A method for utilizing wet-ground steel slag in-situ wet carbonization whole slurry

Abstract

The application discloses a kind of wet grinding steel slag in situ wet carbonization whole pulp utilization method, specifically related to solid waste resource utilization and low-carbon cementing material preparation technical field.The method is first to wet grinding steel slag whole pulp into carbon dioxide gas and is short in situ wet carbonization, and active calcium magnesium component in steel slag that can cause volume instability is preferentially carbonized, and fine and dispersed carbonate particles are generated in situ in whole pulp;Subsequently, without dehydration, drying and regrinding, directly obtained carbonized steel slag whole pulp is mixed with slag, gypsum, sand and stone, and solid waste-based building material products are prepared by forming and curing.The method utilizes in-situ carbonization to reduce the risk of steel slag volume expansion, and simultaneously utilizes the dispersed carbonate particles, liquid phase environment and particle dispersion conditions formed during carbonization to improve the reaction efficiency and structure formation ability of the subsequent mixing system, thereby achieving simultaneous optimization of fluidity, compressive strength and volume stability.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and low-carbon cementitious material preparation technology, and more specifically, to a method for in-situ wet carbonization and pulping utilization of wet-milled steel slag. Background Technology

[0002] Steel slag is a large-scale industrial solid waste generated during the iron and steel smelting process. It contains a certain amount of silicates, ferrates, and calcium and magnesium components, and has certain potential cementing activity and resource utilization value. Applying steel slag to building materials systems can not only help reduce the pressure of solid waste storage, but also partially replace traditional cementing raw materials, resulting in good environmental and economic benefits.

[0003] Existing patents have disclosed numerous technical solutions related to the resource utilization of steel slag. One type of technology mainly focuses on the preparation of steel slag-slag-gypsum composite cementitious materials. This typically uses dry powders such as steel slag, slag, and gypsum as the raw materials, obtaining the cementitious material through methods such as mixing and grinding, graded circulation, proportion optimization, or activation treatment. For example, existing patent CN111362599A discloses a method for preparing steel slag-slag-gypsum composite cementitious materials through mixing and grinding. Its core technical route involves mixing steel slag particles, slag, and gypsum, followed by grinding, air classification, and circulation treatment to obtain the cementitious material. This type of solution focuses primarily on the synergistic grinding of powder raw materials and the optimization of the cementitious material composition.

[0004] Another type of technology in existing patents mainly focuses on the carbonation treatment of steel slag and the utilization of carbonized building materials. For example, some technical solutions target the regulation of calcium carbonate crystal form in carbonized steel slag slurry by introducing carbon dioxide into the steel slag slurry and adding crystal form control agents to improve the activity of steel slag and the subsequent performance of concrete. The focus of this type of solution is on the control of the carbonation process, crystal form regulation, or the carbonation products themselves, rather than the direct engineering utilization of the carbonized slurry.

[0005] In addition, there are technical solutions that utilize wet-milled steel slag slurry directly in the preparation of subsequent materials. For example, existing patent CN112374843A discloses a method for preparing mine backfill concrete using wet-milled steel slag slurry. This method connects the wet milling process with the backfill material preparation process and replaces part of the mixing water with water used in wet milling to improve the utilization rate of steel slag. Although this type of technology involves the direct utilization of wet-milled steel slag slurry, its application is mainly for mine backfill materials, and the technical focus is on the preparation of backfill materials, rather than on the direct utilization of the whole slurry after in-situ wet carbonization of the wet-milled steel slag slurry.

[0006] A review of existing patents reveals that while current technologies have made some progress in areas such as steel slag-slag-gypsum composite cementitious materials, steel slag carbonization treatment, and the utilization of wet-milled steel slag slurry, they still have the following shortcomings: First, most existing steel slag-slag-gypsum patents focus on dry powder, typically requiring separate grinding, dehydration, drying, or further grinding before subsequent utilization, resulting in a long process chain. Second, existing steel slag carbonization patents primarily focus on the control of carbon fixation, carbonization conditions, or carbonization products, neglecting the need for further research on the application of steel slag-slag-gypsum composite cementitious materials, steel slag carbonization treatment, and the utilization of wet-milled steel slag slurry. Third, existing technologies lack specific design considerations regarding the differences in performance, reaction synergy, and volume stability between "direct utilization of carbonized slag slurry" and "utilization of dry powder after carbonization"; fourth, there is a lack of a method that uses wet-milled steel slag slurry as the direct target, performs in-situ wet carbonization under normal pressure and short-time conditions, and integrates the liquid phase environment and the finely dispersed particles generated in-situ into the subsequent mixing system without dehydration, drying, or re-grinding.

