Coal gasification slag-based backfill material for replacing fluidized stabilized soil, preparation method and application

Abstract

The invention discloses a coal gasification slag-based backfill material for replacing flow-state solidified soil, a preparation method and an application, utilizes a synergistic gelling effect among three raw materials, breaks through a material strength forming mechanism of traditional flow-state solidified soil, solves the problems of multiple components and high cost of a flow-state solidified soil material in the prior art, and has the advantages of low raw material cost, low raw material cost, low raw material cost, low raw material cost and the like. And the product popularization is facilitated. The specific scheme is as follows: the coal gasification slag-based backfill material for replacing the fluidized stabilized soil comprises coal gasification slag, carbide slag and titanium gypsum, the ratio of the coal gasification slag to the carbide slag to the titanium gypsum is 6-8: 1.5-3.5: 0.5-1.5, and an alkaline activator is also added; the coal gasification slag is a slag block with a set particle size formed after slag at the bottom of a gasification furnace is cooled, the carbide slag is waste slag which takes calcium oxide as a main component after acetylene gas is obtained by hydrolyzing calcium carbide, and under the action of an exciting agent, the coal gasification slag and the carbide slag are fully activated to release polyhedrons; part of the polyhedrons form a gelling product so as to improve the early strength of the coal gasification slag-based backfill material.

Description

Technical Field

[0001] The present invention relates to the field of fluid-solidified soil, in particular to a coal gasification slag-based backfill material for replacing fluid-solidified soil, a preparation method and an application thereof. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Fluid-solidified soil is a commonly used backfill material for areas difficult to compact in earthwork projects. Traditional fluid-solidified soil is generally mainly prepared from materials such as soil and cement, thus consuming a large amount of land and cement resources. To reduce the consumption of cement, some scholars have currently used industrial solid wastes to partially replace cement as a gelling material for the preparation of fluid-solidified soil. CN119059772A discloses a new type of fluid-solidified soil and a preparation method thereof, and the raw materials include muck, ceramic sand, water, ordinary Portland cement, secondary fly ash, sulfate early strength agent, sand and gravel, industrial tail mud special and curing agent. CN118955023A discloses a fluid-solidified soil prepared by mixing saline soil, iron tailings sand, cement, slag, steel slag, fly ash, magnesium salt, activator and water reducer. Zhao Weiguo used construction waste soil as the test material and red mud and metakaolin as auxiliary gelling materials to develop a new type of low-cement fluid-solidified soil. Although these technologies can reduce the consumption of cement and soil resources, the formula is relatively complex, and the acquisition of raw materials requires transportation from multiple places, and the actual cost may be relatively high.

[0004] On the other hand, the stock of coal gasification slag reaches hundreds of millions of tons, but the comprehensive utilization rate is low, occupying a large amount of land, and there is an urgent need for an efficient utilization method. The chemical composition of coal gasification slag is similar to that of fly ash, containing active substances such as SiO2 and Al2O3, which can undergo pozzolanic reactions, so there is a theoretical basis for it to be used as a binder and filler for fluid-solidified soil, thus replacing cement and soil resources. Some related methods for activating the activity of coal gasification slag to prepare binders are disclosed in the prior art. Guo Yuxia et al. disclosed a method for preparing a coal gasification slag-based binder by using desulfurized gypsum, anhydrous sodium sulfate, water glass, and chlorinated lime as activators, using coal gangue with different particle sizes as fine, medium, and coarse aggregates, and using P.O42.5 Portland cement as a blending material; Ma Zhibin et al. disclosed a method for preparing a high-volume coal gasification slag-based cement, using high-carbon coal gasification slag, steel slag, carbide slag, and clay as raw materials, and using low-carbon coal gasification slag, circulating fluidized bed fly ash, and desulfurized gypsum as active admixtures, and preparing a high-volume coal gasification slag-based cement after processes such as pretreatment, ball milling, and calcination. There are also some related studies on coal gasification slag-based multi-solid waste composite binders. The inventor found that these products have not been popularized and applied, and the reasons are as follows:

[0005] (1) There are too many material components, and problems such as insufficient supply of raw material sources, transportation from multiple places, and relatively high material costs are faced in popularization and application;

[0006] (2) The strength formation mainly relies on the bonding effect of lime or cement. The dosage of cement or lime is relatively large, and the insufficient bonding force between cement or lime and gasification slag affects the quality of the product after molding, resulting in a low cost performance of the product.

