Coal gangue dry-mixed mortar and preparation method thereof

Abstract

The invention relates to the technical field of preparation of coal gangue dry-mixed mortar, in particular to coal gangue dry-mixed mortar and a preparation method thereof. The coal gangue dry-mixed mortar is prepared from the following raw materials in parts by weight: 40-60 parts of modified aggregate, 2-5 parts of slaked lime, 5-15 parts of slag powder, 0.2-0.5 part of fiber, 2-4 parts of gypsum, 0.2-0.55 part of chemical additive, 15-25 parts of cement, 0.4-1 part of functional agent and 5-10 parts of modified calcite powder. By adding the modified aggregate, pores of the coal gangue aggregate can be reduced, the compressive strength of the coal gangue aggregate is improved, by adding the modified calcite powder, the mortar strength can be improved, the impermeability and durability of the mortar can also be improved, and by adding the hydroxypropyl methyl cellulose, a colloidal solution is formed in water, free water is adsorbed and locked, so that the mortar strength is improved. Under the synergistic effect with guar gum ether, the viscosity loss caused by water evaporation and hydration reaction can be reduced, so that the mortar still keeps good operability within a relatively long time.

Description

Technical Field

[0001] This invention relates to the field of coal gangue dry-mixed slurry preparation technology, specifically to a coal gangue dry-mixed mortar and its preparation method. Background Technology

[0002] Coal gangue dry slurry is a dry powder building material made by mixing coal gangue, a solid waste generated during coal mining and washing, with cement, additives, etc., in a specific ratio as the core raw material (or main admixture). Coal gangue dry slurry is a typical building material that "turns waste into treasure". It not only solves the environmental problem of coal gangue accumulation, but also provides construction projects with adjustable performance and controllable cost material options, which is in line with the development trend of green building materials.

[0003] While existing dry-mixed coal gangue mortars achieve solid waste resource utilization, they suffer from limitations in strength and durability due to raw material characteristics, processing technology, and application scenarios. These limitations make them unsuitable for high-pressure applications and result in high strength loss during freeze-thaw cycles. Furthermore, their water retention is poor, leading to rapid water loss and decreased bonding strength. Therefore, this invention provides a dry-mixed coal gangue mortar and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a dry-mixed coal gangue mortar and its preparation method. The dry-mixed coal gangue mortar prepared by this invention not only has good strength and durability, but also reduces the strength loss rate in terms of freeze-thaw cycle resistance, and also has good water retention, which brings convenience to the later construction.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a dry-mixed mortar made from coal gangue, characterized in that it is composed of the following raw materials in parts by weight: 40-60 parts modified aggregate, 2-5 parts quicklime, 5-15 parts slag powder, 0.2-0.5 parts fiber, 2-4 parts gypsum, 0.2-0.55 parts chemical additives, 15-25 parts cement, 0.4-1 part functional agent, and 5-10 parts modified calcite powder; The preparation steps of the coal gangue dry-mixed mortar are as follows: S1. A mixed solvent is prepared by mixing chemical additives with cement accounting for 5-10% of the total cement content; S2. Add the modified aggregate to the mixer and stir at 120 rpm. Add the modified calcite powder and slag powder in sequence and stir for 3 minutes. Set aside. S3. Add the remaining cement, quicklime, and gypsum, stir for 3-5 minutes, and set aside. S4. Add the mixed solvent, then add the fiber, stir for 3-5 minutes, add the functional agent, stir for 5-8 minutes, and obtain the dry-mixed coal gangue mortar.

[0006] The slag powder used is grade S95 slag powder.

[0007] Further, the preparation steps of the modified aggregate are as follows: Coal gangue aggregate is soaked in a mixed solution of 5% calcium chloride and 3% sodium sulfate for 70 minutes, then dried using a drying pan at 105°C for 1-2 hours to obtain dried coal gangue aggregate. The dried coal gangue aggregate is then soaked in a 5% calcium chloride solution for 20 minutes, dried using a drying pan at 60°C for 1-2 hours to obtain the modified aggregate. The modified coal gangue aggregate, obtained through calcium chloride and sodium sulfate modification, becomes denser, improving its compressive strength. It also activates the activity of the coal gangue aggregate and slag powder, promoting the formation of ettringite, increasing stress transfer rate and overall mechanical properties of the mortar, and reducing interfacial cracks.

