Carbon sequestration cementitious material based on alkali salt activated recycled micro-powder and preparation method thereof

Abstract

The application belongs to the field of alkali salt activated inorganic non-metallic cementitious materials, and particularly relates to a kind of alkali salt activated carbon sequestration cementitious materials based on recycled micro powder, which comprises, by mass fraction, 40-50 parts of recycled micro powder, 20-40 parts of blast furnace slag, 10-20 parts of steel slag, 5-8 parts of alkali salt activator, 5-10 parts of inorganic cementing aid, and 0.0005-0.002 parts of reaction activity promoter.The alkali salt activator is Na2CO3; the inorganic cementing aid is MgO; and the reaction activity promoter is basic magnesium carbonate tetrahydrate.The alkali salt activated carbon sequestration cementitious material based on recycled micro powder mainly utilizes recycled micro powder, slag and steel slag generated in the process of urban demolition, and can absorb a part of CO2 during the curing process and improve its compressive strength.

Description

Technical Field

[0001] This invention belongs to the field of salt-activated inorganic non-metallic cementitious materials, and relates to an alkali-salt activated carbon-fixing cementitious material based on recycled micro powder and its preparation method. Background Technology

[0002] In today's rapidly developing economy and technology, people's high demands for housing and working environments have spurred the reconstruction and renovation of buildings. The refurbishment and demolition of buildings generate a large amount of waste, which has become one of the biggest environmental pollution problems. The ever-increasing volume makes the disposal of construction waste an urgent matter. According to reports, the annual output of construction waste in recent years has far exceeded the amount of household waste, making it the largest source of solid waste in cities, accounting for 40% of urban solid waste.

[0003] The most widely used activators for alkali-activated cementitious materials (AAC) are NaOH, water glass, and combinations of NaOH and water glass. However, these activators are the most expensive components in alkali-activated cementitious material systems, exhibit rapid drying shrinkage and hardening, are corrosive, and are major sources of greenhouse gas emissions during AAC production. These factors hinder the widespread practical application of AAC. Alkali salt activators can play an important role in overcoming these drawbacks. Sodium carbonate (Na₂CO₃) is one such example.

[0004] In the 21st century, the effective utilization of resources has become particularly important, with the secondary utilization of recycled construction waste powder being of paramount importance. To address these issues, the comprehensive utilization of recycled powder and improving its utilization rate have become research hotspots in recent years. The preparation of carbon-fixing cementitious materials from recycled powder through alkali-salt activation is one of the effective ways to utilize recycled powder resources. In recent years, scholars both domestically and internationally have conducted continuous research on this topic. Therefore, seeking a convenient and effective method for utilizing recycled powder, and subsequently preparing cementitious materials in large quantities to achieve the comprehensive utilization of recycled construction waste powder, is becoming increasingly important. Summary of the Invention

[0005] To address the shortcomings of existing alkali-activated cementitious materials technology, this invention proposes an alkali-salt activated carbon-fixing cementitious material based on recycled micropowder and its preparation method. This addresses the defects of existing alkali-activated cementitious materials, such as rapid drying shrinkage and hardening, and corrosiveness. Furthermore, it can capture carbon dioxide, providing an effective way to comprehensively utilize recycled micropowder.

[0006] An alkali-salt activated carbon-fixing cementitious material based on recycled micropowder, comprising, by weight parts: 40-50 parts recycled micropowder, 20-40 parts blast furnace slag, 10-20 parts steel slag, 5-8 parts alkaline salt activator, and 5-10 parts...

[0007] Inorganic gelling aid and 0.0005 to 0.002 parts of reactivity promoter.

[0008] As a further description of the above scheme, the recycled powder, by mass percentage, comprises 70-75% recycled clay brick powder and 25-30% recycled C30 concrete powder.

[0009] As a further description of the above scheme, the regenerated micro powder has a particle size of less than 0.075 mm.

[0010] As a further description of the above scheme, the chemical composition and mass fraction of the blast furnace slag are: CaO 30-37%, SiO2 30-36%, Al2O3 15-19%, MgO 9-15%, and Fe2O3 1-2%, with the remainder being impurities; the particle size of the blast furnace slag is 25µm-35µm.

