A method for preparing permeable ecological bricks based on industrial waste residue

Abstract

This invention provides a method for preparing permeable ecological bricks based on industrial waste residue, belonging to the field of industrial waste residue recycling technology. Firstly, the invention uses pyrolysis to change the heavy metal form into stable oxides, and then soaks the bricks in phosphoric acid solution to form insoluble phosphate complexes, achieving deep pre-stabilization of the waste residue. Subsequently, surface modification is performed to form a hydrophobic protective network at the molecular level. Next, an upper permeable layer and a lower support layer are designed according to an optimized formula, and the particle size distribution is optimized using a modified Apollonian sphere packing algorithm. Then, a double-layer structure is formed, and the thickness ratio of the upper and lower layers is precisely controlled through an interlayer balance exponential function. Next, a dense hydrated calcium silicate gel network is formed through low-pressure steam curing. Finally, microporous treatment with citric acid solution and sealing treatment with nano-silica sol are performed to construct a molecular-level protective barrier, solving the technical problem of insufficient waste residue stabilization in the preparation of permeable bricks from industrial waste residue.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste recycling technology, and specifically relates to a method for preparing ecological permeable bricks based on industrial waste. Background Technology

[0002] Permeable bricks, as an important component of urban sponge systems, play a crucial role in improving urban flooding, replenishing groundwater, and enhancing the urban ecological environment. Traditional permeable bricks are mainly made from natural aggregates and cement-based materials. However, with resource scarcity and increasingly stringent environmental requirements, using industrial waste as a substitute for some raw materials in the production of permeable bricks has become a research hotspot. Current technologies typically employ high-temperature sintering, cementitious bonding, or organic resin bonding methods to prepare permeable bricks from industrial waste for use in urban road paving, parks, parking lots, and other applications. However, existing technologies for preparing permeable bricks based on industrial waste suffer from serious problems with waste stabilization. First, conventional physical encapsulation methods have limited effectiveness in fixing heavy metals in the waste; during long-term use, moisture infiltration leads to the gradual leaching of heavy metals, causing secondary pollution. Second, single chemical stabilizer treatments are insufficient to address the complex and diverse heavy metal composition in the waste, resulting in incomplete stabilization. Third, existing surface modification technologies fail to effectively block the contact between the waste and external moisture, allowing heavy metals to migrate into the environment through the porous network, posing potential ecological risks. To achieve safe and resource-efficient utilization of permeable bricks based on industrial waste, the core challenge lies in thoroughly addressing the stabilization of harmful components in the waste. Existing single-treatment methods and simple structural designs are insufficient for comprehensive stabilization, especially when permeable bricks are exposed to complex environments for extended periods, leading to a significant decrease in stabilization effectiveness. Therefore, there is an urgent need to develop a multi-faceted synergistic stabilization technology system and optimized structural design schemes to address the technical bottleneck of insufficient waste stabilization at its source. In other words, existing technologies for preparing permeable bricks from industrial waste suffer from insufficient waste stabilization. Summary of the Invention

[0003] In view of this, the present invention provides a method for preparing permeable ecological bricks based on industrial waste residue, which can solve the technical problem of insufficient stabilization of waste residue in the preparation of permeable bricks based on industrial waste residue in the prior art.

[0004] This invention is achieved as follows: A method for preparing an industrial waste-based permeable brick includes: pre-stabilizing the industrial waste through pyrolysis and phosphoric acid solution soaking; modifying the waste by mixing a silane coupling agent and a titanate coupling agent to form a hydrophobic protective network at the molecular level; designing the upper permeable layer and lower support layer materials according to an optimized formula; adjusting the proportion of particles of different sizes using optimized particle size distribution technology; forming a double-layer structure by adjusting the thickness ratio of the upper and lower layers through an interlayer balance exponential function; forming a hardened brick body through low-pressure steam curing; and finally, performing surface micropore treatment and nano-silica sol sealing treatment to prevent heavy metal leaching.

[0005] The pretreatment step of the industrial waste residue specifically involves crushing the industrial waste residue to a particle size of less than 5 mm, treating it with pyrolysis at 550 to 650°C for 180 to 240 minutes, then soaking it in a phosphoric acid solution with a mass fraction of 3 to 5% for 24 to 36 hours, washing it three times, and drying it at 105 to 110°C to constant weight to obtain stabilized waste residue.

[0006] Specifically, the step of modifying the waste residue by mixing silane coupling agent and titanate coupling agent involves mixing 2 to 4% by mass of silane coupling agent and 0.5 to 1.5% by mass of titanate coupling agent in an ethanol solution, stirring for 30 to 60 minutes to form a homogeneous solution, immersing the stabilized waste residue in the homogeneous solution for 4 to 6 hours, removing it, and drying it at 80 to 90°C for 120 to 180 minutes to obtain the modified waste residue.

[0007] The upper permeable layer consists of 40-50% modified waste residue, 20-30% coarse sand, 10-15% fly ash, 10-15% cement, 1-3% nano-silica, and 0.5-1% water-retaining agent; the lower support layer consists of 30-35% modified waste residue, 30-35% coarse sand, 15-20% fly ash, 15-20% cement, and 1-2% nano-silica.

[0008] Specifically, the optimized particle size distribution technology involves sieving and mixing the upper permeable layer material and the lower support layer material in proportions of 15 to 20% for 2.36 mm, 25 to 30% for 1.18 mm, 30 to 35% for 0.6 mm, 15 to 20% for 0.3 mm, and 5 to 10% for 0.15 mm, respectively, to prepare an upper and lower mixture with a multi-level porous structure.

[0009] Specifically, the double-layer structure forming step involves first mixing the lower layer mixture with water at a mass ratio of 0.35 to 0.4 for 3 to 5 minutes, then pouring it into a mold and compacting it to 60 to 70% of the designed thickness. Then, the upper layer mixture is mixed with water at a mass ratio of 0.38 to 0.42 for 3 to 5 minutes, poured into a mold, and compacted to 100% of the total thickness.

[0010] The input parameters of the interlayer balance exponential function include the permeability coefficient of the upper layer, the permeability coefficient of the lower layer, the compressive strength of the upper layer, the compressive strength of the lower layer, the thickness of the upper layer, the total thickness, the potential migration distance of heavy metals, and the migration restriction threshold of heavy metals; the output of the interlayer balance exponential function is used to guide the optimization of the thickness ratio of the double-layer structure.

[0011] Among them, when the interlayer balance index is between 0.9 and 1.1, it indicates that the optimal balance state has been reached. When it is greater than 1.1, the thickness of the upper layer needs to be reduced, and when it is less than 0.9, the thickness of the upper layer needs to be increased.

[0012] In this process, after the double-layer structure is formed, a layered iterative optimization scheme is adopted. First, a double-layer brick structure is established based on the initial formula. After measuring each physical parameter, the interlayer balance index value is calculated by inputting the interlayer balance index function. If the interlayer balance index value is not in the optimal range, the ratio of the thickness of the upper layer to the thickness of the lower layer and the formula parameters are adjusted, and the structure is prepared and tested again. Through 3 to 5 iterations of optimization, the interlayer balance index value is converged to the range of 1.0±0.1.

[0013] The optimized particle size distribution technology is optimized using the principle of three-dimensional spherical packing. Specifically, it adopts the modified Apollonian spherical packing algorithm, which iteratively fills the gaps between particles of different sizes to achieve a balance between porosity and strength, and solves for the optimal particle size distribution function.

[0014] This invention achieves comprehensive stabilization of heavy metals in waste residue by combining superheated decomposition-phosphoric acid stabilization pretreatment with coupling agent surface modification. A dual-layer structure design and optimized particle size distribution technology are employed to construct a microstructure capable of inhibiting heavy metal migration. Through low-pressure steam curing and surface micropore treatment, a brick with long-term stabilization capabilities is formed. This method fundamentally solves the key defect of insufficient waste residue stabilization in traditional technologies. First, pyrolysis pretreatment at 550-650℃ alters the heavy metal morphology into stable oxides, phosphorylation forms insoluble phosphate complexes that firmly lock the heavy metals within the crystal lattice, and silane and titanate coupling agents modify the molecular level to form a hydrophobic protective layer. This triple protection system comprehensively blocks the leaching pathways of heavy metals from physical, chemical, and surface microstructure perspectives. Second, differentiated design of the upper and lower layer structure formulations and optimization of the interlayer balance exponential function ensure that the migration distance of heavy metals is controlled within a safe threshold. Third, the surface sealing treatment of nano-silica sol forms a molecular-level protective barrier, further improving long-term stability. This solves the technical problem of insufficient stabilization of industrial waste residue in the preparation of permeable bricks. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention.

