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

Abstract

The invention relates to the technical field of geopolymer building materials, in particular to solid-waste-based conductive recycled aggregate high-ductility concrete and a preparation method thereof, and belongs to special low-carbon materials. Recycled fine aggregate is adopted, hybrid fibers are added, and the high-ductility concrete with excellent conductivity is prepared; a large amount of industrial waste is adopted in the preparation process, waste utilization and environmental protection are achieved, and good conductivity and toughness are achieved.

Description

Technical Field

[0001] 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, belonging to special low-carbon materials. Background Art

[0002] With the continuous progress of construction engineering technology, conductive concrete has been applied to engineering fields such as structural damage detection, electromagnetic shielding, snow melting and deicing. Conductive concrete is generally prepared by using cementitious materials and conductive materials. Commonly used conductive materials include carbonaceous raw materials such as graphite and carbon fiber, and metal raw materials such as steel fiber and metal powder. However, conductive materials such as graphite, metal powder, and steel fiber have problems of difficult uniform dispersion, and carbonaceous materials such as carbon nanotubes and graphene have problems of high cost, etc.

[0003] As is well known, traditional concrete is a brittle material, and its compressive strength is 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 disadvantage of poor crack resistance of concrete and is commonly used in engineering fields such as bridge deck paving and structural reinforcement. However, due to its high cementitious material consumption, the cost is relatively high.

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

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

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

[0007] 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 hybrid fibers to prepare high-ductility concrete with excellent conductive performance, realizing the high-added-value 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: 550 - 600 parts of reactive micro - powder, 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 - reducing agent, 4 - 6 parts of sodium hydroxide, 1.5 - 2 parts of defoaming agent, 320 - 400 parts of water.

[0009] The present invention uses reactive micro - powder as the main active substance, adds rice husk ash, mineral powder, and carbide slag as cementitious materials, and supplements a little sodium hydroxide to increase the alkalinity of the cementitious materials, realizing the large - scale recycling of industrial solid wastes.

[0010] Preferably, the preparation process of the reactive micro - powder is as follows: mix bauxite red mud, lithium slag powder, graphite tailing powder, and sodium meta - aluminate in a mass ratio of (5 - 8):(2 - 3):(8 - 10):(0.5 - 0.8) evenly, heat and activate in a reducing atmosphere, cool, and grind to obtain.

[0011] Bauxite red mud is an industrial waste residue produced in the aluminum smelting industry, showing a red color due to its rich iron oxides. Lithium slag powder is a waste residue produced in the lithium extraction industry, and graphite tailings are waste residues produced in the graphite beneficiation process. Through a large number of experiments in the present invention, bauxite red mud, lithium slag powder, and graphite tailing powder are used as main materials, and sodium meta - aluminate is added to heat and activate in a reducing atmosphere, then cooled and ground to obtain reactive micro - powder. The present invention utilizes the high iron - containing characteristic of bauxite red mud, adds graphite tailing powder for heating and activation. In a reducing atmosphere, the residual graphite in the graphite tailing powder can reduce the high - valence iron in the red mud, producing FeO with good electrical conductivity. The lithium slag powder also contains residual lithium elements, enriching the elemental ion content in the reactive micro - powder. Sodium meta - aluminate can also supplement sodium ions. Moreover, under the action of high temperature, the activity of the silicon - aluminum active components in bauxite red mud, lithium slag powder, and graphite tailing powder is improved. Combined with the promoting effect of sodium meta - aluminate, the hydration activity of the reactive micro - powder is further enhanced.

[0012] Rice husk ash is a powder produced by high - temperature treatment of rice husks, with the main component being silicon dioxide, having good hydration activity and can be used as a admixture to partially replace cement. However, in the prior art, due to the high water demand of rice husk ash, its usage ratio in cementitious materials is about 10%. The present invention finds that the prepared reactive micro - powder has good compatibility with rice husk ash. Combined with carbide slag as an alkaline activator, the usage ratio of rice husk ash in cementitious materials can be greatly increased, and it will not affect the mechanical properties and electrical conductivity of concrete. Therefore, the present invention adds a large amount of rice husk ash on the basis of reactive micro - powder, and compositely uses mineral powder to balance the active mineral composition in the cementitious materials, uses carbide slag as an alkaline activator, and supplements part of sodium hydroxide to increase the alkalinity of the cementitious materials and the ion content in the hydration products, so as to improve the electrical conductivity of concrete while meeting the mechanical properties.

