A fast-hardening early-strength durable ternary geopolymer engineering material and a preparation method thereof

Abstract

The application discloses a kind of fast hard early strength durable ternary geopolymer engineering materials and preparation method, the ternary geopolymer engineering materials includes solid raw material and alkali activator solution;The solid raw material is by superfine iron tailings, granulated blast furnace slag and semi-water desulfurization gypsum;The alkali activator solution is by sodium water glass solution, sodium hydroxide and water mixing formation;The ternary geopolymer engineering materials is not incorporated under the premise of any other cementitious material namely realizes fast hard early strength, wherein initial setting time is not higher than 30min, 1d, 3d and 28d compressive strength respectively exceeds 35MPa, 50MP and 73MPa.The application is not incorporated under the premise of any other cementitious material, by the scientific proportioning between three kinds of solid waste and the optimization of process parameters, can give full play to alkali-sulfur excitation synergistic effect, so that the ternary geopolymer engineering materials realizes fast hard early strength on the basis, with good durability, can be used for engineering repair scene.

Description

Technical Field

[0001] This invention belongs to the field of engineering materials technology, and in particular relates to a fast-hardening, early-strength, and durable ternary geopolymer engineering material and its preparation method. Background Technology

[0002] With the rapid development of infrastructure construction in my country, the scale of industrial and civil infrastructure such as roads, bridges, and housing is constantly expanding. Due to the combined effects of the material's inherent properties and the external environment, these facilities may develop defects such as potholes, cracks, and holes during service. If not repaired in time, these defects may affect structural safety and service life. Sulfoaluminate cement, a common type of special cement, rapidly generates a large number of needle-like ettringite crystals through the hydration reaction of anhydrous calcium sulfoaluminate and gypsum, forming a dense framework. This allows for early setting and high strength, with rapid-hardening sulfoaluminate cement being particularly outstanding in terms of rapid hardening and early strength. GB / T 20472-2006, "Sulfoaluminate Cement," classifies rapid-hardening sulfoaluminate cement into four grades based on 3-day compressive strength. Even the lowest strength grade, 42.5 (3-day compressive strength ≥ 42.5 MPa), requires a 1-day compressive strength ≥ 30.0 MPa and an initial setting time ≤ 25 minutes. The rapid-hardening and early-strength characteristics of rapid-hardening sulfoaluminate cement make it suitable for repairing defects in the aforementioned facilities.

[0003] While rapid-hardening sulfoaluminate cement meets engineering material requirements in terms of mechanical properties, it still has shortcomings in long-term durability and economic and environmental benefits. From a durability perspective, sulfoaluminate cement materials are prone to strength reduction in the later stages and have weak resistance to chemical attack. From an economic and environmental perspective, these materials rely on natural mineral resources, and the preparation process involves high-temperature calcination, resulting in high costs and carbon emissions. In contrast, geopolymers, due to their unique three-dimensional aluminosilicate network structure, have stable chemical properties and better long-term durability. Moreover, their main raw materials are industrial solid wastes such as fly ash and slag, rather than natural resources, and the preparation process does not require high-temperature calcination, thus reducing material costs while realizing the resource utilization of solid waste, resulting in significant economic and environmental benefits. Traditional geopolymer preparation often uses a single alkali-activated system. By drawing on the hardening mechanism of sulfoaluminate cement, a small amount of ettringite can be generated by introducing sulfate solid wastes such as gypsum. This synergistic alkali-sulfur activation method can further enhance the mechanical and durability properties of geopolymer products.

[0004] Chinese patent CN114702288B discloses a low-shrinkage engineering repair material and its preparation method. This scheme constructs a quaternary composite system comprising rapid-hardening sulfoaluminate cement, emulsified asphalt, waterborne epoxy resin, and organic nano-montmorillonite. Although this technology utilizes the toughening effect of organic components and the water absorption and release effect of montmorillonite to achieve good mechanical properties and volume stability of the material, it suffers from problems such as a complex raw material system and cumbersome preparation process. The core component, organic montmorillonite, cannot be used directly and requires a series of complex chemical pretreatment processes, including heating intercalation, solid-liquid separation, repeated washing, drying, and grinding. Furthermore, the montmorillonite slurry needs to undergo ultrasonic dispersion treatment for 30 to 40 minutes before final mixing. The preparation process also requires the addition of various additives such as water-reducing agents, defoamers, and retarders, making the operation cumbersome and costly. This not only significantly increases material and time costs but also makes it difficult to meet the needs of practical repair projects for ease of construction.

