Method for preparing footpath brick by recycling waste circuit board

Abstract

The invention relates to a method for preparing a footpath brick by recycling a waste circuit board, and belongs to the technical field of footpath brick preparation, and the method specifically comprises the following steps: S1, collecting the waste circuit board, removing metal components and wires, crushing and screening, and sorting to remove metal components to obtain non-metal powder; s2, mixing the non-metal powder, the building material components, the water reducing agent, the water reducing enhancer and other auxiliaries to obtain a mixture; and carrying out vibration compression molding on the mixture, and carrying out balance treatment on the molded green body to obtain the footpath brick prepared by recycling the waste circuit board. Wherein the water reducing and reinforcing agent is epoxy modified anionic polyacrylamide. Through interface bridging of the anionic polyacrylamide water-reducing enhancer, dispersion water-reducing of the lignosulfonate water-reducing agent and secondary hydration of the fly ash / slag, the problems of weak interface bonding between non-metal powder and cement and poor slurry fluidity are solved, and finally the regenerated footpath brick with high strength and good durability is prepared.

Description

Technical Field

[0001] The present application relates to the technical field of pavement brick preparation, and more specifically, to a method for preparing pavement bricks by recycling waste circuit boards. Background Art

[0002] With the rapid development of the electronic information industry, the amount of electronic waste generated has increased sharply. Among them, discarded circuit boards have become a key problem in the field of environmental governance because they contain heavy metals and difficult-to-degrade organic matter.

[0003] Existing technologies for utilizing non-metallic powder from scrap circuit boards face significant limitations. Firstly, due to their high surface inertness and complex pore structure, direct use of non-metallic powder as aggregate can lead to weak bonding with the cement matrix and numerous interfacial defects, resulting in low strength and poor durability. Secondly, traditional walkway brick production processes are not optimized for the properties of non-metallic powders. Simple blending alone cannot address the volume shrinkage caused by their high water absorption, and it is difficult to balance water permeability with mechanical properties. Furthermore, while conventional water-reducing agents (such as wood sulfonates) can improve workability, they suffer from rapid dispersibility degradation and poor compatibility with inert aggregates, further limiting the high-value utilization of non-metallic powders.

[0004] Therefore, developing a technology for preparing non-metallic powder-based walkway bricks from waste circuit boards that combines resource recycling with high performance is of great significance for promoting the upgrading of the electronic waste resource utilization industry and alleviating the pressure of natural aggregate shortage. Based on the above statement, this application provides a method for preparing walkway bricks by recycling waste circuit boards. Summary of the Invention

[0005] To address the issues raised in the background art, this application provides a method for recycling waste circuit boards into walkway bricks. By combining the interfacial bridging of anionic polyacrylamide water-reducing enhancers with the dispersive water-reducing properties of wood sulfonate water-reducing agents and the secondary hydration of fly ash / slag, the weak interfacial bonding between non-metallic powders and cement and the poor slurry fluidity are addressed, ultimately producing high-strength, durable recycled walkway bricks.

[0006] This application provides a method for recycling waste circuit boards to prepare walkway bricks, using the following technical solutions: A method for preparing walkway bricks by recycling waste circuit boards comprises the following steps: S1. Collect waste circuit boards, remove metal components and wires, crush and screen them, and remove metal components to obtain non-metallic powder; S2. Mix non-metallic powder, building material components, water reducing agent, water reducing enhancer and other additives to obtain a mixture; vibrate and pressurize the mixture into shape, and balance the formed body to obtain a waste circuit board for preparing walkway bricks; wherein the water reducing enhancer is epoxy-modified anionic polyacrylamide.

[0007] Further preferably, a method for recycling waste circuit boards to prepare walkway bricks comprises the following steps: S1. Collect waste circuit boards, mechanically disassemble them, remove metal components and wires, and then crush and screen them to break them into material particles with a particle size of less than 5 mm. After sorting and removing metal components, non-metallic powder is obtained; S2. Non-metallic powder, silicate cement, other building material components, water reducing agent, water reducing enhancer and other additives are mixed to obtain a mixture; the mixture is vibrated and pressurized to form, and the formed body is balanced to obtain a waste circuit board for preparing walkway bricks; wherein the water reducing enhancer is epoxy-modified anionic polyacrylamide.