[0008] Coal gangue aggregate uses either spontaneously combusted coal gangue or coal gangue that has been artificially calcined.

[0009] Furthermore, the fiber is composed of 40-50% pp fiber and 50-60% cellulose fiber.

[0010] Furthermore, the chemical additive consists of 45-60% polycarboxylate superplasticizer, 40-45% hydroxypropyl methylcellulose, and 5-10% guar gum ether.

[0011] Furthermore, the coal gangue aggregate is composed of 60% coarse coal gangue aggregate and 40% fine coal gangue aggregate, with the coarse coal gangue aggregate having a particle size of 5-10 mm and the fine coal gangue aggregate having a particle size of <0.6 mm.

[0012] Furthermore, the functional agent is composed of 50% polyether polyol and 50% glycerol polyoxypropylene ether.

[0013] Further, the preparation steps of the modified calcite powder are as follows: calcite is ground to 400-500 mesh using a ball mill to obtain calcite particles; the calcite particles are dried in a drying oven to obtain dried calcite particles; a high-speed mixer is heated to 100-110℃, and the dried calcite particles are added and stirred at 1200 rpm for 30 minutes; a solvent is sprayed onto the stirred dried calcite particles, and the temperature is controlled at 100-105℃ for 5-15 minutes to obtain modified calcite powder. The modified calcite powder can be fully filled into the modified aggregate, making the mortar structure more compact. It can not only improve the mortar strength, but also increase the mortar's impermeability and durability. It can also work synergistically with PP fiber and cellulose fiber to improve the mortar's freeze-thaw resistance and crack resistance, solving the freeze-thaw damage problem.

[0014] Furthermore, the solvent is composed of a titanate coupling agent and liquid paraffin mixed in a 1:1 mass ratio; The solvent preparation steps are as follows: Liquid paraffin is added to a reaction vessel and stirred at a speed of 300-500 rpm. Titanate coupling agent is added in batches, 10%-20% each time, with a 5-minute interval between each addition. Once all the titanate coupling agent is added to the reaction vessel, the speed is increased to 1000-2000 rpm and stirred for 15-30 minutes. The reaction vessel is then heated to a temperature of 50-70℃, and the speed is adjusted to 800-1200 rpm. Stirring is continued for 20-30 minutes, and the speed is adjusted to 200-300 rpm. The reaction vessel is then allowed to cool naturally to 18-25℃ to obtain the solvent.

[0015] Furthermore, the mass ratio of the dried calcite particles to the solvent is 1:(0.01-0.06).

[0016] Further, the preparation steps of the mixed solvent are as follows: 3.5-8% of the total cement is stirred in a reactor at a speed of 300-600 rpm, polycarboxylate superplasticizer, hydroxypropyl methylcellulose and guar gum are added, and stirred for 5-10 minutes. Then, 1.5-2% of the total cement is added and stirred for 5-10 minutes to obtain the mixed solvent. Hydroxypropyl methylcellulose can dissolve in water and form a high-viscosity colloidal solution, which can adsorb and lock in free water, slow down the evaporation of water, and also make the aqueous solution have a high viscosity, significantly increasing the viscosity of the mortar paste, providing water for the hydration of cement and slag powder. It can also work synergistically with guar gum and polycarboxylate superplasticizer to greatly improve the fluidity and water retention of the mortar.

[0017] The cement used is ordinary Portland cement, with a strength grade of 42.5.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention modifies coal gangue aggregate using calcium chloride and sodium sulfate, which reduces the porosity of the coal gangue aggregate itself, improves its compressive strength, makes it denser and more durable, and also stimulates the activity of coal gangue aggregate and slag powder, promotes the formation of ettringite, forms an "aggregate-slurry" interface, improves stress transfer rate, reduces interface cracks, and improves the overall mechanical properties of mortar. Calcium chloride can also accelerate the hydration reaction of cement, shorten the setting time, and improve early strength.