[0005] Chinese patent CN115385622B discloses a solid waste road repair material and its preparation method. This material utilizes waste incineration fly ash, recycled building powder, steel slag powder, and waste mask fibers to replace part of the cement and aggregate, and introduces nano-silica for modification. While this technology significantly improves the utilization rate of solid waste and effectively avoids environmental pollution and secondary carbon emissions, its mechanical properties are generally poor. Experimental data shows that its 28-day compressive strength is only around 30 MPa at most. Furthermore, this patent is limited to short-term mechanical performance testing from 3 to 28 days, lacking verification of early 1-day and longer-term mechanical properties, as well as key durability properties such as frost resistance and impermeability. Its reliability in actual complex service environments still needs further evaluation. Summary of the Invention

[0006] Based on the above-mentioned technical problems, this invention provides a fast-hardening, early-strength, and durable ternary geopolymer engineering material and its preparation method. Using ultrafine iron tailings, granulated blast furnace slag, and hemihydrate desulfurized gypsum as the main solid raw materials, and sodium silicate solution and sodium hydroxide as alkaline activators, without adding any other cementing materials, the scientific ratio of the three solid wastes and the optimization of process parameters can fully leverage the synergistic effect of alkali-sulfur activation. This allows the ternary geopolymer engineering material to achieve fast hardening and early strength while simultaneously improving its durability, meeting the long-term stability requirements for engineering repair applications.

[0007] This invention proposes a fast-hardening, early-strength, and durable ternary geopolymer engineering material and its preparation method, comprising solid raw materials and an alkaline activator solution;

[0008] The solid raw materials include ultrafine iron tailings, granulated blast furnace slag, and hemihydrate desulfurization gypsum; the alkali activator solution is formed by mixing sodium silicate solution, sodium hydroxide, and water.

[0009] The sum of the SiO2 and Al2O3 contents in the ultrafine iron tailings is ≥60%, and in the ultrafine iron tailings and granulated blast furnace slag, 2.5 > [SiO2] / [Al2O3] > 2.3, where [SiO2] is the total content percentage of SiO2 in the ultrafine iron tailings and granulated blast furnace slag, and [Al2O3] is the total content percentage of Al2O3 in the ultrafine iron tailings and granulated blast furnace slag.

[0010] In this invention, in ultrafine iron tailings and granulated blast furnace slag, 2.5 > [SiO2] / [Al2O3] > 2.3; because if [SiO2] / [Al2O3] is too high, it will result in a lack of [Al(OH)4]. - The setting and hardening time is significantly prolonged, and the drying shrinkage in the later stage is large. If the [SiO2] / [Al2O3] ratio is too low, the reaction will be too fast, making actual construction difficult. It is also easy to generate a porous zeolite-like crystalline phase, and its mechanical properties are far inferior to those of gel products such as C-(A)-SH (hydrated calcium silicate), which have a three-dimensional network structure. The strength is prone to shrinkage in the later stage.

[0011] Preferably, by weight, the solid raw materials include: 45-54 parts of ultrafine iron tailings, 45-50 parts of granulated blast furnace slag, and 1-5 parts of hemihydrate desulfurized gypsum.

[0012] Preferably, the water-to-solid ratio of the alkaline activator solution is 0.24-0.28, and the modulus is 0.9-1.1, where the modulus is the molar ratio of SiO2 to Na2O in the solution.

[0013] Preferably, the mass of Na2O in the alkali activator is 8-12% of the mass of the solid raw material.

[0014] Preferably, the median particle size d of the ultrafine iron tailings is... 50 Particles smaller than 35 μm and with a particle size of less than 600 μm account for more than 99% of the total particle volume.

[0015] Preferably, the chemical composition of the ultrafine iron tailings, by mass percentage, is: SiO2 45-50%, Al2O3 15-20%, Fe2O3 15-20%, MgO 5-10%, Na2O 0-5%, CaO 0-5%; the remainder being SO3, K2O, etc.

[0016] Preferably, the granulated blast furnace slag is S95 grade slag powder with an activity index ≥95% after 28 days and a specific surface area ≥400m² / kg.

