Preparation method of industrial waste residue-based ecological water permeable brick

Abstract

The invention provides a preparation method of an industrial waste residue-based ecological water permeable brick, and belongs to the technical field of industrial waste residue reutilization, and the preparation method comprises the following steps: firstly, changing the form of heavy metal into stable oxide through a pyrolysis method, and soaking with a phosphoric acid solution to form an insoluble phosphate compound to realize deep pre-stabilization of waste residues; then surface modification is carried out, and a hydrophobic protection network is formed on the molecular level; designing an upper permeable layer and a lower supporting layer according to an optimization formula, optimizing grain composition by using a modified Aboronia sphere stacking algorithm, forming by adopting a double-layer structure, and accurately regulating and controlling the thickness proportion of the upper layer and the lower layer through an interlayer equilibrium exponential function; performing low-pressure steam curing to form a compact hydrated calcium silicate gel network; and finally, citric acid solution micropore treatment and nano silica sol sealing treatment are carried out, a molecular-level protection barrier is constructed, and the technical problem that the stabilization of the waste residues is not enough when the water permeable brick is prepared from the industrial waste residues is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial waste residue recycling, and in particular relates to a method for preparing industrial waste residue-based ecological permeable bricks. Background Art

[0002] Permeable bricks, as a crucial component of urban sponge systems, play a key role in alleviating urban waterlogging, replenishing groundwater, and improving the urban ecological environment. Traditional permeable bricks are primarily made from natural aggregates and cement-based materials. However, with resource shortages and increasing environmental protection requirements, the use of industrial waste residues to replace some of the raw materials in the production of permeable bricks has become a research hotspot. Existing technologies typically use high-temperature sintering, cement gelation, or organic resin bonding to produce permeable bricks from industrial waste residues for use in urban road paving, parks, plazas, parking lots, and other locations. However, existing technologies for producing permeable bricks based on industrial waste residues face serious challenges in waste residue stabilization. First, conventional physical encapsulation methods have limited effectiveness in immobilizing heavy metals in the waste residues. Over long-term use, moisture intrusion can lead to the gradual leaching of heavy metals, causing secondary pollution. Second, single chemical stabilizer treatments are unable to fully address the complex and diverse heavy metal composition of the waste residues, resulting in incomplete stabilization. Third, existing surface modification technologies fail to effectively block contact between the waste residues and external moisture, resulting in the migration of heavy metals into the environment through the pore network, posing potential ecological risks. The core challenge for achieving safe resource utilization of industrial waste residue-based permeable bricks lies in thoroughly resolving the issue of stabilizing harmful components in the waste residue. Existing technologies struggle to achieve comprehensive stabilization with single treatment methods and simple structural designs. This is especially true when permeable bricks are exposed to complex environmental conditions for long periods of time, where the stabilization effect significantly diminishes. There is an urgent need to develop a multi-layered, coordinated stabilization technology system and optimized structural design solutions to address the technical bottleneck of insufficient waste residue stabilization at the source. In other words, existing technologies for producing permeable bricks from industrial waste residue present the technical problem of insufficient waste residue stabilization. Summary of the Invention

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

[0004] The present invention is implemented as follows: The present invention provides a preparation method of industrial waste residue-based ecological permeable bricks, including: subjecting industrial waste residue to thermal decomposition and phosphoric acid solution immersion treatment to achieve pre-stabilization of the waste residue; using a mixed modification of a silane coupling agent and a titanate coupling agent to form a hydrophobic protection network at the molecular level; designing the upper permeable layer and the lower support layer materials according to an optimized formula; using optimized particle grading technology to adjust the proportion of particles of different particle sizes; adopting a double-layer structure to form, and adjusting the thickness ratio of the upper and lower layers through an interlayer balance index function; forming a condensed and 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] Among them, the step of pretreating the industrial waste residue is specifically to crush the industrial waste residue to a particle size of less than 5 mm, treat it by pyrolysis at 550 to 650 ° C for 180 to 240 minutes, then soak it in a phosphoric acid solution with a mass fraction of 3 to 5% for 24 to 36 hours, and after three washings, dry it at 105 to 110 ° C to constant weight to obtain stabilized waste residue.

[0006] The step of modifying the waste residue by mixing a silane coupling agent with a titanate coupling agent is as follows: mixing a silane coupling agent with a mass fraction of 2 to 4% and a titanate coupling agent with a mass fraction of 0.5 to 1.5% in an ethanol solution, stirring for 30 to 60 minutes to form a uniform solution, immersing the stabilized waste residue in the uniform solution for 4 to 6 hours, taking it out, and drying it at 80 to 90° C. for 120 to 180 minutes to obtain modified waste residue.

[0007] Among them, the formula of the upper permeable layer is 40 to 50% modified waste residue, 20 to 30% coarse sand, 10 to 15% fly ash, 10 to 15% cement, 1 to 3% nano-silicon dioxide, and 0.5 to 1% water-retaining agent; the formula of the lower support layer is 30 to 35% modified waste residue, 30 to 35% coarse sand, 15 to 20% fly ash, 15 to 20% cement, and 1 to 2% nano-silicon dioxide.

[0008] Among them, the optimized particle grading technology specifically involves screening and mixing the upper permeable layer material and the lower support layer material according to the ratio of 2.36 mm accounting for 15 to 20%, 1.18 mm accounting for 25 to 30%, 0.6 mm accounting for 30 to 35%, 0.3 mm accounting for 15 to 20%, and 0.15 mm accounting for 5 to 10%, to prepare upper and lower layer mixtures with multi-level pore structures.

[0009] Among them, the steps of forming the double-layer structure are specifically: first mixing the lower layer mixture with water in a mass ratio of 0.35 to 0.4 for 3 to 5 minutes, pouring it into a mold and compacting it to 60 to 70% of the designed thickness, and then mixing the upper layer mixture with water in a mass ratio of 0.38 to 0.42 for 3 to 5 minutes, pouring it into a mold and compacting it to a total thickness of 100%.

[0010] Among them, the input parameters of the interlayer balance index function include the upper layer permeability coefficient, the lower layer permeability coefficient, the upper layer compressive strength, the lower layer compressive strength, the upper layer thickness, the total thickness, the potential migration distance of heavy metals, and the heavy metal migration limit threshold; the output of the interlayer balance index 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 is 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] Among them, after the double-layer structure is formed, a layered iterative optimization scheme is adopted. First, the double-layer brick structure is established based on the initial formula. After measuring the various physical parameters, the interlayer balance index function is entered to calculate the interlayer balance index value. If the interlayer balance index value is not in the optimal range, the ratio of the upper layer thickness to the lower layer thickness and the formula parameters are adjusted, and the system is re-prepared and tested. After 3 to 5 iterative optimizations, the interlayer balance index value converges to the range of 1.0±0.1.

[0013] Among them, the optimized particle grading technology applies the three-dimensional sphere packing principle for optimization, specifically adopting the modified Apollonia sphere packing algorithm to iteratively fill the gaps between particles of different particle sizes to achieve a balance between porosity and strength and solve the optimal particle size distribution function.

