Solid waste-based conductive recycled aggregate high-ductility concrete and preparation method thereof

Abstract

The present invention relates to the technical field of geopolymer building materials, and in particular to a solid waste-based conductive recycled aggregate high-ductility concrete and a preparation method thereof, which belongs to special low-carbon materials. The present invention adopts recycled fine aggregate and adds mixed fibers to prepare high-ductility concrete with excellent conductive properties. The preparation process of the present invention adopts a large amount of industrial waste, which is waste-recycling and environmentally friendly, and has good conductivity and toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of geopolymer building materials, in particular to a solid waste-based conductive recycled aggregate high-ductility concrete and a preparation method thereof, belonging to special low-carbon materials. Background Art

[0002] With the continuous advancement of construction engineering technology, conductive concrete has been applied in engineering fields such as structural damage detection, electromagnetic shielding, and snow and ice removal. Conductive concrete is generally made from cementitious materials and conductive materials. Common conductive materials include carbonaceous materials such as graphite and carbon fiber, and metallic materials such as steel fiber and metal powder. However, conductive materials such as graphite, metal powder, and steel fiber have the problem of difficult uniform dispersion, while carbonaceous materials such as carbon nanotubes and graphene are also subject to high costs.

[0003] As we all know, traditional concrete is a brittle material with a compressive strength much higher than its flexural strength. In recent years, high-ductility concrete, also known as high-ductility cement-based composite materials, has been developed and applied. It overcomes the shortcomings of concrete's poor crack resistance and is often used in engineering fields such as bridge deck paving and structural reinforcement. However, due to its high consumption of cementitious materials, the cost is relatively high.

[0004] Industrial production is accompanied by the generation of large amounts of solid waste, which poses a threat to the environment. Some industrial solid waste has been successfully used in concrete manufacturing with relatively mature technology, such as fly ash, mineral powder, and silica fume.

[0005] Building demolition is often accompanied by the generation of large amounts of construction waste, which occupies a large amount of land. Crushing it to prepare recycled aggregate can also be used in concrete production.

[0006] The recycling of industrial solid waste and construction waste is beneficial to reducing land occupation and storage, reducing damage to the environment, lowering the cost of building materials production, and reducing carbon emissions, with good environmental and economic benefits. However, there is currently a technical gap in how to increase the added value of industrial solid waste and construction waste and prepare functional concrete, especially the preparation of high-ductility concrete with conductive function. Summary of the Invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a solid waste-based conductive recycled aggregate high-ductility concrete, which uses solid waste to prepare cementitious materials, adopts recycled fine aggregate, and adds mixed fibers to prepare high-ductility concrete with excellent conductive properties, thereby realizing the high-value-added reuse of industrial solid waste and recycled aggregate.

[0008] Specifically, the solid waste-based conductive recycled aggregate high-ductility concrete of the present invention is composed of the following raw materials in parts by weight:

[0009] 550-600 parts of active micropowder, 300-350 parts of rice husk ash, 200-250 parts of mineral powder, 200-220 parts of carbide slag, 450-500 parts of recycled fine aggregate, 10-13 parts of polyvinyl alcohol fiber, 4-6 parts of polypropylene fiber, 6-12 parts of carbon fiber, 18-25 parts of water reducer, 4-6 parts of sodium hydroxide, 1.5-2 parts of defoaming agent, and 320-400 parts of water.

[0010] The present invention adopts active micropowder as the main active substance, adds rice husk ash, mineral powder and carbide slag as gelling materials, and supplements a small amount of sodium hydroxide to increase the alkalinity of the gelling material, thereby realizing the large-scale recycling of industrial solid waste.

[0011] Preferably, the active micropowder preparation process is: Bayer process red mud, lithium slag powder, graphite tailings powder, and sodium aluminate are uniformly mixed in a mass ratio of (5-8): (2-3): (8-10): (0.5-0.8), heated and activated in a reducing atmosphere, cooled, and ground to obtain the active micropowder.

