Superfine iron tailing-based geopolymer cementing material as well as preparation method and application thereof

Abstract

The invention discloses a superfine iron tailing-based geopolymer cementing material as well as a preparation method and application thereof. The geopolymer cementing material comprises the following raw material components in parts by weight: 10 to 500 parts of superfine iron tailings, 10 to 600 parts of fly ash, 10 to 600 parts of blast furnace slag, 10 to 50 parts of solid sodium hydroxide crystals and 10 to 100 parts of solid sodium silicate powder. In the invention, the superfine iron tailings, the fly ash and the blast furnace slag play a remarkable synergistic effect, and the proportion of the fly ash to the blast furnace slag can influence the physical and mechanical properties of a gelling system to different degrees. The cementing materials with different strengths can be used in a graded and classified manner, the potential of efficiently realizing three-in-one of solid waste absorption, carbon emission reduction and cost reduction is achieved, and green transformation of mining industry / energy cities is promoted.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology of ultrafine iron tailings, fly ash and blast furnace slag, specifically to an ultrafine iron tailings base polymer cementitious material and its preparation method and application. Background Technology

[0002] In the construction industry, cement production processes emit large amounts of greenhouse gases such as carbon dioxide. Therefore, new green cementitious materials such as geopolymers have emerged. Generally, geopolymers possess superior mechanical properties and durability compared to cement-based materials, while also having lower energy consumption and carbon emissions (approximately 80% reduction). In recent years, incorporating calcium-rich materials (such as blast furnace slag and steel slag) and active aluminosilicate materials (such as fly ash) into geopolymers has been found to fully leverage the synergistic effects of these materials, becoming an important means of improving geopolymer performance. Currently, in the field of industrial solid waste resource utilization, blast furnace slag is the most valuable calcium-rich material, and fly ash is the most widely used active aluminosilicate material. Compared to cement, geopolymers promote the resource utilization of industrial by-products rich in aluminosilicates and calcium.

[0003] Ultrafine iron tailings are solid waste with a particle size of less than 75 μm. They have a large specific surface area and high water content, making them prone to particle agglomeration and thus difficult to recycle effectively. Due to their high silicon and aluminum content, they can be used as a precursor material for geopolymers. However, iron tailings themselves have low activity, and when used as a single precursor to generate geopolymers, they usually require pretreatment such as grinding or calcination. This increases carbon emissions, energy consumption, and the need for advanced equipment, limiting their large-scale utilization.

[0004] In summary, applying ultrafine iron tailings, calcium-rich materials, and active aluminosilicate materials to geopolymers presents a potential solution for obtaining high-performance, low-cost, environmentally friendly, and energy-saving geopolymers. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an ultrafine iron tailings-based polymer cementitious material, its preparation method, and its application. Specifically, it relates to an ultrafine iron tailings-based polymer cementitious material comprising ultrafine iron tailings, fly ash, blast furnace slag, sodium hydroxide crystals, and sodium silicate powder. By investigating the influence of the ratio of fly ash to blast furnace slag on its physical and mechanical properties and revealing its evolution mechanism, ultrafine iron tailings-based polymer cementitious materials with various strength requirements are obtained. The application of this ultrafine iron tailings-based polymer cementitious material enables large-scale resource utilization of fly ash, blast furnace slag, and ultrafine iron tailings, reducing environmental pollution and production costs.

[0006] A polymer cementitious material based on ultrafine iron tailings comprises the following components: by weight, 10-500 parts ultrafine iron tailings, 10-600 parts fly ash, 10-600 parts blast furnace slag, 10-50 parts sodium hydroxide, and 10-100 parts sodium silicate.

[0007] Preferably, the ultrafine iron tailings contains 25%–40% silica, has a specific gravity of 2.6–2.8, a liquid limit of 30%–40%, a plastic limit of 15%–17%, a plasticity index of 18%–20%, an optimum moisture content of 14%–16%, and a maximum dry density of 1500 kg / m³. 3 ~2000kg / m 3 Specific surface area is 23000 cm² -1 ~26000cm -1 .

