High-doping-amount fine-fraction iron tailing-based cementing material as well as preparation method and application of high-doping-amount fine-fraction iron tailing-based cementing material

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a high-doping-amount fine-fraction iron tailing-based cementing material as well as a preparation method and application thereof. The high-doping-amount fine-fraction iron tailing-based cementing material comprises the following components: iron tailing active powder, an alkali activator, high-calcium silicon-aluminum solid waste, a sulfate activator and an ion complexing regulating agent, in the cementing material system, the molar ratio of calcium oxide to silicon dioxide is 1.0-3.0, the molar ratio of aluminum oxide to calcium oxide is 0.01-0.3, the molar ratio of sulfur trioxide to calcium oxide is 0.1-3.0, and the molar ratio of iron trioxide to calcium oxide is 0.06-0.15. Through multi-component coordinated regulation and ion complexing optimization, the mixing amount of the fine-fraction iron tailings exceeds 40%, meanwhile, it is guaranteed that the cementing material has excellent early-stage and later-stage strength, the utilization rate of iron-phase-containing silicon-aluminum solid waste is increased, and the environmental pressure is reduced.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-content fine-grained iron tailings-based cementitious material, its preparation method, and its application. Background Technology

[0002] As a major steel producer and iron ore consumer, my country generates a massive amount of iron tailings annually. Statistics show that the total stockpile of metal tailings nationwide exceeds 23.5 billion tons, of which iron tailings account for over 70%, with an annual production of approximately 1.4 billion tons. These iron tailings are typically disposed of through open-pit storage or tailings ponds, which not only consume vast amounts of land resources but also, due to the heavy metal ions and residual beneficiation reagents they contain, can cause long-term pollution to surrounding water bodies, soil, and the atmosphere through wind erosion and leaching, posing serious environmental safety hazards and incurring high environmental remediation costs.

[0003] Furthermore, with the increasing scarcity of high-grade mineral resources, grinding and beneficiation processes are constantly being improved to enhance mineral processing recovery rates, leading to a year-on-year increase in the proportion of fine-grained tailings (D50 < 75 μm) in tailings. Although these fine-grained iron tailings are rich in SiO2, they generally exist in crystalline form (such as quartz and feldspar), making activation difficult. Currently, the utilization of fine-grained iron tailings in building materials is mostly limited to low-dosage auxiliary admixtures, and research focuses primarily on SiO2 and Al2O3 content, neglecting the role of Fe2O3 in the cementing system. The disclosed alkali-salt composite activated low-carbon hydraulic cementitious materials only consider the influence of Si and Al in siliceous aluminate solid waste, failing to address the effect of iron content on the hydration system, thus limiting the high-value utilization of iron tailings.

[0004] Therefore, developing a cementitious material that can achieve high utilization of fine-grained iron tailings while taking into account both performance and environmental protection has become an urgent technical problem to be solved in this field.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] To address the problems of high activation difficulty, low admixture content, and neglect of iron content in existing technologies for fine-grained iron tailings, this invention provides a high-admixture fine-grained iron tailings-based cementitious material, its preparation method, and its applications. Through multi-component synergistic regulation and ion complexation optimization, an admixture content exceeding 40% (controlled by Fe2O3 / CaO) is achieved, while simultaneously ensuring excellent early and late-stage strength of the cementitious material. This improves the utilization rate of iron-containing siliceous aluminous solid waste and reduces environmental impact.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high-dosage fine-grained iron tailings-based cementitious material comprises the following components: iron tailings active powder, alkali activator, high-calcium silicate solid waste, sulfate activator, and ion complexing regulator; in the cementitious material system, the molar ratio of calcium oxide to silicon dioxide is 1.0~3.0, the molar ratio of aluminum oxide to calcium oxide is 0.01~0.3, the molar ratio of sulfur trioxide to calcium oxide is 0.1~3.0, and the molar ratio of ferric oxide to calcium oxide is 0.06~0.15.

