An autothermal early-strength tailings geopolymer

Abstract

A self-heating early-strength tailings geopolymer is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with or without water; the raw materials of the geopolymer precursor powder A include high-calcium tailings, sodium hydroxide, highly reactive lime and fly ash; before mixing the raw materials of the geopolymer precursor powder A, the raw materials including high-calcium tailings, sodium hydroxide and highly reactive lime are mechanically activated; the raw materials of the geopolymer additive B include a water reducer, a thermal insulation material and sodium silicate. The strength of the geopolymer of the present invention is significantly improved, and it has high early strength. It does not require external heating for curing. The preparation process and construction method are simple. It can locally consume tailings and can replace cement with the same strength as building subgrade materials, etc., and has good economic benefits.

Description

Technical Field

[0001] The present invention relates to the fields of building materials and solid waste resource utilization, and particularly to a self-heating early-strength geopolymer for consuming tailings. Background Art

[0002] A large amount of tailings will be generated after ore beneficiation. With the continuous decrease of the grade of exploitable ore, the amount of tailings generated each year is also increasing year by year. Tailings are the waste generated after ore beneficiation or smelting processes, which contain unextracted minerals and a large amount of impurities, such as metal elements, mineral particles, chemical substances, etc. At present, the utilization rate of tailings in China is only about 30%, and a large amount of the remaining tailings are stored in tailing ponds. The large accumulation of tailings not only wastes precious land resources, but also brings serious pollution and safety hazards to the environment. The resource utilization of tailings not only helps to reduce the harm of tailings to the environment, but also can achieve the efficient reuse of waste and reduce the pressure on limited natural resources.

[0003] Geopolymer is a type of inorganic polymerized structural cementitious material formed by silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons, which was first developed by Professor J•Davidovits in France in the late 1970s. Compared with traditional silicate building materials, geopolymers have the following advantages: (1) Environmental protection advantage: Compared with the high-temperature calcination in the cement manufacturing process, its carbon emissions are smaller; (2) Crack resistance: Due to its nanoscale microstructure and excellent toughness, geopolymers can reduce the generation of cracks on the surface of buildings; (3) Corrosion resistance: It can slow down the erosion of chemical substances on building materials and enhance the durability of building materials; (4) Thermal performance advantage: Geopolymers can maintain good stability in high-temperature environments and can provide excellent thermal insulation performance in some composite materials, reducing the energy consumption of buildings. In short, geopolymers have more advantages in terms of environmental protection, physical properties, chemical properties, thermal properties and flexibility compared with traditional cement building materials, providing more innovative possibilities for the construction field and promoting the sustainable development of the construction industry.

[0004] Patent CN104844081A discloses a concrete with granite powder as the main mineral admixture. However, in this patent, granite powder only serves as an aggregate and does not participate in the reaction, and the dosage is only 5-17.5wt%, resulting in problems such as low utilization rate of stone powder, low compressive strength and added value of the product.

[0005] Although patents CN113735473A and CN113620618A solve the technical problem that solid waste can only be used as a small amount of filler, the leaching of active silicon and aluminum must be achieved by using high-temperature roasting and a variety of complex agents, and the product preparation process is complex, the overall compressive strength is low, and the high-temperature roasting cost is high and does not conform to the development trend of green and low-carbon, making it difficult to be widely promoted and applied on a large scale.

[0006] CN115849781A discloses a geopolymer based on multiple solid wastes and a preparation method thereof. Granite powder, silica fume and lime are mixed and ground and then uniformly mixed with fine-grained fly ash to obtain a precursor powder. The obtained precursor powder is uniformly mixed with an alkali activator to obtain a slurry; then it is formed and cured to obtain a geopolymer. Although this method does not require alkali thermal activation of the solid waste granite powder, only the specific surface area of the stone powder particles is increased by grinding, which provides beneficial conditions for the attachment of silica fume, thereby providing favorable conditions for the formation of silica-rich gel in the later stage. In essence, it does not change the crystallinity of the tailings to fully activate the silicon-aluminum activity in the tailings. And because the tailings geopolymer needs to be sealed and heat-treated for curing to ensure a certain compressive strength, it cannot be locally consumed when treating tailings on site. The preparation method is cumbersome and costly, which is not conducive to later industrial applications.

[0007] Thus, it can be seen that in the existing technology, when using tailings to prepare geopolymer in actual building construction, heating equipment is required to heat and cure the geopolymer, which has strict requirements for construction conditions and is difficult to achieve. Therefore, there is an urgent need to develop a method for preparing geopolymer by curing tailings at room temperature and simultaneously improving the early strength of the geopolymer. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a self-heating early-strength tailings-based geopolymer with high early strength.

[0009] The technical solution adopted by the present invention to solve its technical problems is as follows: A self-heating early-strength tailings-based geopolymer is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with or without water.

[0010] The raw materials of the geopolymer precursor powder A include high-calcium tailings, sodium hydroxide, highly reactive lime and fly ash; before mixing the raw materials of the geopolymer precursor powder A, the raw materials including high-calcium tailings, sodium hydroxide and highly reactive lime are mechanically activated together.

[0011] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material and sodium silicate.

[0012] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to highly reactive lime is 10-110:1.

[0013] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to sodium hydroxide is 20-110:1.

[0014] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is less than 4.5:1.

[0015] In the said slurry, the mass ratio of the dosage of geopolymer precursor powder A to that of geopolymer assistant B is 1 to 100:1;

[0016] The water content of the said slurry is below 40 wt%.

[0017] Preferably, the mechanical force activation adopts the high-energy ball milling method.

[0018] Preferably, the water reducing agent is one or more of polycarboxylic acid type, lignosulfonate type, and sulfamic acid type.

[0019] Preferably, the thermal insulation material is one or more of polystyrene particles, expanded perlite, and composite silicate.

[0020] Preferably, the water content of the water glass is 50 wt% - 60 wt%.

[0021] More preferably, the rotation speed of the high-energy ball milling method is above 200 rpm.

[0022] More preferably, the treatment time of the high-energy ball milling method is above 5 minutes.

[0023] Preferably, the composition of the high-calcium tailings includes: 15 wt% - 30 wt% of CaO, 20 wt% - 50 wt% of SiO2, and 5 wt% - 10 wt% of Al2O3.

[0024] Preferably, the digestion temperature of the high-reactivity lime is above 90 °C, and the digestion time is above 30 minutes.

[0025] Preferably, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to that of high-reactivity lime is 20 to 100:1.

[0026] Preferably, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to that of sodium hydroxide is 30 to 100:1.

[0027] Preferably, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to that of fly ash is below 4:1.

[0028] Preferably, the composition of the fly ash includes: 35 wt% - 50 wt% of SiO2, 15 wt% - 35 wt% of Al2O3, and 2 wt% - 10 wt% of CaO.

[0029] Preferably, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to that of fly ash is 0.8 to 3:1.

[0030] Preferably, in the geopolymer assistant B, the mass ratio of the dosage of the water reducing agent to that of the thermal insulation material is 1 to 10:1.

[0031] Preferably, in the geopolymer additive B, the mass ratio of the water reducing agent to the sodium silicate is 0.1 to 0.4:1.

[0032] Preferably, in the slurry, the mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 2 to 60:1.

