Steel slag-based cementing material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solid waste recycling, in particular to a steel slag-based cementing material as well as a preparation method and application thereof. The steel slag-based cementing material is prepared from the following raw materials: modified steel slag, mineral slag, gypsum, Portland cement and auxiliary materials, wherein the modified steel slag is obtained by mixing acid radical salt and steel slag and reacting. The steel slag is modified to reduce the content of free calcium and free magnesium in the steel slag and improve the activity of the steel slag, so that the obtained steel slag based cementing material has good mechanical properties, durability and stability, and the utilization rate of the steel slag is improved.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, specifically to a steel slag-based cementitious material, its preparation method, and its application. Background Technology

[0002] With the steady increase in metallurgical industry capacity, the harmless treatment and resource utilization of steel slag, a highly alkaline industrial solid waste, has become a focus of industry attention. Currently, my country's cumulative steel slag stockpile exceeds 1 billion tons, with an annual emission of approximately 100 million tons. However, the comprehensive utilization rate is only around 30%. This large-scale stockpiling not only occupies land resources and incurs maintenance costs but also risks soil and water pollution due to heavy metal leakage. Meanwhile, the traditional cement-based material production process has high carbon emissions, which does not align with the "dual-carbon" development goals. While the application of industrial solid wastes such as steel slag in cementitious materials can achieve a 30%-50% carbon emission reduction, it has long faced the bottleneck of balancing high solid waste content with high performance.

[0003] In existing technologies, physical and chemical methods such as flotation, acid leaching, grinding, and aging are used to improve the properties of steel slag in order to increase its utilization rate. However, the chemical composition of steel slag from different sources varies significantly. The reduction of the content of free calcium oxide and free magnesium oxide in steel slag through the above methods is limited, which will affect the hydration activity and stability of steel slag. Moreover, the low activity leads to limited use. Summary of the Invention

[0004] In view of this, the present invention provides a steel slag-based cementitious material, its preparation method and application. By modifying the steel slag, the content of free calcium and free magnesium in the steel slag is reduced and the activity of the steel slag is improved, so that the obtained steel slag-based cementitious material has good mechanical properties, durability and stability, and improves the utilization rate of steel slag.

[0005] In a first aspect, the present invention provides a steel slag-based cementitious material, wherein the raw materials of the steel slag-based cementitious material include modified steel slag, slag, gypsum, silicate cement and auxiliary materials, wherein the modified steel slag is obtained by mixing and reacting anions with steel slag.

[0006] As described above, the steel slag-based cementitious material includes at least one of phosphates, silicates, sulfates, and formates. And / or, the excipients include at least one of nano-silica, steel fiber, basalt fiber, and polypropylene fiber; And / or, the slag includes at least one of blast furnace slag and granulated blast furnace slag; And / or, the gypsum includes at least one of phosphogypsum, natural gypsum, and desulfurized gypsum.

[0007] As described above, the mass ratio of the acid salt to the steel slag in the steel slag-based cementitious material is (1-4):100.

[0008] As described above, in the steel slag-based cementitious material, the ratio of the total mass of slag and gypsum to the mass of the anion salt is (5-37):(0.8-1). And / or, the mass ratio of the auxiliary material to the modified steel slag is (0.2-0.5):100.

[0009] As described above, in the steel slag-based cementitious material, the mass ratio of silicate to formate is 1:(0.5-1). And / or, the ratio of the formate to the total mass of silicate cement and auxiliary materials is (4-20):(102-145).

[0010] Secondly, the present invention provides a method for preparing the steel slag-based cementitious material as described above, comprising the following steps: Modified steel slag, slag and gypsum are mixed evenly, crushed and then added with auxiliary materials and silicate cement, and stirred to obtain steel slag-based cementitious material.

[0011] As described above, the pulverization process includes mixing modified steel slag, blast furnace slag and gypsum, pulverizing to 20-100 mesh, and then treating with carbon dioxide to obtain the pulverized intermediate material.

[0012] As described above, the carbon dioxide treatment includes treating for 30-120 minutes under conditions of a pressure of 0.5-1.2 MPa and a temperature of 60-100°C.

