Construction waste self-reinforced recycled aggregate preparation method and prepared recycled aggregate

Abstract

The application discloses a kind of building waste self-reinforced recycled aggregate preparation methods, comprising the following steps: (1), the building waste containing red brick and hardened cement paste is crushed, and red brick material and the block of hardened cement paste containing are separated out;(2), red brick material is mixed with the solution containing carboxyl ether and is ground, and the modified slurry containing nanoscale red brick particle material is obtained;(3), the block of hardened cement paste containing separated out is immersed in modified slurry, after immersion is completed, the block of hardened cement paste containing is taken out and is dried, and building waste self-reinforced recycled aggregate is obtained;In the solution containing carboxyl ether, solvent is water, and the concentration of carboxyl ether is 0.1-0.8mol / L;The particle size range of nanoscale red brick particle material is 50-200nm;During the process of immersion, the mixture is heated and stirred, and the heating temperature is 40-80 DEG C.The method can prepare building waste self-reinforced recycled aggregate with high strength and low water absorption.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a method for preparing self-reinforced recycled aggregate from construction waste and the resulting recycled aggregate. Background Technology

[0002] Construction waste in suburban areas typically contains red bricks and large amounts of low-grade mortar and concrete, generally referring to mortar and concrete with strength grades between M5 and M10. Low-grade mortar and concrete have high porosity and large pore size, resulting in exceptionally high water absorption, which severely impacts their strength when used as aggregate in recycled concrete. Red bricks primarily contain oxides such as silicon dioxide (SiO2), aluminum oxide (Al2O3), iron oxide (Fe2O3), and magnesium oxide (MgO). The proportion of these oxides and the presence of other materials can affect the specific color and texture of the red bricks. Furthermore, aggregates made from demolition materials like red bricks suffer from high porosity, high water absorption, and exceptionally high crushing indices, limiting their application in concrete. Therefore, in current technologies, cement blocks and red bricks from construction waste concrete are unsuitable for direct production of recycled aggregates; their processing remains limited to simple stockpiling and landfilling, resulting in low resource recovery and reuse rates. Summary of the Invention

[0003] One technical problem to be solved by the present invention is to provide a method for preparing self-reinforced recycled aggregate from construction waste that can produce recycled aggregate with high strength and low water absorption.

[0004] One technical solution of the present invention is to provide a method for preparing self-reinforced recycled aggregate from construction waste, comprising the following steps:

[0005] (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste.

[0006] (2) Mix and grind the red brick material with a solution containing carboxyl ether to obtain a modified slurry containing nano-sized red brick particles.

[0007] (3) The separated block containing hardened cement paste is immersed in modified mud. After immersion, the block containing hardened cement paste is removed and dried to obtain self-reinforced recycled aggregate from construction waste.

[0008] After adopting the above steps, the method for preparing self-reinforced recycled aggregate from construction waste of the present invention has the following advantages:

[0009] After separation, construction waste yields red brick material and hardened cement slurry material. The red brick material is mixed and ground with a solution containing carboxyl ethers to produce modified slurry containing nano-sized red brick particles. During the grinding process to produce the modified slurry, the carboxyl ethers in the solution help to better suspend the nano-sized red brick particles. When the blocks containing hardened cement slurry are immersed in the modified slurry, the presence of ether groups in the modified slurry reduces the surface tension of the blocks, allowing a large amount of nano-sized red brick particles and carboxyl ethers to enter the pores or cracks of the blocks containing hardened cement slurry. The carboxyl ethers that enter the pores or cracks hydrolyze to produce carboxyl groups. These carboxyl groups can dissolve magnesium (Mg) and iron (Fe) from the nano-sized red brick particles in the pores or cracks, forming ions. Some carboxyl groups are grafted onto the inner surface of the pores or cracks and remain in the pores or cracks. After drying, as the self-reinforced recycled aggregate from construction waste gradually loses moisture, Mg ions crystallize inside the pores or cracks to form an interwoven magnesium hydroxide plate-like crystal structure, i.e., Mg(OH)2 plate-like crystal structure. This structure fills and supports the pores or cracks and refines the pore structure, thereby strengthening the self-reinforced recycled aggregate from construction waste and significantly reducing the water absorption rate of the recycled aggregate. This allows for the preparation of self-reinforced recycled aggregate from construction waste with high strength and low water absorption.

