Method for recycling construction waste, recycled material

Abstract

The application relates to a construction waste recycling method and a recycled material, and relates to the field of construction waste recycling. The construction waste recycling method comprises the following steps: pretreating construction waste to obtain first construction waste particles with a particle size of 5-10 mm; performing oxygen-rich microwave plasma treatment on the first construction waste particles to obtain second construction waste particles; and performing multistage gradient pressure immersion treatment on the second construction waste particles in a modified liquid, and drying to obtain recycled aggregates. Compared with the prior art, the application mainly combines the oxygen-rich microwave plasma process with the multistage gradient pressure immersion treatment technology of the specific modified liquid, realizes physical-chemical synergistic modification and activation of the construction waste, significantly reduces the void ratio and water absorption of the obtained recycled aggregates, can meet the use requirements of recycled materials such as concrete, provides a new technical means for construction waste recycling, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of construction waste recycling, and more particularly to a method for recycling and regenerating construction waste and recycled materials. Background Technology

[0002] With the acceleration of urbanization and the large-scale development of infrastructure construction, the construction industry is booming, and at the same time, the amount of construction waste generated is also increasing daily. Construction waste mainly includes waste concrete, bricks, rubble, wood, steel, and various decoration wastes, with waste concrete accounting for a considerable proportion. If this construction waste is not properly disposed of, it will not only occupy a large amount of valuable land resources, but also cause serious pollution to environmental elements such as soil, water sources, and air, affecting ecological balance and human health.

[0003] Currently, common physical treatment methods for construction waste mainly include crushing, washing, screening, and magnetic separation. However, the recycled aggregate obtained after these conventional physical treatments has problems such as microcracks on its surface, numerous pores, and high water absorption. As a result, when this recycled aggregate is used to prepare recycled materials such as concrete, it will significantly reduce the mechanical properties and durability of the recycled materials, making it difficult to meet the material performance requirements of actual engineering projects. Summary of the Invention

[0004] To address the above problems, this invention provides a method for recycling and regenerating construction waste, as well as recycled materials.

[0005] Firstly, the present invention provides a method for recycling and regenerating construction waste, such as... Figure 1 As shown, it includes the following steps:

[0006] Construction waste is pre-treated to obtain first construction waste particles with a particle size of 5-10mm;

[0007] The first construction waste particles were subjected to oxygen-enriched microwave plasma treatment to obtain the second construction waste particles.

[0008] The second type of construction waste particles were placed in a modified liquid for multi-stage gradient pressure impregnation treatment and dried to obtain recycled aggregate.

[0009] The modified liquid comprises the following components: silane coupling agent and nano-silica sol;

[0010] The silane coupling agent is composed of an aminosilane coupling agent and a fluorinated silane coupling agent in a weight ratio of (77-89):(11-23).

[0011] Furthermore, the pretreatment steps include crushing, washing, drying, magnetic separation, and sieving.

[0012] Furthermore, the working conditions parameters of the oxygen-enriched microwave plasma treatment include: microwave power of 580W-620W, time of 1min-3min, and the working medium is composed of oxygen and nitrogen in a volume ratio of (5-10):1.

[0013] Further, the step of placing the second construction waste particles in a modified liquid for multi-stage gradient pressure impregnation to obtain the second construction waste particles includes the following processes:

[0014] The nano-silica sol and the silane coupling agent were added to ethanol and stirred at room temperature. The pH was then adjusted to 8.8-9.5 to obtain the modified solution.

[0015] The second construction waste particles were added to the modified liquid at a temperature of 50℃-55℃ and heated and stirred for 25min-35min. Then, they were subjected to multi-stage gradient pressure impregnation treatment under room temperature and continuous stirring conditions to separate the second construction waste particles.

[0016] The multi-level gradient pressure impregnation process includes, in sequence:

[0017] Hold the pressure at -0.02MPa to -0.06MPa for 3-7 minutes;

[0018] Hold the pressure at 0.2MPa to 0.5MPa for 20-30 minutes;

[0019] Hold the pressure at 0.8 MPa to 1.2 MPa for 8 to 15 minutes.

[0020] Hold the pressure at 0.09 MPa to 0.11 MPa for 20-30 minutes.

[0021] Further, the weight ratio of the nano-silica sol, the silane coupling agent, and the ethanol is (25-30):(1-3):(5-10).

