Fly ash gangue cement solid for coal mines and preparation method thereof

Abstract

The present invention relates to the field of mine filling technology, and more particularly to a fly ash and gangue cement for coal mines and a preparation method thereof. The fly ash and gangue cement for coal mines of the present invention comprises the following raw materials in parts by weight: 50-60 parts of coal gangue, 10-15 parts of cement, 25-35 parts of fly ash, 5-10 parts of modified fly ash, 4-7 parts of an activator, and 1-5 parts of a water reducer. After being mixed with water, the fly ash and gangue cement for coal mines of the present invention has good fluidity, can meet the requirements of pipeline transportation, and has a short setting time. The compressive strength and heavy metal solidification capacity of the filling blocks formed by the cement after curing can meet the national standard requirements for filling materials. Therefore, the present invention has broad application prospects in the field of mine filling.

Description

Technical Field

[0001] The present invention relates to the technical field of mine filling, in particular to a fly ash and gangue cementitious material for coal mines and a preparation method thereof. Background Art

[0002] Coal resources are the main energy source in my country, providing strong support for the development of the national economy and social stability. This will not change at present or for a considerable period of time in the future.

[0003] As a by-product of coal mining and washing, the output of coal gangue has increased rapidly with the growth of coal consumption. The accumulation of coal gangue occupies a large amount of land resources, causing serious waste of resources, environmental pollution and other problems.

[0004] Patent technical document CN113321468B discloses a coal gangue cementitious filling material and a high-fluidity and high-solid content cementitious filling material slurry. The invention discloses a coal gangue cementitious filling material and a high-fluidity and high-solid content cementitious filling material slurry, wherein the coal gangue cementitious filling material is composed of coal gangue, cement, fly ash, auxiliary materials and water reducer; the cementitious filling material can obtain good fluidity with less water consumption, and the material has a certain strength after solidification and hardening in the filling area, which can meet the requirements of filling mining and goaf filling for the mechanical properties of filling materials. Patent document CN118754517A discloses a functional material for gangue backfill and its preparation method. The invention discloses a functional material for gangue backfill, which comprises, by weight, 800-1200 parts of silt, 50-60 parts of cement, 40-50 parts of fly ash, and 1-5 parts of modified polyacrylamide. The functional material for gangue backfill provided by the invention has excellent flame retardancy and can also reduce the land occupied by gangue accumulation and secondary pollution to the environment, thus facilitating the local, large-scale, reduced, and ecological utilization of gangue. The above patents all provide fly ash and gangue backfill materials. However, since gangue contains heavy metal ions, when used as a filling material, the heavy metal ions contained therein often flow into the soil with the infiltration of groundwater or rainwater, causing pollution to the environment. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a fly ash gangue cement for coal mines and a preparation method thereof, so as to solve the problem that heavy metal ions in traditional fly ash gangue cement flow into the soil with water, thereby causing environmental pollution.

[0006] Based on the above purpose, the present invention provides a fly ash gangue cement for coal mines, comprising the following raw materials in parts by weight: 50-60 parts of coal gangue, 10-15 parts of cement, 25-35 parts of fly ash, 5-10 parts of modified fly ash, 4-7 parts of activator, and 1-5 parts of water reducer;

[0007] The preparation steps of the modified fly ash are as follows:

[0008] S1: removing impurities from fly ash to obtain pretreated fly ash;

[0009] S2: Mix the pretreated fly ash, hydrogen peroxide and concentrated sulfuric acid, stir them evenly, let them stand until the gas is completely released, filter them, wash them and dry them to obtain hydroxylated fly ash;

[0010] S3: Mix and stir the hydroxylated fly ash and anhydrous ethanol, adjust the pH to 4.5-5, then add the silane coupling agent KH-570, react at 90-100°C for 12-14 hours, filter, wash, and dry to obtain olefinated fly ash;

[0011] S4: Sodium alginate is dissolved in deionized water at 50°C, followed by the addition of olefinated fly ash, polyacrylamide, trifluoroethyl acrylate and N,N-methylenebis(acrylamide). After ultrasonic homogenization, an initiator is added, and the fly ash is modified by reacting at 60-65°C for 3-4 hours, separation, washing, drying, crushing and screening.