[0033] Preferably, the water content of the slurry is 10 wt% to 30 wt%.

[0034] Preferably, the curing time of the slurry is 4 to 72 h.

[0035] The present invention has the following beneficial effects:

[0036] (1) The strength of the geopolymer is significantly improved: The present invention innovatively uses high-calcium tailings, sodium hydroxide, and highly reactive lime for mechanical activation together to enhance the reaction activity of the high-calcium tailings, endowing the high-calcium tailings with alkali activation activity and further forming a gel phase, significantly improving the strength of the geopolymer;

[0037] (2) The C-S-H and N-A-S-H gel phases in the geopolymer act synergistically to significantly improve the strength of the geopolymer;

[0038] (3) The geopolymer has high early strength, does not require external heating for curing, the preparation process and construction method are simple, it can locally consume tailings, and can replace cement with the same strength as building subgrade materials, etc., having good economic benefits.

[0039] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the accompanying drawings to further elaborate on the present invention in detail. Description of the Drawings

[0040] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0041] Figure 1 is the X-ray diffraction pattern of the mechanically activated high-calcium tailings in Example 1 and Example 2 of the present invention, and the high-calcium tailings treated by ordinary ball milling in Comparative Example 1;

[0042] Figure 2 is the detection result diagram of the infrared spectrum of the geopolymers obtained in Example 2 and Comparative Example 2 of the present invention. Detailed Embodiments

[0043] To make the objectives, solutions, and beneficial technologies of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. It should be noted that the embodiments described in this specification are only for explaining the present invention and not for limiting the present invention.

[0044] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recited.

[0045] In the description herein, it should be noted that unless otherwise specified, "above" and "below" include the recited number, the meaning of "multiple" in "one or more" is two or more, and the meaning of "multiple" in "one or more" is two or more.

[0046] An embodiment of the present invention provides a self-heating early-strength tailing-based geopolymer, which is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with or without water.

[0047] The raw materials of the geopolymer precursor powder A include high-calcium tailings, sodium hydroxide, highly reactive lime, and fly ash; before mixing the raw materials of the geopolymer precursor powder A, the raw materials including high-calcium tailings, sodium hydroxide, and highly reactive lime are first mechanically activated together.

[0048] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate.

[0049] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to highly reactive lime is 10 - 110:1.

[0050] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to sodium hydroxide is 20 - 110:1.

[0051] In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is below 4.5:1.

[0052] In the slurry, the mass ratio of the dosage of geopolymer precursor powder A to geopolymer additive B is 1 - 100:1.

[0053] The water content of the slurry is 40 wt% or less.

[0054] High-calcium tailings often originate from iron tailings, lead-zinc tailings, tungsten tailings, etc.; the silicon-aluminum-calcium components in high-calcium tailings mainly exist in inert minerals such as quartz, mica, and zeolites, and do not have alkali activation activity, which greatly limits their application as geopolymer raw materials. In the embodiments of the present invention, mechanical activation is performed on high-calcium tailings, sodium hydroxide, and highly reactive lime together, which can make the mixture of the three more uniform, so as to promote the highly reactive lime to uniformly provide reaction heat; after grinding, the highly reactive lime can more easily react with the active components in sodium hydroxide and high-calcium tailings to form a stronger cementitious material. This helps to improve the strength and stability of geopolymers. Sodium hydroxide can provide a strong alkaline environment during the activation process and can chemically react with the components in the tailings (such as silicon, aluminum, and calcium compounds). Under high pH conditions, these components are more likely to dissolve and recrystallize. Mechanical activation applies high-frequency impact, shear, and friction forces to the particles, which can destroy the crystal structure of the tailings, increase lattice defects and broken bonds, and even convert some crystalline substances into more reactive amorphous states. Under the synergistic effect of mechanical activation and sodium hydroxide, the stable crystalline structure in the tailings may be destroyed and partially converted into amorphous states, making the originally stable substances become thermodynamically unstable but more reactive states. The silicon-aluminum-calcium components in high-calcium tailings have alkali activation activity after being mechanically activated by the present invention. Reactive calcium silicate can promote the formation of the C-S-H gel phase, and reactive calcium silicoaluminate can promote the formation of the N-A-S-H gel phase. Under the interweaving action of the two gel networks, the strength of geopolymers can be significantly improved.

[0055] The synergistic effect of the heat release during the hydration of highly reactive lime, the heat release during the dissolution of sodium hydroxide, and the heat insulation of the heat-insulating material enhances the early strength of geopolymers. The heat released during the hydration of lime is beneficial to the continuous progress of the geopolymerization reaction and the hydration reaction, accelerating the formation of gel phases such as C-S-H and N-A-S-H and improving the early strength of the geopolymer gel material. However, it is difficult to meet the heat requirements of self-heating early-strength geopolymers only by the heat release during the hydration of lime. In the present invention, a large amount of heat is released through the hydration of highly reactive lime with a high digestion temperature and a long digestion time. The dissolution of sodium hydroxide will further release a large amount of heat to meet the temperature requirements of self-heating early-strength geopolymers. At the same time, the heat-insulating material in the heat-insulating suspension can slow down the outward heat dissipation inside, reduce the internal and external temperature exchange of the geopolymer, and thus delay the heat dissipation, further improving the early strength of the geopolymer gel material. The synergistic effect of highly reactive lime, sodium hydroxide, and the heat-insulating material can achieve the curing of geopolymers without external heating and the on-site construction and consumption of tailings.

[0056] Sodium silicate is both an alkali activator and a silicon source in geopolymers. As an alkali activator, sodium silicate promotes the dissolution of aluminosilicate raw materials and then forms geopolymer gels; the silicate in sodium silicate provides a silicon source for the geopolymer reaction, combines with aluminate to form aluminosilicate gels, and enhances the material strength.

[0057] On the one hand, the water reducer improves the fluidity and workability of the geopolymer paste by dispersing the particles and reducing the friction between the particles, facilitating pouring and shaping. On the other hand, the water reducer helps to form a denser structure and enhance the compressive and flexural strengths of the geopolymer.

[0058] The self-heating and early-strength tailings-based geopolymer provided by the embodiments of the present invention has the following advantages:

[0059] (1) The strength of the geopolymer is significantly improved: In the present invention, high-calcium tailings, sodium hydroxide, and highly reactive lime are innovatively used for mechanical activation together to enhance the reaction activity of the high-calcium tailings, endowing the high-calcium tailings with alkali activation activity and further forming a gel phase, significantly improving the strength of the geopolymer.

[0060] (2) The C-S-H and N-A-S-H gel phases in the geopolymer act synergistically to significantly improve the strength of the geopolymer.

[0061] (3) The geopolymer has high early strength, does not require external heating for curing, has simple preparation processes and construction methods, can locally consume tailings, and can replace cement with the same strength as building subgrade materials, etc., having good economic benefits.

[0062] In the embodiments of the present invention, the mechanical activation adopts the high-energy ball milling method. Common high-energy ball mills on the market can be used, such as planetary, stirring, and vibrating high-energy ball mills. Compared with ordinary ball mills, high-energy ball mills can achieve higher rotation speeds and stronger impact forces, making the collision between the grinding medium and the material more intense and applying a large amount of mechanical energy in a short time.

