A full-solid-waste low-carbon non-burning brick and a preparation method thereof

Abstract

This invention provides a low-carbon, non-fired brick made entirely from solid waste and its preparation method, belonging to the technical field of solid waste resource utilization and low-carbon building materials. The non-fired brick is made from specific weight parts of industrial solid waste raw materials, including 30-45 parts steel slag, 30-45 parts blast furnace slag, 10-40 parts calcium carbide slag, and 20 parts water. The preparation method includes: mixing and stirring the above raw materials into a slurry, pressing it into brick blanks, then placing the brick blanks in a carbonization curing chamber, introducing CO2 industrial waste gas at a pressure of 0.1 MPa for 4-24 hours of carbonization curing, and finally transferring them to a constant temperature and humidity environment for 26-28 days of conventional curing. This method utilizes the calcium carbonate and silica gel generated during the carbonization process to construct an early strength framework, and further optimizes the microstructure through the synergistic hydration reaction of the solid waste components during subsequent curing. The resulting non-fired brick has excellent mechanical properties, good durability, and significant carbon fixation effect, while achieving low-cost production.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and low-carbon building materials technology, specifically relating to a low-carbon, non-fired brick made entirely from solid waste and its preparation method. Background Technology

[0002] With the deepening of the "zero-waste city" construction strategy, the resource utilization of bulk industrial solid waste has become a major requirement for my country's green and low-carbon development. Among them, the preparation of all-solid-waste non-fired bricks using typical industrial solid wastes such as steel slag, ore slag, and carbide slag is regarded as an important way to achieve solid waste disposal and building material utilization due to its significant advantages of not requiring sintering, low energy consumption, and simple process.

[0003] However, existing technologies for producing all-solid-waste non-fired bricks still face key technical bottlenecks. First, due to the lack of stable chemical bonds formed by high-temperature sintering, solid-waste non-fired bricks mainly rely on physical pressing and weak cementing, resulting in mechanical properties and durability that fail to meet the performance requirements of building materials. Second, existing technologies still primarily use single solid wastes as raw materials, adding cement or chemical activators to improve performance, without considering the synergistic effects between multiple solid waste components. This not only increases production costs but also reduces the actual utilization rate of solid waste, deviating from the original intention of the "all-solid-waste" concept.

[0004] On the other hand, the industrial flue gas emitted by coal-fired power plants is rich in CO2, and its capture, storage, and utilization are also major challenges facing my country in achieving its "dual carbon" goals. Traditional carbon capture technologies are costly and difficult to promote. Therefore, if they can be organically combined with the solid waste building materials process to construct a technical path of "treating waste with waste and fixing carbon in materials," it will have significant environmental and economic value. Summary of the Invention

[0005] This invention aims to solve two key challenges in the current fields of industrial solid waste resource utilization and carbon emission reduction. On the one hand, addressing the shortcomings of existing all-solid-waste non-fired bricks—namely, insufficient mechanical strength and durability due to a lack of stable chemical bonding, and reliance on external cementing materials (such as cement) that deviates from the original intention of "all-solid-waste, low-cost"—this invention designs a ternary solid waste synergistic system of steel slag, blast furnace slag, and carbide slag to prepare high-performance non-fired bricks without adding external cementing materials. On the other hand, this invention combines industrial solid waste utilization with CO2 fixation. Its core technology aims to utilize CO2 from industrial flue gas to carbonize and cure the brick blanks, thereby improving brick performance while achieving "waste treatment and turning waste into treasure." This simultaneously achieves the dual goals of disposing of large quantities of solid waste and sealing carbon dioxide, ultimately providing a simple, low-cost, and environmentally friendly method for preparing green building materials.

[0006] To achieve the above-mentioned technical objectives of this invention, the following technical solution is adopted: In one aspect, a low-carbon, non-fired brick made entirely from solid waste is provided, comprising the following raw materials in parts by weight: 30-45 parts steel slag, 30-45 parts blast furnace slag, 10-40 parts calcium carbide slag, and 20 parts water.

[0007] Preferably, the main components of the steel slag are CaO and Fe2O3; the main components of the ore slag are CaO, SiO2 and Al2O3; and the main component of the carbide slag is CaO.

