A lightweight high-strength carbonized steel slag-based artificial aggregate and a two-step granulation preparation method thereof

Abstract

The application discloses a method for preparing light high-strength carbonized steel slag artificial aggregate by adopting a two-step granulation method, and comprises the following steps: (1) adding water into steel slag powder and stirring to obtain pre-wetted steel slag powder; (2) adding the pre-wetted steel slag powder into a closed rolling granulation device, introducing CO2 gas, and then rolling carbonization granulation is carried out in a closed state to obtain light porous inner cores; (3) carrying out first carbonization curing to obtain carbonized porous inner cores; (4) soaking the carbonized porous inner cores in water and achieving a saturated surface dry state, then adding pre-wetted steel slag powder to carry out rolling granulation to obtain double-layer structure particles; and (5) carrying out second carbonization curing, and thus the light high-strength carbonized steel slag-based artificial aggregate is obtained. The application takes steel slag powder as a main raw material, combines step-by-step granulation and precise carbonization and other processes, and constructs a double-layer aggregate structure with a porous core and a dense shell, on the basis of efficient carbon sequestration, can effectively take into account light weight and high strength and other performances, and is suitable for wide application.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and building materials technology, specifically relating to a lightweight, high-strength carbonized steel slag-based artificial aggregate and its two-step granulation preparation method. Background Technology

[0002] Steel slag, a major solid waste from the steel industry, is emitted in enormous quantities annually. Long-term stockpiling not only occupies vast amounts of land resources but also causes environmental pollution due to heavy metal leaching and dust emissions. Processing steel slag into artificial aggregates is one important way to realize its resource utilization.

[0003] Currently, carbonation is the mainstream technology for preparing steel slag-based artificial aggregates. It involves the reaction of CO2 with active components in steel slag (such as CaO and MgO) to generate carbonate binders, which can improve the strength and stability of the aggregate. However, existing carbonized steel slag-based artificial aggregate preparation technologies all employ a one-step granulation process. This process still has a core defect that is difficult to overcome: during the one-step granulation process, the surface of the steel slag particles preferentially reacts with CO2, rapidly forming a dense carbonate outer layer. While this dense outer layer can improve the surface strength of the aggregate to some extent, it directly hinders the subsequent penetration of CO2 into the aggregate core. This results in the active components of the steel slag in the core area not being able to fully react with CO2, leading to extremely low carbonization of the aggregate core (usually less than 30%), significantly reducing the CO2 sequestration rate and failing to fully realize the environmental value of carbonation technology. More importantly, the insufficiently carbonized core cannot form a stable cemented structure, making it difficult to meet the modern construction demand for lightweight, high-strength aggregates.

[0004] Therefore, further developing a preparation process that can overcome the obstacles of the dense outer layer, ensure the full carbonization of the core, and flexibly adjust and balance the lightweight and high-strength properties has become the key to solving the current technical bottleneck. Summary of the Invention

[0005] The main objective of this invention is to address the shortcomings of existing carbonized steel slag artificial aggregate preparation technologies, such as difficulty in achieving both lightweight and high-strength properties and insufficient core carbonization. This invention provides a lightweight, high-strength carbonized steel slag artificial aggregate and its two-step granulation preparation method. Through step-by-step granulation and precise carbonization control, a double-layer aggregate structure with a "porous core-dense shell" is constructed. This effectively balances lightweight and high-strength properties while maintaining efficient carbon fixation, and allows for flexible adjustment of structural parameters to meet diverse engineering needs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing lightweight, high-strength carbide steel slag artificial aggregate using a two-step granulation process includes the following steps: (1) Add water to the steel slag powder and stir until the steel slag powder is completely wetted and there is no obvious dry material clumping, to obtain pre-wetted steel slag powder; (2) Pour the pre-wetted steel slag powder into a closed rolling granulation device, introduce CO2 gas, and then keep it in a closed state to carry out rolling carbonization granulation to obtain a lightweight porous core. (3) The obtained lightweight porous core is placed in a carbonization curing box for the first carbonization curing. During the curing process, the gas is kept circulating to obtain the carbonized porous core. (4) Immerse the obtained carbonized porous core in water until the core components absorb water and reach a saturated surface-dry state; Then, pre-wetted steel slag powder is added to the obtained saturated surface-dry carbonized porous core and rolled granulation is carried out. By utilizing the adsorption of the porous core and the rolling friction, the pre-wetted steel slag powder is evenly coated on the surface of the carbonized porous core, forming a double-layer structure particle with the carbonized porous core as the core and the dense steel slag layer as the outer shell. (5) The obtained double-layer structure particles are placed in a carbonization curing box for a second carbonization curing, so that the outer shell steel slag is completely carbonized and hardened, and lightweight high-strength carbonized steel slag-based artificial aggregate is obtained.