[0019] 2. This invention, by adding modified calcite powder, can better fill the voids between cement, slag powder, and coal gangue aggregates, making the mortar structure more compact. This not only improves strength but also increases the mortar's impermeability and durability. When the mortar develops microcracks due to drying shrinkage, temperature changes, or external forces, the PP fibers will cross the cracks, absorbing and dispersing stress, significantly improving the mortar's toughness and impact resistance. Cellulose fibers have extremely strong hydrophilicity, which can adsorb and lock in a large amount of free water, greatly slowing down the rate of water loss from the mortar surface, allowing for more complete hydration and uniform shrinkage within the mortar, thereby effectively preventing the formation of plastic cracks. The synergistic effect of titanate coupling agent-modified calcite powder, polycarboxylate superplasticizer, and PP fibers solves the freeze-thaw damage problem from two aspects: "enhancing the antifreeze structure" and "improving crack resistance."

[0020] 3. This invention, by adding hydroxypropyl methylcellulose, can dissolve in water and form a high-viscosity colloidal solution. This solution can adsorb and lock in a large amount of free water, greatly slowing down water evaporation and loss to the porous substrate. Its aqueous solution has a high viscosity, which can significantly increase the viscosity of the mortar. It can also provide the necessary water for the continuous hydration reaction of cement and slag powder, avoiding incomplete hydration, strength reduction, and surface powdering due to water shortage. It increases the cohesiveness and lubricity of the mortar, making it easier to plaster and improving construction efficiency. The combination of guar gum and hydroxypropyl methylcellulose can better maintain the stability of the mortar consistency, slow down the consistency loss caused by water evaporation and hydration reaction, and keep the mortar in good workability for a longer period of time. The synergistic effect of hydroxypropyl methylcellulose, guar gum, and polycarboxylate superplasticizer greatly improves the fluidity and water retention of the mortar.

[0021] 4. This invention introduces a large number of uniform, closed, and micro-sized air bubbles into the mortar by adding polyether polyol. These air bubbles act as physical lubricants between mortar particles, reducing internal frictional resistance and making the mortar smoother. This makes plastering easier and more efficient, significantly reducing the labor intensity of workers. The introduced micro-bubbles can accommodate the volume expansion of water when it freezes, which helps improve freeze-thaw resistance and also enhances the deformation capacity of the mortar. Glyceryl polyoxypropylene ether has strong hydrophilicity and film-forming properties, which can stabilize the air bubbles introduced by the polyether polyol, preventing small air bubbles from merging into large air bubbles or rupturing, ensuring the durability and stability of the air bubble system. At the same time, its molecules can adsorb water, providing an auxiliary water retention effect. The synergistic effect of polyether polyol and glyceryl polyoxypropylene ether can make the actual construction process smoother, easier, and more efficient. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0024] Example 1

[0025] A dry-mixed mortar made from coal gangue is composed of the following raw materials in parts by weight: 40 parts modified aggregate, 2 parts quicklime, 5 parts slag powder, 0.2 parts fiber, 2 parts gypsum, 0.2 parts chemical additives, 15 parts cement, 0.4 parts functional agent, and 5 parts modified calcite powder. The preparation steps for coal gangue dry-mixed mortar are as follows: S1. A mixed solvent is prepared by mixing chemical additives with cement accounting for 5-10% of the total cement content; S2. Add the modified aggregate to the mixer and stir at 120 rpm. Add the modified calcite powder and slag powder in sequence and stir for 3 minutes. Set aside. S3. Add the remaining cement, quicklime, and gypsum, stir for 3-5 minutes, and set aside. S4. Add the mixed solvent, then add the fiber, stir for 3-5 minutes, add the functional agent, stir for 5-8 minutes, and obtain the dry-mixed coal gangue mortar.