[0007] (3) The developed cementitious material processing technology is too complex to be popularized and applied. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a gasification slag-based backfill material to replace fluidized solidified soil. The raw materials of the backfill material are easy to obtain, with low cost, and there is a mutual coordination and mutual cementitious promotion effect among the raw materials, effectively ensuring the quality of the backfill material product.

[0009] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0010] In the first aspect, the present invention provides a gasification slag-based backfill material to replace fluidized solidified soil. The raw materials of the gasification slag-based backfill material include gasification slag, carbide slag, and titanium gypsum. The ratio of gasification slag, carbide slag, and titanium gypsum is 6 - 8, 1.5 - 3.5, 0.5 - 1.5, and an alkaline activator is also added.

[0011] The gasification slag is selected as the slag block with a set particle size formed after the molten slag at the bottom of the gasification furnace is cooled. The carbide slag is the waste residue mainly composed of calcium oxide after calcium carbide is hydrolyzed to obtain acetylene gas. Under the action of the alkaline activator, the gasification slag and the carbide slag are fully activated to release polyhedrons. Some polyhedrons form cementitious products to improve the early strength of the gasification slag-based backfill material; some polyhedrons react with calcium oxide in the carbide slag and calcium sulfate in the titanium gypsum to generate stable monosulfate calcium sulfoaluminate hydrate.

[0012] The gasification slag-based backfill material as described above has a simple composition, consisting of only three components: gasification slag, carbide slag, and titanium gypsum. The gasification slag is the ash residue formed after coal combustion. In this application, slag blocks with a set particle size are selected for convenient collection. Titanium gypsum is the precipitate produced in the production of titanium dioxide and has a relatively high water content. Carbide slag is the waste residue after acetylene gasification. The three raw materials are abundantly supplied, low in cost, and convenient for transportation. In an alkaline environment, the gasification slag and carbide slag are fully activated to release a large amount of active polyhedrons, generating a large amount of gelling products, which provide early strength for the gasification slag-based backfill material. Some of the active polyhedrons react with CaO provided by the carbide slag and free CaSO4 provided by the titanium gypsum to form calcium sulfoaluminate hydrate crystals with high sulfur content. As the reaction progresses, the free CaSO4 in the system decreases, and most of the calcium sulfoaluminate hydrate with high sulfur content transforms into the more stable and stronger calcium sulfoaluminate hydrate with single sulfur content. The crystal structure is short columnar, and the stability increases, ultimately forming a network cross-linked structure to ensure the structural strength and stability of the gasification slag-based backfill material. In addition, titanium gypsum contains iron oxide Fe2O3, and the iron oxide content is 9% - 18%. Under the action of the alkaline environment formed after mixing with carbide slag and alkaline activator, the iron in titanium gypsum mainly exists in the form of Fe(OH)3. On the one hand, a large amount of iron impurities contribute to the formation of calcium sulfoaluminate hydrate with single sulfur content, making the gelling structure more dense; on the other hand, under alkaline conditions, the hydrolysis degree of ferric sulfate and aluminum sulfate in titanium gypsum increases, so after hydrolysis, the two exist in the form of colloids and adsorb OH - and are negatively charged. The negatively charged colloid has a strong adsorption effect on positively charged heavy metal ions, enabling the gasification slag-based backfill material to also adsorb heavy metal pollutants in the surrounding soil and improve the soil.

[0013] For the gasification slag-based backfill material that replaces fluidized solidified soil as described above, the particle size of the slag block is 4 - 9 mm, ensuring the particle size of the calcium sulfoaluminate hydrate with single sulfur content formed.

[0014] For the gasification slag-based backfill material that replaces fluidized solidified soil as described above, the gasification slag includes silicon dioxide, aluminum oxide, iron oxide, and calcium oxide. The contents of silicon dioxide, aluminum oxide, iron oxide, and calcium oxide are 45% - 53%, 16% - 30%, 8% - 11%, and 11% - 16% in sequence. After the gasification slag and carbide slag are in full contact, silicon dioxide can form silicon tetraoxide tetrahedrons, and aluminum oxide can form tetra-aluminum oxide and hexa-aluminum oxide tetrahedrons, which are conducive to the formation of aluminates, C-S-H calcium silicate, calcium aluminosilicate, and sodium aluminosilicate gelling products, providing early strength for the gasification slag-based backfill material.

