Solid waste-based high-fluidity filling material and preparation method thereof

Abstract

The application provides a solid waste-based high-fluidity filling material and a preparation method thereof. The solid waste-based filling material comprises 40-60 parts of Bayer red mud, 40-60 parts of fly ash, 10-20 parts of desulfurization gypsum, 3-5 parts of a pumping agent, 30-60 parts of water, and the pumping agent is a compounded product of an organic silicon polycarboxylic acid water reducing agent, a polymaleic acid and a water-soluble cellulose at a mass ratio of 3-5:3-5:10. The organic silicon polycarboxylic acid water reducing agent is copolymerized from an unsaturated carboxylic acid monomer, a polyethylene glycol monoallyl ether and an unsaturated silane monomer at a mass ratio of 1.5-2:2-4:0.8-1 in the presence of a chain transfer agent. The silane monomer forms a hydrophobic region, and through the balance of the hydrophilic and hydrophobic region structure, the electrostatic repulsion between the solid waste gel particles with the water reducing agent adsorbed on the surface is enhanced, the occurrence of the solid waste gel particles wrapping the water reducing agent is prevented, and the slurry fluidity and the filling material strength are improved.

Description

Technical Field

[0001] This invention belongs to the field of filling material technology, specifically relating to a solid waste-based filling material and its preparation method. Background Technology

[0002] my country has a vast territory, abundant mineral resources, and a large population, making it a major energy producer and consumer. The tunnels, goafs, and rock fissures left after resource extraction are depleted, posing potential threats to geological stability. When the overlying rock mass shifts under gravity and stress, it can cause strong surface movement, potentially leading to surface subsidence and persistent mine-related tremors. Backfilling and managing goafs can reduce mine safety risks, improve resource recovery and utilization rates, decrease the demand for new resources, and promote sustainable mine development.

[0003] Based on different conveying technologies, backfilling methods for goaf areas can currently be divided into hydraulic backfilling, dry backfilling, and cemented backfilling. Cemented backfilling, due to its low operating cost, good mechanical properties, and mature technology, has been widely used. Grouting cemented backfill materials are highly fluid backfill materials that can self-fill and form a self-compacting structure through their own weight or minimal vibration. They have low strength requirements, therefore, industrial solid waste alkali-activated cementitious materials rich in Si, Al, and Ca can be used as backfill materials, such as red mud, coal gangue, fly ash, and slag. These materials have the advantages of low cost and environmental friendliness, possessing significant social and economic benefits. For example, patent CN102101788B discloses a red mud-based fluid expansion backfill material, and CN111393097B discloses a Bayer process red mud-based backfill material and its preparation method.

[0004] The above technologies utilize red mud and fly ash as the main cementing materials for backfilling, achieving green utilization of solid waste and reducing the cost of backfilling materials. However, the pH of the red mud leachate can reach 12-14, and its alkali-activated cementitious reaction significantly increases the viscosity of the slurry, weakens its fluidity, and easily leads to pipe blockage. In addition, red mud and fly ash have a large specific surface area, and slurries containing red mud and fly ash are in a highly alkaline environment. The interaction between the solid waste cementing particles and the anionic water-reducing agent is stronger. The water-reducing agent is easily encapsulated by the solid waste cementing particles, making it difficult to contact water, resulting in an insignificant water-reducing effect, deteriorated slurry fluidity, and unoptimized strength.