[0008] Furthermore, the 28-day activity index of the iron tailings active powder is 60%~90%, and its chemical composition includes 18~22wt% ferric oxide, 2~5wt% calcium oxide, 65~80wt% silicon dioxide, 3~10wt% aluminum oxide, 3~8wt% magnesium oxide, and 0~1wt% sulfur trioxide; the specific surface area of ​​the iron tailings active powder is 300~980m². 2 / kg.

[0009] Furthermore, the alkali activator is selected from one or more combinations of cement clinker, carbide slag, steel slag, and red mud; The 28-day activity index of the high-calcium silica-alumina solid waste is 90%~120%, wherein the calcium oxide content is ≥40wt%, the aluminum oxide content is ≥15wt%, and the silicon dioxide content is ≥20wt%; the specific surface area of ​​the high-calcium silica-alumina solid waste is ≥400m². 2 / kg.

[0010] Furthermore, the sulfate activator is selected from one or more combinations of titanium gypsum, anhydrite, phosphogypsum, and desulfurized gypsum; the specific surface area of ​​the sulfate activator is 300~500 m². 2 / kg.

[0011] Furthermore, the ion complexing regulator is selected from one or more combinations of sodium citrate, sodium gluconate, and EDTA; the amount of the ion complexing regulator added is 0.01 to 5 wt% of the total mass of the cementitious material.

[0012] In addition, the present invention also provides a method for preparing a high-content fine-grained iron tailings-based cementitious material as described above, comprising the following steps: S1. Raw material pretreatment: Drying fine-grained iron tailings and high-calcium silicate solid waste, and low-temperature drying of sulfate activator; S2. Mechanical activation: The pretreated fine-grained iron tailings are mechanically ground and activated to obtain active iron tailings powder. S3. According to the set oxide molar ratio, the iron tailings active powder, alkali activator, pretreated high-calcium silicate solid waste, sulfate activator and ion complexing regulator are mixed evenly to obtain the high-dosage fine-grained iron tailings-based cementitious material.

[0013] Further, in step S1, the drying temperature of the fine-grained iron tailings and high-calcium silicate solid waste is 100~110℃, and the drying time is 20~28h; the drying temperature of the sulfate activator is 55~65℃, and the drying time is 20~28h.

[0014] Further, in step S2, the mechanical grinding activation is performed using an experimental mill with a capacity of 5 kg and a ball-to-material mass ratio of (3~5):1; the mechanical grinding activation speed is 40~55 r / min and the grinding time is 10~90 min.

[0015] Furthermore, in step S3, the mixing is carried out using a mortar mixer, first at a low speed of 62±5 r / min for 30s, and then at a high speed of 125±10 r / min for 30s.

[0016] In addition, the present invention also provides an application of the high-dosage fine-grained iron tailings-based cementitious material as described above in the preparation of building mortar. When preparing building mortar, the mass ratio of water to cementitious material is (0.4~0.6):1, and the mass ratio of sand to cementitious material is (2~4):1. The sand is Chinese ISO standard sand or other sand conforming to ISO standards, and the preparation process complies with the requirements of GB / T 17671-2021 standard.

[0017] Compared with the prior art, the technical solution of the present invention has at least the following technical effects: (1) The present invention uses alkali activator and sulfate activator in combination to activate fine-grained iron tailings and high-calcium silicate solid waste. By adjusting the CaO / SiO2 ratio, Al2O3 / CaO ratio and SO3 / CaO, a spontaneously driven chemical environment is created for the hydration of the cementation system, which promotes the generation of hydration products.

[0018] (2) By precisely controlling the Fe2O3 / CaO ratio, the present invention allows the iron phase, which is traditionally considered inert, to participate in the hydration reaction, forming iron-containing ettringite and a more compact iron-containing gel phase. The slow formation of iron-containing ettringite leaves enough space for the formation of gel, effectively solving the problems of rapid ettringite formation rate in the current sulfate system leading to excessively rapid coagulation of cementitious materials, poor volume stability, and low strength in the later stage. At the same time, it realizes the high-quality utilization of fine-grained tailings.

