Fiber-reinforced cement-based foam filling material and preparation method thereof

Abstract

The invention discloses a fiber-reinforced cement-based foam filling material and a preparation method thereof, and belongs to the technical field of building materials. The filling material is prepared from 50%-70% of cement, 5%-25% of activated coal gangue, 10%-20% of modified aluminum slag foaming agent, 1%-2% of polypropylene fiber, 0.5%-1% of basalt fiber and the balance water. The industrial waste aluminum slag and coal gangue are subjected to resource utilization, and the fiber reinforcement technology is combined, so that the problems that a traditional filling material is high in bleeding rate and poor in crack resistance, and the aluminum slag pollutes the environment are solved. The 28-day compressive strength of the filling material reaches 8-10 MPa, and the bleeding rate is 1t; and after 300 freezing and thawing cycles, the strength retention rate is greater than or equal to 90%, the heat conductivity coefficient is less than or equal to 0.25 W / (m.K), and the filling material is suitable for efficient and safe filling of the mine goaf.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a fiber-reinforced cement-based foam filling material and a preparation method thereof. Background Art

[0002] At present, the efficient utilization of mineral resources and the protection of mine environments have become important directions for the development of the industry. However, the mining industry faces a series of challenges and pain points: 1. A large amount of tailings and waste rocks generated by mining activities occupy land resources, pose safety hazards, and have high treatment costs; 2. The underground voids left after mining are prone to cause ground settlement, cracks, and even collapses, threatening the safety of personnel and surface facilities; 3. Traditional filling materials have problems such as poor connectivity and insufficient stability, and it is difficult to meet the requirements of modern mines for efficient and safe operations; 4. Industrial wastes such as aluminum slag generated during the aluminum electrolysis process are difficult to treat, have low resource utilization rates, and pose great environmental pollution risks.

[0003] Although traditional filling materials (such as CN 119504213 A) utilize solid wastes, they have problems such as high bleeding rate, poor freeze-thaw cycle performance, uneven fiber dispersion, and insufficient crack resistance. In addition, direct landfill of aluminum slag is likely to release AlN (generating NH3), polluting the environment. Summary of the Invention

[0004] One technical problem solved by the present invention is to provide a fiber-reinforced cement-based foam filling material, the 28-day compressive strength of which is 8 - 10 MPa, the bleeding rate is <1%, the strength retention rate after 300 freeze-thaw cycles is ≥90%, and the thermal conductivity is ≤0.25 W / (m·K), with excellent performance. Another technical problem to be solved by the present invention is to provide a preparation method of a fiber-reinforced cement-based foam filling material, which solves the problems of high bleeding rate, poor crack resistance of traditional filling materials, and environmental pollution of aluminum slag by resourcefully utilizing industrial wastes aluminum slag and coal gangue and combining fiber reinforcement technology.

[0005] Technical Solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A fiber-reinforced cement-based foam filling material is composed of the following components by weight fraction: 50% - 70% of cement, 5% - 25% of activated coal gangue, 10% - 20% of modified aluminum slag foaming agent, 1% - 2% of polypropylene fiber, 0.5% - 1% of basalt fiber, and the balance is water; preferably, it is composed of the following components by weight fraction: 50% - 65% of cement, 5% - 15% of activated coal gangue, 10% - 15% of modified aluminum slag foaming agent, 1% - 2% of polypropylene fiber, 0.5% - 0.8% of basalt fiber, and the balance is water.

[0007] For the fiber-reinforced cement-based foam filling material, the polypropylene fiber has a tensile strength of 450 - 600 MPa, an elastic modulus of 3.5 - 5.0 GPa, a fiber length of 6 - 20 mm, and a diameter of 15 - 35 μm; preferably, the polypropylene fiber has a tensile strength of 500 MPa, an elastic modulus of 4.0 - 5.0 GPa, a fiber length of 12 mm, and a diameter of 25 μm.

[0008] For the fiber-reinforced cement-based foam filling material, the basalt fiber has a tensile strength ≥ 800 MPa, an elastic modulus of 80 - 110 GPa, a fiber length of 12 - 18 mm, and a diameter of 10 - 20 μm; using polypropylene fiber and basalt fiber together can form a three-dimensional network structure, which helps to improve the stability of the porous structure; preferably, the basalt fiber has a tensile strength of 850 MPa, an elastic modulus of 90 - 100 GPa, a fiber length of 15 mm, and a diameter of 15 μm.

[0009] For the fiber-reinforced cement-based foam filling material, the cement is ordinary Portland cement with a strength grade of 42.5R.

[0010] For the fiber-reinforced cement-based foam filling material, the modified aluminum slag foaming agent is prepared by mixing aluminum slag and quicklime in a mass ratio of 0.3:1 - 0.4:1 and then calcining.

