Low-temperature foaming inorganic filling material as well as preparation method and application thereof

Abstract

The invention relates to a low-temperature foaming inorganic filling material as well as a preparation method and application thereof, and belongs to the field of grouting filling reinforcement. Aiming at the problems of low foaming efficiency and the like of an existing inorganic system at low temperature, cement and sodium silicate are used as main components of a filling material, carbonate is used as a main foaming agent, dolomite is used as an auxiliary foaming agent, and stage release of carbon dioxide is realized through cooperation of organic phosphonic acid and citric acid; the composite foam stabilizing system is constructed by combining nano silicon dioxide and sodium carboxymethyl cellulose. The filling material can be quickly foamed at low temperature, is high in foaming rate, good in stability and excellent in compressive strength, the foaming ratio at 5 DEG C is greater than or equal to 5.4 times, the half-life period is greater than or equal to 35min, and the 7d compressive strength is greater than or equal to 8.4 MPa according to tests, the technical problems that a traditional inorganic grouting material is low in low-temperature foaming efficiency and poor in foam stability are solved, and the filling material is suitable for coal mine underground low-temperature grouting engineering.

Description

Technical Field

[0001] This invention belongs to the field of grouting and filling reinforcement, and particularly relates to a low-temperature foaming inorganic filler material, its preparation method and application. The filler material can foam rapidly at low temperatures, with high foaming rate, good stability and good compressive strength. Background Technology

[0002] Grouting technology utilizes specialized equipment to inject low-viscosity chemical grout into fissures or loose rock masses. The grout gels and solidifies within a very short time, forming a three-dimensional network of solidified material. This re-bonds the originally broken and loose structure into a continuous and complete load-bearing whole, thereby repairing structural defects and improving load-bearing capacity and seepage prevention. The process is simple and highly effective, and has been widely applied in recent years in fields such as mining.

[0003] Two-component chemical foaming grout is made by mixing two independent components, A and B, on-site. After injection into the formation, it reacts, expands, and solidifies rapidly, forming an integrated reinforcement-sealing structure. Depending on the working conditions, a catalyst can be added appropriately to achieve rapid leak sealing in formations with high water velocity, with particularly significant effects on surrounding rock reinforcement and seepage prevention. The two-component foaming system with inorganic filler as its core has both high-ratio foaming and instant curing capabilities, enabling efficient filling and sealing of water inflow in fractured formations or underground coal mine fissures. Its low-temperature reaction characteristics ensure a safe gas environment, and it is solvent-free, flame-retardant, and low-cost, with simple construction and significantly improved project efficiency. Currently, commonly used inorganic grouting materials are mainly divided into two categories: cement-based and water glass-based. Cement-based materials are low in cost and high in strength, but have poor foaming ability, high heat release, and poor fluidity. Existing inorganic systems generally have low foaming efficiency, unstable foam, and difficult-to-control setting time at low temperatures, which affects mechanical properties and restricts construction quality and efficiency.

[0004] Foaming agents used in grouting materials mainly include hydrogen peroxide foaming agents and carbonate foaming agents. At low temperatures, the decomposition rate of hydrogen peroxide slows down significantly, and it may even fail to decompose effectively, resulting in a substantial reduction in foaming performance. This prevents the generation of sufficient gas to form an ideal foam structure, affecting the material's foaming properties and final porosity and other performance indicators. Hydrogen peroxide foaming agents are unstable and prone to decomposition failure, requiring specific storage conditions such as low temperature, protection from light, and airtight sealing. Otherwise, premature decomposition will cause them to lose their foaming effect, increasing the difficulty and cost of use and storage.

[0005] Carbonate foaming agents are widely used in grouting foaming agents due to their low cost, good safety, and good low-temperature applicability. However, the amount of carbon dioxide gas produced by the complete decomposition of sodium bicarbonate per unit mass is low, requiring a large addition amount to achieve a good foaming effect, which adversely affects other properties of the material (such as strength). Simultaneously, an excessively fast foaming rate results in the concentrated release of CO2 within 10-30 seconds, with bubbles merging into large millimeter-sized bubbles, making it impossible to continuously and stably provide good foaming performance for the grouting material. Furthermore, poor foam stability and a fragile foam layer make it susceptible to breakage due to external factors such as shear forces generated by material flow during grouting, its own gravity, and downhole humidity, making it difficult for the foam to maintain uniformity and stability for extended periods, severely impacting the performance of the grouting material.

