Preparation method of carbon sequestration water permeable brick

Abstract

The application discloses a preparation method of carbon sequestration water permeable bricks, comprising the following steps: 1) drying and grinding powdery solid waste to obtain active micro powder; 2) mixing the active micro powder, magnesium slag, part of aggregate and water, and synchronously introducing industrial flue gas containing CO2 in the wet grinding process to carry out pre-mineralization reaction, so that a nano-carbonate "fluff layer" is generated on the surface of the aggregate, and a pre-mineralization slurry rich in nano-carbonate crystal nucleus is formed in the slurry; 3) mixing the obtained pre-mineralization slurry with the remaining aggregate and a modifier; 4) dehydrating and pressure forming into a brick blank; and 5) curing and mineralizing the brick blank in a CO2 atmosphere. Through the wet grinding pre-mineralization of the aggregate, the interface bonding between the aggregate and the cementing phase is significantly enhanced, the mechanical properties, water permeability and carbon sequestration efficiency of the water permeable brick are greatly improved while the solid waste is efficiently disposed, and low-carbon manufacturing is realized.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a method for preparing carbon-fixed permeable bricks. Background Technology

[0002] Permeable bricks are an indispensable environmentally friendly material in modern urban construction. With the acceleration of urbanization, the problem of hardened urban surfaces has become increasingly serious, and the emergence of permeable bricks has effectively alleviated this situation. They possess excellent permeability, allowing rainwater to quickly infiltrate the ground, replenishing groundwater, reducing surface runoff, and thus lowering the risk of urban flooding. Simultaneously, their porous structure can adsorb dust and other impurities, playing a role in purifying the air and reducing noise, significantly improving the quality of the urban environment and providing key support for urban construction concepts such as "sponge cities" and "ecological cities." There is a complex and contradictory relationship between the mechanical properties and permeability coefficient of permeable bricks. From a mechanical performance perspective, in order for permeable bricks to withstand various loads from vehicles, pedestrians, etc., the brick body needs high strength and good flexural strength. This usually means that the brick structure must be relatively dense, and the bonding between materials must be tight. However, for the permeability coefficient, the brick body needs to have enough pores to allow water to pass through smoothly. Pores are the channels for water permeability; the higher the porosity, the greater the permeability coefficient tends to be. This is similar to a sponge; the more and larger the pores, the stronger its water absorption (permeability). Therefore, in practice, when trying to improve the mechanical properties of permeable bricks, it's inevitable to reduce or shrink the pores, leading to a decrease in the permeability coefficient. Conversely, excessively pursuing a high permeability coefficient and increasing porosity will significantly compromise the mechanical properties of the permeable bricks, making them prone to damage during use. On the other hand, traditional permeable brick production often relies on materials like cement. The cement industry, a typical high-CO2-emission sector, emitted over 1.2 billion tons of CO2 in my country in 2020 alone, accounting for 12% of total social CO2 emissions. The permeable brick industry urgently needs to explore innovative production methods that reduce cement usage or adopt low-carbon, environmentally friendly alternatives to reduce CO2 emissions from production, achieve green and sustainable development, better align with the national green development strategy, and achieve a balance and win-win situation between urban construction and environmental protection.

[0003] Solid waste, as a byproduct of industrial production, is not only abundant but also contains a chemical composition similar to silicate cement. Therefore, using solid waste to produce permeable bricks can effectively reduce dependence on high-emission cement and lower carbon emissions. Furthermore, these solid wastes, rich in active components such as silicon and aluminum, can endow permeable bricks with excellent mechanical and permeability properties, opening up a new path for environmentally friendly and high-value production. In addition, CO2 mineralization curing can also improve the mechanical properties of cement-based materials. Closely integrating carbon sequestration with the preparation of high-value building materials to achieve "waste treatment and carbon sequestration from solid waste" is a key direction for overcoming bottlenecks. However, existing solid waste-based CO2 curing technologies typically concentrate CO2 mineralization in the curing stage of the final formed green body. This method has inherent drawbacks: the diffusion resistance of CO2 gas in the already formed dense green body is high, the mineralization reaction only occurs on the surface, and the penetration depth is limited; the mineralization efficiency is severely limited by the pore structure and density of the green body; and achieving a certain amount of carbon sequestration often requires curing time of several days or even weeks, resulting in low efficiency. The fundamental reason is that CO2 failed to participate in the reaction in the early stages when the material system has the largest specific surface area and reactivity, thus missing the best opportunity for mineralization. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing carbon-fixed permeable bricks, which overcomes the defects of weak aggregate-matrix interface bonding and low mineralization efficiency in the prior art. By introducing part of the aggregate into the wet grinding pre-mineralization stage, in-situ activation and mineralization of the aggregate surface are achieved, simultaneously solving the two major problems of interface strengthening and deep carbon fixation.

