Solid waste-based high-toughness composite material and preparation method thereof

Abstract

The invention provides a solid waste-based high-toughness composite material. The solid waste-based high-toughness composite material is prepared from the following raw materials in parts by weight: 40-50 parts of a low-carbon solid waste cementing material, 30-40 parts of fine aggregate, 10-20 parts of fly ash, 10-20 parts of toughening fibers, 25-35 parts of water and 0.5-1 part of a water reducing agent. The invention also provides a preparation method of the solid waste-based high-toughness composite material. The solid waste-based high-toughness composite material provided by the invention has relatively good strength, toughness and durability.

Description

Technical Field

[0001] The present invention relates to a composite material, in particular to a solid waste-based high-toughness composite material and a preparation method thereof. Background Art

[0002] Traditional cement-based composite materials are difficult to meet the requirements of high toughness and high durability in modern construction projects due to their large brittleness. On the other hand, the large-scale storage of industrial solid waste not only occupies land resources but also brings environmental pollution. Therefore, the development and research of high-toughness composite materials based on the utilization of solid waste resources can not only improve the performance of building materials but also realize the resource utilization of solid waste, which is in line with the concept of green and low-carbon development. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a solid waste-based high-toughness composite material with good strength, toughness and durability.

[0004] To solve the above technical problem, the technical solution of the present invention is as follows:

[0005] A solid waste-based high-toughness composite material is made from the following raw materials in parts by weight: 40-50 parts of low-carbon solid waste cementitious material, 30-40 parts of fine aggregate, 10-20 parts of fly ash, 10-20 parts of toughening fiber, 25-35 parts of water, and 0.5-1 part of water reducing agent.

[0006] Further, the low-carbon solid waste cementitious material of the present invention is composed of steel slag, slag, desulfurized gypsum, and alkali activator in a weight ratio of (40-50):(30-40):(10-20):(1-3). The low-carbon solid waste cementitious material is compounded by steel slag, slag and desulfurized gypsum. Through the double salt effect and the silicon tetracoordination isomorphization effect, C-S-H gel and ettringite are generated by potential active components (CaO, SiO2, Al2O3) to provide bonding and strength.

[0007] Further, the specific surface area of the steel slag in the present invention is 400-500m 2 / kg, the specific surface area of the slag is 350-450m 2 / kg, the specific surface area of the desulfurized gypsum is 200-300m 2 / kg, and the alkali activator is one or a mixture of two of sodium carbonate and sodium sulfate. Among them, the steel slag provides the main structural calcium source and participates in the double salt effect to generate ettringite and C-S-H gel; the slag provides the silicon-aluminum source and generates C-S-H and C-A-S-H gels with Ca 2+ in the steel slag; the desulfurized gypsum provides sulfate ions to stabilize the hydration products and avoid reaction instability in the alkali activation system; the alkali activator can fully activate the potential activity of the low-carbon solid waste cementitious material and then regulate the reaction environment.

[0008] Furthermore, the fine aggregate in the present invention is fine coal gangue sand or fine iron tailings sand. The fine aggregate provides the skeleton and strength, and optimizes the grading and the compactness of the material.

[0009] Furthermore, the preparation method of the fine coal gangue sand in the present invention is as follows:

[0010] The coal gangue is dried until the moisture content is < 3%, and then coarsely crushed to a particle size ≤ 10 mm using a jaw crusher or a hammer crusher. Then, it is medium-crushed to a particle size ≤ 2 mm using a cone crusher or a counterattack crusher. Then, it is crushed to a particle size ≤ 0.5 mm using an impact sand making machine or a vertical shaft crusher. Finally, it is screened using a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively to obtain fine coal gangue particles with a particle size of 75 μm - 0.5 mm and ultrafine coal gangue particles with a particle size < 75 μm. The fine coal gangue particles and the ultrafine coal gangue particles are collected and mixed to obtain fine coal gangue sand, and the ultrafine coal gangue particles are separated using a cyclone separator or a pneumatic separation device and the content thereof is controlled to be 5 - 15 wt%, which can avoid the influence of excessive content of ultrafine coal gangue particles on grading imbalance and the fluidity of the material.

