Steel slag-clay composite material, preparation method and application

Abstract

The application provides a steel slag-clay composite material, a preparation method and application, and comprises the following steps: providing dried and crushed steel slag and clay respectively; mixing the steel slag with an alkaline activator, and carrying out closed wet heat pretreatment under the condition that the temperature is 50-80 DEG C and the relative humidity is 60-85%, to obtain activated steel slag powder; mixing the activated steel slag powder, the clay and water to obtain a slurry; and after the slurry is sequentially subjected to forming treatment and curing treatment, the steel slag-clay composite material is obtained. Moreover, the obtained steel slag-clay composite material is in a slurry state, is convenient for construction and forming, and is suitable for various engineering application scenarios such as grouting and pouring. In addition, the application consumes a large amount of steel slag and clay, realizes high-value utilization of the steel slag, reduces solid waste emission, does not need sintering in the preparation process, has low energy consumption, and conforms to the green low-carbon circular development concept. The obtained product has excellent performance and has significant market competitiveness.

Description

Technical Field

[0001] This invention relates to the fields of industrial solid waste resource utilization and building materials technology, and particularly to steel slag-clay composite materials, their preparation methods, and applications. Background Technology

[0002] With the rapid development of my country's steel industry, steel slag, as a major solid waste generated during the smelting process, has become a key bottleneck restricting the green development of the steel industry. The large-scale stockpiling of steel slag not only occupies valuable land resources, but the leaching of heavy metals from it also poses a serious threat to soil and water environments. Steel slag is rich in active minerals such as calcium silicate and calcium aluminate, providing the basic conditions for resource utilization. However, due to its low activity, slow hydration rate, and the presence of unstable components such as free calcium oxide and periclase, steel slag is prone to volume expansion and cracking, severely restricting its large-scale, high-value application in the building materials sector. The current national promotion of comprehensive utilization of solid waste and recycling of construction and transportation waste has created an urgent need for the efficient utilization of industrial solid wastes such as steel slag.

[0003] Existing steel slag activation technologies mainly include physical grinding, chemical activation, and thermal activation. While physical grinding can increase the specific surface area, it has limited impact on the glassy structure, resulting in insignificant activity enhancement. Chemical activation often uses strong alkaline activators, posing a risk of alkali-aggregate reaction and exhibiting strong corrosiveness. Furthermore, single sulfates are ineffective in activating the silicon phase in steel slag. In addition, although research on the preparation of building materials from steel slag and clay composites has been reported, these generally suffer from technical defects such as low composite strength and poor water stability due to insufficient steel slag activity and weak interfacial bonding. Therefore, this invention provides a steel slag-clay composite material, its preparation method, and its application. This results in a composite material that can deeply and efficiently activate steel slag and achieve a strong bond with clay, which is of great significance for promoting the resource utilization of solid waste. Summary of the Invention

[0004] The main objective of this invention is to provide a steel slag-clay composite material, its preparation method, and its application, in order to solve the technical problems of low strength and poor water stability of composite materials caused by insufficient activity of steel slag in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for preparing a steel slag-clay composite material, comprising the following steps: S1: Provides dried and crushed steel slag and clay respectively.

[0006] S2: The steel slag is mixed with an alkaline activator and subjected to closed wet heat pretreatment at a temperature of 50~80℃ and a relative humidity of 60~85% to obtain activated steel slag powder.

[0007] S3: The activated steel slag powder, the clay and water are mixed to obtain a slurry; the slurry is then subjected to molding and curing treatments to obtain the steel slag-clay composite material.

[0008] The mass ratio of the activated steel slag powder, the clay, and the water is (2~4):(2~5):(4~8).

[0009] According to an embodiment of this application, the alkaline activator comprises 10-50% desulfurized gypsum and 50-90% alkaline components by mass fraction.

[0010] According to embodiments of this application, the alkaline component includes one or more of water glass, sodium hydroxide, potassium hydroxide, sodium silicate, sodium carbonate, and quicklime.

[0011] The alkaline component includes a complex of sodium silicate and sodium carbonate, and the mass ratio of sodium silicate to sodium carbonate is (2:1) to (1:2).

[0012] According to embodiments of this application, the clay includes one or more of kaolin, bentonite, and illite clay.

[0013] According to an embodiment of this application, the total amount of alkaline activator added is 5-15% of the mass of the steel slag.

[0014] According to an embodiment of this application, after the pretreatment step, the pretreated product is further processed using a high-energy ball mill.