[0012] Preferably, the coal gangue consists of coal gangue fine aggregate and coal gangue coarse aggregate in a weight ratio of 1:1.

[0013] Furthermore, the particle size of the coal gangue fine aggregate is 1-5 mm.

[0014] Furthermore, the particle size of the coal gangue coarse aggregate is 5-15 mm.

[0015] Preferably, the cement is ordinary Portland cement with a PO32.5.

[0016] Preferably, the particle size of the fly ash is 10-100 μm.

[0017] Preferably, the activator is a mixture of Na2SiO3, Na2SO4 and NaCl in a weight ratio of 1:2:3.

[0018] Preferably, the water reducer is one of a lignin sulfonate water reducer, a naphthalene water reducer, a polycarboxylic acid water reducer, a melamine water reducer or an aminosulfonate water reducer.

[0019] Preferably, the impurity removal in step S1 is performed by first using anhydrous ethanol and then using deionized water.

[0020] Preferably, the usage ratio of the pretreated fly ash, hydrogen peroxide and concentrated sulfuric acid in step S2 is 40-50 g: 50-60 ml: 50-60 ml.

[0021] Preferably, the concentration of the hydrogen peroxide in step S2 is 20%.

[0022] Preferably, the concentration of the concentrated sulfuric acid in step S2 is 98%.

[0023] Preferably, the washing in step S2 is washing to neutrality.

[0024] Preferably, in step S3, the weight ratio of the hydroxylated fly ash, the silane coupling agent KH-570 and the anhydrous ethanol is 30-40 g: 10-15 g: 300-500 g.

[0025] Preferably, the pH adjustment in step S3 is performed using formic acid.

[0026] Preferably, in step S4, the weight ratio of the olefinated fly ash, polyacrylamide, trifluoroethyl acrylate, N,N-methylenebis(acrylamide), sodium alginate, initiator and deionized water is 30-40g:20-25g:1-3g:1-5g:10-15g:0.03-0.05g:200-300g.

[0027] Preferably, the initiator in step S4 is ammonium persulfate.

[0028] Furthermore, the present invention also provides a method for preparing fly ash and gangue cement for coal mines, comprising the following steps:

[0029] The raw materials are mixed in proportion and stirred evenly to obtain fly ash gangue cement solid for coal mines.

[0030] The beneficial effects of the present invention are as follows: the slurry formed by mixing the fly ash gangue cement for coal mines with water has good fluidity, can meet the requirements of pipeline transportation, and has a short setting time. The filling blocks formed by its curing have excellent compressive strength and heavy metal solidification ability.

[0031] The fly ash gangue cement for coal mines of the present invention adds sodium alginate during the preparation of the modified fly ash, thereby significantly increasing the effective grafting density of polyacrylamide and fluorine chains and forming a three-dimensional network structure on the fly ash surface. This structure not only wraps the fly ash particles and the heavy metal ions adsorbed on their surfaces, but also fills the gaps between the particles, thereby improving the overall density of the material and enhancing the compressive strength of the filling block and the heavy metal solidification performance.

[0032] The fly ash gangue cement for coal mines of the present invention improves the hydrophobicity of the material by using a modified substance with a longer fluorine chain in the process of preparing the modified fly ash, and the long side bonds are entangled with each other, so that the compressive strength and heavy metal solidification performance of the filling body are improved to a certain extent. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0034] Example 1: A fly ash and gangue cement for coal mines, the specific preparation steps are as follows:

[0035] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 20 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 20 minutes, centrifuged, filtered, and vacuum dried for 12 hours to obtain pretreated fly ash;

[0036] (2) 40 g of pretreated fly ash, 50 ml of hydrogen peroxide (20%), and 50 ml of concentrated sulfuric acid (98%) were mixed and stirred evenly. After the gas was completely released, the mixture was filtered and washed to neutrality, and vacuum dried for 12 h to obtain hydroxylated fly ash.

