Alkali-activated solid waste-based backfill material and preparation method thereof

Abstract

This invention discloses an alkali-activated solid waste-based backfill material. The backfill material comprises the following components: a solid waste-based composite material, an additive, sodium silicate, and water. The solid waste-based composite material comprises the following components: 60-75 parts of fine construction waste powder; 10-20 parts of calcined coal gangue powder; 5-10 parts of desulfurized gypsum powder; 5-15 parts of municipal solid waste incineration ash powder; and 5-15 parts of alkali residue. The mass percentage of sodium silicate in the solid waste-based composite material is 1-5%; and the mass percentage of water is 20-30%. This application uses the solid waste-based composite material as the base material, uniformly mixing it with the additive, sodium silicate, and water. The combined effect of these materials produces a self-leveling, self-compacting backfill material with controllable strength and hardening time. This application solves the problems of insufficient utilization and consumption of solid waste in existing technologies, opening up new areas for the resource utilization of solid waste.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment, and specifically relates to alkali-activated solid waste-based backfill materials and their preparation methods. Background Technology

[0002] If my country were to dispose of its large amount of solid waste through resource utilization, a huge market for solid waste resource utilization would be created.

[0003] Due to the unique characteristics of the industry, whether it is the processing of raw materials into building materials, the recycling of these building materials after their life cycle, or the resource utilization of bulk industrial solid waste such as tailings, there are bottlenecks in improving the utilization rate. These bottlenecks include high energy consumption, poor performance, narrow product applications, and high costs in the resource utilization process, which restrict the development of the resource utilization of solid waste in the building materials industry.

[0004] Currently, the backfilling of pipe trenches, trenches, cavities, and foundation trenches is mostly carried out by layered soil filling and compaction. The filling quality is significantly affected by factors such as the quality of the filling soil, the thickness of each layer, and the compaction method. It is difficult to guarantee the filling quality at corners and irregular shapes.

[0005] During the processing of construction waste into aggregates, a large amount of fine construction waste powder with a particle size of less than 0.25mm is generated in the dust collection system, vibrating screen residue, and aggregate washing pool of the processing plant. Compared with the recycled coarse and fine aggregates from construction waste, the resource utilization rate of fine construction waste powder is not high. Coal gangue is a solid waste discharged during the coal mining and washing process. It is a blackish-gray rock with a low carbon content and harder than coal that is associated with coal seams during the coal formation process. It not only occupies land but can also spontaneously combust, polluting the air or causing fires. Waste incineration ash is the main product after waste incineration, and there are problems of insufficient utilization and underconsumption of waste incineration ash. In addition, in industrial production, solid wastes such as desulfurization gypsum and alkali slag are directly dumped in the open or landfilled, which poses problems of occupying land, secondary pollution, and insufficient utilization. Summary of the Invention

[0006] This invention provides an alkali-activated solid waste-based backfill material and its preparation method, in order to solve the problems of insufficient utilization and inadequate consumption of solid waste in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: an alkali-activated solid waste-based backfill material, wherein the backfill material comprises the following components: a solid waste-based composite material, an additive, sodium silicate, and water; wherein the solid waste-based composite material comprises the following components: 60-75 parts of fine powder from construction waste; 10-20 parts of calcined coal gangue powder; 5-10 parts of desulfurized gypsum powder; 5-15 parts of municipal solid waste incineration ash powder; and 5-15 parts of alkali residue.

[0008] Furthermore, the mass percentage of sodium silicate in the solid waste-based composite material is 1-5%; the mass percentage of water in the solid waste-based composite material is 20-30%; the admixture is an anti-clay polycarboxylate high-performance water-reducing agent and calcium formate, the mass percentage of the anti-clay polycarboxylate high-performance water-reducing agent in the solid waste-based composite material is 0.05%-0.1%; the mass percentage of calcium formate in the solid waste-based composite material is 0.5%-2.5%.

[0009] Furthermore, the clay-resistant polycarboxylate superplasticizer is in powder form.