[0008] Secondly, a method for preparing low-carbon, non-fired bricks made entirely from solid waste is provided, comprising the following steps: (1) Mix steel slag, mineral slag, calcium carbide slag and water for 3-5 minutes to obtain a slurry; (2) The slurry is statically pressed under a pressure of 10-20 MPa for 2-3 minutes to obtain a brick blank; (3) Place the brick blank in a carbonization curing environment with a temperature of 20±2℃ and a humidity of 60~80%, introduce CO2 industrial waste gas until the gas pressure reaches 0.1MPa, and perform carbonization curing for 4~24 hours; (4) After carbonization, the brick blank is transferred to an environment with a temperature of 20±2℃ and a humidity of ≥95% for conventional curing for 26 to 28 days to obtain the all-solid waste low-carbon non-fired brick.

[0009] Preferably, in step (3), the CO2 industrial waste gas originates from the flue gas of a coal-fired power plant, and its CO2 volume concentration is 10%.

[0010] Preferably, in step (3), the carbonization curing time is 8 to 24 hours.

[0011] Preferably, in step (3), the carbonization curing time is 24 hours.

[0012] Preferably, in step (1), the weight parts of the steel slag, ore slag, carbide slag and water are 35 parts steel slag, 35 parts ore slag, 30 parts carbide slag and 20 parts water, respectively.

[0013] The dry density of the all-solid-waste low-carbon non-fired bricks prepared by this invention is 1.58–1.68 g / cm³. 3 The 28-day compressive strength is 18.2–39.1 MPa, the carbon fixation rate is 5.2–10.0%, the 28-day water absorption rate is less than 15%, and the softening coefficient is greater than 0.85.

[0014] Compared with the prior art, the present invention achieves the following technical effects: First, a multi-component solid waste synergistic cementing system was constructed by using steel slag, blast furnace slag, and carbide slag in specific proportions. This method fully utilizes the complementarity of the chemical components among the three (steel slag provides calcium silicate minerals, blast furnace slag provides active silica-alumina components, and carbide slag provides an alkaline activation environment), achieving efficient mutual activation and synergistic reaction. This significantly improves the final performance of unfired bricks without relying on external cement, providing an innovative solution for the high-value-added and full-scale resource utilization of bulk industrial solid waste.

[0015] Secondly, this invention creatively combines solid waste resource utilization with carbon capture and utilization, forming a technological path of treating waste with waste. By actively introducing industrial flue gas emitted from coal-fired power plants and other sources as a carbonization curing medium, the CO2 in the waste gas reacts with the active calcium components (mainly from steel slag and carbide slag) in the brick body to generate stable calcium carbonate crystals. This process not only strengthens the early structure of the brick body but also achieves permanent mineral sequestration of CO2, resulting in direct carbon emission reduction benefits. Some formulations even achieve net negative carbon emissions.

[0016] Finally, based on the aforementioned material design and process innovations, the prepared all-solid-waste non-fired bricks exhibit excellent comprehensive performance. Their 28-day compressive strength reaches 18.2 to 39.1 MPa, water absorption is less than 15%, and softening coefficient is greater than 0.85, fully meeting the performance requirements of relevant national standards for non-sintered wall materials. They can be used for load-bearing or self-supporting walls. While possessing excellent mechanical properties and durability, this product also has a lower production cost than commercially available ordinary concrete bricks, combining environmental friendliness and economic competitiveness, thus opening up a practical new path for the development and large-scale application of green and low-carbon building materials. Attached Figure Description

[0017] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the preparation process of the all-solid waste low-carbon non-fired brick provided by the present invention.

[0019] Figure 2 XRD patterns of all-solid-waste low-carbon non-fired bricks under different curing conditions.

[0020] Figure 3 Thermogravimetric analysis diagrams of low-carbon, non-fired bricks made entirely from solid waste under different curing conditions.

[0021] Figure 4 The images show the microstructure of low-carbon, non-fired bricks made entirely from solid waste under different curing conditions. (a) shows the microstructure of the uncarbonized bricks; (b) shows the microstructure of the bricks after 24 hours of carbonization; and (c) shows the microstructure of the bricks after 24 hours of carbonization plus 27 days of conventional curing.