[0013] Preferably, the SiO in the rice husk ash 2 Content ≥75%.

[0014] Preferably, the mineral powder is at least one of grades S95 and S105.

[0015] Preferably, the particle size of the recycled fine aggregate is 1-4.75 mm, and the fineness modulus is 2.2-2.5. More preferably, the recycled fine aggregate is obtained by crushing and screening construction waste.

[0016] Preferably, the polyvinyl alcohol fiber has a diameter of 8-12 μm and a length of 2-5 mm.

[0017] Preferably, the polypropylene fiber has a diameter of 20-30 μm and a length of 10-20 mm.

[0018] Preferably, the carbon fiber has a diameter of 5-10 μm and a length of 3-8 mm.

[0019] 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 not as good as 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 which 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 present invention's research shows that adding polyvinyl alcohol fiber and polypropylene fiber can synergistically improve the toughness of concrete with carbon fiber.

[0020] Preferably, the water reducer is a polycarboxylate water reducer.

[0021] Preferably, the defoamer is a silicone defoamer.

[0022] Preferably, the heating activation temperature during the preparation of the active micropowder is 700-800°C and the time is 3-4h.

[0023] Preferably, the active micropowder is ground to a particle size of ≤45 μm during the preparation process.

[0024] 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: 1) Weigh each raw material by weight, 2) Mix the reactive micro powder, rice husk ash, mineral powder, and carbide slag evenly, add polyvinyl alcohol fiber, polypropylene fiber, and carbon fiber, and mix evenly to obtain dry powder material. 3) Mix the water reducing agent, sodium hydroxide, defoamer, and water evenly to obtain liquid material. 4) Mix the dry powder material, recycled fine aggregate, and liquid material evenly to obtain slurry. 5) Shape and cure the slurry to obtain the product.

[0025] The present invention has the following technical advantages: 1. The present invention uses Bayer red mud, lithium slag powder, graphite tailing powder, and sodium meta aluminate to prepare reactive micro powder with conductive effect and high activity, which forms a conductive network in combination with carbon fiber to improve the conductivity of concrete. 2. The present invention uses recycled fine aggregate as fine aggregate, combines solid waste based cementitious material, and uses polyvinyl alcohol fiber, polypropylene fiber, and carbon fiber to improve the toughness of concrete. 3. The preparation process of the present invention uses a large amount of industrial waste, which is environmentally friendly for waste utilization and has good conductivity and toughness. Specific embodiments

[0026] To characterize the technical effects of the present invention, concrete was prepared and its performance was tested. During the resistivity test, the four electrode method was used, the voltage was 32V, the size of the test piece was 150×150×300mm, and it was cured under standard conditions for 28d.

[0027] Example 1 Concrete is composed of the following raw materials in parts by weight: 560 parts of reactive micro powder, 350 parts of rice husk ash, 220 parts of S95 grade mineral powder, 210 parts of 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 polycarboxylate water reducing agent, 4 parts of sodium hydroxide, 1.5 parts of silicone defoamer, and 400 parts of water. The preparation process of the reactive micro powder is as follows: Mix Bayer red mud, lithium slag powder, graphite tailing powder, and sodium meta aluminate evenly according to the mass ratio of 7:3:9:0.7, heat and activate in a reducing atmosphere at 780°C for 3.5h, cool, and grind to a particle size of ≤45μm to obtain the product.

[0028] After testing, the 28d compressive strength of the concrete is 46.0MPa, the flexural strength is 10.2MPa, and the resistivity is 5.3Ω·m.

[0029] Example 2 Concrete is composed of the following raw materials in parts by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of 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 superplasticizer, 5 parts of sodium hydroxide, 2 parts of silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: mix bauxite residue, lithium slag powder, graphite tailings powder, and sodium metaaluminate evenly according to a mass ratio of 8:2:8:0.8, heat and activate at 800°C for 3.5 h in a reducing atmosphere, cool, and grind to a particle size of ≤45 μm to obtain it.

[0030] After testing, the 28-day compressive strength of the concrete is 47.5 MPa, the flexural strength is 10.8 MPa, and the resistivity is 4.9 Ω·m.

[0031] Comparative Example 1 The concrete is composed of the following raw materials in parts by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of 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 superplasticizer, 5 parts of sodium hydroxide, 2 parts of silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: mix bauxite residue, lithium slag powder, graphite, and sodium metaaluminate evenly according to a mass ratio of 15:2:1:0.8, heat and activate at 800°C for 3.5 h in a reducing atmosphere, cool, and grind to a particle size of ≤45 μm to obtain it.