[0007] Therefore, there is an urgent need in the field for a wet carbonization method for steel slag that requires no additional post-processing and can be directly used as a slurry. This method can reduce the risk of steel slag volume expansion while fully preserving the liquid phase environment, particle dispersion state, and finely dispersed carbonate particles generated in situ during carbonization, thereby improving the overall working performance, reaction efficiency, and volume stability of the subsequent mixing system containing slag, gypsum, and aggregates. Summary of the Invention

[0008] To overcome the aforementioned deficiencies of the prior art, this invention provides a method for utilizing wet-milled steel slag in situ using wet carbonization. This method involves short-time in-situ wet carbonization of the wet-milled steel slag slurry, followed by direct use of the resulting carbonized steel slag slurry, along with a liquid environment, to prepare a solid waste-based building material mixture containing slag, gypsum, sand, and gravel, without dewatering, drying, or re-grinding. The mixture is then molded and cured to obtain solid waste-based building material products. This method simplifies the process, enables direct utilization of the slurry, and synergistically improves workability, mechanical properties, and volume stability, thus solving the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for utilizing wet-milled steel slag through in-situ wet carbonization pulping includes the following steps: Step 1: The wet-milled steel slag slurry is subjected to in-situ wet carbonization treatment by introducing a gas containing carbon dioxide under stirring conditions, so that the active calcium and magnesium components in it undergo carbonization reaction to obtain carbonized steel slag slurry. Step 2: The carbide steel slag slurry is directly mixed with slag, gypsum, sand and gravel without dewatering, drying and re-grinding to obtain solid waste-based concrete mixture. Step 3: The solid waste-based concrete mixture is molded and cured to obtain solid waste-based building materials.

[0010] As a further embodiment of the present invention, the wet-milled steel slag slurry in step one is obtained by mixing steel slag and water at a solid-liquid ratio of 1:1 to 1:10 and then wet-milling it.

[0011] As a further aspect of the present invention, the wet grinding process employs one or more of ball milling, stirring milling, and sand milling.

[0012] As a further aspect of the present invention, the in-situ wet carbonization in step one is carried out under normal pressure.

[0013] As a further aspect of the present invention, the concentration of carbon dioxide gas introduced in step one is 10% to 99%.

[0014] As a further embodiment of the present invention, the carbon dioxide gas flow rate is 5-20 L / min / 1 kg steel slag, the carbonization time is 5-20 min, and the stirring speed is 500-3000 rpm.

[0015] As a further aspect of the present invention, the carbonized steel slag slurry obtained in step one is mixed together with the liquid phase environment in the subsequent mixing process.

[0016] As a further embodiment of the present invention, in step two, the steel slag solid phase, slag and gypsum contained in the carbide steel slag slurry are used as cementing components, and the ratio of the three by mass is 4:5:1.

[0017] As a further aspect of the present invention, the solid waste-based building materials are mortar products, concrete block products, or other molded products.

[0018] As a further aspect of the present invention, the dispersed carbonate particles formed in the carbide steel slag slurry participate in the subsequent mixing system structure formation process, and are beneficial to the formation and deposition of slag hydration reaction products.

[0019] The technical effects and advantages of the present invention regarding the in-situ wet carbonization and pulping method for utilizing wet-milled steel slag are as follows: This invention adopts a continuous process path of "wet grinding and pulping - in-situ wet carbonization - direct use of whole pulp", which enables steel slag to complete pretreatment, carbonization and subsequent utilization in the pulp state, without the need for dewatering, drying and re-grinding. This shortens the process flow, reduces energy consumption and material transportation costs, has lower equipment requirements, and is easy to scale up and apply in engineering.

[0020] This invention performs in-situ wet carbonization of wet-milled steel slag slurry under normal pressure, short time, and stirring conditions. This process preferentially converts the active calcium and magnesium components in the steel slag, which are prone to volume instability, into stable carbonate phases. This reduces the risk of expansion in subsequent use of the steel slag from the source, while avoiding potential activity loss due to over-treatment, thus achieving a balance between stabilization and activity preservation.

[0021] This invention preserves the liquid phase environment, particle dispersion state, and in-situ generated fine dispersed carbonate particles in the carbide steel slag slurry, allowing it to be directly incorporated into the subsequent mixing system containing slag, gypsum, and aggregates. This improves particle wetting and dispersion conditions, provides favorable interfaces and nucleation sites, and enhances the synergistic reaction and structure-forming ability of the solid waste-based building materials system.