[0010] Furthermore, the particle size of the fine powder from construction waste is less than 0.25 mm.

[0011] Furthermore, the calcined coal gangue powder is the product of coal gangue after calcination at 800℃-1000℃, followed by grinding and air classification, with a particle size of less than 0.075mm.

[0012] Furthermore, the municipal solid waste incineration ash powder is a mixture of the residue obtained after recovering metals from the bottom ash produced by municipal solid waste incineration plants, which is then matured in an open environment and sieved, and municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

[0013] This invention also provides a method for preparing alkali-activated solid waste-based backfill material, the method comprising the following steps:

[0014] S1. Weigh the dry construction waste fine powder, calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue according to the proportion and put them into a powder mixer for mixing to obtain solid waste-based composite material.

[0015] S2. Fill the barrel with an appropriate amount of water, and add calcium formate, anti-clay polycarboxylate superplasticizer and sodium silicate solution into the barrel in sequence according to the proportion, and stir evenly.

[0016] S3. Put the solid waste-based composite material into the mixer, add the mixed solution in the material cylinder into the mixer, and stir evenly to obtain the finished product of alkali-activated solid waste-based backfill material.

[0017] Furthermore, the mixing time in step S1 is at least 3 minutes.

[0018] Furthermore, the stirring time in step S2 is at least 3 minutes.

[0019] Furthermore, the stirring time in step S3 is 3-5 minutes.

[0020] The beneficial effects of this invention are reflected in:

[0021] 1) The alkali-activated solid waste backfill material disclosed in this invention uses fine powder of construction waste, calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue as basic raw materials. These materials are uniformly mixed with anti-clay polycarboxylate superplasticizer (powder), calcium formate, sodium silicate, and water. By adjusting the proportions of each raw material, the combined effect of each raw material is achieved.

[0022] 2) The alkali-activated solid waste backfill material does not use traditional cementitious materials such as cement and lime during preparation. Instead, it activates the mineral activity of calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue through alkaline activators, enabling the material to achieve the expected unconfined compressive strength. This saves costs, is energy-saving and environmentally friendly, and provides a new direction for the resource utilization of solid waste.

[0023] 3) The present invention does not use natural aggregates in the preparation of alkali-activated solid waste backfill material, thus reducing the use of natural resources.

[0024] 4) The alkali-activated solid waste backfill material prepared by this invention has moderate and adjustable strength, which is convenient for secondary excavation; it is self-leveling and can fill narrow spaces; it is self-compacting and basically does not require compaction. It can replace traditional backfill materials, solve the problems of insufficient utilization and insufficient consumption of solid waste in the existing technology, open up new fields for the resource utilization of solid waste, and improve the utilization rate and efficiency of industrial solid waste such as construction waste, coal gangue, desulfurization gypsum, municipal solid waste incineration ash, and alkali residue.

[0025] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention; the main objects and other advantages of the invention may be realized and obtained by means of the embodiments particularly pointed out in the description. Detailed Implementation

[0026] This invention provides an alkali-activated solid waste-based backfill material, comprising a solid waste-based composite material, additives, sodium silicate, and water. The solid waste-based composite material specifically comprises the following components by weight: 60-75 parts fine powder of construction waste; 10-20 parts calcined coal gangue powder; 5-10 parts desulfurized gypsum powder; 5-15 parts municipal solid waste incineration ash powder; and 5-15 parts alkali residue.

[0027] The mass percentage of sodium silicate in the solid waste-based composite material is 1-5%; the mass percentage of water in the solid waste-based composite material is 20-30%; the admixtures are anti-clay polycarboxylate high-performance water-reducing agent (powder) and calcium formate, with the anti-clay polycarboxylate high-performance water-reducing agent (powder) accounting for 0.05%-0.1% of the solid waste-based composite material; and the calcium formate accounting for 0.5%-2.5% of the solid waste-based composite material.