[0015] A kind of gasification slag-based backfill material substituting for flow-state solidified soil as described above, the titanium gypsum includes calcium sulfate and iron(III) oxide, and the contents of calcium sulfate and iron(III) oxide are 33% - 42% and 9% - 18% respectively. Under the action of the alkaline environment formed after the iron(III) oxide in the gasification slag and titanium gypsum is mixed with carbide slag and alkaline activator, the iron in the titanium gypsum mainly exists in the form of Fe(OH)3, which is beneficial to make the gel structure more dense, and the content of calcium sulfate in the titanium gypsum is relatively high to facilitate the formation of more monosulfate calcium sulfoaluminate hydrate.

[0016] A kind of gasification slag-based backfill material substituting for flow-state solidified soil as described above, the alkaline activator is sodium hydroxide, and the dosage is 3.5wt% - 5wt% of the sum of the masses of the gasification slag and carbide slag.

[0017] Second, the present invention also provides a preparation method of a gasification slag-based backfill material substituting for flow-state solidified soil, including the following contents:

[0018] Dry the required gasification slag, carbide slag and titanium gypsum.

[0019] Calculate and weigh the required gasification slag, carbide slag, titanium gypsum and activator.

[0020] Determine the water-cement ratio of the gasification slag-based backfill material, and then determine the required water.

[0021] Grind the gasification slag and carbide slag to obtain fine powders of gasification slag and carbide slag.

[0022] Mix the gasification slag, carbide slag and activator and stir evenly to obtain a solid powder mixture.

[0023] Mix the titanium gypsum and water and stir fully to obtain a titanium gypsum slurry.

[0024] Mix the solid powder mixture and the titanium gypsum slurry and stir fully to obtain the gasification slag-based backfill material.

[0025] For the preparation method of a gasification slag-based backfill material substituting for flow-state solidified soil as described above, the water-cement ratio of the gasification slag-based backfill material is calculated according to formula (1):

[0026] Q = 0.178A + 0.835B + 0.737C + 0.006AB - 0.210AC - 0.050BC + 1.538ABC (1)

[0027] Wherein, Q is the water-cement ratio of the gasification slag-based backfill material; A, B, and C are the proportions of the gasification slag, carbide slag, and titanium gypsum in the total mass of the three respectively.

[0028] A preparation method of a gasification slag-based backfill material substituting for fluidized solidified soil, as described above, dries the gasification slag and carbide slag by means of sun drying or drying to facilitate subsequent grinding.

[0029] In the third aspect, the present invention also provides an application of a gasification slag-based backfill material substituting for fluidized solidified soil. During the backfilling process of building foundation fat trenches, goafs, room centers, and trench foundations, the gasification slag-based backfill material prepared by the preparation method of a gasification slag-based backfill material substituting for fluidized solidified soil described above is used for backfilling.

[0030] The beneficial effects of the present invention described above are as follows:

[0031] 1) The materials provided by the present invention have only three components: gasification slag, carbide slag, and titanium gypsum. The composition is simple. The gasification slag is the ash residue formed after coal combustion. Selecting slag blocks with a set particle size is convenient for collection. Titanium gypsum is the precipitate produced in the production of titanium dioxide and has a relatively high water content. Carbide slag is the waste residue after acetylene gasification. The three raw materials are abundantly supplied, low in cost, and convenient for transportation, which is conducive to the promotion of the product. Under the action of an alkaline activator, the gasification slag and carbide slag are fully activated to release polyhedrons. Some polyhedrons form gel products to improve the early strength of the gasification slag-based backfill material. Some polyhedrons react with calcium oxide in the carbide slag and calcium sulfate in the titanium gypsum to generate stable monosulfate calcium sulfoaluminate, increasing the stability, and finally forming a network cross-linked structure. Under the action of an alkaline activator, the synergistic gelling effect among the gasification slag, titanium gypsum, and carbide slag is fully utilized to replace the incorporation of cement, effectively improving the compressive strength and performance of the formed product, and realizing the preparation of a binder material without clinker, low emissions, and low cost.

[0032] 2) In the present invention, the gasification slag and titanium gypsum contain iron oxide Fe2O3. Under the action of the alkaline environment formed after mixing with carbide slag and NaOH, the iron in the titanium gypsum mainly exists in the form of Fe(OH)3. On the one hand, a large amount of iron impurities contribute to the formation of monosulfate calcium sulfoaluminate, making the gel structure more dense. On the other hand, the hydrolysis degree of iron sulfate and aluminum sulfate in the titanium gypsum increases under alkaline conditions, so the two exist in the form of colloids after hydrolysis and adsorb OH - and are negatively charged under alkaline conditions. The negatively charged colloid has a strong adsorption effect on positively charged heavy metal ions, so that the gasification slag-based backfill material can also adsorb heavy metal pollutants in the surrounding soil and can improve the soil.