[0014] The present invention combines superheated decomposition and phosphoric acid stabilization pretreatment with coupling agent surface modification to achieve comprehensive stabilization of heavy metals in waste slag. A double-layer structure design and optimized particle grading technology create a microstructure that inhibits heavy metal migration. Low-pressure steam curing and surface micropore treatment create a brick body with long-term stabilization. This method fundamentally addresses the key drawback of conventional waste slag stabilization techniques. First, thermal pretreatment at 550 to 650°C changes the form of heavy metals into stable oxides, phosphating treatment forms insoluble phosphate complexes to firmly lock the heavy metals in the crystal lattice, and silane and titanate coupling agent modification forms a hydrophobic protective layer at the molecular level. The triple protection system blocks the leaching pathways of heavy metals from all aspects of physical, chemical and surface microstructure. Secondly, the differentiated design of the upper and lower layer structure formulas and the optimization of the interlayer balance index function ensure that the migration distance of heavy metals is controlled within the safety threshold. Thirdly, the surface sealing treatment of nano-silica sol forms a molecular-level protective barrier, which further improves the long-term stability and solves the technical problem of insufficient stabilization of waste slag in the preparation of permeable bricks from industrial waste slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the method of the present invention.

[0016] Figure 2 Schematic diagram of the double-layer structure of the ecological permeable brick obtained in Example 2. DETAILED DESCRIPTION

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

[0018] like Figure 1 FIG. 1 is a flow chart of a method for preparing an industrial waste residue-based ecological permeable brick provided by the present invention. The method comprises the following steps:

[0019] S01. Pre-treating the industrial waste residue, including crushing it 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 3 to 5% by mass phosphoric acid solution 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;

[0020] S02. Preparing a modifier, mixing 2 to 4% by mass of a silane coupling agent and 0.5 to 1.5% by mass of a titanate coupling agent in an ethanol solution, stirring for 30 to 60 minutes to form a uniform solution, immersing the stabilized waste residue in the uniform solution for 4 to 6 hours, then removing the solution, and drying the solution at 80 to 90° C. for 120 to 180 minutes to obtain a modified waste residue;

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

[0022] S04. Using optimized particle grading technology, the upper permeable layer material and the lower support layer material are sieved and mixed in a ratio of 2.36 mm (15-20%), 1.18 mm (25-30%), 0.6 mm (30-35%), 0.3 mm (15-20%), and 0.15 mm (5-10%), respectively, to prepare an upper layer mixture and a lower layer mixture having a multi-level pore structure;

[0023] S05. Perform double-layer structure molding: 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 a 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 a 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 calculation result of the interlayer balance index function;

[0024] S06. Perform low-pressure steam curing on the formed brick body, first pre-curing at 20 to 25° C. for 24 to 36 hours, and then steam curing at 65 to 75° C. and 90 to 95% relative humidity for 72 to 96 hours to form a coagulated and hardened brick body;

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

[0026] Among them, the pyrolysis method specifically refers to a method of heating industrial waste residue in an airless or oxygen-limited environment to decompose and volatilize organic matter, while changing the form of heavy metals into stable oxide forms, thereby reducing the activity of heavy metals and the risk of leaching;

[0027] Among them, stabilized waste residue specifically refers to waste residue materials that have been physically crushed and chemically treated, with heavy metal elements fixed in mineral lattices or forming insoluble phosphate complexes, thereby reducing environmental risks;

[0028] Among them, modified waste residue specifically refers to waste residue materials whose surface properties have changed after being treated with a coupling agent, and whose compatibility with the matrix material has been improved and whose heavy metal stability has been enhanced;

[0029] The multi-level pore structure specifically refers to the existence of interconnected pores of different scales, namely micron, submicron and nanometer, inside the brick, forming a network structure that combines high permeability with high filterability.

[0030] Among them, the optimized particle grading technology specifically refers to a ratio optimization method that controls the distribution of particles of different particle sizes in the mixture to form the best void ratio between particles, thereby ensuring sufficient permeability and maintaining structural strength.

[0031] Among them, low-pressure steam curing specifically refers to a process method that uses saturated steam to promote cement hydration reaction under low temperature and pressure conditions to form 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 silicon dioxide particles with a diameter of 5 to 20 nanometers, which can penetrate into the tiny pores on the surface of the brick, forming a dense protective layer and blocking the migration path of heavy metal ions;

[0033] Among them, there is a chemical mechanism for the modification process of step S02, the coupling agent surface reaction involves the bonding between the hydroxyl groups on the waste residue surface and the silane groups, the surface modification reaction is used to calculate the surface coverage and reaction efficiency, the input includes the waste residue specific surface area, the silane coupling agent concentration, the reaction time, the reaction temperature, and the waste residue surface hydroxyl density, the waste residue specific surface area is measured by nitrogen adsorption method, the silane coupling agent concentration is determined by the formula, the reaction time is controlled by the process, the reaction temperature is controlled by the heating equipment, and the waste residue surface hydroxyl density is obtained by infrared spectroscopy analysis, and the output is the surface modification degree and the bonding stability index, the surface modification degree is used to determine the coupling agent dosage, and the bonding stability index is used to predict the chemical stability of the modified waste residue during use;

[0034] The optimized particle grading technology in step S04 is optimized by applying the three-dimensional sphere packing principle. Specifically, a modified Apollonia sphere packing algorithm is used to iteratively fill the gaps between particles of different sizes to achieve a balance between porosity and strength and solve the optimal particle size distribution function. The particle size distribution parameter is the optimization parameter and is dynamically adjusted according to the permeability requirement.

[0035] Among them, the interlayer balance index function is defined as a mathematical expression of the comprehensive performance balance of the upper and lower layers. The input parameters of the interlayer balance index function include the upper layer permeability coefficient, the lower layer permeability coefficient, the upper layer compressive strength, the lower layer compressive strength, the upper layer thickness, the total thickness, the potential migration distance of heavy metals, and the heavy metal migration limit threshold. The upper layer permeability coefficient and the lower layer permeability coefficient are determined by permeation experiments, the upper layer compressive strength and the lower layer compressive strength are obtained by pressure testing, the upper layer thickness and the total thickness are determined by physical measurements, and the heavy metal potential migration distance and the heavy metal migration limit threshold 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 is reached. When it is greater than 1.1, the upper layer thickness needs to be reduced, and when it is less than 0.9, the upper layer thickness 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 inserting it into the interlayer balance index function. If the interlayer balance index value is not in the optimal range, the ratio of the upper layer thickness to the lower layer thickness and the formula parameters are adjusted, and the material is re-prepared and tested. After 3 to 5 iterative optimizations, the interlayer balance index value converges to the range of 1.0±0.1, achieving a comprehensive balance between permeability, strength performance and environmental safety performance.

