A recycled roof grout for mines and its preparation method

Abstract

This invention discloses a recycled roof grouting slurry for mines and its preparation method, relating to the field of reinforcement grouting slurry technology. Sodium silicate solution and calcium chloride are mixed and stirred evenly to obtain an additive. Clay and water are mixed and stirred until homogeneous. After the slurry is aged, a yellow mud slurry is obtained. Ordinary silicate cement, quicklime, the additive, and hydroxypropyl methylcellulose are added to the yellow mud slurry and stirred until homogeneous to obtain the recycled roof grouting slurry for mines. This invention uses waste clay from construction sites as the main raw material, reducing the amount of ordinary silicate cement used. This reduces costs while achieving resource reuse. Hydroxypropyl methylcellulose has a certain water retention capacity, which increases the viscosity of the grouting slurry and effectively binds fine particles in the original slurry, such as clay, thus improving the consolidation strength of the hardened grout.

Description

Technical Field

[0001] This invention belongs to the field of reinforcement and strengthening grouting technology, and in particular relates to a novel grouting slurry for mine recycled roof and its preparation method. Background Technology

[0002] There are three main methods for mining thick coal seams: high-depth single-pass full-thickness mining, layered mining, and top-coal caving mining. Layered mining is the dominant technology for thick coal seams in my country. The regenerated roof is the roof of the lower layer formed by the natural consolidation or artificial cementation of the collapsed gangue from the upper layer during layered mining. In layered mining of thick coal seams, especially top-layered mining, a large amount of rubble collapses from the upper roof in the goaf. Goaf grouting is a key measure to prevent spontaneous combustion of the coal seam and collapse of surrounding strata, improve the bearing capacity of the strata, and reduce the coal seam recovery cycle.

[0003] Currently, most grouting slurries used in grouting processes use ordinary silicate cement as the cementitious slurry. Ordinary silicate cement as the raw slurry is not only expensive, but also sets quickly. The groutability of cement-based mining grouts is usually achieved by increasing the water-cement ratio of the slurry. In addition, the heat of hydration of cement itself is not safe for coal.

[0004] With the progress of urban construction and renovation, clay waste is increasing, such as building clay bricks and large amounts of clay generated during foundation excavation. This not only occupies arable land, pollutes the surrounding environment, and affects the aesthetics of the city, but also requires a lot of manpower for processing and transportation. Therefore, it is of great significance to carry out research on the resource-based reuse of clay waste.

[0005] Therefore, there is an urgent need in this field for a clay-based recycled roof grouting slurry for mining. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a novel grouting slurry for mine recycled roofs and its preparation method. Using clay obtained from excavating the foundation as the main raw material, it achieves resource reuse and reduces the amount of ordinary silicate cement used. Simultaneously, by controlling the amount of hydroxypropyl methylcellulose added, a novel grouting slurry for mine recycled roofs with adjustable operating time is obtained. This grouting slurry is not only low in cost but also exhibits excellent performance.

[0007] This invention provides a novel grouting slurry for recycled roof slabs in mines, comprising, by weight, 40-60 parts clay, 4-8 parts ordinary silicate cement, 4-8 parts quicklime, 0.3-0.7 parts admixture, and 0.2-0.8 parts hydroxypropyl methylcellulose.

[0008] Clay-based grouts possess a certain binding capacity, but this capacity does not significantly increase the compressive strength of the grout. This invention fixes the amounts of clay, ordinary silicate cement, quicklime, and admixtures in the grout, while varying the amount of hydroxypropyl methylcellulose (HMC). Further research into the effect of HMC dosage on the workability time of the grout reveals that HMC has a significant impact on the workability time; as the HMC dosage increases, the workability time of the clay-based grout gradually decreases. The addition of HMC increases the grout viscosity and consistency, thus hindering the workability time. Workability time is a crucial parameter affecting the flowability and groutability of the grout. This invention adjusts the workability time of the grout within an appropriate range by adding HMC. Considering that HMC has good water retention properties but its addition is detrimental to the workability time, this invention strictly limits its dosage.

[0009] To prepare a green, low-cost, and high-performance novel grouting material for recycled roof slabs in mines, this invention uses clay as the main raw material, with the addition of small amounts of ordinary silicate cement, quicklime, admixtures, and hydroxypropyl methylcellulose, to prepare a novel clay-based recycled roof grouting material.