[0005] Therefore, it is necessary to develop a solid waste-based backfill material that can ensure optimal mechanical properties and excellent slurry flowability. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-flowability solid waste backfill material and its preparation method. The backfill material contains an organosilicon polycarboxylate superplasticizer copolymerized from carboxylic acid monomers, polyethylene glycol monoallyl ether, and silane monomers. The silane monomer segments increase the hydrophobic region while simultaneously increasing the charge density of the hydrophilic region. Through this balance of hydrophilic and hydrophobic region structures, the electrostatic repulsion between solid waste gel particles with superplasticizer adsorbed on their surfaces is enhanced, preventing the solid waste gel particles from encapsulating the superplasticizer and improving the slurry flowability and the strength of the backfill material. Furthermore, under the combined action of hydrophilic and hydrophobic groups, a thick solvated water film forms on the surface of particles such as red mud, further reducing the viscosity between particles and improving the slurry flowability.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] A high-flowability backfill material for solid waste includes the following raw materials in parts by weight: 40-60 parts Bayer red mud, 40-60 parts fly ash, 10-20 parts desulfurized gypsum, 3-5 parts pumping agent, and 30-60 parts water. The pumping agent is a compound of organosilicon polycarboxylate superplasticizer, polymaleic acid, and water-soluble cellulose in a mass ratio of 3-5:3-5:10. The organosilicon polycarboxylate superplasticizer is copolymerized from unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether, and unsaturated silane monomers in a mass ratio of 1.5-2:2-4:0.8-1 in the presence of a chain transfer agent.

[0009] The unsaturated carboxylic acid monomer is selected from one or a combination of two or more of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and itaconic acid.

[0010] The number-average molecular weight of the polyethylene glycol monoallyl ether is 1500-2400.

[0011] The unsaturated silane monomer is selected from one or a combination of two or more of triisopropyl acrylate, acryloyloxytrimethylsilane, and acryloyloxymethyltrimethylsilane.

[0012] Specifically, the organosilicon polycarboxylate superplasticizer is prepared by a method comprising the following steps:

[0013] The polymer was obtained by aqueous free radical polymerization under an inert atmosphere using unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether, and unsaturated silane monomers as polymerization monomers, initiated by an oxidation / reduction system initiator, and under the action of a chain transfer agent.

[0014] The polymerization temperature is 30-60℃, and the polymerization reaction time is 1-3 hours. The polymerizable monomer has a mass fraction of 40-60 wt% in the aqueous solution. In the oxidation / reduction system, the amount of reducing agent is 0.5-1 wt% of the sum of the mass of the carboxylic acid monomer, polyethylene glycol monoallyl ether, and silane monomer, and the reducing agent is selected from one or a combination of two or more of ascorbic acid, sodium sulfite, sodium hypophosphite, glucose, and sodium formaldehyde sulfoxylate. The amount of oxidizing agent is 0.5-1 wt% of the sum of the mass of the carboxylic acid monomer, polyethylene glycol monoallyl ether, and silane monomer, and is selected from one or a combination of two or more of hydrogen peroxide, ammonium persulfate, and potassium persulfate. The amount of chain transfer agent is 0.3-0.5 wt% of the sum of the mass of the carboxylic acid monomer, polyethylene glycol monoallyl ether, and silane monomer, and is selected from one or a combination of two or more of mercaptoacetic acid, 3-mercaptopropionic acid, and mercaptoethanol.

[0015] Due to the presence of hydrophobic silane monomers, although the hydration film formed by using organosilicon polycarboxylate superplasticizer alone can improve the fluidity of the slurry, if the hydration film is too thick and the particles wrapped under the film are large and uneven, bleeding and sedimentation will occur, reducing the strength of the consolidated filling material. Polymaleic acid has the effect of chelating calcium ions, retarding and reducing viscosity, and can also work synergistically with organosilicon polycarboxylate superplasticizer to form uniformly dispersed and uniform solvated particles. With the synergistic effect of water-soluble cellulose as a water-retaining agent, the mechanical properties can be optimized while ensuring good fluidity of the slurry.

[0016] The relative molecular mass of the polymaleic acid is 600-1000.

[0017] The water-soluble cellulose has a weight-average molecular weight of 100,000 to 500,000 and is selected from one or a combination of two or more of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0018] The fly ash is selected from one or a combination of two of Grade I fly ash and Grade II fly ash.