[0022] The nano-silica sol meets the following conditions: the silica mass percentage content is 20%-40%, and the dispersion medium is water;

[0023] The fluorinated silane coupling agent has a perfluorocarbon chain with 6-10 carbon atoms.

[0024] Furthermore, the aminosilane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane, and the fluorinated silane coupling agent includes at least one of perfluorohexyltriethoxysilane, perfluorohexyltrimethoxysilane, perfluorooctyltriethoxysilane, perfluorooctyltrimethoxysilane, perfluorodecyltriethoxysilane, and perfluorodecyltrimethoxysilane.

[0025] Furthermore, the construction waste includes waste concrete.

[0026] Secondly, based on the same inventive concept, the present invention provides a recycled material, which includes recycled aggregate obtained by the method of recycling and regenerating construction waste as described in the first aspect.

[0027] Further, by weight, the recycled material comprises the following components:

[0028] 375-390 parts cement, 50-60 parts fly ash, 20-25 parts mineral powder, 720-730 parts river sand, 1150-1160 parts of the aforementioned recycled aggregate, 4.5-6 parts water-reducing agent, 5-8 parts reinforcing fiber, and 160-170 parts water.

[0029] The reinforcing fiber includes at least one of steel fiber, polypropylene fiber, and basalt fiber.

[0030] Furthermore, the reinforcing fiber is composed of basalt fiber, polypropylene fiber and steel fiber in a weight ratio of (5-8):(1-2):(1-2).

[0031] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art:

[0032] This invention provides a method and recycled materials for the recycling of construction waste. Compared to existing technologies, this invention primarily utilizes a multi-stage gradient pressure impregnation process combined with an oxygen-enriched microwave plasma process and the introduction of a specific modifying liquid. This achieves synergistic physical-chemical modification and activation of construction waste, significantly reducing the porosity and water absorption rate of the resulting recycled aggregate. This meets the requirements for use in recycled materials such as concrete, providing a new technical means for the recycling of construction waste with broad application prospects. Specifically:

[0033] On the one hand, this invention employs an oxygen-enriched microwave plasma process to activate construction waste particles, which not only enhances their surface reactivity and expands the effective contact area but also facilitates subsequent adsorption and chemical bonding of the modified liquid. On the other hand, this invention utilizes a suitable ratio of aminosilane coupling agents, fluorinated silane coupling agents, and nano-silica sol to strengthen interfacial adhesion and improve hydrophobicity. Combined with a multi-stage gradient pressure impregnation technology (mainly including a negative pressure vacuum degassing stage, a low-pressure permeation stage, a high-pressure filling stage, and a normal-pressure capillary adsorption stage), it achieves effective in-situ filling of the modified liquid. The synergistic effect of each step significantly reduces the porosity and water absorption rate of recycled construction waste aggregates, providing an efficient and environmentally friendly technical path for the resource utilization of construction waste. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a process flow diagram of a method for recycling and regenerating construction waste provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. For example, construction waste, silane coupling agents, nano-silica sol (such as alkaline nano-silica sol with a silica mass percentage of 30%), and reinforcing fibers (basalt fiber, polypropylene fiber, and steel fiber, 15-20 mm in length) can all be directly sourced from commercially available products or prepared using existing methods. Furthermore, the steps and parameters involved in pretreatment processes such as crushing, washing, drying, magnetic separation, and sieving in this invention, unless otherwise specified or defined, can be carried out according to the existing methods for recycling and regenerating construction waste or directly using existing equipment; these will not be elaborated upon in this application.

[0039] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed according to national standards such as GB / T 14685-2022 and GB / T 25177-2010. If no corresponding national standard exists, general international standards, conventional conditions, or conditions recommended by the manufacturer shall be followed.

[0040] Example 1

[0041] This example provides a method for recycling and regenerating construction waste, including the following steps:

[0042] S1: The construction waste (specifically waste concrete) is crushed, washed, dried, magnetically separated, and screened to obtain the first construction waste particles with a particle size of 5-10mm.

[0043] S2: The first construction waste particles are subjected to oxygen-enriched microwave plasma treatment with a microwave power of 600W and a time of 2min. The working medium is composed of oxygen and nitrogen in a volume ratio of 8:1, and the discharge mode is glow discharge to obtain the second construction waste particles.