[0013] As described above, the stirring process includes stirring at 60-120 rpm for 5-10 minutes, then adding water and standard sand, and stirring for 20-40 minutes to obtain a steel slag-based cementitious material.

[0014] Thirdly, the present invention provides an application of the steel slag-based cementitious material as described above, which is applied to at least one of roadbed paving and building materials.

[0015] The present invention, employing the above-described solution, has at least the following beneficial effects: In this application, by modifying steel slag with acid salts, the content of free calcium and free magnesium in the steel slag can be reduced, and the stability and cementitious activity of the steel slag can be improved. Furthermore, by combining it with slag and gypsum, the content of free calcium and free magnesium in the steel slag can be further reduced, so that the steel slag-based cementitious material has good durability, stability and strength. Finally, by adding auxiliary materials and silicate cement, the mechanical properties, stability and durability of the material can be further improved, so that the steel slag-based cementitious material can have a wider range of applications. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0017] To improve the utilization rate of steel slag in cementitious materials and to reuse solid waste, the inventors studied the formulation of cementitious materials and the modification of steel slag. They found that one of the factors affecting the use of steel slag in existing technologies is the presence of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO). The free calcium oxide content is generally between 6-12%, and a high content of free calcium leads to a strong hydration reaction, causing volume expansion and resulting in surface bulging, cracking, and other defects within a short period, affecting the durability of the material. Meanwhile, the free magnesium oxide content is generally between 3-8%, and free magnesium oxide undergoes a slow hydration reaction over a longer period, resulting in delayed expansion and damage. This can lead to sudden cracking of the material after a long time, posing a long-term risk and reducing the strength and durability of the material, thus affecting the utilization rate of steel slag.

[0018] In existing technologies, physical and chemical methods such as flotation, acid leaching, grinding, and aging are used to improve the properties of steel slag in order to increase its utilization rate. However, the chemical composition of steel slag from different sources varies significantly. The above methods have limited effect on reducing the content of free calcium oxide and free magnesium oxide in steel slag. The hydration activity and stability of steel slag are poor, and the activity of cementing materials is low, which limits its use.

[0019] The inventors first chemically modified the steel slag to reduce the content of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) in the steel slag, and then optimized the formula of the cementitious material to reduce f-CaO and f-MgO while improving the mechanical properties, durability and stability of the cementitious material.

[0020] In view of this, firstly, embodiments of this application propose a steel slag-based cementitious material, the raw materials of which include modified steel slag, slag, gypsum, silicate cement, and auxiliary materials. The modified steel slag is obtained by mixing and reacting anion salts with steel slag.

[0021] Modified steel slag is obtained by mixing and reacting acid salts with steel slag. This process can reduce the content of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) in steel slag. Furthermore, by combining it with slag, gypsum, silicate cement and auxiliary materials, the activity, mechanical properties, durability and stability of steel slag-based cementitious materials can be improved.

[0022] In one embodiment of the present invention, the acid salt includes at least one selected from phosphates, silicates, sulfates, and formates. By using acid salts, the acid radicals can react with free calcium oxide and magnesium oxide in the steel slag to produce stable compounds such as calcium phosphate, calcium silicate, and magnesium silicate, thereby reducing the content of free calcium oxide and magnesium oxide in the steel slag, improving the stability of the steel slag, preventing later expansion and cracking, and improving the cementing activity and durability of the steel slag.

[0023] In one embodiment of the present invention, the auxiliary material includes at least one selected from nano-silica, steel fiber, basalt fiber, and polypropylene fiber. Exemplarily, the auxiliary material can be any one of nano-silica, steel fiber, basalt fiber, and polypropylene fiber, or it can be nano-silica and steel fiber, nano-silica and basalt fiber, or nano-silica and polypropylene fiber; it can also be nano-silica, steel fiber, basalt fiber, or nano-silica, basalt fiber, and polypropylene fiber; those skilled in the art can select according to the actual situation. By adding the auxiliary material, the toughness, durability, and crack resistance of the cementitious material can be improved.

[0024] In one specific embodiment, the excipients are nano-silica and basalt fiber. By adding nano-silica and basalt fiber to the cementitious material, the microstructure of the cementitious material can be optimized and the cementitious material can have a network structure, which can synergistically improve the mechanical properties, durability and environmental adaptability of the material.