[0010] When the self-reinforced recycled aggregate from construction waste is applied to concrete, on the one hand, cement dissolves a large amount of calcium ions when it comes into contact with water, and on the surface of the pores or cracks of the recycled aggregate, there are a large number of carboxyl anions, namely -COO. - This causes the nano-sized red brick particles that penetrate into pores or cracks to become negatively charged in the solid phase, enabling the formation of positive trivalent iron ions, i.e., Fe. 3 + and calcium ions, i.e., Ca 2 + Due to electrical effects, Fe is deposited on the solid surface of nano-sized red brick particles. 3 + ions and Ca 2 The process induces and accelerates the formation of hydration products such as hydrated calcium silicate and hydrated calcium aluminate on the solid surface of nano-sized red brick particles. On the other hand, Mg ions in the pores or cracks can further induce calcium carbonate crystallization at the aggregate pores or cracks. The synergistic effect of these two factors further strengthens the self-reinforcing recycled construction waste aggregate. Furthermore, during the subsequent curing of cement concrete, the hydration products within the pores or cracks continue to grow and overflow from the aggregate pores or cracks. These growing and overflowing hydration products intertwine with the hydration products in the interface transition zone between the recycled aggregate and the cement matrix, acting as an anchoring agent between the recycled aggregate and the cement matrix, thereby improving the overall performance of the recycled aggregate concrete.

[0011] Furthermore, in step (2), the solvent in the solution containing carboxyl ether is water, and the concentration of carboxyl ether is 0.1-0.8 mol / L. By adopting the above steps, it is further ensured that the obtained slurry is a modified slurry containing nano-sized red brick particles.

[0012] Furthermore, in step (2), the particle size range of the nano-sized red brick particles is 50-200 nm. By employing the above steps, the blocky material containing hardened cement slurry is more thoroughly impregnated in the modified slurry, further ensuring the technical effect of forming Mg(OH)2 crystals in the pores or cracks of the blocky material containing hardened cement slurry.

[0013] Furthermore, in step (3), when the block containing hardened cement paste is impregnated in the modified slurry, the mixture is heated and stirred at a temperature of 40-80℃. By employing the above steps, the heating treatment during impregnation accelerates the entry of nano-sized red brick particles and carboxyl ethers into the pores or cracks of the block containing hardened cement paste, increasing the penetration amount. Moreover, it accelerates the hydrolysis and grafting of carboxyl ethers onto the inner surface of the aggregate pores or cracks, which is beneficial for the dissolution and transformation of Mg in the nano-sized red brick particles into ionic states, further ensuring the technical effect of forming Mg(OH)2 crystals in the pores or cracks of the block containing hardened cement paste.

[0014] Furthermore, in step (3), the lumps containing hardened cement slurry are immersed in the modified slurry for more than 30 minutes. By adopting the above steps, the lumps containing hardened cement slurry are more thoroughly immersed in the modified slurry, further ensuring that the nano-sized red brick particles and carboxyl ethers can penetrate into the pores or cracks, thus further guaranteeing the technical effect of forming Mg(OH)2 crystals in the pores or cracks of the lumps containing hardened cement slurry.

[0015] Furthermore, in step (3), the drying temperature is 50-80℃ and the drying time is 2-6 hours. By adopting the above steps, the drying degree of the self-reinforced recycled aggregate from construction waste is better, which is more conducive to the production of concrete. This further ensures the anchoring effect between the self-reinforced recycled aggregate from construction waste and the cement matrix, thereby achieving the technical effect of improving the overall performance of the self-reinforced recycled aggregate concrete from construction waste.

[0016] Another technical problem to be solved by the present invention is to provide a self-reinforced recycled aggregate from construction waste with high strength and low water absorption.

[0017] Another technical solution of the present invention is to provide a self-reinforced recycled aggregate from construction waste, which is prepared by the preparation method of self-reinforced recycled aggregate from construction waste described in any of the above technical solutions.

[0018] The self-reinforced recycled aggregate from construction waste of this invention has the following advantages: high strength and low water absorption. When this self-reinforced recycled aggregate from construction waste is used in concrete mixing, substances such as carboxylic ethers that penetrate into the aggregate can interact with the cement paste, filling pores and cracks, further strengthening the self-reinforced recycled aggregate from construction waste. Moreover, as the cement concrete cures, the hydration products within the pores or cracks continue to grow and overflow from the outside of the aggregate pores or cracks. The growing and overflowing hydration products intertwine with the hydration products in the interface transition zone of the cement aggregate, playing an anchoring role between the self-reinforced recycled aggregate from construction waste and the cement matrix, thereby improving the overall performance of the self-reinforced recycled aggregate concrete from construction waste.