[0022] The results of the embodiments and comparative examples of this invention show that the system using carbonized steel slag for direct utilization of the whole slurry is superior to the uncarbonized steel slag powder system, the uncarbonized steel slag slurry system, and the carbonized dry powder system in terms of fluidity, mechanical properties, and volume stability. This indicates that its technical effect comes from the synergistic effect formed by the combination of in-situ wet carbonization and direct utilization of the whole slurry. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of an in-situ wet carbonization and pulping method for utilizing wet-milled steel slag according to the present invention. Figure 2 This is a schematic diagram of the system structure formed by the participation of carbide steel slag slurry in subsequent mixing in this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment is based on a pilot-scale test of converter steel slag resource utilization in a steel enterprise, and specifically describes a method for in-situ wet carbonization and slurry utilization of wet-milled steel slag according to the present invention. The steel slag used in this embodiment originates from the converter steelmaking process and is reserved after conventional magnetic separation to remove recoverable metallic iron. This steel slag contains silicates, ferrates, and calcium-magnesium components, possessing certain potential cementitious activity, and also contains a certain amount of active calcium-magnesium components that may cause volume changes during subsequent use. Granulated blast furnace slag powder is used as the slag, industrial by-product gypsum is used, medium sand is used, continuously graded crushed stone is used, and conventional industrial water is used for the process. The entire implementation process includes several continuous steps: steel slag pretreatment, wet milling and slurry preparation, in-situ wet carbonization, direct mixing of the carbonized slurry, molding, and standard curing. There are no interruptions in dewatering, drying, and re-milling processes between each step, allowing the wet-milled steel slag to continuously complete carbonization and subsequent utilization in a slurry state.

[0027] like Figure 1 As shown, the overall process flow of this embodiment includes the following continuous processes: steel slag is pretreated and mixed with water, and then enters the wet grinding and slurry preparation process to form a uniformly dispersed wet-ground steel slag slurry; the wet-ground steel slag slurry enters a reaction vessel equipped with a gas introduction device and a high-speed stirring device, and carbon dioxide-containing gas is introduced under normal pressure to carry out in-situ wet carbonization, forming a carbonized steel slag slurry; the obtained carbonized steel slag slurry is kept in slurry state and, without dewatering, drying and re-grinding, directly enters the mixing process with slag, gypsum, sand and gravel to form a solid waste-based building material mixture; the solid waste-based building material mixture is molded and standard cured to obtain solid waste-based building material products.

[0028] First, steel slag pretreatment and wet grinding are performed. The magnetically separated steel slag is crushed and screened to ensure that the particle size of the steel slag before entering the wet grinding process is no greater than 5 mm, so as to ensure that the steel slag can be uniformly dispersed in a short time. Then, steel slag and water are weighed and added to a wet stirred mill at a solid-liquid ratio of 1:5 for wet grinding. This solid-liquid ratio is within the process range of 1:1 to 1:10. At this ratio, the slurry has sufficient fluidity to facilitate subsequent aeration and stirring, while maintaining a high solid content, which is convenient for direct entry into the mixing system.

[0029] The wet grinding equipment uses a stirred mill with a rotation speed of 1200 rpm and a grinding time of 30 minutes. During the wet grinding process, the steel slag particles are continuously subjected to shearing, collision, and friction in the liquid medium. The outer surface of the particles is constantly renewed, and the initially coarser steel slag particles gradually disintegrate, local agglomerates are broken up, and the steel slag particles are suspended and dispersed in the aqueous phase in a more uniform manner. As the wet grinding process progresses, the system gradually transforms from an initial state of coarse particle suspension to a uniformly dispersed and continuously flowing wet-ground steel slag slurry. The slurry obtained after wet grinding is grayish-black, with a stable overall state. No obvious large particle settling, stratification, or local agglomeration is observed by the naked eye, indicating that the steel slag has completed the transformation from a granular state to a continuously transportable slurry state.

[0030] Wet milling disperses and refines steel slag in an aqueous environment, creating suitable liquid phase conditions for subsequent carbonization. After wet milling, the outer surface of the steel slag particles has more sufficient contact with the liquid phase, and the solid-liquid interface inside the slurry is richer. When carbon dioxide gas is subsequently introduced, the carbon dioxide can diffuse and transfer under more uniform interface conditions. The steel slag maintains a continuous slurry morphology throughout the treatment process, which helps reduce intermediate transfer and state transition steps and provides a stable slurry environment for the subsequent formation of fine dispersed particles.

[0031] After wet milling, the resulting wet-milled steel slag slurry is directly transferred to a carbonization reaction vessel for in-situ wet carbonization. The reaction vessel used is a vertical, closed stirred tank, equipped with a high-speed mechanical agitator and a gas inlet device at the bottom. The gas inlet device is a porous disperser with a gas inlet on the side wall, allowing carbon dioxide-containing gas to be introduced into the slurry through bubbling, the disperser, or the gas inlet pipe. This reaction vessel maintains thorough mixing of the slurry during aeration and forms numerous fine bubbles when the gas enters the slurry, thereby improving gas-liquid contact efficiency. The carbonization process is carried out under normal pressure without applying additional pressure. Before aeration, the agitator is started and the agitation speed is adjusted to 2000 rpm. Then, carbon dioxide-containing gas is continuously introduced into the wet-milled steel slag slurry. In this embodiment, the carbon dioxide concentration is 50%, falling within the applicable range of 10% to 99%; the gas flow rate is controlled at 10 L / min, falling within the range of 5 to 20 L / min / 1 kg steel slag slurry; and the aeration time is controlled at 10 min, falling within the range of 5 to 20 min.

