Concrete aggregate based on modified coal gangue as well as preparation method and application of concrete aggregate

Abstract

The concrete aggregate based on the modified coal gangue is prepared from the following components in parts by weight: 35 to 40 parts of slag, 5 to 9 parts of nano aluminum oxide, 80 to 100 parts of red mud, 10 to 20 parts of fly ash, 80 to 100 parts of the modified coal gangue and 10 to 15 parts of hybrid fiber. The concrete aggregate based on the modified coal gangue has better strength, so that the mechanical property of concrete is improved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a concrete aggregate based on modified coal gangue, and a preparation method and application thereof. Background Art

[0002] Concrete, referred to as "concrete", is a general term for engineering composite materials in which aggregates are bonded into a whole by cementitious materials. The term concrete usually refers to cement as a cementitious material, sand and stone as aggregates; mixed with water (which may contain admixtures and additives) in a certain proportion, and the cement concrete obtained by mixing is also called ordinary concrete, which is widely used in civil engineering. Among them, concrete aggregate plays a role of skeleton and support in buildings. When mixing the materials, cement is stirred into a thin paste with water. If aggregates are not added, it cannot be formed, which will make the subsequent concrete unusable. Therefore, aggregates are very important raw materials in construction, and the various performance indicators of aggregates will directly affect the construction performance and use performance of concrete.

[0003] Coal gangue refers to coal-containing waste or by-products produced during coal mining and processing. It is mainly composed of non-economic parts of coal strata, including coal strata, carbonaceous roof, rock debris, mudstone and quartz. In the process of coal mining, a large amount of coal gangue will inevitably be produced, which has become the solid waste with the largest cumulative stock and the largest occupied area. In addition, the accumulation and discharge of coal gangue has caused serious pollution and damage to the ecological environment of the mining area.

[0004] As people pursue environmental protection in buildings, some scholars have begun to study the use of coal gangue as coarse aggregate to prepare coal gangue concrete in recent years, in order to achieve the purpose of utilizing solid waste and reducing the cost of concrete production. However, as a weak aggregate, coal gangue will generally greatly weaken the strength of coal gangue concrete when added to concrete. Therefore, how to use coal gangue as a weak aggregate and add it to concrete without reducing the mechanical properties of concrete has become a problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In order to solve the above problems, the embodiments of the present application provide a concrete aggregate based on modified coal gangue, a preparation method and application thereof, which can improve the strength of the concrete aggregate based on modified coal gangue, thereby improving the mechanical properties of concrete.

[0006] To this end, the following technical solutions are adopted in the embodiments of the present application:

[0007] In a first aspect, the embodiment of the present application provides a concrete aggregate based on modified coal gangue, comprising the following components in parts by weight: 35-40 parts of slag, 5-9 parts of nano-alumina, 80-100 parts of red mud, 10-20 parts of fly ash, 80-100 parts of modified coal gangue, and 10-15 parts of mixed fibers;

[0008] Among them, the preparation method of the modified coal gangue includes the following steps:

[0009] The coal gangue is ground into powder by ball milling and then screened with a 150-mesh standard sieve to obtain fine coal gangue powder;

[0010] The coal gangue powder is soaked in a sulfuric acid solution with a concentration of 40-50%, the slag and liquid are separated, the soaked coal gangue slag is dried, and then soaked in an ammonia water solution with a concentration of 25-30%, the slag and liquid are separated, and dried to obtain the primary treated coal gangue;

[0011] A titanate coupling agent solution with a concentration of 10-12% is prepared by using ethanol, the primary treated coal gangue is impregnated therein, the impregnation time is controlled to be 45-60 min, the coal gangue is taken out, rinsed 2-3 times with distilled water, and dried to obtain the secondary treated coal gangue;

[0012] Polyvinyl alcohol is dissolved in deionized water to form a 10% polyvinyl alcohol solution. The secondary treated coal gangue is mixed with the polyvinyl alcohol solution, methyl acrylate and an initiator are added, stirred evenly, heated to 80°C, reacted for 1-2 h, cooled, the slag and liquid are separated, and dried to obtain the modified coal gangue; the weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and the initiator in the modified coal gangue is (1-10):(0.5-3):(0.2-1):(0.005-0.05).

[0013] In this embodiment, through multi-step modification treatment, the structural stability and strength performance of coal gangue are improved by using chemical and physical means respectively. Specifically, the treatment process of coal gangue includes means such as pickling, titanate coupling agent impregnation, and polyvinyl alcohol composite treatment, which improve the surface characteristics and internal structure of coal gangue, enhance its adhesion to concrete, and thus reduce the situation of strength decline after coal gangue is incorporated into concrete.

[0014] Specifically, first, the coal gangue is ball-milled into powder, and then the fine coal gangue powder is screened out through a 150-mesh standard sieve. This helps to increase the surface contact area between the coal gangue and other components (such as cement), providing a better basis for subsequent modification. Sulfuric acid treatment and ammonia water soaking: The coal gangue powder is treated with sulfuric acid and ammonia water to remove some harmful impurities (such as metal ions), cleaning the surface of the coal gangue, which is beneficial for adding modifiers next. The titanate coupling agent can enhance the chemical bonding force between the coal gangue and the cement matrix at a certain concentration, helping to improve the hydrophilicity of the coal gangue and the adhesion with the cement paste in the concrete. Composite treatment of polyvinyl alcohol and methyl acrylate: This step can further enhance the surface activity of the coal gangue and strengthen the structural stability of the coal gangue through polymerization reaction, enabling it to better maintain its shape in the concrete and improve its strength. The modified coal gangue has improved its adhesion with the cement matrix through physical and chemical treatment, enhancing its mechanical properties. Its main role is to act as an aggregate in the concrete, providing certain structural support and participating in the cement hydration reaction to further improve the strength and durability of the concrete. The bonding force between the modified coal gangue and the cement matrix has been enhanced, enabling it to act together with other components (such as slag, fly ash) to improve the strength, toughness and stability of the concrete. The addition of the modified coal gangue can also reduce the cost of the concrete and promote the resource utilization of the coal gangue.

[0015] Secondly, the addition of fly ash and nano-alumina fills the gaps in the coal gangue, improving the density of the coal gangue. At the same time, the modified coal gangue particles fill the voids in the subsequent concrete, making the internal structure of the concrete more dense. In addition, in the subsequent application of the concrete, nano-alumina can also play a role in lubrication and filling, reducing the cohesiveness of the paste and increasing its fluidity, which enables the concrete aggregate prepared from the modified coal gangue to be more evenly distributed during the mixing and shaping process of the concrete paste. Moreover, nano-alumina can react with the cement hydration products to generate Al(OH)3 and other hydrated aluminates, which helps to further promote the hydration reaction of the cement paste and improve the compressive strength, flexural strength and thermal resistance of the concrete. In addition, the particles of nano-alumina are relatively small, which can fill the pores in the concrete, improving its density. When acting together with other admixtures such as slag, fly ash, red mud, etc., nano-alumina can enhance the microstructure of the concrete and improve the overall strength and stability by filling voids and promoting chemical reactions.