[0022] Figure 5 The diagram shows a comparison of the pore size distribution of Examples 1-3 and Comparative Example 1. Detailed Implementation

[0023] The following are specific embodiments of the present invention, described in conjunction with the accompanying drawings, to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments. Specific details, such as particular configurations, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention.

[0024] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified. The chemical compositions of the steel slag, ore slag, and carbide slag mentioned in the examples are shown in Table 1.

[0025] Table 1. Chemical composition of steel slag, mineral slag, and calcium carbide slag / wt.%

[0026] Example 1: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 35 parts steel slag, 35 parts ore slag, 30 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blank in a carbonization curing box with a temperature of 20±2 ℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 4 hours. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0027] Example 2: A low-carbon, non-fired brick made entirely from solid waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 35 parts steel slag, 35 parts ore slag, 30 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blanks in a carbonization curing box with a temperature of 20±2 ℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 8 hours. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0028] Example 3: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 35 parts steel slag, 35 parts ore slag, 30 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blanks in a carbonization curing box with a temperature of 20±2℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 24 hours. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0029] Example 4: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 45 parts steel slag, 45 parts ore slag, 10 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blank in a carbonization curing box with a temperature of 20±2 ℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 24 h. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0030] Example 5: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 40 parts steel slag, 40 parts ore slag, 20 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blank in a carbonization curing box with a temperature of 20±2 ℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 24 h. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0031] Example 6: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The specific preparation method of the all-solid-waste low-carbon non-fired brick is as follows: (1) According to the weight ratio, put 30 parts steel slag, 30 parts ore slag, 40 parts calcium carbide slag and 20 parts water into a mixer and mix for 5 minutes to obtain slurry; (2) The slurry is placed in the mold and pressed statically for 2 minutes under a pressure of 15 MPa by a brick press to obtain a brick blank; (3) Place the brick blank in a carbonization curing box with a temperature of 20±2 ℃ and a humidity of 60~80%, and introduce industrial waste gas with a volume concentration of 10% CO2. When the gas pressure reaches 0.1 MPa, carry out carbonization curing for 24 h. (4) After carbonization, the brick blanks are transferred to a curing room with a temperature of 20±2 ℃ and a humidity of ≥95% and continue to be cured for 27 days to obtain all-solid waste low-carbon non-fired bricks.

[0032] Comparative Example 1: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 1 is as follows: In steps (3) and (4), after the brick blank is pressed and formed, it is directly subjected to conventional curing for 28 days to obtain all-solid waste low-carbon non-fired bricks.

[0033] Comparative Example 2: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 1 is as follows: In steps (3) and (4), after the brick blank is pressed and formed, it is first cured for 27 days, and then placed in a carbonization curing box for 24 hours of carbonization curing to obtain all-solid waste low-carbon non-fired brick.

[0034] Comparative Example 3: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In steps (3) and (4), the carbonization curing time is 48 hours and the conventional curing time is 26 days.

[0035] Comparative Example 4: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 47 parts steel slag, 47 parts ore slag, 6 parts calcium carbide slag and 20 parts water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0036] Comparative Example 5: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 70 parts steel slag, 30 parts ore slag and 20 parts water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0037] Comparative Example 6: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 50 parts steel slag, 50 parts ore slag and 20 parts water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0038] Comparative Example 7: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 30 parts steel slag, 70 parts ore slag and 20 parts water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0039] Comparative Example 8: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 70 parts steel slag, 30 parts carbide slag and 20 parts water are put into a mixer and mixed for 5 minutes by weight to obtain slurry.

[0040] Comparative Example 9: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 50 parts steel slag, 50 parts carbide slag and 20 parts water are put into a mixer and mixed for 5 minutes by weight to obtain slurry.

[0041] Comparative Example 10: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 70 parts slag, 30 parts calcium carbide slag and 20 parts water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0042] Comparative Example 11: A Low-Carbon, Non-Firing Brick Made entirely from Solid Waste The difference from Example 3 is that: In step (1), 50 parts of slag, 50 parts of carbide slag and 20 parts of water are put into a mixer and mixed for 5 minutes to obtain a slurry.

[0043] The formulation and maintenance methods of Examples 1-6 and Comparative Examples 1-11 are summarized in Table 2.