[0028] Among them, construction waste fine powder refers to fine powder with a particle size of less than 0.25 mm collected in the dust collection system, vibrating screen residue, and aggregate washing pool during the aggregate processing of construction waste, and its main components are brick slag and concrete slag; calcined coal gangue micro powder is the product of coal gangue after calcination at 800℃-1000℃ and subsequent grinding and air classification, with a particle size of less than 0.075 mm; desulfurized gypsum is commercially available desulfurized gypsum powder, with the main component being CaSO4·1 / 2H2O; municipal solid waste incineration ash micro powder is the residue obtained after the bottom ash from municipal solid waste incineration plants has been recovered and matured in an open environment and screened, mixed with municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

[0029] Among them, the alkali residue is commercially available alkali residue, the sodium silicate is commercially available sodium silicate powder, and the additives are commercially available anti-clay type polycarboxylate high-performance water-reducing agent (powder) and calcium formate.

[0030] Example 1

[0031] This embodiment provides an alkali-activated solid waste-based backfill material, the raw materials of which include a solid waste-based composite material, additives, sodium silicate, and water. The mass ratio of each component in the solid waste-based composite material is as follows:

[0032]

[0033] The mass percentage of sodium silicate in the solid waste-based composite material is 3%;

[0034] The mass of the clay-resistant polycarboxylate-based high-performance water-reducing agent (powder) accounts for 0.07% of the solid waste-based composite material;

[0035] Calcium formate accounts for 1.0% of the total mass of the solid waste-based composite material.

[0036] The water accounts for 25% of the mass of the solid raw material.

[0037] Furthermore, the fine powder of construction waste is fine powder with a particle size of less than 0.25mm collected in the dust collection system, vibrating screen residue, aggregate washing pool, etc. during the aggregate processing of construction waste, and its main components are brick slag and concrete slag.

[0038] The calcined coal gangue powder is the product of coal gangue after calcination at 800℃-1000℃, followed by grinding and air classification, with a particle size of less than 0.075mm.

[0039] The desulfurized gypsum is commercially available desulfurized gypsum powder, whose main component is CaSO4·1 / 2H2O.

[0040] The municipal solid waste incineration ash is a mixture of the residue obtained after recovering metals from the bottom ash produced by the municipal solid waste incineration plant, which is then matured in an open environment and sieved, and municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

[0041] The alkaline residue is commercially available alkaline residue.

[0042] The sodium silicate mentioned is commercially available sodium silicate powder.

[0043] The admixtures are commercially available anti-clay polycarboxylate high-performance water-reducing agents (powder) and calcium formate.

[0044] Example 2

[0045] This embodiment provides an alkali-activated solid waste-based backfill material, the raw materials of which include a solid waste-based composite material, additives, sodium silicate, and water. The mass ratio of each component in the solid waste-based composite material is as follows:

[0046]

[0047] The mass percentage of sodium silicate in the solid waste-based composite material is 4%;

[0048] The mass of the clay-resistant polycarboxylate-based high-performance water-reducing agent (powder) accounts for 0.1% of the solid waste-based composite material;

[0049] Calcium formate accounts for 2.0% of the total mass of the solid waste-based composite material.

[0050] The water accounts for 20% of the mass of the solid raw material.

[0051] Furthermore, the fine powder of construction waste is fine powder with a particle size of less than 0.25mm collected in the dust collection system, vibrating screen residue, aggregate washing pool, etc. during the aggregate processing of construction waste, and its main components are brick slag and concrete slag.

[0052] The calcined coal gangue powder is the product of coal gangue after calcination at 800℃-1000℃, followed by grinding and air classification, with a particle size of less than 0.075mm.

[0053] The desulfurized gypsum is commercially available desulfurized gypsum powder, whose main component is CaSO4·1 / 2H2O.

[0054] The municipal solid waste incineration ash is a mixture of the residue obtained after recovering metals from the bottom ash produced by the municipal solid waste incineration plant, which is then matured in an open environment and sieved, and municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

[0055] The alkaline residue is commercially available alkaline residue.