[0008] Preferably, the fly ash is grade F low-calcium fly ash, with a silica content of 40%~50%, an alumina content of 30%~40%, and a density of 2.0~2.5 g / cm³. 3 Specific surface area is 20000 cm² -1 ~23000cm -1 .

[0009] Preferably, the blast furnace slag is grade S95, with an activity index of over 95%, a silica content of 30%–40%, a calcium oxide content of 30%–40%, an alumina content of 15%–20%, and a density of 3.0 g / cm³. 3 ~3.5g / cm 3 Specific surface area is 22000 cm² -1 ~25000cm -1 .

[0010] The solid sodium hydroxide crystals are blocky crystals with a purity of 97% to 99%.

[0011] Preferably, the solid sodium silicate powder is a white powder with a SiO2:Na2O molar ratio of 3.0M to 3.5M.

[0012] This invention also provides a method for using the above-mentioned ultrafine iron tailings base polymer cementitious material, comprising the following steps:

[0013] (1) After drying the ultrafine iron tailings, fly ash and blast furnace slag, the particle size distribution was tested using a laser particle size analyzer; (2) After boiling the deionized water, cool it to 50℃~60℃, dissolve sodium silicate powder and sodium hydroxide crystals in the deionized water, and cool it to obtain an alkaline activation solution; the SiO2:Na2O molar ratio of the alkaline activation solution is 1.2M~1.4M; (3) Weigh out the ultrafine iron tailings, fly ash and blast furnace slag, mix them evenly and then add the alkali activator solution mentioned in step (2). Stir manually for 1 min to 2 min, then stir using a standard cement mortar mixer. First stir at 50 r / min to 60 r / min for 2 min to 3 min, then stir at 80 r / min to 100 r / min for 1 min to 2 min. Then, manually stir for 30-60 seconds until evenly distributed to obtain fresh ultrafine iron tailings base polymer cementitious material; pour the fresh ultrafine iron tailings base polymer cementitious material into a mold and compact it in a standard vibrator for 1-2 minutes, then let it stand at room temperature for 24-48 hours before demolding. (4) Place the hardened ultrafine iron tailings base polymer cementitious material in a standard curing box for 6-7 days, with a curing temperature of 60-70℃ and a curing humidity of 90%RH-98%RH.

[0014] The above-mentioned ultrafine iron tailings base polymer cementitious materials are used in mine filling materials, ecological concrete materials, road base materials, and building curtain wall block materials.

[0015] Compared with the prior art, the present invention has the following advantages: This invention provides an ultrafine iron tailings geopolymer cementitious material with advantages such as wide availability of materials, low production cost, simple production process, and minimal environmental pollution. Furthermore, this invention fully leverages the synergistic effects of chemical complementarity, physical filling, and reaction sequence of ultrafine iron tailings, fly ash, and blast furnace slag to achieve triple optimization of the geopolymer's strength, environmental friendliness, and economic efficiency, particularly addressing the shortcomings of insufficient activity or compositional fluctuations in single solid wastes. Therefore, this invention has significant economic, social, and environmental benefits.

[0016] 1. Environmental benefits (1) Solid waste utilization: large-scale resource utilization of ultrafine iron tailings, blast furnace slag and fly ash to reduce stockpiling pollution (heavy metals, dust, etc.) and land occupation.

[0017] (2) Low carbon emission reduction: No high-temperature calcination is required, reducing production energy consumption by 60%, and CO2 emissions are about 70% lower than those of cement. It is estimated that each ton of geopolymer emits about 0.2 tons of CO2, while each ton of cement emits about 0.9 tons.

[0018] 2. Economic benefits Low raw material costs: The cost of solid waste and its treatment is far lower than that of cement, and the total raw material cost is expected to be about 30% lower than that of cement (cement relies on expensive limestone).

[0019] 3. Social Impact (1) Circular economy: promote the transformation of mining / thermal power solid waste into treasure and alleviate the pressure of resource depletion.