[0011] Furthermore, the preparation method of the fine iron tailings sand in the present invention is as follows:

[0012] The iron tailings are washed to remove surface impurities and then dried until the moisture content is < 5%. Then, the particles with a particle size ≥ 5 mm are screened out. Then, it is finely crushed to a particle size ≤ 1 mm using an impact sand making machine or a vertical shaft crusher. Then, it is ground to a particle size ≤ 0.5 mm and a specific surface area of 350 - 450 m 2 / kg using a ball mill or a vibration mill. Then, it is screened using a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively to obtain fine iron tailings particles with a particle size of 75 μm - 0.5 mm and ultrafine iron tailings particles with a particle size < 75 μm. The fine iron tailings particles and the ultrafine iron tailings particles are collected and mixed to obtain fine iron tailings sand, and the ultrafine iron tailings particles are separated using a cyclone separator or a pneumatic separation device and the content thereof is controlled to be 5 - 15 wt%, which can avoid the influence of excessive content of ultrafine iron tailings particles on grading imbalance and the fluidity of the material.

[0013] Furthermore, the particle size of the fly ash in the present invention is 0.5 - 75 μm. The fly ash can play a micro-filling role, fill the pores, improve the compactness of the material, and at the same time improve the fluidity of the slurry.

[0014] Furthermore, the toughening fiber in the present invention is one or more of PVA fiber, PE fiber, basalt fiber, and glass fiber with a single filament diameter of 10 - 20 μm, a length of 6 - 12 mm, a tensile strength of 1000 - 3000 MPa, and an elongation rate ≥ 3%. The toughening fiber is used for crack control, toughening, and improvement of strain hardening characteristics.

[0015] Furthermore, the water reducer of the present invention is a polycarboxylic acid water reducer. The water reducer is used to reduce the water-cement ratio, enhance the strength and fluidity of the material, and can disperse cement particles through the steric hindrance effect.

[0016] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned solid waste-based high-toughness composite material.

[0017] To solve the above technical problems, the technical solution is:

[0018] A method for preparing a solid waste-based high-toughness composite material comprises the following steps:

[0019] S1 weighed each raw material by weight, the low-carbon solid waste cementitious material, fine aggregate, fly ash was added to the planetary mixer, stirred at 150-180rpm for 3-5 minutes to obtain a mixture;

[0020] S2. Water and a water reducing agent were added to the mixture obtained in step S1, stirred at a speed of 150-180 rpm for 2-3 minutes, and then stirred at a speed of 240-300 rpm for 3-5 minutes to obtain a mixture II;

[0021] S3. Add the toughening fiber to the mixture 2 obtained in step S2, and stir at a speed of 240-300 rpm for 3-5 minutes to obtain a solid waste-based high-toughness composite material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The present invention replaces traditional cement-based materials with industrial solid wastes such as steel slag, slag, desulfurized gypsum, and fly ash, and forms a cementitious system through active excitation and grading optimization. At the same time, fiber is used as a toughening medium, and the bonding performance of the fiber and matrix interface is optimized through micromechanics theory. When the composite material is tensile, the fiber can effectively bridge microcracks and delay crack expansion. At the same time, the fiber and the matrix work together to form multi-point cracking, and the width of the crack is limited to within 150μm. The stress continues to increase with strain, realizing a ductile failure mode similar to that of metal, and the ultimate tensile strain can reach 3-5%. The bridging effect of the fiber can disperse stress concentration, promote cracks to be distributed in a fine and uniform form, and avoid brittle fracture caused by a single wide crack, thereby significantly improving the crack resistance, toughness and durability of the composite material.