[0056] The sodium silicate mentioned is commercially available sodium silicate powder.

[0057] The admixtures are commercially available anti-clay polycarboxylate high-performance water-reducing agents (powder) and calcium formate.

[0058] Example 3

[0059] This embodiment provides an alkali-activated solid waste-based backfill material, the raw materials of which include a solid waste-based composite material, additives, sodium silicate, and water. The mass ratio of each component in the solid waste-based composite material is as follows:

[0060]

[0061] The mass percentage of sodium silicate in the solid waste-based composite material is 2%;

[0062] The mass of the clay-resistant polycarboxylate-based high-performance water-reducing agent (powder) accounts for 0.05% of the solid waste-based composite material;

[0063] Calcium formate accounts for 0.5% of the total mass of the solid waste-based composite material.

[0064] The water accounts for 30% of the mass of the solid raw material.

[0065] Furthermore, the fine powder of construction waste is fine powder with a particle size of less than 0.25mm collected in the dust collection system, vibrating screen residue, aggregate washing pool, etc. during the aggregate processing of construction waste, and its main components are brick slag and concrete slag.

[0066] The calcined coal gangue powder is the product of coal gangue after calcination at 800℃-1000℃, followed by grinding and air classification, with a particle size of less than 0.075mm.

[0067] The desulfurized gypsum is commercially available desulfurized gypsum powder, whose main component is CaSO4·1 / 2H2O.

[0068] The municipal solid waste incineration ash is a mixture of the residue obtained after recovering metals from the bottom ash produced by the municipal solid waste incineration plant, which is then matured in an open environment and sieved, and municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

[0069] The alkaline residue is commercially available alkaline residue.

[0070] The sodium silicate mentioned is commercially available sodium silicate powder.

[0071] The admixtures are commercially available anti-clay polycarboxylate high-performance water-reducing agents (powder) and calcium formate.

[0072] Comparative Example 1

[0073] This comparative example provides an alkali-activated solid waste-based backfill material to be compared with Example 1. Its raw materials include solid waste-based composite material, additives, sodium silicate and water. In the solid waste-based composite material, the mass ratio of each component is 4% alkali residue, and the other component ratios are the same as those in Example 1.

[0074] This invention also provides a method for preparing the above-mentioned alkali-activated solid waste-based backfill material, comprising the following steps:

[0075] S1. Weigh the dry construction waste fine powder, calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue according to the proportion and put them into the powder mixer for mixing to obtain solid waste-based composite material; the mixing time shall not be less than 3 minutes.

[0076] S2. Fill the barrel with an appropriate amount of water, and add calcium formate, anti-clay polycarboxylate high-performance water-reducing agent (powder), and sodium silicate solution into the barrel in a certain proportion. Stir evenly for no less than 3 minutes.

[0077] S3. Add the solid waste-based composite material to the mixer, add the mixed solution from the material cylinder to the mixer, stir for 3-5 minutes, and after uniform mixing, obtain the alkali-activated solid waste-based backfill material product.

[0078] Comparative Example 2

[0079] This comparative example provides a cement-based backfill material to compare with Example 3. Its raw materials include cement, admixtures, fine powder of construction waste and water, and the mass ratio of each component is as follows:

[0080] Construction waste fine powder 70%;

[0081] Cement 30%.

[0082] The clay-resistant polycarboxylate-based high-performance water-reducing agent (powder) accounts for 0.05% of the mass of the cement.

[0083] Calcium formate accounts for 0.5% of the mass of the cement.

[0084] The water accounts for 30% of the mass of the solid raw material.

[0085] The cement is commercially available 32.5 slag silicate cement.

[0086] Other materials are the same as in Example 3.

[0087] The preparation method includes the following steps:

[0088] S1. Weigh dry construction waste powder and cement according to the proportion and put them into a powder mixer to mix them to obtain cement-based composite material; the mixing time shall not be less than 3 minutes.