[0019] Furthermore, the particle size range of the self-reinforced recycled aggregate from construction waste is 3-25mm. Within this particle size range, it is more suitable for the application of self-reinforced recycled aggregate from construction waste in concrete, thereby further improving the overall performance of concrete made with self-reinforced recycled aggregate from construction waste. Attached Figure Description

[0020] Figure 1 These are SEM images of self-reinforced recycled aggregates from construction waste in concrete from Examples 1, 2, and 3. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions of specific embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various specific embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The present invention discloses a method for preparing self-reinforced recycled aggregate from construction waste, comprising the following steps:

[0023] (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste.

[0024] (2) Mix and grind the red brick material with a solution containing carboxyl ether to obtain a modified slurry containing nano-sized red brick particles.

[0025] (3) The separated block containing hardened cement paste is immersed in modified mud. After immersion, the block containing hardened cement paste is removed and dried to obtain self-reinforced recycled aggregate from construction waste.

[0026] It's not hard to understand: self-reinforcing means that construction waste contains bricks and hardened cement paste lumps. These lumps are impregnated in slurry made from finely ground and modified bricks, thus strengthening the lumps. In other words, the construction waste itself strengthens the lumps, resulting in self-reinforcing recycled aggregate, hence the name "construction waste self-reinforcing recycled aggregate." Construction waste containing bricks and hardened cement paste refers to bricks and hardened cement paste after impurities such as reinforcing steel have been removed. Hardened cement paste lumps can also be called concrete lumps after removing reinforcing steel and impurities. Of course, these concrete lumps do not include natural aggregates in concrete, such as crushed stone and pebbles. "Modification" is a general term referring to methods that change the physical form or properties of materials through physical and chemical means. Here, it can be understood as mixing and grinding red brick materials with a solution containing carboxyl ethers to obtain slurry containing nano-sized red brick particles, which is thus considered modified slurry. The solution containing carboxyl ethers mentioned are commercially available solutions containing carboxyl ethers, such as commercially available polyethylene glycol dicarboxyl ether and commercially available ethylene glycol methyl ether acetate, the latter of which contains a carboxyl group in acetic acid. The term carboxyl ether can be understood as an organic compound containing a carboxyl functional group and an ether bond.

[0027] In step (2), the solvent in the solution containing carboxyl ether is water, and the concentration of carboxyl ether is preferably 0.1-0.8 mol / L.

[0028] In step (2), when the block containing hardened cement paste is impregnated in the modified mud, the mixture is heated and stirred, and the heating temperature is preferably 40-80℃.

[0029] In step (3), the lumps containing hardened cement paste are impregnated in the modified slurry for at least 30 minutes. 30 minutes is the lower limit, ensuring sufficient impregnation of the lumps containing hardened cement paste in the modified slurry, guaranteeing that the nano-sized red brick particles and carboxyl ethers can penetrate into the pores or cracks. There is no upper limit; that is, increasing the impregnation time further will not negatively impact the recycled aggregate. However, from the perspective of efficiency and saving heating costs, excessively long impregnation times will affect production efficiency and relatively increase heating costs. Therefore, 30-360 minutes, or 0.5 to 6 hours, can be considered the preferred range. This allows the nano-sized red brick particles and carboxyl ethers to fully penetrate into the pores or cracks while relatively improving production efficiency and relatively saving heating costs.

[0030] In step (3), the preferred particle size range of the nanoscale red brick microparticles is 50-200 nm.

[0031] In step (3), the drying temperature is preferably 50-80℃ and the drying time is preferably 2-6 hours.

[0032] The self-reinforced recycled aggregate from construction waste is prepared by the preparation method of self-reinforced recycled aggregate from construction waste described in any of the above technical solutions.

[0033] The preferred particle size range for the self-reinforced recycled aggregate from construction waste is 3-25 mm.

[0034] The present invention will be further described below with reference to specific embodiments:

[0035] Example 1

[0036] (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste.

[0037] (2) The red brick material is mixed and ground with a solution containing carboxyl ether. The particle size range of the nano-sized red brick particles obtained by grinding is 50 nm. Modified slurry containing nano-sized red brick particles is obtained. The solvent of the solution containing carboxyl ether is water, and the concentration of carboxyl ether is 0.2 mol / L. The solution containing carboxyl ether can be a solution containing polyethylene glycol dicarboxyl ether, and the concentration of polyethylene glycol dicarboxyl ether is 0.2 mol / L.

[0038] (3) The separated blocks containing hardened cement paste are immersed in modified mud for 1 hour, while the mixture is heated and stirred at 50°C. After immersion, the blocks containing hardened cement paste are removed and dried for 2 hours to obtain self-reinforced recycled aggregate from construction waste with a particle size of 5 mm.

[0039] Example 2

[0040] (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste.