[0016] In addition, as a mineral admixture for modified coal gangue, slag can fill the pore structure and capillary pores in the modified coal gangue fragments, block the permeation channels of the modified coal gangue, thereby greatly improving the strength and impermeability of the modified coal gangue. Slag is an active mineral admixture that reacts with water in cement to form hydration products, which can improve the compressive strength and impermeability of concrete. At the same time, slag has good corrosion resistance, which can enhance the durability of concrete. The addition of slag can react with the cement minerals in cement to form hydration products with a stable structure, thereby improving the early strength and long-term strength of concrete. It acts together with other components (such as red mud and fly ash) to form a denser cement matrix. Red mud is an industrial by-product generated during the extraction of bauxite from bauxite ore, containing rich mineral components such as aluminum, iron, and calcium. Red mud contains rich bauxite minerals and some active components, which can be used as an admixture to enhance the strength of concrete and has a certain cement substitution effect. The introduction of red mud can improve the impermeability, corrosion resistance, and durability of concrete. The components of red mud can react with the hydration products in cement to produce hydrated aluminates, thereby promoting the hydration reaction of concrete. In addition, the iron element in red mud can also improve the antioxidant ability of concrete, and further improve the overall performance of concrete when acting together with slag, fly ash, etc.

[0017] Hybrid fibers have high strength, toughness, and impact resistance. When added to modified coal gangue and combined with fly ash and nano-aluminum oxide, they not only fill the gaps between the modified coal gangue, but also effectively inhibit the generation of cracks in subsequent concrete applications, helping to improve the crack resistance and impermeability of the modified coal gangue, and enhancing the strength, toughness, and durability of the modified coal gangue. Moreover, the combination of hybrid fibers and other components can significantly improve the crack control performance of concrete. When materials such as coal gangue and slag react with the cement matrix, the fibers can effectively inhibit the crack propagation, thereby enhancing the overall mechanical properties and durability of concrete.

[0018] Thus, by adopting the above multi-step modification measures, the physicochemical properties of coal gangue can be significantly improved, and its strength performance in concrete can be enhanced. After the modified coal gangue is treated, the bonding force between it and the cement matrix is strengthened, thus avoiding the problem of concrete strength decline caused by unmodified coal gangue. Due to the combined action of the modified coal gangue and other admixtures (such as slag, fly ash, etc.), the comprehensive performance of concrete is optimized. The incorporation of the modified coal gangue not only improves the strength of concrete, but also enhances the durability performance such as impermeability and crack resistance of concrete. This scheme uses the waste coal gangue as aggregate, reducing the stacking and treatment burden of coal gangue, which is helpful for environmental protection. In addition, the utilization of industrial wastes such as red mud and fly ash not only saves natural resources, but also reduces the environmental impact of wastes. By reasonably designing and matching these components, their advantages can be maximally exerted to achieve the comprehensive improvement of the performance of concrete aggregates.

[0019] As an implementable embodiment, the weight ratio of the secondary-treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is (5-10):(1-2):(0.5-1):(0.02-0.05).

[0020] As an implementable embodiment, the weight ratio of the secondary-treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is 5:1:0.5:0.02.

[0021] In this embodiment, after verification, when the weight ratio of the secondary-treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator is within the above range, this modified coal gangue treated by polymer has improved hydrophilicity, adhesion and enhanced mechanical properties, making the modified coal gangue have a better effect on improving the strength of concrete.

[0022] As an implementable embodiment, the initiator includes any one of ammonium persulfate, benzoyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide and hydrogen peroxide.

[0023] Optionally, the titanate coupling agent includes tetra(2-ethylhexyl) titanate, tetra(octyl) titanate, tetra(isopropoxy) titanate or tris(3-aminopropyl) titanate.

[0024] As an implementable embodiment, the hybrid fiber includes modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano-silica powder and amino-silane coupling agent with a weight ratio of (30-40):(5-10):(2-5):(10-15):(15-20):(2-4).

[0025] In this embodiment, polyphenylene sulfide has good chemical stability and high temperature resistance, and can enhance the anti-aging and anti-corrosion properties of concrete aggregates. Nanoscale fibers can provide more contact surfaces, help improve the bonding property and mechanical properties of concrete aggregates, and enhance the strength and toughness of the modified coal gangue concrete aggregates. Carbon nanotubes are widely used due to their excellent electrical conductivity and mechanical properties (such as high strength and high stiffness). The role of carbon nanotubes in the hybrid fibers is mainly to enhance the mechanical strength and crack resistance of concrete aggregates. They can improve the overall mechanical properties of concrete aggregates, especially in terms of compressive strength and tensile strength, by enhancing the interfacial bonding between the modified coal gangue aggregates and the fibers. Graphene oxide has a large specific surface area, good dispersibility and strengthening effect, and can play a role in enhancing the mechanical properties, improving the electrical conductivity, and increasing the heat resistance and chemical stability of concrete aggregates. When acting synergistically with other components, graphene oxide will improve the overall performance of the entire concrete aggregate by improving the bonding force between fibers and the interfacial compatibility between the modified coal gangue aggregates and the fibers. Polytetrafluoroethylene fibers have excellent chemical stability and high temperature resistance characteristics, but their own mechanical properties are relatively low. Adding polytetrafluoroethylene fibers may play an important role in enhancing the corrosion resistance, wear resistance and stability at high temperatures of the hybrid fibers in concrete aggregates. Polytetrafluoroethylene can improve the processing performance of concrete aggregates and reduce friction and wear. Nano-silica powder is usually used for the hardness, wear resistance and crack resistance of concrete aggregates. It can act synergistically with other components (such as polyphenylene sulfide and carbon nanotubes) to enhance the overall compressive strength and heat resistance of the composite material, and at the same time improve the impact resistance of concrete aggregates. Amino silane coupling agents are usually used to enhance the interfacial bonding force between fibers and matrix materials (such as coal gangue aggregates). It can effectively improve the dispersibility and adhesiveness of fibers in concrete aggregates, promote the interaction between different components, and thus improve the mechanical properties and durability of the material. Through the synergistic action of different components, the hybrid fibers can achieve significant performance improvement in the modified coal gangue aggregates, especially in terms of mechanical properties, thermal stability and interfacial adhesiveness. It should be noted that the physical and chemical characteristics of each component are different and they can complement each other. For example, the combination of the strengthening effect of graphene oxide and carbon nanotubes and the high temperature resistance characteristics of modified polyphenylene sulfide fibers can significantly improve the comprehensive performance of concrete aggregates; amino silane coupling agents can improve the bonding force between aggregates and fibers, promote the dispersion of nano-materials such as carbon nanotubes and graphene oxide, and reduce their aggregation phenomenon, thereby improving the mechanical properties of the composite material; carbon nanotubes and graphene oxide can provide additional mechanical strengthening for concrete aggregates, improving the tensile strength, compressive strength and impact resistance; modified polyphenylene sulfide nanofibers can provide better fatigue resistance; the addition of polytetrafluoroethylene fibers in the composite material can improve the high temperature resistance and corrosion resistance of the material, and synergistically enhance the environmental adaptability and service life of the material.This synergistic enhancement effect can effectively improve the comprehensive properties of concrete aggregates and is applicable to engineering fields with requirements such as high strength, high temperature resistance, and corrosion resistance.