[0015] The ball mill operates at a speed of 300-500 rpm; the ball milling time is 0.5-2 hours; the ball-to-material ratio is (5:1)-(15:1); and the grinding media is zirconia balls.

[0016] According to an embodiment of this application, the molding process includes: injecting the slurry into a mold for molding.

[0017] The curing process includes: demolding after curing under the first condition, and then curing the demolded product under the second condition.

[0018] According to the embodiments of this application, the first condition curing includes: a first temperature of 20±2℃; a first humidity of ≥95%; and a first curing duration of 24~48h.

[0019] The second condition curing includes high-temperature steam curing.

[0020] The high-temperature steam curing includes: a second temperature of 60~90℃; a second humidity of ≥95%; and a second curing duration of 12~72h.

[0021] The present invention also provides a steel slag-clay composite material, which is prepared by the method described above.

[0022] The present invention also provides a steel slag-clay composite material prepared by the above preparation method or the application of the above steel slag-clay composite material in road base course and subgrade filler, wherein the 7-day unconfined compressive strength of the steel slag-clay composite material is 0.2~5 MPa.

[0023] The unconfined compressive strength after 28 days is 3~15 MPa.

[0024] Softening coefficient ≥ 0.85.

[0025] Compared with the prior art, the beneficial effects of the present invention are: The aforementioned method for preparing steel slag-clay composite materials involves mixing steel slag powder with an alkaline activator. Under humid and hot conditions, the alkaline activator accelerates the dissolution of aluminosilicate glass in the steel slag, releasing active SiO2 and Al2O3, significantly enhancing its gelling activity. Controlling the temperature to a medium-low humidity environment of 50-80℃ promotes the reaction while avoiding excessive energy consumption, thus improving activation efficiency and consistency. The method couples mechanical destruction and chemical activation in the same process using physical methods. The mechanical force not only refines the particles but also embeds the alkaline activator into the microcracks and new surfaces of the steel slag powder, achieving a synergistic "mechanical-chemical" activation that deeply activates the silicon and aluminum active centers in the steel slag, resulting in activated steel slag powder. This activates the latent gelling activity of the steel slag powder, improving its bonding properties and giving the composite material better mechanical strength and stability. The activated steel slag powder and clay form a composite structure with the participation of water, producing a synergistic physical-chemical effect that improves the density, compressive strength, and durability of the composite material. The highly active steel slag hydration products can effectively bind clay particles, solving the bottleneck problem of weak interfacial bonding in traditional materials. Moreover, the resulting steel slag-clay composite material is in a slurry state, which is convenient for construction and molding, and is suitable for various engineering applications such as grouting and casting.

[0026] Furthermore, this invention consumes a large amount of steel slag and clay, achieving high-value utilization of steel slag and reducing solid waste emissions. The preparation process does not require sintering, has low energy consumption, and conforms to the concept of green, low-carbon, and circular development. The resulting product has excellent performance and significant market competitiveness, and has important practical significance and broad application prospects for promoting the comprehensive utilization of smelting waste slag in steel enterprises and promoting carbon emission reduction in the building materials industry. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 This is a SEM image (magnified 3000 times) of the activated steel slag powder in Example 1 of the present invention; Figure 2 SEM image (3000x magnification) of the steel slag-clay composite material prepared in Example 1 of this invention; Figure 3 Polarized optical images of steel slag-clay composite materials prepared for different curing times; where (a) represents the first and second curing times totaling 0 days; and (b) represents the first and second curing times totaling 2 days. Figure 4 SEM images of silica composition in steel slag-clay composites prepared for different curing times; where (a) the first and second curing times totaled 0 days; and (b) the first and second curing times totaled 2 days.

[0029] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0031] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0032] To achieve the above objectives, the present invention provides a method for preparing a steel slag-clay composite material, comprising the following steps: S1: Provides dried and crushed steel slag and clay respectively.

[0033] In some embodiments, drying removes free moisture from the steel slag and clay, preventing material performance fluctuations due to uneven moisture content during subsequent mixing. This also improves powder flowability, facilitating uniform mixing. Crushing increases the specific surface area of ​​the steel slag and clay, resulting in finer particles that promote better contact and reaction with the alkaline activator, thus improving activation efficiency.

[0034] S2: The steel slag is mixed with an alkaline activator and subjected to closed wet heat pretreatment at a temperature of 50~80℃ and a relative humidity of 60~85% to obtain activated steel slag powder.