[0007] Following the above scheme, the maximum particle size of the steel slag powder mentioned in step (1) is no greater than 75 μm.

[0008] Furthermore, in the steel slag powder, the CaO content is greater than 35%; the tetracalcium aluminoferrite content is less than 5%; the dicalcium ferrite content is less than 5%; and the RO phase content is less than 10%.

[0009] Following the above scheme, in step (1), the mass ratio of water to steel slag powder is 0.20-0.35.

[0010] Following the above scheme, in step (2), the concentration of CO2 gas introduced is 20-50 vol% (the rest is mainly nitrogen, or a small amount of other gases that will not participate in the reaction), the gas flow rate is controlled at 0.5-1.5 L / min, and the gas is introduced until the internal pressure of the granulator rises to 0.2-1.0 MPa, and then sealed for rolling carbonization granulation; the rotation speed of the rolling granulation device is controlled at 10-20 r / min, the tilt angle is 30°-60°, and the granulation time is 20-40 min.

[0011] Following the above scheme, in step (3), the concentration of CO2 gas in the curing chamber used in the first carbonization curing step is 20-30 vol%, the circulating wind speed is 0.3-0.5 m / s, the curing temperature is 20-25℃, the pressure is normal, the relative humidity is 60-70%, and the curing time is 5-7h.

[0012] Furthermore, the resulting lightweight porous core has a particle size of 0.5-2 cm and a rich porous structure with a pore size of 10-50 μm (interconnected multi-level pore structure), which can provide a low-resistance fast transport channel for the gas / liquid phase reaction medium, which is conducive to the full progress of the internal carbonization reaction.

[0013] Following the above scheme, the soaking time in step (4) is 5-10 minutes.

[0014] Following the above scheme, in step (4), the moisture content of the pre-wetted steel slag powder is 9-17 wt%.

[0015] Following the above scheme, in step (4), the mass ratio of saturated surface-dry carbonized porous core to pre-wetted steel slag powder is 1:1-2.5.

[0016] According to the above scheme, in step (4), the rotation speed of the rolling granulation is controlled at 15-25 r / min, the tilt angle is 30°-60°, and the granulation time is 15-25 min.

[0017] Following the above scheme, in step (5), the conditions for the second carbonization curing include: CO2 gas concentration of 20-30 vol% (the rest is mainly nitrogen, or a small amount of other gases that will not participate in the reaction), circulating wind speed of 0.5-1.0 m / s, curing temperature of 30-40℃, normal pressure, relative humidity of 70-80%, and curing time of 6-8 h.

[0018] Furthermore, by adjusting the amount of pre-wetted steel slag powder in steps (2) and (4), the volume of the porous core and the thickness of the dense shell of the artificial aggregate can be flexibly controlled, which can promote the precise balance between the lightweight and high-strength properties of the artificial aggregate.

[0019] Preferably, the mass ratio of water to steel slag powder is 0.25-0.30, the concentration of CO2 gas is 25-35 vol%, the circulating air velocity is 0.35-0.45 m / s, the curing temperature is 20-23℃, the relative humidity is 63-68%, and the curing time is 5-6.5 h; the rolling granulation speed is 15-20 r / min, and the granulation time is 20-35 min.