[0025] In one specific embodiment, the mass ratio of nano-silica to basalt fiber is (1-3):2; exemplaryly, the mass ratio can be 1:2; 1:1; 3:2, or any range between the above. By controlling the parameters of the above two components, the properties of the material can be adjusted according to different situations.

[0026] In one embodiment of the present invention, the slag includes at least one of blast furnace slag and granulated blast furnace slag; preferably, the slag is granulated blast furnace slag.

[0027] In one embodiment of the present invention, the gypsum includes at least one of phosphogypsum, natural gypsum, and desulfurized gypsum; preferably, the gypsum is desulfurized gypsum. By combining granulated blast furnace slag and desulfurized gypsum, not only can the activity and strength of the cementitious material be improved, but the harmful effects of free calcium oxide and free magnesium oxide can also be further suppressed.

[0028] In one embodiment of the present invention, the mass ratio of the anhydride to the steel slag is (1-4):100; exemplaryly, the mass ratio can be 1:100; 2:100; 3:100; 4:100, or any ratio within the range of two of the above. By controlling the amount of anhydride added, it can fully react with the free calcium oxide and magnesium oxide in the steel slag, and can play a certain synergistic role, effectively improving the stability and durability of the steel slag.

[0029] In one embodiment of the present invention, the ratio of the total mass of slag and gypsum to the mass of the anhydride is (5-37):(0.8-1); exemplaryly, the mass ratio can be 5:0.8; 5:1; 15:0.8; 15:1; 23:0.9; 27:0.8; 29:1; 35:0.8; 37:1, or any ratio range between the above two. By controlling the addition ratio of the anhydride to slag and gypsum, a synergistic effect can be achieved, further improving the stability and durability of the material.

[0030] In one specific implementation, the mass ratio of slag to gypsum is (20-50):(5:10); for example, the mass ratio can be 20:5; 20:10; 35:5; 35:10; 50:5; 50:10, or any ratio range between the above two. By controlling the mass ratio of slag to gypsum, better synergistic effects can be achieved.

[0031] In one embodiment of the present invention, the mass ratio of the auxiliary material to the modified steel slag is (0.2-0.5):100. Exemplarily, the mass ratio can be 0.2:100; 0.4:100; 0.5:100, or any ratio range between the two. By controlling the amount of auxiliary material added, the durability and strength of the cementitious material can be improved.

[0032] In one embodiment of the present invention, the mass ratio of silicate to formate is 1:(0.5-1); exemplaryly, the mass ratio can be 1:0.5; 1:0.6; 1:0.7; 1:0.8; 1:1, or any ratio range between the above two. By using silicate and formate as modifiers and controlling their amounts, a synergistic effect can be achieved to a certain extent, which is beneficial to improving the mechanical properties, stability, and durability of steel slag.

[0033] In one specific embodiment, the silicate includes at least one of sodium silicate, potassium silicate, and water glass. Those skilled in the art can select a suitable silicate according to the actual situation.

[0034] In one specific embodiment, the formate includes at least one of sodium formate, potassium formate, and calcium formate. Those skilled in the art can select a suitable formate according to the actual situation.

[0035] In one embodiment of the present invention, the mass ratio of formate to the total mass of silicate cement and auxiliary materials is (4-20):(102-145); exemplaryly, the mass ratio can be 4:102; 4:121; 4:145; 10:113; 10:126; 10:137; 20:102; 20:145, or any range between the above two. By controlling the mass ratio of formate to the total mass of silicate cement and auxiliary materials, the structure and stability of the cementitious material can be improved, which is beneficial to further improving durability.

[0036] Secondly, the present invention provides a method for preparing the steel slag-based cementitious material as described above, comprising the following steps: Modified steel slag, blast furnace slag, and gypsum are mixed evenly, pulverized, and then additives and silicate cement are added and stirred to obtain a steel slag-based cementitious material. The above preparation method is simple and easy to produce.

[0037] In one embodiment of the present invention, the pulverization process includes mixing modified steel slag, slag, and gypsum, pulverizing the mixture to 20-100 mesh, and then subjecting it to carbon dioxide treatment to obtain the pulverized intermediate material. By pulverizing the modified steel slag, slag, and gypsum and then subjecting them to carbon dioxide treatment, the free calcium and free magnesium in the steel slag can be further reduced, which is beneficial to improving the stability of the material.