[0063] In the embodiments of the present invention, the water reducer is one or more of polycarboxylic acid-based, lignosulfonate-based, and aminosulfonic acid-based.

[0064] In the embodiments of the present invention, the thermal insulation material is one or more of polystyrene particles, expanded perlite, and composite silicate.

[0065] In the embodiments of the present invention, the moisture content of the water glass is 50 wt% - 60 wt%.

[0066] In some embodiments of the present invention, the rotation speed of the high-energy ball milling method is above 200 rpm. High-energy ball milling requires a relatively high rotation speed. If the rotation speed is too low, it is difficult to be called high-energy ball milling even if a high-energy ball mill is used.

[0067] In some embodiments of the present invention, the treatment time of the high-energy ball milling method is above 5 min.

[0068] In some embodiments of the present invention, the rotational speed of the high-energy ball milling method is 200 - 1000 rpm. The experimental results show that when the rotational speed is too low, the effect is similar to that of ordinary ball milling, making it difficult to promote phase transformation or amorphization on the surface of the tailings, unable to activate the activity of the silicon-aluminum-calcium minerals contained in the high-calcium tailings themselves, and also unable to achieve mechanical activation. When the rotational speed is higher than this range, phase transformation or amorphization can still occur on the surface of the tailings, activating the activity of the silicon-aluminum-calcium minerals contained in the high-calcium tailings themselves. However, too high a ball milling rotational speed requires higher energy, resulting in too high costs and wasting resources.

[0069] In some embodiments of the present invention, the treatment time of the high-energy ball milling method is 5 - 60 min. Longer high-energy ball milling treatment can still achieve phase transformation or amorphization on the surface of the tailings, activating the activity of the silicon-aluminum-calcium minerals contained in the high-calcium tailings themselves. It's just that it is unnecessary to continue with high-energy ball milling treatment after the reaction is basically completed, and it will also cause waste of resources.

[0070] In the embodiments of the present invention, the composition of the high-calcium tailings includes: CaO 15 wt% - 30 wt%, SiO2 20 wt% - 50 wt%, Al2O3 5 wt% - 10 wt%.

[0071] High-reactivity lime is a common term in the industry. Activity is an index to measure the reaction rate of quicklime and is one of the important standards for inspecting the quality of quicklime. In the embodiments of the present invention, the digestion temperature of the high-reactivity lime is above 90 °C, and the digestion time is above 30 min.

[0072] In the embodiments of the present invention, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to high-reactivity lime is 20 - 100:1.

[0073] In the embodiments of the present invention, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to sodium hydroxide is 30 - 100:1.

[0074] In the embodiments of the present invention, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is below 4:1.

[0075] In the embodiments of the present invention, the composition of the fly ash includes: SiO2 35 wt% - 50 wt%, Al2O3 15 wt% - 35 wt%, CaO 2 wt% - 10 wt%.

[0076] In the embodiments of the present invention, in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is 0.8 - 3:1.

[0077] In some embodiments of the present invention, when mixing the raw materials of the geopolymer precursor powder A, grinding mixing is adopted; common grinding mixing methods can all be used, for example: general ball milling mixing.

[0078] In an embodiment of the present invention, in the geopolymer additive B, the mass ratio of the dosage of the water reducing agent to the heat insulation material is 1 to 10:1.

[0079] In an embodiment of the present invention, in the geopolymer additive B, the mass ratio of the dosage of the water reducing agent to the water glass is 0.1 to 0.4:1.

[0080] In an embodiment of the present invention, in the slurry, the mass ratio of the dosage of the geopolymer precursor powder A to the geopolymer additive B is 2 to 60:1.

[0081] In an embodiment of the present invention, the water content of the slurry is 10 wt% to 30 wt%.

[0082] In some embodiments of the present invention, when molding, the slurry is injected into a mold for molding.

[0083] In some embodiments of the present invention, after the slurry is injected into the mold for molding, a film is covered for curing, and after demolding, curing is carried out to obtain a formed self-heating early-strength tailings-based geopolymer.

[0084] In an embodiment of the present invention, the curing time of the slurry is 4 to 72 h. The curing of the slurry can be carried out at room temperature without external heating.

[0085] Examples

[0086] The following examples more specifically describe the content disclosed in the present invention. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the present invention are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples can be obtained through conventional commercial channels or synthesized according to conventional methods and can be used directly without further treatment. Unless otherwise stated, the instruments used in the examples can be obtained through conventional commercial channels.

[0087] The water reducing agent used in each example and comparative example was purchased from Jiangsu Sobute New Materials Co., Ltd.; the heat insulation material was purchased from Hebei Shengda Thermal Insulation Building Materials Co., Ltd.; the water glass was purchased from Wuxi Yatai United Chemical Co., Ltd.; the high-calcium tailings were taken from the tailing ponds in Ezhou, Hubei and Handan, Hebei; the high-reactivity lime was purchased from Hengyang Hengxin Environmental Protection Co., Ltd., Hunan; the fly ash was purchased from Wuhan Jiyesheng Chemical Co., Ltd.

[0088] For the 7-day compressive strength test conducted in each example and comparative example, the "Standard Test Method for Physical and Mechanical Properties of Concrete" (GB / T 5008 - 2019) was adopted.

[0089] For convenient comparison and viewing, the strength test results of each example and comparative example are summarized in Table 1.

[0090] Example 1

[0091] The self-heating early-strength tailing geopolymer of this example is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with water; the mass ratio of geopolymer precursor powder A to geopolymer additive B is 40:1, and the water content of the mixed slurry is 20 wt%.

[0092] The raw materials of the geopolymer precursor powder A include (by weight): 100 parts of high-calcium tailings, 2 parts of sodium hydroxide, 5 parts of highly reactive lime, and 100 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 500 rpm and a treatment time of 20 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling.

[0093] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by mixing evenly. Among them, the mass ratio of the water reducer to the thermal insulation material is 3:1; the mass ratio of the water reducer to sodium silicate is 0.4:1.

[0094] The water reducer used in this example is a polycarboxylate water reducer.

[0095] The thermal insulation material used in this example is polystyrene particles.

[0096] The composition of the high-calcium tailings used in this example includes: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%

[0097] The digestion temperature of the highly reactive lime used in this example is 90 °C, and the digestion time is 60 min.

[0098] The composition of the fly ash used in this example includes: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0099] When the slurry is formed and cured, it is first cast and molded in a prefabricated mold, then covered with a film and cured at room temperature for 24 h, demolded and then cured at room temperature, and finally the formed self-heating early-strength tailing geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 47.25 MPa.

[0100] Example 2

[0101] The self-heating early-strength tailings geopolymer of this embodiment is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer assistant B with water; the mass ratio of geopolymer precursor powder A to geopolymer assistant B is 30:1, and the water content of the mixed slurry is 10 wt%.

[0102] The raw materials of the geopolymer precursor powder A include (by weight): 100 parts of high-calcium tailings, 2 parts of sodium hydroxide, 2.5 parts of highly active lime, and 50 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly active lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 600 rpm and a treatment time of 30 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling;

[0103] The raw materials of the geopolymer assistant B include a water reducing agent, a thermal insulation material, and sodium silicate; mixing evenly gives the geopolymer assistant B. Among them, the mass ratio of the water reducing agent to the thermal insulation material is 5:1; the mass ratio of the water reducing agent to sodium silicate is 0.1:1.