[0033] 3) In the present invention, the gasification slag-based backfill material is prepared from three materials, realizing the efficient utilization of large amounts of solid waste such as gasification slag, carbide slag, and titanium gypsum, effectively alleviating the environmental hazards and land occupation problems caused by the large accumulation of solid waste such as titanium gypsum and gasification slag, saving resources, and protecting the environment.

[0034] 4) The provision of the preparation method of the gasification slag-based backfill material in the present invention enables the preparation of the gasification slag-based backfill material. By drying, grinding, and mixing the gasification slag and carbide slag to obtain a solid powder mixture, mixing titanium gypsum with water to obtain a titanium gypsum slurry, and then mixing the titanium gypsum slurry with the solid powder mixture and fully stirring, the gasification slag-based backfill material is obtained after stirring. The preparation process is simple and highly operable. Without adding cement clinker, the quality of the formed gasification slag-based backfill material can be ensured.

[0035] 5) The gasification slag-based backfill material prepared in the present invention can be applied to the backfilling of building foundation fat grooves, goaf areas, room centers, and trench foundations. After forming, the gasification slag-based backfill material has high strength; and the volume stability of the backfilled structure is good, with small differential settlement from the surrounding buildings, ensuring the backfilling quality of the entire area. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The attached drawings forming a part of this invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0037] Figure 1 It is a reaction schematic diagram during the preparation process of the material of the gasification slag-based backfill material that replaces fluidized solidified soil according to one or more embodiments of the present invention.

[0038] Figure 2 It is a process schematic diagram of the preparation method of the gasification slag-based backfill material that replaces fluidized solidified soil according to one or more embodiments of the present invention.

[0039] Figure 3 It is a sample of the gasification slag-based backfill material prepared by the preparation method of the gasification slag-based backfill material that replaces fluidized solidified soil according to one or more embodiments of the present invention through a mold. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the present invention clearly states otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof;

[0042] As introduced in the background art, in the prior art, the fluid-solidified soil has problems such as many material components, high material costs, and mainly relying on the bonding effect of cement. To solve the above technical problems, the present invention proposes a gasification slag-based backfill material to replace the fluid-solidified soil.

[0043] Example 1

[0044] In a typical embodiment of the present invention, a gasification slag-based backfill material to replace the fluid-solidified soil, the raw materials of the gasification slag-based backfill material include gasification slag, carbide slag, and titanium gypsum. The ratio of gasification slag, carbide slag, and titanium gypsum is 6 - 8, 1.5 - 3.5, 0.5 - 1.5. An alkaline activator is also added. The strength of the gasification slag-based backfill material after 28 days is between 8 - 11 MPa, and the fluidity expansion degree is between 215 - 230 mm.

[0045] The gasification slag is selected as the slag block with a set particle size formed after the molten slag at the bottom of the gasification furnace is cooled. The carbide slag is the waste residue mainly composed of calcium oxide after calcium carbide is hydrolyzed to obtain acetylene gas. The dosage of titanium gypsum is less than or equal to 15% of the total mass of the three materials. This is because the strength formation of the entire cementitious system is mainly related to the dosages of gasification slag and carbide slag. When the dosage of titanium gypsum is too large, it will cause an excess of free calcium sulfate CaSO4 in the entire reaction system, and the free CaSO4 exists in the form of CaSO4·2H2O, which is not conducive to the transformation of high-sulfur hydrated calcium aluminate to the more stable and higher-strength monosulfide hydrated calcium aluminate, resulting in poor stability of the finally formed network cross-linked structure and reduced material strength.

[0046] Specifically, the gasification slag is selected as the coarse slag with a particle size between 4 - 9 mm formed after the molten slag at the bottom of the gasification furnace is cooled. The main components of the gasification slag include silicon dioxide SiO2 (45% - 53%), aluminum oxide Al2O3 (16% - 30%), iron oxide Fe2O3 (8% - 11%), calcium oxide CaO (11% - 16%), and also includes other components.

[0047] Among them, the main components of titanium gypsum include calcium sulfate CaSO4 (33% - 42%), iron oxide Fe2O3 (9% - 18%).

[0048] The carbide slag is the waste residue mainly composed of calcium oxide after calcium carbide is hydrolyzed to obtain acetylene gas. The main chemical component of the carbide slag is calcium oxide CaO, the content of calcium oxide is 54% - 72%, and it contains a small amount of impurities such as SiO2, Al2O3, SO3, Fe2O3, etc., and the loss on ignition is 23% - 31%.