[0016] Figure 2 This is a schematic diagram of the double-layer structure of the permeable ecological brick obtained in Example 2. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0018] like Figure 1 The diagram shown is a flowchart of a method for preparing an industrial waste-based permeable brick according to the present invention. This method includes the following steps:

[0019] S01. Pre-treat industrial waste residue, including crushing to a particle size of less than 5 mm, treating it by pyrolysis at 550 to 650°C for 180 to 240 minutes, then soaking it in a phosphoric acid solution with a mass fraction of 3 to 5% for 24 to 36 hours, and drying it to constant weight at 105 to 110°C after three washes to obtain stabilized waste residue.

[0020] S02. Prepare the modifier by mixing 2 to 4% by mass of silane coupling agent and 0.5 to 1.5% by mass of titanate coupling agent in an ethanol solution and stirring for 30 to 60 minutes to form a homogeneous solution. Immerse the stabilized waste residue in the homogeneous solution for 4 to 6 hours and then remove it. Dry it at 80 to 90°C for 120 to 180 minutes to obtain the modified waste residue.

[0021] S03. Prepare a multi-layer structure formula. The upper permeable layer formula consists of 40-50% modified waste residue, 20-30% coarse sand, 10-15% fly ash, 10-15% cement, 1-3% nano silica, and 0.5-1% water-retaining agent. The lower support layer formula consists of 30-35% modified waste residue, 30-35% coarse sand, 15-20% fly ash, 15-20% cement, and 1-2% nano silica.

[0022] S04. Using optimized particle size distribution technology, the upper permeable layer material and the lower support layer material are screened and mixed in proportions of 15 to 20% for 2.36 mm, 25 to 30% for 1.18 mm, 30 to 35% for 0.6 mm, 15 to 20% for 0.3 mm, and 5 to 10% for 0.15 mm, respectively, to prepare an upper and lower mixture with a multi-level porous structure.

[0023] S05. To form a double-layer structure, first mix the lower layer mixture with water at a mass ratio of 0.35 to 0.4 for 3 to 5 minutes, pour it into the mold and compact it to 60 to 70% of the designed thickness. Then mix the upper layer mixture with water at a mass ratio of 0.38 to 0.42 for 3 to 5 minutes, pour it into the mold and compact it to 100% of the total thickness. Then adjust the ratio of the upper layer thickness to the lower layer thickness according to the interlayer balance exponential function calculation results.

[0024] S06. The formed bricks are cured with low-pressure steam. First, they are pre-cured at 20 to 25°C for 24 to 36 hours, and then steam-cured at 65 to 75°C and 90 to 95% relative humidity for 72 to 96 hours to form solidified and hardened bricks.

[0025] S07. Perform surface microporous treatment by spraying the hardened brick surface with a citric acid solution of 10 to 15% by mass. After standing for 30 to 60 minutes, rinse with clean water to form additional microporous structures and improve water permeability. At the same time, use nano-silica sol for surface sealing treatment to prevent heavy metal leaching, and obtain the final industrial waste-based ecological permeable brick.

[0026] Among them, pyrolysis specifically refers to heating industrial waste residue under air-isolated or oxygen-limited conditions to decompose and volatilize organic matter, while changing the form of heavy metals into stable oxide forms, thereby reducing the activity and leaching risk of heavy metals.

[0027] Stabilized waste residue specifically refers to waste residue materials that, after physical crushing and chemical treatment, have heavy metal elements fixed in the mineral lattice or form insoluble phosphate complexes, thereby reducing environmental risks.

[0028] Specifically, modified waste residue refers to waste residue materials whose surface properties change after being treated with coupling agents, resulting in improved compatibility with matrix materials and enhanced stability of heavy metals.

[0029] Among them, the multi-level pore structure specifically refers to the simultaneous existence of interconnected pores of different scales, such as micron, submicron, and nano, within the brick body, forming a network structure that combines high permeability and high filtration.

[0030] Among them, the optimized particle size distribution technology specifically refers to the method of optimizing the proportion of particles of different sizes in a mixture to form the optimal porosity between particles, thereby ensuring sufficient permeability and maintaining structural strength.

[0031] Low-pressure steam curing specifically refers to a process that uses saturated steam to promote the hydration reaction of cement under lower temperature and pressure conditions, forming a high-strength hydrated calcium silicate gel network structure, while avoiding the generation of microcracks caused by high temperature.

[0032] Among them, nano silica sol specifically refers to a colloidal solution containing silica particles with a diameter of 5 to 20 nanometers, which can penetrate into the tiny pores on the surface of bricks to form a dense protective layer and block the migration path of heavy metal ions.

[0033] The modification process of the SO2 step involves a chemical mechanism. The surface reaction of the coupling agent involves the bonding between hydroxyl groups and silane groups on the surface of the waste residue. The surface modification reaction is used to calculate the surface coverage and reaction efficiency. The inputs include the specific surface area of ​​the waste residue, the concentration of the silane coupling agent, the reaction time, the reaction temperature, and the hydroxyl density on the surface of the waste residue. The specific surface area of ​​the waste residue is determined by nitrogen adsorption, the concentration of the silane coupling agent is determined by the formulation, the reaction time is controlled by the process, the reaction temperature is controlled by the heating equipment, and the hydroxyl density on the surface of the waste residue is obtained by infrared spectroscopy analysis. The outputs are the degree of surface modification and the bonding stability index. The degree of surface modification is used to determine the amount of coupling agent, and the bonding stability index is used to predict the chemical stability of the modified waste residue during use.

[0034] Among them, the optimization of particle size distribution technology in step S04 is optimized by applying the three-dimensional spherical packing principle. Specifically, the modified Apollonian spherical packing algorithm is adopted. By iteratively filling the gaps between particles of different sizes, the balance between porosity and strength is achieved, and the optimal particle size distribution function is solved. The particle size distribution parameter is the optimization parameter and is dynamically adjusted according to the water permeability requirements.

[0035] The interlayer balance index function is defined as a mathematical expression of the overall performance balance between the upper and lower layers. The input parameters of the interlayer balance index function include the permeability coefficient of the upper layer, the permeability coefficient of the lower layer, the compressive strength of the upper layer, the compressive strength of the lower layer, the thickness of the upper layer, the total thickness, the potential migration distance of heavy metals, and the migration limitation threshold of heavy metals. The permeability coefficients of the upper and lower layers are determined by permeation experiments, the compressive strengths of the upper and lower layers are obtained by pressure tests, the thickness of the upper layer and the total thickness are determined by physical measurements, and the potential migration distance of heavy metals and the migration limitation threshold of heavy metals are evaluated by leaching experiments. The output of the interlayer balance index function is used to guide the optimization of the thickness ratio of the double-layer structure. When the interlayer balance index is between 0.9 and 1.1, it indicates that the optimal balance state has been reached. When it is greater than 1.1, the thickness of the upper layer needs to be reduced, and when it is less than 0.9, the thickness of the upper layer needs to be increased.

[0036] Among them, a layered iterative optimization scheme is adopted. First, a double-layer brick structure is established based on the initial formula. After measuring various physical parameters, the interlayer balance index value is calculated by inputting the interlayer balance index function. If the interlayer balance index value is not in the optimal range, the ratio of the thickness of the upper layer to the thickness of the lower layer and the formula parameters are adjusted, and the brick is prepared and tested again. Through 3 to 5 iterations of optimization, the interlayer balance index value is converged within the range of 1.0±0.1, so as to achieve a comprehensive balance between permeability, strength performance and environmental safety performance.

[0037] The sum of the mass percentages of all components in the upper permeable layer formulation and the lower support layer formulation is 100%.

[0038] The sum of the mass percentages of each particle size component in the upper and lower layers of the mixture is 100%.