[0037] (3) Disperse 30 g of hydroxylated fly ash in 300 g of anhydrous ethanol, add formic acid, adjust the pH to 4.5, then add 10 g of KH-570, maintain at 90 ° C for 12 h, and after the reaction is completed, filter, wash, and dry to obtain olefinated fly ash;

[0038] (4) At 50°C, 10 g of sodium alginate was placed in 200 g of deionized water. After it was completely dissolved, 30 g of olefinized fly ash, 20 g of polyacrylamide, 1 g of trifluoroethyl acrylate and 1 g of N,N-methylenebis(acrylamide) were mixed, and 0.03 g of ammonium persulfate was added. After reacting at 60°C for 3 h, the mixture was separated and washed with a mixture of water and methanol, and then dried in an oven at 60°C for 30 h. Finally, the mixture was powdered to obtain modified fly ash.

[0039] (5) Mix 50 g of coal gangue, 2.510 g of PO3, 25 g of fly ash, 5 g of modified fly ash, 4 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), and 1 g of naphthalene-based water reducer, and stir evenly to obtain fly ash gangue cement for coal mines.

[0040] Example 2: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0041] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 25 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 25 minutes, centrifuged, filtered, and vacuum dried for 20 hours to obtain pretreated fly ash;

[0042] (2) 45 g of pretreated fly ash, 55 ml of hydrogen peroxide (20%), and 55 ml of concentrated sulfuric acid (98%) were mixed and stirred evenly. After the gas was completely released, the mixture was filtered and washed to neutrality, and vacuum dried for 20 h to obtain hydroxylated fly ash.

[0043] (3) Disperse 35 g of hydroxylated fly ash in 400 g of anhydrous ethanol, add formic acid, adjust the pH to 4.7, then add 13 g of KH-570, maintain at 95 ° C for 13 h, and after the reaction is completed, filter, wash, and dry to obtain olefinated fly ash;

[0044] (4) At 50°C, 13g of sodium alginate was placed in 250g of deionized water. After it was completely dissolved, 35g of olefinized fly ash, 23g of polyacrylamide, 2g of trifluoroethyl acrylate and 2g of N,N-methylenebis(acrylamide) were mixed, and 0.04g of ammonium persulfate was added. After reacting at 63°C for 4h, the mixture was separated and washed with a mixture of water and methanol, and then dried in an oven at 65°C for 33h. Finally, the mixture was powdered to obtain modified fly ash.

[0045] (5) 55 g of coal gangue, 2.513 g of PO3, 30 g of fly ash, 8 g of modified fly ash, 6 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), and 3 g of naphthalene-based water reducer are mixed and stirred evenly to obtain fly ash gangue cement for coal mines.

[0046] Example 3: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0047] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 30 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 30 minutes, centrifuged, filtered, and vacuum dried for 24 hours to obtain pretreated fly ash;

[0048] (2) 50 g of pretreated fly ash, 60 ml of hydrogen peroxide (20%), and 60 ml of concentrated sulfuric acid (98%) were mixed and stirred evenly. After the gas was completely released, the mixture was filtered and washed to neutrality, and vacuum dried for 24 h to obtain hydroxylated fly ash.

[0049] (3) Disperse 40 g of hydroxylated fly ash in 500 g of anhydrous ethanol, add formic acid, adjust the pH to 5, then add 15 g of KH-570, and maintain at 100 ° C for 14 h. After the reaction is completed, filter, wash, and dry to obtain olefinated fly ash;

[0050] (4) At 50°C, 15g of sodium alginate was placed in 300g of deionized water. After it was completely dissolved, 40g of olefinized fly ash, 25g of polyacrylamide, 3g of trifluoroethyl acrylate and 5g of N,N-methylenebis(acrylamide) were mixed, and 0.05g of ammonium persulfate was added. After reacting at 65°C for 4h, the mixture was separated and washed with a mixture of water and methanol, and then dried in an oven at 70°C for 36h. Finally, the mixture was powdered to obtain modified fly ash.