[0032] During carbonization, carbon dioxide-containing gas enters the wet-milled steel slag slurry through a bottom disperser, forming numerous fine bubbles that are rapidly dispersed throughout the slurry volume under high-speed stirring. Due to the high stirring speed, continuous circulation occurs within the slurry, maintaining a high bubble turnover rate. This allows carbon dioxide to continuously diffuse from the bubble surface into the liquid phase and migrate around the steel slag particles. Since the steel slag particles have already been sufficiently dispersed in the previous wet milling process, their surfaces are fully exposed, enabling the active calcium and magnesium components to react with carbon dioxide under relatively uniform contact conditions. As the reaction proceeds, the active components in the steel slag that easily cause subsequent volume changes gradually transform, and fine dispersed particles are simultaneously generated within the slurry. These particles are directly exposed to the liquid phase environment after formation and maintain a uniform distribution under stirring. The entire carbonization process is carried out continuously within the slurry, ensuring that the generation and dispersion of fine dispersed particles are completed under the same process conditions.

[0033] This embodiment employs a carbonization process under atmospheric pressure, short duration, and high-speed stirring. Atmospheric pressure facilitates continuous setup for pilot-scale and industrial production, short-duration aeration helps shorten the process cycle, and high-speed stirring enhances the gas-liquid-solid three-phase contact, allowing the carbonization process to proceed more uniformly within the slurry. After carbonization, aeration is stopped, and low-speed stirring continues for 1 minute to further eliminate local concentration differences, making the slurry more homogeneous, ultimately yielding a complete carbonized steel slag slurry.

[0034] The resulting carbonized steel slag slurry is directly fed into subsequent mixing processes in its slurry state without dewatering, drying, or re-grinding. The fine dispersed particles formed after carbonization, the liquid phase environment in the slurry, and the original dispersion state of the steel slag particles are all preserved and carried into the subsequent mixing system containing slag, gypsum, sand, and gravel. This allows the slag and gypsum to be quickly wetted and dispersed, while also facilitating the uniform distribution of sand and gravel in the mixture, thus forming a homogeneous solid waste-based building material mixture.

[0035] Subsequently, the solid waste-based building material mixture was prepared. The steel slag solid phase, slag, and gypsum contained in the carbide steel slag slurry were used as the cementing components, with a mass ratio of 4:5:1, where the steel slag portion was entirely provided by the aforementioned carbide steel slag slurry. In specific operation, slag, gypsum, sand, and gravel were first weighed according to the target ratio and premixed in a forced mixer. Then, all the carbide steel slag slurry was added, and an appropriate amount of process water was added according to the performance requirements of the mixture to ensure good homogeneity and formability. During the mixing process, the slag and gypsum were rapidly wetted and dispersed in the slurry liquid phase. Steel slag particles, the liquid phase environment, and fine dispersed particles formed during the carbide steel slag slurry simultaneously entered the mixing system, while sand and gravel were uniformly distributed as aggregates within the system. After mixing, the resulting solid waste-based building material mixture was uniform overall, without significant segregation, clumping, or severe bleeding, exhibiting good workability.

[0036] like Figure 2 As shown, after the carbide steel slag slurry enters the subsequent mixing system containing slag, gypsum, sand, and gravel, the fine dispersed particles formed within the slurry are uniformly distributed throughout the system and participate in the subsequent structural formation process together with the slag, gypsum, and aggregates. The steel slag particles, liquid phase, and fine dispersed particles in the slurry form a continuously distributed composite mixing structure after stirring. The slag particles are in full contact with the liquid phase in this system, the gypsum plays a reaction regulating role, and the fine dispersed particles provide uniformly distributed interface sites, resulting in good continuity and uniformity in the subsequent structural construction. These fine dispersed particles also act as nucleation sites in the system, promoting the formation and deposition of slag hydration reaction products.

[0037] In this subsequent mixing system, slag, as the main potential active component, participates in the subsequent hardening process, gypsum participates in reaction regulation, and the carbide steel slag slurry enters the system as a whole, providing the foundation for the composite structure. The fine, dispersed particles present in the slurry provide numerous uniformly distributed interfacial locations within the system. After entering this environment, slag particles can more quickly form reaction products near these interfaces and gradually accumulate, resulting in better continuity in the structural formation process within the system. Because the liquid phase environment carried by the slurry is completely preserved, slag, steel slag, and gypsum can exist under relatively uniform ion migration and particle contact conditions throughout the mixing stage. The resulting mixture exhibits good workability in the initial mixing stage and gradually forms a dense, hardened structure during subsequent curing.