[0017] Preferably, the chemical composition of the granulated blast furnace slag, by mass percentage, is: CaO 35-40%, SiO2 25-30%, Al2O3 15-20%, MgO 10-15%, TiO2 0-5%, Fe2O3 0-5%, MnO 0-1%; the remainder being SO3, K2O, etc.

[0018] Preferably, the chemical composition of the hemihydrate desulfurized gypsum, by mass percentage, is: SO3 50-60%, CaO 30-40%, SiO2 0-5%, Al2O3 0-5%, Fe2O3 0-5%, CO2 0-10%, K2O 0-1%; the remainder being NiO, MnO, etc.

[0019] This invention also proposes a method for preparing the above-mentioned fast-hardening, early-strength, and durable ternary geopolymer engineering material, comprising the following steps:

[0020] S1. Mix water, sodium silicate solution and sodium hydroxide and stir to dissolve to obtain an alkaline activator solution;

[0021] S2. Mix ultrafine iron tailings, granulated blast furnace slag and semi-hydrated desulfurization gypsum evenly, then add alkali activator solution and stir thoroughly to obtain the ternary geopolymer engineering material.

[0022] This invention also proposes the application of the above-mentioned fast-hardening, early-strength, and durable ternary geopolymer engineering material in engineering repair.

[0023] The beneficial effects of this invention are:

[0024] (1) This invention uses three industrial solid wastes—ultrafine iron tailings, granulated blast furnace slag, and hemihydrate desulfurized gypsum—as basic raw materials and employs alkali-sulfur synergistic activation technology to prepare a fast-hardening, early-strength, and durable ternary geopolymer engineering material. Through the scientific proportioning of the three raw materials and the optimization of reaction parameters such as water-solid ratio, alkali activator modulus, and alkali equivalent, the synergistic effect among the three raw materials can be maximized, solving the problem of low strength and slow setting faced by ultrafine iron tailings-based geopolymers. On the basis of achieving fast hardening and early strength, it ensures excellent long-term compressive strength and durability. Taking Example 1 as an example, the initial setting time of the geopolymer engineering material described in this invention is only about 26 minutes, and the compressive strength at 1 day and 90 days exceeds 40 and 90 MPa, respectively; after 100 freeze-thaw cycles, the compressive strength loss does not exceed 30%, and the mass loss is within 2%; the impermeability performance is also good, and according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete", the water permeability resistance level can reach P11; the chloride ion penetration resistance is good, and according to JGJ / T 193-2009 "Standard for Testing and Evaluation of Durability of Concrete", it can reach Q-V level.

[0025] (2) The strength of the ternary geopolymer engineering material described in this invention comes from the synergistic complementarity among the three solid wastes: ultrafine iron tailings, as the main raw material, forms silicon-oxygen and aluminum-oxygen tetrahedra after dissolution and recombination, which are the skeleton of the geopolymer products; granulated blast furnace slag can supplement the system with active silicon-aluminum-calcium to promote the formation of gel products such as hydrated calcium silicate (aluminate) (C-(A)-SH) and hydrated sodium aluminosilicate (NASH), and improve the setting time and compressive strength of the material; the Ca provided by hemihydrate desulfurization gypsum 2+ and SO4 2- This facilitates the formation of ettringite (AFt), which, by filling pores and compensating for drying shrinkage, imparts good volume stability and durability to the material. The reaction mechanism can be summarized as follows:

[0026] 1) Dissolving the raw materials:

[0027] SiO2 + OH - + H2O → [H3SiO4] -

[0028] Al2O3 + 2OH - + 3H₂O → 2[Al(OH)₄] -

[0029] CaSO4·0.5H2O → Ca 2+ + SO4 2- + 0.5H2O

[0030] 2) Formation of C-(A)-SH and NASH in an alkaline-activated system:

[0031] [H3SiO4] - + [Al(OH)4] - + Ca 2+ → C-(A)-SH

[0032] [H3SiO4] - + [Al(OH)4] - + Na + → NASH + OH - + H2O

[0033] 3) Formation of ettringite in a sulfate-activated system:

