Solid-waste-based grouting material for mine roof-contacted filling and preparation method of solid-waste-based grouting material

Abstract

The invention discloses a solid-waste-based grouting material for mine roof contact filling and a preparation method. The solid-waste-based grouting material comprises 30-44 parts of steel slag powder, 25-39 parts of fly ash, 8-15 parts of desulfurized gypsum, 10-24 parts of activated coal gangue powder and 13-18 parts of an alkali activator. The mass ratio of the alkali activator water glass to the sodium hydroxide is 1.5-2.5; the content of free calcium oxide f-CaO required by the steel slag powder is lt; the specific surface area is greater than or equal to 700m < 2 > / kg; the activated coal gangue powder is prepared by calcining coal gangue at 650-750 DEG C for 1-2 hours, removing organic matters and activated silicon-aluminum components, and grinding until the specific surface area is greater than or equal to 500m / kg. The fluidity of the obtained material is 260-310 mm, the 3d compressive strength is larger than or equal to 7.2 MPa, and the 28d shrinkage rate lt is achieved; the solid waste utilization rate is greater than or equal to 90%, and the cost is reduced by more than 35% compared with that of the traditional material. The material is used for mine filling roof contact, has the characteristics of good fluidity, rapid hardening, appropriate early strength, excellent volume stability, environmental friendliness and low cost, and has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the technical field of cementitious materials for tailings backfilling in underground mining, specifically relating to a mine backfilling grouting material based on solid waste and its preparation method. Background Technology

[0002] Backfilling mining is a key technology for controlling goaf areas and preventing surface subsidence, and its application is becoming increasingly widespread in modern green mine construction. Currently, mine backfilling mainly uses ordinary silicate cement-based cementitious materials and cementitious materials prepared from industrial solid wastes such as slag, steel slag, and desulfurized gypsum. However, these calcium silicate-based cementitious materials suffer from slow early strength development and significant volume stability issues. Their hydration products are mainly hydrated calcium silicate gel (CSH) and ettringite (AFt), which may shrink later due to ettringite transformation, drying shrinkage, or settlement, preventing the backfill from fully connecting with the roof and forming goaf areas. The existence of goaf roofs not only reduces the support effect and increases the exposed roof area and the risk of collapse, but also leads to water accumulation in the stope due to runoff. Furthermore, rainwater, under the influence of surface runoff, seeps into the rock strata and enters the goaf area, further causing mine tunnel water inrush and deteriorating the natural environment.

[0003] Currently, the main material used for mine roof filling is silicate cement. For example, Chinese patent (CN202211573042) uses an expanding agent to activate cement before it is used as a roof filling material. After mixing with the seepage water inside the empty roof, it expands to a certain extent, thus achieving roof filling. However, this method has disadvantages such as high cost and high carbon emissions. For example, Chinese patent (CN202510634557) utilizes the micro-expansion properties of steel slag powder to better compensate for the volume shrinkage of the mine, thereby increasing the volume stability of the mine filling. However, it has defects such as low early strength and slow setting time.

[0004] Studies have shown that geopolymers possess advantages such as early strength and rapid hardening, corrosion resistance, low shrinkage, high temperature resistance, and environmental friendliness. However, research on geopolymers for mine backfilling is relatively limited. In particular, how to utilize the characteristics of solid waste materials to synergistically address the shrinkage and strength issues of backfill materials still requires in-depth exploration. Therefore, this invention aims to realize the resource utilization of solid waste by transforming multi-source solid wastes such as coal gangue, steel slag, fly ash, and desulfurized gypsum into a high-performance green backfill material through alkali activation technology. The goal is to replace cement in a more environmentally friendly and economical way and achieve engineering applications. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing underground filling cementitious materials, such as slow early strength development, significant volume stability issues, inability to adequately connect to the roof, high cost, and high carbon emissions. The invention provides a high-performance, low-cost, and environmentally friendly solid waste-based grouting material for mine filling and roof connection, thus solving the problem of mine filling and roof connection.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned solid waste-based grouting material for mine backfilling.

[0007] To achieve the above-mentioned objectives of this invention, a solid waste-based grouting material for mine roof filling is provided. The raw material components, when calculated on a 100-part basis, consist of: 30-44 parts steel slag powder, 25-39 parts fly ash, 8-15 parts desulfurized gypsum, 10-24 parts activated coal gangue powder, and 13-18 parts alkaline activator. The alkaline activator is a compound of water glass and sodium hydroxide, with a mass ratio of water glass to sodium hydroxide of 1.5-2.5 and a modulus of water glass of 1.6-2.0. Within this range, it helps to form a geopolymer gel structure with high strength and good stability. The steel slag powder is required to have a free calcium oxide (f-CaO) content of <3% to avoid later volume instability, and a specific surface area ≥700 m². 2 / kg, to ensure its activity; the activated coal gangue powder is made by calcining coal gangue at 650~750℃ for 1~2h to remove organic matter and activated silicon-aluminum components, and then grinding it to a specific surface area ≥500m² / kg, so that it has the dual functions of providing active Al2O3 and SiO2 and filling micro aggregates.