[0006] Therefore, developing an inorganic filler material with good low-temperature foaming performance, high stability, low cost, and suitability for coal mine grouting is of great practical significance. Summary of the Invention

[0007] This invention provides an inorganic filler material suitable for low-temperature environments, its preparation method, and its application. It uses carbonate as the main foaming agent and dolomite as an auxiliary foaming agent, achieving phased release of carbon dioxide through the synergistic effect of organophosphonic acid and citric acid. A composite foam-stabilizing system is constructed by combining nano-silica and sodium carboxymethyl cellulose, significantly reducing the amount of carbonate used while simultaneously improving the foaming ratio and compressive strength. This effectively solves the problems of high dosage, poor foam stability, and weak compressive strength associated with traditional carbonate foaming agents in low-temperature grouting.

[0008] This invention provides a low-temperature foaming inorganic filler material, comprising component A and component B, wherein:

[0009] Component A comprises the following raw materials in parts by weight: 10-40 parts cement, 10-30 parts sodium silicate, 10-30 parts dolomite, 1-5 parts foam stabilizer, 2-10 parts foaming agent, 2-6 parts surfactant, and 30-60 parts water.

[0010] Component B comprises the following raw materials in parts by weight: 5-15 parts organophosphonic acid, 3-10 parts citric acid, 5-15 parts additives, and 30-70 parts water.

[0011] The mass ratio of component A to component B is 1:1.

[0012] Preferably, the cement component A is at least one of silicate cement, phosphate cement, and aluminosilicate cement.

[0013] Preferably, the foaming agent of component A is at least one of sodium bicarbonate, potassium bicarbonate, sodium carbonate, or potassium carbonate.

[0014] Preferably, the dolomite has a particle size of 1-50 micrometers, more preferably 5-20 μm, and the sodium silicate has a modulus of 2.4-2.8.

[0015] Preferably, the foam stabilizer in component A is nano-silica and sodium carboxymethyl cellulose, and the mass ratio of nano-silica to sodium carboxymethyl cellulose is 10:1-3.

[0016] Preferably, the surfactant in component A is one or a mixture of Tween 80, Span 60, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate.

[0017] Preferably, the B component organic phosphoric acid is at least one selected from aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, methylamine dimethylphosphonic acid, glycine dimethylphosphonic acid, ethylenediaminetetramethylenephosphonic acid, and aminoethylidene diphosphonic acid.

[0018] Preferably, the B component additive is at least one of a water-reducing agent, an early-strength agent, and a retarder. Preferably, the water-reducing agent is at least one of a polycarboxylate-based water-reducing agent and a melamine resin-based water-reducing agent; the early-strength agent is at least one of sodium gluconate and sodium hexametaphosphate; and the retarder is at least one of triethanolamine and sodium formate.

[0019] Preferably, the present invention also provides a method for preparing the above-mentioned low-temperature foamed inorganic filler material, comprising the following steps:

[0020] (1) Preparation of component A: Weigh cement, sodium silicate, dolomite, foam stabilizer, foaming agent, surfactant and water according to the weight parts, put them in a mixer and stir evenly to obtain a uniform component A slurry.

[0021] (2) Preparation of component B: Weigh out the organic phosphonic acid, citric acid, additives and water by weight, place them in a mixer and stir evenly to obtain a uniform solution of component B.

[0022] (3) Mixed use: When using, mix component A and component B at a mass ratio of 1:1 to obtain the low-temperature foamed inorganic filler material.

[0023] Preferably, in step (1), the stirring speed is 300-500 r / min and the stirring time is 5-10 minutes. In step (2), the stirring speed is 200-400 r / min and the stirring time is 3-8 minutes. In step (3), the stirring speed is 400-600 r / min and the stirring time is 1-5 minutes.