[0051] (5) Mix 60 g of coal gangue, 2.515 g of PO3, 35 g of fly ash, 10 g of modified fly ash, 7 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), and 5 g of naphthalene-based water reducer, and stir evenly to obtain fly ash gangue cement for coal mines.

[0052] Comparative Example 1: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0053] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 25 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 25 minutes, centrifuged, filtered, and vacuum dried for 20 hours to obtain pretreated fly ash;

[0054] (2) 45 g of pretreated fly ash, 55 ml of hydrogen peroxide (20%), and 55 ml of concentrated sulfuric acid (98%) were mixed and stirred evenly. After the gas was completely released, the mixture was filtered and washed to neutrality, and vacuum dried for 20 h to obtain hydroxylated fly ash.

[0055] (3) Disperse 35 g of hydroxylated fly ash in 400 g of anhydrous ethanol, add formic acid, adjust the pH to 4.7, then add 13 g of KH-570, maintain at 95 ° C for 13 h, and after the reaction is completed, filter, wash, and dry to obtain olefinated fly ash;

[0056] (4) 35 g of olefinized fly ash, 23 g of polyacrylamide, 2 g of trifluoroethyl acrylate, 2 g of N,N-methylenebis(acrylamide) and 250 g of deionized water were mixed, and 0.04 g of ammonium persulfate was added. The mixture was reacted at 63° C. for 4 h, separated, washed with a mixture of water and methanol, and then dried in an oven at 65° C. for 33 h. Finally, the mixture was powdered to obtain modified fly ash.

[0057] (5) 55 g of coal gangue, 2.513 g of PO3, 30 g of fly ash, 8 g of modified fly ash, 6 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), 3 g of naphthalene-based water reducer and 1.38 g of sodium alginate are mixed and stirred evenly to obtain fly ash gangue cement for coal mines.

[0058] Comparative Example 2: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0059] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 25 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 25 minutes, centrifuged, filtered, and vacuum dried for 20 hours to obtain pretreated fly ash;

[0060] (2) 45 g of pretreated fly ash, 55 ml of hydrogen peroxide (20%), and 55 ml of concentrated sulfuric acid (98%) were mixed and stirred evenly. After the gas was completely released, the mixture was filtered and washed to neutrality, and vacuum dried for 20 h to obtain hydroxylated fly ash.

[0061] (3) Disperse 35 g of hydroxylated fly ash in 400 g of anhydrous ethanol, add formic acid, adjust the pH to 4.7, then add 13 g of KH-570, maintain at 95 ° C for 13 h, and after the reaction is completed, filter, wash, and dry to obtain olefinated fly ash;

[0062] (4) 35 g of olefinized fly ash, 23 g of polyacrylamide, 2 g of trifluoroethyl acrylate, 2 g of N,N-methylenebis(acrylamide) and 250 g of deionized water were mixed, and 0.04 g of ammonium persulfate was added. The mixture was reacted at 63° C. for 4 h, separated, washed with a mixture of water and methanol, and then dried in an oven at 65° C. for 33 h. Finally, the mixture was powdered to obtain modified fly ash.

[0063] (5) 55 g of coal gangue, 2.513 g of PO3, 30 g of fly ash, 8 g of modified fly ash, 6 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), and 3 g of naphthalene-based water reducer are mixed and stirred evenly to obtain fly ash gangue cement for coal mines.