[0049] In addition, the raw materials further include an activator. The alkaline activator added to the gasification slag and carbide slag has a dosage of 3.5 wt% to 5 wt%, which refers to the percentage of the dosage of the activator in the total mass of the gasification slag and carbide slag.

[0050] The gasification slag-based backfill material substituting for flowable solidified soil provided by this embodiment has simple composition, and fully utilizes the synergistic cementitious effect among the gasification slag, titanium gypsum and carbide slag. It reacts under the action of an alkaline activator, as Figure 1 shown. In an alkaline environment, the gasification slag and carbide slag are fully activated, releasing a large amount of active [SiO4 tetraoxygen silicon] tetrahedrons, [AlO4 tetraaluminum] tetrahedrons and [AlO6 hexaaluminum] coordination polyhedrons. A large amount of C-A-H (calcium aluminate), C-S-H (calcium silicate), C-A-S-H (calcium aluminosilicate), and N-A-S-H (sodium aluminosilicate) cementitious products are generated in the whole reaction system, providing early strength for the gasification slag-based backfill material. The remaining part of the active [SiO4] tetrahedrons, [AlO4] tetrahedrons and [AlO6] coordination polyhedrons react with CaO provided by the carbide slag and free CaSO4 provided by the titanium gypsum to generate ettringite crystals. As the reaction proceeds, the free CaSO4 in the system decreases, and most of the ettringite is transformed into more stable and higher-strength monosulfate, and the crystal structure is short columnar, with increased stability, resulting in further increase in the compactness and strength of the gasification slag-based backfill material. Finally, a network cross-linked structure mainly composed of C-A-S-H, 2CaSO4·H2O (gypsum), Aft (ettringite), and Afm (monosulfate) is formed, including the following chemical reaction formulas:

[0051] CaO + Al2O3 + H2O → C-A-H (2)

[0052] CaO + SiO2 + H2O → C-S-H (3)

[0053] Ca(OH)2 + SiO2 + Al2O3 + H2O → C-A-S-H (4)

[0054] NaSiO3 + Al2O3 + H2O → N-A-S-H (5)

[0055] 3CaO + 3Al2O3 + 3(CaSO4·2H2O) + 12H2O → 3CaO·Al2O3·3CaSO4·32H2O (6)

[0056] 3CaO·Al2O3·3CaSO4·32H2O + 2(3CaO·Al2O3·6H2O) → 3(3CaO·Al2O3·CaSO4·12H2O) (7)

[0057] Among them, NaSiO3 is sodium silicate, Al2O3 is aluminum oxide, SiO2 is silicon dioxide, Ca(OH)2 is calcium hydroxide, 3CaO·Al2O3·3CaSO4·32H2O is ettringite crystal, which is needle-shaped, has a retarding effect on the gelling system and provides partial strength, 3CaO·Al2O3·CaSO4·12H2O is monosulfate ettringite crystal, which is short columnar and has strong thermal stability, and can increase the compactness and strength of the coal gasification slag-based backfill material.

[0058] In addition, titanium gypsum contains iron oxide Fe2O3, and the iron oxide content is 9% - 18%. Under the action of the alkaline environment formed after mixing with carbide slag and NaOH, iron in titanium gypsum mainly exists in the form of Fe(OH)3. On the one hand, a large amount of iron impurities contribute to the formation of monosulfate ettringite, making the gelling structure more dense and improving the volume stability of the formed structure. On the other hand, the hydrolysis degree of ferric sulfate and aluminum sulfate in titanium gypsum increases under alkaline conditions, so after hydrolysis, the two exist in the form of colloid and adsorb OH - and are negatively charged. The negatively charged colloid has a strong adsorption effect on positively charged heavy metal ions, so that the coal gasification slag-based backfill material can also adsorb heavy metal pollutants in the surrounding soil and can improve the soil.

[0059] In this way, the coal gasification slag-based backfill material does not require the addition of cement, realizing the preparation of a cement-free, low-emission, and low-cost cementitious material under normal temperature process; while improving the compressive strength and performance of the product, it realizes the large consumption of bulk solid wastes such as coal gasification slag, carbide slag, and titanium gypsum, and can effectively alleviate the pollution hazards and land occupation problems caused by the large accumulation of solid wastes such as titanium gypsum and coal gasification slag.

[0060] Example Two

[0061] Reference Figure 2 As shown, this example provides a preparation method of a coal gasification slag-based backfill material to replace fluidized solidified soil, including the following contents:

[0062] 1) Dry the required coal gasification slag, carbide slag, and titanium gypsum.