[0012] Bayer red mud is industrial waste slag produced by the aluminum smelting industry and is red in color due to its rich iron oxide content. Lithium slag powder is waste slag produced by the lithium extraction industry, and graphite tailings is waste slag produced in the graphite beneficiation process. The present invention, after extensive testing, uses Bayer red mud, lithium slag powder, and graphite tailings powder as main ingredients, adds sodium metaaluminate, heats and activates the mixture in a reducing atmosphere, and then cools and grinds the mixture to obtain active micropowder. The present invention utilizes the high iron content of Bayer red mud and adds graphite tailings powder for heating and activation. Under the reducing atmosphere, residual graphite in the graphite tailings powder can reduce the high-valent iron in the red mud to produce FeO with good conductive properties. Lithium slag powder also contains residual lithium, which enriches the elemental ion content in the active micropowder. Sodium metaaluminate can also supplement sodium ions. Moreover, under the action of high temperature, the activity of the silico-aluminous active components in the Bayer red mud, lithium slag powder, and graphite tailings powder is improved. Combined with the promoting effect of sodium metaaluminate, the hydration activity of the active micropowder is further improved.

[0013] Rice husk ash is a powder produced by high-temperature treatment of rice husks. Its main component is silicon dioxide, which has good hydration activity and can be used as an admixture to partially replace cement. However, in the existing technology, due to the high water demand of rice husk ash, its usage ratio in cementitious materials is about 10%. The present invention has found that the prepared active micropowder has good adaptability with rice husk ash. When combined with calcium carbide slag as an alkaline activator, the usage ratio of rice husk ash in cementitious materials can be greatly increased without affecting the mechanical properties and conductive effects of concrete. Therefore, the present invention adds a large amount of rice husk ash on the basis of active micropowder, and composites mineral powder to balance the active mineral composition in the cementitious material, uses calcium carbide slag as an alkaline activator, and supplements part of sodium hydroxide to increase the alkalinity of the cementitious material and the ion content in the hydration product, thereby improving the conductive properties of the concrete while meeting the mechanical properties.

[0014] Preferably, the SiO2 content in the rice husk ash is ≥75%.

[0015] Preferably, the mineral powder is at least one of S95 and S105 grades.

[0016] Preferably, the recycled fine aggregate has a particle size of 1-4.75 mm and a fineness modulus of 2.2-2.5. More preferably, the recycled fine aggregate is obtained by crushing and screening construction waste.

[0017] Preferably, the polyvinyl alcohol fiber has a diameter of 8-12 μm and a length of 2-5 mm.

[0018] Preferably, the polypropylene fiber has a diameter of 20-30 μm and a length of 10-20 mm.

[0019] Preferably, the carbon fiber has a diameter of 5-10 μm and a length of 3-8 mm.

[0020] The present invention adopts solid waste-based cementitious materials and combines them with recycled fine aggregate to fully realize the recycling of solid waste. However, the surface of recycled fine aggregate is rough, has certain water absorption, and has some microcracks. Its performance is inferior to that of natural fine aggregate. There are technical difficulties in preparing high-ductility concrete. There is little technical research on the preparation of solid waste-based conductive high-ductility concrete with natural fine aggregate in the prior art. According to the characteristics of the cementitious materials and recycled fine aggregate of the present invention, in order to meet the mechanical property requirements of high-ductility concrete, the present invention adopts polyvinyl alcohol fiber, polypropylene fiber and carbon fiber as mixed fibers to prepare high-ductility concrete. Among them, carbon fiber has a certain crack resistance improvement effect, but it cannot meet the high ductility performance index when used alone. Its main function is to form a conductive network in combination with cementitious materials in concrete. In order to cooperate with carbon fiber to improve the toughness of concrete, the research of the present invention shows that adding polyvinyl alcohol fiber and polypropylene fiber can synergistically improve the toughness of concrete with carbon fiber.

[0021] Preferably, the water reducer is a polycarboxylate water reducer.

[0022] Preferably, the defoaming agent is a silicone defoaming agent.

[0023] Preferably, the heating activation temperature during the preparation of the active micropowder is 700-800° C. and the time is 3-4 hours.

[0024] Preferably, the active micropowder is ground to a particle size of ≤45 μm during the preparation process.

[0025] The present invention also relates to a method for preparing the above-mentioned solid waste-based conductive recycled aggregate high-ductility concrete, which specifically comprises the following steps:

[0026] 1) Weigh each raw material by weight,

[0027] 2) Mix the active micro powder, rice husk ash, mineral powder and carbide slag evenly, add polyvinyl alcohol fiber, polypropylene fiber and carbon fiber, mix evenly to obtain dry powder.

[0028] 3) Mix the water reducer, sodium hydroxide, defoamer and water evenly to obtain liquid material.

[0029] 4) Mix the dry powder, recycled fine aggregate and liquid material evenly to obtain slurry.