[0020] The lightweight, high-strength carbide steel slag-based artificial aggregate prepared according to the above scheme has a lightweight, porous steel slag core and a dense steel slag shell, with a bulk density of 900-1100 kg / m³. 3 The cylinder compressive strength is 5.2-6.5 MPa, the carbonization degree is over 90%, the CO2 absorption rate is over 70%, and the water absorption rate is less than 10%, especially below 8%.

[0021] Furthermore, in the lightweight high-strength carbonized steel slag-based artificial aggregate, the thickness of the dense steel slag outer shell accounts for 50-100% of the diameter of the lightweight porous steel slag inner core.

[0022] The principles of this invention include: (1) Cemented framework and interconnected pore construction mechanism: CO2 gas and pre-wetted steel slag powder undergo rolling carbonization and granulation in a closed (0.2-1.0 MPa) rolling device. The active CaO and MgO in the steel slag rapidly hydrate upon contact with free water to generate Ca(OH)2 and Mg(OH)2. The high concentration of CO2 reacts rapidly with hydroxides, initially generating amorphous calcium carbonate precursors with cohesive activity and trace amounts of hydrated calcium silicate gel. These precursors have good adhesion properties and can agglomerate the steel slag powder under rolling friction. As the reaction continues, the amorphous precursors gradually transform into crystalline CaCO3 (aragonite phase), and the rigid calcium carbonate crystals interlock to form a stable porous framework, effectively maintaining the overall structure of the core. Furthermore, the carbonization reaction of the active components in steel slag is a strongly exothermic reaction. The instantaneous temperature rise of the system causes the free water between particles to vaporize rapidly and generate trace amounts of water vapor. The water vapor formed under high pressure and closed rolling conditions cannot dissipate quickly, which in turn promotes the formation of tiny bubbles inside the aggregated particles, opening up the micro gaps between particles in situ. At the same time, combined with the shearing and collision effects continuously applied during the rolling granulation process, the pore channels formed by water vapor are further expanded and connected, promoting the formation of a lightweight porous core.

[0023] (2) Formation principle of dense outer shell: The surface of the saturated surface-dry carbonized porous core has a certain adsorption capacity. The pre-wetted steel slag powder with low moisture content can be tightly wrapped around the surface of the porous core under rolling action, and form a dense outer layer structure under continuous rolling friction. Then, CO2 carbonization curing is carried out. The steel slag components embedded or wrapped around the surface of the lightweight porous core react fully with CO2 to generate a dense carbonate cementing layer, which further significantly improves the density and overall mechanical properties of the obtained aggregate. In addition, during the transition from the inner layer to the outer layer, the pore size of the interface area gradually decreases, and the density increases, which is conducive to improving the mechanical properties of the aggregate and ensuring good overall performance.

[0024] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention uses steel slag powder as raw material to prepare lightweight high-strength aggregate, which can realize the high-value utilization of steel slag solid waste, significantly reduce the cost of raw materials, and the carbonization process can absorb a large amount of CO2, which has significant economic and environmental benefits.

[0025] (2) Both granulation steps use a rolling granulation device, which is simple and controllable to operate; carbonization curing can ensure a full and uniform reaction through concentration and airflow control, resulting in a high yield and is suitable for industrial mass production.

[0026] (3) The prepared steel slag-based artificial aggregate has a double-layer structure based on a porous core and a dense shell. The core has a high degree of carbonization and the shell has a high hardness, which can achieve an effective balance between low bulk density and high compressive strength.

[0027] (5) By adjusting the amount of steel slag used in the two-step granulation, the core volume ratio and shell thickness can be flexibly adjusted, which can help meet the different requirements of different projects for aggregate density and strength. Attached Figure Description

[0028] Figure 1 The image shows a cross-sectional view (backscattered electron microscope image) of the lightweight, high-strength carbonized steel slag-based artificial aggregate obtained in Example 1 of the present invention, wherein (a) is the porous core region (black pores in the attached figure), (b) is the main display and interface region, and (c) is the dense shell region. Detailed Implementation

[0029] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention. Modifications made by those skilled in the art without departing from the essence and concept of the present invention fall within the scope of protection of the present invention. Coal slag and granite powder are dried according to the description in the embodiments.