[0063] 2) Determine the mix ratio: In this example, the ratio of coal gasification slag: carbide slag: titanium gypsum = 7:2:1. After calculation, 1400 g of coarse coal gasification slag, 400 g of carbide slag, and 200 g of titanium gypsum are taken. According to formula (1), the water-cement ratio of this mix ratio is calculated to be 0.373, and after calculation, 746 g of water is taken.

[0064] Q = 0.178A + 0.835B + 0.737C + 0.006AB - 0.210AC - 0.050BC + 1.538ABC (1)

[0065] Wherein, Q is the water-cement ratio of the gasification slag-based backfill; A, B, and C are the proportions of gasification slag, carbide slag, and titanium gypsum in the total mass of the three respectively;

[0066] 3) Place the gasification slag and carbide slag in a drying oven (the gasification slag and carbide slag can be placed in the drying oven simultaneously or sequentially for separate drying), and dry them at 100°C for a set time such as 90 min to dry the gasification slag and carbide slag;

[0067] 4) Pass the dried gasification slag and carbide slag through an existing planetary ball mill (the gasification slag and carbide slag can be placed in the ball mill simultaneously or sequentially for separate grinding), and grind them at a speed of 400 r / min for a set time such as 40 min to obtain fine powder of gasification slag and fine powder of carbide slag (the particle size of the fine powder of gasification slag and fine powder of carbide slag is less than or equal to 1 mm);

[0068] 5) Mix the gasification slag, carbide slag and activator, and place them in an existing mixer for dry mixing for 120 s to obtain a uniformly mixed solid powder mixture. The activator uses solid sodium hydroxide powder, and the dosage of the activator is 5 wt%;

[0069] 6) Mix the titanium gypsum with the set amount of water in step 1), and stir well in a mixer for a set time such as 120 s to obtain a titanium gypsum slurry;

[0070] 7) Mix the solid powder mixture in step 4) with the titanium gypsum slurry in step 5), and stir well in a mixer for 240 s to obtain the gasification slag-based backfill;

[0071] 8) Under standard curing conditions, after curing for a set time, obtain a qualified gasification slag-based backfill.

[0072] It is easily understandable that the determination of the flow expansion degree of the gasification slag-based backfill also includes the following content:

[0073] Take a certain amount of gasification slag-based backfill, conduct three flow expansion tests according to the existing engineering application requirements of fluidized solidified soil. The test standards and methods refer to the "Technical Guide for the Application of Fluidized Solidified Soil Filling". The test results are accurate to 1 mm. The test results are 217 mm, 216 mm, and 219 mm respectively. All three results are greater than 140 mm, and the error is less than or equal to 5%. Then the flow expansion degree of the gasification slag-based backfill is qualified;

[0074] After the flow spread meets the requirements, pour the coal gasification slag-based backfill into the test mold. The test mold is a 70.7mm×70.7mm×70.7mm mold, and the curing and forming of the test piece are carried out in accordance with the existing requirements for the engineering application of fluidized solidified soil.

[0075] Take out the samples cured for 3 days, 7 days, and 28 days under the curing conditions respectively. Among them, the 28-day test piece sample is as Figure 3 shown. Refer to the "Technical Guidelines for the Application of Fluidized Solidified Soil Filling" to conduct uniaxial compressive strength tests on the samples respectively. The test results are accurate to 0.01 MPa. The strengths of the three test samples at 7 days are 5.32 MPa, 5.56 MPa, and 5.11 MPa respectively. The average value is 5.33 MPa, and the mean square deviation is 0.24 MPa. The error of the three results is less than or equal to 0.5 MPa, and the result is qualified. The strengths of the three test samples at 28 days are measured to be 8.51 MPa, 8.18 MPa, and 8.97 MPa respectively; the average value is 8.56 MPa, and the mean square deviation is 0.39 MPa. The error of the three results is less than or equal to 0.5 MPa, and the result is qualified, that is, a qualified coal gasification slag-based backfill is obtained.

[0076] In this way, according to the above test results, during the backfilling process of the foundation fat groove, goaf, room center, and pipe trench foundation of the building, use the coal gasification slag-based backfill prepared by the above-mentioned preparation method of a coal gasification slag-based backfill to replace fluidized solidified soil for backfilling. The coal gasification slag-based backfill has high fluidity and can achieve self-compacting backfill in narrow and other difficult compaction construction areas. After curing the obtained coal gasification slag-based backfill for 28 days under the curing conditions, a qualified coal gasification slag-based backfill is obtained.