[0024] Preferably, the present invention also provides an application of a low-temperature foamed inorganic filler material in a coal mine, comprising the following steps: adding material A and material B to the grouting system in a mass ratio of 1:1 using a grouting pump, and then using a grouting machine for curing and filling.

[0025] This invention uses cement and sodium silicate as the main components of the filler material. Silicate ions can react with calcium hydroxide produced during cement hydration to form hydrated calcium silicate gel, which helps to improve the early strength of the filler structure more quickly. In addition, the viscous substances such as silicate colloids produced by the hydrolysis of sodium silicate make the internal structure of the filler more compact, reduce porosity, and avoid insufficient strength of the filler due to local loose structure.

[0026] This invention uses carbonate as the main foaming agent, which reacts pre-with organophosphoric acid to form carbon dioxide. The resulting sodium organophosphonate or potassium organophosphate has surface activity, reducing gas-liquid interfacial tension, forming a dense liquid film, reducing bubble coalescence and rupture, and improving foam stability. Dolomite, whose main component is calcium magnesium carbonate, has poorer dispersibility in water than sodium carbonate-based main foaming agents, and its carbon dioxide generation rate is slower, achieving a second-stage foaming. This invention uses a staged foaming method, which avoids bubble coalescence and rupture, and provides a continuous and stable foam system even at low temperatures. Compared to using one acid alone, the combination of organophosphoric acid and citric acid significantly increases the reaction rate of sodium carbonate and dolomite decomposition to produce carbon dioxide, ensuring sufficient carbon dioxide gas for good foaming effect at relatively low temperatures.

[0027] The present invention preferably uses dolomite with a particle size of 1-50 micrometers, more preferably 5-20 micrometers. This is beneficial in two ways: firstly, it facilitates the reaction with acid to form carbon dioxide, increasing the foaming ratio; secondly, unreacted dolomite can act as a filler, dispersing in the voids between cement particles within the cement slurry, thus improving the compressive strength of the filler. The smaller the dolomite particle size, the faster the foaming reaction rate; the greater the amount of dolomite added, the higher the foaming ratio of the material. By controlling the amount and particle size of dolomite added, the foaming ratio, foaming rate, and strength of the solidified foam can be adjusted to meet the grouting needs of different application scenarios.

[0028] The foam stabilizer used in this invention is a composite foam stabilizer consisting of nano-silica and sodium carboxymethyl cellulose in a mass ratio of 10:1-3. Nano-silica forms a nanofluid in water, creating a physical barrier on the liquid film surface that hinders gas diffusion and delays foam breakage. Simultaneously, nano-SiO2 reacts with Ca(OH)2, a cement hydration product, in a pozzolanic reaction to generate secondary CSH gel, enhancing the bonding strength at the foam-matrix interface. The carboxyl groups in the sodium carboxymethyl cellulose molecular chain combine with water molecules to form hydrogen bonds, increasing the grout viscosity and improving foam stability. Furthermore, carboxymethyl cellulose acts as an emulsifier and dispersant, preventing the agglomeration of nano-silica. Together, these two components synergistically improve the foam stability of the grouting system.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention adopts a two-component design. After the A component and the B component are mixed, they can quickly foam at low temperature. The foaming rate is high and the foam stability is good. It overcomes the problem that the traditional carbonate foaming agent has reduced reactivity due to low temperature and requires a large increase in dosage. It can successfully complete the grouting and filling operation under low temperature conditions and expand the applicable temperature range of inorganic filler materials.

[0031] (2) By rationally combining carbonates and dolomite, and combining the synergistic effect of organophosphonic acid and citric acid, carbon dioxide was released in stages, making the foaming process more uniform and stable, and the foaming ratio was improved. Furthermore, thanks to the synergistic and stable foam structure of nano-silica and carboxymethyl cellulose, the compressive strength of the filler was also significantly improved, better meeting the engineering requirements for the strength and stability of the filler.

[0032] (3) The raw materials used are all inorganic materials or environmentally friendly organic compounds, which are inexpensive and do not pollute the environment, in line with the development trend of green and environmental protection.