[0038] In one specific embodiment, the mesh size of the pulverized material can be 20 mesh, 30 mesh, 50 mesh, 80 mesh, 100 mesh, or any value between two of these. Those skilled in the art can also adjust the mesh size of the pulverized material according to the actual situation.

[0039] In one embodiment of the present invention, the carbon dioxide treatment includes treatment for 30-120 minutes at a pressure of 0.5-1.2 MPa and a temperature of 60-100°C. By subjecting the steel slag to carbon dioxide treatment at a certain pressure and temperature, the stability, durability, and volume stability of the material can be further improved.

[0040] In one specific embodiment, the pressure can be 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, or any value between two of these. Those skilled in the art can also select a suitable pressure based on actual conditions. The temperature can be 60°C, 80°C, 100°C, or any value between two of these. Those skilled in the art can also select a suitable temperature based on actual conditions. The processing time can be 30 min, 60 min, 90 min, 120 min, or any value between two of these. Those skilled in the art can also select a suitable time based on actual conditions.

[0041] In one specific implementation, the carbon dioxide introduction rate is 0.5-1.8 m. 3 / h, for example, the infeed rate can be 0.5m 3 / h, 1.0m 3 / h, 1.8m 3 / h, or any value between the two above; those skilled in the art may also adjust it according to the actual situation.

[0042] In one embodiment of the present invention, the stirring process includes stirring at 60-120 rpm for 5-10 minutes, then adding water and standard sand, and stirring for 20-40 minutes to obtain a steel slag-based cementitious material. Stirring the dry materials first, and then stirring the mixture, facilitates a more uniform mixing.

[0043] In one specific embodiment, the stirring speed can be 60 rpm, 80 rpm, 120 rpm, or any combination thereof. The first stirring time can be 5 min, 8 min, 10 min, or any combination thereof; the second stirring time can be 20 min, 30 min, 40 min, or any combination thereof. Those skilled in the art can also adjust the stirring speed and stirring time according to actual conditions.

[0044] Thirdly, this invention provides an application of a steel slag-based cementitious material, which is used in at least one of roadbed paving and building materials. By using the steel slag-based cementitious material in roadbed paving or building materials, the service life can be improved. Furthermore, the steel slag-based cementitious material of this application can be used in suitable fields according to actual conditions.

[0045] The modification of steel slag and the preparation of steel slag-based cementitious materials are described in detail below: Preparation Example 1 Preparation of modified steel slag The steel slag was dried in a dryer until constant weight; 2.0 g of calcium formate was dissolved in 196 mL of water, and then 2.0 g of sodium silicate was added and stirred to dissolve, resulting in a 200 mL modified solution with a concentration of 2 wt%.

[0046] 100g of dried steel slag was added to 200mL of a 2wt% modified solution, stirred for 3h, filtered and separated, and dried at 60℃ to obtain modified steel slag.

[0047] Preparation Example 2 Preparation of modified steel slag The steel slag was dried in a dryer to constant weight; 0.9g of calcium formate was dissolved in 197.3mL of water, and then 1.8g of sodium silicate was added and stirred evenly to obtain a 200mL modified solution with a total concentration of 1.35wt%.

[0048] 100g of dried steel slag was added to 200mL of a 1.35wt% modified solution, stirred for 2h, filtered and separated, and dried at 60℃ to obtain modified steel slag.

[0049] Preparation Example 3 Preparation of modified steel slag The steel slag was dried in a dryer to constant weight; 0.8g of calcium formate was dissolved in 197.7mL of water, and then 1.5g of sodium silicate was added and stirred to dissolve, resulting in a 200mL modified solution with a concentration of 1.15wt%.

[0050] 100g of dried steel slag was added to 200mL of a 1.15wt% modified solution, stirred for 1.5h, filtered and separated, and dried at 60℃ to obtain modified steel slag.