[0044] Table 2. Formulation and curing methods of Examples 1-6 and Comparative Examples 1-11

[0045] The compressive strength, water absorption rate, and softening coefficient of the all-solid waste low-carbon non-fired bricks were determined according to JC / T 422-2025 "Non-sintered waste tailings bricks" in Examples 1-6 and Comparative Examples 1-11. The dry density of the all-solid waste low-carbon non-fired bricks was tested by drying. The phase composition of the all-solid waste low-carbon non-fired bricks was tested by X-ray diffraction (XRD). The phase change and carbon fixation rate of the all-solid waste low-carbon non-fired bricks were tested by thermogravimetric analysis (TG). The microstructure of the all-solid waste low-carbon non-fired bricks was observed by scanning electron microscopy (SEM). The pore size distribution and porosity of the all-solid waste low-carbon non-fired bricks were tested by mercury intrusion porosimetry (MIP).

[0046] The specific test results are shown in Table 3: Table 3 Test results of Examples 1-6 and Comparative Examples 1-11

[0047] Depend on Figure 2 The XRD patterns revealed that in the uncarbonized bricks, Ca(OH)₂ originated from carbide slag, while C₃S and C₂S originated from steel slag. The active SiO₂ and Al₂O₃ provided by the slag were in amorphous form and did not show corresponding diffraction peaks. After carbonization, the diffraction peak intensities of Ca(OH)₂, C₃S, and C₂S all decreased, while the diffraction peak intensity of CaCO₃ significantly increased. This indicates that Ca(OH)₂ reacted with CO₂ to form CaCO₃, and that C₃S and C₂S also reacted with CO₂ to form CaCO₃ and amorphous silica gel (silica gel showed no diffraction peaks). Further conventional curing of the carbonized bricks showed a further decrease in the diffraction peak intensities of C₃S and C₂S, indicating that they underwent a hydration reaction to generate Ca(OH)₂ and CSH (CSH showed no diffraction peaks). The generated Ca(OH)₂ helps maintain the alkaline environment of the system, thereby activating the potential activity of the slag.

[0048] from Figure 3Thermogravimetric analysis revealed that after carbonization curing, the CaCO3 content in the bricks increased significantly, by 18.8%, while the Ca(OH)2 content decreased from 8.6% in the uncarbonized bricks to 2.1%, indicating that the carbonization reaction consumed most of the Ca(OH)2, but still retained a certain amount. Further conventional curing of the carbonized bricks resulted in a decrease in Ca(OH)2 content from 2.1% to 1.7%, while the bound water content increased by 1.6% within the temperature range of 60–250 °C. This change indicates that the Ca(OH)2 generated from the hydration of C3S and C2S, as well as the remaining Ca(OH)2 after carbonization, underwent a hydration reaction with the active SiO2 and Al2O3 in the slag, generating the cementitious product C-(A)-SH.

[0049] from Figure 4 The microstructure reveals that the uncarbonized bricks rely solely on the mechanical bonding force during pressing to agglomerate solid waste particles, lacking effective chemical bonding between the particles. Consequently, the surface structure is loose, and internal pores are prominent. After carbonization curing, a large number of CaCO3 crystals are generated inside the bricks, effectively filling the pores. Simultaneously, the amorphous silica gel produced by the carbonization reaction binds some of the solid waste particles together, making the microstructure denser. Further curing of the carbonized bricks results in the newly generated cementing product C-(A)-SH forming a strong chemical bond and physical interweaving network between the solid waste particles, further filling the micropores. This optimization of the microstructure enhances the mechanical properties and durability of the bricks.

[0050] according to Figure 5 The pore size distribution test results of Examples 1-3 and Comparative Example 1 show that, compared with the uncarbonized Comparative Example 1, after carbonization curing with CO2 waste gas, the pore size of the bricks shows a continuous decreasing trend, and the total porosity decreases significantly with the extension of carbonization time. This change indicates that the CaCO3 and silica gel products generated by the carbonization reaction can effectively fill the pores and microcracks inside the brick, thereby optimizing the pore structure and improving the density. This result is consistent with... Figure 4 The results of the microscopic morphology observations shown are consistent, further verifying the effect of carbonization curing on improving the microstructure of bricks.