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

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

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

[0040] The specific implementation of step S01 involves systematically pre-treating industrial waste slag to transform it into an environmentally safe, stabilized material. First, physical pulverization is performed, using a jaw crusher to initially crush the slag to less than 10 mm. Subsequently, a hammer mill is used to further crush it to less than 5 mm. During the crushing process, particle size is monitored in real time and equipment parameters are adjusted to ensure particle size uniformity. The crushed slag is then transferred to a pyrolysis furnace for pyrolysis in an oxygen-free or oxygen-limited environment. The furnace temperature is controlled between 550 and 650°C, preferably 600°C, and the treatment time is controlled between 180 and 240 minutes, preferably 210 minutes. Under these conditions, organic matter is fully decomposed and volatilized, while heavy metals are oxidized to a stable form. The pyrolyzed slag is cooled to room temperature and then transferred to a chemical treatment step, where it is soaked in a 3 to 5% by mass phosphoric acid solution, preferably at a concentration of 4%, for 24 to 36 hours, preferably 30 hours, with a liquid-to-solid ratio of 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, which significantly reduce the activity of heavy metals. The soaked waste residue needs to be washed three times, with a liquid-to-solid ratio of 6:1 and a stirring time of 10 minutes each time to remove residual acidic substances and soluble salts. After washing, the waste residue is placed in an oven with a temperature controlled at 105 to 110°C, preferably 108°C, and dried to constant weight. The judgment standard is that the weight change is less than 0.1% in two consecutive measurements with an interval of 2 hours. The purpose of this step is to increase the specific surface area of ​​the waste residue by physical crushing, reduce the risk of heavy metal leaching by pyrolysis and phosphoric acid stabilization, and lay a safe foundation for the subsequent preparation of permeable bricks.

[0041] The specific implementation method of step S02 is to perform surface modification treatment on the waste residue to improve the interfacial compatibility between the waste residue and the cement matrix and further stabilize the heavy metals. First, prepare a modifier solution, dissolve 2 to 4% of a silane coupling agent by mass and 0.5 to 1.5% of a titanate coupling agent by mass in anhydrous ethanol, the preferred concentration of the silane coupling agent is 3%, the preferred concentration of the titanate coupling agent is 1%, and the total volume of the solution to the waste residue mass ratio is 2:1. Use a constant temperature magnetic stirrer to stir at room temperature for 30 to 60 minutes, preferably 45 minutes, and a stirring rate of 300 revolutions per minute to ensure that the coupling agent is completely dissolved and a uniform solution is formed. The stabilized waste residue is then immersed in the prepared solution for 4 to 6 hours, preferably 5 hours, and stirred every 30 minutes to ensure the uniformity of the reaction. The surface modification reaction that occurs during the soaking process is based on interfacial chemistry theory. The alkoxy groups in the silane coupling agent molecules condense with the hydroxyl groups on the waste residue surface, forming chemical bonds. Simultaneously, the organic groups of the silane molecules extend outward, increasing the surface's hydrophobicity and organic compatibility. After soaking, the waste residue is removed and the filtration rate is controlled to minimize modifier loss. The residue is then transferred to a constant-temperature drying oven and dried at 80 to 90°C for 120 to 180 minutes, preferably 85°C, for a preferred drying time of 150 minutes. The drying process utilizes a staged temperature control technique, initially maintaining the temperature at 70°C for 30 minutes before increasing to the set temperature to prevent rapid solvent evaporation and uneven surface modification. The degree of surface modification is determined by potassium bromide tablet Fourier transform infrared spectroscopy, and the silane bonding rate is calculated. The optimized process achieves surface coverage exceeding 90%, with heavy metal stability increased by 3 to 5 times. After drying, the modified waste residue must be sealed to prevent hydrolysis of surface groups caused by moisture in the air.

[0042] The specific implementation of step S03 is to prepare a multi-layer structure formula of permeable bricks based on the theory of functional gradient materials. First, accurately weigh the various components. The upper permeable layer formula includes 40 to 50% modified waste slag, 20 to 30% coarse sand, 10 to 15% fly ash, 10 to 15% cement, 1 to 3% nano-silicon dioxide, and 0.5 to 1% water retaining agent. The preferred ratio is 45% modified waste slag, 25% coarse sand, 12% fly ash, 12% cement, 2% nano-silicon dioxide, and 0.8% water retaining agent. The lower support layer formula includes 30 to 35% modified waste slag, 30 to 35% coarse sand, 15 to 20% fly ash, 15 to 20% cement, and 1 to 2% nano-silicon dioxide. The preferred ratio is 32% modified waste slag, 32% coarse sand, 18% fly ash, 17% cement, and 1.5% nano-silicon dioxide. The multi-layer structure formulation was designed using a material performance balance algorithm, comprehensively considering four dimensions: permeability, strength, durability, and environmental safety. The optimal ratio was determined through orthogonal testing. The upper permeable layer was designed to prioritize high porosity, with a target porosity of 25-30% and a permeability greater than 0.1 cm / s. A water-retaining agent was added to enhance ecological function, with a target water retention of 15-20%. The lower support layer was designed to prioritize high strength, with a compressive strength target greater than 25 MPa while maintaining a certain level of permeability to prevent water accumulation, with a target permeability of 0.01-0.05 cm / s. Fly ash is used in different proportions in the two layers. Based on pozzolanic reaction theory, a lower proportion is used in the upper layer to maintain the pore structure, while a higher proportion is used in the lower layer to enhance later-stage strength and erosion resistance. Nanosilica, added as an active material, fills microscopic pores and promotes hydration, improving interfacial bonding and material density. The two-layer structure creates a physical and chemical functional gradient, ensuring the synergistic optimization of the overall performance of the permeable brick.

[0043] The specific implementation method of step S04 is to prepare multi-level porous structure materials using optimized particle grading technology. First, prepare the upper permeable layer material and the lower support layer material according to the formula components, and use the standard screening method to screen the materials into five particle size grades: 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm and 0.15 mm. The screening process uses a mechanical vibration screening device, the vibration frequency is controlled at 50 Hz, and the vibration time is 15 minutes to ensure complete screening. The optimal particle size distribution is calculated according to the modified Apollonia sphere packing algorithm. The algorithm is based on the three-dimensional space filling theory and regards particles of each particle size as rigid spheres. The void ratio and packing density of different particle size combinations are iteratively calculated to solve 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 prepared in a ratio of 2.36 mm (15-20%), 1.18 mm (25-30%), 0.6 mm (30-35%), 0.3 mm (15-20%), and 0.15 mm (5-10%), with a preferred ratio of 2.36 mm (17%), 1.18 mm (28%), 0.6 mm (32%), 0.3 mm (18%), and 0.15 mm (7%). The lower support layer material is prepared using the same particle size grading ratio, but the composition of each particle size grade follows the lower layer formulation in step S03. The particle grading 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 within the brick body. This includes macropores ranging from 100 to 500 microns for primary permeable channels, mesopores ranging from 10 to 100 microns for capillary adsorption, and micropores ranging from 1 to 10 microns for water retention, forming a highly efficient permeable and filtration network system. Materials that have completed grading optimization must be stored in a sealed manner to avoid stratification or segregation.