[0033] (4) The material has good fluidity and is easy to construct. It can be applied to coal mine grouting projects under different geological conditions and has a wide range of application prospects. Detailed Implementation

[0034] To more clearly illustrate the purpose, technical solution, and advantages of this invention, the technical solution of this invention will be described in detail below through specific embodiments. It should be noted that these embodiments are only for illustrating this invention and not for limiting its scope of protection; the actual scope of protection of this invention should be determined by the claims.

[0035] Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available. Unless otherwise specified, each part by weight or each portion in the following examples is 1 g.

[0036] I. Preparation of a low-temperature foaming inorganic filler material.

[0037] The present invention relates to a method for preparing a low-temperature foamed inorganic filler material, specifically comprising the following steps:

[0038] (1) Preparation of component A: Weigh each raw material according to the above weight parts, place them in a mixer, and stir for 10 minutes at a speed of 300 r / min to obtain a uniform slurry of component A.

[0039] (2) Preparation of component B: Weigh each raw material according to the above weight proportions, place them in a mixer, and stir for 8 minutes at a speed of 200 r / min to obtain a uniform solution of component B.

[0040] (3) Mixed use: When using, mix component A and component B at a mass ratio of 1:1 and stir for 5 minutes at a speed of 400 r / min to obtain the low-temperature foamed inorganic filler material.

[0041] Table 1: The mass fractions (g) of each component in Examples 1-4 are as follows.

[0042]

[0043] Example 6

[0044] The difference from Example 1 is that the dolomite has a particle size of 1 μm, while the other conditions are the same as in Example 1.

[0045] Example 7

[0046] The difference from Example 1 is that the dolomite has a particle size of 10 μm, while the other conditions are the same as in Example 1.

[0047] Example 8

[0048] The difference from Example 1 is that the dolomite has a particle size of 20 μm, while the other conditions are the same as in Example 1.

[0049] Example 9

[0050] The difference from Example 1 is that the dolomite has a particle size of 40 μm, while the other conditions are the same as in Example 1.

[0051] Table 2: The mass fractions (g) of each component in Comparative Examples 1-7 are as follows.

[0052]

[0053]

[0054] II. Performance Evaluation:

[0055] The application of the low-temperature foamed inorganic filler material prepared in the examples and comparative examples in coal mine grouting includes the following steps: using a grouting pump to add material A and material B to the grouting system at a mass ratio of 1:1, and using a grouting machine to perform curing and filling.

[0056] 1. Material mechanical strength testing

[0057] In accordance with the requirements of AQ / T 1089-2020 standard, the prepared material slurry was first poured into a 10cm×10cm×10cm mold. After 24 hours, the mold was removed, and the test samples were placed in environments of 25℃ and 5℃ with a relative humidity of 50% for 7 days. The compressive strength of the material at 7 days was tested, and the average value of 5 test samples was selected for each experimental test.

[0058] 2. Foaming ratio

[0059] The foaming ratio was tested at 25℃ and 5℃ respectively, in accordance with the requirements of JC / T 266-2011 "Foamed Concrete" standard.

[0060] 3. Foam half-life

[0061] At 5°C, the prepared components A and B are mixed in a mass ratio of 1:1 and stirred at a stirring speed of 400 r / min for 6 minutes to allow them to fully foam and produce uniform foam. The foam is then transferred to a pre-prepared measuring container, and the time required for the foam to defoam to half its original size is recorded as the foam half-life, which is used to measure the stability of the foam.

[0062] Table 3. Performance of grouting materials in different embodiments and comparative examples.

[0063]

[0064]

[0065] According to the test results in Table 3, the low-temperature foaming inorganic filler material of this invention foams rapidly at low temperatures, with a foaming ratio ≥ 4.6 times at 5℃ and a foam half-life ≥ 30 min. It exhibits high foaming rate and good foam stability, overcoming the problems of reduced reactivity and significantly increased dosage required by traditional carbonate foaming agents at low temperatures, as well as poor foam stability. Furthermore, the prepared low-temperature foaming inorganic filler material demonstrates excellent filling performance in coal mine filling: a compressive strength ≥ 7.5 MPa after curing at 5℃ for 7 days; and a compressive strength ≥ 10 MPa after curing at 25℃ for 7 days. It can successfully complete grouting filling operations under low-temperature conditions, expanding the applicable temperature range of inorganic filler materials.