[0051] Preparation Example 4 Preparation of modified steel slag The steel slag was dried in a dryer to constant weight; 0.4g of calcium formate was dissolved in 199mL of water, and then 0.6g of sodium silicate was added and stirred to dissolve, resulting in a 200mL modified solution with a concentration of 0.5wt%.

[0052] 100g of dried steel slag was added to 200mL of a 0.5wt% modified solution, stirred for 1.5h, filtered and separated, and dried at 60℃ to obtain modified steel slag.

[0053] Example 1 Preparation of steel slag-based cementitious materials 100g of modified steel slag from Example 1, 20g of granulated blast furnace slag, and 5g of desulfurized gypsum were mixed and pulverized to 20 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 0.5MPa, and heated from room temperature to 60°C. Carbon dioxide was introduced at a rate of 0.5m³ / min. 3 The process is carried out at 60 rpm for 120 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.3 g of nano silica, 0.2 g of basalt short fibers and 10 g of silicate cement are added. The mixture is stirred at 60 rpm for 5 minutes, then 55 g of water and 380 g of standard sand are added, and the mixture is stirred for another 20 minutes to obtain steel slag-based cementitious material.

[0054] Example 2 100g of modified steel slag from Example 1, 40g of granulated blast furnace slag, and 8g of desulfurized gypsum were mixed and pulverized to 20 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 0.5MPa, and heated from room temperature to 75°C. Carbon dioxide was introduced at a rate of 0.9m³ / min. 3 The process is carried out at 60 rpm for 120 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.3 g of nano silica, 0.2 g of basalt short fibers and 10 g of silicate cement are added. The mixture is stirred at 60 rpm for 5 minutes, then 80 g of water and 430 g of standard sand are added, and the mixture is stirred for another 30 minutes to obtain steel slag-based cementitious material.

[0055] Example 3 100g of modified steel slag from Example 1, 50g of granulated blast furnace slag, and 10g of desulfurized gypsum were mixed and pulverized to 20 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 0.5MPa, and heated from room temperature to 75°C. Carbon dioxide was introduced at a rate of 0.9m³ / min. 3 The process is carried out at 60 rpm for 120 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.3 g of nano silica, 0.2 g of basalt short fibers and 10 g of silicate cement are added. The mixture is stirred at 60 rpm for 5 minutes, then 80 g of water and 430 g of standard sand are added, and the mixture is stirred for another 30 minutes to obtain steel slag-based cementitious material.

[0056] Example 4 100g of the modified steel slag from Example 2, 35g of granulated blast furnace slag, and 8g of desulfurized gypsum were mixed and pulverized to 60 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 0.8MPa, and heated from room temperature to 100°C. Carbon dioxide was introduced at a rate of 1.8m³ / min. 3 The mixture was processed at 80 rpm for 80 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.2 g of nano silica, 0.2 g of basalt short fibers, and 10 g of silicate cement were added. The mixture was stirred at 80 rpm for 8 minutes, then 70 g of water and 400 g of standard sand were added, and the mixture was stirred for another 30 minutes to obtain steel slag-based cementitious material.

[0057] Example 5 100g of the modified steel slag from Example 3, 30g of granulated blast furnace slag, and 10g of desulfurized gypsum were mixed and pulverized to 100 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 1.2MPa, heated from room temperature to 100°C, and carbon dioxide was introduced at a rate of 1.8m³ / min. 3The mixture was processed at 120 rpm for 60 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.1 g of nano-silica, 0.2 g of basalt short fibers, and 10 g of silicate cement were added. The mixture was stirred at 120 rpm for 10 minutes. Then, 70 g of water and 400 g of standard sand were added, and the mixture was stirred for another 40 minutes to obtain steel slag-based cementitious material.

[0058] Example 6 100g of the modified steel slag from Example 4, 32g of granulated blast furnace slag, and 5g of desulfurized gypsum were mixed and pulverized to 100 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 1.2MPa, and heated from room temperature to 100°C. Carbon dioxide was introduced at a rate of 1.5m³ / min. 3 Process for 30 minutes at / h, cool to room temperature, remove and place in a mixing tank, add 0.2g nano silica, 0.2g basalt short fiber and 10g silicate cement, stir at 120rpm for 5 minutes, then add 73g water and 400g standard sand, continue stirring for 25 minutes to obtain steel slag-based cementitious material.