[0039] The specific implementation methods of the above steps are described in detail below.

[0040] The specific implementation of step S01 involves systematically pretreating industrial waste residue to transform it into an environmentally safe, stabilized material. First, physical crushing is performed, using a jaw crusher to initially crush the waste residue to below 10 mm, followed by further crushing to below 5 mm using a hammer mill. During the crushing process, particle size is monitored in real time, and equipment parameters are adjusted to ensure uniform particle size. Next, the crushed waste residue is transferred to a pyrolysis furnace for pyrolysis under oxygen-isolated or limited-oxygen conditions. The furnace temperature is controlled within the range of 550 to 650°C, preferably 600°C, and the treatment time is controlled within the range of 180 to 240 minutes, preferably 210 minutes. Under these conditions, organic matter can be fully decomposed and volatilized, while heavy metals are oxidized into stable forms. After pyrolysis, the waste residue is cooled to room temperature and then transferred to a chemical treatment stage. It is soaked in a 3-5% (by mass) phosphoric acid solution, preferably 4%, for 24 to 36 hours, preferably 30 hours, with a liquid-to-solid ratio controlled at 5:1. Phosphoric acid treatment is based on the principle of chemical immobilization. Phosphate ions react with heavy metal ions in the waste residue to form insoluble phosphate precipitates, significantly reducing the activity of heavy metals. The soaked waste residue requires three washes, each with a liquid-to-solid ratio of 6:1 and a stirring time of 10 minutes, to remove residual acidic substances and soluble salts. After washing, the waste residue is placed in an oven at a temperature controlled between 105 and 110°C, preferably 108°C, and dried to constant weight. The criterion for judgment is a weight change of less than 0.1% measured twice consecutively at 2-hour intervals. The purpose of this step is to increase the specific surface area of ​​the waste residue through physical crushing and to reduce the risk of heavy metal leaching through pyrolysis and phosphoric acid stabilization treatment, laying a safe foundation for the subsequent preparation of permeable bricks.

[0041] The specific implementation of step S02 involves surface modification treatment of the waste residue to improve the interfacial compatibility between the waste residue and the cement matrix and further stabilize heavy metals. First, a modifier solution is prepared by dissolving 2-4% by mass of a silane coupling agent and 0.5-1.5% by mass of a titanate coupling agent in anhydrous ethanol. The preferred concentration of the silane coupling agent is 3%, and the preferred concentration of the titanate coupling agent is 1%. The total volume of the solution is in a 2:1 ratio to the mass of the waste residue. The solution is stirred at room temperature using a thermostatic magnetic stirrer for 30-60 minutes, preferably 45 minutes, at a stirring speed of 300 rpm, to ensure complete dissolution of the coupling agent and the formation of a homogeneous solution. Subsequently, the stabilized waste residue is immersed in the prepared solution for 4-6 hours, preferably 5 hours, with stirring every 30 minutes during this period to ensure uniform reaction. The surface modification reaction during the soaking process is based on interfacial chemistry theory. The alkoxy groups in the silane coupling agent molecule undergo a condensation reaction with the hydroxyl groups on the waste residue surface, forming chemical bonds. Simultaneously, the organic groups of the silane molecule extend outward, improving the hydrophobicity and organic compatibility of the waste residue surface. After soaking, the waste residue is removed, and the filtration rate is controlled to minimize modifier loss. The waste residue is then transferred to a constant temperature drying oven and dried at 80-90℃ for 120-180 minutes, with a preferred drying temperature of 85℃ and a preferred drying time of 150 minutes. The drying process employs segmented temperature control technology, with the temperature controlled at 70℃ for the initial 30 minutes, then gradually increased to the set temperature to prevent rapid solvent evaporation and uneven surface modification. The degree of surface modification is determined by potassium bromide pellet Fourier transform infrared spectroscopy, and the silane bonding rate is calculated. The optimized process can achieve a surface coverage of over 90%, and the stability of heavy metals is improved by 3 to 5 times. The modified waste residue after drying must be sealed and stored to prevent hydrolysis of surface groups due to moisture in the air.

[0042] The specific implementation of step S03 is to prepare a multi-layer structure formula for permeable bricks based on the functionally graded materials theory. First, each component material is accurately weighed. The upper permeable layer formula includes 40-50% modified waste residue, 20-30% coarse sand, 10-15% fly ash, 10-15% cement, 1-3% nano-silica, and 0.5-1% water-retaining agent. A preferred ratio is 45% modified waste residue, 25% coarse sand, 12% fly ash, 12% cement, 2% nano-silica, and 0.8% water-retaining agent. The lower support layer formula includes 30-35% modified waste residue, 30-35% coarse sand, 15-20% fly ash, 15-20% cement, and 1-2% nano-silica. A preferred ratio is 32% modified waste residue, 32% coarse sand, 18% fly ash, 17% cement, and 1.5% nano-silica. The multi-layer structure formulation design employs a material performance balance algorithm, comprehensively considering four dimensions: permeability, strength, durability, and environmental safety. The optimal ratio is determined through orthogonal experiments. The upper permeable layer prioritizes high porosity, with a target porosity of 25-30% and a permeability coefficient greater than 0.1 cm / s. A water-retaining agent is added to enhance ecological function, with a target water retention rate of 15-20%. The lower support layer prioritizes high strength, with a target compressive strength greater than 25 MPa, while maintaining a certain level of permeability to prevent water accumulation, with a target permeability coefficient of 0.01-0.05 cm / s. Fly ash is used in different proportions in the two layers. Based on the pozzolanic reaction theory, a lower proportion is used in the upper layer to maintain the porous structure, while a higher proportion is used in the lower layer to enhance later-stage strength and erosion resistance. Nano-silica is added as an active material, filling micropores and promoting hydration reactions, improving interfacial bonding and material density. The two-layer structure forms a physicochemical functional gradient, ensuring synergistic optimization of the overall performance of the permeable brick.

[0043] The specific implementation of step S04 involves preparing a multi-level porous structure material using optimized particle size distribution technology. First, the upper permeable layer material and the lower support layer material are prepared according to the formulation components. The materials are then sieved into five particle size grades using a standard sieving method: 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, and 0.15 mm. The sieving process uses a mechanical vibrating sieve with a vibration frequency controlled at 50 Hz and a vibration time of 15 minutes to ensure complete sieving. The optimal particle size distribution is calculated using a modified Apollonian sphere packing algorithm. This algorithm, based on three-dimensional space filling theory, treats each particle size as a rigid sphere and iteratively calculates the porosity and packing density of different particle size combinations to solve for the optimal particle size distribution function. The algorithm input parameters include the true density, apparent density, shape factor, and target porosity of each particle size component, and the output is the optimal ratio of each particle size component. The upper permeable layer material is formulated with the following proportions: 15-20% for 2.36 mm, 25-30% for 1.18 mm, 30-35% for 0.6 mm, 15-20% for 0.3 mm, and 5-10% for 0.15 mm. The preferred proportions are 17% for 2.36 mm, 28% for 1.18 mm, 32% for 0.6 mm, 18% for 0.3 mm, and 7% for 0.15 mm. The lower support layer material is formulated using the same particle size distribution, but the composition of each particle size level follows the lower layer formulation in step S03. The particle size distribution optimization process is based on the principle of pore network connectivity. By controlling the volume fraction of particles of different sizes, a multi-level pore structure is formed inside the brick, including macropores of 100-500 micrometers for the main permeable channels, mesopores of 10-100 micrometers for capillary adsorption, and micropores of 1-10 micrometers for water retention, forming a highly efficient permeable and filtration network system. Materials that have undergone gradation optimization must be stored in sealed containers to prevent stratification or segregation.