[0026] For example, when applied to concrete, polyphenylene sulfide (PPS) nanofibers have excellent high temperature resistance, corrosion resistance, and toughness, which can increase the crack resistance of concrete and improve its compressive strength and anti-aging performance. The addition of carbon nanotubes can significantly enhance the mechanical properties of concrete, especially the tensile strength and flexural strength. The high rigidity and good dispersion performance of carbon nanotubes can significantly improve the crack resistance of concrete. Graphene can significantly improve the electrical conductivity and impermeability of concrete, while increasing its crack resistance and compressive strength. In particular, the combination of nano-graphene and other fibers can produce a synergistic strengthening effect. Polytetrafluoroethylene fibers have excellent chemical stability, corrosion resistance, and low friction characteristics. After adding them, the impermeability and durability of concrete can be improved, especially suitable for use in harsh environments. Nano-silica powder can fill the fine pores of concrete, improve the density, and thus significantly enhance the impermeability and compressive strength. It is used to improve the adhesion between fibers and the cement matrix, enhance the bonding force between fibers and the matrix, and improve the overall mechanical properties of concrete. The morphology and properties of PPS nanofibers, carbon nanotubes, graphene, and polytetrafluoroethylene fibers are complementary, and they can form a three-dimensional network structure inside the concrete. The addition of graphene and carbon nanotubes can enhance the crack resistance and impermeability of concrete, while PPS fibers and polytetrafluoroethylene fibers further improve the toughness and durability of concrete. Nano-silica powder and mineralized graphene fillers not only help to improve the impermeability of concrete, but also fill the fine pores in the concrete, reduce the porosity, thereby increasing the density and enhancing its compressive strength. Amino silane coupling agents effectively improve the bonding force between fibers and the cement matrix, ensuring the dispersion and stability of these reinforcing fibers in the concrete. Through the optimized design of the composite material, by utilizing the synergistic effect of PPS nanofibers, carbon nanotubes, graphene, polytetrafluoroethylene fibers, and nano-silica powder, the impermeability, waterproof performance, and mechanical strength of concrete can be significantly improved. These fibers and fillers can not only improve the microstructure of concrete, but also provide better adhesion and dispersion, thus enhancing the overall performance of concrete.

[0027] As an achievable implementation method, the amino silane coupling agents include KH550 (3-aminopropyltriethoxysilane), KH570 (3-aminopropyltrimethoxysilane), APTES (3-aminopropyltriethoxysilane), KH600 (3-aminopropyltrichlorosilane), KH540 (β-aminopropyltriethoxysilane), KH570 (3-aminopropyltrimethoxysilane), γ-aminopropyltriethoxysilane (APS), N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AEAPS), or 3-aminopropyltriisopropoxysilane (KH710).

[0028] As an implementable embodiment, the hybrid fibers are prepared by the following method:

[0029] Prepare an amino silane coupling agent solution with a concentration of 3% using distilled water. After mixing modified polyphenylene sulfide nanofibers and polytetrafluoroethylene fibers in a predetermined ratio in ethanol or distilled water, add them to the 3% amino silane coupling agent solution;

[0030] Add carbon nanotubes, graphene oxide, and nano silicon powder to the amino silane coupling agent solution in a predetermined ratio, and perform ultrasonic treatment for 30 - 60 min. After suction filtration, washing, and drying, the hybrid fibers are obtained.

[0031] In this embodiment, polyphenylene sulfide nanofibers, carbon nanotubes, polytetrafluoroethylene fibers, graphene, and nano silicon powder are mixed in a predetermined ratio. The fiber surface is treated with an amino silane coupling agent to enhance its hydrophilicity and adhesion to the cement matrix. The mixture is soaked in an appropriate solution (such as a water / alcohol solution) to remove residual organic groups on its surface and improve its dispersibility. For example, the ultrasonic dispersion method is used to improve the dispersion degree of the fibers and fillers. This step can ensure the uniform distribution of the fibers and graphene and reduce the agglomeration phenomenon.

[0032] As an implementable embodiment, the preparation method of the modified polyphenylene sulfide nanofibers includes the following steps:

[0033] Add 10 g of polyphenylene sulfide nanofibers to a nitric acid solution with a concentration of 10 - 18%, stir for 1 - 3 h, wash with water, then immerse in absolute ethanol for 1 - 2 h, filter dry with a vacuum filter, and dry at a temperature of 70 °C for 3 h to obtain dry polyphenylene sulfide nanofibers;

[0034] Immerse the polyphenylene sulfide nanofibers in an aqueous solution of 3 wt.% silane coupling agent, heat to 70 °C and soak for 2 h. After cooling to room temperature, filter dry with a vacuum filter, then wash with ethanol 3 times, and dry in an oven at 75 °C to obtain polyphenylene sulfide nanofibers loaded with the silane coupling agent;

[0035] Put the polyphenylene sulfide nanofibers loaded with the silane coupling agent into 1000 ml of ethanol solvent, add 1 wt.% cetyltrimethylammonium chloride, and stir evenly to obtain a polyphenylene sulfide nanofiber mixture;

[0036] Add 30 - 40 ml of ammonia water to the polyphenylene sulfide nanofiber mixture as a catalyst, and disperse it by ultrasonic wave for 30 - 60 minutes. Then, under stirring conditions, add 60 - 80 ml of tetraethyl orthosilicate dropwise to the mixture, and stir and react at a constant temperature of 45 °C for 12 hours to obtain polyphenylene sulfide nanofibers with a silica nanoparticle coating on the surface. Take out the polyphenylene sulfide nanofibers with a silica nanoparticle coating on the surface from the solution, dry them with a vacuum filter, wash them three times with methanol, and place them in an oven at 75 °C for 12 hours of drying;

[0037] Mix 0.1 - 0.5 g of ferrocene evenly with the polyphenylene sulfide nanofibers with a silica nanoparticle coating on the surface. Pour the obtained mixture into a crucible and place it in a microwave oven for 10 - 15 seconds of microwave radiation, and then cool it to room temperature to obtain modified polyphenylene sulfide nanofibers with a silica nanoparticle and carbon nanotube coating on the surface.

[0038] In this embodiment, polyphenylene sulfide (PPS) is a polymer material with high thermal stability and excellent electrical insulation properties. However, its surface energy is relatively low, which may be unfavorable for the combination with other materials. By immersing polyphenylene sulfide nanofibers in a concentrated nitric acid solution, impurities that may exist on the surface can be removed, and the surface hydrophilicity can be increased, thereby enhancing its compatibility with subsequent coupling agents and other functional materials. In the silane coupling agent molecule, there are reaction groups with the polyphenylene sulfide molecular chain (such as -CHO, -NH2, etc.), and there are also reaction groups with inorganic materials (such as nano-silica) (such as Si-OH). Through the modification of the silane coupling agent, not only can the binding force between the polyphenylene sulfide nanofibers and materials such as nano-silica be improved, but also the interfacial adhesion of the fibers can be improved, thereby enhancing their composite properties. Nano-silica is deposited on the surface of polyphenylene sulfide nanofibers through the reaction of tetraethyl orthosilicate (TEOS). This coating step can significantly improve the surface properties of the fibers, enabling them to have better mechanical properties, thermal stability, and enhanced surface affinity. The introduction of nano-silica can improve the interaction between the fibers and the external interface (such as aggregates or matrix materials), increasing the mechanical strength of the composite material. Microwave radiation treatment can promote the cross-linking reaction between materials by rapidly heating the modified materials, improving the mechanical strength and stability of the composite fibers. At the same time, microwave radiation helps to heat rapidly and uniformly, avoiding the problem of uneven temperature that may exist in traditional heating methods. When the concrete aggregate with the modified polyphenylene sulfide nanofibers is applied in concrete, nano-silica mainly reacts with Ca(OH)2 at the interface between the fibers and the cement matrix, reducing the size and quantity of Ca(OH)2, thereby making the interfacial bonding strength higher. And carbon nanotubes form a network structure between the carbon nanotubes and the cement-based material through physical connection, thereby improving the interfacial bonding strength between the fibers and the cement matrix. To make the combination between the fibers and the cement matrix closer, two kinds of nano-materials, nano-silica and carbon nanotubes, are grown on the surface of the carbon fibers, and both chemical and physical methods act simultaneously at the interface between the fibers and the cement matrix to achieve a better strengthening effect.