[0024] 2) The present invention can effectively solve the problems of high brittleness and low utilization rate of solid waste resources of traditional cement-based composite materials, and has broad engineering application prospects. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below in conjunction with specific embodiments. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0026] Example 1

[0027] The solid waste-based high-toughness composite material is made of the following raw materials by weight: 45 parts of low-carbon solid waste cementitious material, 35 parts of fine aggregate, 15 parts of fly ash, 15 parts of toughening fiber, 30 parts of water, and 0.8 part of water reducer. Among them, the low-carbon solid waste cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 45:35:15:2. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 200 - 300 m 2 / kg, and the alkali activator is sodium carbonate; the fine aggregate is fine coal gangue sand; the particle size of the fly ash is 0.5 - 75 μm; the toughening fiber is PVA fiber with a single filament diameter of 15 μm, a length of 9 mm, a tensile strength of 2000 MPa, and an elongation rate ≥ 3%; the water reducer is polycarboxylate water reducer.

[0028] The preparation method of the fine coal gangue sand is as follows:

[0029] Dry the coal gangue until the moisture content < 3%, then use a jaw crusher or a hammer crusher for coarse crushing to a particle size ≤ 10 mm, then use a cone crusher or a counterattack crusher for medium crushing to a particle size ≤ 2 mm, then use an impact sand making machine or a vertical shaft crusher to crush to a particle size ≤ 0.5 mm, and finally use a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively for screening to obtain coal gangue fine particles with a particle size of 75 μm - 0.5 mm and coal gangue ultrafine particles with a particle size < 75 μm. Collect and mix the coal gangue fine particles and the coal gangue ultrafine particles to obtain fine coal gangue sand, and use a cyclone separator or a pneumatic separation device to separate the coal gangue ultrafine particles and control their content to be 5 wt%.

[0030] The preparation method of Example 1 includes the following steps:

[0031] S1. Weigh each raw material by weight, add the low-carbon solid waste cementitious material, fine aggregate, and fly ash into a planetary mixer, and stir at a speed of 160 rpm for 4.5 minutes to obtain mixture one;

[0032] S2. Add water and water reducer to mixture one obtained in step S1, stir at a speed of 160 rpm for 2.5 minutes, and then stir at a speed of 270 rpm for 4 minutes to obtain mixture two;

[0033] S3. Add the toughening fiber to the mixture two obtained in step S2, and stir at a speed of 270 rpm for 4 minutes to obtain the solid waste-based high-toughness composite material.

[0034] Example 2

[0035] The solid waste-based high-toughness composite material is made from the following raw materials by weight: 40 parts of low-carbon solid waste cementitious material, 30 parts of fine aggregate, 10 parts of fly ash, 20 parts of toughening fiber, 27 parts of water, and 0.9 part of water reducing agent. Among them, the low-carbon solid waste cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 40:30:10:1. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 200 - 300 m 2 / kg, and the alkali activator is sodium sulfate; the fine aggregate is fine iron tailings sand; the particle size of the fly ash is 0.5 - 75 μm; the toughening fiber is basalt fiber with a single filament diameter of 10 μm, a length of 6 mm, a tensile strength of 1000 MPa, and an elongation rate ≥ 3%; the water reducing agent is polycarboxylate water reducing agent.

[0036] The preparation method of the fine iron tailings sand is as follows:

[0037] After washing the iron tailings to remove surface impurities, dry them until the moisture content < 5%, then screen out the particles with a particle size ≥ 5 mm, and then use an impact crusher or a vertical shaft crusher for fine crushing until the particle size ≤ 1 mm. Then use a ball mill or a vibration mill to grind until the particle size ≤ 0.5 mm and the specific surface area is 350 - 450 m 2 / kg. Then, use a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively for screening to obtain fine iron tailings particles with a particle size of 75 μm - 0.5 mm and ultrafine iron tailings particles with a particle size < 75 μm. Collect and mix the fine iron tailings particles and the ultrafine iron tailings particles to obtain fine iron tailings sand, and use a cyclone separator or a pneumatic separation device to separate the ultrafine iron tailings particles and control their content to 5 wt%.