[0044] The specific implementation method of step S05 is to achieve the double-layer structure forming and interlayer balance optimization of permeable bricks. First, prepare the forming mold and coat the inner surface with a release agent to ensure that the brick body can be smoothly demolded after forming. Mix the lower support layer mixture prepared in step S04 with water in a mass ratio of 0.35 to 0.4, preferably a water-to-material ratio of 0.38, and use a forced mixer to stir for 3 to 5 minutes at a stirring rate of 60 revolutions per minute to ensure that the material is fully moistened and evenly mixed. The mixing uniformity is evaluated by sampling and testing the distribution state of the cement slurry, and the coefficient of variation is controlled below 5%. Pour the mixed lower layer material into the mold and vibrate it using a vibration table with a vibration frequency of 40 Hz and a vibration time of 30 seconds to fill the material densely and reach 60 to 70% of the designed thickness of the mold, preferably with a compaction degree of 65%. Next, prepare the upper permeable layer material. The upper layer mixture prepared in step S04 is mixed with water at a mass ratio of 0.38 to 0.42, preferably a water-to-material ratio of 0.4. The same mixing process is used to ensure uniform mixing. The upper layer material is poured into a mold containing the existing lower layer material and vibrated again to 100% of the total design thickness, forming a two-layer structure. Immediately after forming, an interlayer balance index function is applied to calculate the rationality of the upper and lower layer thickness ratio. This function comprehensively considers permeability, strength, and environmental safety. Input parameters include the permeability coefficient, compressive strength, and heavy metal migration characteristics of the upper and lower layers, and the output parameter is the interlayer balance index value. An interlayer balance index value between 0.9 and 1.1 indicates optimal balance. If it is greater than 1.1, the upper layer thickness should be reduced, and if it is less than 0.9, the upper layer thickness should be increased. The preferred upper and lower layer thickness ratio is 3:7. This ratio is determined through a layered iterative optimization scheme, which involves fine-tuning the thickness ratio and formulation three to five times to ultimately converge the interlayer balance index value within a range of 1.0±0.1. After forming, the bricks need to be initially cured and placed in an environment with a temperature of 20°C and a relative humidity of more than 95% for 4 hours to allow the bricks to gain a certain initial strength and prepare for subsequent curing.

[0045] The specific implementation method of step S06 is to use a low-pressure steam curing process to promote the cement hydration reaction and improve the strength and durability of the permeable bricks. First, the formed brick body is transferred to the pre-curing room and pre-cured at 20 to 25°C for 24 to 36 hours, preferably at 23°C, and preferably for 30 hours. A constant temperature and humidity control system is used in the pre-curing stage, and the relative humidity is maintained at above 90% to avoid shrinkage cracks caused by water loss on the surface of the brick body. During the pre-curing period, the brick body initially solidifies and hardens, forming sufficient strength to withstand the temperature stress in the subsequent steam curing process. After the pre-curing is completed, the brick body is transferred to the steam curing room and steam cured using a program-controlled heating and cooling process. During the heating phase, the temperature increase rate is controlled at 5°C per hour to prevent rapid temperature increases that could cause cracking in the bricks. After reaching the target temperature of 65 to 75°C, the temperature is maintained constant, preferably at 70°C. The relative humidity is controlled between 90 and 95%, preferably 93%. The curing time is 72 to 96 hours, preferably 84 hours. During the cooling phase, the temperature decrease rate is controlled at 3°C ​​per hour to prevent thermal stress-induced microcracking. The steam curing process is based on the principles of cement hydration kinetics. Appropriate temperature and humidity conditions accelerate the surface hydration reaction 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 monitored in real time by a multi-point monitoring system to ensure consistent curing conditions for all bricks. After curing, the bricks undergo strength testing. Compressive strength must exceed 85% of the design value, and permeability must exceed 90% of the design value before proceeding to the next step. If these values ​​are not met, the curing time may need to be extended or the curing parameters adjusted.

[0046] The specific implementation of step S07 involves treating and sealing the surface micropores to improve water permeability and ensure environmental safety. First, prepare a citric acid solution with a mass fraction of 10 to 15%, preferably 12%, and control the pH of the solution between 2.5 and 3.0. Use a spray device to evenly spray the hardened brick surface at a rate of 200 to 250 ml per square meter and a pressure of 0.2 MPa to ensure that the solution is evenly distributed on the brick surface. Citric acid, as an organic weak acid, selectively dissolves 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 and creates an additional microporous structure on the brick surface. After spraying, allow the solution to stand for 30 to 60 minutes, preferably 45 minutes, to allow the acid solution to fully react. During this standing period, maintain an ambient temperature of 20 to 25°C and avoid 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 acidic substances and reaction products are completely removed. The bricks are then air-dried for 2 hours before being treated with a nano-silica sol surface sealant. A nano-silica sol solution is prepared with a concentration of 3 to 5%, preferably 4%, and a nano-silica particle size of 10 to 15 nanometers. The sol is evenly applied to the brick surface by dipping or spraying, using a dosage of 150 to 200 milliliters per square meter. The nano-silica sol penetrates the micropores on the brick surface through capillary permeation and forms a network structure through a polycondensation reaction, forming a nanoscale protective layer on the inner wall of the pores, blocking the migration channels of heavy metals without affecting the passage of water. The treated bricks are dried at room temperature for 24 hours. After completion, water permeability tests and heavy metal leaching tests are performed to verify the treatment effect. The optimized surface treatment process can increase the water 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.

[0047] It should be noted that the industrial waste residue-based ecological permeable bricks of the present invention achieve 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, and realizes the transformation and fixation of heavy metal forms through a dual pretreatment process of pyrolysis and phosphoric acid stabilization, fundamentally reducing environmental risks. The coupling agent surface modification technology establishes a chemical bonding bridge between the waste residue and the matrix material, enhances the interfacial bonding force and further encapsulates heavy metals. The innovative multi-level pore structure design, with the help of a modified Apollonia sphere stacking algorithm, enables the permeable bricks to simultaneously have a micron, submicron and nanometer-level interconnected pore network, forming a functional structure that unifies high permeability and high filterability. The double-layer structure design is combined with the iterative optimization of the interlayer balance exponential function to achieve the synergistic effect of high permeability of the upper layer and high bearing capacity of the lower layer. By dynamically adjusting the interlayer thickness ratio and formula parameters, the permeability, strength performance and environmental safety performance are achieved to the optimal balance point. Low-pressure steam curing combined with citric acid surface micropore treatment and nano-silica sol sealing technology improves water permeability without sacrificing strength, while building a barrier to heavy metal migration.

[0048] Specifically, the principle of the present invention is: the technical principle of the present invention is based on the multi-level waste slag stabilization treatment and structural safety design concept, and through the systematic integration of multiple innovative technologies, the comprehensive stabilization of harmful components in industrial waste slag is achieved.

