Silicon-aluminum activation synergistic carbonization regenerated micro-powder auxiliary agent and preparation method thereof

Abstract

The invention relates to the technical field of building material and solid waste resource utilization, in particular to a silicon-aluminum activation synergistic carbonization regenerated micro-powder additive and a preparation method thereof. The preparation method comprises the following steps: dispersing regenerated cement micro powder from building solid waste as a raw material in a sodium bicarbonate aqueous solution at room temperature to form a suspension system, introducing CO2 for wet carbonization, and carrying out centrifugal separation and drying to obtain the target auxiliary agent. According to the method, Ca < 2 + > in C-S-H gel is promoted to release through a Na < + > charge shielding effect, HCO3 <-> maintains alkalinity and supplies carbonate, a carbonization reaction is synergistically accelerated, a product forms calcite, a vaterite phase and a silicon-aluminum-rich high-activity amorphous phase, and the chemical activity is remarkably improved. The additive can be applied to a cement-based or alkali-activated cementing material in a high doping amount of 10-60%, so that the mechanical property and durability of the material are effectively improved, high-valued utilization of building solid wastes and CO2 fixation are realized, and the requirements of green and low-carbon development are met.

Description

A silicon-aluminum activation synergistic carbonization regeneration micro powder additive and its preparation method Technical Field

[0001] This invention relates to the field of building materials and solid waste resource utilization technology, and in particular to a silicon-aluminum activation synergistic carbonization regeneration micro powder additive and its preparation method. Background Technology

[0002] With the rapid development of the global construction industry, the amount of construction solid waste generated has continued to rise, becoming one of the key issues restricting the industry's green transformation. Recycled cement powder (RP), as a major byproduct of recycled aggregate production, is seeing its output increase with the promotion and application of recycled building materials. If efficient resource utilization cannot be achieved, it will not only occupy a large amount of land resources but may also cause environmental problems such as dust pollution and ecological damage. Therefore, its high-value and low-carbon utilization has become an important research direction in the field of building materials and one of the important paths to achieving the "dual carbon" target.

[0003] However, traditional recycled cement powder has significant performance shortcomings, severely limiting its application range and dosage in cementitious materials. On the one hand, recycled cement powder generally has low chemical activity and high water demand. Directly incorporating it into cement-based materials or alkali-activated cementitious materials significantly dilutes the active components in the system, destroying the density of the cementitious structure and leading to a substantial decrease in the material's compressive strength, elastic modulus, and other mechanical properties. This performance degradation is particularly pronounced when the dosage exceeds 30%, making it difficult to meet engineering application requirements. On the other hand, recycled cement powder contains a large amount of unhydrated clinker phase and highly stable CSH gel, whose internal Ca... 2+ It is difficult to release effectively, which further reduces its synergistic reaction with the gelling system.

[0004] To improve the performance of recycled cement powder, existing technologies often employ carbonization, but these methods still have many shortcomings. Traditional wet carbonization technology mainly relies on the physical contact between CO2 and the surface of recycled powder to achieve densification, resulting in low carbonization reaction efficiency and difficulty in penetrating deep into the powder to trigger chemical activation, thus failing to fundamentally improve the reactivity of silicon and aluminum components. While dry carbonization methods can accelerate the carbonization rate to some extent, they are insufficient in disrupting the Si-O-Ca bonds within the CSH gel, leading to insufficient Ca... 2+ Insufficient release results in limited chemical activation of recycled micropowder. Furthermore, existing carbonization technologies struggle to balance the contradiction between "high-volume solid waste disposal" and "material performance improvement." In scenarios where recycled cement micropowder content exceeds 40%, the mechanical and durability properties of cementitious materials often fail to meet engineering standards. Additionally, there is a lack of precise control over the carbonization process, making it difficult to achieve synergistic optimization of carbonization efficiency, chemical activation effect, and environmental benefits.