[0059] Example 7 100g of the modified steel slag from Example 4, 32g of granulated blast furnace slag, and 5g of desulfurized gypsum were mixed and pulverized to 100 mesh. The pulverized material was then placed in a reaction vessel, pressurized to 1.0 MPa, and heated from room temperature to 100°C. Carbon dioxide was introduced at a rate of 1.5 m³ / min. 3 The mixture was processed at 100 rpm for 40 minutes, cooled to room temperature, and then transferred to a mixing tank. 0.1 g of nano-silica, 0.1 g of basalt short fibers, and 14 g of silicate cement were added. The mixture was stirred at 100 rpm for 5 minutes, then 73 g of water and 400 g of standard sand were added. The mixture was stirred for another 20 minutes to obtain steel slag-based cementitious material.

[0060] Comparative Example 1 In this comparative example, ordinary steel slag was used instead of modified steel slag, and the other steps were the same as in Example 1.

[0061] Comparative Example 2 In this comparative example, silicates were used to modify the steel slag instead of formates, and the other steps were the same as in Example 1.

[0062] Comparative Example 3 In this comparative example, formate was used to modify the steel slag instead of silicate, and the other steps were the same as in Example 1.

[0063] Comparative Example 4 In this comparative example, no auxiliary materials were added during the preparation of the steel slag-based cementitious material, and the other steps were the same as in Example 1.

[0064] Comparative Example 5 In this comparative example, after the modified steel slag, granulated blast furnace slag, and desulfurized gypsum were crushed, no carbon dioxide treatment was performed, and the other steps were the same as in Example 1.

[0065] Test case The modified steel slags prepared in Examples 1-4 were tested for free calcium oxide and free magnesium oxide content. The steel slag-based cementitious materials prepared in Examples 1-8 and the steel slag-based cementitious materials prepared in Comparative Examples 1-5 were also tested. The following items were tested: free calcium oxide and free magnesium oxide content, autoclaving stability, activity index, compressive strength and unconfined compressive strength.

[0066] The content of free calcium oxide and free magnesium oxide was determined according to national standards GB / T 24492 and GB / T 5066; the stability was determined according to GB / T 750 and JTG E42 T0347; the activity index was determined according to national standard GB / T 20491; the compressive strength was determined according to national standard GB / T 17671-2021; and the unconfined compressive strength was determined according to JTG E51-2009 T 0805.

[0067] The test results are shown in Tables 1 and 2: Table 1 Table 2 According to the data in Table 1, modifying steel slag with silicates and formates can effectively reduce the content of f-CaO and f-MgO in steel slag. Different proportions of silicates and formates have different effects on reducing the content of f-CaO and f-MgO in steel slag, but they can play a synergistic role to a certain extent.

[0068] According to the data in Table 2, in Examples 1-7, by using modified steel slag, granulated blast furnace slag, desulfurized gypsum, and carbon dioxide treatment, the f-CaO and f-MgO contents in the materials can be further reduced. The f-CaO content can be as low as 0.99%, and the f-MgO content can be as low as 0.61%, indicating that the use of granulated blast furnace slag, desulfurized gypsum, and carbon dioxide treatment can further play a synergistic role. Furthermore, in Examples 1-7, the stability of the prepared steel slag-based cementitious materials all met the requirements, and the water immersion expansion rate was all <1%, with the lowest reaching 0.61%, indicating that the steel slag-based cementitious materials in this application have good volume stability and can be used for a long time.

[0069] In Examples 1-7, the mortar strength activity index of the prepared steel slag-based cementitious materials showed high cementitious activity at both 7d and 28d, reaching a maximum of 73% at 7d and 92% at 28d. This indicates that the treatment of steel slag in this application has a significant effect and can be used in different scenarios.

[0070] In Examples 1-7, the compressive strength of the prepared steel slag-based cementitious materials reached at least 9.1 MPa at 3 days, at least 30.9 MPa at 7 days, and at least 42.1 MPa at 28 days, indicating that the material of this application has strong compressive strength. The unconfined compressive strength reached 4.2 MPa or more at 7 days and 11.7 MPa or more at 28 days, indicating that the material of this application also has strong unconfined compressive strength. In summary, the steel slag-based cementitious materials of this application can be used in different scenarios.