[0005] The technical solution of the present invention is as follows: A method for preparing a carbon-fixed permeable brick includes the following steps: 1) Dry and grind the powdered solid waste to obtain 100-200 mesh active micro powder; 2) Preparation of premineralized slurry: The active micro powder, magnesium slag, and first part of aggregate obtained in step 1) are mixed with water in a certain proportion. The mixture is ground in a wet grinding equipment while a gas containing CO2 is introduced to carry out wet grinding and premineralization reaction, so as to obtain a premineralized slurry rich in carbonate crystal nuclei and with the surface of aggregate mineralized. 3) Mix the premineralized slurry obtained in step 2), the second part of aggregate, the modifier and water to prepare a mixed slurry; 4) After dehydrating the mixed slurry, it is pressed into brick blanks; 5) Deep mineralization curing: Place the brick blanks obtained in step 4) in a CO2 curing chamber for mineralization curing to obtain carbon-fixed permeable bricks.

[0006] The powdered solid waste is selected from at least one of magnesium slag, steel slag, and construction waste residue. The CO2-containing gas is industrial kiln flue gas with a CO2 volume concentration of not less than 10%. The first and second aggregates together constitute the aggregate system of the permeable brick, and the first and second aggregates are selected from at least two of natural river sand, lightweight aggregates, and construction waste aggregates.

[0007] In this invention, the first portion of aggregate participates in the wet grinding stage, where its surface is mechanically activated, exposing more active sites. Simultaneously, it reacts with CO2 in the liquid phase to generate a nanoscale carbonate "fluffy layer." This "fluffy layer" serves as a seed crystal for subsequent mineralization reactions and, after molding, forms a continuous transition with the carbonate crystals in the cementitious phase, significantly enhancing the interfacial bonding between the aggregate and the matrix. The second portion of aggregate is added in the subsequent mixing stage, acting as a skeletal support to ensure the permeability of the permeable brick.

[0008] Preferably, in step 2), the first part of the aggregate accounts for 25%-70% of the total mass of the aggregate system, and the second part of the aggregate accounts for 30%-75% of the total mass of the aggregate system. By adjusting the proportion of the two-stage aggregates, the balance between the interface reinforcement effect and the permeability can be controlled.

[0009] Preferably, in step 2), the mass ratio of the active micro powder, magnesium slag, first aggregate, and water is (30-45):(30-45):(10-30):(15-30). The addition of magnesium slag provides magnesium ions, which induce the formation of aragonite-type calcium carbonate during the pre-mineralization process, which is beneficial to the formation of a dense and stable interface layer.

[0010] Preferably, in step 2), the wet grinding ball-to-particle ratio is 1:2, the grinding ball size is 0.6-0.8 mm, the wet grinding speed is 300-400 r / min, and the wet grinding time is 1-2 h. Under these conditions, the first part of the aggregate can be effectively ground and activated without being over-crushed and affecting the gradation.

[0011] In step 3), the proportions of the pre-mineralized slurry, the second aggregate, and the modifier, by weight, are (50-70):(15-30):(5-10). The modifier includes at least one of magnesium ion-doped modifier, quaternary ammonium salt surfactant, and polyethylene glycol, used to further regulate the mineralization reaction and pore structure.

[0012] In step 4), the pressure for pressing is 5-40 MPa, and the holding time is 300-400 s.

[0013] In step 5), the mineralization curing temperature is 20-30℃, the humidity is 20-40%, and the time is 4-24h. The carbonate crystal nuclei and carbonate "velvet layer" generated in step 2) serve as growth templates during the curing stage, accelerating and guiding the deep mineralization reaction inside the brick blank, while strengthening the interfacial bonding between the aggregate and the cementitious phase.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The technical concept of participating in wet grinding and pre-mineralization of aggregates was proposed for the first time, which enables the in-situ generation of nano-carbonate "fluff layer" on the surface of aggregates, realizes chemical bonding at the aggregate-matrix interface, and fundamentally solves the problem of weak interface between aggregates and cementitious phase in permeable bricks.

[0015] 2. The carbonate layer formed on the surface of premineralized aggregates serves as a template for crystal growth during subsequent curing, guiding calcium carbonate to preferentially grow at the interface and forming a continuous microstructure from aggregate to matrix, which greatly improves flexural strength and freeze-thaw resistance.