[0035] In some embodiments, the alkaline activator can accelerate the dissolution of aluminosilicate glass in steel slag under humid and hot conditions, releasing active SiO2 and Al2O3, and significantly enhancing its gelling activity. Maintaining a medium-low temperature humid and hot environment of 50-80°C promotes the reaction while avoiding excessive energy consumption; a humidity level of 60-85% ensures sufficient contact between the activator and the steel slag, preventing moisture loss through evaporation. Controlling the pretreatment steps also prevents the escape of harmful gases, while maintaining stable temperature and humidity within the system, improving activation efficiency and consistency.

[0036] In some embodiments, the alkaline component in the alkaline activator can disrupt the Si-O-Al network structure of the glassy phase in the steel slag, release active silica-alumina components, and generate cementitious products such as hydrated calcium silicate (CSH) or hydrated calcium aluminate (CAH) which grow crosswise between particles in the form of nanofibers or foil meshes, forming a dense three-dimensional spatial skeleton. This allows the originally loose steel slag-clay particles to be "welded" into a whole, significantly improving compressive and flexural strength.

[0037] In some embodiments, the alkaline activator can provide an alkaline environment, which can promote the solidification of heavy metal ions (such as Cr and Pb) in steel slag and reduce the risk of environmental pollution. The CSH layered structure can be achieved through isomorphic substitution (Al... 3+ →Si 4 + Electrostatic adsorption and physical encapsulation of Cr 6+ Pb 2+ Harmful ions are locked into the gel lattice, reducing the leaching concentration by 1 to 2 orders of magnitude, meeting the GB 5085.3 hazardous waste safety standard. Moreover, the gel can undergo long-term secondary hydration in an alkaline environment, re-precipitating CSH at the microcrack interface to suture the cracks, extending its service life and possessing the potential for "self-healing".

[0038] S3: The activated steel slag powder, the clay and water are mixed to obtain a slurry; the slurry is then subjected to molding and curing treatments to obtain the steel slag-clay composite material.

[0039] The mass ratio of the activated steel slag powder, the clay, and the water is (2~4):(2~5):(4~8).

[0040] In some embodiments, the active components in the activated steel slag powder react with the aluminosilicates in the clay to form a stable gel structure (such as CSH, NASH), thereby improving the material strength. The plasticity of the clay is neutralized by the rigid particles of the steel slag, reducing drying shrinkage cracks; at the same time, the water retention of the clay delays the loss of slurry moisture and promotes continuous hydration.

[0041] In some embodiments, the mass ratio of the activated steel slag powder, the clay, and the water is (2~3):(2~4):(4~6).

[0042] In some embodiments, by adjusting the mass ratio of activated steel slag powder, clay, and water to a suitable range, the prepared steel slag-clay composite material can be suitable for scenarios such as backfilling of mined-out areas, roadbed grouting, and self-sealing of abandoned mines. However, if the amount of water is too large, the slurry will be too thin, resulting in bleeding and low strength; if the amount of water is too small, the slurry will be too thick, losing its self-flowing function and generating more air bubbles.

[0043] The aforementioned method for preparing steel slag-clay composite materials involves mixing steel slag powder with an alkaline activator. Under humid and hot conditions, the alkaline activator accelerates the dissolution of aluminosilicate glass in the steel slag, releasing active SiO2 and Al2O3, significantly enhancing its gelling activity. Controlling the temperature to a medium-low temperature and humidity of 50-80℃ promotes the reaction while avoiding excessive energy consumption. A humidity level of 60-85% ensures sufficient contact between the activator and the steel slag, preventing moisture loss through evaporation. Controlling the pretreatment steps also prevents the escape of harmful gases and maintains stable temperature and humidity within the system, improving activation efficiency and consistency. The method couples mechanical destruction and chemical activation in the same process using physical methods. Mechanical force not only refines the particles but also embeds the alkaline activator into the microcracks and new surfaces of the steel slag powder, achieving a synergistic "mechanical-chemical" activation that deeply activates the silicon and aluminum active centers in the steel slag, resulting in activated steel slag powder. This activates the potential gelling activity of the steel slag powder, improves its bonding properties, and gives the composite material better mechanical strength and stability. Activated steel slag powder and clay form a composite structure with the aid of water, resulting in a synergistic physical-chemical effect that improves the density, compressive strength, and durability of the composite material. The highly active steel slag hydration products effectively bind clay particles, overcoming the bottleneck problem of weak interfacial bonding in traditional materials. Furthermore, the resulting steel slag-clay composite material is in a slurry state, facilitating construction and molding, and is suitable for various engineering applications such as grouting and casting. This process, through a "low-temperature activation-synergistic bonding" pathway, transforms waste steel slag into highly active cementing components, forming a composite material with complementary properties with clay, achieving a unified approach to high-value utilization of solid waste and low-carbon engineering applications.