[0041] (2) The red brick material is mixed and ground with a solution containing carboxyl ether. The particle size range of the nano-sized red brick particles obtained by grinding is 180 nm. Modified slurry containing nano-sized red brick particles is obtained. The solvent of the solution containing carboxyl ether is water, and the concentration of carboxyl ether is 0.8 mol / L. The solution containing carboxyl ether can be a solution containing ethylene glycol methyl ether acetate, and the concentration of ethylene glycol methyl ether acetate is 0.8 mol / L.

[0042] (3) The separated blocks containing hardened cement paste are impregnated in modified mud for 6 hours, while the mixture is heated and stirred at 70°C. After impregnation, the blocks containing hardened cement paste are removed and dried for 6 hours to obtain self-reinforced recycled aggregate from construction waste with a particle size of 23 mm.

[0043] Example 3

[0044] (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste.

[0045] (2) The red brick material is mixed and ground with a solution containing carboxyl ether. The particle size range of the nano-sized red brick particles obtained by grinding is 60 nm. Modified slurry containing nano-sized red brick particles is obtained. The solvent of the solution containing carboxyl ether is water, and the concentration of carboxyl ether is 0.4 mol / L. The solution containing carboxyl ether can be a solution containing polyethylene glycol dicarboxyl ether, and the concentration of polyethylene glycol dicarboxyl ether is 0.4 mol / L.

[0046] (3) The separated blocks containing hardened cement paste are impregnated in modified mud for 5 hours, while the mixture is heated and stirred at 60°C. After impregnation, the blocks containing hardened cement paste are removed and dried for 3 hours to obtain self-reinforced recycled aggregate from construction waste with a particle size of 15 mm.

[0047] As cement concrete cures, hydration products within pores or cracks continue to grow and overflow from the aggregate pores or cracks, such as... Figure 1 As shown, the hydration products that overflow during growth intertwine with the hydration products in the cement-aggregate interface transition zone, playing an anchoring role between the recycled aggregate and the cement matrix, thereby improving the overall performance of recycled aggregate concrete.

[0048] The self-reinforced recycled construction waste aggregate obtained in Example 3 above was subjected to crushing value and water absorption tests. These were compared with untreated block aggregate containing original hardened cement paste and natural crushed stone, and their crushing value and water absorption were also tested. Furthermore, C30 concrete specimens were prepared from these three aggregates according to the concrete mix design requirements, and the 28-day compressive strength of the concrete specimens was tested. The relevant test data are shown in the table below.

[0049] Table 1. Comparison of performance data of different aggregates and strength of concrete test blocks.

[0050]

[0051] The above test data shows that the nano-sized red brick particles obtained by treating construction waste with carboxylated ether solution, followed by modified slurry, can further strengthen the lumpy recycled aggregate containing hardened cement paste in the construction waste after impregnation in the modified slurry. This results in increased strength and significantly reduced water absorption of the lumpy recycled aggregate, achieving self-strengthening of the construction waste recycled aggregate during impregnation. In addition, the self-strengthening aggregate can also generate a secondary strengthening effect with the hydration products in the mixture, thus improving the overall performance of concrete using this self-reinforced construction waste recycled aggregate.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing self-reinforced recycled aggregate from construction waste, characterized in that, Includes the following steps: (1) The construction waste containing red bricks and hardened cement paste is crushed and separated into red brick materials and blocky materials containing hardened cement paste. (2) Mix and grind the red brick material with a solution containing carboxyl ether to obtain a modified slurry containing nano-sized red brick particles; (3) The separated blocky material containing hardened cement paste is immersed in modified mud. After immersion, the blocky material containing hardened cement paste is taken out and dried to obtain self-reinforced recycled aggregate from construction waste. In step (2), the solvent in the solution containing carboxyl ether is water, and the concentration of carboxyl ether is 0.1-0.8 mol / L; In step (3), when the block containing hardened cement paste is impregnated in the modified mud, the mixture is heated and stirred at a temperature of 40-80℃. In step (3), the block containing hardened cement paste is immersed in modified mud for 0.5-6 hours.

2. The method for preparing self-reinforced recycled aggregate from construction waste according to claim 1, characterized in that: In step (2), the particle size range of the nanoscale red brick microparticles is 50-200 nm.

3. The method for preparing self-reinforced recycled aggregate from construction waste according to claim 1, characterized in that: In step (3), the drying temperature is 50-80℃ and the drying time is 2-6 hours.

4. A self-reinforced recycled aggregate from construction waste, characterized in that: The self-reinforced recycled aggregate from construction waste is prepared by the method for preparing self-reinforced recycled aggregate from construction waste as described in any one of claims 1-3.

5. The recycled aggregate according to claim 4, characterized in that: The particle size range of the self-reinforced recycled aggregate from construction waste is 3-25mm.

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