[0019] (3) The introduction of ion complexation regulators accelerates ion migration (the ion complexation regulators act as "carriers" of metal ions, which accelerates the migration of ions in the liquid phase and avoids the aggregation of hydration products), optimizes the spatial distribution of hydration products, and forms a three-dimensional reinforced structure of C-(A)-SH gel, ettringite and iron-containing interlocking, which significantly improves the early and late performance of the material. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein: Figure 1 The fine-grained iron tailings used in this invention are ground to a specific surface area of ​​345 m². 2 / kg, 625m 2 / kg and 965m 2 XRD pattern per kg. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0022] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0023] According to a first aspect of the present invention, a high-dosage fine-grained iron tailings-based cementitious material is provided, comprising the following components: iron tailings active powder, alkali activator, high-calcium silicate solid waste, sulfate activator, and ion complexing regulator; in the cementitious material system, the molar ratio of calcium oxide to silicon dioxide is 1.0~3.0, the molar ratio of aluminum oxide to calcium oxide is 0.01~0.3, the molar ratio of sulfur trioxide to calcium oxide is 0.1~3.0, and the molar ratio of ferric oxide to calcium oxide is 0.06~0.15.

[0024] The core of the high-dosage fine-grained iron tailings-based cementitious material of this invention achieves the orderly generation and microstructure optimization of hydration products by controlling the ratios of CaO / SiO2, Al2O3 / CaO, SO3 / CaO, and Fe2O3 / CaO. The active iron tailings powder used in this invention mainly serves as a source of SiO2, Al2O3, and Fe2O3. The alkali activator mainly provides an alkaline environment, and the sulfate activator mainly serves as a source of SO3. In addition, since the activity of fine-grained iron tailings is low, although mechanical grinding is performed, the content of soluble SiO2 and Al2O3 is limited and insufficient to support the hydration of the cementitious system. Therefore, high-calcium silicate solid waste is added as an additional source of CaO, SiO2, and Al2O3 to promote the hydration of the cementitious system. This invention first utilizes mechanical ball milling to enhance the surface activity of tailings. Then, by adjusting the composition (CaO, SiO2, Al2O3, SO3, Fe2O3), the proportions of active iron tailings powder, alkali activator, high-calcium silicate-alumina solid waste, and sulfate activator are optimized to achieve controllable regulation of the hydration product formation rate. This promotes the orderly growth of C-(A)-SH gel and ettringite crystals, improving the flexural / compressive strength of the fine-grained iron tailings-based cementitious material. Furthermore, an ion complexation regulator acts as an ion migration accelerator, modifying the hydration product formation pathway and optimizing the spatial distribution of hydration products, further enhancing the density of the cementitious material. This achieves high-value and high-quality utilization of fine-grained iron tailings.

[0025] The relevant mechanisms for regulating the proportion of core oxides are as follows: Fe 3+ With Al 3+ Ions with similar radii readily undergo isomorphic substitution to form solid solutions, such as Fe. 3+ It can partially replace Al in ettringite (AFt) 3+ This process forms iron-containing ettringite ((Fe,Al)-AFt). The formation rate of iron-containing ettringite is slower than that of pure aluminum ettringite, which delays early expansion and provides time and space for the formation of C-(A)-SH gel. Therefore, by controlling the Fe2O3 / CaO ratio, the Fe content can be controlled. 3+ The ratio of ettringite to gel affects the early hydration rate and the later microstructure stability.

[0026] Alkali activators are responsible for providing the alkaline environment required for hydration. Excessive alkalinity leads to the decomposition of ettringite and the formation of unstable high-Ca / Si gels, while insufficient alkalinity results in the loss of ions necessary for hydration, causing delays or cessation of hydration. Sulfate activators, on the other hand, are responsible for providing SO42-. 2- Al dissolved under alkaline activator 3+ Ca 2+ The reaction produces ettringite and simultaneously promotes the formation of C-(A)-SH. The chelating agent, through complexation of Ca in the liquid phase... 2+ Fe3+ Al 3+ Metal ions extend the ion migration path and promote the uniform nucleation of hydration products over a wider range.