[0034] 2[Al(OH)4] - + 6Ca 2+ + 3SO4 2- + 4OH -+ 26H2O → Ca6Al2(SO4)3(OH) 12 ·26H2O

[0035] (3) Based on the above effects, the present invention provides a fast-hardening, early-strength, durable ternary geopolymer engineering material. While realizing the high-value resource utilization of the three industrial solid wastes, the material achieves good early strength and long-term durability performance through the self-regulating synergistic effect between components. It also has the advantages of low carbon emissions, low energy consumption, and low cost, and has good engineering application prospects. It can be used in engineering repair scenarios. Attached Figure Description

[0036] Figure 1 The particle size distribution diagrams of the ultrafine iron tailings, granulated blast furnace slag, and hemihydrate desulfurization gypsum described in the embodiments and comparative examples of the present invention are shown below.

[0037] Figure 2 The XRD patterns of the ultrafine iron tailings, granulated blast furnace slag and hemihydrate desulfurization gypsum described in the embodiments and comparative examples of the present invention are shown below.

[0038] Figure 3 The strength change and mass loss rate of the geopolymer engineering material described in Example 1 of this invention after undergoing different numbers of freeze-thaw cycles;

[0039] Figure 4 This is a graph showing the relationship between current and time in a chloride ion permeation test of the geopolymer engineering material described in Example 1 of the present invention. Detailed Implementation

[0040] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0041] The specific chemical composition, particle size distribution, and mineral composition of the ultrafine iron tailings, granulated blast furnace slag, and hemihydrate desulfurization gypsum involved in the following examples and comparative examples are shown in Tables 1-3 below. Figure 1 and Figure 2 As shown:

[0042] The ultrafine iron tailings used in the following examples and comparative examples were obtained from a mineral processing plant in Ma'anshan City, Anhui Province. After the collected tailings slurry was allowed to settle and the supernatant was removed, the bottom solids were collected and air-dried to obtain the ultrafine iron tailings that meet the requirements of this invention; Table 1, Figure 1 and Figure 2 Its chemical composition, particle size distribution, and mineral composition are shown respectively.

[0043] Table 1 Chemical composition of ultrafine iron tailings

[0044]

[0045] As shown in Table 1 above, the main components of this ultrafine iron tailings are SiO2 and Al2O3, with contents of 48.73% and 16.98% respectively, and their total content is >60%, which helps to form a dense three-dimensional network structure; Figure 1 The particle size distribution diagram shows that the median particle size (d) of this ultrafine iron tailings is... 50 The particle size is approximately 35 μm, and the maximum particle size is approximately 600 μm; Figure 2 The XRD pattern shows that its main mineral composition is quartz, albite and hematite.

[0046] Granulated blast furnace slag is a byproduct of the blast furnace ironmaking process. The granulated blast furnace slag used in the following examples and comparative examples is S95 grade slag, sourced from a steel plant in Ma'anshan City, Anhui Province. (Table 2) Figure 1 and Figure 2 Its chemical composition, particle size distribution, and mineral composition are shown respectively.

[0047] Table 2 Chemical composition of granulated blast furnace slag

[0048]

[0049] As shown in Table 2 above, the main chemical composition of this granulated blast furnace slag includes: 38.51% CaO, 28.41% SiO2, 15.30% Al2O3, and 12.07% MgO; Figure 1 The particle size distribution diagram shows that the median particle size (d) of this granulated blast furnace slag is... 50 Approximately 8μm; by Figure 2 The XRD pattern shows that the granulated blast furnace slag has a typical glassy structure (amorphous bulges) and contains a small amount of dicalcium silicate (C2S) crystalline phase.

[0050] The hemihydrate desulfurization gypsum used in the following examples and comparative examples came from an environmental protection technology company in Yantai City, Shandong Province. Table 3. Figure 1 and Figure 2 Its chemical composition, particle size distribution, and mineral composition are shown respectively.

[0051] Table 3 Chemical composition of hemihydrate desulfurized gypsum

[0052]

[0053] As shown in Table 3 above, this hemihydrate desulfurization gypsum contains abundant SO3 and CaO; Figure 1 The particle size distribution diagram shows that the median particle size (d) of this hemihydrate desulfurization gypsum is... 50 Approximately 12 μm; by Figure 2 The XRD pattern shows that its mineral composition is mainly hemihydrate gypsum.