[0010] The introduction of hydroxypropyl methylcellulose (HMC) solves the problem of low grout viscosity while ensuring a good workability time for the grout material. It also optimizes the interfacial bonding between the grout material and the rock, improving the mechanical properties of the hardened grout structure. Using water as a carrier, the grout fills the gaps in the collapsed rock in the goaf through its fluidity. The addition of HMC further enhances the bonding between the grout and the rock interface, allowing the hardened grout structure to bond seamlessly with the rock, thus contributing to improved roof strength.

[0011] When ordinary Portland cement is added, it interacts with the sodium silicate solution in the admixture, which significantly reduces the grouting workability time. By limiting the amount of ordinary Portland cement added, not only can costs be saved, but its adverse effects on workability time can also be reduced.

[0012] Furthermore, the viscosity of the hydroxypropyl methylcellulose is 150,000 to 250,000.

[0013] Furthermore, the additive is composed of sodium silicate solution and calcium chloride in a mass ratio of 1 to 1.5:1.

[0014] Furthermore, the additive is composed of sodium silicate solution and calcium chloride in a mass ratio of 1 to 1.2:1.

[0015] By adding sodium silicate solution and calcium chloride, a calcium source is added to the grout. The addition of sodium silicate solution provides potential conditions for improving the strength of the hardened grout in the later stage.

[0016] This invention also provides a method for preparing a novel grouting slurry for mine recycled roof, comprising the following steps:

[0017] S1. After mixing sodium silicate solution and calcium chloride, stir evenly and react to obtain an additive;

[0018] S2. Mix clay and water, stir until uniform, and allow the slurry to settle to obtain yellow mud slurry;

[0019] S3. Add ordinary silicate cement, quicklime, admixtures, and hydroxypropyl methylcellulose to yellow mud slurry and stir until uniform to obtain a new type of grouting slurry for mine recycled roof.

[0020] Furthermore, the reaction temperature in S1 is 18–25°C, and the reaction time is 2–6 h.

[0021] Furthermore, the mass ratio of water to clay is 1 to 4:1, and the slurry aging time is 12 to 24 hours.

[0022] The beneficial effects of this invention are:

[0023] This invention uses waste clay from construction sites as the main raw material, reducing the amount of ordinary silicate cement used and minimizing the unsafe impact of cement hydration heat on coal. More importantly, it achieves resource reuse while reducing costs. Hydroxypropyl methylcellulose has a certain water retention capacity, which can increase the viscosity of the grout and effectively bind the fine particles of the original grout, such as clay, together, which is beneficial to improving the consolidation strength of the hardened grout.

[0024] The working time of the novel recycled roof grout provided by this invention can be adjusted within the range of 3.9 to 17 hours. After adding hydroxypropyl methylcellulose, the compressive strength of the hardened solid after 28 days of curing increased from 0.9 MPa to 1.42 MPa, an increase of 57.8%. The mechanical properties of the hardened solid of the clay-based grout were greatly improved. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a flowchart illustrating the preparation method of a novel grouting slurry for mine recycled roof in Example 1;

[0027] Figure 2 The graph shows the change in the operability time of the novel recycled roof grouting material obtained in Examples 1-5.

[0028] Figure 3 This is a diagram illustrating the viscosity measurement experiment in an embodiment of the present invention.

[0029] Figure 4 The viscosity variation graphs are shown for the novel recycled roof grouting materials obtained in Examples 1-5.

[0030] Figure 5 The graph shows the change in the operable time of the grouting slurry obtained in Comparative Examples 2-6.

[0031] Figure 6 The viscosity variation graphs of the grouting slurry obtained in Comparative Examples 1-6 are shown.

[0032] Figure 7 The image shows the interface bonding between the hardened aggregate and the grout obtained in Example 1, Comparative Examples 4 and 6.

[0033] Figure 8 This is a comparison chart of the workable time of the grouting slurry in Example 1 and Comparative Examples 7 and 8;

[0034] Figure 9 This is a comparison chart of the viscosity of the grout in Example 1 and Comparative Examples 7 and 8. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] 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.

[0037] 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 slurries are described herein, any methods and slurries 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 slurries associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] 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 obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] Unless otherwise specified, the term "parts" in this invention refers to "parts by weight".