[0049] In terms of waste residue stabilization, the present invention adopts a triple stabilization technology system to form a multi-level barrier at the physical, chemical, and molecular levels. First, pyrolysis pretreatment, under isolated or oxygen-limited conditions at 550 to 650°C, completely decomposes and volatilizes organic pollutants in the waste residue through a temperature-controlled thermodynamic conversion process. At the same time, highly active heavy metal ions are converted into stable oxide crystals, fundamentally reducing the chemical activity and migration ability of heavy metals. Second, phosphoric acid solution immersion treatment utilizes the strong chemical affinity between phosphate and heavy metal ions to form phosphate mineral crystals with extremely low solubility. The heavy metals are firmly fixed through the dual effects of lattice wrapping and chemical bonding, and can remain stable even under acidic conditions. Third, the composite modification of 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 progress layer by layer and work synergistically, from microscopic mineralogical transformation, mesoscopic crystal fixation to macroscopic interface closure, to build a comprehensive, multi-level heavy metal migration blocking system.

[0050] In terms of structural safety design, the present invention adopts a deep protection strategy of double-layer structure and heavy metal migration control. The upper permeable layer adopts a carefully designed formula and microporous structure to form a primary barrier layer for heavy metals; the lower support layer has a higher density and more fly ash active components, which can further intercept heavy metals that may migrate through physical adsorption and chemical fixation. The modified Apollonia sphere packing algorithm optimizes the pore structure, controls pore connectivity and migration channels, and reduces the possibility of heavy metals migrating through dominant flow paths. At the same time, the interlayer balance index function dynamically optimizes the thickness ratio of the upper and lower layers by comprehensively considering the potential migration distance of heavy metals and the migration limit threshold, ensuring that heavy metals cannot penetrate the entire brick structure even under the most extreme conditions.

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

[0052] The above principles work together to form a complete protection system from material stabilization, structural barrier to surface closure, which enables the present invention to fundamentally solve the technical problem of insufficient waste stabilization in the preparation of permeable bricks from industrial waste slag, and successfully prepare industrial waste slag-based ecological permeable bricks with significantly improved environmental safety.

[0053] A specific embodiment 1 of the present invention is provided below. The specific implementation of each step in this embodiment 1 is described in detail as follows.

[0054] The specific implementation method of step S01 is to carry out systematic pretreatment of industrial waste slag to transform it into an environmentally safe stabilized material. First, physical crushing treatment is carried out, and a jaw crusher is used to initially crush the waste slag to less than 10 mm, and then a hammer crusher is used to further crush it to less than 5 mm. During the crushing process, the particle size is monitored in real time and the equipment parameters are adjusted to ensure the uniformity of the particle size. The crushed waste slag is then transferred to a pyrolysis furnace and pyrolysis treatment is carried out under oxygen isolation or oxygen-limited conditions. The furnace temperature is controlled in the range of 550 to 650°C, preferably at 600°C, and the processing time is controlled in the range of 180 to 240 minutes, preferably at 210 minutes. The decomposition rate of organic matter during the pyrolysis process can be expressed as:

[0055] Where r d is the decomposition rate of organic matter, in kilograms per cubic meter per second; k0 is the pre-exponential factor, with a value range of 10 5 to 10 7 per second; Ea is the activation energy, ranging from 80 to 120 kilojoules per mole; R is the gas constant, 8.314 joules per mole Kelvin; T is the pyrolysis temperature in Kelvin; C is the organic matter concentration in kilograms per cubic meter; and n is the reaction order, usually 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 phosphoric acid solution with a mass fraction of 3 to 5%, and the liquid-to-solid ratio is controlled at 5:1. The heavy metal stabilization efficiency during the phosphoric acid treatment is calculated as follows:

[0057] Where η s is the heavy metal stabilization efficiency, expressed in percentage; C in is the leachable concentration of heavy metals before treatment, in milligrams per liter; C out It is the leachable concentration of heavy metals after treatment, in milligrams per liter.

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

[0059] Where M n+ Represents the heavy metal ions in the waste residue, and n is the valence state of the ion.

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

[0061] Where, E w is the total cleaning efficiency, expressed in percentage; r is the single cleaning efficiency, ranging from 0.5 to 0.7; and n is the number of cleaning times, 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, determined by a weight change of less than 0.1% measured two times two hours apart. This step aims to increase the specific surface area of ​​the waste residue through physical crushing, reduce the risk of heavy metal leaching through thermal decomposition and phosphoric acid stabilization, and lay a safe foundation for the subsequent production of permeable bricks.

[0063] The specific implementation method of step S02 is to perform surface modification treatment on the waste residue, improve the interfacial compatibility between the waste residue and the cement matrix and further stabilize the heavy metals. First, prepare a modifier solution, dissolve a silane coupling agent with a mass fraction of 2 to 4% and a titanate coupling agent with a mass fraction of 0.5 to 1.5% in anhydrous ethanol, and the total volume of the solution to the mass ratio of the waste residue is 2:1. Use a constant temperature magnetic stirrer to stir at room temperature for 30 to 60 minutes to ensure that the coupling agent is completely dissolved and a uniform solution is formed. The stabilized waste residue is then immersed in the prepared solution for 4 to 6 hours, and stirred every 30 minutes during the period to ensure the uniformity of the reaction. The coupling agent surface modification reaction involves the bonding of hydroxyl groups on the waste residue surface with silane groups, and the surface reaction kinetic model can be expressed as:

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

[0065] The calculation formula for surface modification degree is:

[0066] Where D m is the surface modification degree, in percentage; C s is the actual bonding coupling agent concentration, in milligrams per square meter; C max is the theoretical maximum bonding capacity, expressed in milligrams per square meter.

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

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

[0069] The key parameters for the surface modification reaction 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 waste residue surface. The hydroxyl density on the waste residue surface is obtained by infrared spectroscopy and is calculated using the following formula:

[0070] Where, ρ OH is the surface hydroxyl density, in units of per square nanometer; A OH k is the hydroxyl absorption peak area in the infrared spectrum, and its unit is absorbance multiplied by wave number; cal is the correction factor, the unit is absorbance multiplied by wave number multiplied by square meter, and the value is 3.5×10 18 ;S BET is the specific surface area in square meters per gram, determined by nitrogen adsorption.

[0071] After soaking, the waste residue is removed and the filtration rate is controlled to minimize modifier loss. The residue is then transferred to a constant temperature drying oven and dried at 80 to 90°C for 120 to 180 minutes. The drying process utilizes segmented temperature control, with the temperature initially maintained at 70°C for 30 minutes before being raised to the set temperature to prevent rapid solvent evaporation and uneven surface modification. The degree of surface modification is measured using Fourier transform infrared spectroscopy. The optimized process achieves surface coverage exceeding 90%, and heavy metal stability is increased by 3 to 5 times.

[0072] The specific implementation method of step S03 is to prepare a multi-layer structure formula of permeable bricks based on the theory of functional gradient materials. First, accurately weigh each component material. The upper permeable layer formula components include modified waste slag accounting for 40 to 50%, coarse sand accounting for 20 to 30%, fly ash accounting for 10 to 15%, cement accounting for 10 to 15%, nano-silicon dioxide accounting for 1 to 3%, and water retaining agent accounting for 0.5 to 1%. The lower support layer formula components include modified waste slag accounting for 30 to 35%, coarse sand accounting for 30 to 35%, fly ash accounting for 15 to 20%, cement accounting for 15 to 20%, and nano-silicon dioxide accounting for 1 to 2%. The multi-layer structure formula design adopts the material performance balance algorithm, which is expressed by the performance weight matrix:

[0073] Where W is the performance weight matrix; w p1 、w p2 、w p3 、w p4 are the permeability, strength, durability and environmental safety weights of the upper permeable layer; w s1 、w s2 、w s3 、w s4 are the permeability, strength, durability and environmental safety weights of the lower support layer respectively. The recommended weight value of the upper permeable layer is w p1 =0.4, w p2 =0.2, w p3 =0.2, w p4 =0.2; the recommended weight value of the lower support layer is w s1 =0.2, w s2=0.4, w s3 =0.2, w s4 =0.2.