[0044] Furthermore, this invention uses waste steel slag as one of the main raw materials, consuming a large amount of steel slag and clay, thus achieving high-value utilization of steel slag, reducing solid waste emissions, and eliminating the need for sintering in the preparation process, resulting in low energy consumption and aligning with the concept of green, low-carbon, and circular development. The resulting product exhibits excellent performance and significant market competitiveness.

[0045] In some embodiments, the alkaline activator comprises, by mass fraction, 10-50% desulfurized gypsum and 50-90% alkaline components.

[0046] In some embodiments, the main component of desulfurized gypsum is calcium sulfate dihydrate (CaSO4·2H2O), and the desulfurized gypsum is in powder form with a particle size of 20-60 μm. When desulfurized gypsum encounters alkaline components, it will first dissolve and then slowly release SO4. 2- It can consume some free OH groups. - This stabilizes the liquid phase pH within the range of 12-12.8, avoiding efflorescence and crusting problems caused by pH > 13. Furthermore, the SO4 provided by the desulfurization gypsum... 2- It can react with Al2O3 and Ca dissolved in steel slag 2+ The rapid formation of ettringite is illustrated by the following reaction equation: 6Ca 2+ +2Al(OH)4 - + 3SO4 2- + 4OH - + 26H2O → Ca6[Al(OH)6]2(SO4)3·26H2O Etnacite crystals are slender needle-like and can cross-link into a network within 6 to 24 hours, compensating for the low early strength of soda ash activation.

[0047] In addition, the addition of desulfurized gypsum can reduce the amount of alkaline components used and lower raw material costs.

[0048] In some embodiments, the alkaline activator comprises, by mass fraction, 20-40% desulfurized gypsum and 60-80% alkaline components.

[0049] In some embodiments, the alkaline activator comprises, by mass fraction, 25-35% desulfurized gypsum and 65-75% alkaline components.

[0050] In some embodiments, the alkaline activator comprises, by mass fraction, 28-32% desulfurized gypsum and 68-72% sodium silicate.

[0051] In some embodiments, the alkaline component includes one or more of water glass, sodium hydroxide, potassium hydroxide, sodium silicate, sodium carbonate, and quicklime.

[0052] The alkaline component includes a complex of sodium silicate and sodium carbonate, and the mass ratio of sodium silicate to sodium carbonate is (2:1) to (1:2).

[0053] In some embodiments, the alkaline component includes one of water glass, sodium hydroxide, potassium hydroxide, sodium silicate, sodium carbonate, and quicklime.

[0054] In some embodiments, the alkaline component includes water glass. Water glass is an aqueous solution of alkaline silicate, generally written as Na₂O·nSiO₂·mH₂O (sodium water glass) or K₂O·nSiO₂·mH₂O (potassium water glass), where n is a value of 2.0 to 3.0. Here, n is the molar ratio of SiO₂ to Na₂O; the larger the value of n, the higher the SiO₂ content, the greater the viscosity, and the lower the alkalinity. The alkaline component not only provides OH⁻... - It can instantly raise the pH to 12-13, rapidly eroding the glassy structure of steel slag; it can also react directly with calcium ions in steel slag to deposit low Ca / Si CSH gel.

[0055] In some embodiments, the clay includes one or more of kaolin, bentonite, illite clay, and river silt.

[0056] In some embodiments, the clay includes one of kaolin, bentonite, illite clay, and river silt.

[0057] In some embodiments, the clay includes kaolin and bentonite.

[0058] In some embodiments, the total amount of alkaline activator added is 5-15% of the mass of the steel slag.

[0059] In some embodiments, the total amount of alkaline activator added is 8-12% of the mass of the steel slag.

[0060] In some embodiments, after the pretreatment step, the pretreated product is further processed using a high-energy ball mill.

[0061] The ball mill operates at a speed of 300-500 rpm; the ball milling time is 0.5-2 hours; the ball-to-material ratio is (5:1)-(15:1); and the grinding media is zirconia balls.

