In the said step 3, the mass ratio of steel slag to slag is 3:7.

[0032] The high-activity steel slag-slag composite micro-powder has small particle size, high dispersibility, few and uniform coarse particles, few edges and corners on the surface of the micro-powder particles, and the particle morphology tends to be spherical. These microscopic characteristics determine that the high-activity steel slag-slag composite micro-powder has good micro-aggregate effect and pozzolanic effect, and thus shows high activity.

[0033] Using high-activity steel slag-slag composite micro-powder as a high-quality mineral admixture in concrete production is beneficial to enhancing the workability and durability of concrete.

[0034] The chemical composition of the said steel slag mainly includes oxides such as CaO, Fe2O3, SiO2, etc., accounting for 80.58% of the whole. The activity coefficient of the steel slag is 2.61, and the basicity coefficient is 2.24, belonging to high-alkali slag;

[0035] The chemical composition of the slag mainly includes oxides such as CaO, SiO2, Al2O3, and MgO, accounting for 93.58% of the whole. The basicity coefficient of the slag is 1.22, belonging to basic slag, and its mass coefficient is 2.21, meeting the requirement of K≥1.2 in Chinese national standard GB / T203-2008 and K>1.6. The activity coefficient is 1.51, belonging to excellent slag.

[0036] The high-activity steel slag-slag composite micro-powder has pozzolanic effect and micro-aggregate effect, which can improve the stability of concrete and reduce the risk of cracking. At the same time, the composite micro-powder can significantly improve the chloride ion penetration resistance and frost resistance of concrete and reduce the dry shrinkage rate of concrete. After the steel slag and slag are compounded in a certain proportion, the composite powder can accelerate the hydration process of each other, and the steel slag and slag can stimulate and promote each other's hydration. The slag needs an alkaline environment during the hydration process to dissolve its own silicon-aluminum structure, and the dissolution of free calcium oxide in the steel slag produces Ca 2+ which can promote its hydration process. When the steel slag and slag are compounded, the Ca 2+ dissolved from the steel slag can be utilized by the slag. Therefore, the steel slag and slag can stimulate and promote each other's hydration, producing a composite superposition effect. The silicon-aluminum glass body in the slag and its "secondary hydration reaction" with the hydration products Ca(OH)2 of the steel slag and cement generate low-calcium type hydrated calcium silicate gel. The unhydrated steel slag particles fill the pores, increasing the density of the system and cross-linking with the hydrated calcium silicate gel network, which will significantly improve the relevant properties of the cementitious system.

[0037] Example 1:

[0038] Step 1: Select steel slag and slag respectively;

[0039] Step 2: Select YT-K6 as the surfactant, and the dosage is 0.06%-0.08% of the total mass of the steel slag and slag;

[0040] Step 3: The steel slag and slag are compounded according to a mass ratio of 3:7, and at the same time, the surfactant is added, and the composite powder is ground in the mill for 90 minutes. When the specific surface area of the material reaches 550 m 2 / kg and the activity index reaches 110%-, the high-activity steel slag-slag composite micro-powder is obtained.

[0041] Example 2:

[0042] Step 1: Select steel slag and slag respectively;

[0043] Step 2: Select YT-K6 as the surfactant, and the dosage is 0.08% of the total mass of the steel slag and slag;

[0044] Step 3: Weigh steel slag and slag respectively, add activator at the same time, and perform combined grinding in a mill for 120 min. When the specific surface area of the material reaches 680 m 2 / kg and the activity index reaches 120%, highly active steel slag-slag composite fine powder can be obtained.

[0045] (1) Steel slag and slag with the same mass are ball milled at the same time gradient. When the ball milling time is 120 min and 150 min, the fineness of steel slag fine powder and slag fine powder is the closest. When the ball milling time is 120 min, the D50 of steel slag powder and slag powder is the closest, and the difference between them is only 0.58 μm. When the ball milling time is 150 min, the D50 and VMD of steel slag powder and slag powder are very close, and the differences are 1.91 μm and 1.12 μm respectively.