[0011] For the fiber-reinforced cement-based foam filling material, the calcination process is completed in two stages, specifically: the first stage is calcined at 800 - 900 °C for 1 - 2 hours to make the AlN oxidation rate ≥ 95%, completely eliminating the risk of NH3 release; the second stage is calcined at 1100 - 1200 °C for 0.5 - 1 hour to generate calcium aluminate (CA) and silicate minerals; preferably, the first stage is calcined at 850 °C for 1.5 hours; the second stage is calcined at 1150 °C for 1 hour.

[0012] For the fiber-reinforced cement-based foam filling material, the preparation method of activated coal gangue is: after crushing the coal gangue to a particle size ≤ 150 μm, it is stirred with a sodium silicate solution with a mass fraction of 5% - 10% at 60 - 80 °C for 30 minutes; Na in sodium silicate + reacts with Al2O3 on the surface of coal gangue to form aluminosilicate gel, releasing active SiO2 and Al 3+ , promoting the formation of C-S-H gel in subsequent hydration reactions; preferably, it is stirred with a sodium silicate solution with a mass fraction of 8% at 70 °C for 30 minutes, and the modulus of sodium silicate is 2.5 - 3.2; further preferably, the modulus of sodium silicate is 2.8.

[0013] For the described fiber-reinforced cementitious foam filling material, in the aluminum slag, Al2O3 ≥ 70% and AlN ≤ 10%; in the quicklime, CaO ≥ 90%; preferably, the content of Al2O3 in the aluminum slag is 78% and the content of AlN is 5%; the content of CaO in the quicklime is 92%.

[0014] The preparation method of the above fiber-reinforced cementitious foam filling material includes the following steps:

[0015] (1) Grind the modified aluminum slag foaming agent to a particle size ≤ 45μm through a planetary ball mill;

[0016] (2) Dry mix the ground modified aluminum slag foaming agent with cement, activated coal gangue, polypropylene fiber and basalt fiber for 1 - 3 min;

[0017] (3) Add water to the mixture and continue stirring for 4 - 6 min to obtain the fiber-reinforced cementitious foam filling material.

[0018] The polypropylene fibers are dispersed in the mixture, increasing the tensile strength and toughness of the material. The chemical bonding between the fibers and the cement matrix further improves the overall performance of the composite material. The polypropylene fibers absorb impact energy, and the basalt fibers increase the tensile strength. The polypropylene fibers disperse the impact energy, and the basalt fibers provide rigid support to enhance the integrity of the matrix.

[0019] The modified aluminum slag foaming agent reacts with water to generate stable bubbles and simultaneously release Ca 2+ Activate SiO2 and Al2O3 in the coal gangue to generate C-S-H gel to fill the pores, making the material have both high compressive strength and low thermal conductivity.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) By resourcefully utilizing industrial waste aluminum slag and coal gangue, the present invention reduces environmental pollution and waste treatment costs, and at the same time reduces the procurement cost of raw materials, achieving a double improvement in environmental protection and economic benefits.

[0022] (2) The present invention eliminates the risk of NH3 release through the modified aluminum slag foaming agent, and at the same time generates active mineral phases, combines SiO2 and Al released by the activated coal gangue 3+ , promotes the hydration reaction to generate C-S-H gel, and improves the compactness and compressive strength of the material.

[0023] (3) The filling material of the present invention utilizes the active mineral phases generated by the eutectic reaction and the hydration reaction, combined with the strengthening effect of polypropylene fibers, and exhibits excellent mechanical properties and durability. The 28-day compressive strength is 8-10 MPa, the bleeding rate is <1%, the strength retention rate after 300 freeze-thaw cycles is ≥90%, and the thermal conductivity is ≤0.25 W / (m·K). It effectively improves the stability and safety of the mined-out area in the mine, reducing the risk of ground settlement and cracks. Description of the Drawings

[0024] Figure 1 It is a scanning electron microscope image of the pore structure of the fiber-reinforced cement-based foam filling material. Detailed Embodiments

[0025] The following further clarifies the present invention in combination with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0026] Embodiment 1

[0027] The fiber-reinforced cement-based foam filling material S1 is composed of the following components by weight fraction:

[0028] Ordinary Portland cement (42.5R): 65%;

[0029] Activated coal gangue (particle size ≤ 150 μm): 5%;

[0030] Modified aluminum slag foaming agent (Al2O3 72%, AlN 8%): 10%;

[0031] Polypropylene fiber (tensile strength 500 MPa, elastic modulus 4.0 GPa, length 12 mm, diameter 25 μm): 1%;

[0032] Basalt fiber (tensile strength 850 MPa, elastic modulus 100 GPa, length 15 mm, diameter 15 μm): 0.5%;

[0033] Water: 18.5%.

[0034] The preparation method of the above-mentioned filling material includes the following steps:

[0035] (1) Aluminum slag (with Al2O3 content of 78% and AlN content of 5%) and quicklime (CaO content of 92%) are mixed at 0.3:1, calcined at 850 °C for 1.5 hours and then at 1150 °C for 1 hour in sequence, and ground to a particle size ≤ 45 μm after cooling;

[0036] (2) After crushing the coal gangue to a particle size of ≤150 μm, it is stirred with a sodium silicate solution with a mass fraction of 8% at 70 °C for 30 minutes to obtain activated coal gangue, and the sodium silicate modulus is 2.8;

[0037] (3) Dry-mix the modified aluminum slag foaming agent, cement, activated coal gangue, polypropylene fiber and basalt fiber for 2 minutes;

[0038] (4) Add water and stir for 5 minutes to obtain the filling material.