[0077] It is easy to understand that the coal gasification slag-based backfill prepared by the preparation method of a coal gasification slag-based backfill to replace fluidized solidified soil overcomes the defect of low strength of traditional fluidized solidified soil, breaks the application limitation that it can only be used for the subbase of low-grade roads, temporary roads, and the bottom layer of temporary floors, and can be used for the base and subbase of highways below grade II; it can also be used for deep foundation pit backfilling. Using fluidized solidified soil for backfilling can speed up the construction progress, shorten the construction period, have stable quality, and be pollution-free; it can also be used for the backfilling of mine pits, karst caves, and underground goafs. The coal gasification slag-based backfill can effectively solve problems such as high cost and environmental unfriendliness in the pretreatment of traditional karst caves, and has good economic and social benefits.

[0078] Specifically, when using the gasification slag-based backfill provided by this application, the raw material cost is less than 100 yuan per ton. Therefore, the developed product has a wide range of applications and broad promotion prospects. After large-scale promotion and application, energy conservation and emission reduction, cost reduction and efficiency improvement can be achieved during engineering construction, cement production and harmful gas emissions can be reduced, the ecological environment can be protected, the utilization efficiency of solid waste resources can be effectively improved, the intensive utilization of land resources can be promoted, land occupation can be reduced, and significant economic and social benefits will be brought.

[0079] In addition, in other examples, qualified gasification slag-based backfill is prepared with the ratio of gasification slag: carbide slag: titanium gypsum = 6:3:1.

[0080] 1) Determine the mix ratio: In this embodiment, the ratio of gasification slag: carbide slag: titanium gypsum is 6:3:1. After calculation, 1200 g of coarse gasification slag, 600 g of carbide slag, and 200 g of titanium gypsum are taken. According to the above formula (1), the water-cement ratio of this mix ratio is calculated to be 0.446. After calculation, 892 g of water is taken;

[0081] 2) Place the gasification slag and carbide slag in a drying oven (the gasification slag and carbide slag can be placed in the drying oven simultaneously or sequentially for separate drying), and dry them at 100 °C for a set time such as 90 min to dry the gasification slag and carbide slag;

[0082] 3) Pass the dried gasification slag and carbide slag through an existing planetary ball mill (the gasification slag and carbide slag can be placed in the ball mill simultaneously or sequentially for separate grinding), and grind them at a speed of 400 r / min for a set time such as 40 min to obtain fine gasification slag powder and fine carbide slag powder (the particle size of the fine gasification slag powder and fine carbide slag powder is less than or equal to 1 mm);

[0083] 4) Mix the gasification slag, carbide slag and activator, and place them in an existing mixer for dry mixing for 120 s to obtain a uniformly mixed solid powder mixture. The activator uses sodium hydroxide solid powder, and the activator dosage is 5 wt%;

[0084] 5) Mix the titanium gypsum with the set amount of water in step 1), and stir well in a mixer for a set time such as 120 s to obtain a titanium gypsum slurry;

[0085] 6) Mix the solid powder mixture in step 4) with the titanium gypsum slurry in step 5), and stir well in a mixer for 240 s to obtain the gasification slag-based backfill;

[0086] 7) Under standard curing conditions, after curing for a set time, obtain qualified gasification slag-based backfill.

[0087] It is easily understandable that the determination of the flow spread of the gasification slag-based backfill also includes the following content:

[0088] Take a fixed amount of gasification slag-based backfill and conduct three flow spread tests according to the existing engineering application requirements of fluidized solidified soil. The test results are accurate to 1 mm. The test results are 221 mm, 219 mm, and 222 mm respectively. The error of the three results is less than or equal to 5%. Then the flow spread of the gasification slag-based backfill is qualified.

[0089] After the flow spread meets the conditions, pour the gasification slag-based backfill into a test mold. The test mold uses a mold of 70.7 mm × 70.7 mm × 70.7 mm. The curing and forming of the specimens are carried out according to the existing engineering application requirements of fluidized solidified soil.