[0062] In some embodiments, the ball mill rotates at a speed of 350-450 rpm; the ball milling time is 1-2 hours; the ball-to-material ratio is (5:1)-(10:1); and the grinding media is zirconia balls.

[0063] In some embodiments, the molding process includes injecting the slurry into a mold for molding.

[0064] The curing process includes: demolding after curing under the first condition, and then curing the demolded product under the second condition.

[0065] In some embodiments, the first conditional curing includes: a first temperature of 20±2℃; a first humidity of ≥95%; and a first curing duration of 24~48h.

[0066] The second condition curing includes high-temperature steam curing.

[0067] The high-temperature steam curing includes: a second temperature of 60~90℃; a second humidity of ≥95%; and a second curing duration of 12~72h.

[0068] In some embodiments, the slurry is injected into a mold for molding, the mold size being 40mm×40mm×160mm. After compaction, the mold is subjected to first-condition curing.

[0069] In some embodiments, the first condition curing at room temperature allows for sufficient hydration of the slurry surface, generating a sufficient CSH gel structure that allows for immediate demolding, thereby shortening the cycle and increasing the mold cycle rate.

[0070] In some implementations, the second curing condition is high-temperature steam curing. This method effectively enhances the ion exchange capacity of the CSH gel, allowing its layered structure to undergo ion exchange and lattice solid solution interaction, thereby releasing Cr... 6+ Pb 2+ Heavy metal ions are more firmly solidified inside the crystal lattice, which greatly improves the long-term stability and environmental safety of the steel slag-clay composite material.

[0071] The present invention also provides a steel slag-clay composite material, which is prepared by the method described above.

[0072] The present invention also provides a steel slag-clay composite material prepared by the above preparation method or the application of the above steel slag-clay composite material in road base course and subgrade filler, wherein the 7-day unconfined compressive strength of the steel slag-clay composite material is 0.2~5 MPa.

[0073] The unconfined compressive strength after 28 days is 3~15 MPa.

[0074] Softening coefficient ≥ 0.85.

[0075] In some embodiments, the 7-day unconfined compressive strength of the steel slag-clay composite material is 3~5 MPa; the 28-day unconfined compressive strength is 10~15 MPa; and the softening coefficient is 0.85~1.0.

[0076] In some embodiments, the 7-day unconfined compressive strength of the steel slag-clay composite material is 4~5 MPa; the 28-day unconfined compressive strength is 13~15 MPa; and the softening coefficient is 0.85~0.95.

[0077] In some embodiments, the steel slag-clay composite material exhibits superior early and late strength. Specifically, the 7-day unconfined compressive strength ensures that the steel slag-clay composite material can quickly develop load-bearing capacity after construction, shortening the construction period; the 28-day unconfined compressive strength significantly enhances the load-bearing capacity and structural stability of the road base layer, effectively resisting traffic loads and deformation.

[0078] In some embodiments, the steel slag-clay composite material exhibits a high softening coefficient, indicating minimal strength loss under saturated conditions. It retains most of its strength even under erosion from aquatic environments (such as rainwater and groundwater), demonstrating strong resistance to water damage and thus ensuring the long-term durability and service life of the road structure in humid and rainy areas.

[0079] To further illustrate the present invention, the following examples are provided: Example 1 A method for preparing a steel slag-clay composite material, comprising the following steps: S1: Provides dried and crushed converter slag and clay respectively; the clay is selected from kaolin.

[0080] S2: Mix 1000g of steel slag with 100g of alkaline activator, and perform a closed-loop wet heat pretreatment at 70℃ and 85% relative humidity. Then, place the mixture in a ball mill and ball mill it at 400 rpm for 1 hour using zirconia balls as the grinding medium (ball-to-material ratio 10:1) to obtain activated steel slag powder. See [link to relevant documentation]. Figure 1 It can be seen that the alkaline activator is embedded in the microcracks and new surface of the steel slag powder, forming a dense structure. The activated steel slag powder exhibits irregular granular and blocky aggregates with uneven particle size and a relatively rough surface. The alkaline activator consists of 30% desulfurized gypsum and 70% sodium silicate.