[0044] The specific implementation of step S05 is to achieve the double-layer structure molding and interlayer balance optimization of permeable bricks. First, prepare the molding mold, coating its inner surface with a release agent to ensure smooth demolding of the bricks after molding. Mix the lower support layer mixture prepared in step S04 with water at a mass ratio of 0.35 to 0.4, preferably a water-to-material ratio of 0.38. Use a forced mixer to stir for 3 to 5 minutes at a stirring speed of 60 rpm to ensure the material is fully wetted and uniformly mixed. The uniformity of mixing is assessed by sampling and testing the distribution of cement paste, with the coefficient of variation controlled below 5%. Pour the mixed lower layer material into the mold and compact it using a vibrating table at a vibration frequency of 40 Hz for 30 seconds, ensuring the material is densely packed and reaches 60 to 70% of the mold's designed thickness, preferably 65%. Next, prepare the upper permeable layer material by mixing the upper mixture prepared in step S04 with water at a mass ratio of 0.38 to 0.42, preferably a water-to-material ratio of 0.4, using the same mixing process to ensure uniform mixing. Pour the upper layer material into a mold containing the lower layer material and compact it again to 100% of the total designed thickness, forming a double-layer structure. Immediately after molding, apply the interlayer balance index function to calculate the rationality of the upper and lower layer thickness ratio. This function comprehensively considers permeability, strength, and environmental safety performance. Input parameters include the permeability coefficients of the upper and lower layers, compressive strength, and heavy metal migration characteristics, while the output parameter is the interlayer balance index value. When the interlayer balance index value is between 0.9 and 1.1, it indicates that the optimal balance state has been reached. If it is greater than 1.1, the upper layer thickness needs to be reduced; if it is less than 0.9, the upper layer thickness needs to be increased. The preferred upper and lower layer thickness ratio is 3:7. This ratio is determined through a layered iterative optimization scheme, that is, through 3 to 5 fine-tuning of the thickness ratio and formula, the interlayer balance index value finally converges to the range of 1.0 ± 0.1. After the bricks are formed, they need to undergo preliminary curing. They should be left to stand for 4 hours in an environment with a temperature of 20℃ and a relative humidity of over 95% to allow the bricks to gain a certain initial strength and prepare for subsequent curing.

[0045] The specific implementation of step S06 involves using a low-pressure steam curing process to promote cement hydration and improve the strength and durability of the permeable bricks. First, the formed bricks are transferred to a pre-curing chamber and pre-cured for 24 to 36 hours at 20 to 25°C, with a preferred temperature of 23°C and a preferred time of 30 hours. During the pre-curing stage, a constant temperature and humidity control system is used, maintaining a relative humidity above 90% to prevent surface water loss and shrinkage cracks. During pre-curing, the bricks initially harden and develop sufficient strength to withstand the temperature stress during subsequent steam curing. After pre-curing, the bricks are transferred to a steam curing chamber and steam cured using a programmed temperature rise and fall process. During the heating phase, the temperature rise rate is controlled at 5°C per hour to prevent rapid temperature increases that could cause brick cracking. Once the target temperature of 65-75°C is reached, it is maintained at a constant temperature, with 70°C being the preferred temperature. Relative humidity is controlled at 90-95%, with 93% being the preferred humidity. The curing time is 72-96 hours, with 84 hours being the preferred time. During the cooling phase, the temperature drop rate is controlled at 3°C ​​per hour to prevent thermal stress from causing microcracks. The steam curing process is based on the principles of cement hydration kinetics. Appropriate temperature and humidity conditions accelerate the hydration reaction on the surface of cement particles, promoting the formation of a hydrated calcium silicate gel network structure, while avoiding structural defects caused by high temperature and high pressure. The uniformity of temperature and humidity distribution in the curing chamber is controlled in real time through a multi-point monitoring system to ensure that all bricks receive consistent curing conditions. After curing, the bricks must undergo strength testing. The compressive strength should reach at least 85% of the design value, and the permeability coefficient should reach at least 90% of the design value before proceeding to the next step. If these standards are not met, the curing time needs to be extended or the curing parameters adjusted.

[0046] The specific implementation of step S07 involves surface micropore treatment and sealing to improve water permeability and ensure environmental safety. First, a citric acid solution with a mass fraction of 10-15%, preferably 12%, is prepared, with the pH value controlled between 2.5 and 3.0. The solution is then uniformly sprayed onto the hardened brick surface using a spraying device, with a spray volume of 200-250 ml per square meter and a spraying pressure controlled at 0.2 MPa, ensuring uniform distribution across the brick surface. Citric acid, as a weak organic acid, can selectively dissolve the cement hydration products on the brick surface, primarily reacting with calcium hydroxide and some CSH gel in the hydration products to form soluble calcium citrate, which then dissolves, creating additional microporous structures on the brick surface. After spraying, the solution is allowed to stand for 30-60 minutes, preferably 45 minutes, to allow for complete acid reaction. During the standing period, the ambient temperature is maintained at 20-25°C, and direct sunlight and wind are avoided to ensure uniform reaction. After the reaction is complete, rinse the brick surface with clean water at a pressure of 0.3 MPa for 2 minutes to ensure complete removal of residual acidic substances and reaction products. Allow the bricks to air dry naturally for 2 hours, followed by a nano-silica sol surface sealing treatment. Prepare a 3-5% nano-silica sol solution, preferably 4%, with nano-silica particles of 10-15 nanometers in size. Apply the sol evenly to the brick surface using an impregnation or spraying method, at a rate of 150-200 ml per square meter. The nano-silica sol penetrates the micropores of the brick surface based on capillary penetration and forms a network structure through a condensation reaction, creating a nanoscale protective layer on the inner walls of the pores. This blocks the migration channels for heavy metals without affecting water permeability. After treatment, dry the bricks at room temperature for 24 hours. Then, conduct water permeability and heavy metal leaching tests to verify the treatment effect. The optimized surface treatment process can increase the permeability coefficient of the brick surface by 30 to 50%, while reducing the risk of heavy metal leaching by more than 90%, thus meeting the dual requirements of ecological permeability and environmental safety.

[0047] It should be noted that the industrial waste-based permeable brick of this invention achieves multiple technical effects and significant advantages through a layered iterative optimization scheme. This method organically combines the resource utilization of waste residue with environmental safety performance. Through a dual pretreatment process of pyrolysis and phosphoric acid stabilization, it achieves the transformation and fixation of heavy metal forms, fundamentally reducing environmental risks. The coupling agent surface modification technology establishes a chemical bonding bridge between the waste residue and the matrix material, enhancing interfacial bonding and further encapsulating heavy metals. The innovative multi-level pore structure design, utilizing a modified Apollonian sphere packing algorithm, enables the permeable brick to simultaneously possess a network of interconnected micron, submicron, and nano-scale pores, forming a functional structure that unifies high permeability and high filtration. The double-layer structure design, combined with iterative optimization of the interlayer balance exponential function, achieves a synergistic effect between the high permeability of the upper layer and the high load-bearing capacity of the lower layer. By dynamically adjusting the interlayer thickness ratio and formulation parameters, it achieves the optimal balance between permeability, strength, and environmental safety performance. Low-pressure steam curing combined with citric acid surface microporous treatment and nano-silica sol sealing process improves water permeability without sacrificing strength, while also constructing a barrier to prevent heavy metal migration.

[0048] Specifically, the principle of this invention is as follows: The technical principle of this invention is based on the concept of multi-level waste residue stabilization treatment and structural safety design. Through the system integration of multiple innovative technologies, the harmful components in industrial waste residue are fully stabilized.

[0049] In terms of waste residue stabilization, this invention employs a triple stabilization technology system, forming a multi-layered barrier at the physical, chemical, and molecular levels. First, the pyrolysis pretreatment, conducted at 550-650℃ under isolated or oxygen-limited conditions, utilizes a temperature-controlled thermodynamic transformation process to completely decompose and volatilize organic pollutants in the waste residue. Simultaneously, highly reactive heavy metal ions are converted into stable oxide crystals, fundamentally reducing the chemical activity and migration capacity of heavy metals. Second, the phosphoric acid solution immersion treatment utilizes the strong chemical affinity between phosphate ions and heavy metal ions to form phosphate mineral crystals with extremely low solubility. Through lattice encapsulation and chemical bonding, the heavy metals are firmly fixed, maintaining stability even under acidic conditions. Third, the composite modification with silane and titanate coupling agents chemically bonds with the hydroxyl groups on the waste residue surface at the molecular level, forming a hydrophobic protective network. This not only blocks direct contact between moisture and heavy metals but also enhances the interfacial compatibility between the waste residue and the cement matrix through molecular bridging, preventing the formation of interfacial microcracks. These three stabilization mechanisms work in a progressive and synergistic manner, from microscopic mineralogical transformation and mesoscopic crystal fixation to macroscopic interface closure, constructing a comprehensive and multi-level heavy metal migration blocking system.