[0089] S2. Fill the barrel with an appropriate amount of water, and add calcium formate and anti-clay polycarboxylate high-performance water-reducing agent (powder) into the barrel in proportion, stir evenly, and stir for no less than 3 minutes.

[0090] S3. Add the cement-based composite material to the mixer, add the mixed solution from the material cylinder to the mixer, stir for 3-5 minutes, and after uniform mixing, the cement-based backfill material product is obtained.

[0091] The parameters for Examples 1-3 and Comparative Examples 1-2 are as follows:

[0092] Mixing time in step S1 4 minutes 4 minutes 4 minutes 4 minutes 4 minutes Stirring time in step S2 3 minutes 3 minutes 3 minutes 3 minutes 3 minutes Stirring time in step S3 4 minutes 4 minutes 4 minutes 4 minutes 4 minutes

[0093] Performance testing

[0094] 1. The performance of the backfill materials prepared in Examples 1-3 and Comparative Examples 1-2 was tested. The unconfined compressive strength was tested according to ASTM D4832-16e1, the fluidity was tested according to ASTM D6103 / D6103M-17, and the setting time was tested according to ASTM D6024 / D6024M-16. The specific test results are shown in Table 1.

[0095] Table 1 Performance Test Results

[0096]

[0097] As can be seen from Table 1, the alkali-activated solid waste backfill material provided in this application has the following characteristics:

[0098] (1) The range of unconfined compressive strength at 3 days is 0.23-0.45 MPa, indicating high early strength; the range of unconfined compressive strength at 28 days is 1.27-2.14 MPa, which not only meets the strength required for backfill materials but also facilitates secondary excavation.

[0099] (2) The fluidity is greater than 200mm, which has good self-leveling properties and self-compacting properties, making it suitable for filling narrow spaces;

[0100] (3) The initial setting time is less than 6 hours, and the subsequent construction process can be quickly connected after backfilling to speed up the construction progress.

[0101] (4) The amount of alkali residue in Comparative Example 1 is less than 5%, the alkalinity of the mixture is weak, the working performance is significantly worse than that in Example 1, and some indicators do not meet the requirements of the indicator values.

[0102] (4) Comparative Example 2 is a cement-based backfill material, and its performance is significantly different from that of Example 3. The index does not meet the index value requirements.

[0103] 2. Leaching concentration test: The leaching concentrations of Zn, Pb, Ni, Cd, TCr, and Cu in the alkali-activated solid waste backfill material were determined by inductively coupled plasma atomic emission spectrometry. The specific test results are shown in Tables 2 and 3.

[0104] Table 2 Results of 30-day leaching concentration test

[0105]

[0106] Table 3 Results of 90-day leaching concentration test

[0107]

[0108] As can be seen from Tables 2 and 3, the alkali-activated solid waste-based backfill materials provided in this application for Examples 1-3 and Comparative Example 1 have the following characteristics: the leaching concentrations of Zn, Pb, Ni, Cd, TCr, and Cu in the 30-day and 90-day alkali-activated solid waste-based backfill materials are all far lower than the heavy metal mass concentration limits of landfill leachate pollutants, meeting the requirements of the "Standard for Pollutant Control of Municipal Solid Waste Landfills" (GB 16889-2008), and are environmentally friendly and safe; the data in Comparative Example 1 show a significant increase compared to Example 1; Comparative Example 2 is a cement-based backfill material, and basically no heavy metals were detected.

[0109] The alkali-activated solid waste backfill material provided in this application uses fine powder of construction waste, calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue as basic raw materials. These are uniformly mixed with anti-clay polycarboxylate superplasticizer (powder), calcium formate, sodium silicate, and water. By adjusting the proportions of each raw material, the combined effect of each raw material is achieved. The resulting backfill material has the strength to meet backfilling requirements and is easy to excavate in secondary excavation. It can automatically fill narrow spaces and does not require compaction.