[0081] S3: Mix 400g of activated steel slag powder with 400g of clay and 800g of water for 30 minutes to obtain a slurry, which is the steel slag-clay composite material. (See also...) Figure 2It can be seen that the steel slag-clay composite material prepared by this invention has a dense filling and a compact structure, with only a small number of pores and gaps. A large number of needle-like and fibrous crystalline substances appear in the steel slag-clay composite material, which are interwoven and distributed between the particles, filling the pores. This indicates that a chemical reaction has occurred, making the microstructure of the steel slag-clay composite material more compact and its interwoven structure stronger. The slurry was then injected into a 40mm×40mm×160mm mold and compacted. After curing in an environment with a first temperature of 20℃ and a first humidity of 95% for 24 hours, the mold was removed and transferred to a steam curing chamber with a second temperature of 80℃ and a second humidity of 95% for 24 hours. The mold was then removed, cooled, and tested.

[0082] The steel slag-clay composite material prepared in Example 1 was tested and found to have a 7-day unconfined compressive strength of 4.8 MPa, a 28-day unconfined compressive strength of 14.6 MPa, and a softening coefficient of 0.90.

[0083] Example 2 Compared to Example 1, the mass ratio of activated steel slag powder to clay was changed.

[0084] The mass ratio of activated steel slag powder to clay was 2:1. Other steps were the same as in Example 1, and a steel slag-clay composite material was obtained.

[0085] The steel slag-clay composite material prepared in Example 2 was tested and found to have a 7-day unconfined compressive strength of 3.9 MPa, a 28-day unconfined compressive strength of 13.5 MPa, and a softening coefficient of 0.87.

[0086] Example 3 Compared to Example 1, the composition of the alkaline activator was changed.

[0087] The alkaline activator consisted of a composite of 30% desulfurized gypsum and 70% sodium silicate and sodium carbonate, with a mass ratio of sodium silicate to sodium carbonate of 1:2. Other steps were the same as in Example 1, resulting in a steel slag-clay composite material.

[0088] The steel slag-clay composite material prepared in Example 3 was tested and found to have a 7-day unconfined compressive strength of 3.9 MPa, a 28-day unconfined compressive strength of 14.2 MPa, and a softening coefficient of 0.85.

[0089] Comparative Example 1 Compared to Example 1, the alkaline activator was changed.

[0090] The alkaline activator was only desulfurized gypsum. The other steps were the same as in Example 1, and a steel slag-clay composite material was obtained.

[0091] The steel slag-clay composite material prepared in Comparative Example 1 was tested and found to have an unconfined compressive strength of 0.11 MPa after 7 days, an unconfined compressive strength of 2.1 MPa after 28 days, and a softening coefficient of 0.82.

[0092] Comparative Example 2 Compared to Example 1, the activation step in the ball mill was omitted.

[0093] The other steps are the same as in Example 1, and the steel slag-clay composite material is obtained.

[0094] The steel slag-clay composite material prepared in Comparative Example 2 was tested and found to have a 7-day unconfined compressive strength of 0.16 MPa, a 28-day unconfined compressive strength of 2.8 MPa, and a softening coefficient of 0.73.

[0095] analyze: See Figure 3 Polarized optical images of steel slag-clay composite materials obtained for different curing times; among them, Figure 3 (a) The total duration of the first and second maintenance periods is 0 days; Figure 3 (b) The first and second maintenance periods total 2 days; from Figure 3 As can be seen in (a), when the curing time was 0 days, the steel slag particles were wrapped in fine soil; when the curing time was 2 days, a distinct light gray halo appeared around the steel slag particles, indicating that the steel slag and clay underwent a hydration reaction and generated hydration products. Figure 4 SEM images of silica composition in steel slag-clay composites prepared for different curing times; among them, Figure 4 (a) The total duration of the first and second maintenance periods is 0 days; Figure 4 (b) The curing time for the first and second curing cycles totals 2 days. As shown in the figure, during the 0-day curing period, the distribution of SiO2 (bright areas) is relatively dispersed with localized concentrations. After 2 days of curing, the distribution of SiO2 becomes more uniform, and the previously locally concentrated areas show SiO2 migration or dispersion. This indicates that during the curing process, SiO2 participated in the reaction within the steel slag-clay system, causing SiO2 to diffuse from the previously concentrated areas to the surrounding matrix, reflecting the hydration process of the steel slag-clay. Furthermore, the matrix after 2 days of curing (dark areas) shows a higher degree of SiO2 filling, indirectly reflecting the generation of more cementitious products during the curing process, resulting in a denser microstructure.