[0104] The water reducing agent used in this embodiment is a lignosulfonate water reducing agent.

[0105] The thermal insulation material used in this embodiment is expanded perlite.

[0106] The composition of the high-calcium tailings used in this embodiment includes: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%.

[0107] The digestion temperature of the highly active lime used in this embodiment is 100 °C, and the digestion time is 50 min.

[0108] The composition of the fly ash used in this embodiment includes: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0109] When the slurry is formed and cured, it is first cast and formed in a prefabricated mold, then covered with a film and cured at room temperature for 48 h, demolded and cured at room temperature, and finally the formed self-heating early-strength tailings geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 54.9 MPa.

[0110] Example 3

[0111] The self-heating early-strength tailings geopolymer of this embodiment is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer assistant B with water; the mass ratio of geopolymer precursor powder A to geopolymer assistant B is 50:1, and the water content of the mixed slurry is 30 wt%.

[0112] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 1 part of sodium hydroxide, 1 part of highly reactive lime, and 40 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 800 rpm and a treatment time of 20 min), and then all the raw materials of the geopolymer precursor powder A are uniformly mixed by ordinary ball milling;

[0113] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by uniform mixing. The mass ratio of the water reducer to the thermal insulation material is 3:1; the mass ratio of the water reducer to sodium silicate is 0.3:1.

[0114] The water reducer used in this example is a polycarboxylate water reducer.

[0115] The thermal insulation material used in this example is composite silicate.

[0116] The composition of the high-calcium tailings used in this example includes: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%.

[0117] The digestion temperature of the highly reactive lime used in this example is 120 °C, and the digestion time is 30 min.

[0118] The composition of the fly ash used in this example includes: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0119] When the slurry is formed and cured, it is first cast and formed in a precast mold, then covered with a film and cured at room temperature for 40 h, and after demolding, it is cured at room temperature, and finally, a formed self-heating early-strength tailings-based geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 57.5 MPa.

[0120] Example 4

[0121] The self-heating early-strength tailings-based geopolymer of this example is obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 30:1, and the water content of the mixed slurry is 15 wt%;

[0122] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 2 parts of sodium hydroxide, 3 parts of highly reactive lime, and 20 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 200 rpm and a treatment time of 60 min), and then all the raw materials of the geopolymer precursor powder A are uniformly mixed by ordinary ball milling;

[0123] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by uniform mixing. The mass ratio of the water reducer to the thermal insulation material is 1:1; the mass ratio of the water reducer to sodium silicate is 0.2:1.

[0124] The water reducer used in this example is an amino sulfonic acid-based water reducer.

[0125] The thermal insulation material used in this example is compound silicate.

[0126] The composition of the high-calcium tailings used in this example includes: CaO 15.22 wt%, SiO2 20.18 wt%, Al2O3 5.17 wt%.

[0127] The digestion temperature of the highly reactive lime used in this example is 110 °C, and the digestion time is 40 min.

[0128] The composition of the fly ash used in this example includes: SiO2 49.08 wt%, Al2O3 15.78 wt%, CaO 9.26 wt%.

[0129] When the slurry is formed and cured, it is first cast and molded in a prefabricated mold, then covered with a film and cured at room temperature for 4 h, demolded and cured at room temperature, and finally a formed self-heating early-strength tailings-based geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 57.7 MPa.

[0130] Example 5

[0131] The self-heating early-strength tailings-based geopolymer of this example is obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 5:1, and the water content of the mixed slurry is 25 wt%;

[0132] The raw materials of the geopolymer precursor powder A include (by weight): 100 parts of high-calcium tailings, 1 part of sodium hydroxide, 1 part of highly reactive lime, and 125 parts of fly ash. First, the raw materials including high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 1000 rpm and a treatment time of 5 minutes), and then all the raw materials of the geopolymer precursor powder A are uniformly mixed by ordinary ball milling.

[0133] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by uniform mixing. The mass ratio of the water reducer to the thermal insulation material is 10:1; the mass ratio of the water reducer to sodium silicate is 0.1:1.

[0134] The water reducer used in this example is an amino sulfonic acid-based water reducer.

[0135] The thermal insulation material used in this example is polystyrene particles.

[0136] The composition of the high-calcium tailings used in this example includes: 15.22 wt% CaO, 20.18 wt% SiO2, and 5.17 wt% Al2O3.

[0137] The digestion temperature of the highly reactive lime used in this example is 100°C, and the digestion time is 30 minutes.

[0138] The composition of the fly ash used in this example includes: 49.08 wt% SiO2, 15.78 wt% Al2O3, and 9.26 wt% CaO.

[0139] When the slurry is formed and cured, it is first cast and molded in a prefabricated mold, then covered with a film and cured at room temperature for 72 hours, demolded and cured at room temperature, and finally a formed self-heating early-strength tailings-based geopolymer is obtained. After testing, the 7-day compressive strength value of the obtained geopolymer is 56.4 MPa.

[0140] As can be seen from the above examples, the geopolymers prepared in the present invention all have good compressive strength, and the compressive strength grades are all above 42.5R, and most of them meet the 52.5R grade. It can be seen from the examples that the geopolymers of the present invention can be cured at room temperature, and the 7-day compressive strength can reach a high standard. Compared with the existing technology geopolymers that need to be cured at high temperature, the present invention has obvious advantages.

[0141] Comparative Example 1

[0142] Compared with Example 1, this comparative example uses ordinary ball milling to replace high-energy ball milling, and other processes are the same as those in Example 1. The specific situation is as follows.

[0143] The tailings geopolymer of this comparative example is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with water; the mass ratio of geopolymer precursor powder A to geopolymer additive B is 40:1, and the water content of the mixed slurry is 20 wt%.

[0144] The raw materials of the geopolymer precursor powder A include (by weight): 100 parts of high-calcium tailings, 2 parts of sodium hydroxide, 5 parts of highly reactive lime, and 100 parts of fly ash; first, grind the high-calcium tailings, sodium hydroxide, and highly reactive lime using an ordinary ball mill (rotation speed of 500 rpm, treatment time of 20 min), and then mix all the raw materials of the geopolymer precursor powder A evenly by ordinary ball milling;

[0145] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; mix evenly to obtain the geopolymer additive B. Among them, the mass ratio of the water reducer to the thermal insulation material is 3:1; the mass ratio of the water reducer to sodium silicate is 0.4:1.

[0146] The water reducer used in this comparative example is a polycarboxylate water reducer.

[0147] The thermal insulation material used in this comparative example is polystyrene particles.

[0148] The composition of the high-calcium tailings used in this comparative example includes: 29.88 wt% of CaO, 49.95 wt% of SiO2, and 9.13 wt% of Al2O3.

[0149] The digestion temperature of the highly reactive lime used in this comparative example is 90 °C, and the digestion time is 60 min.

[0150] The composition of the fly ash used in this comparative example includes: 35.23 wt% of SiO2, 30.65 wt% of Al2O3, and 2.65 wt% of CaO.