[0110] The alkali-activated solid waste backfill material prepared in this application does not use traditional cementitious materials such as cement and lime during preparation. Instead, it activates the mineral activity of calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue through an alkaline activator. This enables the material to achieve the expected requirements in terms of unconfined compressive strength, fluidity, initial setting time, and heavy metal concentration in the leachate. This saves costs, is energy-saving and environmentally friendly, and provides a new direction for the resource utilization of solid waste.

[0111] Natural aggregates were not used in the preparation of alkali-activated solid waste backfill material. Instead, fine powder from construction waste was fully utilized, which not only solved the problem of solid waste occupying land but also reduced the use of natural resources and protected the environment.

[0112] In summary, the alkali-activated solid waste backfill material and its preparation method provided by this invention have opened up new fields for the resource utilization of solid waste, and improved the utilization rate and quality of industrial solid wastes such as coal gangue, desulfurization gypsum, municipal solid waste incineration ash, and alkali residue.

[0113] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An alkali-activated solid waste-based backfill material, characterized in that, The backfill material comprises the following components: solid waste-based composite material, additives, sodium silicate, and water; wherein the solid waste-based composite material comprises the following components: 60-75 parts of fine construction waste powder; 10-20 parts of calcined coal gangue powder; 5-10 parts of desulfurized gypsum powder; 5-15 parts of municipal solid waste incineration ash powder; 5-15 parts of alkali residue; the mass percentage of sodium silicate in the solid waste-based composite material is 1-5%; the mass percentage of water in the solid waste-based composite material is 20-30%; the additives... The additives are a clay-resistant polycarboxylate superplasticizer and calcium formate. The clay-resistant polycarboxylate superplasticizer accounts for 0.05%-0.1% of the mass of the solid waste-based composite material; the calcium formate accounts for 0.5%-2.5% of the mass of the solid waste-based composite material; the clay-resistant polycarboxylate superplasticizer is in powder form; the fine powder of construction waste has a particle size of less than 0.25 mm; the calcined coal gangue powder is the product of coal gangue after calcination at 800℃-1000℃, followed by grinding and air classification, with a particle size of less than 0.075 mm.

2. The alkali-activated solid waste-based backfill material as described in claim 1, characterized in that, The municipal solid waste incineration ash powder is a mixture of the residue obtained after the bottom ash from municipal solid waste incineration plants is recovered and matured in an open environment and then screened, and municipal solid waste incineration fly ash at a mass ratio of 5:1, with a particle size of less than 0.075 mm.

3. A method for preparing alkali-activated solid waste-based backfill material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: S1, weighing dry construction waste fine powder, calcined coal gangue powder, desulfurized gypsum powder, municipal solid waste incineration ash powder, and alkali residue according to proportion and adding them to a powder mixer for mixing to obtain a solid waste-based composite material; S2, adding an appropriate amount of water to a material cylinder, and sequentially adding calcium formate, anti-clay polycarboxylate high-performance water-reducing agent, and sodium silicate according to proportion, and stirring evenly; S3, adding the solid waste-based composite material to a mixer, adding the mixed solution from the material cylinder to the mixer, and stirring evenly to obtain the alkali-activated solid waste-based backfill material product; wherein, the mass percentage of sodium silicate in the solid waste-based composite material is 1-5%; the mass percentage of water in the solid waste-based composite material is 20-30%; the mass percentage of anti-clay polycarboxylate high-performance water-reducing agent in the solid waste-based composite material is 0.05%-0.1%; and the mass percentage of calcium formate in the solid waste-based composite material is 0.5%-2.5%.

4. The preparation method according to claim 3, characterized in that, The mixing time in step S1 is at least 3 minutes.

5. The preparation method according to claim 3, characterized in that, The stirring time in step S2 shall be at least 3 minutes.

6. The preparation method according to claim 3, characterized in that, The stirring time in step S3 is 3-5 minutes.

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