[0090] Take out the samples cured for 3 days, 7 days, and 28 days under standard curing conditions respectively. The 28-day specimen sample is as Figure 3 shown. Conduct uniaxial compressive strength tests on the samples respectively. The test results are accurate to 0.01 MPa. The strengths of the three test samples at 7 days are 6.45 MPa, 6.49 MPa, and 6.77 MPa respectively. The average value is 6.57 MPa, and the mean square deviation is 0.24 MPa. The error of the three results is less than or equal to 0.5 MPa, and the result is qualified. The strengths of the three test samples measured at 28 days are 10.29 MPa, 10.41 MPa, and 10.55 MPa respectively; the average value is 10.42 MPa, and the mean square deviation is 0.18 MPa. The error of the three results is less than or equal to 0.5 MPa, and the result is qualified, that is, a qualified gasification slag-based backfill is obtained.

[0091] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coal gasification slag-based backfill material replacing fluidized solidified soil, characterized in that: The raw materials of the coal gasification slag-based backfill material include coal gasification slag, carbide slag, and titanium gypsum. The ratio of coal gasification slag, carbide slag, and titanium gypsum is 6-8, 1.5-3.5, and 0.5-1.5, and an alkaline activator is also added; The coal gasification slag is a slag block with a set particle size formed after the slag at the bottom of the gasifier is cooled. The carbide slag is a waste slag with calcium oxide as the main component after acetylene gas is obtained by hydrolysis of calcium carbide. Under the action of an alkaline activator, the coal gasification slag and the carbide slag are fully activated to release polyhedrons. Some of the polyhedrons form a gelled product to improve the early strength of the coal gasification slag-based backfill material; some of the polyhedrons react with the calcium oxide in the carbide slag and the calcium sulfate in the titanium gypsum to generate stable monosulfide-type hydrated calcium sulfoaluminate.

2. The coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 1, characterized in that: The particle size of the slag block is 4 to 9 mm.

3. The coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 1, characterized in that: The coal gasification slag comprises silicon dioxide, aluminum oxide, ferric oxide and calcium oxide, wherein the contents of silicon dioxide, aluminum oxide, ferric oxide and calcium oxide are 45% to 53%, 16% to 30%, 8% to 11% and 11% to 16% respectively. After the coal gasification slag is fully in contact with the carbide slag, silicon dioxide can form silicon tetroxide tetrahedrons, and aluminum oxide can form aluminum tetroxide and aluminum hexaoxide tetrahedrons, which are beneficial to the formation of calcium aluminate, CSH calcium silicate, calcium aluminosilicate and sodium aluminosilicate gelled products.

4. The coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 1, characterized in that: The titanium gypsum includes calcium sulfate and ferric oxide, the contents of which are 33% to 42% and 9% to 18% respectively. Under the action of the alkaline environment formed after the ferric oxide is mixed with carbide slag and an alkaline activator, the iron in the titanium gypsum mainly exists in the form of Fe(OH)3.

5. The coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 1, characterized in that: The alkaline activator is sodium hydroxide, and the amount of the activator is 3.5wt% to 5wt% of the sum of the mass of the coal gasification slag and the carbide slag.

6. A method for preparing coal gasification slag-based backfill material to replace fluidized solidified soil, characterized in that: It includes the following: Drying the required coal gasification slag, carbide slag and titanium gypsum; Calculate and weigh the required coal gasification slag, carbide slag, titanium gypsum and activator; Determine the water-cement ratio of coal gasification slag-based backfill materials and thus determine the required water; Grinding the coal gasification slag and the carbide slag to obtain fine coal gasification slag powder and fine carbide slag powder; The coal gasification slag, carbide slag and activator are mixed and stirred evenly to obtain a solid powder mixture; Mixing titanium gypsum with water and stirring thoroughly to obtain titanium gypsum slurry; The solid powder mixture is mixed with the titanium gypsum slurry and stirred sufficiently to obtain a coal gasification slag-based backfill material.

7. The method for preparing a coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 6, characterized in that: The water-cement ratio of the coal gasification slag-based backfill material is calculated according to the following formula (1): Q=0.178A+0.835B+0.737C+0.006AB-0.210AC-0.050BC+1.538ABC (1); Among them, Q is the water-cement ratio of coal gasification slag-based backfill; A, B, and C are the proportions of coal gasification slag, carbide slag, and titanium gypsum in the total mass of the three, respectively.

8. The method for preparing a coal gasification slag-based backfill material replacing fluidized solidified soil according to claim 6, characterized in that: The coal gasification slag and carbide slag are dried by airing or drying them.

9. An application of coal gasification slag-based backfill material to replace fluidized solidified soil, characterized in that: In the process of backfilling the fertilizer trough, goaf, room core and pipe trench foundation of the building, the gasification slag-based backfill material prepared by the preparation method of the gasification slag-based backfill material replacing fluidized solidified soil described in any one of claims 6-8 is used for backfilling.

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