[0039] Grow various nanomaterials such as nano-silica and carbon nanotubes on polyphenylene sulfide nanofibers to achieve nano-hybridization. Specifically, through surface treatment (cleaning with nitric acid solution) and loading of silane coupling agents, the compatibility of polyphenylene sulfide nanofibers with other materials (such as nano-silica, coal gangue, etc.) is greatly improved. This enhanced interfacial bonding force helps to improve the overall mechanical properties of the composite material. The coating of nano-silica and carbon nanotubes endows polyphenylene sulfide nanofibers with higher rigidity and strength. At the same time, due to the unique properties of silica and carbon nanotubes, they can play a strengthening role in the composite material, enhancing its compressive strength and tensile strength. The addition of nano-silica and carbon nanotubes not only improves the strength of the fibers but also improves their dispersion in the composite material. Through ultrasonic treatment, a better dispersion network is formed between nano-silica and polyphenylene sulfide nanofibers, avoiding the agglomeration of nanoparticles and thus exerting their maximum strengthening effect. Microwave radiation enables the polyphenylene sulfide nanofibers to reach uniform heating in a short time, promoting the cross-linking reaction inside the material, making the entire modification process more efficient and better controlled. After the surface of polyphenylene sulfide nanofibers is modified with silane coupling agents, nano-silica and carbon nanotubes, a stronger bonding force can be formed between the coal gangue aggregate and the polymer matrix. In particular, the silane coupling agent can effectively improve the interfacial bonding property by reacting with the surface functional groups of the coal gangue. The modified polyphenylene sulfide nanofibers have higher tensile strength and rigidity. When combined with coal gangue, they can effectively share the external load and improve the mechanical properties such as compressive strength and flexural strength of the composite material.

[0040] As an achievable embodiment, the ratio of tetraethyl orthosilicate, ammonia water, and ferrocene is 60 - 80 ml: 30 - 40 ml: 0.1 - 0.5 g.

[0041] As an achievable embodiment, the ratio of tetraethyl orthosilicate, ammonia water, and ferrocene is 60 ml: 30 ml: 0.1 g.

[0042] In this embodiment, after verification, when in the above ratio, the nano-silica and carbon nanotubes grown on the polyphenylene sulfide nanofibers are relatively uniform, making the concrete aggregate added with the modified polyphenylene sulfide nanofibers have a better effect on improving the concrete strength.

[0043] In the second aspect, the embodiment of the present application also provides a preparation method of the concrete aggregate based on modified coal gangue in the first aspect above, including the following steps: Mix 35 - 40 parts of slag, 5 - 9 parts of nano-aluminum oxide, 80 - 100 parts of red mud, 10 - 20 parts of fly ash, 80 - 100 parts of modified coal gangue, and 10 - 15 parts of hybrid fibers evenly to obtain the concrete aggregate; wherein, the preparation method of the modified coal gangue includes the following steps:

[0044] After the coal gangue is ground into powder by ball milling, it is sieved with a 150-mesh standard sieve to obtain fine coal gangue powder;

[0045] The coal gangue powder is soaked in a sulfuric acid solution with a concentration of 40-50%, the slag and liquid are separated, the soaked coal gangue slag is dried, and then it is soaked in an ammonia water solution with a concentration of 25-30%, the slag and liquid are separated, and dried to obtain the primary treated coal gangue;

[0046] A titanate coupling agent solution with a concentration of 10-12% is prepared with ethanol, the primary treated coal gangue is impregnated therein, the impregnation time is controlled to be 45-60 min, the coal gangue is taken out, and rinsed 2-3 times with distilled water, and dried to obtain the secondary treated coal gangue;

[0047] Polyvinyl alcohol is dissolved in deionized water to form a 10% polyvinyl alcohol solution. The secondary treated coal gangue is mixed with the polyvinyl alcohol solution, methyl acrylate and an initiator are added, and after stirring evenly, it is heated to 80 °C and reacted for 1-2 h. After cooling, the slag and liquid are separated and dried to obtain the modified coal gangue; the weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is (1-10):(0.5-3):(0.2-1):(0.005-0.05).

[0048] In a third aspect, the present application also provides an application of the concrete aggregate based on the modified coal gangue in the first aspect above in concrete. When the above concrete aggregate is applied to concrete, admixtures such as slag, red mud and fly ash react with cement to generate more hydration products, fill the voids in the concrete, enhance the compactness of the concrete, reduce the porosity, and improve the strength. The addition of the modified coal gangue improves the aggregate strength of the concrete and the bonding force with the cement matrix, and further improves the compressive strength of the concrete. The synergistic effect of red mud, slag and fly ash not only improves the strength, but also improves the impermeability and corrosion resistance. The hybrid fibers disperse the stress, inhibit the formation and expansion of cracks, enhance the crack resistance of the concrete, and cooperate with other materials to jointly improve the impact resistance and tensile strength of the concrete. The hybrid fibers disperse the stress, inhibit the formation and expansion of cracks, enhance the crack resistance of the concrete, and cooperate with other materials to jointly improve the impact resistance and tensile strength of the concrete. Detailed implementation manners

[0049] The technical solutions in the embodiments of the present application will be described below.

[0050] It should be specifically noted that: unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The experimental reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments, and equipment used in the following embodiments can all be obtained through market purchase or by existing methods; the dosages of the experimental reagents are all the dosages in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0051] The cement in the embodiments of the present application is P.O42.5 cement. The water reducer is a polycarboxylic acid high-performance water reducer with a water reduction rate of 26.8%. The initiator is ammonium persulfate (APS, 98wt.%), purchased from J&K Scientific. Nano-aluminum oxide and carbon nanotubes are purchased from Shanghai Liantian Materials Technology Co., Ltd. The length of the polyphenylene sulfide nanofibers is 4 - 100μm, and the diameter is 50 - 500nm. The length of the polytetrafluoroethylene fibers is 7 - 8mm, and the diameter is 30 - 60μm. Tetraethyl orthosilicate (TEOS, analytical pure) is purchased from Sinopharm Chemical Reagent Co., Ltd. The amino-silane coupling agent is KH550 (3-aminopropyltriethoxysilane, 98wt.%). Anhydrous ethanol (AR, 99.7%); ammonia water without special indication of concentration is concentrated ammonia water (AR, 25% - 30%). Cetyltrimethylammonium bromide (CTAB, analytical pure, ≥99.0wt.%). Ferrocene (98wt.%). The fineness of the fly ash is 15.6%, the bulk density is 0.63g / cm, the specific surface area is 1400m / kg, and the 28d activity index is 95%.

[0052] The room temperature in the embodiments of the present application is 25°C.