[0027] CaO / SiO2 directly controls the Ca / Si ratio of C-(A)-SH gel. A low Ca / Si ratio promotes the formation of highly polymerized calcium silicate gel, improving later-stage strength and durability. Al2O3 / CaO regulates the relative content of ettringite and gel. Appropriately increasing Al2O3 / CaO can increase the amount of ettringite, but excessively high Al2O3 / CaO can lead to early expansion. It needs to be controlled in conjunction with SO3 / CaO. SO3 / CaO controls the sulfate activation intensity and the amount of ettringite formed. High SO3 / CaO will promote ettringite formation, but may lead to delayed expansion. Therefore, further regulation of Fe2O3 / CaO can alleviate the problem of poor system performance due to later-stage expansion. Fe2O3 / CaO regulates the degree and form of iron phase participation in hydration, controlling the Fe... 3+ The ratio of ettringite to gel affects the early hydration rate and the later microstructure stability.

[0028] In this invention, the amount of fine-grained iron tailings is precisely controlled by adjusting the Fe2O3 / CaO molar ratio. There is no need to limit the specific amount of tailings; the supply of CaO can be adjusted according to the actual Fe2O3 content in the active iron tailings powder to maintain the ratio range, thus achieving a technical effect of over 40% content.

[0029] Based on the above scheme, as a preferred embodiment, the iron tailings active powder has an activity index of 60%~90% after 28 days, contains 18~22% Fe2O3, 2~5% CaO, 65~80% SiO2, 3~10% Al2O3, 3~8% MgO, 0~1% SO3, and has a specific surface area of ​​300~980m². 2 / kg. The alkali activator is one or more of cement clinker, carbide slag, steel slag, and red mud. Cement clinker and / or carbide slag are preferred. The high-calcium silicate solid waste has an activity index of 90%~120% after 28 days, CaO content ≥40%, Al2O3 content ≥15%, SiO2 content ≥20%, and specific surface area ≥400m². 2 / kg. Water slag is preferred. The sulfate activator is one or more of titanium gypsum, anhydrite, phosphogypsum, and desulfurized gypsum, with a specific surface area of ​​300~500 m². 2 / kg. Desulfurized gypsum is preferred. The ion complexing regulator is one or more of sodium citrate, sodium gluconate, and EDTA (ethylenediaminetetraacetic acid); the ion complexing regulator, through its complexation effect with ions, not only helps to improve the chemical activation efficiency but also optimizes the formation pathway of hydration products. EDTA is preferred. Optionally, the amount of the ion complexing regulator added is 0.01–5 wt% of the total mass of the cementitious material.

[0030] According to a second aspect of the present invention, a method for preparing a high-content fine-grained iron tailings-based cementitious material as described above is provided, comprising the following steps: S1. Raw material pretreatment: Fine-grained iron tailings and high-calcium silicate solid waste are dried at 100~110℃ for 20~28h, and sulfate activator is dried at 55~65℃ for 20~28h. S2. Mechanical activation: The pretreated fine-grained iron tailings are ground using an experimental mill with a ball-to-material ratio of (3~5):1, a rotation speed of 40~55 r / min, and a grinding time of 10~90 min to obtain iron tailings activated powder with the target specific surface area. S3. Mixing: Weigh each raw material according to the set oxide molar ratio, mix them using a mortar mixer, first mix at a low speed of 62±5r / min for 30s, then mix at a high speed of 125±10r / min for 30s.

[0031] According to a third aspect of the present invention, an application of a high-dosage fine-grained iron tailings-based cementitious material as described above is provided, the cementitious material being used to prepare building mortar, wherein the mass ratio of water to cementitious material is (0.4~0.6):1, the mass ratio of sand to cementitious material is (2~4):1, the sand is Chinese ISO standard sand or other sand conforming to ISO standards, and the preparation process follows the GB / T17671-2021 standard.