[0005] Therefore, how to develop an efficient recycled cement powder modification technology that can significantly improve its chemical activity and accelerate the carbonization reaction kinetics, thereby simultaneously improving the mechanical and durability properties of cementitious materials under high dosage conditions, while also taking into account the environmental protection requirements of solid waste disposal and carbon fixation, has become a technical bottleneck that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and to propose a silicon-aluminum activation synergistic carbonization regeneration micro powder additive and its preparation method.

[0007] Based on the above objectives, the present invention provides a method for preparing a silicon-aluminum activated synergistic carbonization regenerated micro powder additive, comprising the following steps: (1) at room temperature, adding regenerated cement micro powder into an aqueous solution of sodium bicarbonate and stirring to form a suspension system; (2) under stirring, introducing CO2 into the suspension system to carry out a wet carbonization reaction; (3) after carbonization, centrifuging to separate the solid and drying to obtain a silicon-aluminum activated synergistic carbonization regenerated micro powder additive.

[0008] Preferably, the recycled cement powder in (1) is obtained from waste concrete, waste mortar, or solid waste from building demolition after crushing, grading, and sieving, and has a specific surface area ≥980m². 2 / kg.

[0009] Preferably, the recycled cement powder in (1) comprises CSH gel, calcium hydroxide and unhydrated clinker phase.

[0010] Preferably, in step (1), the ratio of recycled cement powder to sodium bicarbonate aqueous solution is 1:3-5, where the unit of the solid-liquid ratio is g / ml.

[0011] Preferably, the concentration of sodium bicarbonate in the sodium bicarbonate aqueous solution in (1) is 0.05-3 mol / L.

[0012] Preferably, the pH of the suspension system in (1) is 12.7-12.8.

[0013] Preferably, in step (2), CO2 is introduced by gas introduction, solution saturation, pressure release or any combination thereof; wherein the purity of CO2 gas is ≥99.99%.

[0014] Preferably, the CO2 in step (2) is introduced at a rate of 0.1-0.5 mL / min / g.

[0015] Preferably, the wet carbonization reaction time in (2) is 40-80 min.

[0016] Preferably, in the wet carbonization reaction of (2), Na... +The charge shielding effect weakens Si-O-Ca bonding in CSH gels and promotes Ca2+ bonding. 2+ Release; HCO3 - Maintaining the alkalinity of the solution and providing carbonate ions accelerates the carbonation reaction kinetics.

[0017] Preferably, the silicon-aluminum activation synergistic carbonization regeneration micro powder additive in (3) comprises a calcium carbonate phase formed by calcite, aragonite or a combination thereof.

[0018] Preferably, the silicon-aluminum activated synergistic carbonization regenerated micro powder additive in (3) has a reduced Ca content and increased Si and Al chemical activity after wet carbonization.

[0019] Furthermore, the present invention also provides a silicon-aluminum activation synergistic carbonization regeneration micro powder additive, which is prepared by the above-described preparation method.

[0020] Furthermore, the present invention also provides an application of a silicon-aluminum activated synergistic carbonization regenerated micro powder additive in cementitious materials.

[0021] Preferably, the cementitious material is a cement-based material or an alkali-activated cementitious material.

[0022] Preferably, the dosage of the silicon-aluminum activated synergistic carbonization regenerated micro powder additive in the cementitious material is 10-60%.