[0053] The following details the concrete aggregates provided in the embodiments of the present application.

[0054] Preparation example of modified coal gangue

[0055] Preparation example 1 - 1

[0056] The preparation method of the modified coal gangue includes the following steps:

[0057] Step 1: Grind 1 part of coal gangue into powder by ball milling and sieve it with a 150-mesh standard sieve to obtain fine coal gangue powder;

[0058] Step 2: Immerse the coal gangue powder in a sulfuric acid solution with a concentration of 40%, separate the residue and the liquid, dry the soaked coal gangue residue, then immerse it in an ammonia water solution with a concentration of 25%, separate the residue and the liquid, and dry it to obtain the once-treated coal gangue;

[0059] Step 3: Prepare a 10% solution of tetra(2-ethylhexyl) titanate coupling agent with ethanol. Immerse the once-treated coal gangue in it, control the immersion time to be 50 min, take out the coal gangue, and rinse it with distilled water 2 - 3 times. After drying, obtain the twice-treated coal gangue;

[0060] Step 4: Dissolve polyvinyl alcohol in deionized water to form a 10% polyvinyl alcohol solution. Mix the twice-treated coal gangue with the polyvinyl alcohol solution, add methyl acrylate and ammonium persulfate, stir evenly, heat to 80 °C, react for 1.5 h, separate the cooled slag and liquid, and dry to obtain the modified coal gangue; among them, the weight ratio of the twice-treated coal gangue, polyvinyl alcohol, methyl acrylate, and initiator in the modified coal gangue is 1:0.5:0.2:0.005.

[0061] Preparation Example 1-2

[0062] The difference from Preparation Example 1-1 is that the weight ratio of the twice-treated coal gangue, polyvinyl alcohol, methyl acrylate, and initiator in the modified coal gangue is 5:1:0.5:0.02.

[0063] Preparation Example 1-3

[0064] The difference from Preparation Example 1-1 is that the weight ratio of the twice-treated coal gangue, polyvinyl alcohol, methyl acrylate, and initiator in the modified coal gangue is 10:3:1:0.05.

[0065] Preparation Example 1-4

[0066] The difference from Preparation Example 1-1 is that Step 3 is omitted.

[0067] Preparation Example 1-5

[0068] The difference from Preparation Example 1-1 is that Step 4 is omitted.

[0069] Hybrid Fiber Preparation Example

[0070] Preparation Example 2-1

[0071] The hybrid fiber includes modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano-silica powder, and amino-silane coupling agent with a weight ratio of (30 - 40):(5 - 10):(2 - 5):(10 - 15):(15 - 20):(2 - 4).

[0072] The hybrid fiber is prepared by the following method:

[0073] Prepare a 3% KH550 amino-silane coupling agent solution using distilled water. After mixing 30 parts of modified polyphenylene sulfide nanofibers and 5 parts of polytetrafluoroethylene fibers in ethanol or distilled water according to a predetermined ratio, add them to the 3% amino-silane coupling agent solution.

[0074] According to a predetermined ratio, add 2 parts of carbon nanotubes, 10 parts of graphene oxide, and 15 parts of nano-silica powder to the KH550 amino-silane coupling agent solution, and perform ultrasonic treatment for 60 min. After suction filtration, washing, and drying, the hybrid fibers are obtained.

[0075] Among them, the preparation method of the modified polyphenylene sulfide nanofibers includes the following steps:

[0076] Add 10 g of polyphenylene sulfide nanofibers to a 10% nitric acid solution, stir for 1 h, wash with water, then immerse in absolute ethanol for 1 h, filter dry with a vacuum filter, and dry at 70 °C for 3 h to obtain dry polyphenylene sulfide nanofibers.

[0077] Immerse the polyphenylene sulfide nanofibers in a 3 wt.% aqueous solution of KH550 silane coupling agent, heat to 70 °C, soak at a constant temperature for 2 h, cool to room temperature, filter dry with a vacuum filter, wash 3 times with ethanol, and dry in an oven at 75 °C to obtain polyphenylene sulfide nanofibers loaded with the silane coupling agent.

[0078] Put the polyphenylene sulfide nanofibers loaded with the silane coupling agent into 1000 ml of ethanol solvent, add 1 wt.% cetyltrimethylammonium chloride, and stir evenly to obtain a polyphenylene sulfide nanofiber mixture.

[0079] Add 40 ml of ammonia water as a catalyst to the polyphenylene sulfide nanofiber mixture, disperse it by ultrasonic wave for 30 min. Then, under stirring conditions, add 80 ml of tetraethyl orthosilicate dropwise to the mixture at a dropping rate of 1 drop / s, and stir and react at a constant temperature of 45 °C for 12 h to obtain polyphenylene sulfide nanofibers with a surface coated with nano-silica. Take out the polyphenylene sulfide nanofibers with a surface coated with nano-silica from the solution, filter dry with a vacuum filter, wash 3 times with methanol, and dry in an oven at 75 °C for 12 h.

[0080] Mix the polyphenylene sulfide nanofibers with a surface coated with nano-silica evenly with 0.1 g of ferrocene. Pour the obtained mixture into a crucible, place it in a microwave oven, irradiate with microwaves for 15 s, and then cool to room temperature to obtain modified polyphenylene sulfide nanofibers with a surface coated with nano-silica and carbon nanotubes.

[0081] Preparation Example 2-2

[0082] The difference from Preparation Example 2-1 is that the hybrid fibers include modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano-silica powder, and amino-silane coupling agent with a weight ratio of 35:7:3:12:17:3.

[0083] Preparation Example 2-3

[0084] The difference from Preparation Example 2-1 is that the hybrid fibers include modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano-silica powder, and amino-silane coupling agent with a weight ratio of 40:10:5:15:20:4.

[0085] Preparation Example 2-4

[0086] The difference from Preparation Example 2-1 is that no modified polyphenylene sulfide nanofibers are added to the hybrid fibers.

[0087] Preparation Example 2-5

[0088] The difference from Preparation Example 2-1 is that the modified polyphenylene sulfide nanofibers added to the hybrid fibers are changed to unmodified ordinary polyphenylene sulfide nanofibers.

[0089] Preparation Example 2-6

[0090] The difference from Preparation Example 2-1 is that no polytetrafluoroethylene fibers are added to the hybrid fibers.

[0091] Preparation Example 2-7

[0092] The difference from Preparation Example 2-1 is that no carbon nanotubes, graphene oxide, nano-silica powder, and amino-silane coupling agent are added to the hybrid fibers.

[0093] Preparation Example 2-8

[0094] The difference from Preparation Example 2-1 is that no carbon nanotubes and graphene oxide are added to the hybrid fibers.

[0095] Preparation Example 2-9

[0096] The difference from Preparation Example 2-1 is that no nano-silica powder and amino-silane coupling agent are added to the hybrid fibers.