[0008] Furthermore, in step S1, the specific operation of the screening process is: The crushed material is initially screened using a 4-5mm aperture sieve to separate coarse particles with a particle size >5mm; then a 2-3mm aperture sieve is used for fine screening to further separate medium particles of 2-5mm, and finally a 1mm aperture sieve is used for final screening.

[0009] Furthermore, in step S1, the screening process adopts vibration screening with a vibration frequency of 50-80 Hz, an amplitude of 1-2 mm, and a screening time of 10-15 minutes per batch.

[0010] Furthermore, in step S1, the separation includes magnetic separation, eddy current separation and electrostatic separation steps.

[0011] Furthermore, in step S1, the specific operation of the sorting is: The material particles are fed into a magnetic separator, and the magnetic field strength of the magnetic separator is set to 0.3-1.5T, the feeding rate is 50-80kg / h, and the magnetic roller speed is 20-30rpm. The magnetic material is recovered and the non-magnetic material is further fed into an eddy current separator, with the frequency set to 100-1000Hz, the magnetic field strength to 0.2-0.5T, the roller speed to 200-400rpm, and the material ejection height to 150-200mm. The conductive non-ferrous metal is recovered and the non-metallic components are separated; the non-metallic components are fed into a high-voltage electrostatic separator, with the voltage set to 10-20kV, the plate spacing to 50-100mm, the feeding rate to 30-50kg / h, and the ambient humidity controlled below 40RH%. After recovering the metal impurities, non-metallic powder is collected.

[0012] Furthermore, in step S2, the other building material components include fly ash and slag powder.

[0013] Furthermore, in step S2, the other auxiliary agent used is at least one of sodium citrate and sodium gluconate.

[0014] In the above technical solution, the solubility product of sodium citrate or sodium gluconate is lower than that of sulfonate water reducer, and it can be used as a complexing agent to preferentially react with Ca in the system. 2+ Binding to prevent Ca 2+ - The formation of sulfonate precipitation, resulting in water reduction failure.

[0015] Furthermore, in step S2, in the mixture, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives is (30-40):(25-35):(20-30):(0.5-1.5):(0.3-1):(0.1-0.3).

[0016] Furthermore, in step S2, the mixture is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water and stir at a high speed for 1-2 hours to obtain a mixture A; A2. Add Portland cement, other additives, and other building material components into a mixer, set the mixer speed to 30-40 rpm for mixing, add mixture A, add water to the system until the water-cement ratio reaches 0.3-0.35, then increase the speed and continue stirring to obtain a mixture.

[0017] Furthermore, in step S2, the mixture is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water at a bath ratio of 1 g:10 mL, and stir at 800-1000 rpm for 1-2 hours to obtain a mixture A. During the above reaction process, the hydrophilic groups of the water reducing enhancer are adsorbed on the surface of the non-metallic powder by electrostatic action, and the long carbon chain hydrophobic groups face the air, thereby enhancing the compatibility with water and anionic water reducing agent.

[0018] A2. Add Portland cement, other additives, and other building material components into a mixer, set the mixer speed to 30-40 rpm, mix for 5-8 minutes, then add mixture A, add water to the system until the water-cement ratio reaches 0.3-0.35, then increase the speed to 50-60 rpm, and continue stirring for 3-5 minutes to obtain a mixture.

[0019] Furthermore, in step S2, the water reducer is preferably a wood sulfonate water reducer.

[0020] Furthermore, in step S2, the water reducing enhancer is specifically prepared by the following steps: S21, adding acrylamide to deionized water and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to the NaOH solution and stirring to obtain a sodium acrylate aqueous solution; ultrasonically dispersing the epoxy group-containing monomer in anhydrous ethanol to obtain an epoxy monomer dispersion; S22. Mix the acrylamide aqueous solution, the sodium acrylate aqueous solution and the epoxy monomer dispersion, introduce an inert gas, add an initiator and an epoxy group protective agent, increase the system temperature to 40-50°C, stir and react for 4-8 hours, cool to room temperature, add anhydrous ethanol and centrifuge for 10-15 minutes, filter, wash the precipitate, dry, crush and sieve to obtain a water-reducing enhancer.