[0030] 5) Shape and cure the slurry to obtain the product.

[0031] The present invention has the following technical advantages:

[0032] 1. The present invention uses Bayer red mud, lithium slag powder, graphite tailings powder, and sodium metaaluminate to prepare active micropowder with conductive effect and high activity, which forms a conductive network with carbon fiber to improve the conductivity of concrete.

[0033] 2. The present invention uses recycled fine aggregate as fine aggregate, combines it with solid waste-based cementitious materials, and uses polyvinyl alcohol fiber, polypropylene fiber and carbon fiber to improve the toughness of concrete.

[0034] 3. The preparation process of the present invention uses a large amount of industrial waste, which is waste-recycling and environmentally friendly, and has good electrical conductivity and toughness. DETAILED DESCRIPTION

[0035] In order to characterize the technical effect of the present invention, concrete was prepared and its performance was tested. In the resistivity test, a four-electrode method was used with a voltage of 32 V, a specimen size of 150×150×300 mm, and standard curing for 28 days.

[0036] Example 1

[0037] Concrete is composed of the following raw materials in parts by weight:

[0038] 560 parts of active micropowder, 350 parts of rice husk ash, 220 parts of S95 grade mineral powder, 210 parts of calcium carbide slag, 470 parts of recycled fine aggregate, 11 parts of polyvinyl alcohol fiber, 4 parts of polypropylene fiber, 10 parts of carbon fiber, 23 parts of polycarboxylic acid water reducer, 4 parts of sodium hydroxide, 1.5 parts of organosilicon defoamer, 400 parts of water,

[0039] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite tailings powder and sodium aluminate in a mass ratio of 7:3:9:0.7, heating and activating at 780° C. in a reducing atmosphere for 3.5 hours, cooling and grinding to a particle size of ≤45 μm.

[0040] After testing, the 28d compressive strength of the concrete was 46.0MPa, the flexural strength was 10.2MPa, and the resistivity was 5.3Ω·m.

[0041] Example 2

[0042] Concrete is composed of the following raw materials in parts by weight:

[0043] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade mineral powder, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 12 parts of polyvinyl alcohol fiber, 6 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0044] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite tailings powder and sodium metaaluminate in a mass ratio of 8:2:8:0.8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling and grinding to a particle size of ≤45 μm.

[0045] After testing, the 28d compressive strength of the concrete was 47.5MPa, the flexural strength was 10.8MPa, and the resistivity was 4.9Ω·m.

[0046] Comparative Example 1

[0047] Concrete is composed of the following raw materials in parts by weight:

[0048] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade mineral powder, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 12 parts of polyvinyl alcohol fiber, 6 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0049] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite and sodium aluminate in a mass ratio of 15:2:1:0.8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling, and grinding to a particle size of ≤45 μm.

[0050] After testing, the 28d compressive strength of the concrete was 40.4MPa, the flexural strength was 8.7MPa, and the resistivity was 29.8Ω·m.

[0051] Comparative Example 2

[0052] Concrete is composed of the following raw materials in parts by weight:

[0053] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade mineral powder, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 12 parts of polyvinyl alcohol fiber, 6 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0054] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder and graphite tailings powder in a mass ratio of 8:2:8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling, and grinding to a particle size of ≤45 μm.

[0055] After testing, the 28d compressive strength of the concrete was 36.8MPa, the flexural strength was 7.9MPa, and the resistivity was 36.3Ω·m.

[0056] Comparative Example 3

[0057] Concrete is composed of the following raw materials in parts by weight:

[0058] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade mineral powder, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 12 parts of polyvinyl alcohol fiber, 6 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0059] The active micropowder preparation process is as follows: kaolin, slag powder, iron tailings powder, and sodium aluminate are uniformly mixed in a mass ratio of 8:2:8:0.8, heated and activated at 800° C. in a reducing atmosphere for 3.5 hours, cooled, and ground to a particle size of ≤45 μm.

[0060] After testing, the 28d compressive strength of the concrete was 45.4MPa, the flexural strength was 9.8MPa, and the resistivity was 217.3Ω·m.

[0061] Comparative Example 4

[0062] Concrete is composed of the following raw materials in parts by weight:

[0063] 590 parts of active micropowder, 330 parts of fly ash, 200 parts of S95 grade mineral powder, 220 parts of alkali residue, 480 parts of recycled fine aggregate, 12 parts of polyvinyl alcohol fiber, 6 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylic acid water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0064] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite tailings powder and sodium metaaluminate in a mass ratio of 8:2:8:0.8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling and grinding to a particle size of ≤45 μm.