[0074] The recipe performance scoring function is:

[0075] Where S i is the comprehensive performance score of the i-th layer (i=p represents the upper layer, i=s represents the lower layer), with a value range of 0 to 100; w ij is the weight of the i-th layer on the j-th performance; P ij is the normalized score of the jth performance item in the i-th layer, ranging from 0 to 100.

[0076] The performance standardization calculation formula is:

[0077] Where, is the original performance test data; is the minimum acceptable value of the performance indicator; is the ideal target value of this performance indicator.

[0078] The design concept for the upper permeable layer prioritizes high porosity, with a target porosity of 25 to 30% and a target permeability greater than 0.1 cm / s. Water-retaining agents are added to enhance ecological function, with a target water retention rate of 15 to 20%. The design concept for 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 of 0.01 to 0.05 cm / s.

[0079] The specific implementation method of step S04 is to prepare a multi-level porous structure material by optimizing the particle grading technology. First, prepare the upper permeable layer material and the lower support layer material according to the formula components, and use the standard screening method to screen the materials into five particle size grades: 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm and 0.15 mm. The modified Apollonia sphere packing algorithm is used to optimize the particle grading. The algorithm is based on the three-dimensional space filling theory and regards particles of each particle size as rigid spheres. The optimal particle size distribution function is solved by iteratively calculating the void ratio and packing density of different particle size combinations. The optimization objective function is: F(x) = w1·P(x) + w2·S(x) + w3·C(x);

[0080] Where F(x) is the objective function of particle grading optimization, with a value range of 0 to 1; x is the particle size distribution vector, x = (x1, x2, x3, x4, x5), where x irepresents the mass fraction of particles of the i-th size; P(x) is the porosity function, with a numerical range of 0 to 1; S(x) is the strength function, with a numerical range of 0 to 1; C(x) is the connectivity function, with a numerical range of 0 to 1; w1, w2, and w3 are weight 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.

[0081] Porosity function calculation formula:

[0082] Where, ρ i is the bulk density of particles of size i, in grams per cubic centimeter.

[0083] Intensity function calculation formula:

[0084] Where C d is the bulk density of the particles, in grams per cubic centimeter, calculated as C d0 is the critical bulk density, in grams per cubic centimeter, and its value is 1.4; k is the sensitivity coefficient, and its value is 5.

[0085] Connectivity function calculation formula:

[0086] Where c ij is the connectivity coefficient matrix between particles of size class i and j, determined experimentally.

[0087] The optimization solution is realized by genetic algorithm, and the constraints are:

[0088]

[0089] x i ≥x i，min ;

[0090] x i ≤x i，max ;

[0091] Where x i，min and x i，max They are the minimum and maximum allowable mass fractions of particles of grade i, and the specific value ranges are: 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%.

[0092] Through the above optimization algorithm, the particle grading of the upper permeable layer material and the lower support layer material are optimized, and finally a multi-level pore structure is formed, including macropores of 100 to 500 microns for the main permeable channels, mesopores of 10 to 100 microns for capillary adsorption, and micropores of 1 to 10 microns for water retention, forming an efficient permeable and filtration network system.

[0093] The specific implementation method of step S05 is to achieve the double-layer structure forming and interlayer balance optimization of permeable bricks. First, prepare the forming mold and apply a release agent on the inner surface to ensure that the brick body can be smoothly demolded after forming. Mix the lower support layer mixture prepared in step S04 with water in a mass ratio of 0.35 to 0.4, and use a forced mixer to stir for 3 to 5 minutes at a stirring rate of 60 revolutions per minute to ensure that the materials are fully moistened and mixed evenly. Pour the mixed lower layer material into the mold and vibrate it on a vibration table with a vibration frequency of 40 Hz and a vibration time of 30 seconds to ensure that the material is densely filled and reaches 60 to 70% of the designed thickness of the mold. Then prepare the upper permeable layer material, mix the upper layer mixture prepared in step S04 with water in a mass ratio of 0.38 to 0.42, and use the same mixing process to ensure uniform mixing. Pour the upper layer material into the mold with the existing lower layer material and vibrate it again to 100% of the total designed thickness to form a double-layer structure.

[0094] Immediately after forming, the interlayer balance index function is applied to calculate the rationality of the thickness ratio of the upper and lower layers. The interlayer balance index function is defined as:

[0095]

[0096] Where, I b k is the interlayer balance index, dimensionless, with an optimal range of 0.9 to 1.1; p k is the permeability coefficient of the upper layer, in centimeters per second, determined by the infiltration experiment; s is the water permeability coefficient of the lower layer, in centimeters per second, determined by the infiltration experiment; h p is the thickness of the upper layer in millimeters, determined by physical measurement; h s is the thickness of the lower layer in millimeters, determined by physical measurement; f p is the compressive strength of the upper layer, in MPa, obtained through pressure testing; f s is the compressive strength of the lower layer, in MPa, obtained through pressure testing; D cr is the critical protective layer thickness, in millimeters, ranging from 10 to 15; L hm is the potential migration distance of heavy metals, in millimeters, evaluated by leaching experiments; L cris the heavy metal migration limit threshold, in millimeters, with a value range of 30 to 40; α1, α2, α3, and α4 are weight coefficients, and satisfy α1+α2+α3+α4=1. The recommended values ​​are α1=0.3, α2=0.3, α3=0.2, and α4=0.2.

[0097] The first term of the interlayer balance index function represents the balance of water permeability, the second term represents the balance of strength, the third term represents the adequacy of the protective layer thickness, and the fourth term represents the safety of heavy metal migration. An interlayer balance index between 0.9 and 1.1 indicates optimal balance. When it exceeds 1.1, the upper layer thickness should be reduced, while when it is less than 0.9, the upper layer thickness should be increased.

[0098] Using a layered iterative optimization scheme, the thickness ratio update formula is: n+1 =r n ·(2-I b，n );

[0099] Where r n is the thickness ratio of the upper and lower layers at the nth iteration, defined as I b，n is the inter-layer balance index calculated for the nth iteration; r n+1 is the updated thickness ratio of the upper and lower layers.

[0100] The iteration termination condition is: |I b，n -1|<0.1 or n>n max ;

[0101] Where n max The maximum number of allowed iterations is 5.

[0102] Through 3 to 5 iterations of optimization, the interlayer balance index converged within the range of 1.0 ± 0.1, achieving a comprehensive balance between water permeability, strength, and environmental safety. After forming, the bricks require initial curing, allowing them to rest for 4 hours at a temperature of 20°C and relative humidity above 95% to achieve a certain initial strength.