[0021] Furthermore, in step S2, the water reducing enhancer is specifically prepared by the following steps: S21. Add acrylamide to deionized water at a mass volume ratio of 1 g: (5-10) mL, and stir at room temperature until dissolved to obtain an acrylamide aqueous solution; add acrylic acid to a 5-10 wt% NaOH solution at a mass volume ratio of (0.5-1) g: 5 mL, and stir at room temperature until dissolved to obtain a sodium acrylate aqueous solution; add an epoxy group-containing monomer to anhydrous ethanol at a mass volume ratio of (0.5-1) g: 5 mL, and ultrasonically disperse for 8-10 minutes to obtain an epoxy monomer dispersion; S22. Mix an aqueous acrylamide solution, an aqueous sodium acrylate solution and an epoxy monomer dispersion, and introduce an inert gas for 20-30 minutes; then add an initiator and an epoxy group protecting agent to the system, increase the system temperature to 40-50°C, stir and react at a rate of 200-300 rpm for 4-8 hours, then naturally cool to room temperature, add anhydrous ethanol three times the volume of the system and centrifuge at a rate of 4000-5000 rpm for 10-15 minutes, filter, wash the precipitate 3-4 times with a deionized water / ethanol mixture (volume ratio 1:1), and dry it at 40-50°C to constant weight, crush it through an 80-mesh sieve to obtain a water-reducing enhancer.

[0022] In the above reaction process, the anionic monomer (sodium acrylate), the nonionic monomer (acrylamide) and the epoxy-containing monomer are combined through a free radical copolymerization reaction to form a copolymer containing both anionic groups such as carboxyl groups and epoxy groups, thereby retaining the anionic properties and introducing modification functions.

[0023] Furthermore, the mass ratio of acrylamide, sodium acrylate and epoxy group-containing monomer is (60-70):(20-30):(5-10).

[0024] Furthermore, in step S21, the epoxy group-containing monomer is preferably glycidyl methacrylate.

[0025] Furthermore, the initiator is potassium persulfate, and the usage amount is 0.05-0.2% of the total mass of acrylamide, sodium acrylate and monomer containing epoxy group.

[0026] Furthermore, the epoxy group protecting agent is tert-butyl glycidyl ether, and the usage amount is 0.5-2% of the total mass of acrylamide, sodium acrylate and monomer containing epoxy group.

[0027] Furthermore, the vibration molding frequency is 50-60 Hz, the amplitude is 0.5-0.8 mm, and the molding pressure is 8-20 MPa.

[0028] Furthermore, in step S2, the specific operations of the equalization processing are: The formed green body was balanced at 20-40°C and 80-85 RH% for 1-3 days.

[0029] In summary, this application has the following beneficial effects: In this technical solution, the metal components of discarded circuit boards are recovered and non-metallic powder containing epoxy resin and glass fiber is converted into aggregate, which is then used as a component of walkway tiles. The porous structure of this non-metallic powder provides permeable channels in the tiles, facilitating rapid water penetration. Improved components and preparation processes, including epoxy-modified anionic polyacrylamide, enhance the bonding between the non-metallic powder and other components, maintaining the structural stability of the tiles. This technical solution reduces mineral resource consumption and aligns with the concept of a "zero-waste city."

[0030] During the preparation of the walkway bricks, Portland cement hydrates to form a CSH gel-strengthening framework, while secondary hydration of fly ash / slag powder from other building materials fills the pores. A wood sulfonate water reducer, combined with epoxy-modified anionic polyacrylamide, is also used as a water-reducing enhancer for the walkway bricks containing waste circuit board components. The sulfonic acid groups of the LS adsorb on the surface of cement particles, forming a negatively charged layer that disperses the particles through electrostatic repulsion. The polymer chains of the water-reducing enhancer wrap around the surface of the cement particles, hindering direct contact between them and extending the stability of the dispersion. Furthermore, the anionic nature of the water-reducing enhancer synergizes with the sulfonic acid groups of the LS to increase the surface negative charge density, strengthening electrostatic repulsion and further reducing the probability of cement particle agglomeration, thereby enhancing the bonding between the components.

[0031] In addition, the filling effect of fly ash / slag powder reduces internal stress concentration, components such as sodium citrate in other additives delay the setting time and avoid early rapid water loss and shrinkage, and the interfacial bonding of epoxy-modified anionic polyacrylamide can inhibit microcracks. The three work together to reduce the shrinkage rate and show a synergistic effect. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] The raw materials involved in the specific implementation of this application are industrial pure. Waste circuit boards: Foxconn's scrapped PCB circuit boards.

[0034] Portland cement: Conch Cement, PO 42.5.