[0046] (2) When the combined grinding time is 120 min and 150 min, the 28-day activity index of the combined fine powder with less than 30% steel slag content is greater than that of pure slag fine powder. When the grinding time of the composite powder is 120 min and 150 min and the steel slag content is 30%, the 28-day activity index of the composite fine powder is the largest, which are 104.9% and 113.4% respectively.

[0047] (3) The combined powder with a mass ratio of steel slag:slag of 3:7 is subjected to combined grinding according to a preset time gradient (30, 45, 60, 90, 120, 150, 180 min). The specific surface area of the combined fine powder increases linearly with the extension of the grinding time, and the specific surface areas are 341, 444, 454, 547, 648, 740, 814 m 2 / kg.

[0048] When the grinding time is 180 min, the specific surface area is the largest, which is 814 m 2 / kg, and the corresponding 28-day activity index at this time is 108.6%. The 28-day activity index of the combined fine powder first increases and then decreases with the increase of the grinding time. Under this time gradient, the 28-day activity indexes of the combined powder are 85.3%, 97.6%, 99.6%, 103.8%, 106.5%, 107.3%, 98.3% respectively. When the grinding time is 150 min, the 28-day activity index of the combined fine powder is the largest, which is 117.6%, and the specific surface area of the combined fine powder at this time is 740 m 2 / kg.

[0049] (4) When the grinding time is 30 min, the incorporation of the activator has a certain promoting effect on the fineness and hydration ability of the combined fine powder. With the increase of the activator dosage, the specific surface area of the combined fine powder first increases and then decreases, and the specific surface area changes in the range of 346±5 m 2 / kg. When the activator dosage is 0.08%, the specific surface area is the largest, which is 351 m2 / kg. The 28-day activity index of the composite fine powder increases first and then decreases as the dosage of the activator increases. When the dosage of the activator is 0.12%, its 28-day activity index is the largest, which is 98.5%.

[0050] When the grinding time is 60 min, the activator significantly improves the fineness and hydration ability of the composite fine powder. As the dosage of the activator increases, the specific surface area of the composite fine powder shows a trend of increasing first and then decreasing, and the change range of the specific surface area is 484±30 m 2 / kg. When the dosage of the activator is 0.08%, the specific surface area is the largest, which is 514 m 2 / kg. As the dosage of the activator increases, its 28-day activity index increases first and then decreases as a whole. When the dosage of the activator is 0.12%, its 28-day activity index is the largest, which is 109.0%.

[0051] When the grinding time is 90 min, the activator has a certain influence on the fineness and hydration ability of the composite fine powder. As the dosage of the activator increases, the specific surface area of the composite fine powder shows a trend of increasing first and then decreasing, and the change range of the specific surface area is 553±13 m 2 / kg. When the dosage of the activator is 0.10%, the specific surface area is the largest, which is 566 m 2 / kg. However, the improvement effect of the activator on the 28-day activity index of the composite fine powder is not significant, and even decreases. When no activator is added, its 28-day activity index is 110.0%. When the dosage of the activator is 0.06%, the activity index under this grinding time is the largest, which is 113.9%.

[0052] When the grinding time is 120 min, within the range of the dosage of the activator being 0.00%, 0.06%, 0.08%, 0.10%, and 0.12%, the change of the specific surface area of the steel slag-slag composite fine powder fluctuates, showing a state of increasing first and then decreasing, then increasing and decreasing again. The change range of its specific surface area is 653±32 m 2 / kg. When the active dosage is 0.10%, the specific surface area of the composite fine powder is the largest, which is 685 m 2 / kg. The 28-day activity index of the composite fine powder increases first and then decreases as a whole with the increase of the dosage of the activator. When the dosage of the activator is 0.06%, the 28-day activity index is the largest, which is 121.3%.

[0053] When the grinding time is 150 min, the dosage of the activator has a significant influence on the fineness of the composite fine powder. As the dosage of the activator increases, the specific surface area of the composite fine powder shows a trend of increasing first and then decreasing, and the change range of the specific surface area is 770±30 m 2 / kg. When the dosage of the activator is 0.10%, the specific surface area is the largest, which is 800 m 2 / kg. The activator has a negative impact on the 28-day activity index of the composite micro-powder ground for 150 min. When no activator is added, its 28-day activity index is the largest, reaching 117.6%.