[0011] As a further description of the above scheme, the chemical composition and mass fraction of the steel slag are: CaO 30-40%, Fe2O3 18-25%, SiO2 12-16%, MgO 8-12%, and Al2O3 5-8%, with the remainder being impurities; the particle size of the steel slag is 35um-45um, and the steel slag has undergone pre-carbonization treatment.

[0012] As a further description of the above scheme, the alkaline salt activator is sodium carbonate (Na2CO3) with analytical purity.

[0013] As a further description of the above scheme, the inorganic gelling aid is light-burned magnesium oxide, with an activity of 60% to 65% and a purity of 80% to 85%.

[0014] As a further description of the above scheme, the reaction promoter is basic magnesium carbonate tetrahydrate 4MgCO3·Mg(OH)2·4H2O, with analytical purity.

[0015] A method for preparing the above-mentioned alkaline salt activated carbon-fixing cementitious material based on recycled micropowder includes the following steps: preparing raw materials according to the following mass ratio: 30-50 parts recycled micropowder, 20-40 parts blast furnace slag, 10-20 parts steel slag, 5-8 parts alkaline salt activator, 5-10 parts inorganic cementing aid, and 0.0005-0.002 parts reactive accelerator; mixing the above raw materials at a water-cement ratio of 0.5±0.02, calculating the mass of water, and uniformly dispersing the reactive accelerator in the water using a magnetic stirrer; grinding the recycled micropowder to below 0.075 mm; placing the steel slag powder into a dry carbonization kettle, with a CO2 pressure of 0.5±0.02 MPa and a carbonization kettle temperature of 60±1.5℃, and pre-carbonizing for 60±2 min;

[0016] Regenerated micro powder, blast furnace slag, steel slag, alkaline salt activator, and inorganic cementitious aid are added to a mixer and stirred evenly. Then, the reaction accelerator mixed with water is poured into the mixing pot. The mixture is stirred at low speed for 30±2 seconds. In the next 30±2 seconds, standard sand is completely poured into the mixing pot. The mixing is stopped for 30±2 seconds, and any unevenly mixed material at the bottom of the pot is manually stirred until uniform. Simultaneously, the slurry on the blades and pot walls is scraped into the center of the pot. Then, high-speed stirring is performed for 60±4 seconds to obtain the alkali-salt activated carbon-fixing cementitious material slurry. The low-speed stirring refers to stirring at a speed of 90±5 rpm; the high-speed stirring refers to stirring at a speed of... Stir at a speed of 120±5 rpm; pour the uniformly stirred alkali-salt activated carbon-fixing cementitious material slurry into a mold, place it in an environment of 20±2℃ to solidify and harden, then remove the mold, and place it in a carbonization kettle for CO2 carbonization curing; the water level in the carbonization kettle is 40±2mm, the initial curing conditions are CO2 pressure 0.5±0.02Mpa, 80±5% relative humidity and 30±1.5℃, after the carbonization kettle is heated to 60±1.5℃ within 0.5h, continue curing for 30±2min, and then perform standard curing to obtain the alkali-salt activated carbon-fixing cementitious material based on recycled micro powder.

[0017] As a further description of the above scheme, the mold has a size of 40mm×40mm×40mm, and the setting and hardening time of the alkali-salt activated carbon-fixing cementitious material slurry is 24 hours.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. The alkali-salt activated carbon-fixing cementitious material based on recycled micropowder described in this invention mainly utilizes the recycled micropowder produced after preparing recycled aggregate from urban building demolition waste. By adding appropriate amounts of steel slag and blast furnace slag, the alkali-salt activated cementitious material can be achieved, allowing for the secondary utilization of the recycled micropowder. This solves the problem of recycled micropowder consumption and utilization. This patent can be applied to the field of prefabricated construction technology. Compared with existing technologies, this product is inexpensive and environmentally friendly, and its strength is comparable to prefabricated components produced using OPC concrete.

[0020] 2. The alkaline salt activator selected in this invention is sodium carbonate, which has the advantages of low cost, low pollution, weak corrosiveness, and less alkali return in the later stage compared with traditional alkaline activators such as sodium hydroxide or water glass.