[0032] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0033] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0034] Example 1 (1) Fine-grained iron tailings and water slag (high-calcium silicate aluminum solid waste) were placed in an oven and dried for 24 hours at a temperature of 105°C to obtain dried fine-grained iron tailings and water slag; desulfurized gypsum (sulfate activator) was placed in an oven and dried for 24 hours at a temperature of 60°C to obtain dried desulfurized gypsum containing 2 molecules of water of crystallization for later use. (2) The dried fine-grained iron tailings, slag and desulfurized gypsum were ground for 3 min, 40 min and 8 min respectively to obtain a specific surface area of ​​345 m². 2 Iron tailings active powder, mineral powder and desulfurized gypsum powder at concentrations of 430 m² / kg and 300 m² / kg are available for use. (3) Weigh iron tailings active powder, cement clinker, water slag, desulfurization gypsum and EDTA (ion complexing regulator, the amount added accounts for 0.2wt% of the cementitious system) according to the following ratios: CaO / SiO2 ratio 2.71, Al2O3 / CaO ratio 0.10, SO3 / CaO ratio 0.12 and Fe2O3 / CaO ratio 0.09. Mix them evenly in a mortar mixer to obtain cementitious material. (4) Mortar preparation and performance testing: The mortar was prepared according to GB / T 17671-2021 with a water to cementitious material mass ratio of 0.5:1 and a standard sand to cementitious material mass ratio of 3:1. After standard curing for 1 day, the mortar was demolded and cured for another 3 days, 7 days and 28 days. The compressive strength was then tested.

[0035] Example 2 The remaining steps and parameters are the same as in Example 1, with the only difference being: The component ratios were adjusted to: CaO / SiO2 ratio 2.49, Al2O3 / CaO ratio 0.11, SO3 / CaO ratio 0.12, and Fe2O3 / CaO ratio 0.09. Example 3 The remaining steps and parameters are the same as in Example 1, with the only difference being: The component ratios were adjusted to: CaO / SiO2 ratio 3.0, Al2O3 / CaO ratio 0.08, SO3 / CaO ratio 0.14, and Fe2O3 / CaO ratio 0.13. Example 4 The remaining steps and parameters are the same as in Example 1, with the only difference being: The fine-grained iron tailings were ground for 30 minutes, yielding a specific surface area of ​​625 m². 2 / kg of active iron tailings powder.

[0036] Example 5 The remaining steps and parameters are the same as in Example 2, with the only difference being: The fine-grained iron tailings were ground for 30 minutes, yielding a specific surface area of ​​625 m².2 / kg of active iron tailings powder.

[0037] Example 6 The remaining steps and parameters are the same as in Example 3, with the only difference being: The fine-grained iron tailings were ground for 30 minutes, yielding a specific surface area of ​​625 m². 2 / kg of active iron tailings powder.

[0038] Example 7 The remaining steps and parameters are the same as in Example 1, with the only difference being: The fine-grained iron tailings were ground for 90 minutes, yielding a specific surface area of ​​965 m². 2 / kg of active iron tailings powder.

[0039] Example 8 The remaining steps and parameters are the same as in Example 2, with the only difference being: The fine-grained iron tailings were ground for 90 minutes, yielding a specific surface area of ​​965 m². 2 / kg of active iron tailings powder.

[0040] Example 9 The remaining steps and parameters are the same as in Example 3, with the only difference being: The fine-grained iron tailings were ground for 90 minutes, yielding a specific surface area of ​​965 m². 2 / kg of active iron tailings powder.

[0041] Example 10 The remaining steps and parameters are the same as in Example 1, with the only difference being: In step (2), the fine-grained iron tailings were ground for 90 minutes, resulting in a specific surface area of ​​965 m². 2 / kg of active iron tailings powder. The ion complexing regulator added in step (3) is sodium citrate (the amount added accounts for 0.2wt% of the gelling system).

[0042] Comparative Example 1 The remaining steps and parameters are the same as in Example 1, with the only difference being: No ion complexing regulator is added in step (3).

[0043] Comparative Example 2 The remaining steps and parameters are the same as in Example 2, with the only difference being: No ion complexing regulator is added in step (3).

[0044] Comparative Example 3 The remaining steps and parameters are the same as in Example 3, with the only difference being: No ion complexing regulator is added in step (3).

[0045] Comparative Example 4 The remaining steps and parameters are the same as in Example 4, with the only difference being: No ion complexing regulator is added in step (3).

[0046] Comparative Example 5 The remaining steps and parameters are the same as in Example 5, with the only difference being: No ion complexing regulator is added in step (3).