[0054] Based on the above conclusions, considering energy consumption, the hydration ability of the composite micro-powder, and economic benefits, the composite micro-powder with a grinding time of 120 min and an activator dosage of 0.06% was selected for subsequent research.

[0055] As Figure 1 shown, the high-activity steel slag-slag composite micro-powder has good dispersibility. The composite micro-powder has small particle size, high dispersibility, few and uniform coarse particles, few edges and corners on the surface of the micro-powder particles, and the particle morphology tends to be spherical. These microscopic characteristics determine that the high-activity steel slag-slag composite micro-powder has good micro-aggregate effect and pozzolanic effect, thus showing relatively high activity;

[0056] As Figure 2 shown, the high-activity steel slag-slag composite micro-powder shows good mechanical properties and relatively high activity in the cement system. After adding 0.06% of the activator to the composite micro-powder, its 7-day activity index increases from 79.8% to 95%, and the 28-day activity index rises from 104.5% to 121.3%. It can be seen that this dosage of the activator has a significant promoting effect on the activity of the composite micro-powder.

[0057] As Figure 3 shown, the following are the hydration heat flow curves of the ordinary composite micro-powder and the high-activity steel slag-slag composite micro-powder in the cement system. The data shows that the induction period of the high-activity composite micro-powder cement system with an activator dosage of 0.06% precedes that of the ordinary composite micro-powder cement system, and the heat flow curve in the acceleration period rises rapidly, indicating that the early hydration rate of the high-activity composite micro-powder in the cement system is higher, which can significantly improve the early strength of the cementitious system.

[0058] As Figure 4 shown, the following are the mercury intrusion curves of the ordinary composite micro-powder and the high-activity steel slag-slag composite micro-powder in the cement system. The data shows that the pore size distribution of the high-activity composite micro-powder cement system is uniform and continuous, and the main pore size distribution is concentrated in the range of 5 - 20 nm, indicating that its microstructure is dense. While the pore size distribution curve of the composite micro-powder without the activator shows multiple peaks, indicating that the internal pores are discontinuous.

Claims

1. A high-activity steel slag-slag composite fine powder, characterized in that, It includes steel slag and slag, and the steel slag and slag are compounded according to a mass ratio of 3:7; Ca leached from steel slag 2+ For the utilization of slag, the silica-aluminum glass body in the slag and its "secondary hydration reaction" with the steel slag and the calcium hydroxide (Ca(OH)2) of the cement hydration products generate low-calcium type calcium silicate hydrate gel; the incompletely hydrated steel slag particles fill the pores, increasing the density of the system and cross-linking with the calcium silicate hydrate gel network.

2. The highly active steel slag-slag composite fine powder according to claim 1, wherein The pore size distribution of the high-activity composite micro-powder cement system is uniform and continuous, and the pore size is mainly concentrated in the range of 5-20 nm, indicating that its microstructure is dense.

3. A preparation method of high-activity steel slag-slag composite fine powder, characterized in that, It includes the following steps; Step 1: Select steel slag and slag respectively; Step 2: Select YT-K6 as the surfactant, and the dosage is 0.06%-0.08% of the total mass of steel slag and slag; Step 3: Weigh steel slag and slag respectively, add an activator at the same time, and perform compound grinding in a mill for 90 - 120 min. Wait until the specific surface area of the material reaches 550 - 680 m 2 / kg and the activity index reaches 110% - 120%, then highly active steel slag - slag composite fine powder is obtained.

4. The preparation method of a highly active steel slag-slag composite micro-powder according to claim 3, characterized in that, In the said Step 3, the mass ratio of steel slag to slag is 3:

7.

5. The preparation method of a highly active steel slag-slag composite micro-powder according to claim 3, characterized in that, The high-activity steel slag-slag composite micro-powder has small particle size, high dispersibility, few and uniform coarse particles, few edges and corners on the surface of the micro-powder particles, and the particle morphology tends to be spherical.

6. Use of a highly active steel slag-slag composite micro powder according to any one of claims 1-5, characterized in that, The high-activity steel slag-slag composite micro-powder is used as a high-quality mineral admixture in concrete production.

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