[0021] 3. The inorganic cementing agent selected in this invention is magnesium oxide, which has a micro-expansion effect and can alleviate part of the drying shrinkage effect of the recycled micro powder-slag cementitious material.

[0022] 4. The reaction promoter selected in this invention is basic magnesium carbonate tetrahydrate, which can provide additional nucleation sites in the early stage of cementitious material formation, improve the compactness of the microstructure, and enhance the hydration and carbonization potential of cementitious material, thus promoting the later strength development of cementitious material.

[0023] 5. The curing method selected in this invention involves maintaining a water level of 40±2mm in the carbonization reactor, with initial curing conditions of CO2 pressure of 0.5±0.02Mpa, relative humidity of 80±5%, and temperature of 30±1.5℃. After the carbonization reactor is heated to 60±1.5℃ within 0.5 hours, curing continues for another 0.5 hours, followed by standard curing. This method not only improves early strength but also significantly consumes carbon dioxide generated in industrial production, aligning with the environmental protection concept of "carbon peaking and carbon neutrality." Attached Figure Description

[0024] Figure 1 This is an internal image of the magnesium oxide-sodium carbonate alkali salt co-activated carbon cementitious material under a scanning electron microscope after 3 days of curing, according to Example 1 of the present invention.

[0025] Figure 2 This is an internal image of the magnesium oxide-sodium carbonate alkali salt co-activated carbon cementitious material under a scanning electron microscope after 7 days of curing, according to Example 1 of the present invention.

[0026] Figure 3 This is an internal image of the magnesium oxide-sodium carbonate alkali salt co-activated carbon cementitious material under a scanning electron microscope after 28 days of curing, according to Example 1 of the present invention. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0028] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0029] In the following examples, the "percentage" refers to parts by weight of the total material weight.

[0030] In the examples described below, a 28-day compressive strength of 42.5 MPa indicates that the formulation has the potential to replace 425 cement.

[0031] An alkali-salt activated carbon-fixing cementitious material based on recycled micropowder, comprising, by weight: 40-50 parts recycled micropowder, 20-40 parts blast furnace slag, 10-20 parts steel slag, 5-8 parts alkaline salt activator, 5-10 parts inorganic cementitious aid, and 0.0005-0.002 parts reactivity promoter. This invention utilizes recycled micropowder, specifically the recycled micropowder produced after preparing recycled aggregate from urban building demolition waste. By adding appropriate amounts of steel slag and blast furnace slag, the alkali-salt activated cementitious material is achieved, allowing for the secondary utilization of the recycled micropowder. This solves the problem of recycled micropowder consumption and utilization. This patent can be applied to the field of prefabricated construction technology. Compared to existing technologies, this product is inexpensive and environmentally friendly, and its strength is comparable to prefabricated components produced using OPC concrete.

[0032] The recycled micro powder of the present invention comprises, by mass percentage, 70-75% recycled clay brick powder and 25-30% recycled C30 concrete powder.

[0033] The regenerated micro powder of the present invention has a particle size of less than 0.075 mm.

[0034] The blast furnace slag of the present invention is a residue generated during the iron and steel smelting process. The chemical composition and mass fraction of the blast furnace slag are as follows: CaO 30-37%, SiO2 30-36%, Al2O3 15-19%, MgO 9-15%, and Fe2O3 1-2%, with the remainder being impurities. The particle size of the blast furnace slag is 25μm-35μm.

[0035] The steel slag of this invention is hot-quenching steel slag, wherein the chemical composition and mass fraction of the steel slag are: CaO 30-40%, Fe2O3 18-25%, SiO2 12-16%, MgO 8-12%, and Al2O3 5-8%, with the remainder being impurities; the particle size of the steel slag is 35um-45um, and the steel slag is used as a reaction raw material after pre-carbonization treatment.

[0036] The alkaline salt activator of this invention is sodium carbonate (Na₂CO₃) with analytical purity. Compared to traditional alkaline activators such as sodium hydroxide or water glass, sodium carbonate has advantages such as lower cost, less pollution, weaker corrosiveness, and less subsequent alkali return.