[0097] Preparation Example 2-10

[0098] The difference from Preparation Example 2-1 is that the preparation method of the modified polyphenylene sulfide nanofibers includes the following steps:

[0099] Add 10 g of polyphenylene sulfide nanofibers to a nitric acid solution with a concentration of 10%, stir for 1 h, wash with water, then immerse in absolute ethanol for 1 h, filter dry with a vacuum filter, and dry at 70 °C for 3 h to obtain dry polyphenylene sulfide nanofibers;

[0100] Immerse the polyphenylene sulfide nanofibers in an aqueous solution of 3 wt.% KH550 silane coupling agent, heat to 70 °C and soak at a constant temperature for 2 h. After cooling to room temperature, filter dry with a vacuum filter, then wash with ethanol 3 times, and place in an oven at 75 °C to dry to obtain polyphenylene sulfide nanofibers loaded with the silane coupling agent;

[0101] Put the polyphenylene sulfide nanofibers loaded with the silane coupling agent into 1000 ml of ethanol solvent, add 1 wt.% cetyltrimethylammonium chloride, and stir evenly to obtain a polyphenylene sulfide nanofiber mixture;

[0102] Add 35 ml of ammonia water to the polyphenylene sulfide nanofiber mixture as a catalyst, disperse it by ultrasonic wave, with the ultrasonic time being 45 min. Then, under stirring conditions, add 70 ml of tetraethyl orthosilicate dropwise to the mixture at a dropping rate of 2 drops / s, and stir and react at a constant temperature of 45 °C for 12 h to obtain polyphenylene sulfide nanofibers with nano-silica coated on the surface. Take out the polyphenylene sulfide nanofibers with nano-silica coated on the surface from the solution, filter dry with a vacuum filter, wash with methanol 3 times, and place in an oven at 75 °C to dry for 12 h;

[0103] Mix 0.5 g of ferrocene evenly with the polyphenylene sulfide nanofibers with nano-silica coated on the surface. Pour the obtained mixture into a crucible and place it in a microwave oven for microwave radiation for 13 s, then cool to room temperature to obtain modified polyphenylene sulfide nanofibers with nano-silica and carbon nanotubes coated on the surface.

[0104] Preparation Example 2-11

[0105] The difference from Preparation Example 2-1 is that the preparation method of the modified polyphenylene sulfide nanofibers includes the following steps:

[0106] Add 10 g of polyphenylene sulfide nanofibers to a nitric acid solution with a concentration of 10%, stir for 1 h, wash with water, then immerse in absolute ethanol for 1 h, filter dry with a vacuum filter, and dry at 70 °C for 3 h to obtain dry polyphenylene sulfide nanofibers;

[0107] Immerse the polyphenylene sulfide nanofibers in an aqueous solution of 3 wt.% KH550 silane coupling agent, heat to 70 °C and soak at a constant temperature for 2 h. After cooling to room temperature, filter dry with a vacuum filter, then wash with ethanol 3 times, and place in an oven at 75 °C to dry to obtain polyphenylene sulfide nanofibers loaded with the silane coupling agent;

[0108] Put the polyphenylene sulfide nanofibers loaded with silane coupling agent into 1000 ml of ethanol solvent, add 1 wt.% of cetyltrimethylammonium chloride, and stir evenly to obtain a polyphenylene sulfide nanofiber mixture;

[0109] Add 30 ml of ammonia water as a catalyst to the polyphenylene sulfide nanofiber mixture, disperse it by ultrasonic wave, and the ultrasonic time is 60 min. Then, under stirring conditions, add 60 ml of tetraethyl orthosilicate dropwise to the mixture at a dropping rate of 3 drops / s, and stir and react at a constant temperature of 45 °C for 12 h to obtain polyphenylene sulfide nanofibers coated with nano-silica on the surface. Take out the polyphenylene sulfide nanofibers coated with nano-silica on the surface from the solution, dry them with a vacuum filter, wash them 3 times with methanol, and place them in an oven at 75 °C for drying for 12 h;

[0110] Mix the polyphenylene sulfide nanofibers coated with nano-silica on the surface evenly with 0.3 g of ferrocene. Pour the obtained mixture into a crucible and place it in a microwave oven for microwave radiation for 10 s, and then cool it to room temperature to obtain modified polyphenylene sulfide nanofibers coated with nano-silica and carbon nanotubes on the surface.

[0111] Example 1

[0112] A preparation method of concrete aggregate based on modified coal gangue, comprising the following steps:

[0113] Mix 35 parts of slag, 5 parts of nano-aluminum oxide, 80 parts of red mud, 10 parts of fly ash, 80 parts of modified coal gangue, and 10 parts of hybrid fiber evenly to obtain concrete aggregate. Among them, the modified coal gangue is prepared by Preparation Example 1-1; the hybrid fiber is prepared by Preparation Example 2-1.

[0114] Example 2

[0115] A preparation method of concrete aggregate based on modified coal gangue, comprising the following steps:

[0116] Mix 38 parts of slag, 7 parts of nano-aluminum oxide, 90 parts of red mud, 15 parts of fly ash, 90 parts of modified coal gangue, and 13 parts of hybrid fiber evenly to obtain concrete aggregate. Among them, the modified coal gangue is prepared by Preparation Example 1-1; the hybrid fiber is prepared by Preparation Example 2-1.

[0117] Example 3

[0118] A preparation method of concrete aggregate based on modified coal gangue, comprising the following steps:

[0119] Mix 40 parts of slag, 9 parts of nano-aluminum oxide, 100 parts of red mud, 20 parts of fly ash, 100 parts of modified coal gangue, and 15 parts of hybrid fiber evenly to obtain concrete aggregate. Among them, the modified coal gangue is prepared by Preparation Example 1-1; the hybrid fiber is prepared by Preparation Example 2-1.

[0120] Examples 4 to 15

[0121] Examples 4 to 15 also provide a kind of concrete aggregate based on modified coal gangue. The difference from Example 1 is that the preparation examples of the modified coal gangue or the hybrid fibers are different, as shown in Table 1 specifically. It should be noted that the component categories and dosages not shown in the table are the same as those in Example 1.

[0122] Table 1 Preparation examples of the modified coal gangue or the hybrid fibers in Examples 4 to 15

[0123]

[0124]

[0125] Comparative examples

[0126] Comparative example 1

[0127] A kind of concrete aggregate, the difference from Example 1 is that the modified coal gangue is prepared by Preparation examples 1 - 4.

[0128] Comparative example 2

[0129] A kind of concrete aggregate, the difference from Example 1 is that the modified coal gangue is prepared by Preparation examples 1 - 5.

[0130] Comparative example 3

[0131] A kind of concrete aggregate, the difference from Example 1 is that the hybrid fibers are replaced with an equal amount of polypropylene fibers.

[0132] Performance detection test

[0133] The concrete aggregates prepared in Examples 1 - 14 and Comparative examples 1 - 3 are formulated into concrete, and the specific formulation is as follows: 70 kg of cement, 10 kg of silica fume, 40 kg of concrete aggregate, 6 kg of water reducing agent, and 24 kg of water.

[0134] Carry out relevant performance detections on the concrete:

[0135] Slump: The slump is a method and index for measuring the workability of concrete. Usually, a slump test is conducted to measure the fluidity of the mixture. Grade T1 is low - plasticity concrete with a slump of 10 - 40 mm; Grade T2 is plastic concrete with a slump of 50 - 90 mm; Grade T3 is flowing concrete with a slump of 100 - 150 mm; T4 is high - flowing concrete with a slump ≥ 160 mm. Test the slump of the concrete mixture at room temperature (20 ± 5)°C according to the slump test in the Standard for Test Methods of Performance of Ordinary Concrete Mixtures GB / T50080 - 2016.

[0136] Compressive strength: The mechanical properties were tested in accordance with the Standard Test Method for Physical and Mechanical Properties of Concrete (GB / T 50081-2019), and the standard curing age was 7 and 28 days.