[0038] The solid waste-based building material mixture is molded immediately after preparation. In this embodiment, the obtained mixture is poured into a 40mm×40mm×160mm prism mold for subsequent flexural and compressive strength testing; cubic specimens or other block-shaped specimens can also be prepared as needed. After pouring, the mold is placed on a vibrating table and vibrated for 30 seconds to ensure the mixture fully fills the mold and removes trapped air. After vibration, the surface of the specimen is smoothed and allowed to stand until initial setting before demolding. The demolded specimens are then cured under standard curing conditions, with a curing temperature controlled at 20±2℃ and a relative humidity not less than 95%. Curing periods are set at 3d, 7d, and 28d to examine the performance changes of the material in the early, middle, and late stages. The obtained material can be used to prepare solid waste-based mortar products, concrete block products, road base materials, and other low-carbon building materials.

[0039] To investigate the changes in the performance of the subsequent mixing system under different wet-process carbonized steel slag slurry blending conditions, experimental groups with different slurry dosages were set up under the same water-cement ratio. The proportions of slag and gypsum were kept consistent in each group, the steel slag portion was adjusted by both wet-process carbonized steel slag slurry and steel slag powder, and the aggregate dosage remained consistent. Samples from each group were treated using the same mixing, molding, and curing processes, and the resulting performance results are shown in Table 1.

[0040] Table 1. Performance results of subsequent mixing systems under different wet-process steel slag slurry blending conditions.

[0041] As shown in Table 1, under different wet-process steel slag slurry blending conditions, as the slurry ratio increased from 0% to 40%, the system fluidity increased from 170 mm to 235 mm, indicating that the addition of slurry to the system is beneficial to improving the dispersion state and workability of the mixture during the mixing and molding stages. In terms of mechanical properties, the compressive strength of the 40% slurry group at 3d, 7d, and 28d were 24.74 MPa, 38.50 MPa, and 48.48 MPa, respectively, significantly higher than the 18.095 MPa, 21.80 MPa, and 26.305 MPa of the 0% slurry group. Regarding flexural strength, the 40% slurry group reached 9.5 MPa and 12 MPa at 7d and 28d, respectively, also higher than the low slurry ratio group. Therefore, it can be seen that with the increase of the wet-process steel slag slurry ratio, the material exhibits a better overall performance trend in both the freshly mixed and hardened states. With the increase of the proportion of whole slag in wet carbonization of steel slag, the expansion rate of the system decreased significantly. The expansion rate of the 40% whole slag group was only 0.10%, which was significantly lower than the 3.00% of the 0% whole slag group. This result indicates that after in-situ wet carbonization of steel slag, the active calcium and magnesium components that are prone to volume instability are effectively treated, thereby reducing the expansion risk of steel slag in subsequent use and improving the volume stability of the system.

[0042] The results shown in Table 1 further illustrate that after steel slag is wet-milled into a slurry, it undergoes in-situ wet carbonization and is directly introduced into the subsequent mixing system containing slag, gypsum, and aggregate in a slurry state. This allows the particle dispersion state and liquid phase environment formed in the previous stage to continue into the next stage, thereby improving the fluidity, mechanical properties, and volume stability of the system.

[0043] In this embodiment, steel slag is first mixed with water and wet-milled to form a wet-milled steel slag slurry. Then, in a reaction vessel equipped with a gas introduction device and a high-speed stirring device, carbon dioxide gas is introduced into the slurry under normal pressure for short-term in-situ wet carbonization to obtain a carbonized steel slag slurry. Subsequently, the slurry is kept in a slurry state and, without dewatering, drying, or re-milling, is directly mixed with slag, gypsum, sand, and gravel to prepare a solid waste-based building material mixture. After molding and standard curing, the solid waste-based building material product is obtained. This implementation method has complete steps, clear parameters, and clear process connections, and can stably realize the direct utilization of wet-milled steel slag slurry in the solid waste-based building material system.

[0044] Example 2

[0045] This embodiment is carried out under the same raw material source and basic process route as Embodiment 1. Converter steel slag is still used as the steel slag source, granulated blast furnace slag powder as the slag component, industrial by-product gypsum as the gypsum component, medium sand as the sand, continuously graded crushed stone as the aggregate, and conventional industrial water as the process water. The steel slag is also first subjected to magnetic separation to remove recoverable metallic iron, and then crushed and screened to ensure that the particle size before entering the wet grinding process is no greater than 5 mm. The difference between this embodiment and Embodiment 1 is that only a portion of the steel slag component in the solid waste-based building materials system is provided by carbide steel slag slurry, while the remainder is provided by steel slag powder, to illustrate the implementation method under the condition of partial substitution of carbide steel slag slurry.