[0041] This invention provides a novel grouting slurry for recycled roof slabs in mines, comprising, by weight, 40-60 parts clay, 4-8 parts ordinary silicate cement, 4-8 parts quicklime, 0.3-0.7 parts admixture, and 0.2-0.8 parts hydroxypropyl methylcellulose.

[0042] In the embodiments of the present invention, the clay used is loess from the foundation of Anhui University of Architecture, which is more in line with the actual engineering background. The cost of grouting materials is greatly reduced from the source in terms of raw material selection. The present invention does not have special requirements for the source of the clay, and any clay familiar to those skilled in the art can be used.

[0043] Since the viscosity of hydroxypropyl methylcellulose affects the workability and fluidity of the grout, excessively high viscosity will reduce the workability of the grout and hinder its groutability, while excessively low viscosity will reduce the bonding force between the hardened grout and the rock mass, thereby reducing the compressive strength of the grout. Therefore, in this embodiment of the invention, the viscosity of hydroxypropyl methylcellulose is preferably 150,000 to 250,000.

[0044] The industrial-grade calcium chloride selected in this invention is solid spherical particles. If it is added directly alone, the solid particles are difficult to dissolve, which will affect the grouting material slurry performance. Therefore, in some preferred embodiments of this invention, sodium silicate and calcium chloride are mixed at a mass ratio of 1 to 1.5:1 to obtain an admixture. After the calcium chloride is fully dissolved, the admixture is mixed with other components and then mixed with the yellow mud slurry. In order to reduce costs, in some more preferred embodiments, the mass ratio of sodium silicate solution and calcium chloride in the admixture is limited to 1 to 1.2:1.

[0045] This invention also provides a method for preparing a novel grouting slurry for mine recycled roof, comprising the following steps:

[0046] S1. After mixing sodium silicate solution and calcium chloride, stir evenly and react to obtain an additive;

[0047] S2. Mix clay and water, stir until uniform, and allow the slurry to settle to obtain yellow mud slurry;

[0048] S3. Mix ordinary silicate cement, quicklime, admixtures, hydroxypropyl methylcellulose and yellow mud slurry, and stir until uniform to obtain a new type of grouting slurry for mine recycled roof.

[0049] In some preferred embodiments, the reaction temperature in S1 is 18-25°C, the reaction time is 2-6 hours, the mass ratio of water to clay is 1-4:1, and the slurry settling time is 12-24 hours.

[0050] In some preferred embodiments of the present invention, the yellow mud slurry in S2 should be thoroughly stirred, and the clay particles should be evenly dispersed in the solution. The stirring operation should be carried out at a temperature of 18–25°C.

[0051] In this embodiment of the invention, the ordinary Portland cement used is grade 42.5 ordinary Portland cement produced by Conch Cement Plant in Wuhu City, Anhui Province;

[0052] The quicklime was produced by Jiangxi Xinyu Huihui Industry Co., Ltd., and its purity was: CaO≥95%;

[0053] Calcium chloride is produced by Zhejiang Quzhou Jusu Chemical Co., Ltd.; it is anhydrous industrial grade with a purity of CaCl2≥94.0%.

[0054] The sodium silicate solution was produced by China Salt Anhui Hongsifang Co., Ltd., and its Baume degree was 39-40, with a modulus range of 2.8-3.3.

[0055] Hydroxypropyl methylcellulose is produced by Shanghai Chenqi Chemical Technology Co., Ltd., with a viscosity range of 150,000 to 250,000.

[0056] The main chemical components of silicate cement and clay in the embodiments of the present invention, by mass parts, are shown in Table 1.

[0057] Table 1

[0058]

[0059] Note: LOI a This indicates the loss on ignition.

[0060] Example 1

[0061] A novel grouting slurry for recycled roof slabs in mines comprises, by weight, 50 parts clay, 6 parts ordinary silicate cement, 6 parts quicklime, 0.25 parts sodium silicate solution, 0.25 parts calcium chloride, and 0.4 parts hydroxypropyl methylcellulose, wherein the hydroxypropyl methylcellulose has a viscosity of 200,000, and the sodium silicate solution has a Baume degree of 39.2 and a modulus of 3.3.

