Grouting material for rapid repair of coal mine tunnel and preparation process

Abstract

The invention discloses a grouting material for rapid repair of a coal mine tunnel and a preparation process of the grouting material. The grouting material comprises a material A, a material B and water, the material A comprises sulphoaluminate cement clinker, metakaolin, a retarder and a defoaming agent; the material B comprises anhydrite, slaked lime, an alkaline activator, a defoaming agent, calcium nitrite, a rheological agent and a water reducing agent, and the technical problems that a traditional CSA material is insufficient in early strength, poor in fluidity and reduced in later strength are solved by doping the modified admixture and the mineral admixture.

Description

Technical Field

[0001] This invention belongs to the field of coal mining roadway repair technology, and particularly relates to a grouting material for rapid repair of coal mine roadways. Background Technology

[0002] With the continuous development of the coal industry, the depth of coal mining is gradually increasing, and the geological structure in deep mines is becoming more and more complex. Loose and broken coal and rock masses are common, which can easily lead to safety accidents such as roof falls, collapses, and water inrushes, affecting the safe mining of coal mines. Grouting reinforcement, as a new type of coal mine roadway reinforcement measure, can effectively enhance the strength and stability of the surrounding rock. Calcium sulfoaluminate cement (CSA) has become a key material for grouting repair of coal mine roadways due to its rapid setting, ultra-early strength, high strength, freeze-thaw resistance, impermeability, corrosion resistance, and micro-expansion. However, at present, there is still a dynamic balance problem between setting time and mechanical properties in its application: too rapid setting can easily lead to insufficient grout fluidity, affecting the filling effect of grout in the cracks, while the high water-cement ratio under the high fluidity requirement may weaken the early strength. Therefore, it is urgent to improve the working performance of CSA through material modification to achieve integrated performance of "controllable rapid setting-high strength-durability", provide theoretical support for rapid repair of cracks in deep coal mines, and realize the strategic needs of green, low-carbon and long-term safe operation and maintenance of coal mines. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a grouting material and its preparation process for rapid repair of coal mine roadways, which solves the technical problems of insufficient early strength, poor fluidity, and subsequent strength reduction of traditional CSA materials by adding modified admixtures and mineral admixtures.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a grouting material for rapid repair of coal mine roadways, comprising material A, material B, and water; Material A includes sulfoaluminate cement clinker, metakaolin, retarder, and defoamer; Material B includes anhydrite, quicklime, alkaline activator, defoamer, calcium nitrite, rheology modifier, and water-reducing agent.

[0005] Preferably, it also includes a thickener.

[0006] Preferably, the sulfoaluminate cement clinker in material A is R·SAC42.5 cement clinker, and the retarder is boric acid retarder.

[0007] Preferably, the anhydrite in material B is gypsum dihydrate (CaSO4-2H2O), the water-reducing agent is polycarboxylate water-reducing agent, the alkaline activator is sodium aluminate, and the rheology modifier is polyvinyl alcohol rheology modifier.

[0008] A preparation process for a grouting material for rapid repair of coal mine roadways, the preparation process including: Preparation of A component: Weigh 450 parts of sulfoaluminate cement clinker, 50 parts of metakaolin, 2 parts of retarder, 0.3 parts of defoamer, and 300 parts of water, mix and stir until uniform and free of particles; For the preparation of material B, weigh 420 parts of anhydrite, 80 parts of quicklime, 4 parts of alkaline activator, 0.3 parts of defoamer, 1 part of calcium nitrite, 6 parts of rheology modifier, 0.6 parts of water-reducing agent, and mix with 300 parts of water until uniform and free of particles. Mix liquid A and liquid B at a volume ratio of 1:1 and stir thoroughly to form an ultra-early strength, high fluidity CSA grouting slurry.