[0035] Fly ash: Class II ash, fineness ≤45μm, water requirement ratio ≤95%, loss on ignition ≤8%.

[0036] Slag powder: S95 grade.

[0037] The wood sulfonate water reducer used is: CAS number: 8068-05-1, brand is Shanghai Jizhi Biochemical.

[0038] The polycarboxylate water reducer used is: model PCA-1, brand Jiangsu Subote New Materials.

[0039] Example 1 A method for preparing walkway bricks by recycling waste circuit boards comprises the following steps: S1. Collect waste circuit boards, mechanically disassemble them, remove metal components and wires, and then crush and screen them to break them into material particles with a particle size of less than 5 mm. After sorting and removing metal components, non-metallic powder is obtained; The specific operations of the crushing and screening process are as follows: Vibration screening is used with a vibration frequency of 80Hz, an amplitude of 2mm, and a screening time of 15 minutes per batch. The crushed material is initially screened using a 5mm aperture screen to separate coarse particles with a particle size greater than 5mm. This is followed by fine screening using a 3mm aperture screen to further separate medium particles, and finally a 1mm aperture screen for final screening.

[0040] The specific operations for separating the metal components are: The material particles are input into a magnetic separator, and the magnetic field strength of the magnetic separator is set to 1.5T, the feeding rate is 60kg / h, and the magnetic roller speed is 30rpm. The magnetic material is recovered and the non-magnetic material is further input into an eddy current separator, with the frequency set to 800Hz, the magnetic field strength to 0.3T, the roller speed to 300rpm, and the material ejection height to 200mm. The conductive non-ferrous metal is recovered and the non-metallic components are separated; the non-metallic components are input into a high-voltage electrostatic separator, with the voltage set to 15kV, the plate spacing to 80mm, the feeding rate to 40kg / h, and the ambient humidity controlled below 40RH%. After recovering the metal impurities, the non-metallic powder is collected.

[0041] S2. Non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives are mixed to obtain a mixture; in the mixture, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives is 30:25:20:0.5:0.3:0.1; the mixture is vibrated and pressurized, the vibration molding frequency is 60 Hz, the amplitude is 0.8 mm, the molding pressure is 15 MPa, the brick size is set to 200×100×50 mm, and the molded green body is balanced at 25° C. and 85 RH% for 1 day to obtain a waste circuit board recycling and preparation of walkway bricks; Wherein, the mixture is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water at a bath ratio of 1 g:10 mL, and stir at 800 rpm for 1 hour to obtain a mixture A. A2. Add Portland cement, other additives, and other building material components to a mixer, set the mixer speed to 40 rpm, mix for 5 minutes, then add Mixture A, add water to the system until the water-cement ratio reaches 0.3, then increase the speed to 50 rpm and continue stirring for 3 minutes to obtain a mixture; The other building material components are obtained by mixing fly ash and slag powder in a mass ratio of 1:1; the other auxiliary agent is sodium citrate; and the water reducer is a wood sulfonate water reducer.

[0042] The water-reducing enhancer is an epoxy-modified anionic polyacrylamide, which is prepared by the following steps: S21, adding acrylamide to deionized water at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to a 10 wt % NaOH solution at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain a sodium acrylate aqueous solution; adding an epoxy group-containing monomer to anhydrous ethanol at a mass volume ratio of 1 g:5 mL, and ultrasonically dispersing for 10 minutes to obtain an epoxy monomer dispersion; The monomer containing epoxy group is glycidyl methacrylate; S22. Mix an acrylamide aqueous solution, a sodium acrylate aqueous solution and an epoxy monomer dispersion, and introduce nitrogen for 20 minutes. The mass ratio of acrylamide, sodium acrylate and the monomer containing an epoxy group is 60:20:5; then add an initiator and an epoxy group protecting agent to the system, wherein the initiator is potassium persulfate, and the amount used is 0.05% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; the epoxy group protecting agent is tert-butyl glycidyl ether, and the amount used is 0.5% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; increase the system temperature to 40°C, stir and react at a rate of 300 rpm for 4 hours, then cool naturally to room temperature, add three times the volume of anhydrous ethanol of the system and centrifuge at a rate of 4000 rpm for 15 minutes, filter, wash the precipitate 3 times with a deionized water / ethanol mixture (volume ratio of 1:1), and dry to constant weight at 40°C, crush and pass through an 80-mesh sieve to obtain a water-reducing enhancer.