[0023] Preferably, the mechanism of action of the preparation method of the silicon-aluminum activation synergistic carbonization regeneration micro powder additive in this invention is explained as follows: The core mechanism of action of the preparation method of the silicon-aluminum activation synergistic carbonization regeneration micro powder additive in this invention revolves around the Na in sodium bicarbonate aqueous solution. + With HCO3 - The synergistic effect is realized by combining wet carbonization reaction to achieve chemical activation and performance optimization of recycled cement powder. At room temperature, after the recycled cement powder is dispersed in a sodium bicarbonate aqueous solution to form a suspension system, Na… + Firstly, the charge shielding effect is applied to the CSH gel structure in the micronized powder, effectively weakening the stability of the Si-O-Ca bonds within the gel and disrupting the original chemical bond equilibrium, thereby promoting Ca... 2+ It is rapidly released from the gel lattice into the solution; simultaneously, HCO3... - It plays a dual role: on the one hand, it acts as a buffer system to maintain the alkaline environment of the solution, providing stable chemical conditions for the carbonation reaction; on the other hand, it acts as a carbonate precursor, accelerating the dissolution and conversion of the introduced high-purity CO2 in the aqueous solution, continuously supplying CO3 for the reaction. 2- Under conditions of stirring and continuous CO2 introduction, Ca released from the CSH gel 2+ With CO3 in the solution 2-A rapid chemical reaction occurs, producing calcium carbonate crystals in the form of calcite, aragonite, or combinations thereof. These crystals not only fill the pores within the system but also enhance the structural density of the final product; while the removal of Ca... 2+ The residual gel structure is then reconstructed, transforming into a highly chemically active amorphous phase rich in silicon and aluminum, significantly enhancing the reactivity and leaching capacity of Si and Al in the regenerated micropowder. Throughout the process, Na... + The charge shielding effect of HCO3 2- The pH buffering and carbonate supply functions work together to accelerate the carbonation reaction kinetics, which not only solves the problems of low activity and limited carbonation efficiency of traditional recycled cement powder, but also, through the activation of silicon-aluminum components and the formation of calcium carbonate crystals, gives the final additive excellent structural characteristics and reactivity, laying the foundation for its high-volume application in cementitious materials and improving the mechanical and durability properties of the materials.

[0024] The beneficial effects of this invention are: 1. This invention utilizes Na in sodium bicarbonate aqueous solution. + With HCO3 - The synergistic effect of Na significantly accelerates the carbonation reaction kinetics of recycled cement powder. + By weakening the Si-O-Ca bonds within the CSH gel through charge shielding, Ca2+ is promoted. 2+ Rapid release of HCO3 - This maintains the system's stable alkalinity and continuously supplies carbonate ions, allowing the carbonation reaction to be more complete and efficient. Simultaneously, the residual gel structure after decalcification is reconstructed into a highly active amorphous phase rich in silicon and aluminum, significantly enhancing the chemical activity and reaction potential of the silicon-aluminum components. This fundamentally solves the technical challenges of low activity and limited carbonation efficiency in traditional regenerated micropowders, providing core support for their high-value applications.

[0025] 2. The recycled micro-powder additive prepared by this invention possesses excellent adaptability to high dosage levels, allowing for large-scale addition to cementitious materials without performance degradation. The calcite and aragonite calcium carbonate crystals in the additive effectively fill the pores within the cementitious system, reducing porosity. Simultaneously, the silica-alumina-rich, highly active amorphous phase undergoes secondary reactions with the cementitious components, forming a dense and strongly bonded gel matrix. This characteristic overcomes the industry pain point of significant decline in mechanical properties at higher dosages of traditional recycled micro-powders, enabling cementitious materials to maintain stable and excellent compressive strength and elastic modulus at different dosages, providing technical support for large-scale disposal of construction solid waste.

[0026] 3. The recycled micro-powder additive prepared in this invention can improve the durability of cementitious materials from multiple dimensions and extend their long-term service life. The dense microstructure reduces seepage channels, significantly improves the material's impermeability, and effectively blocks water intrusion; simultaneously, it hinders the migration paths of harmful ions such as chloride ions, reducing the risk of seepage and providing reliable corrosion protection for building materials such as concrete. Furthermore, the calcium carbonate crystals contained in the additive itself can inhibit CO2 diffusion, reduce carbonation depth, and prevent performance degradation due to carbonation, enabling the material to adapt to complex and harsh engineering environments and expanding the application scenarios of cementitious materials.