[0054] Example 1

[0055] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, comprising solid raw materials and an alkaline activator solution;

[0056] The solid raw material consists of 50 parts of ultrafine iron tailings, 45 parts of granulated blast furnace slag, and 5 parts of hemihydrate desulfurization gypsum; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder, and deionized water, and the addition amounts of the three components meet the following requirements: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0057] The preparation method of the above-mentioned fast-hardening, early-strength, and durable ternary geopolymer engineering materials includes:

[0058] (1) Mix water, sodium silicate solution and sodium hydroxide and stir to dissolve to obtain an alkaline activator solution;

[0059] (2) Mix the ultrafine iron tailings, granulated blast furnace slag and semi-water desulfurization gypsum evenly, then add the alkali activator solution and stir evenly to obtain the ternary geopolymer engineering material.

[0060] Example 2

[0061] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the water-to-solid ratio of the alkali activator solution is 0.24.

[0062] Example 3

[0063] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the water-to-solid ratio of the alkali activator solution is 0.28.

[0064] Example 4

[0065] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the alkali activator modulus of the alkali activator solution is 0.9.

[0066] Example 5

[0067] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the alkali activator modulus of the alkali activator solution is 1.1.

[0068] Example 6

[0069] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the alkali equivalent of the alkali activator solution is 8%.

[0070] Example 7

[0071] A fast-hardening, early-strength, and durable ternary geopolymer engineering material, the raw material composition and preparation method of which are the same as in Example 1, except that the alkali equivalent of the alkali activator solution is 12%.

[0072] Comparative Example 1

[0073] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0074] The solid raw material is composed of 100 parts of ultrafine iron tailings; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder and deionized water, and the addition of the three components satisfies the following: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0075] Comparative Example 2

[0076] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0077] The solid raw material consists of 75 parts of ultrafine iron tailings and 25 parts of granulated blast furnace slag; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder, and deionized water, and the addition amounts of the three components meet the following requirements: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0078] Comparative Example 3

[0079] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0080] The solid raw material consists of 55 parts of ultrafine iron tailings and 45 parts of granulated blast furnace slag; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder and deionized water, and the addition of the three components satisfies the following: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0081] Comparative Example 4

[0082] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0083] The solid raw material is composed of 45 parts of ultrafine iron tailings, 45 parts of granulated blast furnace slag, and 10 parts of hemihydrate desulfurization gypsum; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder, and deionized water, and the addition amounts of the three components meet the following requirements: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0084] Comparative Example 5

[0085] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0086] The solid raw material consists of 10 parts of ultrafine iron tailings, 85 parts of granulated blast furnace slag, and 5 parts of hemihydrate desulfurization gypsum; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder, and deionized water, and the addition amounts of the three components meet the following requirements: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0087] Comparative Example 6

[0088] A geopolymer engineering material, comprising a solid raw material and an alkaline activator solution;

[0089] The solid raw material consists of 80 parts of ultrafine iron tailings, 15 parts of granulated blast furnace slag, and 5 parts of hemihydrate desulfurization gypsum; the alkali activator solution is formed by mixing sodium silicate solution with a modulus of 2.3, solid sodium hydroxide powder, and deionized water, and the addition amounts of the three components meet the following requirements: water-to-solid ratio of 0.26, alkali activator modulus of 1.0, and alkali equivalent of 10%, that is, the mass of Na2O in the alkali activator is 10% of the mass of the solid raw material.

[0090] The setting time of the ternary geopolymer engineering materials described in the above embodiments was measured, and the results are shown in Table 4 below:

[0091] Table 4. Setting time of the geopolymer engineering materials described in each embodiment.

[0092]

[0093] The compressive strength of the geopolymer engineering materials described in the examples and comparative examples was tested, and the results are as follows (among which, comparative examples 4 and 5 set too quickly; the initial setting and final setting times of comparative example 4 were approximately 9 min and 19 min, respectively, and the initial setting and final setting times of comparative example 5 were approximately 8 min and 15 min, respectively, making them impractical and therefore their strength cannot be given):

[0094] Table 5. Compressive strength of the geopolymer engineering materials described in each embodiment and comparative example at different ages.

[0095]

[0096] As shown in Tables 4 and 5 above, the setting time of the geopolymer engineering materials described in the examples and comparative examples was tested: the initial setting time was approximately 25 minutes, and the final setting time was approximately 35 minutes, indicating a relatively fast setting time. In addition, Table 5 shows that the compressive strength of most examples can reach approximately 40 MPa in 1 day, indicating that the material has a prominent fast-hardening and early-strength properties.