[0151] When the slurry is formed and cured, first cast and mold it in a prefabricated mold, then cover it with a film and cure it at room temperature for 24 h, perform room-temperature curing after demolding, and finally obtain the formed tailings geopolymer; after testing, the 7-day compressive strength value of the obtained geopolymer is 24.2 MPa.

[0152] The high-calcium tailings treated by the high-energy ball mill and the ordinary ball mill in Example 1, Example 2, and Comparative Example 1 were subjected to XRD testing, and the results are as Figure 1As shown, it can be found that the main mineral components in the high-calcium tailings are quartz, biotite, chlorite, gismondine, albite, etc. After the mechanical activation in Examples 1 and 2, the diffraction peak intensities of biotite, chlorite, gismondine, and albite in the high-calcium tailings are significantly weakened or even disappear compared with the tailings after ordinary ball milling in Comparative Example 1. This indicates that after mechanical activation, the high-calcium tailings are initially transformed from a crystalline state to an amorphous state.

[0153] The main differences between high-energy ball milling and ordinary ball milling lie in the machine structure design differences and output energy differences. Ordinary ball mills are usually a rotating cylinder filled with grinding media and materials to be ground, and are not specifically designed for high-energy input. Ordinary ball mills are mainly used for crushing particles, mixing materials, and homogenizing particle size distribution, and usually do not cause significant physical and chemical changes, mainly for refining particles without changing the internal structure of the material. The characteristic of high-energy ball milling is that it can achieve higher rotation speeds and more intense impact forces in design, making the collision between the grinding media and the material more violent, thus introducing more energy. In the examples of the present invention, through the rapid rotation or vibration of high-energy ball milling, a large amount of mechanical energy is applied in a short time to cooperate with sodium hydroxide to promote the transformation of the material from a crystalline state to an amorphous state.

[0154] Comparative Example 2

[0155] Compared with Example 2, this comparative example uses low-reactivity lime to replace high-reactivity lime, and other processes are the same as those in Example 2. The specific situation is as follows.

[0156] The tailings geopolymer in this comparative example is obtained by forming and curing a slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with water; the mass ratio of geopolymer precursor powder A to geopolymer additive B is 30:1, and the water content of the mixed slurry is 10 wt%.

[0157] The raw materials of the geopolymer precursor powder A include (by weight): 100 parts of high-calcium tailings, 2 parts of sodium hydroxide, 2.5 parts of low-reactivity lime, and 50 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and low-reactivity lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 600 rpm and a treatment time of 30 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling.

[0158] The raw materials of the geopolymer additive B include a water reducer, a thermal insulation material, and sodium silicate; after mixing evenly, the geopolymer additive B is obtained. The mass ratio of the water reducer to the thermal insulation material is 5:1; the mass ratio of the water reducer to sodium silicate is 0.1:1.

[0159] The water reducer used in this comparative example is a lignosulfonate water reducer.

[0160] The thermal insulation material used in this comparative example is expanded perlite.

[0161] The composition of the high-calcium tailings used in this comparative example includes: CaO 29.88 wt%, SiO₂ 49.95 wt%, Al₂O₃ 9.13 wt%.

[0162] The digestion temperature of the low-reactivity lime used in this comparative example is 60 °C, and the digestion time is 12 min.

[0163] The composition of the fly ash used in this comparative example includes: SiO₂ 35.23 wt%, Al₂O₃ 30.65 wt%, CaO 2.65 wt%.

[0164] When the slurry is formed and cured, it is first cast and molded in a prefabricated mold, then covered with a film and cured at room temperature for 48 h. After demolding, it is cured at room temperature, and finally the formed tailings geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 41.35 MPa.

[0165] The geopolymers obtained in Example 2 and Comparative Example 2 were subjected to FTIR analysis, and the results are as Figure 2 shown. High-reactivity lime was used in Example 2, and low-reactivity lime was used in Comparative Example 2; it can be seen from the figure that the shapes of the two spectra are similar, indicating that although the incorporation of high-reactivity lime relative to low-reactivity lime will affect the hydration reaction rate and compressive strength of the geopolymer, the product components are basically the same. Among them, the stretching and bending vibration peaks of -OH correspond to 3455 cm -1 and 1642 cm -1 respectively. The stretching vibration peak of C-O is near 1444 cm -1 , which may be due to the entry of CO₂ in the air into the alkaline slurry to generate CO₃ 2- . The vibration peaks corresponding to Al-O and Si-O bonds are at 561 cm -1 and 455 cm -1 respectively. The vibration peak corresponding to the Si-O-Al(Si) of the N-A-S-H gel of the geopolymer is at 1011 cm -1 . Compared with low-reactivity lime, after incorporating high-reactivity lime, the wave number at this place moves to the low wave band, indicating that the SiO₄ tetrahedron is replaced by more AlO₄ tetrahedrons, the polymerization degree of the geopolymer increases, more gel phases are produced, and the compressive strength of the geopolymer is improved. Ordinary quicklime has a low digestion temperature and a short digestion time, making it difficult to provide enough heat, and the duration is not enough to improve the strength of the geopolymer.

[0166] Comparative Example 3

[0167] Compared with Example 2, the dosage of high-reactivity lime was reduced in this comparative example (the mass ratio of high-calcium tailings to high-reactivity lime was 120:1), and other processes were the same as those in Example 2. The specific conditions are as follows.

[0168] The tailings-based geopolymer in this comparative example was obtained by molding and curing the slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with water; the mass ratio of geopolymer precursor powder A to geopolymer additive B was 30:1, and the water content of the mixed slurry was 10 wt%.

[0169] The raw materials of the geopolymer precursor powder A included (by weight): 300 parts of high-calcium tailings, 6 parts of sodium hydroxide, 2.5 parts of high-reactivity lime, and 150 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and high-reactivity lime were mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 600 rpm and a treatment time of 30 min), and then all the raw materials of the geopolymer precursor powder A were mixed evenly by ordinary ball milling.

[0170] The raw materials of the geopolymer additive B included a water reducer, a thermal insulation material, and sodium silicate; the geopolymer additive B was obtained by mixing evenly. The mass ratio of the water reducer to the thermal insulation material was 5:1; the mass ratio of the water reducer to sodium silicate was 0.1:1.

[0171] The water reducer used in this comparative example was a lignosulfonate water reducer.

[0172] The thermal insulation material used in this comparative example was expanded perlite.

[0173] The composition of the high-calcium tailings used in this comparative example included: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%.

[0174] The digestion temperature of the high-reactivity lime used in this comparative example was 100 °C, and the digestion time was 50 min.

[0175] The composition of the fly ash used in this comparative example included: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0176] When the slurry was molded and cured, it was first cast and molded in a precast mold, then covered with a film and cured at room temperature for 48 h, demolded and then cured at room temperature, and finally the formed tailings-based geopolymer was obtained; after testing, the 7-day compressive strength value of the obtained geopolymer was 39.85 MPa.

[0177] Comparative Example 4

[0178] Compared with Example 2, the dosage of highly reactive lime was increased in this comparative example (the mass ratio of high-calcium tailings to highly reactive lime was 5:1), and other processes were the same as those in Example 2. The specific situation is as follows.