[0008] Preferably, the fly ash is grade II or higher to ensure its activity and water requirement ratio.

[0009] Preferably, the desulfurized gypsum is dihydrate desulfurized gypsum with a specific surface area ≥350m² / kg, in order to provide early sulfate activation and regulate setting time.

[0010] Preferably, the purity of the NaOH is ≥95%.

[0011] Preferably, the desulfurized gypsum is dihydrate desulfurized gypsum with a specific surface area ≥350m² / kg; and the NaOH has a purity ≥95%.

[0012] This invention discloses a method for preparing a solid waste-based grouting material for mine roof filling, characterized by the following steps:

[0013] S1 Preparation of Alkali Activator

[0014] Weigh out the NaOH granules according to the specified ratio, add them to the water in the specified ratio, and stir until completely dissolved; then add the measured amount of water glass and continue stirring to mix it evenly.

[0015] S2 Dry Mixed Solid Waste Raw Materials

[0016] Accurately weigh steel slag powder, fly ash, desulfurized gypsum and activated coal gangue powder according to the weight proportions, put the above dry powder materials into a forced mixer or mixing machine, mix and stir for 5 to 10 minutes until the color is uniform and there are no visible lumps, and obtain the dry powder mixture.

[0017] S3 Hybrid Molding

[0018] The alkali activator prepared in step S1 is added to the dry powder mixture in step S2 in three parts. After the first and second additions, the mixture is stirred quickly for 1 to 2 minutes each time. After the third addition, the mixture is stirred for another 3 to 4 minutes. The total stirring time is controlled at 5 to 8 minutes until a uniformly fluid solid waste-based grouting material is formed.

[0019] Once the slurry's fluidity is tested and found to be satisfactory, it can be injected into a mold to form a sample for performance testing, or it can be directly pumped to the goaf area of ​​the mine for filling and roof connection operations.

[0020] Furthermore, the performance parameters of the prepared solid waste-based grouting material are as follows: 3-day compressive strength 7.1~9.5 MPa, 28-day compressive strength 14.0~17.5 MPa, fluidity 260~310 mm, and initial setting time 110~160 min.

[0021] Furthermore, the shrinkage rate of the prepared solid waste-based grouting material slurry is ≤0.3% after filling and connecting to the roof within 28 days.

[0022] Compared with the prior art, the solid waste-based grouting material and its preparation method for mine roof filling of the present invention have the following advantages:

[0023] (1) This invention uses four types of industrial solid wastes, namely steel slag, fly ash, desulfurized gypsum and coal gangue, as the main raw materials. The total amount of solid waste can reach more than 90%, and the cost is reduced by more than 35% compared with traditional cement-based grouting materials, realizing the high added value resource utilization of solid waste.

[0024] (2) This invention utilizes the potential hydraulic activity and micro-expansion characteristics of steel slag powder to compensate for system shrinkage, which is beneficial for top compaction. Utilizing the high activity of calcined and activated coal gangue powder after ultrafine grinding, it not only serves as an active component in the system, providing Si and Al elements to participate in the polymerization reaction, but also acts as micro-aggregate to fill pores, optimize particle size distribution, improve slurry density and strength, and reduce shrinkage. This reduces the use of expensive slag in traditional solid waste-based cementitious materials.

[0025] (3) This invention utilizes the synergistic effect of each component and optimized proportions rather than simple gel mixing. The resulting geopolymer material exhibits a performance combination that is very suitable for mine backfilling and roof support. Good fluidity facilitates pumping and backfilling, and a suitable initial setting time ensures both construction time and avoids slow setting. Reasonable early strength can quickly provide initial support and meet the strength requirements for roof support. Extremely low drying shrinkage ensures long-term volume stability of the backfill body, close contact with the roof slab, and eliminates empty roofs. At the same time, the carbon emissions of the geopolymer production process are far lower than those of traditional cement.

[0026] (4) The test results show that the solid waste-based grouting material prepared by the present invention for mine backfilling has excellent technical performance, with a 3-day compressive strength of 7.1~9.5 MPa, a 28-day compressive strength of 14.0~17.5 MPa, a fluidity of 260~310 mm, and an initial setting time of 110~160 min; and a shrinkage rate of ≤0.3% after 28 days of backfilling in goaf areas.