[0097] Analysis of Examples 1, 2 and 3 shows that as the water-to-solid ratio increases from 0.24 to 0.28, the compressive strength decreases. This is because a higher water-to-solid ratio means that the proportion of solid components in the same space is reduced, and instead, unreacted free water is used. After this water evaporates, it forms pores, leading to a decrease in strength.

[0098] Analysis of Examples 1, 4, and 5 shows that as the modulus increases from 0.9 to 1.1, the compressive strength first increases and then decreases. This is because the Si-O bond energy is greater than that of the Al-O bond, and less active silicon is dissolved in the early stage of the reaction. Appropriately increasing the modulus can replenish the silicon component, which is beneficial to the geopolymerization reaction. However, an excessively high modulus means more sodium silicate and higher viscosity, which hinders the dissolution of raw materials and the evaporation of excess water in the system, thus leading to a decrease in strength.

[0099] Analysis of Examples 1, 6, and 7 shows that as the alkali equivalent increases from 8% to 12%, the 1-day, 3-day, and 28-day compressive strengths of the geopolymer show a decreasing trend. This is because a higher alkali equivalent causes the gel structure to form faster in the early stage of the reaction, covering the surface of unreacted raw materials and hindering the continued dissolution of silica and aluminum, resulting in insufficient active silica and aluminum in the early stage. However, the 56-day and 90-day compressive strengths show a trend of first increasing and then decreasing. This is because a lower alkali equivalent leads to insufficient C-(A)-SH in the later stage, while a higher alkali equivalent causes excess alkali to not participate in the geopolymerization reaction and to precipitate out with the migration of free water in the system. It reacts with substances such as CO2 in the air to form carbonates, resulting in surface weathering and causing a loss of compressive strength.

[0100] Analysis of Comparative Example 1 and Example 1 shows that when preparing geopolymers from ultrafine iron tailings alone, the compressive strength at different ages is relatively low. This is because the main silica-alumina components of ultrafine iron tailings—quartz, albite, etc.—are inert minerals, making it difficult to dissolve active silica-alumina and form a large amount of three-dimensional network gel. This is due to… Figure 2 The XRD pattern of the ultrafine iron tailings also shows this.

[0101] Analysis of Comparative Examples 2, 3, and 1 shows that the addition of granulated blast furnace slag has a significant effect on improving the strength of the ultrafine iron tailings-based polymer. This is due to the dual effects of the change in gel product composition and the densification of the structure brought about by the highly active components in the granulated slag. The introduction of granulated slag provides easily soluble silica-alumina monomers and a large amount of active calcium, promoting the transformation of the reaction product from NASH gel as the main component to a coexistence of NASH and C-(A)-SH. The C-(A)-SH gel has higher strength. In addition, the highly dense C-(A)-SH gel can also significantly reduce the porosity of the system by filling the network pores and encapsulating unreacted ultrafine iron tailings particles, thereby achieving both microstructural densification and a leap in macroscopic compressive strength.

[0102] Analysis of Comparative Examples 1, 4, and 1 shows that adding an appropriate amount of hemihydrate desulfurization gypsum can also improve the compressive strength of the polymer in the ultrafine iron tailings base. The further improvement in strength of the polymer in the ultrafine iron tailings base by hemihydrate desulfurization gypsum essentially stems from the supplementary effect of sulfate activation on the alkali activation system. The SO4 released from the hemihydrate desulfurization gypsum... 2- It can react with the active Ca and Al components dissolved from ultrafine iron tailings and granulated blast furnace slag to generate needle-like ettringite crystals. These crystals not only act as bridges interwoven in the network structure of alkali-activated products such as C-(A)-SH, but also effectively fill the micropores between the gel matrix and ultrafine iron tailings particles, reducing the porosity of the system and synergistically improving the compressive strength of the matrix. However, the amount of hemihydrate desulfurization gypsum added should be controlled. As shown in Comparative Example 4, when the amount of hemihydrate desulfurization gypsum added is 10%, the setting time is significantly shortened, with initial setting and final setting times of 9 min and 19 min, respectively, which no longer has working performance and cannot be practically applied. This is because excessive addition of hemihydrate desulfurization gypsum will quickly generate products such as ettringite, which will rapidly interweave into a network, lock in moisture, and cause the material to lose its fluidity, resulting in rapid setting and hardening. This "flash setting" phenomenon will hinder the polymerization of aluminosilicate gel and the further dissolution of raw materials, and is prone to cracking problems in the later stages due to excessive ettringite.