[0066] As shown in Examples 1 and 6-9, the particle size of dolomite plays a decisive role in the foaming ratio and compressive strength of the grouting material. If the particle size is too small, it reacts rapidly with acid and produces carbon dioxide quickly, but it is prone to agglomeration and has poor dispersibility; if the particle size is too large, it is prone to sedimentation and difficult to suspend evenly. Controlling the dolomite particle size to 1–50 μm, preferably 5–20 μm, can balance high reactivity and dispersion stability in low-temperature environments: on the one hand, an appropriate amount of dolomite reacts rapidly with acid to generate CO2, significantly increasing the foaming ratio; on the other hand, unreacted fine dolomite particles uniformly fill the micro-gap between cement particles, acting as micro-aggregate reinforcement and improving the compressive strength of the solidified body. By simultaneously adjusting the dosage and particle size of dolomite, the foaming rate, foaming ratio, and final compressive strength can be precisely controlled to meet the grouting requirements of different working conditions.

[0067] A comparison of Example 1 and Comparative Examples 1-2 reveals that Comparative Example 1, using only sodium bicarbonate, exhibits reduced reactivity at low temperatures, making it difficult to guarantee sufficient and stable carbon dioxide production, resulting in poor foaming performance and limited foaming ratio. Comparative Example 2, using only dolomite as a foaming agent, exhibits a relatively slow rate of carbon dioxide generation and a low foaming ratio, as evidenced by Table 3, where its foaming ratio and foam half-life at 5°C are significantly lower than those of Example 1. In contrast, Example 1 utilizes a combination of carbonate and dolomite. The carbonate first reacts with organic phosphoric acid to form carbon dioxide, while the rate of carbon dioxide generation from dolomite and acid is slower, achieving a second-stage foaming process. This invention employs a staged foaming method to avoid bubble aggregation and breakage, providing a continuous and stable foam system even at low temperatures.

[0068] A comparison of Example 1 and Comparative Examples 3-4 shows that Comparative Examples 3-4, using a single citric acid or organophosphoric acid system at 25°C, can achieve compressive strength and expansion ratio similar to Example 1. However, at a low temperature of 5°C, their compressive strength, expansion ratio, and foam half-life all decrease significantly. In contrast, Example 1, by combining organophosphoric acid and citric acid, can simultaneously activate sodium bicarbonate and dolomite at low temperatures, continuously producing carbon dioxide in stages, thereby ensuring sufficient foaming. The underlying mechanism is speculated to be that the sodium (or potassium) organophosphonate generated by the reaction of dolomite and organophosphoric acid possesses surface activity, reducing gas-liquid interfacial tension, forming a dense liquid film, inhibiting bubble coalescence and rupture, and improving foam stability. Simultaneously, the unreacted dolomite particles act as micro-aggregates, further enhancing the compressive strength of the filler.

[0069] A comparison of Example 1 and Comparative Examples 5-7 shows that Comparative Example 5 did not add a foam stabilizer, while Comparative Examples 6-7 used only either nano-silica or sodium carboxymethyl cellulose as a foam stabilizer, resulting in poor foam stability and shorter foam half-lives than in Example 1. This, in turn, affected the uniformity and stability of the internal structure of the material, leading to performance indicators such as compressive strength and expansion ratio being less than ideal at both 25°C and 5°C compared to Example 1. Example 1 used nano-silica and sodium carboxymethyl cellulose as synergistic foam stabilizers. Nano-silica forms a nanofluid in water, delaying foam breakage. Simultaneously, nano-SiO2 reacts with the cement hydration product Ca(OH)2 in a pozzolanic reaction, generating secondary CSH gel, which improves compressive strength. Sodium carboxymethyl cellulose increases the viscosity of the slurry and also has emulsifying and dispersing effects, preventing the agglomeration of nano-SiO2. The synergistic effect of these two substances ensures high stability of the foam system at both room temperature and low temperature, thereby guaranteeing excellent compressive strength and foaming performance.