[0020] (2) Industrial upgrading: drive the green building materials industry chain and help the sustainable development strategy. Attached Figure Description

[0021] Figure 1 This is a particle size distribution diagram of the ultrafine iron tailings in this invention; Figure 2 This is a particle size distribution diagram of fly ash in this invention; Figure 3 This is a particle size distribution diagram of the blast furnace slag in this invention; Figure 4 This is a diagram showing the moisture content of the ultrafine iron tailings in this invention. Figure 5 This is a schematic diagram comparing the consistency and density of Examples 1-5 of the present invention; Figure 6 The figures show the packing density and longitudinal wave velocity results for Examples 1-5 of this invention; Figure 7 The graphs show the compressive strength, splitting tensile strength, and flexural strength results of Examples 1-5 of the present invention. Figure 8 The results of consistency and ultrasonic velocity in Examples 6-12 of this invention are shown in the figure. Figure 9 The compressive strength, splitting tensile strength, and flexural strength of Examples 6-12 of the present invention are given. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Examples 1-5 A polymer cementitious material based on ultrafine iron tailings comprises the following raw material components in parts by weight: 300 parts ultrafine iron tailings, 60-240 parts fly ash, 60-240 parts blast furnace slag, 20 parts sodium hydroxide, and 36.6 parts sodium silicate. When using, add 270 parts water. Specific implementation ratios are shown in Table 1.

[0024] Table 1. Components and weight parts of cementitious materials in Examples 1-5

[0025] The method of using the above-mentioned ultrafine iron tailings base polymer cementitious material includes the following steps: (1) Place the ultrafine iron tailings, fly ash and blast furnace slag in a forced-air drying oven at 105±2℃ and dry them to constant weight. After cooling to room temperature, test their particle size distribution with a laser particle size analyzer. 1) The ultrafine iron tailings contained 33.15% silica, had a specific gravity of 2.78, a liquid limit of 36.1%, a plastic limit of 16.3%, a plasticity index of 19.8%, an optimum moisture content of 15.35%, and a maximum dry density of 1900 kg / m³. 3 The specific surface area is 25422.89 cm². -1 .

[0026] 2) The fly ash is grade F low-calcium fly ash, with a silica content of 45.10%, an alumina content of 36.80%, and a density of 2.10 g / cm³. 3 The specific surface area is 22467.56 cm². -1 .

[0027] 3) The blast furnace slag is grade S95, with an activity index of 98.30%, a silica content of 34.20%, a calcium oxide content of 34.00%, an alumina content of 17.60%, and a density of 3.10 g / cm³. 3 The specific surface area is 23519.75 cm². -1 .

[0028] (2) Boil deionized water and cool it to 60°C for use in preparing the alkaline activation solution. Weigh the required amount of water for the experiment into a 2L plastic beaker, and then dissolve sodium silicate powder and sodium hydroxide crystals in the beaker sequentially. Seal the prepared alkaline activation solution with plastic wrap and let it cool at room temperature for 24 hours. The SiO2:Na2O molar ratio of the alkaline activation solution is 1.2M.

[0029] 1) The solid sodium hydroxide crystals are block crystals with a purity of 98.5%.

[0030] 2) The solid sodium silicate powder is a white powder with a SiO2:Na2O molar ratio of 3.3M.

[0031] (3) Weigh out the ultrafine iron tailings, fly ash and blast furnace slag required for the test, and place them in a mixing pot and mix them evenly.

[0032] (4) Add the alkali activator solution to the mixing pot and stir manually for 1 minute. Then, stir for 3 minutes using a standard cement mortar mixer to obtain the mixture. The 3 minutes of stirring is equivalent to 2 minutes of low-speed stirring at 60 r / min and 1 minute of high-speed stirring at 80 r / min.

[0033] (5) Stir the mixture after stirring in step (4) manually for 30 seconds until it is evenly distributed, and you will get fresh ultrafine iron tailings geopolymer cementitious material. Pour the fresh ultrafine iron tailings geopolymer cementitious material into a mold and compact it in a standard vibrator for 1 minute. Then let it stand at room temperature for 24 hours before demolding.