[0071] In Comparative Example 1, without modified steel slag, the content of f-CaO and f-MgO in the steel slag was significantly increased compared to Example 1, indicating that modifying the steel slag beforehand can effectively reduce the content of f-CaO and f-MgO in the steel slag. In Comparative Examples 2-3, only a single anion salt was used to modify the steel slag, compared to Example 1 where two anion salts were used simultaneously for modification. The content of f-CaO and f-MgO in the steel slag was significantly increased compared to Example 1, indicating that the silicates and formates used in this application have a synergistic effect.

[0072] In Comparative Example 4, when no additives were added to the steel slag-based cementitious material, the compressive strength and unconfined compressive strength of the material decreased, indicating that adding additives can enhance the compressive strength and unconfined compressive strength of the material.

[0073] In Comparative Example 5, when carbon dioxide treatment was not used during the preparation of the steel slag-based cementitious material, the content of f-CaO and f-MgO in the material increased compared to Comparative Examples 2-3, indicating that carbon dioxide treatment can further reduce the content of f-CaO and f-MgO in the material.

[0074] In summary, this application modifies steel slag to reduce the content of free calcium and free magnesium, and improve the activity of steel slag, so that the resulting steel slag-based cementitious material has good mechanical properties, durability and stability, and improves the utilization rate of steel slag.

[0075] The foregoing has provided a detailed description of a steel slag-based cementitious material, its preparation method, and its applications. The specific embodiments described are merely illustrative of the invention's method and core concepts. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

[0076] It should be noted that: for experimental steps or conditions not specified in the examples, the procedures and conditions described in conventional experimental procedures in the literature of this art can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A steel slag-based cementitious material, characterized in that, The raw materials for the steel slag-based cementitious material include modified steel slag, slag, gypsum, silicate cement, and auxiliary materials. The modified steel slag is obtained by mixing and reacting acid salts with steel slag.

2. The steel slag-based cementitious material according to claim 1, characterized in that, The anions include at least one of phosphates, silicates, sulfates, and formates; And / or, the excipients include at least one of nano-silica, steel fiber, basalt fiber, and polypropylene fiber; And / or, the slag includes at least one of blast furnace slag and granulated blast furnace slag; And / or, the gypsum includes at least one of phosphogypsum, natural gypsum, and desulfurized gypsum.

3. The steel slag-based cementitious material according to claim 2, characterized in that, The mass ratio of the anion salt to the steel slag is (1-4):

100.

4. The steel slag-based cementitious material according to claim 2, characterized in that, The ratio of the total mass of the slag and gypsum to the mass of the anhydride is (5-37):(0.8-1). And / or, the mass ratio of the auxiliary material to the modified steel slag is (0.2-0.5):

100.

5. The steel slag-based cementitious material according to claim 2, characterized in that, The mass ratio of the silicate to the formate is 1:(0.5-1); And / or, the ratio of the formate to the total mass of silicate cement and auxiliary materials is (4-20):(102-145).

6. A method for preparing a steel slag-based cementitious material as described in any one of claims 1-5, characterized in that, Includes the following steps: Modified steel slag, slag and gypsum are mixed evenly, crushed and then added with auxiliary materials and silicate cement, and stirred to obtain steel slag-based cementitious material.

7. The preparation method according to claim 6, characterized in that, The pulverization process includes mixing modified steel slag, slag and gypsum, pulverizing to 20-100 mesh, and then treating with carbon dioxide to obtain the pulverized intermediate material.

8. The preparation method according to claim 7, characterized in that, The carbon dioxide treatment includes treatment for 30-120 minutes under conditions of pressure of 0.5-1.2 MPa and temperature of 60-100℃.

9. The preparation method according to claim 6 or 7, characterized in that, The stirring process includes stirring at 60-120 rpm for 5-10 minutes, then adding water and standard sand, and stirring for 20-40 minutes to obtain a steel slag-based cementitious material.

10. The application of a steel slag-based cementitious material prepared by the method for preparing steel slag-based cementitious materials according to any one of claims 1-5 or claims 6-9, characterized in that, It is used in at least one of the following: roadbed paving and building materials.

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