[0027] 4. This invention achieves high-value utilization of construction solid waste while also providing significant low-carbon and environmental benefits. The carbonization reaction fixes a large amount of CO2, reducing carbon emissions throughout the entire lifecycle of building materials and contributing to the achievement of "dual carbon" goals. Furthermore, it can facilitate the large-scale disposal of construction byproducts such as recycled cement powder, reducing land use for solid waste disposal and mitigating environmental pollution risks. The entire preparation process is conducted under mild conditions, requiring no harsh processes such as high temperature and high pressure, resulting in low energy consumption. It achieves a triple synergy of "solid waste resource utilization, high-performance materials, and low environmental impact," driving the building materials industry towards a green and low-carbon transformation. Attached Figure Description

[0028] Figure 1 is a diagram of the carbonization device used in this invention and its working principle; Figure 2 is a diagram of the accelerated carbonization mechanism of NaHCO3 solution in this invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0030] Example 1: A specific preparation method of a silicon-aluminum activation synergistic carbonization regenerated micro powder additive, including the following steps: (1) Waste concrete (PO 42.5 cement, water-cement ratio 0.45) is crushed, graded and passed through a 75 µm sieve to obtain a specific surface area ≥980 m². 2 / kg of recycled cement powder; (2) At room temperature, in a carbonization device, the recycled cement powder is added to a sodium bicarbonate aqueous solution with a concentration of 0.05mol / L at a solid-liquid ratio of 1:3 (g / ml), and stirred to form a suspension system with pH=12.7-12.8; (3) Under stirring, high-purity CO2 gas (purity ≥99.99%) is introduced into the suspension system at a rate of 0.1mL / min / g for wet carbonization reaction, and the reaction time is 40min; (4) After carbonization, the solid is separated by centrifugation and dried to obtain a silicon-aluminum activated synergistic carbonization recycled powder additive.

[0031] Example 2: A specific preparation method of a silicon-aluminum activation synergistic carbonization regenerated micro powder additive, including the following steps: (1) Waste concrete (PO 42.5 cement, water-cement ratio 0.45) is crushed, graded and passed through a 75 µm sieve to obtain a specific surface area ≥980 m². 2 / kg of recycled cement powder; (2) At room temperature, in a carbonization device, the recycled cement powder is added to a sodium bicarbonate aqueous solution with a concentration of 0.5mol / L at a solid-liquid ratio of 1:4 (g / ml), and stirred to form a suspension system with pH=12.7-12.8; (3) Under stirring, high-purity CO2 gas (purity ≥99.99%) is introduced into the suspension system at a rate of 0.3mL / min / g for wet carbonization reaction, and the reaction time is 60min; (4) After carbonization, the solid is separated by centrifugation and dried to obtain a silicon-aluminum activated synergistic carbonization recycled powder additive.

[0032] Example 3: A specific preparation method of a silicon-aluminum activation synergistic carbonization regenerated micro powder additive, including the following steps: (1) Waste concrete (PO 42.5 cement, water-cement ratio 0.45) is crushed, graded and passed through a 75 µm sieve to obtain a specific surface area ≥980 m². 2 / kg of recycled cement powder; (2) At room temperature, in a carbonization device, the recycled cement powder is added to a sodium bicarbonate aqueous solution with a concentration of 3mol / L at a solid-liquid ratio of 1:5 (g / ml), and stirred to form a suspension system with pH=12.7-12.8; (3) Under stirring, high-purity CO2 gas (purity ≥99.99%) is introduced into the suspension system at a rate of 0.5mL / min / g for wet carbonization reaction, and the reaction time is 80min; (4) After carbonization, the solid is separated by centrifugation and dried to obtain a silicon-aluminum activated synergistic carbonization recycled powder additive.

[0033] Comparative Example: The difference between the comparative example and Example 2 is that the recycled cement powder obtained in step (1) is used directly, and steps (2)-(4) are omitted.

[0034] The calcite and aragonite content and Si / Al leaching results of the products of Examples 1-3 and the comparative examples are shown in Table 1.