[0050] In terms of structural safety design, this invention employs a deep protection strategy combining a double-layer structure and heavy metal migration control. The upper permeable layer utilizes a carefully designed formula and microporous structure to form a primary barrier against heavy metals. The lower support layer has higher density and more fly ash active components, enabling it to further trap potentially migrating heavy metals through physical adsorption and chemical fixation. A modified Apollonian sphere packing algorithm optimizes the pore structure, controls pore connectivity and migration channels, and reduces the likelihood of heavy metal migration through dominant flow paths. Simultaneously, the interlayer balance exponential function dynamically optimizes the thickness ratio of the upper and lower layers by comprehensively considering the potential migration distance and migration limitation threshold of heavy metals, ensuring that heavy metals cannot penetrate the entire brick structure even under the most extreme conditions.

[0051] In terms of molding and treatment, low-pressure steam curing technology promotes cement hydration reaction under mild conditions, forming a dense hydrated calcium silicate gel network, which provides an additional physical sealing effect; nano-silica sol surface treatment penetrates into the tiny pores on the brick surface to form a nano-scale dense protective layer, establishing a molecular-level barrier and completely blocking the last possible pathway for heavy metals to migrate to the outside world.

[0052] The above principles work together to form a complete protective system from material stabilization and structural barriers to surface sealing. This invention can fundamentally solve the technical problem of insufficient stabilization of industrial waste in the preparation of permeable bricks, and successfully produce industrial waste-based ecological permeable bricks with significantly improved environmental safety.

[0053] The following provides a specific embodiment 1 of the present invention, and the specific implementation of each step in this embodiment 1 is described in detail below.

[0054] The specific implementation of step S01 involves systematically pretreating industrial waste residue to transform it into environmentally safe, stabilized material. First, physical crushing is performed, using a jaw crusher to initially crush the waste residue to below 10 mm, followed by further crushing to below 5 mm using a hammer mill. During the crushing process, particle size is monitored in real time, and equipment parameters are adjusted to ensure uniform particle size. Next, the crushed waste residue is transferred to a pyrolysis furnace for pyrolysis under oxygen-isolated or limited-oxygen conditions. The furnace temperature is controlled within the range of 550 to 650°C, with a preferred temperature of 600°C, and the processing time is controlled within the range of 180 to 240 minutes, with a preferred time of 210 minutes. The organic matter decomposition rate during pyrolysis can be expressed as:

[0055] In the formula, r d k is the rate of organic matter decomposition, expressed in kilograms per cubic meter per second; k0 is the pre-exponential factor, with a value range of 10. 5 Up to 10 7 per second; Ea The activation energy is 80 to 120 kJ / mol; R is the gas constant, 8.314 J / mol K; T is the pyrolysis temperature in Kelvin; C is the organic matter concentration in kg / m³; and n is the reaction order, typically between 1 and 2.

[0056] After pyrolysis, the waste residue is cooled to room temperature and then transferred to the chemical treatment stage. It is soaked in a 3-5% (w / w) phosphoric acid solution with a liquid-to-solid ratio controlled at 5:1. The heavy metal stabilization efficiency during the phosphoric acid treatment process is calculated as follows:

[0057] In the formula, η s Heavy metal stabilization efficiency, expressed as a percentage; C in The leaching concentration of heavy metals before treatment is expressed in milligrams per liter; C out The concentration of heavy metals that can be leached after treatment is expressed in milligrams per liter.

[0058] The phosphate precipitation reaction formed during the stabilization process can be represented as: M n+ +nH3PO4→M(H2PO4) n +nH + ;

[0059] In the formula, M n+ This represents the heavy metal ions in the waste residue, where n is the valence state of the ion.

[0060] The soaked waste residue is washed three times, with a liquid-to-solid ratio of 6:1 each time and a stirring time of 10 minutes. The washing efficiency is calculated using the formula: E w =1-(1-r) n ;

[0061] In the formula, E w The total cleaning efficiency is expressed as a percentage; r is the efficiency of a single cleaning cycle, ranging from 0.5 to 0.7; n is the number of cleaning cycles, which is 3 in this embodiment.

[0062] After cleaning, the waste residue is placed in an oven at a temperature controlled between 105 and 110°C, preferably 108°C, and dried to a constant weight. The criterion for this drying is that the weight change is less than 0.1% when measured twice consecutively at 2-hour intervals. The purpose of this step is to increase the specific surface area of ​​the waste residue through physical crushing and to reduce the risk of heavy metal leaching through pyrolysis and phosphoric acid stabilization treatment, thus laying a safe foundation for the subsequent preparation of permeable bricks.

[0063] The specific implementation of step S02 involves surface modification treatment of the waste residue to improve the interfacial compatibility between the waste residue and the cement matrix and further stabilize heavy metals. First, a modifier solution is prepared by dissolving 2-4% by mass of a silane coupling agent and 0.5-1.5% by mass of a titanate coupling agent in anhydrous ethanol, with a total solution volume to waste residue mass ratio of 2:1. The solution is stirred at room temperature using a thermostatic magnetic stirrer for 30-60 minutes to ensure complete dissolution of the coupling agent and the formation of a homogeneous solution. Subsequently, the stabilized waste residue is immersed in the prepared solution for 4-6 hours, with stirring every 30 minutes to ensure reaction uniformity. The surface modification reaction of the coupling agent involves the bonding between hydroxyl groups and silane groups on the waste residue surface, and the surface reaction kinetic model can be expressed as:

[0064] In the formula, C s The concentration of the surface-bonded coupling agent is expressed in milligrams per square meter; t is the reaction time, expressed in hours; k r is the reaction rate constant, expressed in units of milligrams per square meter per hour, with a value ranging from 0.01 to 0.05; C max The maximum surface bonding capacity is expressed in milligrams per square meter, ranging from 2 to 5; C l This represents the concentration of the coupling agent in the solution, expressed in milligrams per milliliter.

[0065] The formula for calculating the degree of surface modification is:

[0066] In the formula, D m C represents the degree of surface modification, expressed as a percentage. s This represents the actual concentration of the binding coupling agent, expressed in milligrams per square meter; C max This represents the theoretical maximum bonding capacity, expressed in milligrams per square meter.

[0067] The bond stability index can be calculated using the following model:

[0068] In the formula, I bs α is the bonding stability index, dimensionless, ranging from 0 to 1; α is the proportionality coefficient, with a value of 1.2; β is the decay coefficient, with a value of 0.8; E h The bond energy is expressed in kilojoules per mole and is obtained through infrared spectroscopy analysis; E c The critical bonding energy is expressed in kilojoules per mole and is set to 50.

[0069] The key parameters for the surface modification reaction are calculated, including the specific surface area of ​​the waste residue, the concentration of the silane coupling agent, the reaction time, the reaction temperature, and the hydroxyl density on the waste residue surface. The hydroxyl density on the waste residue surface is obtained through infrared spectroscopy analysis and calculated using the following formula:

[0070] In the formula, ρ OH Surface hydroxyl density, in units of hydroxyl groups per square nanometer; A OH k represents the area of ​​the hydroxyl absorption peak in the infrared spectrum, expressed in terms of absorbance wavemultiplier. cal This is a correction factor, expressed in units of absorbance multiplied by wavenumber multiplied by square meter, with a value of 3.5 × 10⁻⁶. 18 S BET Specific surface area, expressed in square meters per gram, determined by nitrogen adsorption method.

[0071] After soaking, the waste residue was removed, and the filtration rate was controlled to minimize modifier loss. The residue was then transferred to a constant-temperature drying oven and dried at 80-90°C for 120-180 minutes. The drying process employed segmented temperature control technology, maintaining the temperature at 70°C for the initial 30 minutes before gradually increasing to the set temperature to prevent rapid solvent evaporation and uneven surface modification. The degree of surface modification was determined using Fourier transform infrared spectroscopy. The optimized process achieved over 90% surface coverage and improved heavy metal stability by 3-5 times.