[0051] As shown in Example 3 and Comparative Examples 1-2, the sequence of carbonization curing followed by conventional curing significantly promotes brick performance better than the sequence of conventional curing followed by carbonization curing. This is because the CaCO3 crystals generated during carbonization curing provide nucleation sites for the hydration of C-(A)-SH gel during subsequent conventional curing, thereby promoting the degree of hydration reaction and benefiting the development of brick strength. Conversely, if conventional curing is performed first, the hydration product C-(A)-SH is generated first. During subsequent carbonization curing, CO2 reacts with C-(A)-SH, causing it to decompose into CaCO3, silica gel, and alumina gel. Although the carbonization products can fill some pores, their cementing properties are reduced, resulting in a weaker improvement in the overall brick performance compared to the sequence of carbonization followed by curing. Therefore, in the preparation process of this all-solid-waste low-carbon non-fired brick, the process sequence of carbonization followed by conventional curing is more conducive to optimizing the mechanical properties of the brick.

[0052] As shown in Example 3 and Comparative Example 3, the strength of the brick actually decreased after the carbonization time exceeded 24 hours. This is because an excessively high initial carbonization degree leads to excessive consumption of Ca(OH)2 in the system, resulting in a lack of sufficient alkaline activators to activate the hydration reaction of the slag during subsequent curing. This affects the amount of hydration products generated, ultimately limiting the development of the brick's strength.

[0053] As shown in Examples 3-6 and Comparative Example 4, the strength of the brick decreases significantly when the content of calcium carbide slag is less than 10%. This is because the Ca(OH)2 in the brick mainly comes from calcium carbide slag, and insufficient content cannot effectively activate the hydration activity of the slag, resulting in incomplete hydration reaction and a significant decrease in strength.

[0054] Based on Examples 3-6 and Comparative Examples 5-11, it can be observed that, under the same carbonization conditions, the ternary system composed of steel slag, blast furnace slag, and carbide slag exhibits significantly better performance than the binary system composed of any two of these solid wastes. This advantage stems from the synergistic effect among the three components: during the carbonization curing stage, steel slag and carbide slag, as the main calcium sources, participate in the reaction to generate silica gel and CaCO3, constructing an early strength framework; in subsequent conventional curing, the active SiO2 and Al2O3 provided by the blast furnace slag, under the stimulation of the hydration products of steel slag and the residual components of carbide slag, continuously form cementing products such as C-(A)-SH, further filling pores and optimizing the microstructure, achieving a synergistic increase in mechanical strength and durability. It is noteworthy that the reactivity of Ca(OH)2, the main component in carbide slag, is higher than that of silicate minerals in steel slag; therefore, appropriately increasing its dosage can further enhance the performance improvement effect.

[0055] Comparative Examples 5-7 lacked calcium carbide slag, resulting in insufficient alkaline activators and incomplete release of slag activity. Comparative Examples 8-9 lacked slag, resulting in a lack of available silica-alumina components for activation during the conventional curing stage, which limited the continuous generation of cementitious products. Comparative Examples 10-11 did not use steel slag, resulting in a lack of silica gel and other products during the carbonization stage, which affected the early skeleton construction and the generation of later hydration products, ultimately leading to a decrease in strength.

[0056] The low-carbon, non-fired brick prepared by this invention has a compressive strength greater than 15 MPa, a water absorption rate less than 15%, and a softening coefficient greater than 0.85. These indicators not only meet the requirements of JC / T 422-2025 "Non-sintered Waste Tailings Bricks" standard, but also comply with the provisions of GB 50574-2010 "Unified Technical Specification for Application of Wall Materials" regarding the block materials for load-bearing walls and self-supporting walls (as shown in Table 4). This brick exhibits good adaptability and demonstrates excellent potential for engineering applications.

[0057] Table 4 Performance Requirements for Load-Bearing Wall and Self-Supporting Wall Block Materials

[0058] According to the process flow of this invention, the cost system is divided into material cost, molding cost, carbonization cost, and maintenance cost, calculated as follows. It should be noted that the material prices and equipment parameters mentioned below were obtained through market research.