[0019] The present invention also provides a method for preparing the above-mentioned solid waste-based backfill material, comprising the following steps:

[0020] Mix Bayer red mud, fly ash, and desulfurized gypsum evenly to obtain mixture 1. Mix pumping agent and water evenly to obtain mixture 2. Mix mixture 1 and mixture 2 evenly to obtain solid waste base filling material.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The filling material of this invention contains an organosilicon polycarboxylate superplasticizer copolymerized from carboxylic acid monomers, polyethylene glycol monoallyl ether, and silane monomers. The silane monomer segments increase both the hydrophobic and hydrophilic regions, thereby balancing these hydrophilic and hydrophobic regions. This balance enhances the electrostatic repulsion between solid waste gel particles with superplasticizer adsorbed on their surfaces, preventing the superplasticizer from being trapped within the gel particles and improving slurry flowability and filling material strength. Furthermore, the combined action of hydrophilic and hydrophobic groups forms a thick solvated water film on the surface of particles such as red mud, further reducing interparticle viscosity and improving slurry flowability. For example, the initial flowability is above 350 mm, and the 30-minute flowability retention value is above 320 mm.

[0023] The inventors discovered that the synergistic effect of organosilicon polycarboxylate superplasticizer, polymaleic acid, and water-soluble cellulose can optimize the mechanical properties while ensuring good fluidity of the slurry. Attached Figure Description

[0024] Figure 1 SEM images and energy dispersive spectroscopy (EDS) scans of the solid waste-based backfill material from Example 1;

[0025] Figure 2 The image shows the XRD pattern of the solid waste-based filling material in Example 1. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0027] Polyethylene glycol monoallyl ether 2400 (number average molecular weight 2400) and polyethylene glycol monoallyl ether 1500 (number average molecular weight 1500) were both purchased from Haian Petrochemical Plant in Jiangsu Province.

[0028] Polymaleic acid with relative molecular masses of 600 and 1000 was purchased from Sinochem Chemicals.

[0029] Hydroxyethyl cellulose with a weight-average molecular weight of 122,000 was purchased from Shanghai Zhenzhun Biotechnology Co., Ltd.

[0030] Bayer red mud and Class I fly ash were purchased from Shanxi Senze Energy Technology Group Co., Ltd.; desulfurization gypsum was purchased from Shangqiu Tianyuan Desulfurization Gypsum Co., Ltd. The oxide composition of the above three raw materials is shown in Table 1.

[0031] Table 1 Composition of raw material oxides

[0032] raw material <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> CaO <![CDATA[SO3]]> <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> MgO <![CDATA[P2O5]]> Bayer red mud 29.34 23.43 16.013 11.48 1.07 4.39 0.984 11.34 0.74 0.41 Class I fly ash 37.45 47.17 4.00 4.43 1.08 2.65 0.61 0.30 0.39 1.14 Desulfurized gypsum 0.46 2.03 0.41 47.64 48.50 0.04 0.07 0.11 0.56 -

[0033] Example 1

[0034] 1) Under a nitrogen atmosphere, 200g of acrylic acid, 200g of polyethylene glycol monoallyl ether 2400, 80g of triisopropyl silicone acrylate, and 1.4g of potassium persulfate were added to 720g of water. The mixture was heated to 60℃ and the monomer solution was mixed evenly. After 30 minutes, a solution consisting of 2.8g of ascorbic acid, 0.84g of mercaptoethanol, and 3.36g of water was added dropwise. The polymerization reaction was carried out for 3 hours. After the reaction was completed, the pH was adjusted to 7 with sodium hydroxide, and the water was removed by vacuum distillation to obtain an organosilicon polycarboxylate superplasticizer with a weight-average molecular weight of 124,000.

[0035] 2) Mix 60g Bayer red mud, 40g Grade I fly ash and 10g desulfurized gypsum evenly to obtain mixture 1. Mix 5g of pumping agent composed of organosilicon polycarboxylate superplasticizer, polymaleic acid with a relative molecular mass of 1000 and hydroxyethyl cellulose in a mass ratio of 5:5:10 and 35g water evenly to obtain mixture 2. Mix mixture 1 and mixture 2 evenly to obtain solid waste-based high-flowability filling material.