[0072] The specific implementation of step S03 is to prepare a multi-layer structure formula for permeable bricks based on the functionally graded materials theory. First, each component material is accurately weighed. The upper permeable layer formula includes 40-50% modified waste residue, 20-30% coarse sand, 10-15% fly ash, 10-15% cement, 1-3% nano-silica, and 0.5-1% water-retaining agent. The lower support layer formula includes 30-35% modified waste residue, 30-35% coarse sand, 15-20% fly ash, 15-20% cement, and 1-2% nano-silica. The multi-layer structure formula design uses a material performance balance algorithm, represented by a performance weight matrix.

[0073]

[0074] In the formula, W is the performance weight matrix; w p1 w p2 w p3 w p4 These are the weights for the permeability, strength, durability, and environmental safety of the upper permeable layer, respectively; w s1 w s2 w s3 w s4 These are the weights for the permeability, strength, durability, and environmental safety of the lower support layer, respectively. The recommended weight for the upper permeable layer is w. p1 =0.4, w p2 =0.2, w p3 =0.2, w p4 =0.2; the recommended weight for the lower support layer is w.s1 =0.2, w s2 =0.4, w s3 =0.2, w s4 =0.2.

[0075] The formula performance scoring function is:

[0076] In the formula, S i The overall performance score for the i-th layer (i = p represents the upper layer, i = s represents the lower layer) ranges from 0 to 100; w ij P represents the weight of the i-th layer for the j-th performance item; ij is the standardized score of the j-th performance item in the i-th layer, with a value ranging from 0 to 100.

[0077] The performance standardization calculation formula is as follows:

[0078] In the formula, This is the original performance test data; This is the minimum acceptable value for this performance indicator; This is the ideal target value for this performance indicator.

[0079] The upper permeable layer is designed with high porosity as a priority, with a target porosity of 25% to 30% and a permeability coefficient greater than 0.1 cm / s. A water-retaining agent is added to enhance ecological function, with a target water retention rate of 15% to 20%. The lower support layer is designed with high strength as a priority, with a target compressive strength greater than 25 MPa, while maintaining a certain level of permeability to prevent water accumulation. The target permeability coefficient is 0.01 to 0.05 cm / s.

[0080] The specific implementation of step S04 involves preparing a multi-level porous structure material using optimized particle size distribution technology. First, the upper permeable layer material and the lower support layer material are prepared according to the formulation components. The materials are then sieved into five particle size grades using a standard sieving method: 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, and 0.15 mm. A modified Apollonian sphere packing algorithm is used to optimize the particle size distribution. This algorithm, based on the three-dimensional space filling theory, treats particles of each size as rigid spheres and iteratively calculates the porosity and packing density of different particle size combinations to solve for the optimal particle size distribution function. The optimization objective function is: F(x) = w1·P(x) + w2·S(x) + w3·C(x);

[0081] In the formula, F(x) is the objective function for particle size distribution optimization, with a numerical range of 0 to 1; x is the particle size distribution vector, x = (x1, x2, x3, x4, x5), where x iThe mass fraction of particles of size i represents the i-th particle size; P(x) is the porosity function, with a value ranging from 0 to 1; S(x) is the intensity function, with a value ranging from 0 to 1; C(x) is the connectivity function, with a value ranging from 0 to 1; w1, w2, and w3 are weighting coefficients, and satisfy w1 + w2 + w3 = 1. The recommended values ​​for the upper permeable layer are w1 = 0.5, w2 = 0.2, and w3 = 0.3, and the recommended values ​​for the lower support layer are w1 = 0.3, w2 = 0.5, and w3 = 0.2.

[0082] Porosity function calculation formula:

[0083] In the formula, ρ i denoted as the bulk density of particles of size i, expressed in grams per cubic centimeter.

[0084] Intensity function calculation formula:

[0085] In the formula, C d The bulk density is expressed in grams per cubic centimeter and is calculated using the following method: C d0 is the critical bulk density, expressed in grams per cubic centimeter, with a value of 1.4; k is the sensitivity coefficient, with a value of 5.

[0086] Connectivity function calculation formula:

[0087] In the formula, c ij The connectivity coefficient matrix between particles of size i and j is determined experimentally.

[0088] The optimization solution is implemented using a genetic algorithm, with the following constraints:

[0089]

[0090] x i ≥x i，min ;

[0091] x i ≤x i，max ;

[0092] In the formula, x i，min and x i，max These are the minimum and maximum allowable mass fractions of particles of the i-th particle size, respectively, with specific value ranges as follows: 2.36 mm particles account for 15 to 20%, 1.18 mm particles account for 25 to 30%, 0.6 mm particles account for 30 to 35%, 0.3 mm particles account for 15 to 20%, and 0.15 mm particles account for 5 to 10%.

[0093] Through the above optimization algorithm, the particle size distribution of the upper permeable layer material and the lower support layer material is optimized, and a multi-level pore structure is finally formed, including macropores of 100 to 500 micrometers for the main water permeability channels, mesopores of 10 to 100 micrometers for capillary adsorption, and micropores of 1 to 10 micrometers for water retention, forming a highly efficient water permeability and filtration network system.

[0094] The specific implementation of step S05 is to achieve the double-layer structure molding and interlayer balance optimization of permeable bricks. First, prepare the molding mold, coating its inner surface with a release agent to ensure smooth demolding after molding. Mix the lower support layer mixture prepared in step S04 with water at a mass ratio of 0.35 to 0.4, and stir using a forced mixer for 3 to 5 minutes at a stirring speed of 60 rpm to ensure the material is fully wetted and uniformly mixed. Pour the mixed lower layer material into the mold and compact it using a vibrating table at a vibration frequency of 40 Hz for 30 seconds to ensure the material is densely packed and reaches 60 to 70% of the mold's designed thickness. Then, prepare the upper permeable layer material by mixing the upper layer mixture prepared in step S04 with water at a mass ratio of 0.38 to 0.42, using the same mixing process to ensure uniform mixing. Pour the upper layer material into the mold containing the lower layer material and compact it again to 100% of the total designed thickness, forming a double-layer structure.

[0095] Immediately after molding, the interlayer balance exponent function is applied to calculate the rationality of the thickness ratio between the upper and lower layers. The interlayer balance exponent function is defined as follows:

[0096]

[0097] In the formula, I b The interlayer equilibrium index is dimensionless, with an optimal range of 0.9 to 1.1; k p The permeability coefficient of the upper layer is expressed in centimeters per second and is determined through a permeability test; k s The permeability coefficient of the lower layer is expressed in centimeters per second and is determined through a permeability test; h p The thickness of the upper layer, in millimeters, is determined through physical measurement; h s The thickness of the lower layer, in millimeters, is determined through physical measurement; f p The upper layer compressive strength, measured in megapascals (MPa), is obtained through pressure testing; f s The lower layer compressive strength, measured in megapascals (MPa), is obtained through pressure testing; D cr The critical protective layer thickness is expressed in millimeters and ranges from 10 to 15; L hm The potential migration distance of heavy metals, in millimeters, is assessed through leaching experiments; L crThe threshold value for heavy metal migration is in millimeters and ranges from 30 to 40. α1, α2, α3, and α4 are weighting coefficients that satisfy α1 + α2 + α3 + α4 = 1. The recommended values ​​are α1 = 0.3, α2 = 0.3, α3 = 0.2, and α4 = 0.2.

[0098] The first term of the interlayer balance index function represents the balance of permeability, the second term represents the balance of strength performance, the third term represents the adequacy of the protective layer thickness, and the fourth term represents the safety of heavy metal migration. When the interlayer balance index is between 0.9 and 1.1, it indicates that the optimal balance has been achieved. When it is greater than 1.1, the thickness of the upper layer needs to be reduced, and when it is less than 0.9, the thickness of the upper layer needs to be increased.

[0099] A layered iterative optimization scheme is adopted, and the thickness ratio update formula is: r n+1 =r n ·(2-I b，n );

[0100] In the formula, r n The thickness ratio of the upper and lower layers in the nth iteration is defined as follows: I b，n r is the interlayer equilibrium index calculated in the nth iteration. n+1 This is the updated thickness ratio between the upper and lower layers.