[0035] Table 1. Characterization of products from Examples 1-3 and the comparative examples, and results of Si / Al leaching tests. Application Example: Alkali-activated concrete was prepared using the products from Example 2 and the comparative example at dosages of 10%, 30%, 40%, and 60%, respectively. The raw material proportions are shown in Table 2; among them, the slag powder has a specific surface area of ​​877 m². 2 / kg; Na2O·2SiO2, silicon-oxygen modulus 1.0; river sand particle size 0.075-4.75 mm, apparent density 2657 kg / m³ 3The coarse aggregate of granite has a particle size of 5-20 mm and an apparent density of 2451 kg / m³. 3 .

[0036] Table 2 Raw material proportions of alkali-activated concrete Preparation process: Add the recycled micro powder additive, fly ash, Na2SiO3, river sand and water to a horizontal mixer and mix for 2 minutes. Add the granite coarse aggregate and continue mixing for 1 minute. The total mixing time is 4 minutes. Pour the mixture into a mold, vibrate to remove bubbles for 1 minute, cover and cure for 24 hours, then demold. Cure in a standard curing room (humidity > 95%, 20℃) for 28 days.

[0037] The compressive strength, elastic modulus, impermeability, chloride ion penetration and carbonation resistance of alkali-activated concrete prepared with different amounts of recycled micro-powder additives in the corresponding use cases were tested. The experimental results are shown in Table 3.

[0038] Table 3 Performance test results of application examples Carbon accounting was performed on the corresponding use cases, and the results are shown in Table 4.

[0039] Table 4. Carbon accounting results from application examples Performance Analysis: The recycled micro-powder additives treated with NaHCO3 solution for synergistic carbonization (Examples 1-3) differ fundamentally from the uncarbonized recycled cement micro-powder (comparative example) in phase composition and chemical activity, and this difference exhibits a regular variation with the intensification of carbonization parameters. As shown in Table 1, the comparative example contains only 10.1% naturally carbonized calcite, lacks the aragonite phase, and has Si and Al leaching amounts of 769.0387 ppm and 253.2119 ppm, respectively, indicating low chemical activity. In contrast, in Examples 1-3, with the gradual intensification of parameters such as sodium bicarbonate concentration, CO2 introduction rate, and carbonization time, the calcite content increased from 22.5% to 37.8%, and the aragonite phase (content 2.5%-10.5%) was generated. This result confirms that Na... + With HCO3 - Synergistic effect: Na⁺ promotes Ca through charge shielding effect 2+ Release, HCO3 - Maintaining alkalinity and supplying carbonate ions accelerated the formation and crystal structure regulation of calcium carbonate crystals. Simultaneously, the leaching amounts of Si and Al in the examples were significantly increased, with ΔSi increasing from 84.97% to 125.01% and ΔAl from 124.92% to 165.01%, while the leaching amount of Ca decreased from 183.9360 ppm to 108.0252%. This indicates that the Si-O-Ca bonds in the CSH gel were effectively weakened during carbonation, and the decalcified gel was reconstructed into a highly active amorphous phase rich in silicon and aluminum, while Ca... 2+It combines with carbonate ions to form stable calcium carbonate crystals, which lays the core foundation for improving the performance of subsequent cementitious materials.

[0040] When the carbonized recycled micro powder additive of Example 2 and the uncarbonized micro powder of the comparative example were applied to alkali-activated concrete at dosages of 10%-60%, the mechanical properties showed significant differences, and NCRP (silicon-aluminum activated synergistic carbonized recycled micro powder) exhibited excellent high dosage compatibility. As shown in Table 3, the compressive strength and flexural modulus of the NCRP group were consistently higher than those of the comparative example with the same dosage, exhibiting a pattern of "gradual increase from 10% to 40% dosage, peak at 40% and slight decrease at 60%": at 10% dosage, the compressive strength of the NCRP group was 50.54 MPa, an increase of 4.8% compared to the comparative example's 48.22 MPa; at 30% dosage, the strength increased to 52.92 MPa, an increase of 15.0% compared to the comparative example's 46.00 MPa; at 40% dosage, the performance was optimal, with a compressive strength of 56.27 MPa and a flexural modulus of 26.1 GPa, representing increases of 38.5% and 13.6% respectively compared to the comparative example; even at a high dosage of 60%, the strength of the NCRP group still reached 53.82 MPa, 1.65 times that of the comparative example's 32.56 MPa. The core reason for this result is that the calcite and aragonite crystals in NCRP can fill the pores inside the cementing system and reduce the porosity. At the same time, the highly active amorphous phase rich in silica and aluminum can undergo secondary reactions with the components in the cementing material to form a dense and strongly bonded CASH gel matrix. In contrast, the uncarbonized micropowder in the comparative proportion has low activity and no filling or reaction enhancement effect. As the dosage increases, the mechanical properties of the system will continue to deteriorate. This highlights the activation value of the synergistic carbonization technology of this invention for regenerated micropowder, and breaks through the industry pain point that the performance of traditional regenerated micropowder will decline significantly after the dosage exceeds 30%.