[0038] The preparation method of Example 2 includes the following steps:

[0039] S1. Weigh each raw material by weight, add the low-carbon solid waste cementitious material, fine aggregate, and fly ash to a planetary mixer, and stir at a speed of 150 rpm for 5 minutes to obtain mixture one;

[0040] S2. Add water and water reducing agent to the mixture one obtained in step S1, stir at a speed of 150 rpm for 3 minutes, and then stir at a speed of 240 rpm for 5 minutes to obtain mixture two;

[0041] S3. Add the toughening fiber into the mixture two obtained in step S2, and stir at a speed of 240 rpm for 5 minutes to obtain the solid waste-based high-toughness composite material.

[0042] Example 3

[0043] The solid waste-based high-toughness composite material is made from the following raw materials by weight: 42 parts of low-carbon solid waste cementitious material, 40 parts of fine aggregate, 20 parts of fly ash, 16 parts of toughening fiber, 35 parts of water, and 0.5 part of water reducing agent. Among them, the low-carbon solid waste cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 50:40:20:3. The specific surface area of the steel slag is 400 - 500 m2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 200 - 300 m 2 / kg, and the alkali activator is sodium carbonate; the fine aggregate is fine coal gangue sand; the particle size of the fly ash is 0.5 - 75 μm; the toughening fiber is a PE fiber with a single filament diameter of 18 μm, a length of 10 mm, a tensile strength of 2500 MPa, and an elongation rate ≥ 3%; the water reducing agent is a polycarboxylate water reducing agent.

[0044] The preparation method of the fine coal gangue sand is as follows:

[0045] Dry the coal gangue until the moisture content < 3%, then use a jaw crusher or a hammer crusher for coarse crushing until the particle size ≤ 10 mm, then use a cone crusher or a counterattack crusher for medium crushing until the particle size ≤ 2 mm, then use an impact sand making machine or a vertical shaft crusher to crush until the particle size ≤ 0.5 mm, and finally use a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively for screening to obtain coal gangue fine particles with a particle size of 75 μm - 0.5 mm and coal gangue ultrafine particles with a particle size < 75 μm. Collect and mix the coal gangue fine particles and the coal gangue ultrafine particles to obtain the fine coal gangue sand, and use a cyclone separator or a pneumatic separation device to separate the coal gangue ultrafine particles and control their content to be 15 wt%.

[0046] The preparation method of Example 3 includes the following steps:

[0047] S1. Weigh each raw material by weight, add the low-carbon solid waste cementitious material, fine aggregate, and fly ash into a planetary mixer, and stir at a speed of 180 rpm for 3 minutes to obtain mixture one;

[0048] S2. Add water and water reducing agent into the mixture one obtained in step S1, stir at a speed of 180 rpm for 2 minutes, and then stir at a speed of 300 rpm for 3 minutes to obtain mixture two;

[0049] S3. Add the toughening fiber into the mixture two obtained in step S2, and stir at a speed of 300 rpm for 3 minutes to obtain the solid waste-based high-toughness composite material.

[0050] Example 4

[0051] The solid waste-based high-toughness composite material is made from the following raw materials in parts by weight: 44 parts of low-carbon solid waste cementitious material, 32 parts of fine aggregate, 12 parts of fly ash, 10 parts of toughening fiber, 25 parts of water, and 1 part of water reducing agent. Among them, the low-carbon solid waste cementitious material is composed of steel slag, slag, desulfurized gypsum, and alkali activator with a weight ratio of 48:33:12:2. The specific surface area of the steel slag is 400 - 500 m 2 / kg, the specific surface area of the slag is 350 - 450 m 2 / kg, the specific surface area of the desulfurized gypsum is 200 - 300 m 2 / kg, and the alkali activator is sodium sulfate; the fine aggregate is fine iron tailings sand; the particle size of the fly ash is 0.5 - 75 μm; the toughening fiber is glass fiber with a single filament diameter of 20 μm, a length of 12 mm, a tensile strength of 3000 MPa, and an elongation rate ≥ 3%; the water reducing agent is polycarboxylate water reducing agent.