[0101] The iteration termination condition is: |I b，n -1|<0.1 or n>n max ;

[0102] In the formula, n max The maximum allowed number of iterations is 5.

[0103] Through 3 to 5 iterations of optimization, the interlayer balance index value is converged within the range of 1.0 ± 0.1, achieving a comprehensive balance between permeability, strength performance, and environmental safety performance. After molding, the bricks need to undergo preliminary curing by standing in an environment with a temperature of 20℃ and a relative humidity of over 95% for 4 hours to allow the bricks to acquire a certain initial strength.

[0104] The specific implementation of step S06 involves using a low-pressure steam curing process to promote cement hydration and improve the strength and durability of the permeable bricks. First, the formed bricks are transferred to a pre-curing chamber and pre-cured at 20-25°C for 24-36 hours. After pre-curing, the bricks are transferred to a steam curing chamber, where a programmed heating and cooling process is used for steam curing. During the heating phase, the temperature rise rate is controlled at 5°C per hour to prevent rapid heating that could cause cracking. Once the target temperature of 65-75°C is reached, it is maintained at a constant temperature. The relative humidity is controlled at 90-95%. The curing time is 72-96 hours. During the cooling phase, the temperature drop rate is controlled at 3°C ​​per hour to prevent thermal stress from causing microcracks.

[0105] The kinetic model of cement hydration reaction can be expressed as:

[0106] In the formula, α is the degree of hydration, dimensionless, with a numerical range of 0 to 1; t is time, in hours; k h is the reaction rate constant, expressed in hours, ranging from 0.01 to 0.1; n is the reaction order, with a value of 2; E h R is the apparent activation energy of the hydration reaction, expressed in kilojoules per mole, with a value ranging from 30 to 50; R is the gas constant, 8.314 joules per mole of Kelvin; and T is the curing temperature, expressed in Kelvin.

[0107] The intensity development model can be expressed as:

[0108] In the formula, f c (t) represents the compressive strength at time t, in megapascals (MPa); f c，∞ The theoretical maximum compressive strength is expressed in megapascals (MPa), with a value ranging from 30 to 40; α(t) is the degree of hydration at time t; α ∞ The theoretical maximum degree of hydration ranges from 0.8 to 0.9.

[0109] Formula for calculating the efficiency coefficient of steam curing temperature:

[0110] In the formula, η T T represents the temperature efficiency coefficient, ranging from 0 to 1; T is the actual curing temperature in degrees Celsius; T0 is the minimum effective curing temperature, taken as 15℃; T opt The optimal maintenance temperature is 70℃.

[0111] The uniformity of temperature and humidity distribution in the curing room is controlled in real time through a multi-point monitoring system to ensure that all bricks are subjected to consistent curing conditions. After curing, the bricks must undergo strength testing. The compressive strength should reach more than 85% of the design value, and the permeability coefficient should reach more than 90% of the design value before proceeding to the next process.

[0112] The specific implementation of step S07 involves surface micropore treatment and sealing to improve permeability and ensure environmental safety. First, a citric acid solution with a mass fraction of 10-15% is prepared, with the pH value controlled between 2.5 and 3.0. The solution is then uniformly sprayed onto the hardened brick surface using a spraying device, with a spraying volume of 200-250 ml per square meter and a spraying pressure controlled at 0.2 MPa, ensuring uniform distribution of the solution on the brick surface. The reaction between citric acid and cement hydration products can be represented as follows:

[0113] Ca(OH)2+H3C6H5O7→Ca(C6H5O7)+2H2O;

[0114] 3CaO·2SiO2·3H2O+2H3C6H5O7→3Ca(C6H5O7)+2SiO2+6H2O.

[0115] The surface micropore formation rate model can be expressed as:

[0116] In the formula, P is the surface porosity, dimensionless, with a value ranging from 0.2 to 0.4; t is the reaction time, in minutes; k p C is the pore formation rate constant, expressed in milliliters per milligram per minute, ranging from 0.005 to 0.01. acid S represents the concentration of the acid solution, expressed in milligrams per milliliter. max S represents the maximum soluble surface area, expressed in square millimeters per square millimeter; S represents the dissolved surface area, expressed in square millimeters per square millimeter.

[0117] After spraying, allow the solution to stand for 30 to 60 minutes to allow the acid to react fully. During this period, maintain an ambient temperature of 20 to 25°C, avoiding direct sunlight and wind to ensure a uniform reaction. After the reaction is complete, rinse the brick surface with clean water at a pressure of 0.3 MPa for 2 minutes to ensure that any residual acid and reaction products are completely removed. Allow the brick to air dry naturally for 2 hours, followed by a nano-silica sol surface sealing treatment.

[0118] Formula for calculating penetration depth during the sealing process of nano-silica sol:

[0119] In the formula, D p The depth of penetration is measured in millimeters; k i The correction factor is 0.6; γ is the surface tension of the liquid, in Newtons per meter, ranging from 0.02 to 0.03; θ is the contact angle, in degrees, ranging from 20 to 40; r is the average pore size, in micrometers, ranging from 0.1 to 1; t is the penetration time, in seconds; η is the sol viscosity, in Pascals per second, ranging from 0.001 to 0.003.

[0120] Formula for calculating heavy metal migration blocking efficiency:

[0121] In the formula, η b Blocking efficiency is expressed as a percentage; C out，b The concentration of heavy metals leaching after sealing treatment is expressed in milligrams per liter; C out，0 The concentration of heavy metal leaching without sealing treatment is expressed in milligrams per liter.

[0122] The treated bricks were dried at room temperature for 24 hours, after which permeability and heavy metal leaching tests were conducted to verify the treatment effect. The optimized surface treatment process can increase the permeability coefficient of the brick surface by 30 to 50%, while reducing the risk of heavy metal leaching by more than 90%, meeting the dual requirements of ecological permeability and environmental safety.

[0123] To better understand and implement this invention, the following is a specific application scenario of Example 2: In this example, converter steel slag from a steel plant is used as raw material to prepare ecological permeable bricks. The main components of the raw steel slag include calcium oxide (45.8%), silicon dioxide (15.2%), iron oxide (18.6%), magnesium oxide (5.3%), aluminum oxide (3.2%), manganese oxide (2.8%), and trace amounts of heavy metals such as chromium and lead. The steel slag has an uneven particle size distribution, with a maximum particle size of 15 mm. The main components and heavy metal contents are shown in Table 1.

[0124] Table 1. Main components and heavy metal content of raw steel slag

[0125] project content(%) project Content (mg / kg) CaO 45.8 chromium 1520 <![CDATA[SiO2]]> 15.2 lead 680 <![CDATA[Fe2O3]]> 18.6 nickel 420 MgO 5.3 Zinc 860 <![CDATA[Al2O3]]> 3.2 copper 380 MnO 2.8 vanadium 760 other 9.1 molybdenum 220

[0126] First, the steel slag is crushed using a PE400×600 jaw crusher to a particle size of less than 10 mm, followed by further crushing using a PC400×300 hammer crusher to a particle size not exceeding 5 mm. The crushed steel slag is then loaded into a tubular electric furnace and pyrolyzed under nitrogen protection at 600℃ for 210 minutes. After cooling to room temperature, the pyrolyzed waste residue is transferred to an enamel-lined reactor and soaked in a 4% phosphoric acid solution at a liquid-to-solid ratio of 5:1 for 30 hours. Following soaking, the residue is washed three times with deionized water and then dried at 108℃ to constant weight to obtain stabilized waste residue.

[0127] The stabilized waste residue underwent surface modification treatment. A modifier solution was prepared, comprising 3% silane coupling agent KH-550 and 1% titanate coupling agent TZ-33, dissolved in anhydrous ethanol, with a total solution volume to waste residue mass ratio of 2:1. After stirring to form a homogeneous solution, the stabilized waste residue was immersed in the solution for 5 hours, stirred every 30 minutes. The immersed waste residue was filtered and collected, then dried at 85℃ for 150 minutes to obtain modified waste residue. Infrared spectroscopy analysis confirmed that the surface modification degree reached 92%, and the surface hydroxyl density was 4.2 hydroxyl groups / nm. 2 .