[0043] Example 2 A method for preparing walkway bricks by recycling waste circuit boards comprises the following steps: S1. Collect waste circuit boards, mechanically disassemble them, remove metal components and wires, and then crush and screen them to break them into material particles with a particle size of less than 5 mm. After sorting and removing metal components, non-metallic powder is obtained; The specific operations of the crushing and screening process are as follows: Vibration screening is used with a vibration frequency of 80Hz, an amplitude of 2mm, and a screening time of 15 minutes per batch. The crushed material is initially screened using a 5mm aperture screen to separate coarse particles with a particle size greater than 5mm. This is followed by fine screening using a 3mm aperture screen to further separate medium particles, and finally a 1mm aperture screen for final screening.

[0044] The specific operations for separating the metal components are: The material particles are input into a magnetic separator, and the magnetic field strength of the magnetic separator is set to 1.5T, the feeding rate is 60kg / h, and the magnetic roller speed is 30rpm. The magnetic material is recovered and the non-magnetic material is further input into an eddy current separator, with the frequency set to 800Hz, the magnetic field strength to 0.3T, the roller speed to 300rpm, and the material ejection height to 200mm. The conductive non-ferrous metal is recovered and the non-metallic components are separated; the non-metallic components are input into a high-voltage electrostatic separator, with the voltage set to 15kV, the plate spacing to 80mm, the feeding rate to 40kg / h, and the ambient humidity controlled below 40RH%. After recovering the metal impurities, the non-metallic powder is collected.

[0045] S2. Non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives are mixed to obtain a mixture; in the mixture, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives is 35:30:25:1:0.6:0.2; the mixture is vibrated and pressurized, the vibration molding frequency is 60 Hz, the amplitude is 0.8 mm, the molding pressure is 15 MPa, the brick size is set to 200×100×50 mm, and the molded green body is balanced at 25° C. and 85 RH% for 1 day to obtain a waste circuit board recycling and preparation of walkway bricks; Wherein, the mixture is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water at a bath ratio of 1 g:10 mL, and stir at 900 rpm for 1.5 hours to obtain a mixture A. A2. Add Portland cement, other additives, and other building material components to a mixer, set the mixer speed to 40 rpm, mix for 8 minutes, then add Mixture A, add water to the system until the water-cement ratio reaches 0.35, then increase the speed to 60 rpm and continue stirring for 5 minutes to obtain a mixture; The other building material components are obtained by mixing fly ash and slag powder in a mass ratio of 1:1; the other auxiliary agent is sodium citrate; and the water reducer is a wood sulfonate water reducer.

[0046] The water-reducing enhancer is an epoxy-modified anionic polyacrylamide, which is prepared by the following steps: S21, adding acrylamide to deionized water at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to a 10 wt % NaOH solution at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain a sodium acrylate aqueous solution; adding an epoxy group-containing monomer to anhydrous ethanol at a mass volume ratio of 1 g:5 mL, and ultrasonically dispersing for 10 minutes to obtain an epoxy monomer dispersion; The monomer containing epoxy group is glycidyl methacrylate; S22. Mix an acrylamide aqueous solution, a sodium acrylate aqueous solution and an epoxy monomer dispersion, and introduce nitrogen for 25 minutes. The mass ratio of acrylamide, sodium acrylate and the monomer containing an epoxy group is 65:25:8; then add an initiator and an epoxy group protecting agent to the system, wherein the initiator is potassium persulfate, and the amount used is 0.1% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; the epoxy group protecting agent is tert-butyl glycidyl ether, and the amount used is 1% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; increase the system temperature to 45°C, stir and react at a rate of 300 rpm for 6 hours, then cool naturally to room temperature, add three times the volume of anhydrous ethanol and centrifuge at a rate of 4500 rpm for 15 minutes, filter, wash the precipitate 4 times with a deionized water / ethanol mixture (volume ratio of 1:1), and dry to constant weight at 50°C, crush and pass through an 80-mesh sieve to obtain a water-reducing enhancer.

[0047] Example 3 A method for preparing walkway bricks by recycling waste circuit boards comprises the following steps: S1. Collect waste circuit boards, mechanically disassemble them, remove metal components and wires, and then crush and screen them to break them into material particles with a particle size of less than 5 mm. After sorting and removing metal components, non-metallic powder is obtained; The specific operations of the crushing and screening process are as follows: Vibration screening is used with a vibration frequency of 80Hz, an amplitude of 2mm, and a screening time of 15 minutes per batch. The crushed material is initially screened using a 5mm aperture screen to separate coarse particles with a particle size greater than 5mm. This is followed by fine screening using a 3mm aperture screen to further separate medium particles, and finally a 1mm aperture screen for final screening.