[0032] After testing, the 28-day compressive strength of the concrete is 40.4 MPa, the flexural strength is 8.7 MPa, and the resistivity is 29.8 Ω·m.

[0033] Comparative Example 2 The concrete is composed of the following raw materials in parts by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of 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 superplasticizer, 5 parts of sodium hydroxide, 2 parts of silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: mix bauxite residue, lithium slag powder, and graphite tailings powder evenly according to a mass ratio of 8:2:8, heat and activate at 800°C for 3.5 h in a reducing atmosphere, cool, and grind to a particle size of ≤45 μm to obtain it.

[0034] After testing, the 28-day compressive strength of the concrete is 36.8 MPa, the flexural strength is 7.9 MPa, and the resistivity is 36.3 Ω·m.

[0035] Comparative Example 3 Concrete, consisting of the following raw materials by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of 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 silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: kaolin, slag powder, iron tailings powder, and sodium metaaluminate are mixed evenly according to a mass ratio of 8:2:8:0.8, heated and activated at 800 °C in a reducing atmosphere for 3.5 h, cooled, and ground to a particle size of ≤45 μm to obtain it.

[0036] After testing, the 28-day compressive strength of the concrete is 45.4 MPa, the flexural strength is 9.8 MPa, and the resistivity is 217.3 Ω·m.

[0037] Comparative Example 4 Concrete, consisting of the following raw materials by weight: 590 parts of reactive micro powder, 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 polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: bauxite red mud, lithium slag powder, graphite tailings powder, and sodium metaaluminate are mixed evenly according to a mass ratio of 8:2:8:0.8, heated and activated at 800 °C in a reducing atmosphere for 3.5 h, cooled, and ground to a particle size of ≤45 μm to obtain it.

[0038] After testing, the 28-day compressive strength of the concrete is 33.6 MPa, the flexural strength is 7.3 MPa, and the resistivity is 107.2 Ω·m.

[0039] Comparative Example 5 Concrete, consisting of the following raw materials by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of carbide slag, 480 parts of recycled fine aggregate, 18 parts of polypropylene fiber, 11 parts of carbon fiber, 22 parts of polycarboxylate water reducer, 5 parts of sodium hydroxide, 2 parts of silicone defoamer, 390 parts of water, The preparation process of the reactive micro powder is as follows: bauxite red mud, lithium slag powder, graphite tailings powder, and sodium metaaluminate are mixed evenly according to a mass ratio of 8:2:8:0.8, heated and activated at 800 °C in a reducing atmosphere for 3.5 h, cooled, and ground to a particle size of ≤45 μm to obtain it.

[0040] After testing, the 28-day compressive strength of the concrete is 44.5 MPa, the flexural strength is 6.1 MPa, and the resistivity is 24.0 Ω·m.

[0041] Comparative Example 6 Concrete, which is composed of the following raw materials by weight: 590 parts of reactive micro powder, 330 parts of rice husk ash, 200 parts of S95-grade mineral powder, 220 parts of 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 silicone defoamer, 390 parts of water The preparation process of the reactive micro powder is as follows: Mix bauxite red mud, lithium slag powder, graphite tailings powder, and sodium aluminate evenly according to a mass ratio of 8:2:8:0.8, heat and activate at 800°C in a reducing atmosphere for 3.5 h, cool, and grind to a particle size ≤ 45 μm to obtain it.

[0042] After testing, the 28-day compressive strength of the concrete is 39.8 MPa, the flexural strength is 7.5 MPa, and the resistivity is 33.4 Ω·m.

[0043] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate 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: Active micro powder 550-600 parts, rice husk ash 300-350 parts, mineral powder 200-250 parts, carbide slag 200-220 parts, recycled fine aggregate 450-500 parts, polyvinyl alcohol fiber 10-13 parts, polypropylene fiber 4-6 parts, carbon fiber 6-12 parts, water reducer 18-25 parts, sodium hydroxide 4-6 parts, defoamer 1.5-2 parts, water 320-400 parts, The active micro powder preparation process comprises: uniformly mixing Bayer red mud, lithium slag powder, graphite tailing powder and sodium aluminate in a mass ratio of (5-8):(2-3):(8-10):(0.5-0.8), heating and activating in a reducing atmosphere, cooling and grinding to obtain the active micro powder.

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 grade S95 and S105.

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 defoamer is an organosilicon defoamer.

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

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

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.