[0027] In summary, this invention provides a solid waste-based grouting material and its preparation method for mine roof filling, which has high solid waste utilization rate, low cost, excellent performance, and simple preparation process, and has good application prospects and promotion value. Detailed Implementation

[0028] To describe the present invention, the following detailed description, in conjunction with embodiments, provides a solid waste-based grouting material for mine roof filling and its preparation method. This detailed description should not be construed as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the invention.

[0029] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0032] In the examples, the main chemical components of activated coal gangue powder are: SiO2 content 53.2%, Al2O3 content 42.6%, and CaO content 0.55%. The main chemical components of steel slag powder are: SiO2 content 11.42%, Al2O3 content 3.38%, and CaO content 45.87%. The main chemical components of fly ash are: SiO2 content 51.54%, Al2O3 content 30.00%, and CaO content 5.18%. The main chemical components of desulfurized gypsum are: CaO content 48.33% and SO3 content 45.39%.

[0033] Example 1

[0034] Weigh the raw materials according to the following proportions by weight: 35 parts steel slag powder, 35 parts fly ash, 10 parts desulfurized gypsum, and 20 parts activated coal gangue powder. Alkaline activator: 5 parts NaOH and 10 parts water glass with a modulus of 1.8. The water-to-solid ratio is controlled at 0.35. Add the weighed steel slag powder, fly ash, desulfurized gypsum, and activated coal gangue powder to a forced mixer and mix for 8 minutes until homogeneous. Add the alkaline activator to the dry mixture in three portions, mixing for 1.5 minutes after each addition, for a total mixing time of 6 minutes, to obtain a homogeneous slurry. Pour into molds and cure under standard conditions (20±2℃, humidity ≥90%). Performance test results are shown in Table 1.

[0035] Example 2

[0036] Unlike Example 1, the raw materials were weighed as follows: 40 parts steel slag powder, 30 parts fly ash, 12 parts desulfurized gypsum, and 18 parts activated coal gangue powder. The alkali activator consisted of 6 parts NaOH and 9 parts water glass with a modulus of 1.6. The water-to-solid ratio was controlled at 0.38. The performance test results are shown in Table 1.

[0037] Example 3

[0038] Unlike Example 1, the raw materials were weighed in the following proportions by weight: 30 parts steel slag powder, 40 parts fly ash, 15 parts desulfurized gypsum, and 15 parts activated coal gangue powder. The alkali activator consisted of 4 parts NaOH and 12 parts water glass with a modulus of 2.0. The water-to-solid ratio was controlled at 0.40. The performance test results are shown in Table 1.

[0039] Example 4

[0040] Unlike Example 1, the raw materials were weighed as follows: 45 parts steel slag powder, 25 parts fly ash, 8 parts desulfurized gypsum, and 22 parts activated coal gangue powder. The alkali activator consisted of 7 parts NaOH and 11 parts water glass with a modulus of 1.7. The water-to-solid ratio was controlled at 0.32. The performance test results are shown in Table 1.

[0041] Example 5

[0042] Unlike Example 1, the raw materials were weighed as follows: 38 parts steel slag powder, 32 parts fly ash, 11 parts desulfurized gypsum, and 19 parts activated coal gangue powder. The alkali activator consisted of 5.5 parts NaOH and 10.5 parts water glass with a modulus of 1.8. The water-to-solid ratio was controlled at 0.36. The performance test results are shown in Table 1.

[0043] Example 6

[0044] Unlike Example 1, the raw materials were weighed in the following proportions by weight: 33 parts steel slag powder, 37 parts fly ash, 13 parts desulfurized gypsum, and 17 parts activated coal gangue powder. The alkali activator consisted of 4.5 parts NaOH and 11.5 parts water glass with a modulus of 1.9. The water-to-solid ratio was controlled at 0.37.

[0045] Comparative Example 1

[0046] The formulation was the same as in Example 1, but activated coal gangue powder was not used; its weight was replaced by an equal amount of fly ash. The preparation method was the same as in Example 1. The performance test results are shown in Table 1.

[0047] Comparative Example 2

[0048] The same proportions as in Example 1 were used, but unactivated undisturbed coal gangue powder was used instead of activated coal gangue powder. The preparation method was the same as in Example 1. The performance test results are shown in Table 1.

[0049] Comparative Example 3

[0050] Referring to the formulation of Example 1, steel slag powder with a free calcium oxide content of 4.5% was used. The preparation method was the same as in Example 1. The performance test results are shown in Table 1.