[0179] The tailings geopolymer of this comparative example was obtained by molding and curing the slurry formed by mixing geopolymer precursor powder A and geopolymer additive B with water; the mass ratio of geopolymer precursor powder A to geopolymer additive B was 30:1, and the water content of the mixed slurry was 10 wt%.

[0180] The raw materials of the geopolymer precursor powder A included (by weight): 100 parts of high-calcium tailings, 2 parts of sodium hydroxide, 20 parts of highly reactive lime, and 50 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime were mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 600 rpm and a treatment time of 30 min), and then all the raw materials of the geopolymer precursor powder A were mixed evenly by ordinary ball milling;

[0181] The raw materials of the geopolymer additive B included a water reducing agent, a thermal insulation material, and sodium silicate; the geopolymer additive B was obtained by mixing evenly. Among them, the mass ratio of the water reducing agent to the thermal insulation material was 5:1; the mass ratio of the water reducing agent to sodium silicate was 0.1:1.

[0182] The water reducing agent used in this comparative example was a lignosulfonate water reducing agent.

[0183] The thermal insulation material used in this comparative example was expanded perlite.

[0184] The composition of the high-calcium tailings used in this comparative example included: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%.

[0185] The digestion temperature of the highly reactive lime used in this comparative example was 100 °C, and the digestion time was 50 min.

[0186] The composition of the fly ash used in this comparative example included: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0187] When the slurry was molded and cured, it was first cast and molded in a prefabricated mold, then covered with a film and cured at room temperature for 48 h, demolded and cured at room temperature, and finally the formed tailings geopolymer was obtained; after testing, the 7-day compressive strength value of the obtained geopolymer was 54.2 MPa.

[0188] The high-calcium tailings to highly reactive lime dosage ratios in Example 2 were compared with those in Comparative Example 3 and Comparative Example 4. It was found that the strength of the geopolymer obtained in Comparative Example 3 was relatively low. Based on the experimental phenomena, it was speculated that perhaps a relatively high high-calcium tailings to highly reactive lime dosage ratio was insufficient to generate enough heat, resulting in limited promotion of the polymerization reaction of the active calcium silicate and aluminum components in the high-calcium tailings and fly ash and the geopolymer additive B. The strength of the product obtained in Comparative Example 4 was relatively high, but a larger amount of highly reactive lime would reduce the acid resistance and chemical corrosion resistance of the geopolymer, and at the same time increase the material cost, as well as environmental problems and safety hazards.

[0189] Comparative Example 5

[0190] Compared with Example 3, in this comparative example, only the high-calcium tailings were mechanically activated, and the other processes were the same as those in Example 3. The specific situation is as follows.

[0191] The tailings-based geopolymer in this comparative example was obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A to the geopolymer additive B was 50:1, and the water content of the mixed slurry was 30 wt%.

[0192] The raw materials of the geopolymer precursor powder A included (by weight): 60 parts of high-calcium tailings, 1 part of sodium hydroxide, 1 part of highly reactive lime, and 40 parts of fly ash; first, the high-calcium tailings were mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 800 rpm and a treatment time of 20 min), and then all the raw materials of the geopolymer precursor powder A were mixed evenly by ordinary ball milling.

[0193] The raw materials of the geopolymer additive B included a water reducer, a thermal insulation material, and sodium silicate; after mixing evenly, the geopolymer additive B was obtained. Among them, the mass ratio of the water reducer to the thermal insulation material was 3:1; the mass ratio of the water reducer to sodium silicate was 0.3:1.

[0194] The water reducer used in this comparative example was a polycarboxylate water reducer.

[0195] The thermal insulation material used in this comparative example was composite silicate.

[0196] The composition of the high-calcium tailings used in this comparative example included: CaO 29.88 wt%, SiO2 49.95 wt%, Al2O3 9.13 wt%.

[0197] The digestion temperature of the highly reactive lime used in this comparative example was 120 °C, and the digestion time was 30 min.

[0198] The composition of the fly ash used in this comparative example included: SiO2 35.23 wt%, Al2O3 30.65 wt%, CaO 2.65 wt%.

[0199] When the slurry is formed and solidified, it is first cast and formed in a prefabricated mold, then covered with a film and cured at room temperature for 40 h. After demolding, it is cured at room temperature, and finally the formed tailings geopolymer is obtained. After testing, the 7-day compressive strength value of the obtained geopolymer is 37.35 MPa.

[0200] Comparative Example 6

[0201] Compared with Example 3, in this comparative example, mechanical activation was carried out separately on high-calcium tailings, sodium hydroxide, and highly reactive lime, and other processes were the same as those in Example 3. The specific situation is as follows.

[0202] The tailings geopolymer of this comparative example was obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water. The mass ratio of the geopolymer precursor powder A to the geopolymer additive B was 50:1, and the water content of the mixed slurry was 30 wt%.

[0203] The raw materials of the geopolymer precursor powder A included (by weight): 60 parts of high-calcium tailings, 1 part of sodium hydroxide, 1 part of highly reactive lime, and 40 parts of fly ash. First, the high-calcium tailings, sodium hydroxide, and highly reactive lime were separately mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 800 rpm and a treatment time of 20 min), and then all the raw materials of the geopolymer precursor powder A were mixed evenly by ordinary ball milling.

[0204] The raw materials of the geopolymer additive B included a water reducer, a thermal insulation material, and sodium silicate. The geopolymer additive B was obtained by mixing evenly. The mass ratio of the water reducer to the thermal insulation material was 3:1; the mass ratio of the water reducer to sodium silicate was 0.3:1.

[0205] The water reducer used in this comparative example was a polycarboxylate water reducer.

[0206] The thermal insulation material used in this comparative example was composite silicate.

[0207] The composition of the high-calcium tailings used in this comparative example included: 29.88 wt% of CaO, 49.95 wt% of SiO2, and 9.13 wt% of Al2O3.

[0208] The digestion temperature of the highly reactive lime used in this comparative example was 120 °C, and the digestion time was 30 min.

[0209] The composition of the fly ash used in this comparative example included: 35.23 wt% of SiO2, 30.65 wt% of Al2O3, and 2.65 wt% of CaO.

[0210] When the slurry is being formed and solidified, it is first cast in a prefabricated mold, then covered with a film and solidified at room temperature for 40 hours, and then demolded and cured at room temperature to finally obtain a formed tailings-based polymer. After testing, the 7-day compressive strength value of the obtained geopolymer is 40.5MPa.

[0211] Comparing Example 3 with Comparative Examples 5 and 6, it is found that the effects of activating high-calcium tailings alone, or activating high-calcium tailings, sodium hydroxide and high-activity lime separately are obviously inferior to the effect of grinding the three together, which shows the importance of grinding high-calcium tailings together with sodium hydroxide and high-activity lime; high-energy ball milling synergizes with sodium hydroxide to promote the formation of gels such as CSH and NASH, thereby enhancing the compressive strength of geopolymers; at the same time, the use of high-activity lime can greatly increase the heat released during the hydration process of geopolymers, and the use of sodium hydroxide dissolution to further supplement the heat is conducive to the geopolymerization reaction and hydration reaction.

[0212] Comparative Example 7

[0213] Compared with Example 3, this comparative example does not use sodium hydroxide, and other processes are consistent with Example 3, and the specific details are as follows.