[0103] The specific implementation method of step S06 is to use a low-pressure steam curing process to promote the cement hydration reaction and improve the strength and durability of the permeable bricks. First, the formed brick body is transferred to the pre-curing room and pre-cured at 20 to 25°C for 24 to 36 hours. After the pre-curing is completed, the brick body is transferred to the steam curing room and steam-cured using a program-controlled heating and cooling process. The temperature rise rate during the heating stage is controlled at 5°C per hour to prevent the brick body from cracking due to rapid heating; after reaching the target temperature of 65 to 75°C, a constant temperature is maintained; the relative humidity is controlled at 90 to 95%; the curing time is 72 to 96 hours; the temperature drop rate during the cooling stage is controlled at 3°C ​​per hour to prevent thermal stress from causing microcracks.

[0104] The cement hydration reaction kinetic model can be expressed as:

[0105] Where α is the degree of hydration, dimensionless, ranging from 0 to 1; t is the time, in hours; k h is the reaction rate constant, in units of hours, ranging from 0.01 to 0.1; n is the reaction order, with a value of 2; E h is the apparent activation energy of the hydration reaction, in kilojoules per mole, ranging from 30 to 50; R is the gas constant, 8.314 joules per mole Kelvin; T is the curing temperature, in Kelvin.

[0106] The strength development model can be expressed as:

[0107] Where, f c (t) is the compressive strength at time t, in MPa; f c，∞ is the theoretical maximum compressive strength, in MPa, with a value range of 30 to 40; α(t) is the degree of hydration at time t; α ∞ is the theoretical maximum degree of hydration, ranging from 0.8 to 0.9.

[0108] Calculation formula for steam curing temperature efficiency coefficient:

[0109] Where η T is the temperature efficiency coefficient, with a value range of 0 to 1; T is the actual curing temperature, in degrees Celsius; T0 is the minimum effective curing temperature, with a value of 15°C; T opt The best curing temperature is 70℃.

[0110] The uniformity of temperature and humidity distribution within the curing chamber is controlled in real time by a multi-point monitoring system, ensuring that all bricks receive consistent curing conditions. After curing, bricks undergo strength testing. Compressive strength must exceed 85% of the design value, and permeability must exceed 90% of the design value before proceeding to the next step.

[0111] The specific implementation of step S07 is to treat and seal the surface micropores to improve water permeability and ensure environmental safety. First, prepare a citric acid solution with a mass fraction of 10 to 15%, and control the pH value of the solution to 2.5 to 3.0. Use a spray device to evenly spray the surface of the solidified brick body, with a spray volume of 200 to 250 ml per square meter and a spray pressure controlled at 0.2 MPa to ensure that the solution is evenly distributed on the brick surface. The reaction between citric acid and cement hydration products can be expressed as:

[0112] Ca(OH)2+H3C6H5O7→Ca(C6H5O7)+2H2O;

[0113] 3CaO·2SiO2·3H2O+2H3C6H5O7→3Ca(C6H5O7)+2SiO2+6H2O.

[0114] The surface micropore formation rate model can be expressed as:

[0115] Where P is the surface porosity, dimensionless, ranging from 0.2 to 0.4; t is the reaction time, in minutes; k p is the pore formation rate constant, expressed in milliliters per milligram per minute, with a value ranging from 0.005 to 0.01; C acid is the concentration of the acid solution in milligrams per milliliter; S max is the maximum soluble surface area, in square millimeters per square millimeter; S is the dissolved surface area, in square millimeters per square millimeter.

[0116] After spraying, allow the acid to fully react for 30 to 60 minutes. Maintain an ambient temperature of 20 to 25°C during this period, avoiding direct sunlight and drafts 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 for 2 hours before applying a nano-silica sol surface sealant.

[0117] The calculation formula of penetration depth during nano-silica sol sealing process is:

[0118] Where D p is the penetration depth in millimeters; k i is the correction coefficient, with a value of 0.6; γ is the surface tension of the liquid, in Newtons per meter, with a value range of 0.02 to 0.03; θ is the contact angle, in degrees, with a value range of 20 to 40; r is the average pore size, in microns, with a value range of 0.1 to 1; t is the penetration time, in seconds; η is the sol viscosity, in Pascal seconds, with a value range of 0.001 to 0.003.

[0119] Calculation formula for heavy metal migration blocking efficiency:

[0120] Where η b is the blocking efficiency, expressed in percentage; C out，b is the concentration of heavy metal leaching after sealing treatment, in milligrams per liter; C out，0 It is the heavy metal leaching concentration when not sealed, in milligrams per liter.

[0121] The treated bricks were dried at room temperature for 24 hours. After completion, water permeability and heavy metal leaching tests were conducted to verify the treatment results. The optimized surface treatment process can increase the brick surface water permeability by 30 to 50% while reducing the risk of heavy metal leaching by over 90%, meeting the dual requirements of ecological permeability and environmental safety.

[0122] In order to better understand and implement the present invention, Example 2 of a specific application scenario of the present invention is provided below: This example uses converter slag produced by a steel plant 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 metal elements such as chromium and lead. The particle size distribution of the steel slag is uneven, with the maximum particle size reaching 15 mm. The main components and heavy metal content are shown in Table 1:

[0123] Table 1 Main components and heavy metal content of raw steel slag

[0124] 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

[0125] First, the steel slag is crushed and initially crushed to less than 10 mm using a PE400×600 jaw crusher, and then further crushed to a particle size of no more than 5 mm using a PC400×300 hammer crusher. The crushed steel slag is placed in a tubular electric furnace and pyrolyzed under nitrogen protection. The pyrolysis temperature is set at 600°C and the treatment time is 210 minutes. The waste slag after pyrolysis is cooled to room temperature and transferred to an enameled reactor. A 4% phosphoric acid solution is added for soaking with a liquid-to-solid ratio of 5:1 and a soaking time of 30 hours. After soaking, it is washed three times with deionized water. The washed waste slag is dried to constant weight at 108°C to obtain stabilized waste slag.

[0126] The stabilized waste residue was subjected to surface modification treatment, and a modifier solution was prepared, including 3% silane coupling agent KH-550 and 1% titanate coupling agent TZ-33, which were dissolved in anhydrous ethanol. The total volume of the solution and the mass ratio of the waste residue were 2:1. After stirring to form a uniform solution, the stabilized waste residue was immersed in the solution for 5 hours, and stirred every 30 minutes. The soaked waste residue was filtered and collected, and dried at 85°C 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 / nm. 2 .