[0096] The aforementioned method for preparing steel slag-clay composite materials involves coupling mechanical stress and chemical activation simultaneously during the mixing of steel slag powder and an alkaline activator. The mechanical force not only refines the particles but also allows the alkaline activator to embed into the microcracks and new surfaces of the steel slag powder, achieving a synergistic "mechanical-chemical" activation. This deeply activates the silicon and aluminum active centers in the steel slag, resulting in activated steel slag powder. This activates the latent cementitious activity of the steel slag powder, improving its bonding properties and giving the composite material better mechanical strength and stability. The activated steel slag powder and clay form a composite structure with the participation of water, producing a synergistic physical-chemical effect that improves the density, compressive strength, and durability of the composite material. The highly active steel slag hydration products effectively bind clay particles, solving the bottleneck problem of weak interfacial bonding in traditional materials. Moreover, the resulting steel slag-clay composite material is in a slurry state, facilitating construction and molding, and is suitable for various engineering applications such as grouting and casting. This process transforms waste steel slag into highly active cementing components through a "low-temperature activation-synergistic bonding" pathway, and forms a composite material with complementary properties with clay, thereby achieving the unification of high-value utilization of solid waste and low-carbon engineering applications.

[0097] Furthermore, this invention uses waste steel slag as one of the main raw materials, consuming a large amount of steel slag and clay, thus achieving high-value utilization of steel slag, reducing solid waste emissions, and eliminating the need for sintering in the preparation process, resulting in low energy consumption and aligning with the concept of green, low-carbon, and circular development. The resulting product exhibits excellent performance and significant market competitiveness.

[0098] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a steel slag-clay composite material, characterized in that, Includes the following steps: S1: Provides dried and crushed steel slag and clay respectively; S2: The steel slag is mixed with an alkaline activator and subjected to closed wet heat pretreatment at a temperature of 50~80℃ and a relative humidity of 60~85% to obtain activated steel slag powder. S3: The activated steel slag powder, the clay and water are mixed to obtain a slurry; the slurry is then subjected to molding treatment and curing treatment in sequence to obtain the steel slag-clay composite material; The mass ratio of the activated steel slag powder, the clay, and the water is (2~4):(2~5):(4~8).

2. The method of claim 1, wherein the steel slag-clay composite material is prepared by mixing the steel slag and the clay in a weight ratio of 1:1 to 1:

3. The alkaline activator comprises 10-50% desulfurized gypsum and 50-90% alkaline components by mass fraction.

3. The method of claim 2, wherein the steel slag-clay composite material is prepared by mixing the steel slag and the clay in a weight ratio of 1:1 to 1:

3. The alkaline component includes one or more of water glass, sodium hydroxide, potassium hydroxide, sodium silicate, sodium carbonate, and quicklime. The alkaline component includes a complex of sodium silicate and sodium carbonate, and the mass ratio of sodium silicate to sodium carbonate is (2:1) to (1:2).

4. The method for preparing the steel slag-clay composite material according to claim 1, characterized in that, The clay includes one or more of kaolin, bentonite, and illite clay.

5. The method for preparing the steel slag-clay composite material according to claim 1, characterized in that, The total amount of alkaline activator added is 5-15% of the mass of the steel slag.

6. The method for preparing the steel slag-clay composite material according to claim 1, characterized in that, Following the pretreatment step, the product is further processed using a high-energy ball mill; The ball mill operates at a speed of 300-500 rpm; the ball milling time is 0.5-2 hours; the ball-to-material ratio is (5:1)-(15:1); and the grinding media is zirconia balls.

7. The method for preparing the steel slag-clay composite material according to claim 1, characterized in that, The molding process includes: injecting the slurry into a mold for molding; The curing process includes: demolding after curing under the first condition, and then curing the demolded product under the second condition.

8. The method for preparing the steel slag-clay composite material according to claim 7, characterized in that, The first curing conditions include: a first temperature of 20±2℃; a first humidity of ≥95%; and a first curing duration of 24~48h. The second condition curing includes high-temperature steam curing; The high-temperature steam curing includes: a second temperature of 60~90℃; a second humidity of ≥95%; and a second curing duration of 12~72h.

9. A steel slag-clay composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the steel slag-clay composite material as described in claim 9, characterized in that, Application of the steel slag-clay composite material in road base and subgrade filler; The 7-day unconfined compressive strength of the steel slag-clay composite material is 0.2~5 MPa; The unconfined compressive strength after 28 days is 3~15 MPa; Softening coefficient ≥ 0.85.

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