[0214] The tailings-based polymer in this comparative example is obtained by forming and solidifying a slurry formed by mixing a geopolymer precursor powder A and a geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A and the geopolymer additive B is 50:1, and the water content of the mixed slurry is 30 wt%;

[0215] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 1 part of high-activity lime and 40 parts of fly ash; the high-calcium tailings and high-activity lime are first mechanically activated by high-energy ball milling (using a high-energy planetary ball mill with a rotation speed of 800 rpm and a processing time of 20 minutes), and then all the raw materials of the geopolymer precursor powder A are mixed uniformly by ordinary ball milling;

[0216] The raw materials of the geopolymer additive B include water reducing agent, thermal insulation material and water glass, which are uniformly mixed to obtain the geopolymer additive B. The mass ratio of the water reducing agent to the thermal insulation material is 3:1; the mass ratio of the water reducing agent to the water glass is 0.3:1.

[0217] The water reducing agent used in this comparative example is a polycarboxylic acid water reducing agent.

[0218] The thermal insulation material used in this comparative example is composite silicate.

[0219] The components of the high calcium tailings used in this comparative example include: CaO 29.88 wt %, SiO2 49.95 wt %, Al2O3 9.13 wt %.

[0220] The digestion temperature of the highly reactive lime used in this comparative example was 120 °C, and the digestion time was 30 min.

[0221] The composition of the fly ash used in this comparative example included: SiO2 35.23 wt%, Al2O3 30.65 wt%, and CaO 2.65 wt%.

[0222] When the slurry was formed and cured, it was first cast in a prefabricated mold, then covered with a film and cured at room temperature for 40 h. After demolding, it was cured at room temperature, and finally the formed tailings geopolymer was obtained. After testing, the 7-day compressive strength value of the obtained geopolymer was 39.5 MPa.

[0223] Comparing Example 3 with Comparative Example 7, it was found that the compressive strength of the geopolymer obtained without adding sodium hydroxide was significantly lower. It was speculated that because the high-energy ball mill ground the high-calcium tailings and sodium hydroxide powder together, it could not only make the particle size of the high-calcium tailings finer and increase the specific surface area, but also the strong alkaline environment provided by sodium hydroxide could promote the micro-reaction on the surface of the high-calcium tailings, synergistically with the high-energy ball milling to promote the transformation of the silicon, aluminum, and calcium components in the high-calcium tailings into a more reactive amorphous state. In addition, it could release heat to provide heat guarantee for the self-heating early-strength geopolymer, thereby promoting the improvement of the geopolymer strength.

[0224] Comparative Example 8

[0225] Compared with Example 4, this comparative example increased the dosage of sodium hydroxide (the mass ratio of high-calcium tailings to sodium hydroxide was 10:1), and other processes were the same as those in Example 4. The specific situation was as follows.

[0226] The tailings geopolymer of this comparative example was obtained by forming and curing the slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water. The mass ratio of the geopolymer precursor powder A to the geopolymer additive B was 30:1, and the water content of the mixed slurry was 15 wt%.

[0227] The raw materials of the geopolymer precursor powder A included (by weight): 60 parts of high-calcium tailings, 6 parts of sodium hydroxide, 3 parts of highly reactive lime, and 20 parts of fly ash. First, the high-calcium tailings, sodium hydroxide, and highly reactive lime were mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 200 rpm and a treatment time of 60 min), and then all the raw materials of the geopolymer precursor powder A were mixed evenly by ordinary ball milling.

[0228] The raw materials of the geopolymer additive B included a water reducer, a thermal insulation material, and water glass; after mixing evenly, the geopolymer additive B was obtained. The mass ratio of the water reducer to the thermal insulation material was 1:1; the mass ratio of the water reducer to water glass was 0.2:1.

[0229] The water reducer used in this comparative example was an amino sulfonic acid-based water reducer.

[0230] The thermal insulation material used in this comparative example is composite silicate.

[0231] The composition of the high-calcium tailings used in this comparative example includes: CaO 15.22 wt%, SiO2 20.18 wt%, Al2O3 5.17 wt%.

[0232] The digestion temperature of the highly reactive lime used in this comparative example is 110 °C, and the digestion time is 40 min.

[0233] The composition of the fly ash used in this comparative example includes: SiO2 49.08 wt%, Al2O3 15.78 wt%, CaO 9.26 wt%.

[0234] When the slurry is formed and cured, it is first cast in a prefabricated mold, then covered with a film and cured at room temperature for 4 h. After demolding, it is cured at room temperature, and finally the formed tailings geopolymer is obtained. After testing, the 7-day compressive strength value of the obtained geopolymer is 41.8 MPa.

[0235] Comparative Example 9

[0236] Compared with Example 4, this comparative example reduces the dosage of sodium hydroxide (the mass ratio of high-calcium tailings to sodium hydroxide is 120:1), and other processes are the same as those in Example 4. The specific situation is as follows.

[0237] The tailings geopolymer of this comparative example is obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water. The mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 30:1, and the water content of the mixed slurry is 15 wt%.

[0238] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 0.5 part of sodium hydroxide, 3 parts of highly reactive lime, and 20 parts of fly ash. First, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 200 rpm and a treatment time of 60 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling.

[0239] The raw materials of the geopolymer additive B include a water reducing agent, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by mixing evenly. Among them, the mass ratio of the water reducing agent to the thermal insulation material is 1:1; the mass ratio of the water reducing agent to sodium silicate is 0.2:1.

[0240] The water reducing agent used in this comparative example is an amino sulfonic acid type water reducing agent.

[0241] The thermal insulation material used in this comparative example is composite silicate.

[0242] The composition of the high-calcium tailings used in this comparative example includes: CaO 15.22 wt%, SiO2 20.18 wt%, and Al2O3 5.17 wt%.

[0243] The digestion temperature of the highly reactive lime used in this comparative example is 110°C, and the digestion time is 40 min.

[0244] The composition of the fly ash used in this comparative example includes: SiO2 49.08 wt%, Al2O3 15.78 wt%, and CaO 9.26 wt%.

[0245] When the slurry is formed and cured, it is first cast in a prefabricated mold, then covered with a film and cured at room temperature for 4 h. After demolding, it is cured at room temperature, and finally the formed tailings geopolymer is obtained. After testing, the 7-day compressive strength value of the obtained geopolymer is 43.5 MPa.

[0246] Combined with the experimental phenomena, comparing Example 4 with Comparative Example 8 and Comparative Example 9, it is found that when the content of sodium hydroxide is too low, it is not sufficient to induce the micro-reaction on the surface of the high-calcium tailings, the heat provided is also insufficient, and the alkalinity in the reaction system decreases, which may also cause insufficient dissolution of Si and Al in some tailings and fly ash, resulting in a reduction in the gel substance of geopolymerization and a decrease in the compressive strength of the specimen. Excessive alkali may introduce more pores, leading to a decrease in the density and an increase in the water absorption rate of the geopolymer, reducing the mechanical properties and durability of the geopolymer, and a large amount of white frost will be generated during the subsequent placement of the geopolymer.

[0247] Comparative Example 10

[0248] Compared with Example 4, in this comparative example, the dosage of fly ash is increased (the mass ratio of high-calcium tailings to fly ash is 0.6:1), and other processes are the same as those in Example 4. The specific situation is as follows.