[0137] Chloride ion diffusion coefficient: The chloride ion diffusion coefficient of the standard test specimens was tested according to the RCM method in the Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete (GB / T 50082-2009).

[0138] Water penetration resistance: The water penetration depth of the standard test specimens was tested according to the step-by-step pressure method in the Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete (GB / T 50082-2009).

[0139] According to the standard of DL / T5332-2005 "Test Code for Fracture of Hydraulic Concrete", the mechanical properties of the above-prepared concrete were detected to obtain the fracture toughness of the concrete, and the cracking area of the concrete was tested according to GB / T 50081-2019. The test results are shown in Table 2.

[0140] Table 2 Test data of examples and comparative examples

[0141]

[0142]

[0143] It can be seen from the data in Table 2 that the 7-day compressive strength of the concrete prepared in Examples 1-15 of this application reached 93 MPa, the 28-day compressive strength reached 115 MPa, and the maximum 28-day drying shrinkage value was 232×10 -6 m, and the maximum fracture toughness was 13.4 MPa·m 1 / 2 , indicating that the concrete prepared with the concrete aggregate based on modified coal gangue in the examples of this application has high compressive strength, fracture toughness and impact resistance, achieving the purpose of using coal gangue as a weak aggregate in concrete without reducing the mechanical properties of the concrete. At the same time, the slump of the concrete in Examples 1-15 reached 230 mm, with excellent fluidity and workability. The chloride ion diffusion coefficient was less than 2.24×10 -12 m 2 ·S -1 , and the cracking area was small, that is, the possibility of concrete cracking was small, and the water penetration depth of the standard specimens was small, with excellent water resistance.

[0144] It can be seen from Example 1 and Comparative Example 1 in combination with the data in Table 2 that, compared with Example 1, the 7-day and 28-day compressive strengths and 28-day fracture toughness of the concrete prepared in Comparative Example 1 without being treated by the coupling agent immersion are all less than those in Example 1, indicating that immersing gangue in a certain concentration of titanate coupling agent can enhance the chemical bonding force between gangue and the cement matrix, contribute to improving the hydrophilicity of gangue, and improve its adhesiveness with the cement paste in concrete, thereby enhancing the mechanical properties of the concrete when the concrete aggregate prepared from modified gangue is added to the concrete.

[0145] It can be seen from Example 1 and Comparative Example 2 in combination with the data in Table 2 that, compared with Example 1, the 7-day and 28-day compressive strengths and 28-day fracture toughness of the concrete prepared from gangue without being treated by the polymer are all less than those in Example 1, indicating that after being chemically modified by the polymer, it has good dispersibility and hydrophilicity, which can enhance its application effect in concrete, such as enhancing the mechanical properties of the concrete.

[0146] It can be seen from Example 1 and Examples 4-5 in combination with the data in Table 2 that, compared with Example 1, the weight ratio of the secondary-treated gangue, polyvinyl alcohol, methyl acrylate, and initiator in the modified gangue can significantly affect the mechanical properties, impermeability, and crack resistance of the concrete. Among them, Example 4 with the weight ratio of the secondary-treated gangue, polyvinyl alcohol, methyl acrylate, and initiator in the modified gangue being 5:1:0.5:0.02 has better comprehensive performance of the concrete.

[0147] It can be seen from Example 1 and Comparative Example 3 in combination with the data in Table 2 that, compared with Comparative Example 3, for Example 1 using hybrid fibers, the fluidity, mechanical properties, impermeability, toughness, and crack resistance of the concrete are all greater than those of the single-dosage fiber in Comparative Example 3. At the same time, it can be seen from Example 1, Examples 8-10 in combination with the data in Table 2 that the modified polyphenylene sulfide nanofibers are not added to the hybrid fibers in Example 8, ordinary polyphenylene sulfide nanofibers are added to the hybrid fibers in Example 9, and polytetrafluoroethylene fibers are not added to the hybrid fibers in Example 10. Compared with Example 1, the slump of the prepared concrete decreases, and the 7-day and 28-day compressive strengths and fracture toughness all decrease significantly. In particular, the performance of the concrete without adding modified polyphenylene sulfide nanofibers in Example 8 decreases most significantly, indicating that the lack of either modified polyphenylene sulfide nanofibers or polytetrafluoroethylene fibers in the hybrid fibers will affect the compressive and crack resistance of the concrete.

[0148] In the hybrid fibers of Example 11, carbon nanotubes, graphene oxide, nano-silica powder, and amino-silane coupling agent were not added. In the hybrid fibers of Example 12, carbon nanotubes and graphene oxide were not added. In the hybrid fibers of Example 13, nano-silica powder and amino-silane coupling agent were not added. Compared with Example 1, the 7-day and 28-day compressive strengths and fracture toughness of the concrete were significantly reduced. Moreover, the chloride ion diffusion coefficient and water penetration depth of the concrete were significantly increased. This shows that the addition of carbon nanotubes can significantly enhance the mechanical properties and impermeability of concrete, especially the compressive strength and fracture toughness. The high rigidity and good dispersion performance of carbon nanotubes can significantly improve the crack resistance of concrete. Graphene can significantly improve the impermeability of concrete, while increasing its crack resistance and compressive strength. In particular, the combination of nano-graphene with other fibers can produce a synergistic strengthening effect. Nano-silica powder can fill the fine pores of concrete, improve the density, and thus significantly enhance the impermeability and compressive strength. It is used to improve the adhesion between the fiber and the cement matrix, enhance the bonding force between the fiber and the matrix, and improve the overall mechanical properties of the concrete.

[0149] From Examples 1, 6, and 7, it can be seen that the ratio of modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano-silica powder, and amino-silane coupling agent in the hybrid fibers can affect the mechanical and impermeability properties of concrete. Among them, the addition of graphene and carbon nanotubes can enhance the crack resistance and impermeability of concrete, while polyphenylene sulfide fibers and polytetrafluoroethylene fibers further improve the toughness and durability of concrete. Nano-silica powder and mineralized graphene fillers not only help to improve the impermeability of concrete, but also fill the fine pores in the concrete, reduce the porosity, thereby improving the density and enhancing its compressive strength. The amino-silane coupling agent effectively improves the bonding force between the fiber and the cement matrix, ensuring the dispersion and stability of these reinforcing fibers in the concrete. Through the optimized design of the composite material, using the synergistic effect of polyphenylene sulfide nanofibers, carbon nanotubes, graphene, polytetrafluoroethylene fibers, and nano-silica powder, the impermeability, waterproof performance, and mechanical strength of concrete can be significantly improved. These fibers and fillers can not only improve the microstructure of concrete, but also provide better adhesion and dispersion, thus enhancing the overall performance of concrete.

[0150] It can be seen from Examples 1, 14 - 15 and in combination with the data in Table 2 that during the modification process of the modified polyphenylene sulfide nanofibers, for the preparation methods of Preparation Examples 2 - 11, the ultrasonic time of 60 min, the addition amount of 60 ml of tetraethyl orthosilicate, the dropping rate of tetraethyl orthosilicate of 3 drops / second, the addition amount of 30 ml of ammonia water, and the microwave radiation time of 10 s result in the best modification effect of the prepared modified polyphenylene sulfide nanofibers. When applied to concrete aggregates, the compressive strength and fracture toughness of the prepared concrete both increase significantly, while the drying shrinkage value, chloride ion diffusion coefficient, water penetration depth, and cracking area all decrease significantly. It is possible that under the process parameters of Preparation Examples 2 - 11, nano-silica and carbon nanotubes can grow uniformly on the surface of the polyphenylene sulfide nanofibers, achieving the best mechanical properties and shrinkage reduction effect for the concrete.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application. Those of ordinary skill in the art should understand that although the present application has been described in detail with reference to the foregoing embodiments, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions in the various embodiments of the present application.