[0064] Comparative Example 3: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0065] (1) Fly ash was dispersed in anhydrous ethanol, stirred evenly, ultrasonically removed impurities for 25 minutes, centrifuged and filtered, and then dispersed in deionized water, ultrasonically removed impurities for 25 minutes, centrifuged, filtered, and vacuum dried for 20 hours to obtain pretreated fly ash;

[0066] (2) 55 g of coal gangue, 2.513 g of PO3, 30 g of pretreated fly ash, 2.45 g of polyacrylamide, 1.38 g of sodium alginate, 0.21 g of trifluoroethyl acrylate, 6 g of activator (the weight ratio of Na2SiO3, Na2SO4 and NaCl is 1:2:3), and 3 g of naphthalene-based water reducer are mixed and stirred evenly to obtain fly ash gangue cement for coal mines.

[0067] Comparative Example 4: A fly ash gangue cement for coal mines, the specific preparation steps are as follows:

[0068] The difference from Example 2 is that trifluoroethyl acrylate is replaced by an equal mass of 1H,1H,2H,2H-perfluorodecyl acrylate, and the remaining steps are the same as Example 2.

[0069] Performance Testing

[0070] The adhesive obtained in the embodiment and the comparative example was mixed with water in a mass percentage of 78%:22% to obtain a slurry, and the performance of the slurry was tested:

[0071] Water bleeding rate: Stir the prepared slurry evenly and pour it into a 500ml beaker and let it stand for 1.5 hours. Use a syringe to suck out the slurry water, read the precipitated water value, and calculate it according to the following formula:

[0072]

[0073] Setting time: The setting time of the filling slurry was tested according to GB / T1346-2011. The test results are shown in Table 1.

[0074] Filling body performance test:

[0075] Compressive strength: According to GB / T 4111-2013, the samples obtained in the examples and comparative examples were mixed with water, poured into a blender and stirred for 5 minutes, and then poured into a mold with a specification of 70.7 mm × 70.7 mm × 70.7. After indoor curing and standing for 24 hours, the specimens were removed from the mold and placed in a constant temperature and humidity curing box (temperature 20°C ± 2°C, humidity 90% ± 5%) for curing. The test pieces were tested after 3 days and 28 days of curing. Three parallel test pieces were prepared for each test and tested using a YAW-3000B strength testing machine. The average value was taken as the final strength. The test results are shown in Table 1.

[0076] Heavy metal solidification performance: According to GB 5085.7-2019 "Hazardous Waste Identification Standard", the leaching toxicity test was carried out on the sample cured for 28 days using the leaching toxin leaching method, sulfuric acid and nitric acid method. In the experiment, concentrated sulfuric acid and concentrated nitric acid were added in a mass ratio of 2:1, and diluted with ordinary water to maintain the pH of the leachate at 3.2±0.05. When the leaching time reached 60 days, the leachate was filtered and collected through a 0.65μm filter, and the heavy metal leaching concentration was analyzed by inductively coupled plasma mass spectrometry, and compared and evaluated with the national standard. The national standard requires that Cu should not exceed 100μg / ml and Mn should not exceed 5μg / ml.

[0077] Table 1 Performance test results

[0078]

[0079]

[0080] Data Analysis:

[0081] The fly ash gangue cement for coal mines of the present invention has good fluidity after being mixed with water to form slurry, is convenient for pipeline transportation, and has a short setting time. The filling blocks obtained by curing the slurry have excellent compressive strength and heavy metal solidification ability.

[0082] It can be seen from Example 2 and Comparative Examples 1 and 2 that the present invention improves the compressive strength and heavy metal solidification performance of the filling block by adding sodium alginate during the preparation of the modified fly ash. This is mainly because, on the one hand, sodium alginate itself has certain adsorption properties and can fix some heavy metal ions. On the other hand, during the grafting process, part of the polyacrylamide and fluorine chains are first grafted to the surface of the sodium alginate microspheres and then grafted to the surface of the fly ash, so that the effective grafting density of the polyacrylamide and fluorine chains is significantly increased, further improving the ability to solidify metal ions. At the same time, the microspheres form a three-dimensional network structure on the surface of the fly ash. This structure not only wraps the fly ash particles and the heavy metal ions adsorbed on their surface, but also fills the gaps between the particles, thereby improving the overall density of the material, reducing the migration path of the heavy metal ions, and reducing the possibility of their dissolution and release.