[0044] S3: A nano-silica sol with a silica mass percentage of 30% and water as the dispersion medium, a silane coupling agent (specifically composed of γ-aminopropyltriethoxysilane and perfluorooctyltriethoxysilane in a weight ratio of 83:17), and ethanol were stirred at room temperature for 15 min, and then the pH was adjusted to 9.2 to obtain a modified solution. The second construction waste particles were added to the modified solution at 52°C and heated and stirred for 30 min. Then, a multi-stage gradient pressure impregnation treatment was carried out under room temperature and continuous stirring: pressure of -0.04 MPa for 5 min; pressure of 0.3 MPa for 25 min; pressure of 1.0 MPa for 12 min; pressure of 0.1 MPa for 25 min; after separation, the mixture was dried at 110°C for 2 h to obtain recycled aggregate.

[0045] Example 2

[0046] This example provides a method for recycling and regenerating construction waste, including the following steps:

[0047] S1: The construction waste (specifically waste concrete) is crushed, washed, dried, magnetically separated, and screened to obtain the first construction waste particles with a particle size of 5-10mm.

[0048] S2: The first construction waste particles are subjected to oxygen-enriched microwave plasma treatment with a microwave power of 580W and a time of 3min. The working medium is composed of oxygen and nitrogen in a volume ratio of 5:1, and the discharge mode is glow discharge to obtain the second construction waste particles.

[0049] S3: Nano-silica sol with a silica mass percentage of 30% and water as the dispersion medium, a silane coupling agent (specifically composed of γ-aminopropyltrimethoxysilane and perfluorohexyltriethoxysilane in a weight ratio of 77:23), and ethanol are stirred at room temperature for 15 min in a weight ratio of 25:1:5. The pH is then adjusted to 9.2 to obtain a modified solution. The second construction waste particles are added to the modified solution at 52°C and heated and stirred for 30 min. Then, a multi-stage gradient pressure impregnation treatment is performed under room temperature and continuous stirring: pressure at -0.06 MPa for 3 min; pressure at 0.2 MPa for 30 min; pressure at 1.2 MPa for 8 min; pressure at 0.1 MPa for 20 min. After separation, the mixture is dried at 110°C for 2 h to obtain recycled aggregate.

[0050] Example 3

[0051] This example provides a method for recycling and regenerating construction waste, including the following steps:

[0052] S1: The construction waste (specifically waste concrete) is crushed, washed, dried, magnetically separated, and screened to obtain the first construction waste particles with a particle size of 5-10mm.

[0053] S2: The first construction waste particles are subjected to oxygen-enriched microwave plasma treatment with a microwave power of 620W and a time of 1min. The working medium is composed of oxygen and nitrogen in a volume ratio of 10:1, and the discharge mode is glow discharge to obtain the second construction waste particles.

[0054] S3: Nano-silica sol with a silica mass percentage of 30% and water as the dispersion medium, a silane coupling agent (specifically composed of γ-aminopropyltriethoxysilane and perfluorodecyltrimethoxysilane in a weight ratio of 89:11), and ethanol are stirred at room temperature for 15 min, and then the pH is adjusted to 9.2 to obtain a modified solution. The second construction waste particles are added to the modified solution at 52°C and heated and stirred for 30 min. Then, a multi-stage gradient pressure impregnation treatment is performed under room temperature and continuous stirring: pressure at -0.02 MPa for 7 min; pressure at 0.5 MPa for 20 min; pressure at 0.9 MPa for 15 min; pressure at 0.1 MPa for 30 min; after separation, the mixture is dried at 110°C for 2 h to obtain recycled aggregate.

[0055] Example 4

[0056] This example provides a recycled material comprising, by weight, the following components: 382 parts cement, 54 parts fly ash, 22 parts S95 grade mineral powder, 726 parts river sand, 1157 parts recycled aggregate obtained in Example 1, 5.5 parts polycarboxylate superplasticizer, 6.8 parts reinforcing fiber (specifically steel fiber), and 166 parts water; wherein the reinforcing fiber is steel fiber.

[0057] Example 5

[0058] This example provides a recycled material, which differs from Example 4 in that the reinforcing fiber is composed of basalt fiber, polypropylene fiber and steel fiber in a weight ratio of 7:1:2.

[0059] Comparative Example 1

[0060] This example provides a method for recycling and regenerating construction waste, which differs from Example 1 in that it does not involve oxygen-enriched microwave plasma treatment.