[0048] The specific operations for separating the metal components are: The material particles are input into a magnetic separator, and the magnetic field strength of the magnetic separator is set to 1.5T, the feeding rate is 60kg / h, and the magnetic roller speed is 30rpm. The magnetic material is recovered and the non-magnetic material is further input into an eddy current separator, with the frequency set to 800Hz, the magnetic field strength to 0.3T, the roller speed to 300rpm, and the material ejection height to 200mm. The conductive non-ferrous metal is recovered and the non-metallic components are separated; the non-metallic components are input into a high-voltage electrostatic separator, with the voltage set to 15kV, the plate spacing to 80mm, the feeding rate to 40kg / h, and the ambient humidity controlled below 40RH%. After recovering the metal impurities, the non-metallic powder is collected.

[0049] S2. Non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives are mixed to obtain a mixture; in the mixture, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives is 40:35:30:1.5:1:0.3; the mixture is vibrated and pressurized, the vibration molding frequency is 60 Hz, the amplitude is 0.8 mm, the molding pressure is 15 MPa, the brick size is set to 200×100×50 mm, and the molded green body is balanced at 25° C. and 85 RH% for 1 day to obtain a waste circuit board recycling and preparation of walkway bricks; Wherein, the mixture is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water at a bath ratio of 1 g:10 mL, and stir at 1000 rpm for 2 hours to obtain a mixture A. A2. Add Portland cement, other additives, and other building material components to a mixer, set the mixer speed to 40 rpm, mix for 8 minutes, then add Mixture A, add water to the system until the water-cement ratio reaches 0.35, then increase the speed to 60 rpm and continue stirring for 5 minutes to obtain a mixture; The other building material components are obtained by mixing fly ash and slag powder in a mass ratio of 1:1; the other auxiliary agent is sodium citrate; and the water reducer is a wood sulfonate water reducer.

[0050] The water-reducing enhancer is an epoxy-modified anionic polyacrylamide, which is prepared by the following steps: S21, adding acrylamide to deionized water at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to a 10 wt % NaOH solution at a mass volume ratio of 1 g:5 mL, and stirring at room temperature until dissolved to obtain a sodium acrylate aqueous solution; adding an epoxy group-containing monomer to anhydrous ethanol at a mass volume ratio of 1 g:5 mL, and ultrasonically dispersing for 10 minutes to obtain an epoxy monomer dispersion; The monomer containing epoxy group is glycidyl methacrylate; S22. Mix an acrylamide aqueous solution, a sodium acrylate aqueous solution and an epoxy monomer dispersion, and introduce nitrogen for 30 minutes. The mass ratio of acrylamide, sodium acrylate and the monomer containing an epoxy group is 70:30:10; then add an initiator and an epoxy group protecting agent to the system, wherein the initiator is potassium persulfate, and the amount used is 0.2% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; the epoxy group protecting agent is tert-butyl glycidyl ether, and the amount used is 2% of the total mass of acrylamide, sodium acrylate and the monomer containing an epoxy group; increase the system temperature to 50°C, stir and react at a rate of 300 rpm for 8 hours, then cool naturally to room temperature, add three times the volume of anhydrous ethanol of the system and centrifuge at a rate of 5000 rpm for 15 minutes, filter, wash the precipitate 4 times with a deionized water / ethanol mixture (volume ratio 1:1), and dry to constant weight at 50°C, crush and pass through an 80-mesh sieve to obtain a water-reducing enhancer.