[0128] Next, the multi-layer structure formula for permeable bricks is prepared. The double-layer structure of the ecological permeable brick is as follows: Figure 2 As shown in Table 2, the specific formulations of the upper permeable layer and the lower support layer are as follows:

[0129] Table 2. Composition of permeable brick upper and lower layers (by mass percentage)

[0130]

[0131]

[0132] According to the optimized particle size distribution technology, the upper permeable layer material and the lower support layer material were screened into five particle size grades. The screening results are shown in Table 3.

[0133] Table 3. Particle size distribution of upper and lower layer materials (mass percentage)

[0134] Particle size classification Upper permeable layer (%) Lower support layer (%) 2.36 mm 17 17 1.18 mm 28 28 0.6 mm 32 32 0.3 mm 18 18 0.15 mm 7 7 total 100 100

[0135] During brick preparation, the lower support layer mixture was first mixed with water at a mass ratio of 0.38 and stirred for 4 minutes. This mixture was then poured into a 240×120×60 mm mold and compacted to a thickness of 39 mm (65% of the total thickness). Subsequently, the upper permeable layer mixture was mixed with water at a mass ratio of 0.4 and stirred for 4 minutes. This mixture was then poured into the mold and compacted to a total thickness of 60 mm. The initial upper-lower layer thickness ratio was 7:13. Through three iterations of optimization, the final upper-lower layer thickness ratio was determined to be 3:7, achieving an interlayer balance index of 1.02.

[0136] After molding, the bricks are pre-cured at 23℃ for 30 hours, followed by steam curing at 70℃ and 93% relative humidity for 84 hours. After curing, the surface of the bricks is sprayed with a 12% citric acid solution, left to stand for 45 minutes, rinsed with water, and then sealed with 4% nano silica sol. After drying for 24 hours, the final product is obtained.

[0137] The performance indicators of the finished permeable bricks are shown in Table 4:

[0138] Table 4 Performance Test Results of Finished Permeable Bricks

[0139] Performance indicators upper layer lower level overall Standard requirements Permeability coefficient (cm / s) 0.13 0.04 0.09 ≥0.05 Compressive strength (MPa) 18.5 28.7 24.6 ≥20 Porosity (%) 28 16 20 ≥15 Water retention rate (%) 18 6 10 ≥8 Heavy metal leaching concentration (mg / L) <0.01 <0.01 <0.01 ≤0.05 Mass loss rate (%) after 25 freeze-thaw cycles 2.3 1.2 1.6 ≤3

[0140] Traditional industrial waste treatment technologies mainly employ cement solidification or vitrification, which suffer from high energy consumption, high costs, and significant risks of secondary pollution. Traditional permeable brick manufacturing techniques typically use a single material, making it difficult to balance permeability and strength, or employ simple porous structures that are prone to pore blockage and reduced strength, and are ineffective at effectively immobilizing heavy metals.

[0141] The layered composite structure design adopted in this invention solves the core problems of traditional technologies: the three-stage treatment process of pyrolysis-phosphoric acid stabilization-coupling agent modification significantly reduces the risk of heavy metal leaching; the modified Apollonian sphere packing algorithm is used to optimize particle size distribution, realizing a multi-level porous structure and ensuring a balance between permeability and strength; the interlayer balance exponential function is innovatively applied to optimize the ratio of upper and lower layers, enabling the permeable brick to simultaneously possess high permeability (0.09 cm / s) and high strength (24.6 MPa); the combination of surface micropore treatment and nano-silica sol sealing technology further improves permeability and ensures environmental safety, with heavy metal leaching concentration below 0.01 mg / L, which is below the standard limit.

[0142] It should be noted that the variables involved in this invention are explained in detail in Tables 5 and 6 below.

[0143] Table 5. Variable Explanation Table (Part 1)

[0144]

[0145]

[0146] Table 6. Variable Explanation Table (Part Two)

[0147]

[0148]

[0149] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an industrial waste residue-based ecological water-permeable brick, characterized in that, Comprise: S01, the industrial waste residue is pretreated, including crushing to particle size less than 5mm, treating at 550-650 DEG C for 180-240 minutes by pyrolysis method, then soaking in 3-5wt% phosphoric acid solution for 24-36 hours, after three times of washing, drying at 105-110 DEG C to constant weight, obtaining stabilized waste residue; S02, preparation of modifier, mixing 2-4wt% silane coupling agent and 0.5-1.5wt% titanate coupling agent in ethanol solution, stirring for 30-60 minutes to form a uniform solution, immersing the stabilized waste residue in the uniform solution for 4-6 hours, then taking out and drying at 80-90 DEG C for 120-180 minutes, obtaining modified waste residue; S03, preparing multi-layer structure formula, the upper water permeable layer formula is modified waste residue 40-50%, coarse sand 20-30%, fly ash 10-15%, cement 10-15%, nano-silicon dioxide 1-3%, water retaining agent 0.5-1%; the lower support layer formula is modified waste residue 30-35%, coarse sand 30-35%, fly ash 15-20%, cement 15-20%, nano-silicon dioxide 1-2%; S04, using optimized particle grading technology, the upper water permeable layer material and the lower support layer material are respectively sieved and mixed according to the ratio of 2.36mm 15-20%, 1.18mm 25-30%, 0.6mm 30-35%, 0.3mm 15-20%, 0.15mm 5-10%, to prepare upper and lower mixed materials with multi-level pore structure; S05, double-layer structure forming, first mixing and stirring the lower mixed material with 0.35-0.4wt% water for 3-5 minutes, pouring into the mold and compacting to 60-70% of the designed thickness, then mixing and stirring the upper mixed material with 0.38-0.42wt% water for 3-5 minutes, pouring into the mold and compacting to 100% of the total thickness, then adjusting the ratio of upper and lower thickness according to the calculation results of interlayer balance index function; Immediately after forming, the rationality of the upper and lower thickness ratio is calculated by interlayer balance index function, and the interlayer balance index function is defined as: ； wherein, is the interlayer balance index, dimensionless; is the upper layer permeability coefficient, in centimeters per second; is the lower layer permeability coefficient, in centimeters per second; is the upper layer thickness, in millimeters; is the lower layer thickness, in millimeters; is the upper layer compressive strength, in megapascals; is the lower layer compressive strength, in megapascals; is the critical protective layer thickness, in millimeters, with a value range of 10 to 15; is the heavy metal potential migration distance, in millimeters; is the heavy metal migration limit threshold, in millimeters, with a value range of 30 to 40; , , , is the weight coefficient, wherein, , , , ; S06, low-pressure steam curing of the formed brick body, first pre-curing at 20-25 DEG C for 24-36 hours, then steam curing at 65-75 DEG C and 90-95% relative humidity for 72-96 hours to form a coagulation hardened brick body; S07, surface micropore treatment, using 10-15wt% citric acid solution to spray the surface of the coagulation hardened brick body, standing for 30-60 minutes and then washing with water to form additional micropore structure, improving water permeability, and using nano-silica sol for surface sealing treatment to prevent heavy metal leaching, obtaining the final industrial waste residue-based ecological permeable brick; The ratio in steps S03 and S04 is mass percentage. Wherein, when the interlayer balance index is between 0.9 to 1.1, it indicates that the best balance state is reached, greater than 1.1, the upper layer thickness needs to be reduced, less than 0.9, the upper layer thickness needs to be increased.

2. The method of claim 1, wherein, After the double-layer structure is formed, a layered iteration optimization scheme is adopted, first, a double-layer brick structure is established based on the initial formula, after the physical parameters are measured, the interlayer balance index function is introduced to calculate the interlayer balance index value, if the interlayer balance index value is not in the best interval, the ratio of the upper layer thickness and the lower layer thickness and the formula parameters are adjusted, and then it is prepared and tested again, through 3 to 5 iterations, the interlayer balance index value converges to the range of 1.0±0.

1.

3. The method of claim 2, wherein, The optimized particle size distribution technology applies the three-dimensional sphere packing principle for optimization, specifically, a modified Apollonian sphere packing algorithm is adopted, through iterative filling of the gap between particles of different sizes, the balance between porosity and strength is realized, and the optimal particle size distribution function is solved.

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