[0103] Analysis of Comparative Examples 5, 6, and 1 shows that the content of ultrafine iron tailings and granulated blast furnace slag should be controlled within a certain range. Content that is too high or too low will not achieve the rapid hardening and early strength effect described in Example 1. This is because the overall [SiO2] / [Al2O3] ratios of ultrafine iron tailings and granulated blast furnace slag in Comparative Examples 5 and 6 are 1.97 and 2.72, respectively, which are outside the range of 2.3-2.5. If the [SiO2] / [Al2O3] ratio is too high, it will result in a lack of [Al(OH)4]. -The setting and hardening time is significantly prolonged, and the drying shrinkage in the later stage is large. If the [SiO2] / [Al2O3] ratio is too low, the reaction will be too fast, making actual construction difficult. It is also easy to generate a porous zeolite-like crystalline phase, and its mechanical properties are far inferior to those of gel products such as C-(A)-SH (hydrated calcium silicate), which have a three-dimensional network structure. The strength is prone to shrinkage in the later stage.

[0104] To determine the durability of ternary geopolymer engineering materials, the main and most common durability indicators were verified, including freeze resistance, water permeability resistance and chloride ion permeability resistance.

[0105] The freeze-thaw resistance of geopolymer engineering materials is one of their key indicators. In some cold regions, some repair materials may crack and become ineffective due to insufficient freeze-thaw resistance. To reflect the freeze-thaw resistance of the ternary geopolymer engineering material described in this invention, freeze-thaw cycle tests were conducted, and the results are as follows: Figure 3 As shown in Table 6:

[0106] Table 6. Strength changes and mass loss rate after freeze-thaw cycles

[0107]

[0108] Figure 3 Tables 1 and 6 show the changes in strength and mass loss rate of the material after different numbers of freeze-thaw cycles. It can be seen that after 100 freeze-thaw cycles, the compressive strength of the ternary geopolymer engineering material described in Example 1 decreased from 81.44 MPa to 57.32 MPa, and the mass loss rate was about 1.54%. This indicates that the material has good freeze resistance and can still maintain high compressive strength under freeze-thaw conditions.

[0109] Water permeability resistance is equally important for engineering materials, reflecting their ability to resist water penetration and other environmental conditions, ensuring stable performance in long-term water-contaminated environments. This invention uses a stepwise pressurization method to determine water permeability. The results show that when the water pressure reaches 1.2 MPa, 3 out of 6 specimens of the ternary geopolymer engineering material described in Example 1 began to show signs of water seepage. The water permeability grade was calculated according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". P =10 H - 1 (where H is the water pressure (MPa) when 3 out of 6 specimens are permeable), the permeability grade of the specimens is P11, indicating that the geopolymer engineering material prepared in this study has excellent permeability resistance.

[0110] Besides freeze resistance and water penetration resistance, chloride ion penetration resistance is also an important indicator for evaluating engineering materials. Materials with good chloride ion penetration resistance can effectively block the intrusion of chloride-containing corrosive media, prevent internal steel corrosion and matrix deterioration, thereby ensuring the long-term durability of engineering materials. This invention measures chloride ion penetration resistance by applying a 60V DC voltage across the two ends of the specimen and recording the current flux through the specimen for 6 hours. The relationship between current and time is shown in the figure below. Figure 4 As shown, the total electrical flux is calculated according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete": Q x =900 ( I 0+ 2 I 30 +2 I 60 + … + 2 I t + … + 2 I 300 +2 I 330 +2 I 360 (where I) t Q represents the current value (A) at t minutes. x This represents the total electrical flux (C) passing through the specimen, and is converted to the electrical flux value for a specimen with a diameter of 95 mm. Q s = Q x (95 / ) x ) 2 (Where x represents the diameter of the specimen (mm)). The final results show that after 6 hours of testing, the electrical flux of the specimen corresponding to the ternary geopolymer engineering material described in Example 1 was approximately 213C (converted to the electrical flux value for a 95mm specimen). According to JGJ / T 193-2009 "Standard for Testing and Evaluation of Concrete Durability", Q... s At temperatures below 500°C, the chloride ion penetration resistance reaches a level of Q-V, indicating that the specimen exhibits good chloride ion penetration resistance. The results of the chloride ion penetration resistance test further reflect the strong resistance of the geopolymer engineering material described in this invention to extreme environments and its good long-term durability.