[0127] Then prepare the multi-layer structure formula of permeable bricks. Among them, the double-layer structure of ecological permeable bricks is as follows Figure 2 The specific formulas of the upper permeable layer and the lower support layer are shown in Table 2:

[0128] Table 2 Composition of the upper and lower layers of permeable bricks (mass percentage)

[0129]

[0130]

[0131] According to the optimized particle grading technology, the upper permeable layer material and the lower support layer material are screened into five particle size grades respectively. The screening results are shown in Table 3:

[0132] Table 3 Particle size distribution of upper and lower layer materials (mass percentage)

[0133] Particle size grade Upper aquifer (%) 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

[0134] To prepare the bricks, the lower support layer mixture was first mixed with water at a mass ratio of 0.38 for four minutes, poured into a 240×120×60 mm mold, and compacted to a thickness of 39 mm (65% of the total thickness). The upper permeable layer mixture was then mixed with water at a mass ratio of 0.4 for four minutes, poured into the mold, and compacted to a total thickness of 60 mm. The initial upper-lower layer thickness ratio was 7:13. After three iterations of optimization, the final upper-lower layer thickness ratio was determined to be 3:7, with an interlayer balance index of 1.02.

[0135] The formed bricks were pre-cured at 23°C for 30 hours, followed by steam curing at 70°C and 93% relative humidity for 84 hours. After curing, the bricks were sprayed with a 12% citric acid solution, left to stand for 45 minutes, rinsed with water, and sealed with a 4% nano-silica sol. The final product was then dried for 24 hours.

[0136] The performance indicators of the finished permeable bricks are shown in Table 4:

[0137] Table 4 Performance test results of finished permeable bricks

[0138] Performance indicators upper layer Lower level overall Standard requirements Water permeability (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 Freeze-thaw cycle (25 times) mass loss rate (%) 2.3 1.2 1.6 ≤3

[0139] Traditional industrial waste treatment technologies primarily rely on cement curing or vitrification, but these methods are associated with high energy consumption, high costs, and a significant risk of secondary pollution. Traditional permeable brick manufacturing techniques typically use a single material, making it difficult to balance permeability and strength. Alternatively, they employ simple porous structures, which can lead to pore clogging, reduced strength, and difficulty effectively immobilizing heavy metals.

[0140] The layered composite structure design adopted in the present invention solves the core problems of traditional technologies: the three-stage treatment process of thermal decomposition-phosphoric acid stabilization-coupling agent modification significantly reduces the risk of heavy metal leaching; the modified Apollonia sphere stacking algorithm is used to optimize the particle grading, realize a multi-level pore structure, and ensure the balance between permeability and strength; the interlayer balance index function is innovatively applied to optimize the ratio of the upper and lower layer structures, so that the permeable bricks have both high permeability (0.09cm / s) and high strength (24.6MPa); the combination of surface micropore treatment and nano-silica sol sealing technology further improves the permeability and ensures environmental safety, and the heavy metal leaching concentration is lower than 0.01mg / L, which is lower than the standard limit.

[0141] It should be noted that the variables involved in the present invention are explained in detail as shown in Tables 5 and 6 below.

[0142] Table 5 Variable Explanation Table (Part 1)

[0143]

[0144]

[0145] Table 6 Variable Explanation Table (Part 2)

[0146]

[0147]

[0148] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing industrial waste residue-based ecological permeable bricks, characterized in that: include: The industrial waste residue is pre-stabilized by pyrolysis and soaked in phosphoric acid solution; A hydrophobic protection network is formed at the molecular level by mixing and modifying silane coupling agents and titanate coupling agents. The upper permeable layer and lower support layer materials are designed according to an optimized formula. The proportion of particles of different sizes is adjusted using optimized particle grading technology. A double-layer structure is adopted, and the thickness ratio of the upper and lower layers is adjusted by the interlayer balance index function. Low-pressure steam curing is used to form a solidified brick body. Finally, surface micropore treatment and nano-silica sol sealing treatment are performed to prevent heavy metal leaching.

2. The method according to claim 1, characterized in that The step of pretreating the industrial waste residue specifically comprises crushing the industrial waste residue 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, washing it three times, and drying it at 105 to 110° C. to constant weight to obtain stabilized waste residue.

3. The method according to claim 2, characterized in that The step of modifying the waste residue by mixing a silane coupling agent with a titanate coupling agent is as follows: mixing a silane coupling agent with a mass fraction of 2 to 4% and a titanate coupling agent with a mass fraction of 0.5 to 1.5% in an ethanol solution, stirring for 30 to 60 minutes to form a uniform solution, immersing the stabilized waste residue in the uniform solution for 4 to 6 hours, taking it out, and drying it at 80 to 90° C. for 120 to 180 minutes to obtain the modified waste residue.

4. The method according to claim 3, characterized in that The formula of the upper permeable layer is 40 to 50% modified waste slag, 20 to 30% coarse sand, 10 to 15% fly ash, 10 to 15% cement, 1 to 3% nano-silicon dioxide, and 0.5 to 1% water-retaining agent; the formula of the lower support layer is 30 to 35% modified waste slag, 30 to 35% coarse sand, 15 to 20% fly ash, 15 to 20% cement, and 1 to 2% nano-silicon dioxide.

5. The method according to claim 4, characterized in that The optimized particle grading technology specifically involves screening and mixing the upper permeable layer material and the lower support layer material according to the ratio of 2.36 mm accounting for 15 to 20%, 1.18 mm accounting for 25 to 30%, 0.6 mm accounting for 30 to 35%, 0.3 mm accounting for 15 to 20%, and 0.15 mm accounting for 5 to 10%, respectively, to prepare upper and lower layer mixtures with multi-level pore structures.

6. The method according to claim 5, characterized in that The steps of forming the double-layer structure are as follows: first, the lower layer mixture is mixed with water in a mass ratio of 0.35 to 0.4 and stirred for 3 to 5 minutes, poured into a mold and compacted to 60 to 70% of the designed thickness, and then the upper layer mixture is mixed with water in a mass ratio of 0.38 to 0.42 and stirred for 3 to 5 minutes, poured into a mold and compacted to a total thickness of 100%.

7. The method according to claim 6, characterized in that The input parameters of the interlayer balance index function include the upper layer permeability coefficient, the lower layer permeability coefficient, the upper layer compressive strength, the lower layer compressive strength, the upper layer thickness, the total thickness, the potential migration distance of heavy metals, and the heavy metal migration limit threshold; the output of the interlayer balance index function is used to guide the optimization of the thickness ratio of the double-layer structure.

8. The method according to claim 7, characterized in that When the interlayer balance index is between 0.9 and 1.1, it indicates that the optimal balance state is 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.

9. The method according to claim 8, characterized in that After the double-layer structure is formed, a layered iterative optimization scheme is adopted. First, the double-layer brick structure is established based on the initial formula. After measuring the physical parameters, the interlayer balance index function is entered to calculate the interlayer balance index value. If the interlayer balance index value is not in the optimal range, the ratio of the upper layer thickness to the lower layer thickness and the formula parameters are adjusted, and the product is re-prepared and tested. After 3 to 5 iterative optimizations, the interlayer balance index value converges to the range of 1.0±0.

1.

10. The method according to claim 9, characterized in that The optimized particle grading technology is optimized using the three-dimensional sphere packing principle, specifically using a modified Apollonia sphere packing algorithm to iteratively fill the gaps between particles of different particle sizes to achieve a balance between porosity and strength and solve the optimal particle size distribution function.

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