[0034] (6) The hardened ultrafine iron tailings base polymer cementitious material was placed in a standard curing box and cured for 6 days at a curing temperature of 60℃ and a curing humidity of 98%RH.

[0035] Examples 6-12 A polymer cementitious material based on ultrafine iron tailings comprises the following raw material components in parts by weight: 360 parts ultrafine iron tailings, 80-160 parts fly ash, 80-160 parts blast furnace slag, 27.15 parts sodium hydroxide, and 64.05 parts sodium silicate. When using, add 252 parts water. Specific implementation ratios are shown in Table 2.

[0036] Table 2. Cementitious material components and parts by weight in Examples 6-12

[0037] The method of using the above-mentioned ultrafine iron tailings base polymer cementitious material includes the following steps: (1) Place the ultrafine iron tailings, fly ash and blast furnace slag in a forced-air drying oven at 105±2℃ and dry them to constant weight. After cooling to room temperature, test their particle size distribution with a laser particle size analyzer. 1) The ultrafine iron tailings contained 33.15% silica, had a specific gravity of 2.78, a liquid limit of 36.1%, a plastic limit of 16.3%, a plasticity index of 19.8%, an optimum moisture content of 15.35%, and a maximum dry density of 1900 kg / m³. 3 The specific surface area is 25422.89 cm². -1 .

[0038] 2) The fly ash is grade F low-calcium fly ash, with a silica content of 45.10%, an alumina content of 36.80%, and a density of 2.10 g / cm³. 3 The specific surface area is 22467.56 cm². -1 .

[0039] 3) The blast furnace slag is grade S95, with an activity index of 98.30%, a silica content of 34.20%, a calcium oxide content of 34.00%, an alumina content of 17.60%, and a density of 3.10 g / cm³. 3 The specific surface area is 23519.75 cm². -1 .

[0040] (2) Boil deionized water and cool it to 60°C for use in preparing the alkaline activation solution. Weigh the required amount of water for the experiment into a 2L plastic beaker, and then dissolve sodium silicate powder and sodium hydroxide crystals in the beaker sequentially. Seal the prepared alkaline activation solution with plastic wrap and let it cool at room temperature for 24 hours. The SiO2:Na2O molar ratio of the alkaline activation solution is 1.4M.

[0041] 1) The solid sodium hydroxide crystals are block crystals with a purity of 98.5%.

[0042] 2) The solid sodium silicate powder is a white powder with a SiO2:Na2O molar ratio of 3.3M.

[0043] (3) Weigh out the ultrafine iron tailings, fly ash and blast furnace slag required for the test, and place them in a mixing pot and mix them evenly; (4) Add the alkali activator solution to the mixing pot and stir manually for 1 minute. Then, stir for 3 minutes using a standard cement mortar mixer to obtain the mixture. The 3 minutes of stirring is 2 minutes of low-speed stirring at 60 r / min and 1 minute of high-speed stirring at 100 r / min.

[0044] (5) Stir the mixture after stirring in step (4) manually for 30 seconds until it is evenly distributed, and you will get fresh ultrafine iron tailings geopolymer cementitious material. Pour the fresh ultrafine iron tailings geopolymer cementitious material into a mold and compact it in a standard vibrator for 1 minute. Then let it stand at room temperature for 24 hours before demolding.

[0045] (6) The hardened ultrafine iron tailings base polymer cementitious material was placed in a standard curing box and cured for 6 days at a curing temperature of 60℃ and a curing humidity of 98%RH.

[0046] The particle size distribution of ultrafine iron tailings, fly ash, and blast furnace slag was tested according to JC / T 721-2006 "Determination of Particle Size Distribution in Cement - Laser Method". The consistency, fresh apparent density, bulk density, longitudinal wave velocity, compressive strength, splitting tensile strength, and flexural strength of the ultrafine iron tailings-based polymer cementitious material were tested according to Chinese standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and American standard ASTM C597-22 "Standard Test Method for Ultrasonic Pulse Velocity of Concrete". The results are as follows: Figures 1-9 As shown.