[0046] First, wet milling was performed. Steel slag and water were weighed and added to a wet stirred mill at a solid-liquid ratio of 1:5. The mill speed was set at 1200 rpm, and the wet milling time was controlled at 30 minutes. After wet milling, a uniformly dispersed wet-milled steel slag slurry was obtained. The slurry was grayish-black, and its overall state was stable, with no obvious large particle settling or local agglomeration. After wet milling, the steel slag was in a continuous slurry state, with the outer surface of the particles in full contact with the liquid phase, providing a uniform reaction interface for subsequent aeration carbonization.

[0047] Subsequently, in-situ wet carbonization was performed, and the resulting wet-milled steel slag slurry was directly transferred to a vertical sealed stirred tank. The stirred tank was equipped with a high-speed mechanical agitator, a porous disperser at the bottom serving as a gas inlet, and gas inlets on the side walls. The carbonization process was carried out under normal pressure. After starting the agitator, the agitation speed was adjusted to 2000 rpm, and carbon dioxide-containing gas was continuously introduced into the wet-milled steel slag slurry. The carbon dioxide concentration in the introduced gas was 50%, the gas flow rate was 10 L / min / 1 kg steel slag slurry, and the aeration time was 10 min. During the aeration process, the carbon dioxide-containing gas entered the slurry through the bottom disperser, forming a large number of fine bubbles under the agitation and rapidly dispersing throughout the slurry volume. The carbon dioxide continuously diffused into the liquid phase and reacted with the active calcium and magnesium components in the steel slag, simultaneously forming fine dispersed particles within the slurry. After the aeration was completed, the aeration was stopped, and low-speed stirring continued for 1 min to obtain the carbonized steel slag slurry.

[0048] The resulting carbonized steel slag slurry is directly fed into the subsequent mixing process while remaining in slurry form, without dewatering, drying, or re-grinding. This slurry retains the liquid phase environment formed during carbonization, the dispersion state of the steel slag particles, and the fine dispersed particles generated in situ, ensuring good dispersion conditions when it enters the mixing system.

[0049] Subsequently, a solid waste-based building material mixture was prepared. Based on the mass of the cementitious components, the steel slag solid phase provided by the carbide steel slag slurry accounted for 30% of the steel slag component, steel slag powder accounted for 10%, slag accounted for 47.5%, and gypsum accounted for 12.5%. In specific operation, slag, gypsum, steel slag powder, sand, and gravel were first weighed and added to a forced mixer for premixing. Then, the carbide steel slag slurry calculated according to the proportions was added, and an appropriate amount of process water was added according to the performance requirements of the mixture. The mixture was stirred for 3 minutes to obtain the solid waste-based building material mixture. In this embodiment, the steel slag portion was provided by both the carbide steel slag slurry and steel slag powder. The carbide steel slag slurry provided the partially carbide-treated steel slag component and its corresponding liquid phase environment, while the steel slag powder provided the remaining steel slag components. After stirring, the resulting mixture was uniform overall, with no obvious segregation or clumping, and exhibited good workability.

[0050] After the carbide steel slag slurry enters the subsequent mixing system containing slag, gypsum, sand, and gravel, the fine dispersed particles formed in the slurry are distributed throughout the system along with the steel slag powder, slag, and gypsum. The liquid environment carried by the slurry facilitates rapid wetting and dispersion of the components during the mixing stage, and the fine dispersed particles provide uniformly distributed interface positions in the system, making the structure formation more continuous during the subsequent hardening process.

[0051] Immediately after the solid waste-based building material mixture was prepared, it was molded. In this embodiment, the obtained mixture was poured into a 40mm×40mm×160mm prism mold and vibrated on a vibrating table for 30 seconds to ensure the mixture fully filled the mold and expelled any entrained air. After vibration, the surface of the specimen was smoothed, and it was allowed to stand until initial setting before demolding. The demolded specimens were then cured under standard curing conditions, with the curing temperature controlled at 20±2℃ and the relative humidity not lower than 95%. The curing ages were set at 3 days, 7 days, and 28 days to test the performance changes of the material at different ages.

[0052] The performance results of the system obtained in this embodiment are as follows: fluidity 210 mm, 3-day flexural strength 6.4 MPa, 7-day flexural strength 8.3 MPa, 28-day flexural strength 11.2 MPa, 3-day compressive strength 21.025 MPa, 7-day compressive strength 29.25 MPa, and 28-day compressive strength 36.07 MPa. Compared with the system without wet carbide steel slag slurry, the system obtained in this embodiment shows better performance in terms of fluidity and mechanical properties, indicating that even when the steel slag component is partially provided by carbide steel slag slurry, the system can still achieve good structure formation and later strength development.