[0062] A method for preparing a novel grouting slurry for mine recycled roof is as follows:

[0063] S1. Preparation of admixture: Sodium silicate solution and calcium chloride are mixed and stirred evenly. After reacting at 25°C for 2 hours, the admixture is obtained.

[0064] S2. Preparation of yellow mud slurry: Clay and laboratory tap water were mixed and stirred evenly. After the slurry was aged for 24 hours, yellow mud slurry was obtained.

[0065] S3. Hydroxypropyl methylcellulose, ordinary silicate cement, quicklime and additives are added to yellow mud slurry and stirred evenly to obtain a new type of recycled roof grouting material for mines. Figure 1 This is a flowchart of a method for preparing a novel grouting slurry for mine recycled roof in Example 1.

[0066] Examples 2-5

[0067] Same as Example 1, except that the amount of hydroxypropyl methylcellulose added is different, and the specific amount added is shown in Table 2.

[0068] Table 2

[0069]

[0070] Note: N: clay, C: ordinary silicate cement, S: quicklime, W: admixture, Ce: hydroxypropyl methylcellulose

[0071] The variation in the workability time of the novel recycled roof grouting materials obtained in Examples 1-5 is shown in the figure. Figure 2 ,Depend on Figure 2 It can be seen that as the amount of hydroxypropyl methylcellulose increases, the working time of grouting can be adjusted between 3.9h and 17h.

[0072] Figure 3This is a diagram illustrating the viscosity measurement experiment in this invention. The viscosity changes of the novel recycled roof grouting materials obtained in Examples 1-5 are shown below. Figure 4 ,Depend on Figure 4 It can be seen that as the amount of hydroxypropyl methylcellulose increases, the viscosity of the new type of recycled roof grouting material for mines increases.

[0073] The compressive strength of the solidified material after grouting with the novel recycled roof grouting slurry obtained in Examples 1-5 and curing for 28 days is shown in Table 3.

[0074] Table 3

[0075]

[0076] Example 6

[0077] Similar to Example 1, except that a new type of grouting slurry for recycled roof slabs in mines comprises, by weight, 40 parts clay, 8 parts ordinary silicate cement, 4.5 parts quicklime, 0.25 parts sodium silicate solution, 0.25 parts calcium chloride, and 0.3 parts hydroxypropyl methylcellulose.

[0078] Example 7

[0079] Similar to Example 1, except that a new type of grouting slurry for recycled roof slabs in mines comprises, by weight, 60 parts clay, 5 parts ordinary silicate cement, 7 parts quicklime, 0.3 parts sodium silicate solution, 0.2 parts calcium chloride, and 0.75 parts hydroxypropyl methylcellulose.

[0080] Comparative Example 1

[0081] Similar to Example 1, except that yellow mud slurry is used as the grouting slurry for the mine's recycled roof, namely N50C0S0.

[0082] Comparative Example 2

[0083] Similar to Example 1, except that quicklime is added only to the yellow mud slurry, and the resulting mine recycled roof grouting slurry is N50C0S6.

[0084] Comparative Example 3

[0085] Similar to Example 1, except that ordinary silicate cement is added only to the yellow mud slurry, and the resulting recycled roof grout for mining is N50C6S0.

[0086] Comparative Example 4

[0087] Similar to Example 1, except that only ordinary silicate cement and quicklime are added to the yellow mud slurry, and the resulting recycled roof grout for mining is N50C6S6.

[0088] Comparative Example 5

[0089] Similar to Example 1, except that only ordinary silicate cement and admixtures are added to the yellow mud slurry, and the resulting recycled roof grout for mining is N50C6S0-W0.5.

[0090] Comparative Example 6

[0091] Similar to Example 1, except that hydroxypropyl methylcellulose was not added, and the resulting novel grouting slurry for mine recycled roof is N50C6S6-W0.5.

[0092] Comparative Example 7 (selecting hydroxypropyl methylcellulose with a viscosity of less than 150,000)

[0093] Same as Example 1, except that the viscosity of hydroxypropyl methylcellulose is 100,000.

[0094] Comparative Example 8 (selecting hydroxypropyl methylcellulose with a viscosity greater than 250,000)

[0095] Same as Example 1, except that the viscosity of hydroxypropyl methylcellulose is 300,000.