[0047] 1. The particle size distribution results indicate that the D of the ultrafine iron tailings... 50 The particle size was 3.626 μm, and the average particle size was 4.441 μm; the D of fly ash 50 The particle size was 4.101 μm, and the average particle size was 6.589 μm; the D of blast furnace slag 50The particle size was 4.541 μm, with an average particle size of 4.736 μm. All three solid wastes exhibited ultrafine particle sizes and large specific surface areas, making the internal aluminosilicate glassy matrix more easily dissolved by the alkaline activator, resulting in a rapid release rate of active SiO2 and Al2O3. In the alkaline activation system, the ultrafine particle size facilitated the dissolution of [SiO4]. 4- and [AlO4] 5- Improved dissolution synchronicity reduces C / NASH gel network formation time by 50%, promoting early strength development. Furthermore, it possesses the potential to fill geopolymer gel pores and provide nucleation sites for unreacted or incompletely reacted ultrafine particles, resulting in a denser structure.

[0048] 2. The experimental results from Examples 1-12 show that a significant increase in the proportion of blast furnace slag reduces the consistency of the ultrafine iron tailings-based polymer cementitious material, while significantly increasing its fresh apparent density, bulk density, longitudinal wave velocity, compressive strength, splitting tensile strength, and flexural strength. Blast furnace slag contains a large amount of highly reactive CaO, which accelerates the initial alkali-activated reaction. Under alkaline activation, it preferentially forms calcium-based gel (CASH), greatly improving early strength. Furthermore, blast furnace slag also contains 17% active Al₂O₃, which increases the [AlO₄] content in the gel network. 5- The increased proportion of mineral powder strengthens the silicon-oxygen-aluminum-oxygen tetrahedral framework, further enhancing strength and making the structure denser. Furthermore, the Ca(OH)₂ component in the blast furnace slag maintains an alkaline environment for the reaction (pH>13), and its higher heat of hydration increases the reaction temperature of the gel system, continuously activating the dissolution of silicon and aluminum in fly ash / iron tailings, thus shortening the polymerization reaction completion time. Finally, the CASH gel generated from the blast furnace slag encapsulates ultrafine iron tailings particles (containing a large amount of Fe₂O₃), possessing the potential to form a "gel-iron phase" interface reinforcement layer. Therefore, the increase in mineral powder is beneficial to improving the physical and mechanical properties of ultrafine iron tailings-based polymer cementitious materials, which enhances structural stability and reliability, laying a solid foundation for its long-term application in engineering.

[0049] 3. The experimental results of Examples 4-5 show that a significant increase in the proportion of fly ash increases the consistency of the ultrafine iron tailings-based polymer cementitious material, while significantly reducing the fresh apparent density, bulk density, longitudinal wave velocity, compressive strength, splitting tensile strength, and flexural strength. Under low alkali content conditions, in the ternary solid waste system, when the ratio of fly ash to blast furnace slag exceeds 1:1, the calcium-silicon ratio (Ca / Si) of the system decreases significantly, leading to dilution of the mineral powder and a substantial reduction in CASH gel formation, which is detrimental to early strength development. Generally, the angular surfaces of blast furnace slag and ultrafine iron tailings increase the system density due to the interlocking effect between particles, but at the cost of fluidity. Fly ash, on the other hand, is mostly spherical with a smooth surface, playing a significant "ball bearing" role in the system and effectively improving fluidity. However, excessive fly ash also reduces the interlocking effect between particles, increases porosity, and results in a loose structure. Finally, the inert quartz phase (α-SiO2) in fly ash requires a high concentration of OH... - While the activator dissolves, excessive fly ash leads to its ineffective consumption in the activation of the inert phase, reducing activation efficiency. Therefore, the alkali content was further increased to enhance the performance of the ultrafine iron tailings-based polymer cementitious material, as described in Examples 6-12.