[0111] In addition to meeting short-term and long-term performance standards and exhibiting stability in extreme environments such as cold, the geopolymer engineering material described in this invention uses industrial solid waste such as ultrafine iron tailings as raw materials and does not involve high-energy-consuming processes such as high-temperature curing, resulting in lower costs, environmental friendliness, and significant environmental and economic benefits.

[0112] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A fast-hardening, early-strength, durable ternary geopolymer engineering material, characterized in that, Includes solid raw materials and alkaline activator solution; The solid raw material is composed of ultrafine iron tailings, granulated blast furnace slag and hemihydrate desulfurization gypsum; the alkaline activator solution is formed by mixing sodium silicate solution, sodium hydroxide and water. By weight, the solid raw materials include: 45-54 parts of ultrafine iron tailings, 45-50 parts of granulated blast furnace slag, and 1-5 parts of hemihydrate desulfurized gypsum. The sum of the SiO2 and Al2O3 contents in the ultrafine iron tailings is ≥60%, and in the ultrafine iron tailings and granulated blast furnace slag, 2.5 > [SiO2] / [Al2O3] > 2.3, where [SiO2] is the total content percentage of SiO2 in the ultrafine iron tailings and granulated blast furnace slag, and [Al2O3] is the total content percentage of Al2O3 in the ultrafine iron tailings and granulated blast furnace slag. The ternary geopolymer engineering material achieves rapid hardening and early strength without the addition of any other cementing materials. The initial setting time is no more than 30 minutes, and the compressive strength at 1 day, 3 days, and 28 days exceeds 35 MPa, 50 MPa, and 73 MPa, respectively.

2. The fast-hardening, early-strength, durable ternary geopolymer engineering material according to claim 1, characterized in that, The median particle size d of the ultrafine iron tailings 50 Particles with a diameter of no more than 35 μm and a particle size of less than 600 μm account for more than 99% of the total particle volume.

3. The fast-hardening, early-strength, durable ternary geopolymer engineering material according to claim 1 or 2, characterized in that, The chemical composition of the ultrafine iron tailings, by mass percentage, is: SiO2 45-50%, Al2O3 15-20%, Fe2O3 15-20%, MgO 5-10%, Na2O 0-5%, CaO 0-5%.

4. The fast-hardening, early-strength, durable ternary geopolymer engineering material according to claim 1 or 2, characterized in that, The granulated blast furnace slag is S95 grade slag powder with an activity index ≥95% after 28 days and a specific surface area ≥400 m². 2 / kg.

5. The fast-hardening, early-strength, durable ternary geopolymer engineering material according to claim 4, characterized in that, The chemical composition of the granulated blast furnace slag, by mass percentage, is: CaO 35-40%, SiO2 25-30%, Al2O3 15-20%, MgO 10-15%, TiO2 0-5%, Fe2O3 0-5%, MnO 0-1%.

6. The fast-hardening, early-strength, durable ternary geopolymer engineering material according to claim 1 or 2, characterized in that, The chemical composition of the hemihydrate desulfurized gypsum, by mass percentage, is: SO3 50-60%, CaO 30-40%, SiO2 0-5%, Al2O3 0-5%, Fe2O3 0-5%, CO2 0-10%, K2O 0-1%.

7. A method for preparing a fast-hardening, early-strength, durable ternary geopolymer engineering material according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix water, sodium silicate solution and sodium hydroxide and stir to dissolve to obtain an alkaline activator solution; S2. Mix ultrafine iron tailings, granulated blast furnace slag and semi-hydrated desulfurization gypsum evenly, then add alkali activator solution and stir thoroughly to obtain the ternary geopolymer engineering material.

8. The application of a fast-hardening, early-strength, durable ternary geopolymer engineering material according to any one of claims 1-6 in engineering repair.

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