[0061] The above-mentioned method for recycling and regenerating construction waste includes the following steps:

[0062] S1: The construction waste (specifically waste concrete) is crushed, washed, dried, magnetically separated, and screened to obtain the first construction waste particles with a particle size of 5-10mm.

[0063] S2: A nano-silica sol with a silica mass percentage of 30% and water as the dispersion medium, a silane coupling agent (specifically composed of γ-aminopropyltriethoxysilane and perfluorooctyltriethoxysilane in a weight ratio of 83:17), and ethanol were stirred at room temperature for 15 min, and then the pH was adjusted to 9.2 to obtain a modified solution. The first construction waste particles were added to the modified solution at 52°C and heated and stirred for 30 min. Then, a multi-stage gradient pressure impregnation treatment was performed under room temperature and continuous stirring: pressure of -0.04 MPa for 5 min; pressure of 0.3 MPa for 25 min; pressure of 1.0 MPa for 12 min; pressure of 0.1 MPa for 25 min; after separation, the mixture was dried at 110°C for 2 h to obtain recycled aggregate.

[0064] Comparative Example 2

[0065] This example provides a method for recycling and regenerating construction waste, which differs from Example 1 in that the multi-stage gradient pressure impregnation treatment in Example 1 is replaced with conventional soaking treatment.

[0066] The above-mentioned method for recycling and regenerating construction waste includes the following steps:

[0067] S1: The construction waste (specifically waste concrete) is crushed, washed, dried, magnetically separated, and screened to obtain the first construction waste particles with a particle size of 5-10mm.

[0068] S2: The first construction waste particles are subjected to oxygen-enriched microwave plasma treatment with a microwave power of 600W and a time of 2min. The working medium is composed of oxygen and nitrogen in a volume ratio of 8:1, and the discharge mode is glow discharge to obtain the second construction waste particles.

[0069] S3: Nano-silica sol with a silica mass percentage of 30% and water as the dispersion medium, a silane coupling agent (specifically composed of γ-aminopropyltriethoxysilane and perfluorooctyltriethoxysilane in a weight ratio of 83:17), and ethanol are stirred at room temperature for 15 min in a weight ratio of 27:2:8. The pH is then adjusted to 9.2 to obtain a modified solution. The second construction waste particles are added to the modified solution at 52°C and heated and stirred for 30 min. Then, they are impregnated at room temperature and under continuous stirring for 67 min under normal pressure. After separation, they are dried at 110°C for 2 h to obtain recycled aggregate.

[0070] Comparative Example 3

[0071] This example provides a method for recycling and regenerating construction waste. The difference from Example 1 is that the silane coupling agent in Example 1 is adjusted to be composed of γ-aminopropyltriethoxysilane and perfluorooctyltriethoxysilane in a weight ratio of 50:50 (i.e., the amount of fluorinated silane coupling agent added is relatively excessive).

[0072] Comparative Example 4

[0073] This example provides a method for recycling and regenerating construction waste, which differs from Example 1 in that:

[0074] (1) The silane coupling agent in Example 1 was adjusted to be composed of γ-aminopropyltriethoxysilane and n-octadecyltriethoxysilane in a weight ratio of 50:50 (i.e., the composition and compounding ratio of the silane coupling agent were adjusted, a non-fluorinated silane coupling agent was used, and the carbon chain was too long).

[0075] Test Example 1

[0076] In this example, the void ratio (%) and water absorption rate (%) of the recycled aggregate obtained by the construction waste recycling method provided in the above embodiments and comparative examples are tested, and the recycled aggregate obtained by conventional physical recycling (i.e., the first construction waste particles obtained in S1 in Example 1) is used as the basic control. The test results are shown in Table 1.

[0077] Table 1. Test results of porosity (%) and water absorption (%) of recycled aggregate.

[0078]

[0079] As shown in Table 1, compared with the recycled aggregate obtained by conventional physical recycling and Comparative Examples 1-4, the recycled aggregate obtained by the construction waste recycling method provided in this embodiment of the invention has significantly reduced porosity and water absorption rate, meeting the requirements for use as recycled materials such as concrete.

[0080] Test Example 2

[0081] Based on the above test example 1, this test example tests the mechanical properties (28-day compressive strength, MPa) and freeze-thaw cycle resistance (compressive strength retention rate, %) of the recycled concrete materials obtained in examples 4 and 5. The test results are shown in Table 2.