[0016] 3. The two-stage aggregate addition strategy balances interface enhancement and permeability: the first part of the aggregate is deeply pre-mineralized to strengthen the interface, and the second part of the aggregate maintains its original morphology to build interconnected pores, so that the permeable brick can achieve high strength while maintaining an excellent permeability coefficient.

[0017] 4. This invention uses all solid waste raw materials, requires no cement, and combines a two-stage carbon sequestration process to achieve high-value utilization of solid waste and permanent CO2 sequestration. The product performance is superior to the national standard (GB / T25993-2010), and has significant economic and environmental benefits. Attached Figure Description

[0018] Figure 1 Scanning electron microscope image of nanoscale calcium carbonate; Figure 2 This is a scanning electron microscope image of aragonite whiskers formed after the mineralization reaction. Figure 3 Scanning electron microscope image of aragonite whiskers formed on the surface of aggregate. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with preferred embodiments, details the specific implementation, structure, features, and effects of a method for preparing a carbon-fixing permeable brick according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0020] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0021] In the following embodiments of the present invention, unless otherwise specified, all reagents used are commercially available, and all methods involved are conventional methods.

[0022] Example 1 This invention provides a method for preparing carbon-fixed permeable bricks, the specific steps of which are as follows: (1) Dry magnesium slag, steel slag and construction waste residue at 600℃ for 60 min, reduce the moisture content to 8-12%, grind for 20 min to obtain 100-200 mesh active micro powder.

[0023] (2) Preparation of premineralized slurry: Take 35 parts of active micro powder, 40 parts of magnesium slag, 15 parts of the first part of aggregate (natural river sand), and 25 parts of water, mix them, and place them in a wet mill. At the same time, continuously introduce cement kiln tail gas (taken from the outlet of the waste heat boiler, CO2 concentration 20%, temperature 180-220℃) for wet grinding. Wet grinding conditions: ball-to-material ratio 1:2, grinding ball particle size 0.6mm, rotation speed 350r / min, time 1h. A premineralized slurry is obtained, in which a nano-calcium carbonate "fluffy layer" is formed on the surface of the river sand.

[0024] (3) Preparation of mixed slurry: Take 60 parts of premineralized slurry from step 2), 20 parts of aggregate from the second part (construction waste aggregate), 3 parts of quaternary ammonium salt surfactant, and 2 parts of polyethylene glycol, add water to adjust the consistency, and stir at 300 r / min for 20 min.

[0025] (4) Dehydration molding: Dehydrate the mixed slurry at 0.8MPa for 15min, transfer it into a mold and pressurize it at 20MPa for 350s to obtain brick blanks.

[0026] (5) Mineralization curing: The brick blanks are sent into the CO2 curing chamber and the same cement kiln tail gas as in step 2) is introduced. The temperature is controlled at 30℃, the humidity at 40%, and the time is 12h to obtain carbon-fixed permeable bricks.

[0027] Example 2 This invention provides a method for preparing carbon-fixed permeable bricks, the specific steps of which are as follows: (1) Dry magnesium slag and construction waste residue at 600℃ for 120 min, reduce the moisture content to 5-10%, grind for 10 min to obtain 100-200 mesh active micro powder.

[0028] (2) Pre-mineralized slurry: Take 40 parts of active micro powder, 43 parts of magnesium slag, 10 parts of the first part of aggregate (lightweight aggregate), and 17 parts of water. Wet grind the slurry and introduce it into the cement kiln tail gas (outlet of the first preheater, CO2 concentration 25%, temperature 280-350℃). Wet grinding conditions: ball-to-material ratio 1:2, grinding balls 0.6mm, rotation speed 300r / min, time 1h.

[0029] (3) Mixed slurry: Take 55 parts of premineralized slurry, 25 parts of the second part of aggregate (natural river sand), and 5 parts of polyethylene glycol, and add water and stir.

[0030] (4) Dehydration molding: pressure 25MPa, holding pressure for 300s.

[0031] (5) Curing: Same as in Example 1, temperature 25℃, humidity 35%, time 10h.

[0032] Example 3 This invention provides a method for preparing carbon-fixed permeable bricks, the specific steps of which are as follows: (1) Dry steel slag and construction waste residue at 700℃ for 40 min, reduce the moisture content to 7-11%, grind for 60 min to obtain 100-200 mesh active micro powder.