[0030] In the following examples, the steel slag powder used was provided by a steel company in Hubei Province, and the content of CaO was 43.5 wt%, the content of tetracalcium aluminoferrite was 4 wt%, the content of dicalcium ferrite was 3 wt%, and the content of RO phase was 8 wt%.

[0031] In the following embodiments, the carbonization curing box model used is TYC-HTX.

[0032] Example 1 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.20 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 20 vol% (the rest was nitrogen, the same below), the gas flow rate was controlled at 0.5 L / min, the rotation speed of the rolling granulation device was controlled at 10 r / min, the tilt angle was 40°, and the gas pressure of the rolling granulation device was 0.5 MPa. The rolling granulation was carried out under the corresponding conditions for 20 min to obtain a lightweight porous core. The average particle size of the obtained lightweight porous core was 1.0 cm and the average pore size was 25 μm. (3) The obtained porous cores are placed in a carbonization curing box for the first carbonization curing, wherein the concentration of CO2 gas is 20%, the circulating wind speed is 0.3 m / s, the curing temperature is 20℃, the pressure is normal, the relative humidity is 60%, and the curing time is 5 h to obtain carbonized porous cores. (4) Soak the obtained carbonized porous core in water for 5 min until saturated and dry. Then put the obtained porous core and pre-wetted steel slag powder (moisture content 9%) into a rolling granulation device for granulation (air atmosphere). The speed of the rolling granulation device is controlled at 15 r / min, the tilt angle is 40°, and the granulation time is 15 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are placed in a carbonization curing box for a second carbonization curing, wherein the concentration of CO2 gas is 20 vol%, the circulating wind speed is 0.5 m / s, the curing temperature is 30℃, the pressure is normal, the relative humidity is 70%, and the curing time is 6 h, to obtain the lightweight high-strength carbonized steel slag-based artificial aggregate.

[0033] Example 2 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.25 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 30 vol%, the gas flow rate was controlled at 0.8 L / min, the rotation speed of the rolling granulation device was controlled at 15 r / min, the tilt angle was 50°, and the gas pressure of the rolling granulation device was 1.0 MPa. The corresponding conditions were maintained in a closed environment for rolling granulation for 25 min to obtain a lightweight porous core. The average particle size of the obtained lightweight porous core was 1.5 cm and the average pore size was 30 μm. (3) The obtained porous cores are placed in a carbonization curing box for carbonization curing, wherein the concentration of CO2 gas is 25%, the circulating wind speed is 0.4 m / s, the curing temperature is 25℃, the pressure is normal, the relative humidity is 65%, and the curing time is 6 h to obtain carbonized porous cores. (4) Soak the carbonized porous core in water for 10 min until it is saturated and dry. Then put the obtained porous core and pre-wetted steel slag powder (moisture content 12%) into a rolling granulation device for granulation (air atmosphere). The speed of the rolling granulation device is controlled at 20 r / min, the tilt angle is 50°, and the granulation time is 20 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are placed in a carbonization curing box for a second carbonization curing, wherein the concentration of CO2 gas is 25 vol %, the circulating wind speed is 0.6 m / s, the curing temperature is 35℃, the pressure is normal, the relative humidity is 75%, and the curing time is 7 h, to obtain lightweight high-strength carbonized steel slag-based artificial aggregate.

[0034] Example 3 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.30 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 40 vol %, the gas flow rate was controlled at 1.2 L / min, the rotation speed of the rolling granulation device was controlled at 15 r / min, the tilt angle was 30°, and the gas pressure of the rolling granulation device was 1.0 MPa. The corresponding conditions were maintained for rolling granulation for 30 min to obtain a lightweight porous core. The average particle size of the obtained lightweight porous core was 2.0 cm and the average pore size was 10 μm. (3) The obtained porous cores are subjected to the first carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 0.5m / s, the curing temperature is 20℃, the pressure is normal, the relative humidity is 70%, and the curing time is 7h to obtain carbonized porous cores. (4) Soak the carbonized porous core in water for 10 min until saturated and surface dry. Then, put the obtained porous core and pre-wetted steel slag powder (moisture content 15%) into a rolling granulator for granulation. The rotation speed of the rolling granulator is controlled at 25 r / min, the tilt angle is 30°, and the granulation time is 25 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are subjected to a second carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 0.8 m / s, the curing temperature is 38℃, the pressure is normal, the relative humidity is 80%, and the curing time is 8 h, to obtain lightweight high-strength carbonized steel slag-based artificial aggregate.