Claims

1. A concrete aggregate based on modified coal gangue, characterized in that: The invention comprises the following components in parts by weight: 35-40 parts of slag, 5-9 parts of nano-alumina, 80-100 parts of red mud, 10-20 parts of fly ash, 80-100 parts of modified coal gangue, and 10-15 parts of mixed fibers; Wherein, the preparation method of modified coal gangue comprises the following steps: The coal gangue is ground into powder by ball milling and then sieved with a 150-mesh standard sieve to obtain fine coal gangue powder; The gangue powder is soaked in a sulfuric acid solution with a concentration of 40-50%, the slag and liquid are separated, the soaked gangue slag is dried, and then soaked in an ammonia solution with a concentration of 25-30%, the slag and liquid are separated, and dried to obtain a once-treated gangue; A titanate coupling agent solution with a concentration of 10-12% is prepared by using ethanol, and the primary treated coal gangue is immersed in the solution, and the immersion time is controlled to be 45-60 minutes. The coal gangue is taken out, and washed with distilled water for 2-3 times, and dried to obtain the secondary treated coal gangue; Dissolve polyvinyl alcohol in deionized water to form a 10% polyvinyl alcohol solution, mix the secondary treated coal gangue with the polyvinyl alcohol solution, add methyl acrylate and an initiator, stir evenly, heat to 80°C, react for 1-2 hours, cool the slag and liquid to separate, and dry to obtain modified coal gangue; the weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is (1-10):(0.5-3):(0.2-1):(0.005-0.05).

2. The concrete aggregate according to claim 1, characterized in that: The weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is (5-10):(1-2):(0.5-1):(0.02-0.05).

3. The concrete aggregate according to claim 2, characterized in that: The weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is 5:1:0.5:0.

02.

4. The concrete aggregate according to any one of claims 1 to 3, characterized in that: The hybrid fiber comprises modified polyphenylene sulfide nanofibers, carbon nanotubes, graphene oxide, polytetrafluoroethylene fibers, nano silicon powder and aminosilane coupling agent in a weight ratio of (30-40): (5-10): (2-5): (10-15): (15-20): (2-4).

5. The concrete aggregate according to claim 4, characterized in that: The hybrid fiber is prepared by the following method: A 3% aminosilane coupling agent solution is prepared by using distilled water, and the modified polyphenylene sulfide nanofiber and polytetrafluoroethylene fiber are mixed in ethanol or distilled water according to a predetermined ratio, and then added into the 3% aminosilane coupling agent solution; According to a predetermined ratio, carbon nanotubes, graphene oxide and nano silicon powder are added to an aminosilane coupling agent solution, and ultrasonically treated for 30-60 minutes. After suction filtration, washing and drying, hybrid fibers are obtained.

6. The concrete aggregate according to claim 4, characterized in that: The modified polyphenylene sulfide nanofiber preparation method comprises the following steps: 10 g of polyphenylene sulfide nanofibers were added to a nitric acid solution with a concentration of 10-18%, stirred for 1-3 hours, washed with water, immersed in anhydrous ethanol, soaked for 1-2 hours, dried with a vacuum filter, and dried at 70° C. for 3 hours to obtain dry polyphenylene sulfide nanofibers; The polyphenylene sulfide nanofibers were immersed in a 3wt.% silane coupling agent aqueous solution, heated to 70°C and kept at this temperature for 2 hours, cooled to room temperature and then dried with a vacuum filter, washed with ethanol for 3 times, and dried in an oven at 75°C to obtain polyphenylene sulfide nanofibers loaded with silane coupling agent; The polyphenylene sulfide nanofibers loaded with the silane coupling agent are placed in 1000 ml of ethanol solvent, 1 wt.% of hexadecyltrimethylammonium chloride is added, and stirred evenly to obtain a polyphenylene sulfide nanofiber mixture; Add 30-40 ml of ammonia water as a catalyst to the polyphenylene sulfide nanofiber mixture, disperse it by ultrasonication for 30-60 min, then add 60-80 ml of ethyl orthosilicate dropwise to the mixture under stirring, and stir and react at a constant temperature of 45° C. for 12 h to obtain polyphenylene sulfide nanofibers with nano-silica coated on the surface, take out the polyphenylene sulfide nanofibers with nano-silica coated on the surface from the solution, drain them with a vacuum filter, wash them with methanol three times, and dry them in an oven at 75° C. for 12 h; The polyphenylene sulfide nanofibers coated with nano-silica are evenly mixed with 0.1-0.5g of ferrocene, the obtained mixture is poured into a crucible and placed in a microwave oven, microwaved for 10-15s, and then cooled to room temperature to obtain modified polyphenylene sulfide nanofibers coated with nano-silica and carbon nanotubes.

7. The concrete aggregate according to claim 6, characterized in that: The ratio of the tetraethyl orthosilicate, ammonia water and ferrocene is 60-80 ml: 30-40 ml: 0.1-0.5 g.

8. The concrete aggregate according to claim 7, characterized in that: The ratio of the tetraethyl orthosilicate, ammonia water and ferrocene is 60ml:30ml:0.1g.

9. A method for preparing concrete aggregate according to any one of claims 1 to 8, characterized in that: The following steps are involved: 35-40 parts of slag, 5-9 parts of nano-alumina, 80-100 parts of red mud, 10-20 parts of fly ash, 80-100 parts of modified coal gangue, and 10-15 parts of mixed fibers are mixed uniformly to obtain concrete aggregate; Wherein, the preparation method of modified coal gangue comprises the following steps: The coal gangue is ground into powder by ball milling and then sieved with a 150-mesh standard sieve to obtain fine coal gangue powder; The gangue powder is soaked in a sulfuric acid solution with a concentration of 40-50%, the slag and liquid are separated, the soaked gangue slag is dried, and then soaked in an ammonia solution with a concentration of 25-30%, the slag and liquid are separated, and dried to obtain a once-treated gangue; A titanate coupling agent solution with a concentration of 10-12% is prepared by using ethanol, and the primary treated coal gangue is immersed in the solution, and the immersion time is controlled to be 45-60 minutes. The coal gangue is taken out, and washed with distilled water for 2-3 times, and dried to obtain the secondary treated coal gangue; Dissolve polyvinyl alcohol in deionized water to form a 10% polyvinyl alcohol solution, mix the secondary treated coal gangue with the polyvinyl alcohol solution, add methyl acrylate and an initiator, stir evenly, heat to 80°C, react for 1-2 hours, cool the slag and liquid to separate, and dry to obtain modified coal gangue; the weight ratio of the secondary treated coal gangue, polyvinyl alcohol, methyl acrylate and initiator in the modified coal gangue is (1-10):(0.5-3):(0.2-1):(0.005-0.05).

10. Use of the concrete aggregate according to any one of claims 1 to 8 in concrete.

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