[0026] The preparation steps of the modified aggregate are as follows: Soak coal gangue aggregate in a mixed solution of 5% calcium chloride and 3% sodium sulfate for 70 minutes, then dry it using a drying pan at 105℃ for 1-2 hours to obtain dried coal gangue aggregate. Soak the dried coal gangue aggregate in a 5% calcium chloride solution for 20 minutes, then dry it using a drying pan at 60℃ for 1-2 hours to obtain the modified aggregate.

[0027] The fiber consists of 40-50% PP fiber and 50-60% cellulose fiber.

[0028] The chemical additives consist of 45-60% polycarboxylate superplasticizer, 40-45% hydroxypropyl methylcellulose, and 5-10% guar gum ether.

[0029] Coal gangue aggregate is composed of 60% coarse coal gangue aggregate and 40% fine coal gangue aggregate. The coarse coal gangue aggregate has a particle size of 5-10 mm, and the fine coal gangue aggregate has a particle size of <0.6 mm.

[0030] The functional agent consists of 50% polyether polyol and 50% glycerol polyoxypropylene ether.

[0031] The preparation steps of modified calcite powder are as follows: calcite is ground to 400-500 mesh using a ball mill to obtain calcite particles; the calcite particles are dried in a drying oven to obtain dried calcite particles; a high-speed mixer is heated to 100-110℃, and the dried calcite particles are added and stirred at 1200 rpm for 30 minutes; solvent is sprayed onto the stirred dried calcite particles, and the temperature is controlled at 100-105℃ for 5-15 minutes to obtain modified calcite powder.

[0032] The solvent is composed of titanate coupling agent and liquid paraffin mixed in a 1:1 mass ratio; The solvent preparation steps are as follows: Liquid paraffin is added to a reaction vessel and stirred at a speed of 300-500 rpm. Titanate coupling agent is added in batches, 10%-20% each time, with an interval of 5 minutes between each addition. After all the titanate coupling agent is added to the reaction vessel, the speed is increased to 1000-2000 rpm and stirred for 15-30 minutes. The reaction vessel is then heated to a temperature of 50-70℃, and the speed is adjusted to 800-1200 rpm. Stirring is continued for 20-30 minutes, and the speed is adjusted to 200-300 rpm. The reaction vessel is then allowed to cool naturally to 18-25℃ to obtain the solvent.

[0033] The mass ratio of dried calcite particles to solvent is 1:(0.01-0.06).

[0034] The preparation steps of the mixed solvent are as follows: 3.5-8% of the total cement is stirred in a reaction vessel at a speed of 300-600 rpm, polycarboxylate superplasticizer, hydroxypropyl methylcellulose and guar gum are added and stirred for 5-10 minutes, then 1.5-2% of the total cement is added and stirred for 5-10 minutes to obtain the mixed solvent.

[0035] Example 2

[0036] A dry-mixed mortar made from coal gangue is composed of the following raw materials in parts by weight: 50 parts modified aggregate, 3.5 parts quicklime, 10 parts slag powder, 0.35 parts fiber, 3 parts gypsum, 0.35 parts chemical additives, 20 parts cement, 0.7 parts functional agent, and 7.5 parts modified calcite powder. The preparation steps for coal gangue dry-mixed mortar are as follows: S1. A mixed solvent is prepared by mixing chemical additives with cement accounting for 5-10% of the total cement content; S2. Add the modified aggregate to the mixer and stir at 120 rpm. Add the modified calcite powder and slag powder in sequence and stir for 3 minutes. Set aside. S3. Add the remaining cement, quicklime, and gypsum, stir for 3-5 minutes, and set aside. S4. Add the mixed solvent, then add the fiber, stir for 3-5 minutes, add the functional agent, stir for 5-8 minutes, and obtain the dry-mixed coal gangue mortar.