[0047] Comparative Example 6 The remaining steps and parameters are the same as in Example 6, with the only difference being: No ion complexing regulator is added in step (3).

[0048] Comparative Example 7 The remaining steps and parameters are the same as in Example 7, with the only difference being: No ion complexing regulator is added in step (3).

[0049] Comparative Example 8 The remaining steps and parameters are the same as in Example 8, with the only difference being: No ion complexing regulator is added in step (3).

[0050] Comparative Example 9 The remaining steps and parameters are the same as in Example 9, with the only difference being: No ion complexing regulator is added in step (3).

[0051] Comparative Example 10 Commercially available P·O 42.5 grade ordinary Portland cement was used; the CaO / SiO2 ratio, Al2O3 / CaO ratio, SO3 / CaO ratio, and Fe2O3 / CaO ratio in the cement were 2.6, 0.06, 0.03, and 0.045, respectively.

[0052] Comparative Example 11 The remaining steps and parameters are the same as in Example 1, with the only difference being: Fine-grained iron tailings powder was converted into quartz powder of the same fineness; the CaO / SiO2 ratio, Al2O3 / CaO ratio, SO3 / CaO ratio, and Fe2O3 / CaO ratio of the cementation system were 2.71, 0.10, 0.12, and 0, respectively.

[0053] Comparative Example 12 The remaining steps and parameters are the same as in Example 1, with the only difference being: No cement clinker is added in step (3); the CaO / SiO2 ratio, Al2O3 / CaO ratio, SO3 / CaO ratio and Fe2O3 / CaO ratio of the cementitious system are 1.91, 0.17, 0.14 and 0.11, respectively.

[0054] Comparative Example 13 The remaining steps and parameters are the same as in Example 1, with the only difference being: No gypsum is added in step (3); the CaO / SiO2 ratio, Al2O3 / CaO ratio, SO3 / CaO ratio and Fe2O3 / CaO ratio of the gelling system are 2.17, 0.12, 0 and 0.09, respectively.

[0055] Comparative Example 14 The remaining steps and parameters are the same as in Example 1, with the only difference being: The CaO / SiO2 ratio, Al2O3 / CaO ratio, SO3 / CaO ratio, and Fe2O3 / CaO ratio of the gelling system are 3.31, 0.07, 0.15, and 0.16, respectively.

[0056] Test Example 1. The mechanical properties of the cementitious materials of Examples 1-10 and Comparative Examples 1-11 were tested according to GB / T17671-2021 Cement Mortar Strength Test Method. The results are shown in Table 1 below.

[0057] Table 1 Results of Mechanical Property Tests This invention, through systematically controlling the key proportions of CaO / SiO2, Al2O3 / CaO, SO3 / CaO, and Fe2O3 / CaO in the cementitious system, and synergistically employing mechanical activation and chemical excitation technologies, successfully achieved high utilization of fine-grained iron tailings (>40%) and a significant improvement in the mechanical properties of the cementitious materials. Data from Table 1 shows that the introduction of ion complexing regulators and the increase in the specific surface area of ​​iron tailings significantly improved the early and late strength of all embodiments, with the highest 28-day compressive strength reaching 42.5 MPa, showing a very small difference from the performance of commercially available P·O 42.5 grade cement (46.0 MPa). The strength results of Comparative Example 11 and Example 1 clearly demonstrate the positive role of the iron phase in the system. Meanwhile, the results of Example 3, Comparative Example 3, and Comparative Example 14 show that the increase in Fe2O3 / CaO hindered strength development, as Fe2O3 mainly comes from iron tailings. Therefore, it is necessary to rationally control the iron tailings content to achieve a balance between high iron tailings content and performance. Furthermore, the significant decrease in strength in Comparative Examples 13 and 14 highlights the synergistic effect of alkali-sulfate activation, achieving a synergistic effect far greater than the sum of its parts. The mechanical property results demonstrate that, with an iron tailings content exceeding 40%, synergistic regulation can fully yield cementitious materials that meet engineering application requirements, achieving efficient resource utilization of iron tailings and providing a new perspective for the utilization of iron-containing solid waste.