[0051] Comparative Example 1 The difference between this comparative example and Example 2 is that in step S2, a water reducing agent is used instead of a water reducing enhancer. That is, in the mixture, the mass ratio of non-metallic powder, Portland cement, other building material components, water reducing agent, and other additives is 40:35:30:2.5:0.3; Comparative Example 2 The difference between this comparative example and Example 2 is that anionic acrylamide is used instead of the water-reducing enhancer. That is, in this comparative example, the water-reducing enhancer is anionic polyacrylamide, which is specifically prepared by the following steps: S21, adding acrylamide to deionized water at a mass volume ratio of 1 g: 5 mL, and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to a 10 wt % NaOH solution at a mass volume ratio of 1 g: 5 mL, and stirring at room temperature until dissolved to obtain a sodium acrylate aqueous solution; S22. Mix an acrylamide aqueous solution and a sodium acrylate aqueous solution, introduce nitrogen, and the ventilation time is 25 minutes. The mass ratio of acrylamide to sodium acrylate is 65:25; then add an initiator to the system, wherein the initiator is ammonium persulfate, and the amount used is 0.1% of the total mass of acrylamide and sodium acrylate; increase the system temperature to 45°C, stir and react at a rate of 300 rpm for 6 hours, then naturally cool to room temperature, add three times the volume of anhydrous ethanol of the system and centrifuge at a rate of 4500 rpm for 15 minutes, filter, wash the precipitate 4 times with a deionized water / ethanol mixture (volume ratio of 1:1), and dry it at 50°C to constant weight, crush it through an 80-mesh sieve to obtain a water-reducing enhancer.

[0052] Comparative Example 3 The difference between this comparative example and Example 2 is that in step S2, a water reducer is used instead of other additives; that is, in the mixture, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives is 35:30:25:1.2:0.6.

[0053] Comparative Example 4 The difference between this comparative example and Example 2 is that in step S2, the water reducer is a polycarboxylate water reducer.

[0054] Comparative Example 5 The difference between this comparative example and Example 2 is that the mixed material is prepared by direct mixing without premixing; that is, the mixed material in this comparative example is specifically prepared by the following steps: Add non-metallic powder, water reducing agent and water reducing enhancer into the mixer, add deionized water into the mixer at a bath ratio of 1g:10mL, then add silicate cement, other additives and other building material components, set the mixer speed to 40rpm, mix for 8 minutes, add water to the system until the water-cement ratio is 0.35, then increase the speed to 60rpm, continue stirring for 5 minutes to obtain a mixture.

[0055] Performance Testing The performance of the walkway brick samples prepared in Examples 1-3 and Comparative Examples 1-5 of the present application was tested. The specific test items and test methods are as follows: 1. Anti-shrinkage performance test: The walkway brick samples prepared in different groups were cured in a natural environment for 28 days, and the shrinkage rate of the samples was tested using a concrete shrinkage meter. The curing conditions were: 20℃±2℃, humidity 95RH%. The shrinkage rate was calculated as (initial length - sample length after curing) / initial length×100% to determine the sample's anti-shrinkage performance.

[0056] 2. Compression performance test: The walkway brick samples prepared in different groups were cured in a natural environment for 28 days under the following curing conditions: 20℃±2℃, humidity 95RH%. The surface of the samples was then cleaned and placed in the center of the lower plate of a hydraulic pressure testing machine (range 0-500kN, accuracy ±1%). The load was applied at a loading rate of 0.5MPa / s until the sample failed. The maximum failure load was recorded and the compressive strength was calculated using the calculation method of σ=F / A, where F is the maximum failure load and A is the cross-sectional area of ​​the specimen, to determine the compressive performance of the sample.

[0057] Crack resistance test: The walkway brick samples prepared from different groups were cured in a natural environment for 28 days under the curing conditions of 20℃±2℃ and 40RH%. Fluorescent agent was then sprayed on the surface of the samples, and microcracks on the surface of the samples were observed to determine the crack resistance level of the samples and judge the crack resistance performance of different samples.

[0058] The evaluation criteria for crack resistance are shown in Table 1 below; wherein N represents the number of cracks on all sides of the sample, L represents the crack length, and W represents the crack width.

[0059] Table 1

[0060] The specific performance test results are shown in Table 2: Table 2

[0061] It can be seen from the results shown in Table 2 above that the quality of the walkway brick samples prepared in Examples 1-3 of the present application is significantly improved by compounding aggregated non-metallic powder, wood sulfonic acid water reducer and epoxy-modified anionic polyacrylamide to enhance the interface, and its comprehensive performance is significantly better than that of the samples prepared in Comparative Examples 1-5, that is, within the technical solution defined in the present application, the comprehensive performance of the walkway brick samples prepared is excellent.