[0052] The preparation method of the fine iron tailings sand is as follows:

[0053] After washing the iron tailings to remove surface impurities, dry them until the moisture content < 5%. Then screen out the particles with a particle size ≥ 5 mm, and then use an impact crusher or a vertical shaft crusher for fine crushing until the particle size ≤ 1 mm. Then use a ball mill or a vibration mill to grind until the particle size ≤ 0.5 mm and the specific surface area is 350 - 450 m 2 / kg. Then, use a double-layer screen vibrating screen with screen hole diameters of 2 mm and 0.5 mm respectively for screening to obtain fine iron tailings particles with a particle size of 75 μm - 0.5 mm and ultrafine iron tailings particles with a particle size < 75 μm. Collect and mix the fine iron tailings particles and the ultrafine iron tailings particles to obtain fine iron tailings sand, and use a cyclone separator or a pneumatic separation device to separate the ultrafine iron tailings particles and control their content to be 15 wt%.

[0054] The preparation method of Example 4 includes the following steps:

[0055] S1. Weigh each raw material according to the parts by weight. Add the low-carbon solid waste cementitious material, fine aggregate, and fly ash into a planetary mixer, and stir at a speed of 150 rpm for 4 minutes to obtain mixture one;

[0056] S2. Add water and water reducing agent to mixture one obtained in step S1, stir at a speed of 150 rpm for 2 minutes, and then stir at a speed of 240 rpm for 4 minutes to obtain mixture two;

[0057] S3. Add the toughening fiber to mixture two obtained in step S2, and stir at a speed of 240 rpm for 4 minutes to obtain the solid waste-based high-toughness composite material.

[0058] Experimental Example: Performance Test

[0059] The solid waste-based high-toughness composites prepared in Examples 1-4 were respectively poured into molds, vibrated and compacted, demolded after standing for 24 h, transferred to a standard curing room for wet curing for 28 days, with a humidity ≥ 90% and a temperature of room temperature, and then performance tests were carried out:

[0060] According to the scheme of GB / T 17671—2021 "Test Method for Strength of Cement Mortar (ISO Method)", a compressive strength test experiment was carried out. The test specimens were cubes with dimensions of 70.5 mm × 70.5 mm × 70.5 mm;

[0061] A CMT5504 type microcomputer-controlled electronic universal testing machine was selected to carry out a uniaxial direct tension experiment. The loading speed was 0.15 mm / min. The test specimens were dumbbell-shaped specimens with a gauge length of 80 mm, a width of 30 mm, and a thickness of 10 mm.

[0062] The test results are shown in Table 1:

[0063] Compressive strength (MPa) Tensile strength (MPa) Tensile strain (%) Example 1 31.5 3.2 2.1 Example 2 33.8 3.5 2.5 Example 3 30.8 3.1 2.3 Example 4 30.4 3.0 2.0

[0064] Table 1

[0065] As can be seen from Table 1, the compressive strength, tensile strength, and tensile strain of Examples 1-4 of the present invention are all good, indicating that the solid waste-based high-toughness composites prepared by the present invention have good strength, toughness, and durability, and have broad engineering application prospects.

[0066] The above embodiments merely illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A solid waste-based high-toughness composite material, characterized in that: The invention is prepared from the following raw materials in parts by weight: 40-50 parts of low-carbon solid waste cementitious material, 30-40 parts of fine aggregate, 10-20 parts of fly ash, 10-20 parts of toughening fiber, 25-35 parts of water and 0.5-1 part of water reducing agent.