[0037] The inorganic cementing aid of this invention is light-burned magnesium oxide, with an activity of 60%–65% and a purity of 80%–85%. In this embodiment of the invention, magnesium oxide is selected because it has a micro-expansion effect, which can alleviate some of the drying shrinkage effect of the recycled micro-powder-slag cementitious material.

[0038] The reaction promoter of this invention is basic magnesium carbonate tetrahydrate 4MgCO3·Mg(OH)2·4H2O, with analytical purity. The basic magnesium carbonate tetrahydrate selected in this invention can provide additional nucleation sites in the early stages of cementitious material formation, improving the compactness of the microstructure and enhancing the hydration and carbonization potential of the cementitious material, thus promoting the later-stage strength development of the cementitious material.

[0039] The above-mentioned preparation method of alkali-salt activated carbon-fixing cementitious material based on recycled micro powder includes the following steps:

[0040] Includes the following steps:

[0041] Prepare the raw materials according to the following proportions by weight: 30-50 parts recycled micro powder, 20-40 parts blast furnace slag, 10-20 parts steel slag, 5-8 parts alkaline salt activator, 5-10 parts inorganic cementing aid, and 0.0005-0.002 parts reaction accelerator; the water-cement ratio of the above raw materials should be 0.5 ± 0.02, determined by water-cement ratio = m 水 / m 前体 Calculate the mass m of the water 水， In the formula m 前体 The total mass of the recycled micro powder, slag, and steel slag was used. A reactive accelerator was uniformly dispersed in water using a magnetic stirrer. The recycled micro powder was ground to below 0.075 mm. The steel slag powder was placed in a dry carbonization reactor at a CO2 pressure of 0.5 ± 0.02 MPa and a reactor temperature of 60 ± 1.5℃ for 60 ± 2 minutes of pre-carbonization. This design places the steel slag in a CO2 gas environment and carbonizes it under specific temperature, humidity, and pressure conditions. The CO2 is fixed and stored in the form of mineral absorption, which not only solidifies a large amount of CO2 but also enables the effective utilization of secondary resources. Simultaneously, the formation of new phases during the carbonization process binds the substances within the system together, resulting in building materials with advantages such as high strength, low price, and good stability.

[0042] Regenerated micro powder, blast furnace slag, steel slag, alkaline salt activator, and inorganic cementitious aid are added to a mixer and stirred evenly. Then, the reaction accelerator mixed with water is poured into the mixing pot. The mixture is stirred at low speed for 30±2 seconds. In the next 30±2 seconds, standard sand is completely poured into the mixing pot. The mixing is stopped for 30±2 seconds, and any unevenly mixed material at the bottom of the pot is manually stirred until uniform. Simultaneously, the slurry on the blades and pot walls is scraped into the center of the pot. Then, high-speed stirring is performed for 60±4 seconds to obtain the alkali-salt activated carbon-fixing cementitious material slurry. Low-speed stirring refers to a stirring speed of 90±5 rpm; high-speed stirring refers to a stirring speed of 120±5 rpm. Stirring at a clock speed; pour the uniformly stirred alkali-salt activated carbon-fixing cementitious material slurry into a 40mm×40mm×40mm mold, place it in an environment of 20±2℃ for 24 hours to solidify and harden, then remove the mold, and place it in a carbonization kettle for CO2 carbonization curing; the water level in the carbonization kettle is 40±2mm, the initial curing conditions are CO2 pressure 0.5±0.02Mpa, 80±5% relative humidity and 30±1.5℃, after the carbonization kettle temperature is raised to 60±1.5℃ within 0.5h, continue curing for 0.5h, and then perform standard curing to obtain the alkali-salt activated carbon-fixing cementitious material based on recycled micro powder. The curing method selected in this invention involves maintaining a water level of 40±2mm in the carbonization reactor, with initial curing conditions of CO2 pressure of 0.5±0.02Mpa, relative humidity of 80±5%, and temperature of 30±1.5℃. After the carbonization reactor is heated to 60±1.5℃ within 30±2 minutes, curing continues for 0.5 hours, followed by standard curing. This method not only improves early strength but also significantly consumes carbon dioxide generated in industrial production, aligning with the environmental protection concept of "carbon peaking and carbon neutrality."