[0009] Compared with the prior art, the beneficial effects of the present invention are: After adding metakaolin, the early strength of CSA gradually decreases, while the later strength shows a trend of first increasing and then decreasing. The cement strength increases with age, and the strength reduction phenomenon disappears. In terms of mechanical properties, the replacement of sulfur-aluminum clinker with metakaolin leads to a decrease in the early strength of cement, but it is beneficial to improve the later strength and suppress the strength reduction of cement.

[0010] By adding modified additives and mineral admixtures, the technical problems of insufficient early strength, poor fluidity, and later strength reduction of traditional CSA materials can be solved. Attached Figure Description

[0011] Figure 1 This is a graph showing the increase in mechanical properties of the CSA material of this invention over age.

[0012] Figure 2 This is the XRD pattern of the CSA material of this invention.

[0013] Figure 3 The image shows the SEM microstructure of the CSA material of this invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Example

[0016] See appendix Figure 1-3 As shown, a grouting material for rapid repair of coal mine roadways includes material A, material B, and water; Material A includes sulfoaluminate cement clinker, metakaolin, retarder, and defoamer; Material B includes anhydrite, quicklime, alkaline activator, defoamer, calcium nitrite, rheology modifier, and water-reducing agent.

[0017] It also includes thickeners.

[0018] The sulfoaluminate cement clinker in material A is R·SAC42.5 cement clinker, and the retarder is boric acid retarder.

[0019] The gypsum in material B is gypsum dihydrate (CaSO4-2H2O), the water-reducing agent is polycarboxylate water-reducing agent, the alkaline activator is sodium aluminate, and the rheology modifier is polyvinyl alcohol rheology modifier.

[0020] The preparation process of grouting materials for rapid repair of coal mine roadways includes: Preparation of A component: Weigh 450 parts of sulfoaluminate cement clinker, 50 parts of metakaolin, 2 parts of retarder, 0.3 parts of defoamer, and 300 parts of water, mix and stir until uniform and free of particles; For the preparation of material B, weigh 420 parts of anhydrite, 80 parts of quicklime, 4 parts of alkaline activator, 0.3 parts of defoamer, 1 part of calcium nitrite, 6 parts of rheology modifier, 0.6 parts of water-reducing agent, and mix with 300 parts of water until uniform and free of particles. Mix liquid A and liquid B at a volume ratio of 1:1 and stir thoroughly to form an ultra-early strength, high fluidity CSA grouting slurry.