[0036] Example 2

[0037] The rest is the same as in Example 1, except that in step 1), polyethylene glycol monoallyl ether 1500 is used instead of polyethylene glycol monoallyl ether 2400, with a weight-average molecular weight of 127,000.

[0038] Example 3

[0039] The rest is the same as in Example 1, except that in step 1), the amount of triisopropylsilyl acrylate used is 100g and the weight-average molecular weight is 122,000.

[0040] Example 4

[0041] The rest is the same as in Example 1, except that in step 1), 150g of acrylic acid, 400g of polyethylene glycol monoallyl ether 2400, and 100g of triisopropylsilyl acrylate have a weight-average molecular weight of 122,000.

[0042] Example 5

[0043] The rest is the same as in Example 1, except that in step 2), the amount of pumping agent used is 3g.

[0044] Example 6

[0045] The rest is the same as in Example 1, except that in step 2), the pumping agent is a compound of organosilicon polycarboxylate superplasticizer, polymaleic acid with a relative molecular mass of 1000, and hydroxyethyl cellulose in a mass ratio of 3:5:10.

[0046] Example 7

[0047] The rest is the same as in Example 1, except that in step 2), the pumping agent is a compound of organosilicon polycarboxylate superplasticizer, polymaleic acid with a relative molecular mass of 1000, and hydroxyethyl cellulose in a mass ratio of 5:3:10.

[0048] Example 8

[0049] The rest is the same as in Example 1, except that in step 2), 40g of Bayer red mud, 60g of Grade I fly ash and 10g of desulfurized gypsum are mixed evenly to obtain mixture 1, 3g of pumping agent composed of organosilicon polycarboxylate superplasticizer, polymaleic acid with a relative molecular mass of 600 and hydroxyethyl cellulose in a mass ratio of 5:5:10 and 35g of water are mixed evenly to obtain mixture 2, and mixture 1 and mixture 2 are mixed evenly to obtain solid waste-based high-flowability filling material.

[0050] Comparative Example 1

[0051] The rest is the same as in Example 1, except that an equal mass of BASF polycarboxylate superplasticizer RHEOPLUS 420 is used instead of silicone polycarboxylate superplasticizer.

[0052] The solid waste-based backfill materials prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0053] 1. Flowability: Refer to Appendix A.0.2 of the Technical Specification for Cement-based Grouting Materials GB / T 50448-2008 for flowability test. The initial spread is required to be ≥290mm and the 30min flowability retention value is required to be ≥260mm. Record the initial flowability and the 30min flowability retention value.

[0054] 2. Bleeding performance: The bleeding test shall be conducted in accordance with the bleeding test standard in GB / T 50080-2002 Standard for Test Methods of Performance of Concrete Mixtures.

[0055] 3. Compressive strength: Tested in accordance with standard GB / T 50081-2002 Practical Standard for Test Methods of Mechanical Properties of Ordinary Concrete.

[0056] Table 2 Performance Test Results

[0057]

[0058] Figure 1The image shows the SEM image of the filling material in Example 1. Through analysis of the microstructure and elemental composition of the solid waste-based high-flowability filling material, it can be seen that a type of target product with characteristic sheet-like and cluster-like structures was generated. The target product is mainly composed of oxides of elements such as Ca, Al, Si, K and Na, and Al and Si elements overlap significantly, as do Ca and Na elements. This indicates that Example 1 generated an aluminosilicate structure and combined with sodium to form C(N)-SH (sodium-containing hydrated calcium silicate), CASH (hydrated calcium aluminosilicate), and CSH (hydrated calcium silicate).

[0059] As can be seen from Table 2, the solid waste-based high-flowability filling material slurry prepared by the present invention has excellent flowability, and the mechanical properties of the solidified filling material are optimized.