[0043] Example 1

[0044] Add 50 parts of recycled micro powder, 40 parts of blast furnace slag, 10 parts of steel slag, and an additional 5 parts of alkaline salt activator and 8 parts of inorganic cementitious agent by weight of the total materials to the mixer. Mix at 120±5 rpm for 30 seconds until homogeneous. Then, mix 0.002 parts of reactive accelerator evenly in water and add it to the mixing pot. Stir at low speed for 30±2 seconds. In the next 30 seconds, pour the standard sand completely into the mixing pot. Stop stirring for 30 seconds and manually stir the unevenly mixed material at the bottom of the pot. At the same time, scrape the slurry on the blades and the pot wall into the middle of the pot. Then, stir at 290±5 rpm for 60±4 seconds to obtain the alkali-salt activated cementitious material slurry. The uniformly mixed alkali-salt activated carbon-fixing cementitious material slurry based on recycled micropowder was poured into a 40mm×40mm×40mm mold. After 24 hours of solidification, the mold was removed, and the material was placed in a carbonization kettle for curing. The water level in the carbonization kettle was 40±2mm. The initial curing conditions were CO2 pressure 0.5±0.02Mpa, relative humidity 80±5%, and 30±1.5℃. After the temperature of the carbonization kettle was raised to 60±1.5℃ within 0.5h, curing continued for another 0.5h, followed by standard curing. The resulting alkali-salt activated carbon-fixing cementitious material specimens were subjected to strength tests. The 3-day unconfined compressive strength was 26.3Mpa, and the 28-day unconfined compressive strength was 44.9Mpa.

[0045] Example 2

[0046] Add 40 parts of recycled micro powder, 30 parts of blast furnace slag, 10 parts of steel slag, and an additional 6 parts of alkaline salt activator and 10 parts of inorganic cementitious agent by weight of the total materials to the mixer. Mix at 120±5 rpm for 30 seconds until homogeneous. Then, mix 0.002 parts of reactive accelerator evenly in water and add it to the mixing pot. Stir at low speed for 30±2 seconds. In the next 30±2 seconds, pour the standard sand completely into the mixing pot. Stop stirring for 30±2 seconds and manually stir the unevenly mixed material at the bottom of the pot. At the same time, scrape the slurry on the blades and the pot wall into the middle of the pot. Then, stir at 290±5 rpm for 60±4 seconds to obtain the alkali-salt activated cementitious material slurry. The uniformly mixed alkali-salt activated carbon-fixing cementitious material slurry based on recycled micropowder was poured into a 40mm×40mm×40mm mold. After 24 hours of solidification, the mold was removed, and the material was placed in a carbonization kettle for curing. The water level in the carbonization kettle was 40±2mm. The initial curing conditions were CO2 pressure 0.5±0.02Mpa, relative humidity 80±5%, and 30±1.5℃. After the temperature of the carbonization kettle was raised to 60±1.5℃ within 0.5h, curing continued for another 0.5h, followed by standard curing. The resulting alkali-salt activated carbon-fixing cementitious material specimens were subjected to strength tests. The 3-day unconfined compressive strength was 27.1Mpa, and the 28-day unconfined compressive strength was 42.6Mpa.