[0033] (2) Pre-mineralized slurry: Take 40 parts of active micro powder, 35 parts of magnesium slag, 20 parts of the first part of aggregate (construction waste aggregate), and 21 parts of water. Wet grinding is carried out with lime kiln tail flue gas (CO2 concentration 28%, temperature 480-510℃). Wet grinding conditions: ball-to-material ratio 1:2, grinding balls 0.8mm, rotation speed 400r / min, time 2h.

[0034] (3) Mixed slurry: Take 65 parts of premineralized slurry, 15 parts of the second part of aggregate (natural river sand + lightweight aggregate), 4 parts of magnesium ion doping modifier, and 1 part of polyethylene glycol, and add water and stir.

[0035] (4) Dehydration molding: pressure 15MPa, holding pressure for 350s.

[0036] (5) Curing: Temperature 28℃, humidity 30%, time 8h.

[0037] Comparative Examples 1-3 Comparative Examples 1-3 were prepared using the same methods as Examples 1-3, except that the first part of the aggregate was not added in step 2), i.e., all the aggregate was added in step 3), and no aggregate was involved in the wet grinding stage.

[0038] Comparative Example 4-5 Comparative Example 4 is the same as Example 1, but CO2 is not introduced in step 2), i.e., only wet milling without pre-mineralization. Comparative Example 5 is the same as Example 1, but step 5) uses traditional autoclaving (180°C, saturated steam) instead of CO2 curing.

[0039] The permeable bricks prepared in Examples 1-3 all meet the requirements of the national standard "Permeable Pavement Bricks and Permeable Pavement Panels" (GB / T25993-2010), with a permeability coefficient ≥1.9mm / s, flexural strength ≥11.87MPa, and carbon fixation rate ≥16.78%, demonstrating excellent comprehensive performance.

[0040] Examples 1-3, through precise limitation of raw material types and amounts, and scientific adjustment of preparation process parameters, all produced permeable bricks exhibiting excellent characteristics such as high flexural strength, low density, and high carbon fixation rate. In particular, Example 2, by optimizing aggregate gradation and the two-stage aggregate addition ratio (the first part of the aggregate accounts for approximately 28.6% of the total aggregate, and the second part accounts for approximately 71.4%), achieved the highest carbon fixation rate (19.33%) while maintaining a high permeability coefficient (2.4 mm / s), fully demonstrating the synergistic solution of the present invention to the ternary contradictions of permeability, strength, and carbon fixation.

[0041] Figure 1 The microstructure of the nanoscale carbonate fluff layer formed on the aggregate surface after wet milling and mineralization is shown. The area marked by the red box reveals fine nano-carbonate grains adhering to the aggregate surface in a network / fluffy manner. This layer is a product formed by the mechanical activation and CO2 reaction of the aggregate during the wet milling stage. It can serve as a crystal growth template and heterogeneous nucleation site, enhancing the interfacial bonding strength between the aggregate and the cementitious matrix, and inducing a more complete and uniform subsequent mineralization reaction.

[0042] Figure 2 Needle-shaped aragonite is formed on the surface of the mineral after the reaction of magnesium ions and carbonization.

[0043] Figure 3 The microstructure of aragonite whiskers formed on the aggregate surface is shown, with typical needle-like aragonite-type calcium carbonate crystals visible in the area marked by the red box. These needle-like whiskers form on the aggregate surface under the induction of magnesium ions.