[0059] (1) Material cost The price of slag is approximately 200 yuan / ton. Steel slag and calcium carbide slag have large production volumes but low utilization rates. The raw materials are free, but they need to be crushed, ground, and screened by the manufacturer. The crushing equipment uses a hammer crusher with a production capacity of 50 tons / hour and an operating power of 132 kW; the grinding equipment uses a vertical roller mill (also for screening), with a production capacity of 50 tons / hour and an operating power of 1250 kW. The price of industrial electricity in my country is approximately 0.6 yuan / kWh. Therefore, the processing cost of steel slag and calcium carbide slag is calculated to be approximately 16.6 yuan / ton. The price of industrial water is approximately 5 yuan / ton. The total raw material mass of a single brick is 2.6 kg. The material cost per brick is obtained by summing the products of the mass ratios of steel slag, slag, calcium carbide slag, and water with their respective prices.

[0060] (2) Molding cost The brick press has a production capacity of 7200 bricks / hour and an operating power of 26 kilowatts. The calculated molding cost is 0.0022 yuan / brick.

[0061] (3) Carbonization cost The CO2 industrial waste gas originates from the flue gas of coal-fired power plants, and its cost is considered zero. The carbonization curing chamber has a volume of 0.72 m³. 3Assuming a 50% utilization rate, approximately 200 bricks can be placed at a time, with an operating power of 1 kilowatt. The carbonization cost is calculated as the product of carbonization time, operating power, and electricity price.

[0062] (4) Maintenance costs The curing room has a volume of 60 m³. 3 Considering a 50% utilization rate, approximately 20,000 bricks can be placed each time, with an operating power of 5 kilowatts. The calculated maintenance cost is 0.0972 yuan per brick.

[0063] The cost analysis results of Examples 1-6 are shown in Table 5. As can be seen from the table, the cost per brick is between 0.2909 and 0.3911 yuan, which is lower than the market price of 0.4500 to 0.6500 yuan per brick for commercially available ordinary concrete bricks. This indicates that the all-solid-waste low-carbon non-fired bricks prepared in this invention have significant economic advantages.

[0064] Table 5 Cost Analysis of Examples 1-6 (in RMB)

[0065] The carbon emission calculation boundary of this invention is from "cradle" to "gate," covering carbon emissions during the raw material acquisition, transportation, and production stages, and deducting CO2 absorbed during the carbonization and curing process. It should be noted that the following carbon emission factors are all derived from GB / T51366-2019 "Standard for Calculation of Carbon Emissions in Buildings."

[0066] (1) Carbon emissions from raw materials Steel slag, mineral slag, and calcium carbide slag are all industrial wastes, and their upstream carbon emissions are calculated to be 0. The carbon emission factor of tap water is 0.168 kg CO2 / t. The carbon emissions of raw materials are calculated based on the product of the water mass ratio and its emission factor. The calculated carbon emissions of raw materials for each brick are 0.00007 kg CO2.

[0067] (2) Carbon emissions from transportation The default transportation distance for raw materials is 500 km, using heavy-duty diesel trucks, with a carbon emission factor of 0.078 kgCO2 / (t·km). Based on this, the carbon emission from transporting each ton of raw materials is 39 kg CO2, and the carbon emission from transporting each brick is 0.08557 kg CO2.

[0068] (3) Production energy consumption and carbon emissions The carbon emission factor for electricity used in production is the average value of the Southern Regional Power Grid, which is 0.5271 kg CO2 / kWh.

[0069] Crushing, grinding, and screening: The production capacity of the crushing, grinding, and screening process for steel slag and carbide slag is 50 tons / hour, with a total power of 1382 kW. The carbon emissions per ton of raw material processed are 14.5690 kg CO2. The carbon emissions per brick are calculated by weighting the amounts of each component according to their mass proportions.

[0070] Compression molding: The brick press has a production capacity of 7200 bricks / hour, an operating power of 26 kW, and a carbon emission of 0.0019 kg CO2 per brick.

[0071] Carbonization curing: The carbonization curing box has a capacity of 200 bricks / cycle, an operating power of 1 kW, and a carbon emission of 0.0026 kg CO2 per brick per hour.

[0072] Routine maintenance: The curing chamber has a capacity of 20,000 bricks / cycle, an operating power of 5 kW, and carbon emissions of 0.0001 kg CO2 per brick per hour.

[0073] The total carbon emissions during the production phase are the sum of the carbon emissions from the crushing, grinding, screening, pressing, carbonization, and routine maintenance processes mentioned above.

[0074] (4) Carbon sequestration The carbon fixation amount is obtained by multiplying the mass of a single brick by its carbon fixation rate, where the carbon fixation rate is taken from the measured values ​​of Examples 1 to 6.