[0035] Example 4 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.35 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 50 vol%, the gas flow rate was controlled at 1.5 L / min, the rotation speed of the rolling granulation device was controlled at 20 r / min, the tilt angle was 60°, and the gas pressure of the rolling granulation device was 0.2 MPa. The corresponding conditions were maintained for rolling granulation for 40 min to obtain a lightweight porous core. The average particle size of the obtained lightweight porous core was 0.5 cm and the average pore size was 50 μm. (3) The obtained porous cores are subjected to the first carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 0.5m / s, the curing temperature is 25℃, the pressure is normal, the relative humidity is 65%, and the curing time is 6h to obtain carbonized porous cores. (4) Soak the carbonized porous core in water for 8 minutes until it is saturated and dry. Then put the obtained porous core and pre-wetted steel slag powder (moisture content 17%) into a rolling granulation device for granulation (air atmosphere). The speed of the rolling granulation device is controlled at 20 r / min, the tilt angle is 60°, and the granulation time is 20 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are subjected to a second carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 1.0 m / s, the curing temperature is 40℃, the pressure is normal, the relative humidity is 75%, and the curing time is 7 h, to obtain lightweight high-strength carbonized steel slag-based artificial aggregate.

[0036] Example 5 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.30 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 35 vol%, the gas flow rate was controlled at 1.0 L / min, the rotation speed of the rolling granulation device was controlled at 15 r / min, the tilt angle was 40°, and the gas pressure of the rolling granulation device was 0.8 MPa. The corresponding conditions were maintained for rolling granulation for 40 min to obtain a lightweight porous core. The average particle size of the obtained lightweight porous core was 1.3 cm and the average pore size was 20 μm. (3) The obtained porous cores are subjected to the first carbonization curing, wherein the concentration of CO2 gas is 25%, the circulating wind speed is 0.4 m / s, the curing temperature is 20℃, the pressure is normal, the relative humidity is 60%, and the curing time is 5 h, to obtain carbonized porous cores. (4) Soak the carbonized porous core in water for 5 min until it is saturated and dry. Then put the obtained porous core and pre-wetted steel slag powder (moisture content 15%) into a rolling granulation device for granulation (air atmosphere). The speed of the rolling granulation device is controlled at 20 r / min, the tilt angle is 40° and the granulation time is 20 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are subjected to a second carbonization curing, wherein the concentration of CO2 gas is 20%, the circulating wind speed is 1.0 m / s, the curing temperature is 35℃, the pressure is normal, the relative humidity is 80%, and the curing time is 8 h, to obtain lightweight high-strength carbonized steel slag-based artificial aggregate.

[0037] Example 6 A lightweight, high-strength carbide steel slag-based artificial aggregate, the preparation method of which includes the following steps: (1) Take steel slag powder and add water at a liquid-to-solid ratio of 0.25 (mass ratio) to obtain pre-wetted steel slag powder; (2) The pre-wetted steel slag powder was poured into a closed rolling granulation device for aeration granulation. The CO2 gas concentration was 35 vol%, the gas flow rate was controlled at 1.0 L / min, the rotation speed of the rolling granulation device was controlled at 15 r / min, the tilt angle was 35°, and the gas pressure of the rolling granulation device was 0.5 MPa. The corresponding conditions were maintained for rolling granulation for 30 min to obtain a lightweight porous core. The average particle size of the obtained porous core was 0.8 cm and the average pore size was 40 μm. (3) The obtained porous cores are subjected to the first carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 0.3m / s, the curing temperature is 25℃, the pressure is normal, the relative humidity is 70%, and the curing time is 6.5 h to obtain carbonized porous cores. (4) Soak the carbonized porous core in water for 10 min until it is saturated and dry. Then, put the obtained porous core and pre-wetted steel slag powder (moisture content 12%) into a rolling granulation device for granulation (air atmosphere). The speed of the rolling granulation device is controlled at 15 r / min, the tilt angle is 35°, and the granulation time is 20 min to obtain double-layer structure particles. (5) The obtained double-layer structure particles are subjected to a second carbonization curing, wherein the concentration of CO2 gas is 30%, the circulating wind speed is 0.5 m / s, the curing temperature is 35℃, the pressure is normal, the relative humidity is 70%, and the curing time is 6 h, to obtain lightweight high-strength carbonized steel slag-based artificial aggregate.