[0053] This embodiment demonstrates that even when the steel slag component is provided only by a portion of the carbonized steel slag slurry, the technical route of wet milling, in-situ wet carbonization, and direct mixing of the slurry can still be effectively implemented, and the resulting solid waste-based building material mixture exhibits good workability and high mechanical properties. This embodiment further shows that carbonized steel slag slurry can be used as either a complete source of steel slag components or a partial source of steel slag components in the construction of solid waste-based building material systems, thereby improving the applicability of this invention under different proportioning conditions.

[0054] Comparative Example 1 Comparative Example 1 uses steel slag powder that has not undergone wet carbonization treatment as the source of steel slag, and the types and proportions of other raw materials are the same as those in Example 1.

[0055] The magnetically separated steel slag is crushed and screened to ensure a particle size of no more than 5 mm. The slag is then dried and ball-milled to obtain steel slag powder. This steel slag powder is not wet-milled or pulped before use.

[0056] In the preparation of solid waste-based building material mixtures, steel slag, blast furnace slag, and gypsum are used as cementing components in a mass ratio of 4:5:1, with the steel slag component entirely provided by steel slag powder. Blast furnace slag, gypsum, sand, gravel, and steel slag powder are premixed in a forced mixer, and then process water is added for further mixing to obtain the solid waste-based building material mixture.

[0057] The resulting mixture exhibited some particle agglomeration during stirring and had relatively low fluidity. The mixture was then poured into a 40mm×40mm×160mm prism mold, compacted for 30 seconds, leveled, and allowed to stand until initial setting before demolding. It was then cured under standard conditions: a curing temperature of 20±2℃, a relative humidity of not less than 95%, and curing periods of 3 days, 7 days, and 28 days.

[0058] The system was tested and found to have a flowability of 170 mm, a 3-day compressive strength of 18.095 MPa, a 7-day compressive strength of 21.80 MPa, and a 28-day compressive strength of 26.305 MPa.

[0059] Comparative Example 2 Comparative Example 2 used wet-milled steel slag pulp without carbonization as the steel slag source, and the other conditions were the same as in Example 1.

[0060] After crushing and screening, the steel slag is added to a wet stirred mill at a solid-liquid ratio of 1:5 for wet grinding at 1200 rpm for 30 minutes, resulting in a uniformly dispersed wet-ground steel slag slurry. This slurry is not subjected to carbonization in subsequent processes and is used directly in the subsequent mixing system.

[0061] In the preparation of the solid waste-based building material mixture, the mass ratio of steel slag, blast furnace slag, and gypsum, based on the mass of the cementitious components, is 4:5:1, with the steel slag portion entirely provided by uncarbonized wet-milled steel slag slurry. The aggregate dosage during mixing of each component remains consistent with that in Example 1, the equivalent water-cement ratio of the system is controlled at 0.5, and the mixing time is 3 minutes, resulting in the solid waste-based building material mixture.

[0062] The dispersion of the resulting mixture was improved compared to Comparative Example 1, but the performance improvement was limited during subsequent structure formation. The molding and curing conditions were the same as in Example 1.

[0063] The system was tested and found to have a flowability of 195 mm, a 3-day compressive strength of 18.44 MPa, a 7-day compressive strength of 22.35 MPa, and a 28-day compressive strength of 34.21 MPa.

[0064] Comparative Example 3 Comparative Example 3 used carbonized steel slag dry powder obtained by carbonization treatment followed by dehydration, drying and grinding as the source of steel slag, and the other conditions were the same as those in Example 1.

[0065] Steel slag was wet-milled and pulped and then subjected to in-situ wet carbonization treatment as described in Example 1 to obtain a solid carbonized steel slag slurry. The solid slurry was then dewatered and dried to constant weight at 105°C, and then ball-milled to obtain dry carbonized steel slag powder.

[0066] In the preparation of solid waste-based building materials mixtures, the mass ratio of steel slag, blast furnace slag, and gypsum, based on the mass of the cementitious components, is 4:5:1, with the steel slag portion entirely provided by dry powder of carbide steel slag. The blast furnace slag, gypsum, sand, gravel, and dry powder of carbide steel slag are premixed, then process water is added and stirred to achieve an equivalent water-cement ratio of 0.5. The stirring time is 3 minutes.

[0067] The resulting mixture showed improved dispersibility compared to the uncarbonized powder, but uneven particle distribution still existed. It was then molded and cured using the same method.

[0068] The system was tested and found to have a flowability of 182 mm, a 3-day compressive strength of 19.845 MPa, a 7-day compressive strength of 24.55 MPa, and a 28-day compressive strength of 30.24 MPa.

[0069] Comparative analysis To facilitate comparison of the impact of different treatment methods on the performance of solid waste-based building materials, the main performance data of Example 1, Example 2 and each comparative example are summarized in Table 2.