[0065] After testing, the 28d compressive strength of the concrete was 33.6MPa, the flexural strength was 7.3MPa, and the resistivity was 107.2Ω·m.

[0066] Comparative Example 5

[0067] Concrete is composed of the following raw materials in parts by weight:

[0068] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade slag, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 18 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylic acid water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0069] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite tailings powder and sodium metaaluminate in a mass ratio of 8:2:8:0.8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling and grinding to a particle size of ≤45 μm.

[0070] After testing, the 28d compressive strength of the concrete was 44.5MPa, the flexural strength was 6.1MPa, and the resistivity was 24.0Ω·m.

[0071] Comparative Example 6

[0072] Concrete is composed of the following raw materials in parts by weight:

[0073] 590 parts of active micropowder, 330 parts of rice husk ash, 200 parts of S95 grade mineral powder, 220 parts of calcium carbide slag, 480 parts of recycled fine aggregate, 12 parts of polyethylene fiber, 6 parts of basalt fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of organosilicon defoamer, 390 parts of water,

[0074] The active micropowder preparation process comprises the following steps: uniformly mixing Bayer red mud, lithium slag powder, graphite tailings powder and sodium metaaluminate in a mass ratio of 8:2:8:0.8, heating and activating at 800° C. in a reducing atmosphere for 3.5 hours, cooling and grinding to a particle size of ≤45 μm.

[0075] After testing, the 28d compressive strength of the concrete was 39.8MPa, the flexural strength was 7.5MPa, and the resistivity was 33.4Ω·m.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid waste-based conductive recycled aggregate high ductility concrete, characterized in that: It is composed of the following raw materials in parts by weight: 550-600 parts of active micropowder, 300-350 parts of rice husk ash, 200-250 parts of mineral powder, 200-220 parts of carbide slag, 450-500 parts of recycled fine aggregate, 10-13 parts of polyvinyl alcohol fiber, 4-6 parts of polypropylene fiber, 6-12 parts of carbon fiber, 18-25 parts of water reducer, 4-6 parts of sodium hydroxide, 1.5-2 parts of defoamer, 320-400 parts of water, The particle size of the recycled fine aggregate is 1-4.75 mm, and the fineness modulus is 2.2-2.

5. The recycled fine aggregate is obtained by crushing and screening construction waste. The preparation process of the active micropowder is as follows: Bayer red mud, lithium slag powder, graphite tailings powder, and sodium metaaluminate are uniformly mixed in a mass ratio of (5-8):(2-3):(8-10):(0.5-0.8), heated and activated in a reducing atmosphere, cooled, and ground to obtain the active micropowder.

2. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The SiO2 content in the rice husk ash is ≥75%.

3. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The mineral powder is at least one of S95 and S105 grades.

4. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The particle size of the recycled fine aggregate is 1-4.75 mm, and the fineness modulus is 2.2-2.

5.

5. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The polyvinyl alcohol fiber has a diameter of 8-12 μm and a length of 2-5 mm, the polypropylene fiber has a diameter of 20-30 μm and a length of 10-20 mm, and the carbon fiber has a diameter of 5-10 μm and a length of 3-8 mm.

6. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

7. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: The defoaming agent is an organosilicon defoaming agent.

8. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: During the preparation of the active micropowder, the heating activation temperature is 700-800° C. and the time is 3-4 hours.

9. The solid waste-based conductive recycled aggregate high-ductility concrete according to claim 1, characterized in that: During the preparation process of the active micropowder, the powder is ground to a particle size of ≤45 μm.

10. The method for preparing solid waste-based conductive recycled aggregate high-ductility concrete according to any one of claims 1 to 9, characterized in that: The steps include: 1) Weigh each raw material by weight, 2) Mix the active micro powder, rice husk ash, mineral powder and carbide slag evenly, add polyvinyl alcohol fiber, polypropylene fiber and carbon fiber, mix evenly to obtain dry powder. 3) Mix the water reducer, sodium hydroxide, defoamer and water evenly to obtain liquid material. 4) Mix the dry powder, recycled fine aggregate and liquid material evenly to obtain slurry. 5) Shape and cure the slurry to obtain the product.