[0041] The introduction of NCRP can comprehensively improve the durability of cementitious materials, and it can still maintain excellent long-term service stability even at high dosages, which is in stark contrast to the deterioration trend of the uncarbonized micro-powder in the comparative example. Looking at the durability performance indicators in Table 3, in terms of impermeability, the pressurized water penetration depth of the NCRP group is lower than that of the comparative example at the same dosage. At a 40% dosage, the penetration depth is only 3.5 mm, a 36.4% reduction compared to the 5.5 mm of the comparative example; at a 60% dosage, it is 3.7 mm, a 45.6% reduction compared to the 6.8 mm of the comparative example. This is attributed to the dense microstructure formed by NCRP reducing the water seepage channels. Regarding chloride ion penetration protection, the rapid chloride ion penetration of the NCRP group is significantly lower than that of the comparative example. At a 40% dosage, it reaches 942C, achieving a "very low" level, and remains around 200C at dosages from 10% to 60%. The NCRP content was below 0°C, while the comparative example, with a 60% dosing, reached 245°C, entering the "medium" permeability level. The dense structure effectively blocked the chloride ion migration path. In terms of carbonation resistance, the accelerated carbonation depth of the NCRP group after 28 days was smaller than that of the comparative example. At a 40% dosing, the depth was 21.08 mm, which was 25.4% lower than the comparative example's 28.26 mm. This is because the calcium carbonate crystals contained in NCRP itself can hinder CO2 diffusion, and the dense matrix reduces gas permeation channels. At the same time, the strength after carbonation not only did not decrease but actually increased, further verifying the effect of NCRP on improving the long-term stability of cementitious materials.

[0042] The synergistic carbonization technology of this invention not only achieves high-value utilization of recycled micropowder but also possesses significant low-carbon and environmentally friendly advantages. Through the synergistic effect of carbon fixation and performance enhancement, it reduces the environmental impact of cementitious materials. As shown in Table 4, the carbon accounting data indicates that the NCRP group exhibits negative carbon dioxide emissions from the micropowder additive due to CO2 fixation during the carbonization process, and the higher the dosage, the greater the carbon fixation: 10% dosage results in 5.62 kg / m³ of carbon fixation. 3 40% admixture, carbon sequestration 11.22 kg / m³ 3 60% admixture results in 16.83 kg / mHCO3 carbon fixation. -This resulted in a significantly lower Global Warming Potential (GWP) for the NCRP group compared to the comparative example. At a 40% dosage, the GWP was 127.59 kg CO2 / kg, an 8.1% reduction compared to the comparative example's 138.81 kg CO2 / kg. More importantly, the NCRP group demonstrated a clear advantage in Carbon Efficiency Index (CI, carbon emissions per unit intensity): at a 40% dosage, the CI was only 2.27 kg CO2 / MPa, far lower than the comparative example's 3.42 kg CO2 / MPa; at a 60% dosage, the CI was 2.22 kg CO2 / MPa, while the comparative example had risen to 4.19 kg CO2 / MPa. These results demonstrate that this invention not only reduces the environmental pressure of solid waste disposal by utilizing high dosages of construction solid waste, but also reduces carbon emissions throughout the entire life cycle of building materials through carbonization and carbon sequestration. Furthermore, it reduces carbon consumption per unit intensity through performance improvements, achieving a triple synergy of "solid waste resource utilization, high-performance materials, and low environmental impact," aligning with the "dual carbon" goals and green development needs of the construction industry.