[0062] From the results of Comparative Example 1, it can be seen that without the interface bonding of epoxy-modified anionic polyacrylamide, the cement paste is prone to water loss and shrinkage, and the water reducer relies solely on the dispersing effect of wood sulfonate, resulting in performance such as shrinkage being lower than that of the embodiment. From the results of Comparative Example 2, it can be seen that the use of anionic acrylamide instead of water-reducing reinforcing agent, without epoxy groups filling the micropores of non-metallic powder, the interface bonding effect is reduced, and the compressive strength and shrinkage indexes are reduced. From the results of Comparative Example 3, it can be seen that without sodium citrate to delay coagulation, Ca 2+ The formation of sulfonate precipitates leads to water reduction failure, rapid early water loss, and decreased shrinkage and crack resistance. The results in Comparative Example 4 show that polycarboxylate water-reducing agents offer better dispersion, but their synergy with epoxy-modified anionic polyacrylamide is weak, resulting in lower performance than in the examples. The results in Comparative Example 5 show that without premixing the components, the non-metallic powders and cement locally agglomerated and unevenly dispersed, resulting in uneven water-cement ratios, significantly increased shrinkage, and decreased performance.

[0063] The samples in Example 2 were tested for harmful substance content limits, with formaldehyde emission and soluble heavy metal content tested according to the methods in GB 18580 and GB 28481, respectively. The specific test results are shown in Table 3 below.

[0064] Table 3

[0065] From the results in Table 3, it can be seen that the content of harmful substances in the sample in Example 2 is low, meets the national standards, and poses no health risks.

[0066] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0067] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing walkway bricks by recycling waste circuit boards, characterized in that: The method comprises the following preparation steps: S1. Collect waste circuit boards, remove metal components and wires, crush and screen them, and remove metal components to obtain non-metallic powder; S2. Mix non-metallic powder, building material components, water reducing agent, water reducing enhancer and other additives to obtain a mixture; vibrate and pressurize the mixture into shape, and balance the formed body to obtain a waste circuit board for preparing walkway bricks; wherein the water reducing enhancer is epoxy-modified anionic polyacrylamide.

2. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S1, the screening process adopts vibration screening with a vibration frequency of 50-80 Hz, an amplitude of 1-2 mm, and a screening time of 10-15 minutes per batch.

3. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S1, the separation includes magnetic separation, eddy current separation and electrostatic separation steps.

4. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S2, the other building material components include fly ash and slag powder.

5. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S2, the other auxiliary agent used is at least one of sodium citrate and sodium gluconate.

6. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S2, the mass ratio of non-metallic powder, silicate cement, other building material components, water reducer, water reducing enhancer and other additives in the mixture is (30-40):(25-35):(20-30):(0.5-1.5):(0.3-1):(0.1-0.3).

7. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S2, the mixed material is specifically prepared by the following steps: A1. Mix the non-metallic powder with a water reducing agent and a water reducing enhancer, add deionized water and stir at a high speed for 1-2 hours to obtain a mixture A; A2. Add Portland cement, other additives, and other building material components into a mixer, set the mixer speed to 30-40 rpm for mixing, add mixture A, add water to the system until the water-cement ratio reaches 0.3-0.35, then increase the speed and continue stirring to obtain a mixture.

8. The method for preparing walkway bricks by recycling waste circuit boards according to claim 1, characterized in that: In step S2, the water reducing enhancer is specifically prepared by the following steps: S21, adding acrylamide to deionized water and stirring at room temperature until dissolved to obtain an acrylamide aqueous solution; adding acrylic acid to the NaOH solution and stirring to obtain a sodium acrylate aqueous solution; ultrasonically dispersing the epoxy group-containing monomer in anhydrous ethanol to obtain an epoxy monomer dispersion; S22. Mix the acrylamide aqueous solution, the sodium acrylate aqueous solution and the epoxy monomer dispersion, introduce an inert gas, add an initiator and an epoxy group protective agent, increase the system temperature to 40-50°C, stir and react for 4-8 hours, cool to room temperature, add anhydrous ethanol and centrifuge for 10-15 minutes, filter, wash the precipitate, dry, crush and sieve to obtain a water-reducing enhancer.

9. The method for preparing walkway bricks by recycling waste circuit boards according to claim 8, characterized in that: The mass ratio of acrylamide, sodium acrylate and monomer containing epoxy group is (60-70):(20-30):(5-10).

10. The method for preparing walkway bricks by recycling waste circuit boards according to claim 8, characterized in that: In step S21, the monomer containing an epoxy group is glycidyl methacrylate.

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