[0038] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that CO2 gas was not introduced during the preparation of the lightweight porous core.

[0039] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the concentration of CO2 gas introduced during the preparation of the lightweight porous core is 10% (in addition, the effect is worse when nitrogen is replaced).

[0040] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the lightweight porous core was not carbonized.

[0041] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the steel slag powder added during the preparation of the double-layer structure particles was not pre-wetted.

[0042] Comparative Example 5 Compared with Example 1, Comparative Example 5 differs in that the moisture content of the pre-wetted steel slag powder added during the preparation of the bilayer structure particles is 33.3%.

[0043] Comparative Example 6 Compared with Example 1, Comparative Example 6 differs only in the preparation process of the lightweight porous core and the conditions before sealing. Specifically, the carbon dioxide gas concentration is 20 vol%, the gas flow rate is controlled at 2.0 L / min (the gas pressure of the rolling granulation device is 0.5 MPa), the rotation speed of the rolling granulation device is 30 r / min, the tilt angle is 30°, and the granulation time is 50 min.

[0044] The artificial aggregates prepared in each embodiment and comparative example were subjected to performance tests. The specific test methods are as follows, and the specific performance results are shown in Table 1.

[0045] TG analysis (TGA) was performed using a Rigaku ThermoPlus EV 02 TGA instrument to calculate the content of carbonization products (calcium hydroxide, CC, and bound water), degree of carbonization, and CO2 uptake. Approximately 20 mg of each sample was heated from room temperature to 1000°C at a flow rate of 10°C / min at an N2 flow rate of 30 mL / min.

[0046] The contents of bound water, CH and CC can be calculated using formula (1-3).

[0047] (1) (2) (3) In the formula, , , These represent the mass loss of the sample at 105-300°C, 400-480°C, and 480-900°C, respectively. This indicates the residual mass of the sample at 900°C.

[0048] Calculate the actual CO2 absorption of the sample using formula (4-6). And the degree of carbonization, DoC. This is obtained by calculating the mass loss at 480-900°C and dividing it by the residual mass at 900°C (Equation 4). The theoretical maximum CO2 absorption... It is calculated based on chemical composition (Equation 5). The degree of carbonization, DoC, is calculated... and The ratio is determined (Equation 6).

[0049] (4) (5) (6) In the formula The mass loss of the sample at 480°C-900°C is mainly caused by the release of CO2 from the decomposition of CC. The residual mass at 900°C. , and These represent the actual CO2 uptake, the theoretical maximum CO2 uptake, and the degree of carbonization, DoC, respectively. CO2uptake.max = 36.99% Table 1 Performance test results of steel slag-based artificial aggregates in each embodiment and comparative example

[0050] Figure 1 The images show microscopic images of the porous core (a), dense shell (c), and interface region (b) of the lightweight, high-strength carbide steel slag-based artificial aggregate obtained in Example 1. As can be seen from the images, the porous core contains numerous macropores (10-50 μm in diameter) exceeding 10 μm; and abundant calcium carbonate (CC) forms between the steel slag particles, constituting a cementing framework that maintains the structural stability of the porous core. Unlike the porous core, the dense shell lacks obvious macropores (1-5 μm in diameter), but contains relatively abundant micropores between the steel slag particles, and a very distinct interface region (transition region) exists between the porous core and the dense shell. The interface region has finer particles and smaller pores than the core region. Based on this structure, an effective balance between lightweight and high strength can be achieved.