[0037] The preparation steps of the modified aggregate are as follows: Soak coal gangue aggregate in a mixed solution of 5% calcium chloride and 3% sodium sulfate for 70 minutes, then dry it using a drying pan at 105℃ for 1-2 hours to obtain dried coal gangue aggregate. Soak the dried coal gangue aggregate in a 5% calcium chloride solution for 20 minutes, then dry it using a drying pan at 60℃ for 1-2 hours to obtain the modified aggregate.

[0038] The fiber consists of 40-50% PP fiber and 50-60% cellulose fiber.

[0039] The chemical additives consist of 45-60% polycarboxylate superplasticizer, 40-45% hydroxypropyl methylcellulose, and 5-10% guar gum ether.

[0040] Coal gangue aggregate is composed of 60% coarse coal gangue aggregate and 40% fine coal gangue aggregate. The coarse coal gangue aggregate has a particle size of 5-10 mm, and the fine coal gangue aggregate has a particle size of <0.6 mm.

[0041] The functional agent consists of 50% polyether polyol and 50% glycerol polyoxypropylene ether.

[0042] The preparation steps of modified calcite powder are as follows: calcite is ground to 400-500 mesh using a ball mill to obtain calcite particles; the calcite particles are dried in a drying oven to obtain dried calcite particles; a high-speed mixer is heated to 100-110℃, and the dried calcite particles are added and stirred at 1200 rpm for 30 minutes; solvent is sprayed onto the stirred dried calcite particles, and the temperature is controlled at 100-105℃ for 5-15 minutes to obtain modified calcite powder.

[0043] The solvent is composed of titanate coupling agent and liquid paraffin mixed in a 1:1 mass ratio; The solvent preparation steps are as follows: Liquid paraffin is added to a reaction vessel and stirred at a speed of 300-500 rpm. Titanate coupling agent is added in batches, 10%-20% each time, with an interval of 5 minutes between each addition. After all the titanate coupling agent is added to the reaction vessel, the speed is increased to 1000-2000 rpm and stirred for 15-30 minutes. The reaction vessel is then heated to a temperature of 50-70℃, and the speed is adjusted to 800-1200 rpm. Stirring is continued for 20-30 minutes, and the speed is adjusted to 200-300 rpm. The reaction vessel is then allowed to cool naturally to 18-25℃ to obtain the solvent.

[0044] The mass ratio of dried calcite particles to solvent is 1:(0.01-0.06).

[0045] The preparation steps of the mixed solvent are as follows: 3.5-8% of the total cement is stirred in a reaction vessel at a speed of 300-600 rpm, polycarboxylate superplasticizer, hydroxypropyl methylcellulose and guar gum are added and stirred for 5-10 minutes, then 1.5-2% of the total cement is added and stirred for 5-10 minutes to obtain the mixed solvent.

[0046] Example 3

[0047] A dry-mixed mortar made from coal gangue is composed of the following raw materials in parts by weight: 60 parts modified aggregate, 5 parts quicklime, 15 parts slag powder, 0.5 parts fiber, 4 parts gypsum, 0.55 parts chemical additives, 25 parts cement, 1 part functional agent, and 10 parts modified calcite powder. The preparation steps for coal gangue dry-mixed mortar are as follows: S1. A mixed solvent is prepared by mixing chemical additives with cement accounting for 5-10% of the total cement content; S2. Add the modified aggregate to the mixer and stir at 120 rpm. Add the modified calcite powder and slag powder in sequence and stir for 3 minutes. Set aside. S3. Add the remaining cement, quicklime, and gypsum, stir for 3-5 minutes, and set aside. S4. Add the mixed solvent, then add the fiber, stir for 3-5 minutes, add the functional agent, stir for 5-8 minutes, and obtain the dry-mixed coal gangue mortar.

[0048] The preparation steps of the modified aggregate are as follows: Soak coal gangue aggregate in a mixed solution of 5% calcium chloride and 3% sodium sulfate for 70 minutes, then dry it using a drying pan at 105℃ for 1-2 hours to obtain dried coal gangue aggregate. Soak the dried coal gangue aggregate in a 5% calcium chloride solution for 20 minutes, then dry it using a drying pan at 60℃ for 1-2 hours to obtain the modified aggregate.