2. The solid waste-based high-toughness composite material according to claim 1, characterized in that: The low-carbon solid waste cementitious material is composed of steel slag, slag, desulfurized gypsum and alkali activator in a weight ratio of (40-50):(30-40):(10-20):(1-3).

3. The solid waste-based high-toughness composite material according to claim 2, characterized in that: The specific surface area of ​​the steel slag is 400-500m 2 / kg, the specific surface area of ​​slag is 350-450m 2 / kg, the specific surface area of ​​desulfurized gypsum is 200-300m 2 / kg, the alkali activator is sodium carbonate, sodium sulfate or a mixture of the two.

4. The solid waste-based high-toughness composite material according to claim 1, characterized in that: The fine aggregate is fine sand of coal gangue or fine sand of iron ore tailings.

5. The solid waste-based high-toughness composite material according to claim 4, characterized in that: The preparation method of the coal gangue fine sand is: The gangue is dried to a moisture content of <3%, and then coarsely crushed to a particle size of ≤10mm using a jaw crusher or a hammer crusher, and then medium crushed to a particle size of ≤2mm using a cone crusher or an impact crusher, and then crushed to a particle size of ≤0.5mm using an impact sand making machine or a vertical shaft crusher, and finally sieved using a double-layer mesh vibrating screen with sieve apertures of 2mm and 0.5mm to obtain fine gangue particles with a particle size of 75μm-0.5mm and ultrafine gangue particles with a particle size of <75μm, the fine gangue particles and the ultrafine gangue particles are collected and mixed to obtain fine gangue sand, and the ultrafine gangue particles are separated using a cyclone separator or an air separation device and the content thereof is controlled to be 5-15wt%.

6. The solid waste-based high-toughness composite material according to claim 4, characterized in that: The preparation method of the iron tailings fine sand is: The iron tailings are washed to remove surface impurities and dried to a moisture content of <5%. Then, the particles with a particle size of ≥5mm are screened and crushed to a particle size of ≤1mm using an impact sand making machine or a vertical shaft crusher. Then, the particles are ground to a particle size of ≤0.5mm using a ball mill or a vibration mill, with a specific surface area of ​​350-450m 2 / kg, and then a double-layer mesh vibrating screen with mesh sizes of 2mm and 0.5mm is used for screening to obtain fine iron tailings particles with a particle size of 75μm-0.5mm and ultrafine iron tailings particles with a particle size of <75μm, the fine iron tailings particles and the ultrafine iron tailings particles are collected and mixed to obtain fine iron tailings sand, and a cyclone separator or air separation equipment is used to separate the ultrafine iron tailings particles and control their content to 5-15wt%.

7. The solid waste-based high-toughness composite material according to claim 1, characterized in that: The particle size of the fly ash is 0.5-75 μm.

8. The solid waste-based high-toughness composite material according to claim 1, characterized in that: The toughening fiber is one or more of PVA fiber, PE fiber, basalt fiber and glass fiber with a single filament diameter of 10-20 μm, a length of 6-12 mm, a tensile strength of 1000-3000 MPa and an elongation of ≥3%.

9. The solid waste-based high-toughness composite material according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

10. The method for preparing a solid waste-based high-toughness composite material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1 weighed each raw material by weight, the low-carbon solid waste cementitious material, fine aggregate, fly ash was added to the planetary mixer, stirred at 150-180rpm for 3-5 minutes to obtain a mixture; S2. Water and a water reducing agent were added to the mixture obtained in step S1, stirred at a speed of 150-180rpm for 2-3 minutes, and then stirred at a speed of 240-300rpm for 3-5 minutes to obtain a mixture II; S3. Add the toughening fiber to the mixture 2 obtained in step S2, and stir at a speed of 240-300 rpm for 3-5 minutes to obtain a solid waste-based high-toughness composite material.