[0051] The test results show that the bulk density of the steel slag-based artificial aggregates prepared using the methods in Examples 1-6 of this invention is 1100 kg / m³. 3 The compressive strength of all samples is greater than 5 MPa, indicating that the prepared artificial aggregate possesses both lightweight and high strength properties. Furthermore, the carbonization degree of all examples is greater than 90%, and the CO2 absorption rate can reach up to 86%, indicating that this preparation method can significantly improve the CO2 absorption rate of the artificial aggregate.

[0052] The above embodiments describe the basic principles, main features, and advantages of the present invention. The present invention is not limited to the above embodiments; the embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its principles, and all such changes are protected by patent law within the scope of the claims.

Claims

1. A method for preparing lightweight, high-strength carburized steel slag artificial aggregate using a two-step granulation process, characterized in that, Includes the following steps: (1) Add water to steel slag powder and stir to obtain pre-wetted steel slag powder; (2) Add the pre-wetted steel slag powder into a closed rolling granulation device, introduce CO2 gas, and then keep it in a closed state to carry out rolling carbonization granulation to obtain a lightweight porous core. (3) The obtained lightweight porous core is subjected to a first carbonization curing to obtain a carbonized porous core; (4) Immerse the carbonized porous core in water until the core components absorb water and reach a saturated surface-dry state; Then, pre-wetted steel slag powder is added to the obtained saturated surface-dry carbonized porous core, and rolling granulation is performed to obtain double-layer structure particles. (5) The obtained double-layer structure particles are subjected to a second carbonization curing to obtain the lightweight high-strength carbonized steel slag-based artificial aggregate.

2. The method according to claim 1, characterized in that, The maximum particle size of the steel slag powder mentioned in step (1) is no greater than 75 μm; the CaO content is greater than 35%, the tetracalcium aluminoferrite content is less than 5%, the dicalcium ferrite content is less than 5%, and the RO phase content is less than 10%.

3. The method according to claim 1, characterized in that, In step (1), the mass ratio of water to steel slag powder is 0.20-0.

35.

4. The method according to claim 1, characterized in that, In step (2), the concentration of CO2 gas introduced is 20-50 vol%, the gas flow rate is controlled at 0.5-1.5 L / min, and the gas is vented until the internal pressure of the sealed granulator rises to 0.2-1.0 MPa, and then sealed for rolling carbonization granulation; the rotation speed of the rolling granulation device is set to 10-20 r / min, the tilt angle is 30°-60°, and the granulation time is 20-40 min.

5. The method according to claim 1, characterized in that, In step (3), the concentration of CO2 gas used in the first carbonization curing step is 20-30 vol%, the circulating wind speed is 0.3-0.5 m / s, the curing temperature is 20-25℃, the pressure is normal, the relative humidity is 60-70%, and the curing time is 5-7 h.

6. The method according to claim 1, characterized in that, The moisture content of the pre-wetted steel slag powder is 9-17%.

7. The method according to claim 1, characterized in that, In step (4), the mass ratio of saturated surface-dried carbonized porous core to pre-wetted steel slag powder is 1:1-2.

5.

8. The method according to claim 1, characterized in that, In step (4), the rotation speed of the rolling granulation is controlled at 15-25 r / min, the tilt angle is 30°-60°, and the granulation time is 15-25 min.

9. The method according to claim 1, characterized in that, In step (5), the conditions for the second carbonization curing include: CO2 gas concentration of 20-30 vol%, circulating wind speed of 0.5-1.0 m / s, curing temperature of 30-40℃, normal pressure, relative humidity of 70-80%, and curing time of 6-8 h.

10. The lightweight, high-strength carburized steel slag-based artificial aggregate prepared by the method according to any one of claims 1 to 9, characterized in that, It has a lightweight, porous steel slag core and a dense steel slag shell.

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