[0049] The fiber consists of 40-50% PP fiber and 50-60% cellulose fiber.

[0050] The chemical additives consist of 45-60% polycarboxylate superplasticizer, 40-45% hydroxypropyl methylcellulose, and 5-10% guar gum ether.

[0051] Coal gangue aggregate is composed of 60% coarse coal gangue aggregate and 40% fine coal gangue aggregate. The coarse coal gangue aggregate has a particle size of 5-10 mm, and the fine coal gangue aggregate has a particle size of <0.6 mm.

[0052] The functional agent consists of 50% polyether polyol and 50% glycerol polyoxypropylene ether.

[0053] The preparation steps of modified calcite powder are as follows: calcite is ground to 400-500 mesh using a ball mill to obtain calcite particles; the calcite particles are dried in a drying oven to obtain dried calcite particles; a high-speed mixer is heated to 100-110℃, and the dried calcite particles are added and stirred at 1200 rpm for 30 minutes; solvent is sprayed onto the stirred dried calcite particles, and the temperature is controlled at 100-105℃ for 5-15 minutes to obtain modified calcite powder.

[0054] The solvent is composed of titanate coupling agent and liquid paraffin mixed in a 1:1 mass ratio; The solvent preparation steps are as follows: Liquid paraffin is added to a reaction vessel and stirred at a speed of 300-500 rpm. Titanate coupling agent is added in batches, 10%-20% each time, with an interval of 5 minutes between each addition. After all the titanate coupling agent is added to the reaction vessel, the speed is increased to 1000-2000 rpm and stirred for 15-30 minutes. The reaction vessel is then heated to a temperature of 50-70℃, and the speed is adjusted to 800-1200 rpm. Stirring is continued for 20-30 minutes, and the speed is adjusted to 200-300 rpm. The reaction vessel is then allowed to cool naturally to 18-25℃ to obtain the solvent.

[0055] The mass ratio of dried calcite particles to solvent is 1:(0.01-0.06).

[0056] The preparation steps of the mixed solvent are as follows: 3.5-8% of the total cement is stirred in a reaction vessel at a speed of 300-600 rpm, polycarboxylate superplasticizer, hydroxypropyl methylcellulose and guar gum are added and stirred for 5-10 minutes, then 1.5-2% of the total cement is added and stirred for 5-10 minutes to obtain the mixed solvent.

[0057] Comparative Example 1: The difference between this comparative example and Example 1 is that the modified coal gangue aggregate is replaced with coal gangue aggregate.

[0058] Comparative Example 2: The difference between this comparative example and Example 1 is that the modified calcite powder is replaced with calcite powder.

[0059] Comparative Example 3 differs from Example 1 in that hydroxypropyl methylcellulose and guar gum ether, chemical additives, were not added during the preparation of this comparative example.

[0060] Performance testing: The relevant properties of the coal gangue dry-mixed mortar samples provided in Examples 1 to 3 and Comparative Examples 1 to 3 were tested respectively, and the test data are recorded in the table below:

[0061] Among them, the compressive strength test of coal gangue dry-mixed mortar prepared by Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 in JGJ / T70-2009 was carried out. Tests were conducted on the frost resistance strength loss rate of dry-mixed coal gangue mortar prepared according to the test methods in GB / T29756-2013, namely, Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The water retention rate of dry-mixed coal gangue mortar prepared according to the test methods in GB / T29756-2013 (Examples 1, 2, 3, Comparative Examples 1, 2, and 3) was tested.

[0062] By comparing and analyzing the relevant data in the table, it can be seen that the dry-mixed coal gangue mortar prepared by this invention not only has good compressive strength and frost resistance strength loss rate, but also excellent water retention. This indicates that the preparation method of dry-mixed coal gangue mortar provided by this invention has a broader market prospect and is more suitable for widespread application.