[0082] Table 2. Test results of mechanical properties and freeze-thaw cycle resistance of recycled concrete materials.

[0083]

[0084] As shown in Table 2, the recycled materials made from the recycled aggregates obtained in the embodiments of the present invention have excellent mechanical properties and freeze-thaw cycle resistance. Furthermore, the material properties can be further improved by optimizing the reinforcing components; for example, introducing appropriate proportions of basalt fiber, polypropylene fiber, and steel fiber can significantly improve the freeze-thaw cycle resistance of the resulting material.

[0085] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0086] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for recycling and regenerating construction waste, characterized in that, Includes the following steps: Construction waste is pre-treated to obtain first construction waste particles with a particle size of 5-10mm; The first construction waste particles were subjected to oxygen-enriched microwave plasma treatment to obtain the second construction waste particles. The second type of construction waste particles are placed in a modified liquid for multi-stage gradient pressure impregnation treatment and then dried to obtain recycled aggregate. The modified liquid comprises the following components: silane coupling agent and nano-silica sol; The silane coupling agent is composed of an aminosilane coupling agent and a fluorinated silane coupling agent in a weight ratio of (77-89):(11-23).

2. The method for recycling and regenerating construction waste according to claim 1, characterized in that, The pretreatment steps include crushing, washing, drying, magnetic separation, and sieving.

3. The method for recycling and regenerating construction waste according to claim 1, characterized in that, The working conditions parameters for the oxygen-enriched microwave plasma treatment include: microwave power of 580W-620W, time of 1min-3min, and working medium composed of oxygen and nitrogen in a volume ratio of (5-10):

1.

4. The method for recycling and regenerating construction waste according to claim 1, characterized in that, The steps of placing the second construction waste particles in a modified liquid for multi-stage gradient pressure impregnation to obtain the second construction waste particles include the following processes: The nano-silica sol and the silane coupling agent were added to ethanol and stirred at room temperature. The pH was then adjusted to 8.8-9.5 to obtain the modified solution. The second construction waste particles were added to the modified liquid at a temperature of 50℃-55℃ and heated and stirred for 25min-35min. Then, they were subjected to multi-stage gradient pressure impregnation treatment under room temperature and continuous stirring conditions to separate the second construction waste particles. The multi-level gradient pressure impregnation process includes, in sequence: Hold the pressure at -0.02MPa to -0.06MPa for 3-7 minutes; Hold the pressure at 0.2MPa to 0.5MPa for 20-30 minutes; Hold the pressure at 0.8 MPa to 1.2 MPa for 8 to 15 minutes. Hold the pressure at 0.09 MPa to 0.11 MPa for 20-30 minutes.

5. The method for recycling and regenerating construction waste according to claim 4, characterized in that, The weight ratio of the nano-silica sol, the silane coupling agent, and the ethanol is (25-30):(1-3):(5-10). The nano-silica sol meets the following conditions: the silica mass percentage content is 20%-40%, and the dispersion medium is water; The fluorinated silane coupling agent has a perfluorocarbon chain with 6-10 carbon atoms.

6. The method for recycling and regenerating construction waste according to claim 4, characterized in that, The aminosilane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane, and the fluorinated silane coupling agent includes at least one of perfluorohexyltriethoxysilane, perfluorohexyltrimethoxysilane, perfluorooctyltriethoxysilane, perfluorooctyltrimethoxysilane, perfluorodecyltriethoxysilane, and perfluorodecyltrimethoxysilane.

7. The method for recycling and regenerating construction waste according to any one of claims 1-6, characterized in that, The construction waste includes waste concrete.

8. A recycled material, characterized in that, The recycled material includes recycled aggregates obtained by the method of recycling and regenerating construction waste according to any one of claims 1-7.

9. The recycled material according to claim 8, characterized in that, The recycled material comprises the following components in parts by weight: 375-390 parts cement, 50-60 parts fly ash, 20-25 parts mineral powder, 720-730 parts river sand, 1150-1160 parts of the aforementioned recycled aggregate, 4.5-6 parts water-reducing agent, 5-8 parts reinforcing fiber, and 160-170 parts water. The reinforcing fiber includes at least one of steel fiber, polypropylene fiber, and basalt fiber.

10. The recycled material according to claim 9, characterized in that, The reinforcing fiber is composed of basalt fiber, polypropylene fiber and steel fiber in a weight ratio of (5-8):(1-2):(1-2).

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