[0039] Figure 1 It is the scanning electron micrograph of the pore structure of the fiber-reinforced cement-based foam filling material. As can be seen from Figure 1 It can be seen that the pore structure of the filling material is a uniform closed-pore distribution.

[0040] Example 2

[0041] The fiber-reinforced cement-based foam filling material S2 is composed of the following components by weight fraction:

[0042] Ordinary Portland cement (42.5R): 50%;

[0043] Activated coal gangue (particle size ≤150 μm): 15%;

[0044] Modified aluminum slag foaming agent (Al2O3 72%, AlN 8%): 15%;

[0045] Polypropylene fiber (tensile strength 500 MPa, elastic modulus 5.0 GPa, length 12 mm, diameter 25 μm): 2%;

[0046] Basalt fiber (tensile strength 850 MPa, elastic modulus 90 GPa, length 15 mm, diameter 15 μm): 0.8%;

[0047] Water: 17.2%.

[0048] The preparation method of the above-mentioned filling material is the same as that of Example 1.

[0049] Comparative Example 1

[0050] The fiber-reinforced cement-based foam filling material G1 is composed of the following components by weight fraction:

[0051] Ordinary Portland cement (42.5R): 50%;

[0052] Activated coal gangue (particle size ≤150 μm): 15%;

[0053] Modified aluminum slag foaming agent (Al2O3 72%, AlN 8%): 15%;

[0054] Polypropylene fiber (tensile strength 500 MPa, elastic modulus 5.0 GPa, length 12 mm, diameter 25 μm): 2%;

[0055] Water: 18%.

[0056] The preparation method of the above filling material is the same as that in Example 1.

[0057] The compressive strength of samples S1, S2, and G1 was tested in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", the bleeding rate was tested in accordance with JC / T 1083-2008 "Test Method for Compatibility of Cement and Water Reducing Agent", the strength retention rate after 300 freeze-thaw cycles was tested in accordance with GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete", and the thermal conductivity was tested in accordance with GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Characteristics of Thermal Insulation Materials - Guarded Hot Plate Method". The results are shown in the following table.

[0058] Table 1 Performance test results of samples S1, S2, and G1

[0059]

[0060] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A fiber-reinforced cement-based foam filling material, characterized in that, It consists of the following components by weight fraction: 50%-70% of cement, 5%-25% of activated coal gangue, 10%-20% of modified aluminum slag foaming agent, 1%-2% of polypropylene fiber, 0.5%-1% of basalt fiber, and the balance is water.

2. The fiber-reinforced cement-based foam filling material according to claim 1, characterized in that, The polypropylene fiber has a tensile strength of 450-600 MPa, an elastic modulus of 3.5-5.0 GPa, a fiber length of 6-20 mm, and a diameter of 15-35 μm.

3. The fiber-reinforced cement-based foam filling material according to claim 1, wherein The basalt fiber has a tensile strength ≥800 MPa, an elastic modulus of 80-110 GPa, a fiber length of 12-18 mm, and a diameter of 10-20 μm.

4. The fiber-reinforced cement-based foam filling material according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of 42.5R.

5. The fiber-reinforced cement-based foam filling material according to claim 1, wherein, The modified aluminum slag foaming agent is prepared by mixing aluminum slag and quicklime in a mass ratio of 0.3:1-0.4:1 and then calcining.

6. The fiber-reinforced cement-based foam filling material according to claim 5, wherein, The calcination process is completed in two stages. Specifically: the first stage is to calcine at 800-900 °C for 1-2 hours to make the AlN oxidation rate ≥95%; the second stage is to calcine at 1100-1200 °C for 0.5-1 hour to generate calcium aluminate and silicate minerals.

7. The fiber-reinforced cement-based foam filling material according to claim 1, wherein, The preparation method of the activated coal gangue is: after crushing the coal gangue to a particle size ≤150 μm, stirring it with a sodium silicate solution with a mass fraction of 5%-10% at 60-80 °C for 30 minutes.

8. The fiber-reinforced cement-based foam filling material according to claim 1, wherein The aluminum slag contains Al2O3≥70% and AlN≤10%; the quicklime contains CaO≥90%.

9. The preparation method of the fiber-reinforced cement-based foam filling material according to claim 1, characterized in that, It includes the following steps: (1) Grinding the modified aluminum slag foaming agent to a particle size ≤45 μm by a planetary ball mill; (2) Dry-mixing the ground modified aluminum slag foaming agent with cement, coal gangue, polypropylene fiber and basalt fiber for 1-3 min; (3) Adding water to the mixture and continuing to stir for 4-6 min to obtain the fiber-reinforced cement-based foam filling material.

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