[0070] Table 2. Performance Comparison of Solid Waste-Based Building Material Systems under Different Treatment Methods

[0071] Table 2 shows that, under the same mix proportions and water-cement ratios, different steel slag treatment methods have a significant impact on the system performance. Regarding fluidity, Example 1, which uses carbonized steel slag directly as a slurry, exhibits the highest fluidity at 235 mm, significantly higher than the comparative systems. The uncarbonized steel slag powder system has the lowest fluidity, at only 170 mm. While the uncarbonized steel slag slurry system and the carbonized dry powder system show some improvement, they are still lower than the system using slurry directly. In terms of mechanical properties, Example 1 exhibits the highest compressive strength at all ages, with a 28-day compressive strength of 48.48 MPa, significantly higher than the 26.31 MPa of the uncarbonized powder system, the 34.21 MPa of the uncarbonized slurry system, and the 30.24 MPa of the carbonized dry powder system. Example 2, where the steel slag component is partially provided by carbonized slurry, also shows significantly better performance than the uncarbonized system, indicating that the carbonized steel slag slurry has a stable reinforcing effect in the system.

[0072] The comparative results show that when steel slag powder is used directly, the system's dispersibility and reactivity are both limited; when wet grinding is used without carbonization, although the dispersibility is improved, the active components are not effectively controlled; when carbonization is followed by dry powdering, the fine dispersed particles and liquid phase environment formed during carbonization are not retained, resulting in a weakening of their role in the subsequent mixing system.

[0073] Meanwhile, as shown in Table 1, the system that directly utilizes carbonized steel slag pulp has a lower expansion rate, indicating that after in-situ wet carbonization of steel slag, the active calcium and magnesium components that are prone to volume instability can be effectively transformed during pulping, thereby improving the volume stability of the system.

[0074] In summary, the results show that in-situ wet carbonization of steel slag after wet grinding to form a slurry, and direct participation of the slurry in the subsequent mixing system containing slag, gypsum, and aggregates, allows the fine dispersed particles, particle dispersion state, and liquid phase environment formed during carbonization to be retained as a whole and continuously participate in the subsequent reaction process. This achieves a synergistic effect of improved flowability, optimized structure formation, enhanced mechanical properties, and improved volume stability within the same system.

[0075] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0076] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for utilizing wet-milled steel slag through in-situ wet carbonization pulping, characterized in that, Includes the following steps: Step 1: The wet-milled steel slag slurry is subjected to in-situ wet carbonization treatment by introducing a gas containing carbon dioxide under stirring conditions, so that the active calcium and magnesium components in it undergo carbonization reaction to obtain carbonized steel slag slurry. Step 2: The carbide steel slag slurry is directly mixed with slag, gypsum, sand and gravel without dewatering, drying and re-grinding to obtain solid waste-based concrete mixture. Step 3: The solid waste-based concrete mixture is molded and cured to obtain solid waste-based building materials.

2. The method for utilizing wet-milled steel slag through in-situ wet carbonization and pulping according to claim 1, characterized in that, The wet-milled steel slag slurry in step one is obtained by mixing steel slag and water at a solid-liquid ratio of 1:1 to 1:10 and then wet-milling it.

3. The method for utilizing wet-milled steel slag through in-situ wet carbonization and pulping according to claim 2, characterized in that, The wet grinding process employs one or more of the following: ball mill, stirred mill, and sand mill.

4. The method for utilizing wet-milled steel slag through in-situ wet carbonization and pulping according to claim 1, characterized in that, The in-situ wet carbonization in step one is carried out under normal pressure.

5. The method for utilizing wet-milled steel slag in in-situ wet carbonization as described in claim 1, characterized in that, The concentration of carbon dioxide gas introduced in step one is 10% to 99%.

6. The method for utilizing wet-milled steel slag in in-situ wet carbonization as described in claim 5, characterized in that, The carbon dioxide gas flow rate is 5-20 L / min / 1 kg steel slag, the carbonization time is 5-20 min, and the stirring speed is 500-3000 rpm.

7. The method for utilizing wet-milled steel slag in in-situ wet carbonization as described in claim 1, characterized in that, The carbide steel slag slurry obtained in step one is mixed together with the liquid phase environment in the subsequent mixing process.

8. The method for utilizing wet-milled steel slag in in-situ wet carbonization as described in claim 1, characterized in that, In step two, the steel slag solid phase, slag and gypsum contained in the carbide steel slag slurry are used as cementing components, and the ratio of the three by mass is 4:5:

1.

9. The method for utilizing wet-milled steel slag in in-situ wet carbonization as described in claim 1, characterized in that, The dispersed carbonate particles formed in the carbide steel slag slurry participate in the subsequent mixing system's structural formation process and are beneficial to the formation and deposition of slag hydration reaction products.

10. A method for utilizing wet-milled steel slag through in-situ wet carbonization and pulping according to claim 1, characterized in that, The solid waste-based building materials products are mortar products, concrete block products, or other molded products.

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