[0096] The changes in the workable time of the grouting slurries obtained in Comparative Examples 2-6 are shown in the figure. Figure 5 ,Depend on Figure 5 It is evident that different raw material compositions have a corresponding impact on the workable time of the grouting material. Studies show that a longer workable time for freshly mixed grout is beneficial for the flow of the grouting material in the roadway. The different raw material compositions significantly affect the workable time of the grout because, under high water-cement ratio conditions, the grout dispersion distance is larger, making it difficult for a reaction to occur in a short time. Pure yellow mud slurry (N50C0S0) does not set for a long time, resulting in a longer workable time, which is not shown in the figure below. Research found that the addition of lime helps extend the workable time of the grout. Compared to the N50C6S0 group, the N50C6S6 group's workable time was extended by 13 hours due to the addition of lime. The introduction of admixtures water glass and calcium chloride inhibited the extension of the workable time. Due to the introduction of admixtures, the N50C6S0-W group's workable time was reduced by 0.5 hours compared to the N50C6S0 group.

[0097] The viscosity changes of the grouting slurries obtained in Comparative Examples 1-6 are shown in the figure. Figure 6 ,Depend on Figure 6 It can be seen that under high water-cement ratio conditions, the viscosity of freshly mixed grouting materials does not differ significantly.

[0098] Figure 7 The diagram shows the interfacial bonding between the hardened aggregate and the grout obtained in Examples 1, 4, and 6. Figure 7 It can be seen that the bonding between the grout and the rock interface becomes tighter due to the addition of hydroxypropyl methylcellulose. Figure 8This is a comparison chart of the workable time of the grouting slurry obtained in Example 1 and Comparative Examples 7 and 8. Figure 9 This is a comparison chart of the viscosity of the grout obtained in Example 1 and Comparative Examples 7 and 8.

[0099] The compressive strength of the solidified bodies of the grouting slurries obtained in Comparative Examples 1-8 after 28 days of curing is shown in Table 4.

[0100] Table 4

[0101]

[0102] Due to the addition of hydroxypropyl methylcellulose, the workable time of the novel recycled roof grouting material for mines obtained in Example 1 is reduced to 4.55 hours, and the grout hardened solid has a compressive strength of 1.42 MPa after 28 days.

[0103] Compared with Comparative Example 4, the addition of hydroxypropyl methylcellulose and additives in Example 1 increased the compressive strength by 57.8% after 28 days, showing a significant strengthening effect.

[0104] Compared with Comparative Example 6, the addition of hydroxypropyl methylcellulose in Example 1 increased the compressive strength by 46.4% after 28 days.

[0105] This invention uses clay as the main raw material to design and prepare a green and low-cost novel grouting material for recycled roof in mines. The addition of hydroxypropyl methylcellulose can effectively adjust the workable time of the grouting material and increase the bonding ability between the grout and the rock interface. At the same time, the introduction of admixtures can further improve the mechanical properties of its hardened solidified body, ultimately obtaining a green, low-cost and high-performance novel grouting material for recycled roof in coal mines.

[0106] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A mine roof reclamation grout slurry, characterized by, By weight, it consists of 40-60 parts clay, 4-8 parts ordinary silicate cement, 4-8 parts quicklime, 0.3-0.7 parts admixture, 0.2-0.8 parts hydroxypropyl methylcellulose, and water; The viscosity of the hydroxypropyl methylcellulose is 150,000 to 250,000. The additive is composed of sodium silicate solution and calcium chloride in a mass ratio of 1 to 1.5:1; The preparation method of the recycled roof grout for mining includes the following steps: S1. Mix sodium silicate solution and calcium chloride, stir until homogeneous, and react to obtain an additive; S2. Mix clay and water, stir until uniform, and allow the slurry to settle to obtain yellow mud slurry; S3. Mix ordinary silicate cement, quicklime, admixtures, hydroxypropyl methylcellulose and yellow mud slurry, and stir until uniform to obtain a mine recycled roof grouting slurry; The mass ratio of water to clay is 1-4:1; The additive is composed of sodium silicate solution and calcium chloride in a mass ratio of 1 to 1.2:

1.

2. A mine roof grouting slurry according to claim 1, characterized in that, The reaction temperature in S1 is 18–25℃, and the reaction time is 2–6 hours.

3. The mine recycled roof grouting slurry according to claim 1, characterized in that, The slurry settling time is 12–24 hours.

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