[0058] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any technical solutions obtained by means of equivalent substitution or equivalent transformation should be covered within the protection scope of the present invention.

Claims

1. A high-content fine-grained iron tailings-based cementitious material, characterized in that, The material comprises the following components: iron tailings activated powder, alkali activator, high-calcium silicate solid waste, sulfate activator, and ion complexing regulator; in the cementitious material system, the molar ratio of calcium oxide to silicon dioxide is 1.0~3.0, the molar ratio of aluminum oxide to calcium oxide is 0.01~0.3, the molar ratio of sulfur trioxide to calcium oxide is 0.1~3.0, and the molar ratio of ferric oxide to calcium oxide is 0.06~0.

15.

2. The high-content fine-grained iron tailings-based cementitious material according to claim 1, characterized in that, The 28-day activity index of the iron tailings active powder is 60%~90%, and its chemical composition includes 18~22wt% ferric oxide, 2~5wt% calcium oxide, 65~80wt% silicon dioxide, 3~10wt% aluminum oxide, 3~8wt% magnesium oxide, and 0~1wt% sulfur trioxide; the specific surface area of ​​the iron tailings active powder is 300~980m². 2 / kg.

3. The high-content fine-grained iron tailings-based cementitious material according to claim 1, characterized in that, The alkali activator is selected from one or more combinations of cement clinker, carbide slag, steel slag and red mud; The 28-day activity index of the high-calcium silica-alumina solid waste is 90%~120%, wherein the calcium oxide content is ≥40wt%, the aluminum oxide content is ≥15wt%, and the silicon dioxide content is ≥20wt%; the specific surface area of ​​the high-calcium silica-alumina solid waste is ≥400m². 2 / kg.

4. The high-content fine-grained iron tailings-based cementitious material according to claim 1, characterized in that, The sulfate activator is selected from one or more combinations of titanium gypsum, anhydrite, phosphogypsum, and desulfurized gypsum; the specific surface area of ​​the sulfate activator is 300~500 m². 2 / kg.

5. The high-content fine-grained iron tailings-based cementitious material according to claim 1, characterized in that, The ion complexing regulator is selected from one or more combinations of sodium citrate, sodium gluconate, and EDTA; the amount of the ion complexing regulator added is 0.01 to 5 wt% of the total mass of the cementitious material.

6. A method for preparing a high-content fine-grained iron tailings-based cementitious material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Raw material pretreatment: Drying fine-grained iron tailings and high-calcium silicate solid waste, and low-temperature drying of sulfate activator; S2. Mechanical activation: The pretreated fine-grained iron tailings are mechanically ground and activated to obtain active iron tailings powder. S3. According to the set oxide molar ratio, the iron tailings active powder, alkali activator, pretreated high-calcium silicate solid waste, sulfate activator and ion complexing regulator are mixed evenly to obtain the high-dosage fine-grained iron tailings-based cementitious material.

7. The preparation method according to claim 6, characterized in that, In step S1, the drying temperature of the fine-grained iron tailings and the high-calcium silicate solid waste is 100~110℃, and the drying time is 20~28h; the drying temperature of the sulfate activator is 55~65℃, and the drying time is 20~28h.

8. The preparation method according to claim 6, characterized in that, In step S2, the mechanical grinding activation is performed using an experimental mill with a capacity of 5 kg and a ball-to-material mass ratio of (3~5):1; the mechanical grinding activation speed is 40~55 r / min and the grinding time is 10~90 min.

9. The preparation method according to claim 6, characterized in that, In step S3, the mixture is mixed using a mortar mixer. First, it is mixed at a low speed of 62±5 r / min for 30 s, and then at a high speed of 125±10 r / min for 30 s.

10. The application of a high-content fine-grained iron tailings-based cementitious material as described in any one of claims 1-5 in the preparation of building mortar, characterized in that, When preparing building mortar, the mass ratio of water to cementitious material is (0.4~0.6):1, and the mass ratio of sand to cementitious material is (2~4):

1. The sand is Chinese ISO standard sand or other sand materials that conform to ISO standards, and the preparation process meets the requirements of GB / T 17671-2021 standard.

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