[0021] Working principle: During grouting, high-pressure grouting equipment is used to inject the mixed grout into the tunnel fissures. The high fluidity and permeability of the grout fully fill the micro-fissures and broken rock masses. After grouting is completed, the repaired area is naturally cured, and the ambient temperature is controlled at 20±1℃ and the humidity at 60±5% to promote the full hydration reaction of ettringite and CSH gel and form a dense composite structure. Material performance testing showed that after natural curing, the uniaxial compressive strength reached 14 MPa after 2 hours of hydration, and 60%~80% of the peak strength after 4 hours. The 28-day compressive strength was 43.2 MPa, meeting the needs of rapid repair of coal mine roadways. The fluidity was ≤12s, indicating strong grout permeability and the ability to fill micro-cracks. The synergistic effect of metakaolin and compound admixtures ensured continuous strength growth after 28 days of hydration, inhibiting the strength reduction of CSA materials. The initial setting time was 6~8 minutes, and the final setting time was ≤18 minutes, providing sufficient time for grouting operations. Figure 1 It can be seen that after adding metakaolin, the early strength of CSA gradually decreases, while the later strength shows a trend of first increasing and then decreasing. The cement strength increases with age, and the strength reduction phenomenon disappears. In terms of mechanical properties, the replacement of sulfur-aluminum clinker with metakaolin leads to a decrease in the early strength of cement, but it is beneficial to improve the later strength and suppress the strength reduction of cement. By adjusting the mix proportion of sulfoaluminate cement-based grouting materials and introducing modified materials, their comprehensive performance was significantly improved. This study combined X-ray diffraction (XRD) phase analysis with scanning electron microscopy (SEM) morphology characterization to analyze the changes in hydration products and microstructure of modified CSA. The conclusions are as follows: The hydration products of the CSA system are related to the content of sulfoaluminate clinker and anhydrite. The main hydration products of C4A3S are ettringite and AH3, while the hydration product of C2S is CSH gel. The early strength and initial setting time of CSA materials are determined by the early formation of ettringite, while the increase in later strength is determined by the hydration of C2S. As the hydration reaction proceeds, the diffraction peak of anhydrite decreases significantly after 1 day of hydration, the diffraction peak of ettringite gradually increases, and the diffraction peak of anhydrous calcium sulfoaluminate gradually decreases, indicating that the modified CSA material has a higher degree of hydration and a more complete reaction. Figure 2 It is known that the hydration products of the CSA system are related to the content of sulfur-aluminum clinker and anhydrite. The main hydration products of C4A3S are ettringite and AH3, while the hydration product of C2S is CSH gel. The early strength and initial setting time of CSA materials are determined by the early formation of ettringite, while the increase in later strength is determined by the hydration of C2S. The introduction of metakaolin significantly improves the microstructure and mechanical properties of CSA, not only increasing early strength but also effectively solving the problem of later strength reduction of CSA by inhibiting ettringite crystallization and optimizing the composition of hydration products. Depend on Figure 3It is known that the hydration products of the CSA system are mainly ettringite, AFm, and CSH gel. In the early stage of hydration, slender needle-like and rod-shaped ettringite overlaps or is embedded in AFm. As the hydration reaction proceeds, the ettringite undergoes crystallization and grows into columnar structures with larger thickness and shorter length. AFm mainly occurs in hexagonal plate-like or tabular form, while CSH gel appears as flocculent covering the surface of ettringite or filling the structural voids. In the SEM microstructure, the modified CSA material has less CSH gel and more voids in the early stage of hydration, while the CSH content increases in the later stage, resulting in a denser structure.

[0022] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all changes falling within the meaning and scope of the equivalents of the claims be included within the present invention, and no reference numerals in the claims should be regarded as limiting the scope of the claims.

[0023] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A grouting material for rapid repair of coal mine roadways, characterized in that: Includes component A, component B, and water; Material A includes sulfoaluminate cement clinker, metakaolin, retarder, and defoamer; Material B includes anhydrite, quicklime, alkaline activator, defoamer, calcium nitrite, rheology modifier, and water-reducing agent.

2. The grouting material for rapid repair of coal mine roadways according to claim 1, characterized in that: It also includes thickeners.

3. The grouting material for rapid repair of coal mine roadways according to claim 1, characterized in that: The sulfoaluminate cement clinker in material A is R·SAC42.5 cement clinker, and the retarder is boric acid retarder.

4. The grouting material for rapid repair of coal mine roadways according to claim 1, characterized in that: The gypsum in material B is gypsum dihydrate (CaSO4-2H2O), the water-reducing agent is polycarboxylate water-reducing agent, the alkaline activator is sodium aluminate, and the rheology modifier is polyvinyl alcohol rheology modifier.

5. A preparation process for a grouting material for rapid repair of coal mine roadways, characterized in that: Its preparation process includes: Preparation of A component: Weigh 450 parts of sulfoaluminate cement clinker, 50 parts of metakaolin, 2 parts of retarder, 0.3 parts of defoamer, and 300 parts of water, mix and stir until uniform and free of particles; For the preparation of material B, weigh 420 parts of anhydrite, 80 parts of quicklime, 4 parts of alkaline activator, 0.3 parts of defoamer, 1 part of calcium nitrite, 6 parts of rheology modifier, 0.6 parts of water-reducing agent, and mix with 300 parts of water until uniform and free of particles. Mix liquid A and liquid B at a volume ratio of 1:1 and stir thoroughly to form an ultra-early strength, high fluidity CSA grouting slurry.

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