[0063] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0064] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A dry-mixed mortar for coal gangue, characterized in that, It is composed of the following raw materials in parts by weight: 40-60 parts modified aggregate, 2-5 parts quicklime, 5-15 parts slag powder, 0.2-0.5 parts fiber, 2-4 parts gypsum, 0.2-0.55 parts chemical additives, 15-25 parts cement, 0.4-1 part functional agent, and 5-10 parts modified calcite powder. The preparation steps of the coal gangue dry-mixed mortar are as follows: S1. A mixed solvent is prepared by mixing chemical additives with cement accounting for 5-10% of the total cement content; S2. Add the modified aggregate to the mixer and stir at 120 rpm. Add the modified calcite powder and slag powder in sequence and stir for 3 minutes. Set aside. S3. Add the remaining cement, quicklime, and gypsum, stir for 3-5 minutes, and set aside. S4. Add the mixed solvent, then add the fiber, stir for 3-5 minutes, add the functional agent, stir for 5-8 minutes, and obtain the dry-mixed coal gangue mortar.

2. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The modified aggregate is prepared by soaking coal gangue aggregate in a mixed solution of 5% calcium chloride and 3% sodium sulfate for 70 minutes, drying it with a drying pan at 105°C for 1-2 hours to obtain dried coal gangue aggregate, and then soaking the dried coal gangue aggregate in a 5% calcium chloride solution for 20 minutes, drying it with a drying pan at 60°C for 1-2 hours to obtain modified aggregate.

3. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The fiber consists of 40-50% PP fiber and 50-60% cellulose fiber.

4. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The chemical additive consists of 45-60% polycarboxylate superplasticizer, 40-45% hydroxypropyl methylcellulose, and 5-10% guar gum ether.

5. The dry-mixed coal gangue mortar according to claim 2, characterized in that, The coal gangue aggregate is composed of 60% coarse coal gangue aggregate and 40% fine coal gangue aggregate, with the coarse coal gangue aggregate having a particle size of 5-10 mm and the fine coal gangue aggregate having a particle size of <0.6 mm.

6. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The functional agent is composed of 50% polyether polyol and 50% glycerol polyoxypropylene ether.

7. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The preparation steps of the modified calcite powder are as follows: calcite is ground to 400-500 mesh using a ball mill to obtain calcite particles; the calcite particles are dried in a drying oven to obtain dried calcite particles; a high-speed mixer is heated to 100-110℃, and the dried calcite particles are added and stirred at 1200 rpm for 30 minutes; a solvent is sprayed onto the stirred dried calcite particles, and the temperature is controlled at 100-105℃ for 5-15 minutes to obtain modified calcite powder.

8. The dry-mixed coal gangue mortar according to claim 7, characterized in that, The solvent is composed of a titanate coupling agent and liquid paraffin mixed in a 1:1 mass ratio. The solvent preparation steps are as follows: Liquid paraffin is added to a reaction vessel and stirred at a speed of 300-500 rpm. Titanate coupling agent is added in batches, 10%-20% each time, with a 5-minute interval between each addition. Once all the titanate coupling agent is added to the reaction vessel, the speed is increased to 1000-2000 rpm and stirred for 15-30 minutes. The reaction vessel is then heated to a temperature of 50-70℃, and the speed is adjusted to 800-1200 rpm. Stirring is continued for 20-30 minutes, and the speed is adjusted to 200-300 rpm. The reaction vessel is then allowed to cool naturally to 18-25℃ to obtain the solvent.

9. The dry-mixed coal gangue mortar according to claim 7, characterized in that, The mass ratio of the dried calcite particles to the solvent is 1:(0.01-0.06).

10. The dry-mixed coal gangue mortar according to claim 1, characterized in that, The preparation steps of the mixed solvent are as follows: 3.5-8% of the total cement is stirred in a reaction vessel at a speed of 300-600 rpm, polycarboxylate superplasticizer, hydroxypropyl methylcellulose and guar gum are added and stirred for 5-10 minutes, then 1.5-2% of the total cement is added and stirred for 5-10 minutes to obtain the mixed solvent.

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