[0043] As can be seen from the data in Tables 1 and 2-3, the core advantage of this invention lies in the use of Na + With HCO3 - The synergistic carbonization mechanism achieves a breakthrough across the entire chain, encompassing "product structure optimization, enhanced chemical activity, improved application performance, and improved environmental benefits." Uncarbonized recycled cement powder (comparative example) has low activity and a single phase, limiting its use in cementitious materials to filler, with higher dosages resulting in greater negative impacts. In contrast, synergistically carbonized NCRP, through the dual effects of physical filling by calcium carbonate crystals and chemical activation by the silica-alumina-rich amorphous phase, addresses the performance limitations of traditional recycled powders while achieving CO2 fixation and utilization. Within a dosage range of 10%-60%, NCRP not only continuously improves the compressive strength and flexural modulus of cementitious materials but also comprehensively optimizes durability properties such as impermeability, chloride ion penetration resistance, and carbonation resistance, while reducing GWP and CI. Especially at a 40% dosage, it achieves the optimal balance between mechanical properties, durability, and environmental benefits, fully demonstrating the technological innovation and practical application value of this invention in the field of high-value and low-carbon utilization of construction solid waste.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-aluminum activation synergistic carbonization regeneration micro powder additive, characterized in that, Includes the following steps: (1) At room temperature, recycled cement powder is added to sodium bicarbonate aqueous solution and stirred to form a suspension system; (2) CO2 is introduced into the suspension system under stirring to carry out wet carbonization reaction; (3) After carbonization, the solid is separated by centrifugation and dried to obtain a silicon-aluminum activation synergistic carbonization regeneration micro powder additive.

2. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, The recycled cement powder in (1) is obtained from waste concrete, waste mortar, or solid waste from building demolition after crushing, grading, and sieving, and has a specific surface area ≥980m². 2 / kg.

3. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, In (1), the recycled cement powder and sodium bicarbonate aqueous solution are in a solid-liquid ratio of 1:3-5, where the unit of solid-liquid ratio is g / ml; the concentration of sodium bicarbonate in the sodium bicarbonate aqueous solution is 0.05-3mol / L; and the pH of the suspension system is 12.7-12.

8.

4. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, In step (2), CO2 is introduced through gas introduction, solution saturation, pressure release, or any combination thereof; wherein the purity of CO2 gas is ≥99.99%.

5. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, In step (2), the CO2 is introduced at a rate of 0.1-0.5 mL / min / g via gas; the wet carbonization reaction time is 40-80 min.

6. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, In the wet carbonization reaction described in (2), Na... + The charge shielding effect weakens Si-O-Ca bonding in CSH gels and promotes Ca2+ bonding. 2+ Release; HCO3 - Maintaining the alkalinity of the solution and providing carbonate ions accelerates the carbonation reaction kinetics.

7. The preparation method of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 1, characterized in that, The silicon-aluminum activation synergistic carbonization regeneration micro powder additive in (3) includes a calcium carbonate phase formed by calcite, aragonite or a combination thereof.

8. The preparation method of the silicon-aluminum activation synergistic carbonization regeneration micro powder additive according to claim 1, characterized in that, The silicon-aluminum activated synergistic carbonization regenerated micro powder additive in (3) has a reduced Ca content and increased Si and Al chemical activity after wet carbonization.

9. A silicon-aluminum activation synergistic carbonization regeneration micro powder additive, prepared by the preparation method described in any one of claims 1-8.

10. The application of the silicon-aluminum activation synergistic carbonization regenerated micro powder additive according to claim 9 in cementitious materials, characterized in that, The cementitious material is a cement-based material or an alkali-activated cementitious material; the dosage of the silicon-aluminum activated synergistic carbonization regenerated micro powder additive in the cementitious material is 10-60%.

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