[0044] The preparation methods of Comparative Examples 1-3 are basically the same as those of Examples 1-3. The core difference is that the first part of the aggregate was not added in step 2) of Comparative Examples 1-3, that is, all the aggregate was added in step 3), and no aggregate participated in the pre-mineralization during the wet grinding stage. The flexural strength of Comparative Examples 1-3 (8.95-10.15 MPa) was significantly lower than that of Examples 1-3 (11.87-13.02 MPa), with a decrease of about 15-25%; the carbon fixation rate of Comparative Examples 1-3 (11.42-14.05%) was significantly lower than that of Examples 1-3 (16.78-19.33%), with a decrease of about 20-30%; the water permeability coefficient of Comparative Examples 1-3 (1.5-1.8 mm / s) was also lower than that of Examples 1-3 (1.9-2.4 mm / s). In Examples 1-3, the first batch of aggregate participates in the wet grinding stage. Its surface is activated by mechanical force, exposing a large number of fresh fracture surfaces and lattice defects. At the same time, it reacts with CO2 in the liquid phase to generate a nanoscale carbonate "fluff layer". This fluff layer has an interface strengthening effect. The nanoscale carbonate layer on the surface of the premineralized aggregate serves as a crystal growth template in the subsequent curing process, guiding calcium carbonate to grow outward along the aggregate surface. It interweaves with the carbonate generated in the matrix, forming a continuous transition zone from aggregate to cementitious phase, significantly enhancing the interfacial bonding strength. In addition, it also has a nucleation induction effect. The nanoscale carbonate grains generated on the aggregate surface serve as heterogeneous nucleation sites, lowering the energy barrier of the subsequent mineralization reaction, making the mineralization reaction in the CO2 curing stage more complete and uniform. Finally, the presence of aragonite has a microfiber strengthening effect. The aragonite-type calcium carbonate induced by magnesium ions has a needle-like structure, forming a "fluff layer" on the aggregate surface, which plays a microfiber strengthening role and further improves the toughness of the brick. In contrast, Comparative Examples 1-3 lacked aggregate participation in the wet grinding pre-mineralization process, resulting in smooth aggregate surfaces, low activity, and only mechanical interlocking with the cementitious phase, leading to weak interfacial bonding. Furthermore, the lack of nucleation-induced effects on the aggregate surface resulted in slow initiation and shallow reaction of subsequent mineralization reactions, ultimately leading to a comprehensive decline in strength, carbon fixation rate, and water permeability.

[0045] This invention significantly enhances the interfacial bonding between aggregates and the cementitious phase by involving aggregates in wet grinding and pre-mineralization. While efficiently disposing of solid waste, it greatly improves the mechanical properties, permeability, and carbon sequestration efficiency of permeable bricks, thus achieving low-carbon manufacturing.

[0046] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a carbon-fixed permeable brick, characterized in that, Includes the following steps: 1) Dry and grind the powdered solid waste to obtain 100-200 mesh active micro powder; 2) Preparation of premineralized slurry: The active micro powder, magnesium slag, and first part of aggregate obtained in step 1) are mixed with water in a certain proportion. The mixture is ground in a wet grinding equipment while a gas containing CO2 is introduced to carry out wet grinding and premineralization reaction to obtain premineralized slurry. 3) Mix the premineralized slurry obtained in step 2), the second part of aggregate, the modifier and water to prepare a mixed slurry; 4) After dehydrating the mixed slurry, it is pressed into brick blanks; 5) Deep mineralization curing: Place the brick blanks obtained in step 4) in a CO2 curing chamber for mineralization curing to obtain carbon-fixed permeable bricks.

2. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, The first and second portions of aggregate together constitute the aggregate system of the permeable brick. The first part of the aggregate accounts for 25%-70% of the total mass of the aggregate system, and the second part of the aggregate accounts for 30%-75% of the total mass of the aggregate system.

3. The method for preparing carbon-fixed permeable bricks according to claim 1 or 2, characterized in that, In step 2), the CO2 volume concentration in the CO2-containing gas is not less than 10%, and the CO2-containing gas is industrial kiln flue gas, which is selected from at least one of cement kiln tail flue gas, glass kiln tail flue gas, lime kiln tail flue gas or chemical reactor tail flue gas.

4. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, In step 2), the conditions for wet milling and pre-mineralization reaction are: ball-to-material ratio 1:2, grinding ball particle size 0.6-0.8mm, wet milling speed 300-400r / min, and wet milling time 1-2h.

5. The method for preparing carbon-fixed permeable bricks according to claim 4, characterized in that, In step 2), the mass ratio of the active micro powder, magnesium slag, first part of aggregate and water is (30-45):(30-45):(10-30):(15-30).

6. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, In step 1), the drying temperature is 300-700℃, the drying time is 30-480min, and the moisture content of the material after drying is less than 15%.

7. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, In step 3), the proportion of the premineralized slurry, the second aggregate and the modifier by weight is (50-70):(15-30):(5-10).

8. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, In step 4), the pressure for pressurization is 5-40 MPa, and the holding time is 300-400 s.

9. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, In step 5), the conditions for mineralization curing are: temperature 20-30℃, humidity 20-40%, and time 4-24h.

10. The method for preparing carbon-fixed permeable bricks according to claim 1, characterized in that, The powdered solid waste is selected from at least one of magnesium slag, steel slag, and construction waste residue; The first part of the aggregate and the second part of the aggregate are selected from at least two of the following: natural river sand, lightweight aggregate and construction waste aggregate; The modifier includes at least one of magnesium ion doping modifier, quaternary ammonium salt surfactant and polyethylene glycol.

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