[0075] The carbon emission analysis results of Examples 1-6 are summarized in Table 6. As shown in the table, the carbon emission range of the all-solid-waste low-carbon non-fired brick prepared in this invention is -0.00474 to 0.09052 kg CO2 / brick, which is approximately -3.24 to 61.88 kg CO2 / m³. 3 It is far lower than the 134–336 kg CO2 / m³ of ordinary bricks. 3 In Example 6, the carbon sequestration amount exceeded the sum of emissions from raw material acquisition, transportation, and production, achieving net carbon negative emissions and fully demonstrating the excellent low-carbon characteristics of this invention.

[0076] Table 6 Carbon emission analysis of Examples 1-6 / kg CO2

[0077] In summary, this invention involves mixing, stirring, and pressing steel slag, mineral slag, and calcium carbide slag in a specific ratio, followed by CO2 industrial waste gas for carbonization curing. After conventional curing, high-performance, low-carbon, non-fired bricks made entirely from solid waste are formed. In this material system, steel slag and calcium carbide slag serve as key calcium sources in the carbonization reaction, constructing an early-stage strength framework primarily composed of silica gel and CaCO3. During conventional curing, the active silica-alumina components in the mineral slag continuously react in an alkaline environment, generating various cementitious products that further optimize the microstructure. This process not only achieves resource utilization of industrial solid waste and CO2 fixation but also effectively improves the overall performance of the non-fired bricks, demonstrating promising engineering application prospects and economic benefits.

[0078] Those skilled in the art to which this application pertains may modify or supplement the specific embodiments described or use similar methods to replace them, but without departing from the inventive concept of this application or exceeding the scope defined by the appended claims.

Claims

1. A low-carbon, non-fired brick made entirely from solid waste, characterized in that, It contains the following raw materials in parts by weight: 30-45 parts steel slag, 30-45 parts blast furnace slag, 10-40 parts calcium carbide slag and 20 parts water.

2. The all-solid-waste low-carbon non-fired brick according to claim 1, characterized in that, The main components of the steel slag are CaO and Fe2O3; the main components of the ore slag are CaO, SiO2 and Al2O3; and the main component of the carbide slag is CaO.

3. A method for preparing a low-carbon, non-fired brick made entirely from solid waste as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Mix steel slag, mineral slag, calcium carbide slag and water for 3-5 minutes to obtain a slurry; (2) The slurry is statically pressed under a pressure of 10-20 MPa for 2-3 minutes to obtain a brick blank; (3) Place the brick blank in a carbonization curing environment with a temperature of 20±2℃ and a humidity of 60~80%, introduce CO2 industrial waste gas until the gas pressure reaches 0.1MPa, and perform carbonization curing for 4~24 hours; (4) After carbonization, the brick blank is transferred to an environment with a temperature of 20±2℃ and a humidity of ≥95% for conventional curing for 26 to 28 days to obtain the all-solid waste low-carbon non-fired brick.

4. The preparation method according to claim 3, characterized in that, In step (3), the CO2 industrial waste gas comes from the flue gas of a coal-fired power plant, and its CO2 volume concentration is 10%.

5. The preparation method according to claim 3, characterized in that, In step (3), the carbonization curing time is 8 to 24 hours.

6. The preparation method according to claim 3, characterized in that, In step (3), the carbonization curing time is 24 hours.

7. The preparation method according to claim 3, characterized in that, In step (1), the weight parts of the steel slag, ore slag, carbide slag and water are 35 parts steel slag, 35 parts ore slag, 30 parts carbide slag and 20 parts water, respectively.

8. The preparation method according to any one of claims 3-7, characterized in that, The dry density of the prepared all-solid-waste low-carbon non-fired bricks is 1.58–1.68 g / cm³.

9. The preparation method according to any one of claims 3-7, characterized in that, The 28-day compressive strength of the prepared all-solid-waste low-carbon non-fired bricks is 18.2–39.1 MPa.

10. The preparation method according to any one of claims 3-7, characterized in that, The carbon fixation rate of the prepared all-solid waste low-carbon non-fired bricks is 5.2-10.0%, the water absorption rate after 28 days is less than 15%, and the softening coefficient is greater than 0.85.

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