[0050] The results above show that the physical and mechanical properties of the ultrafine iron tailings geopolymer cementitious material provided by this invention are significantly improved with increasing blast furnace slag content. However, the physical and mechanical properties of the ultrafine iron tailings geopolymer cementitious material decrease significantly with increasing fly ash content. High-strength geopolymer materials can be used to produce eco-friendly concrete materials, building curtain wall blocks, etc. Low-strength geopolymer materials can be used as mine backfill materials and road base materials. Classifying and grading the use of ultrafine iron tailings geopolymer cementitious materials can efficiently utilize ultrafine iron tailings, fly ash, and blast furnace slag, resulting in significant environmental benefits. Furthermore, compared with cement-based materials, the production cost of the ternary solid waste-based material provided by this invention is significantly reduced, possessing the potential for large-scale promotion and opening up new avenues in the field of solid waste utilization.

Claims

1. An ultrafine iron tailings geopolymer cementitious material, characterised in that, The application relates to a superfine iron tailings-based polymer cementing material, which comprises the following components in parts by weight: superfine iron tailings 10-500 parts, fly ash 10-600 parts, blast furnace slag 10-600 parts, sodium hydroxide 10-50 parts and sodium silicate 10-100 parts.

2. The ultrafine iron tailings geopolymer cementitious material according to claim 1, wherein, The superfine iron tailings have 25-40% of silica content, 2.6-2.8 of specific gravity, 30-40% of liquid limit, 15-17% of plastic limit, 18-20% of plasticity index, 14-16% of optimum water content and 1500kg / m 3 ~2000kg / m 3 of maximum dry density, and 23000cm -1 ~26000cm -1 of specific surface area.

3. The ultrafine iron tailings geopolymer cementitious material of claim 1, wherein, The fly ash is F-grade low-calcium fly ash, the content of silicon dioxide is 40%-50%, the content of aluminum oxide is 30%-40%; the density of the fly ash is 2.0-2.5g / cm 3 , the specific surface area is 20000cm -1 2-23000cm -1 .

4. The ultrafine iron tailings geopolymer cementitious material of claim 1, wherein, The blast furnace slag is S95 grade, the activity index is above 95%, the content of silicon dioxide is 30%-40%, the content of calcium oxide is 30%-40%, and the content of aluminum oxide is 15%-20%; the density of the blast furnace slag is 3.0g / cm 3 -3.5g / cm 3 The specific surface area is 22000cm -1 25000cm -1 .

5. The ultrafine iron tailings geopolymer cementitious material of claim 1, wherein, The sodium silicate is white powder, and the molar ratio of SiO2:Na2O is 3.0M-3.5M.

6. The use of ultrafine iron tailings geopolymer cementitious material according to any one of claims 1 to 5, wherein the use is in a cementitious material. The application further relates to a preparation method of the superfine iron tailings-based polymer cementing material. (1) drying superfine iron tailings, fly ash and blast furnace slag, and testing the particle size distribution by using a laser particle size analyzer; (2) boiling deionized water, cooling to 50-60 DEG C, dissolving sodium silicate and sodium hydroxide in the deionized water, and obtaining an alkali-activated solution after cooling; the molar ratio of SiO2:Na2O in the alkali-activated solution is 1.2M-1.4M; (3) weighing superfine iron tailings, fly ash and blast furnace slag, stirring and mixing uniformly, then adding the alkali-activated solution in step (2), stirring manually for 1-2 minutes, stirring by using a cement mortar standard stirring machine, first stirring at 50-60 r / min for 2-3 minutes, then stirring at 80-100 r / min for 1-2 minutes, and stirring manually for 30-60 seconds until the mixture is uniformly distributed, so that fresh superfine iron tailings-based polymer cementing material is obtained; pouring the fresh superfine iron tailings-based polymer cementing material into a mold, vibrating the mold in a standard vibrating machine for 1-2 minutes, and demolding after being statically placed at room temperature for 24-48 hours; (4) placing the hardened superfine iron tailings-based polymer cementing material in a standard curing box for curing for 6-7 days, and the curing temperature is 60-70 DEG C and the curing humidity is 90-98 RH.

7. Application of the superfine iron tailings-based polymer cementing material in mine filling materials, ecological concrete materials, road base materials and building curtain wall block materials according to any one of claims 1-5. ​

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