[0047] Example 3

[0048] Add 50 parts of recycled micro powder, 35 parts of blast furnace slag, 15 parts of steel slag, and an additional 7 parts of alkaline salt activator and 5 parts of inorganic cementitious agent by weight of the total materials to the mixer. Mix at 120±5 rpm for 30 seconds until homogeneous. Then, mix 0.001 parts of reactive accelerator evenly in water and add it to the mixing pot. Stir at low speed for 30±2 seconds. In the next 30 seconds, pour the standard sand completely into the mixing pot. Stop stirring for 30 seconds and manually stir the unevenly mixed material at the bottom of the pot. At the same time, scrape the slurry on the blades and the pot wall into the middle of the pot. Then, stir at 290±5 rpm for 60±4 seconds to obtain the alkali-salt activated cementitious material slurry. The uniformly mixed alkali-salt activated carbon-fixing cementitious material slurry based on recycled micropowder was poured into a 40mm×40mm×40mm mold. After 24 hours of solidification, the mold was removed, and the material was placed in a carbonization kettle for curing. The water level in the carbonization kettle was 40±2mm. The initial curing conditions were CO2 pressure 0.5±0.02Mpa, relative humidity 80±5%, and 30±1.5℃. After the temperature of the carbonization kettle was raised to 60±1.5℃ within 0.5h, curing continued for another 0.5h, followed by standard curing. The resulting alkali-salt activated carbon-fixing cementitious material specimens were subjected to strength tests. The 3-day unconfined compressive strength was 23.1Mpa, and the 28-day unconfined compressive strength was 42.9Mpa.

[0049] Example 4

[0050] Add 30 parts of recycled micro powder, 40 parts of blast furnace slag, 20 parts of steel slag, and an additional 8 parts of alkaline salt activator and 10 parts of inorganic cementitious agent by weight of the total materials to the mixer. Mix at 120±5 rpm for 30 seconds until homogeneous. Then, mix 0.0005g of the reactive accelerator evenly in water and add it to the mixing pot. Mix at low speed for 30±2 seconds. In the next 30 seconds, pour the standard sand completely into the mixing pot. Stop mixing for 30 seconds and manually mix the unevenly mixed material at the bottom of the pot. At the same time, scrape the slurry on the blades and the pot wall into the middle of the pot. Then, mix at 290±5 rpm for 60±4 seconds to obtain the alkali-salt activated cementitious material slurry. The uniformly mixed alkali-salt activated carbon-fixing cementitious material slurry based on recycled micropowder was poured into a 40mm×40mm×40mm mold. After 24 hours of solidification and hardening, the mold was removed, and the material was placed in a carbonization kettle for curing. The water level in the carbonization kettle was 40±2mm. The initial curing conditions were CO2 pressure 0.5±0.02Mpa, relative humidity 80±5%, and 30±1.5℃. After the temperature of the carbonization kettle was raised to 60±1.5℃ within 0.5h, curing continued for another 0.5h, followed by standard curing. The resulting alkali-salt activated carbon-fixing cementitious material specimens were subjected to strength tests. The 3-day unconfined compressive strength was 23.0Mpa, and the 28-day unconfined compressive strength was 44.5Mpa.

[0051] Figure 1 The image shown is an internal image of the magnesium oxide-sodium carbonate alkali-salt co-activated carbon-fixing cementitious material under a scanning electron microscope after 3 days of curing, as described in Example 1. It can be seen that the surface morphology of the carbon-fixing cementitious material sample prepared using the alkali-salt co-activation method of this invention is more diverse, with a large aggregation of brucite, hydrotalcite-like minerals, and gel products. Flocculated, plate-like, and crystalline hydration products can be observed, and a dense microstructure is visible. Therefore, it can be concluded that the brucite generated in the early stage of hydration of the alkali-salt co-activated cementitious material of this invention plays a connecting role in the slurry, making the slurry denser and exhibiting higher compressive strength.

[0052] Figure 2 The image shown is an internal image of the magnesium oxide-sodium carbonate alkali-salt co-activated carbon cementitious material under a scanning electron microscope after 7 days of curing. It can be seen that a large number of gel phases CSH and CASH are formed in the carbon cementitious material prepared by the alkali-salt co-activated method of the present invention. A large number of flocculent gels and hydrotalcite-like phases are intertwined, and the internal structure of the sample is significantly improved.

[0053] Figure 3The image shown is an internal image of the magnesium oxide-sodium carbonate alkali-activated carbon-fixing cementitious material under a scanning electron microscope after 28 days of curing, as described in Example 1. It can be seen that the area of ​​weak zones in the carbon-fixing cementitious material prepared using the alkali-salt co-activation method of this invention is significantly reduced, the microstructure is denser, and the CSH gel phase is increased. Therefore, the alkali-salt co-activated cementitious material of this invention can form a hydrotalcite phase in the early stage of hydration, providing nucleation sites for the formation of the gel phase in the later stage, thereby improving the later compressive strength of the cementitious material.