[0060] Figure 2 The XRD pattern of the filling material in Example 1 shows that its main structure is ettringite (Ca6Al2(SO4)3(OH)). 12 ·26H2O), beryl (Na8(Al8Si) 16 O 48 )·24H2O), CASH, ettringite (Na6Ca2Al6Si6O 24 (CO3)2·12H2O and CSH. The red mud in the solid waste-based backfill material provides a high alkalinity environment for the reaction, which stimulates the activity of inert silicon and aluminum oxides in the feedstock. The more reactive silicon and aluminum react with Ca... 2+ and OH - The reaction produces more CASH and CSH products. Simultaneously, the aluminosilicate structure in the OH group... - Under the influence of depolymerization into AlO 2- The process consumes CaSO4·2H2O and forms more ettringite, thus promoting the development of backfill materials. Among them, ettringite, CASH, and CSH are typical hydration products that make major contributions to the strength of solid waste backfill materials.

[0061] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A solid waste-based high-flowability filling material, characterized in that, The raw materials include the following parts by weight: 40-60 parts Bayer red mud, 40-60 parts fly ash, 10-20 parts desulfurized gypsum, 3-5 parts pumping agent, and 30-60 parts water. The pumping agent is a compound of organosilicon polycarboxylate superplasticizer, polymaleic acid, and water-soluble cellulose in a mass ratio of 3-5:3-5:

10. The organosilicon polycarboxylate superplasticizer is copolymerized from unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether, and unsaturated silane monomers in a mass ratio of 1.5-2:2-4:0.8-1 in the presence of a chain transfer agent.

2. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The unsaturated carboxylic acid monomer is selected from one or a combination of two or more of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and itaconic acid.

3. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The number-average molecular weight of the polyethylene glycol monoallyl ether is 1500-2400.

4. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The unsaturated silane monomer is selected from one or a combination of two or more of triisopropyl acrylate, acryloyloxytrimethylsilane, and acryloyloxymethyltrimethylsilane.

5. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The organosilicon polycarboxylate water-reducing agent is prepared by a method comprising the following steps: The polymer was obtained by aqueous free radical polymerization under an inert atmosphere using unsaturated carboxylic acid monomers, polyethylene glycol monoallyl ether, and unsaturated silane monomers as polymerization monomers, initiated by an oxidation / reduction system initiator, and under the action of a chain transfer agent.

6. The solid waste-based high-flowability filling material according to claim 5, characterized in that, The polymerization temperature is 30-60℃, and the polymerization reaction time is 1-3h; the mass fraction of the monomer in the aqueous solution is 40-60wt%; the amount of reducing agent in the oxidation / reduction system is 0.5-1wt% of the total mass of the unsaturated carboxylic acid monomer, polyethylene glycol monoallyl ether, and unsaturated silane monomer, and the reducing agent is selected from one or more combinations of ascorbic acid, sodium sulfite, sodium hypophosphite, glucose, and sodium formaldehyde sulfoxylate; the amount of oxidizing agent is 0.5-1wt% of the total mass of the unsaturated carboxylic acid monomer, polyethylene glycol monoallyl ether, and unsaturated silane monomer, and the oxidizing agent is selected from one or more combinations of hydrogen peroxide, ammonium persulfate, and potassium persulfate; the amount of chain transfer agent is 0.3-0.5wt% of the total mass of the unsaturated carboxylic acid monomer, polyethylene glycol monoallyl ether, and unsaturated silane monomer, and is selected from one or more combinations of mercaptoacetic acid, 3-mercaptopropionic acid, and mercaptoethanol.

7. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The relative molecular mass of the polymaleic acid is 600-1000.

8. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The water-soluble cellulose has a weight-average molecular weight of 100,000 to 500,000 and is selected from one or a combination of two or more of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

9. The solid waste-based high-flowability filling material according to claim 1, characterized in that, The fly ash is selected from one or a combination of two of Grade I fly ash and Grade II fly ash.

10. A method for preparing the solid waste-based high-flowability filling material according to any one of claims 1-9, characterized in that, Includes the following steps: Mix Bayer red mud, fly ash, and desulfurized gypsum evenly to obtain mixture 1. Mix pumping agent and water evenly to obtain mixture 2. Mix mixture 1 and mixture 2 evenly to obtain solid waste-based high-flowability filling material.

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