[0070] The above embodiments are merely examples to illustrate the present invention and are not intended to limit the possible implementations of the invention. Based on the disclosure of this invention, those skilled in the art can make various modifications and adjustments. It is neither possible nor necessary to list all possible implementations. Any modifications, equivalent substitutions, or improvements made within the basic principles and scope of this invention should be considered to fall within the protection scope of this invention.

Claims

1. A low-temperature foamed inorganic filler material, characterized in that, It includes component A and component B, wherein: Component A includes the following raw materials in parts by weight: 10-40 parts cement, 10-30 parts sodium silicate, 10-30 parts dolomite, 1-5 parts foam stabilizer, 2-10 parts foaming agent, 2-6 parts surfactant, and 30-60 parts water. Component B comprises the following raw materials in parts by weight: 5-15 parts organophosphonic acid, 3-10 parts citric acid, 5-15 parts additives, and 30-70 parts water. The foaming agent of component A is at least one of sodium bicarbonate, potassium bicarbonate, sodium carbonate, or potassium carbonate; the foam stabilizer of component A is nano silica and sodium carboxymethyl cellulose, and the mass ratio of nano silica to sodium carboxymethyl cellulose is 10:1-3. The mass ratio of component A to component B is 1:

1.

2. The low-temperature foamed inorganic filler material as described in claim 1, characterized in that, The cement component A is at least one of silicate cement, phosphate cement, and aluminosilicate cement.

3. The low-temperature foamed inorganic filler material as described in claim 1, characterized in that, The dolomite has an average particle size of 1-50 micrometers, and the sodium silicate has a modulus of 2.4-2.

8.

4. A low-temperature foamed inorganic filler material as described in any one of claims 1-3, characterized in that, The surfactant in component A is one or a mixture of Tween 80, Span 60, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate.

5. A low-temperature foamed inorganic filler material as described in any one of claims 1-3, characterized in that, The B component, organic phosphoric acid, is at least one of aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, methylamine dimethylphosphonic acid, glycine dimethylphosphonic acid, ethylenediaminetetramethylenephosphonic acid, and aminoethylidene diphosphonic acid.

6. A low-temperature foamed inorganic filler material as described in any one of claims 1-3, characterized in that, The B component additive is at least one of water-reducing agent, early-strength agent, and retarder.

7. The low-temperature foamed inorganic filler material as described in claim 6, characterized in that, The water-reducing agent is at least one of polycarboxylate-based water-reducing agents and melamine resin-based water-reducing agents; the early-strength agent is at least one of sodium gluconate and sodium hexametaphosphate; and the retarding agent is at least one of triethanolamine and sodium formate.

8. A method for preparing a low-temperature foamed inorganic filler material as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation of component A: Weigh cement, sodium silicate, dolomite, foam stabilizer, foaming agent, surfactant and water according to the weight parts, put them in a mixer and stir evenly to obtain a uniform component A slurry. (2) Preparation of component B: Weigh out the organic phosphonic acid, citric acid, additives and water by weight, place them in a mixer and stir evenly to obtain a uniform solution of component B. (3) Mixed use: When using, mix component A and component B at a mass ratio of 1:1 to obtain the low-temperature foamed inorganic filler material.

9. The method for preparing a low-temperature foamed inorganic filler material as described in claim 8, characterized in that, In step (1), the stirring speed is 300-500 r / min and the stirring time is 5-10 minutes; in step (2), the stirring speed is 200-400 r / min and the stirring time is 3-8 minutes; in step (3), the stirring speed is 400-600 r / min and the stirring time is 1-5 minutes.

10. The application of a low-temperature foamed inorganic filler material as described in any one of claims 1-7 and a low-temperature foamed inorganic filler material prepared by the method described in any one of claims 8-9 in a coal mine, comprising the following steps: The A and B materials are added to the grouting system in a 1:1 mass ratio using a grouting pump, and then cured and filled using a grouting machine.

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