[0249] The tailings geopolymer in this comparative example is obtained by forming and curing the slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 30:1, and the water content of the mixed slurry is 15 wt%.

[0250] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 2 parts of sodium hydroxide, 3 parts of highly reactive lime, and 100 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 200 rpm and a treatment time of 60 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling.

[0251] The raw materials of the geopolymer additive B include a water reducing agent, a thermal insulation material, and sodium silicate; the geopolymer additive B is obtained by mixing them evenly. The mass ratio of the water reducing agent to the thermal insulation material is 1:1; the mass ratio of the water reducing agent to sodium silicate is 0.2:1.

[0252] The water reducing agent used in this comparative example is an amino sulfonic acid-based water reducing agent.

[0253] The thermal insulation material used in this comparative example is compound silicate.

[0254] The composition of the high-calcium tailings used in this comparative example includes: 15.22 wt% CaO, 20.18 wt% SiO₂, 5.17 wt% Al₂O₃.

[0255] The digestion temperature of the highly reactive lime used in this comparative example is 110 °C, and the digestion time is 40 min.

[0256] The composition of the fly ash used in this comparative example includes: 49.08 wt% SiO₂, 15.78 wt% Al₂O₃, 9.26 wt% CaO.

[0257] When the slurry is formed and cured, it is first cast in a prefabricated mold, then covered with a film and cured at room temperature for 4 h, demolded and then cured at room temperature, and finally the formed tailings-based geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 53.8 MPa.

[0258] Comparative Example 11

[0259] Compared with Example 4, this comparative example reduces the amount of fly ash used (the mass ratio of high-calcium tailings to fly ash is 5:1), and other processes are the same as those in Example 4. The specific situation is as follows.

[0260] The tailings-based geopolymer in this comparative example is obtained by forming and curing a slurry formed by mixing the geopolymer precursor powder A and the geopolymer additive B with water; the mass ratio of the geopolymer precursor powder A to the geopolymer additive B is 30:1, and the water content of the mixed slurry is 15 wt%;

[0261] The raw materials of the geopolymer precursor powder A include (by weight): 60 parts of high-calcium tailings, 2 parts of sodium hydroxide, 3 parts of highly reactive lime, and 12 parts of fly ash; first, the high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated by high-energy ball milling (using a high-energy stirring ball mill with a rotation speed of 200 rpm and a treatment time of 60 min), and then all the raw materials of the geopolymer precursor powder A are mixed evenly by ordinary ball milling;

[0262] The raw materials of the geopolymer additive B include a water reducing agent, a thermal insulation material, and sodium silicate; they are uniformly mixed to obtain the geopolymer additive B. Among them, the mass ratio of the water reducing agent to the thermal insulation material is 1:1; the mass ratio of the water reducing agent to sodium silicate is 0.2:1.

[0263] The water reducing agent used in this comparative example is an amino sulfonic acid-based water reducing agent.

[0264] The thermal insulation material used in this comparative example is compound silicate.

[0265] The composition of the high-calcium tailings used in this comparative example includes: 15.22 wt% CaO, 20.18 wt% SiO₂, and 5.17 wt% Al₂O₃.

[0266] The digestion temperature of the highly reactive lime used in this comparative example is 110 °C, and the digestion time is 40 min.

[0267] The composition of the fly ash used in this comparative example includes: 49.08 wt% SiO₂, 15.78 wt% Al₂O₃, and 9.26 wt% CaO.

[0268] When the slurry is formed and cured, it is first cast and formed in a prefabricated mold, then covered with a film and cured at room temperature for 4 h. After demolding, it is cured at room temperature, and finally, the formed tailings-based geopolymer is obtained; after testing, the 7-day compressive strength value of the obtained geopolymer is 40.25 MPa.

[0269] Comparing Example 4 with Comparative Example 10 and Comparative Example 11, it is found that when the tailings content is too high, the compressive strength of the geopolymer decreases. It is speculated that this is because the active silicon-aluminum components in the raw materials decrease, which is not conducive to the subsequent hydration reaction of the geopolymer. When the amount of tailings used is small, the change in the compressive strength of the prepared geopolymer is not significant, but the consumption of tailings decreases, which is not conducive to the digestion of tailings.

[0270] Table 1 Compressive strength test results of each example and comparative example

[0271]

Claims

1. An autothermal early-strength tailing-based geopolymer, characterized in that, It is obtained by forming a slurry by mixing geopolymer precursor powder A and geopolymer additive B with or without water and then subjecting it to shaping and curing. The raw materials of the geopolymer precursor powder A include high-calcium tailings, sodium hydroxide, highly reactive lime, and fly ash; before mixing the raw materials of the geopolymer precursor powder A, the raw materials including high-calcium tailings, sodium hydroxide, and highly reactive lime are mechanically activated together. The raw materials of the geopolymer additive B include a water reducing agent, a thermal insulation material, and water glass. In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to highly reactive lime is 10 - 110:

1. In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to sodium hydroxide is 20 - 110:

1. In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is below 4.5:

1. In the slurry, the mass ratio of the dosage of geopolymer precursor powder A to geopolymer additive B is 1 - 100:

1. The water content of the slurry is 40wt% or less. The mechanical activation adopts the high-energy ball milling method; the rotation speed of the high-energy ball milling method is 200rpm or more; the treatment time of the high-energy ball milling method is 5min or more. The composition of the high-calcium tailings includes: 15wt% - 30wt% CaO, 20wt% - 50wt% SiO2, 5wt% - 10wt% Al2O3. The digestion temperature of the highly reactive lime is 90°C or more, and the digestion time is 30min or more.

2. The self-heating and early-strength tailings geopolymer according to claim 1, characterized in that, The water reducing agent is one or more of polycarboxylic acid type, lignosulfonate type, and aminosulfonic acid type; the thermal insulation material is one or more of polystyrene particles, expanded perlite beads, and composite silicate; the water content of the water glass is 50wt% - 60wt%.

3. The self-heating early-strength tailings geopolymer according to claim 1, wherein In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to highly reactive lime is 20 - 100:1; in the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to sodium hydroxide is 30 - 100:

1. In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is below 4:

1. The composition of the fly ash includes: 35wt% - 50wt% SiO2, 15wt% - 35wt% Al2O3, 2wt% - 10wt% CaO.

4. The self-heating and early-strength tailing-based geopolymer according to claim 3, characterized in that, In the geopolymer precursor powder A, the mass ratio of the dosage of high-calcium tailings to fly ash is 0.8 - 3:

1.

5. The self-heating and early-strength tailings geopolymer according to claim 1 or 2, wherein In the geopolymer additive B, the mass ratio of the dosage of the water reducing agent to the thermal insulation material is 1 - 10:

1.

6. The self-heating and early-strength tailings geopolymer according to claim 1 or 2, characterized in that, In the geopolymer additive B, the mass ratio of the dosage of the water reducing agent to water glass is 0.1 - 0.4:

1.

7. The self-heating and early-strength tailing geopolymer according to claim 1, wherein In the slurry, the mass ratio of the dosage of geopolymer precursor powder A to geopolymer additive B is 2 - 60:1; the water content of the slurry is 10wt% - 30wt%; the curing time of the slurry is 4 - 72h.

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