[0083] It can be seen from Example 2 and Comparative Examples 1, 2, and 3 that the present invention grafts polyacrylamide, sodium alginate, and trifluoroethyl acrylate onto the surface of fly ash during the preparation of modified fly ash. Compared with direct mixing, the polyacrylamide, sodium alginate, and trifluoroethyl acrylate can be more evenly distributed on the surface of fly ash, ensuring that each particle is effectively protected, thereby improving the immobilization effect of the overall material. It not only enhances the physical barrier effect, but also fixes heavy metal ions through a variety of chemical mechanisms, thereby greatly improving the ability to fix heavy metal ions. Moreover, the uniform distribution improves the overall density of the material to a certain extent, thereby improving the compressive strength of the filling body.

[0084] It can be seen from Example 2 and Comparative Example 4 that the present invention uses modified substances with longer fluorine chains, which improves the compressive strength and heavy metal curing performance of the filler to a certain extent. On the one hand, the fluorine chain can enhance the hydrophobicity of the material, thereby reducing the penetration of rainwater and groundwater into the filler block. On the other hand, the longer fluorine side chains can be entangled with each other, so that the compressive strength of the filler block is improved to a certain extent.

[0085] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A fly ash gangue cement for coal mines, characterized in that: The raw materials include the following parts by weight: 50-60 parts of coal gangue, 10-15 parts of cement, 25-35 parts of fly ash, 5-10 parts of modified fly ash, 4-7 parts of activator, and 1-5 parts of water reducer; The preparation steps of the modified fly ash are as follows: S1: removing impurities from fly ash to obtain pretreated fly ash; S2: Mix the pretreated fly ash, hydrogen peroxide and concentrated sulfuric acid, stir them evenly, let them stand until the gas is completely released, filter them, wash them and dry them to obtain hydroxylated fly ash; S3: Mix and stir the hydroxylated fly ash and anhydrous ethanol, adjust the pH to 4.5-5, then add the silane coupling agent KH-570, react at 90-100°C for 12-14 hours, filter, wash, and dry to obtain olefinated fly ash; S4: Sodium alginate is dissolved in deionized water at 50°C, followed by the addition of olefinated fly ash, polyacrylamide, trifluoroethyl acrylate and N,N-methylenebis(acrylamide). After ultrasonic homogenization, an initiator is added, and the fly ash is modified by reacting at 60-65°C for 3-4 hours, separation, washing, drying, crushing and screening.

2. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The coal gangue is composed of coal gangue fine aggregate and coal gangue coarse aggregate in a weight ratio of 1:

1.

3. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The cement is ordinary Portland cement with a PO3 of 2.

5.

4. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The particle size of the fly ash is 10-100 μm.

5. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The activator is a mixture of Na2SiO3, Na2SO4 and NaCl in a weight ratio of 1:2:

3.

6. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The water reducer is one of lignin sulfonate water reducer, naphthalene water reducer, polycarboxylic acid water reducer, melamine water reducer or aminosulfonate water reducer.

7. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The usage ratio of the pretreated fly ash, hydrogen peroxide and concentrated sulfuric acid in step S2 is 40-50g:50-60ml:50-60ml.

8. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The weight ratio of the hydroxylated fly ash, silane coupling agent KH-570 and anhydrous ethanol in step S3 is 30-40g:10-15g:300-500g.

9. The fly ash and gangue cement for coal mines according to claim 1, characterized in that: The weight ratio of the olefinated fly ash, polyacrylamide, trifluoroethyl acrylate, N,N-methylenebis(acrylamide), sodium alginate, initiator and deionized water in step S4 is 30-40g:20-25g:1-3g:1-5g:10-15g:0.03-0.05g:200-300g.

10. A method for preparing fly ash and gangue cement for coal mines according to any one of claims 1 to 9, characterized in that: The following steps are involved: The raw materials are mixed in proportion and stirred evenly to obtain fly ash gangue cement solid for coal mines.

Images