[0051] Comparative Example 4

[0052] Referring to the formulation of Example 1, without using any desulfurized gypsum, 10 parts by weight were replaced by equal amounts of steel slag powder and fly ash (5 parts each). The preparation method was the same as in Example 1, and the performance test results are shown in Table 1.

[0053] Table 1 Performance test results of the examples and comparative examples

[0054]

[0055] As can be seen from Examples 1-6, the material prepared by the present invention has a fluidity in the range of 260-310 mm, a 3-day compressive strength ≥7.2 MPa, and a 28-day shrinkage rate of less than 0.3%, exhibiting good fluidity, early strength and extremely low shrinkage rate, which fully meets the performance requirements for mine backfilling and roof support. Compared with traditional cement-based materials, the cost is reduced by about 38%, the solid waste utilization rate is as high as 92%, and the shrinkage rate is significantly reduced.

[0056] Comparative Examples 1 and 2 demonstrate that activated coal gangue powder plays a crucial role in activating the system and filling it with micro-aggregates. Comparative Example 3 highlights the importance of controlling the f-CaO content in steel slag powder, as excessive f-CaO leads to volume instability in the later stages. Comparative Example 4 reflects that desulfurized gypsum participates in the chemical reaction as a regulator rather than a simple filler.

[0057] The solid waste-based grouting material prepared by this invention for mine roof filling has been applied in a certain underground iron mine using the filling method. The application results show that the average roof filling rate is as high as 99.5%, achieving unexpected technical effects.

[0058] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A solid waste-based grouting material for mine roof filling, characterized in that... The total weight of the raw materials, calculated per 100 parts, is as follows: 30-44 parts steel slag powder, 25-39 parts fly ash, 8-15 parts desulfurized gypsum, 10-24 parts activated coal gangue powder, and 13-18 parts alkaline activator. The alkaline activator is a mixture of water glass and sodium hydroxide, with a mass ratio of water glass to sodium hydroxide of 1.5-2.5 and a modulus of water glass of 1.6-2.

0. The steel slag powder is required to have a free calcium oxide (f-CaO) content of <3% and a specific surface area ≥700 m². 2 / kg; The activated coal gangue powder is prepared by calcining coal gangue at 650~750℃ for 1~2h to remove organic matter and activated silicon-aluminum components, and then grinding it to a specific surface area ≥500m² / kg.

2. The solid waste-based grouting material for mine roof filling as described in claim 1, characterized in that: The fly ash used is Grade II or higher.

3. The solid waste-based grouting material for mine roof filling as described in claim 1, characterized in that: The desulfurized gypsum used is dihydrate desulfurized gypsum with a specific surface area ≥350m² / kg.

4. The solid waste-based grouting material for mine roof filling as described in claim 1, characterized in that: The purity of the NaOH is ≥95%.

5. A solid waste-based grouting material for mine roof filling as described in claim 2, characterized in that: The desulfurized gypsum is selected from dihydrate desulfurized gypsum, with a specific surface area ≥350m² / kg; the purity of the NaOH is ≥95%.

6. The method for preparing a solid waste-based grouting material for mine roof filling as described in claim 5, characterized in that... The following steps are adopted: S1 Preparation of Alkali Activator Weigh out the NaOH granules according to the specified ratio, add them to the water in the specified ratio, and stir until completely dissolved; then add the measured amount of water glass and continue stirring to mix it evenly. S2 Dry Mixed Solid Waste Raw Materials Accurately weigh steel slag powder, fly ash, desulfurized gypsum and activated coal gangue powder according to the weight proportions, put the above dry powder materials into a forced mixer or mixing machine, mix and stir for 5 to 10 minutes until the color is uniform and there are no visible lumps, and obtain the dry powder mixture. S3 Hybrid Molding The alkali activator prepared in step S1 is added to the dry powder mixture in step S2 in three parts. After the first and second additions, the mixture is stirred quickly for 1 to 2 minutes each time. After the third addition, the mixture is stirred for another 3 to 4 minutes. The total stirring time is controlled at 5 to 8 minutes until a uniformly fluid solid waste-based grouting material is formed.

7. The method for preparing a solid waste-based grouting material for mine roof filling as described in claim 6, characterized in that: The performance parameters of the prepared solid waste-based grouting material are as follows: 3-day compressive strength 7.1~9.5 MPa, 28-day compressive strength 14.0~17.5 MPa, fluidity 260~310 mm, and initial setting time 110~160 min.

8. The method for preparing a solid waste-based grouting material for mine roof filling as described in claim 6, characterized in that: The shrinkage rate of the prepared solid waste-based grouting material slurry after filling and connecting to the roof is ≤0.3% after 28 days.

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