Claims

1. A regenerative micropowder-based alkali salt-activated carbon sequestering cementitious material, characterized in that: By mass parts, including: 40~ 50 parts of recycled powder, 20 ~ 40 parts of blast furnace slag, 10~ 20 parts of steel slag, 5~ 8 parts of alkaline salt activator, 5~10 parts of inorganic cementing aid and 0.0005~ 0.002 parts of reaction activity promoter; The recycled powder includes recycled clay red brick powder 70~75% and recycled C30 concrete powder 25~30% by mass percentage; The recycled powder particle size is 0.075mm below; The blast furnace slag has a chemical composition and mass fraction of CaO 30-37%, SiO2 30-36%, Al2O ３ 15-19%, MgO 9-15%, and Fe2O3 1-2%, and the rest is impurities; the blast furnace slag has a particle size of 25-35 um; The steel slag chemical composition and mass fraction are: CaO 30~40%, Fe2O3 18~25%, SiO2 12~16%, MgO 8~12% and Al2O3 5~8%, and the rest is impurities; The steel slag particle size is 35um~45um, and the steel slag is subjected to pre-carbonization treatment; The alkaline salt activator is sodium carbonate Na2CO3 with analytical purity; The inorganic cementing aid is light burned magnesium oxide with activity of 60%~65% and purity of 80~85%; The reaction activity promoter is basic magnesium carbonate 4MgCO3·Mg(OH)2·4H2O with analytical purity.

2. A method for producing an alkali salt-based carbon capture and utilization cementitious material based on recycled fines according to claim 1, characterized in that, Including the following steps: Prepare raw materials according to mass parts, 30~ 50 parts of recycled powder, 20 ~ 40 parts of blast furnace slag, 10~ 20 parts of steel slag, 5~8 parts of alkaline salt activator, 5~10 parts of inorganic cementing aid and 0.0005~ 0.002 parts of reaction activity promoter; The water-binder ratio of the above-mentioned raw materials mixed is 0.5±0.02, and the mass of water is calculated, the reaction activity promoter is uniformly dispersed in water by a magnetic stirrer; The recycled powder is ground to 0.075mm below; The steel slag is put into a dry carbonization kettle, the CO2 pressure is 0.5±0.02MPa, the carbonization kettle temperature is 60±1.5℃, and the pre-carbonization is 60±2min; The recycled powder, blast furnace slag, steel slag, alkaline salt activator and inorganic cementing aid are added into a stirring pot and stirred uniformly, then the reaction activity promoter mixed with water is poured into the stirring pot, low-speed stirring is carried out for 30±2s, the next 30±2s, the standard sand is completely poured into the stirring pot, the stirring is stopped for 30±2s, the uneven material at the bottom of the pot is manually stirred uniformly, at the same time, the slurry on the blade and the pot wall is scraped into the middle of the pot, and then high-speed stirring is carried out for 60±4s, that is, the alkaline salt activated carbon sequestration cementitious material slurry can be obtained; The low-speed stirring refers to stirring at a speed of 90±5r / min; The high-speed stirring refers to stirring at a speed of 120±5r / min; The uniformly stirred alkaline salt activated carbon sequestration cementitious material slurry is poured into a mold, placed in a 20±2℃ environment for coagulation and hardening, then demolded, and then placed in a carbonization kettle for CO2 carbonization curing; The water level in the carbonization kettle is 40±2mm, the initial curing conditions are CO2 pressure 0.5±0.02MPa, 80±5% relative humidity and 30±1.5℃, after the carbonization kettle is heated to 60±1.5℃ within 0.5h, the curing is continued for 30±2min, and then standard curing is carried out, to obtain the alkaline salt activated carbon sequestration cementitious material based on recycled powder.

3. The method for producing a carbon sequestration cementitious material based on a regenerative micropowdered alkali salt excitation according to claim 2, characterized in that: The size of the mold is 40mmx40mmx40mm, and the setting and hardening time of the alkali salt activated carbon sequestration cementitious material slurry is 24 hours.

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