Active cementitious material based on aluminum-carbon synergistic reaction and preparation method of active cementitious material

Abstract

The invention discloses an active cementing material based on aluminum-carbon synergistic reaction and a preparation method thereof. The preparation method comprises the following steps: mixing a calcium-based solid waste material with a regulating agent solution to form mixed slurry; introducing industrial tail gas containing CO2 into the mixed slurry, reacting for 30-180 minutes at the temperature of 25-100 DEG C, carrying out carbonization treatment, and then carrying out solid-liquid separation and drying dehydration to obtain an active carbonate admixture; mixing the active carbonate admixture with a volcanic ash material and ordinary Portland cement, and adding water to prepare an active cementing material with aluminum-carbon synergistic reaction; aiming at the problems in the prior art, an aluminum-carbon synergistic reaction is introduced to realize synchronous proceeding of carbonate mineralization and aluminate activation, a compact and continuous skeleton structure is constructed, the early and later compressive strength of the cementing material is remarkably improved, and meanwhile, resource utilization of industrial solid wastes such as the steel slag, the red mud and the waste concrete can also be realized.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an active cementitious material based on aluminum-carbon synergistic reaction and its preparation method. Background Technology

[0002] my country consumes a large amount of ordinary Portland cement (OPC) every year. Its production process requires calcining limestone at high temperatures and consuming fossil fuels. The carbon dioxide emissions per unit of clinker are as high as 0.8 tons / ton, resulting in huge total carbon emissions from the building materials industry, which has become a prominent contradiction in achieving the "dual carbon" target.

[0003] To reduce cement clinker usage and carbon emissions, researchers have explored using industrial solid wastes such as steel slag, blast furnace slag, red mud, and fly ash as alternative cementitious materials, forming cementitious materials primarily based on an OPC-aluminosilicate binary system. While these systems can maintain basic performance at certain substitution ratios, excessively high substitution rates often lead to decreased early strength, poor volume stability, and insufficient durability due to insufficient release of solid waste activity and uneven formation of hydration products.

[0004] To further reduce OPC usage, researchers have attempted to introduce limestone powder into the system to improve performance through the filling effect and potential reactivity of carbonates, and to some extent, increase the system's low-carbon level. However, this ternary composite system of "OPC-aluminosilicate-limestone" suffers from significant reaction incoordination: the aluminate phase dissolves and reacts rapidly in the reaction system, while the carbonate phase dissolves and participates in the reaction relatively slowly, lacking synchronicity and making it difficult to generate stable carbonate hydration products in a timely manner. This results in a discontinuous system framework and insufficient gel network construction, affecting early strength development and limiting efficient CO2 encapsulation.

[0005] It is evident that while existing ternary alternatives can partially reduce carbon emissions, their performance and low-carbon effects are significantly limited due to the asynchronous aluminum-carbon reaction. There is an urgent need for a new type of cementitious material system that can achieve a synergistic aluminum-carbon reaction. Summary of the Invention

[0006] To address the aforementioned issues, this invention introduces an aluminum-carbon synergistic reaction to achieve simultaneous carbonate mineralization and aluminate activation, constructing a dense and continuous skeletal structure. This significantly improves the early and later compressive strength of cementitious materials, while also enabling the resource utilization of industrial solid wastes such as steel slag, red mud, and waste concrete.

[0007] To achieve the above objectives, the following technical solution is adopted: A method for preparing an active cementitious material based on the synergistic reaction of aluminum and carbon includes the following steps: (1) Mix calcium-based solid waste materials with a regulator solution to form a mixed slurry; (2) Introduce industrial tail gas containing CO2 into the mixed slurry and react it at 25~100℃ for 30~180 min for carbonation treatment. Then, separate the solid and liquid, dry and dehydrate to obtain active carbonate admixture. (3) The active carbonate admixture is mixed with volcanic ash material and ordinary silicate cement, and water is added to prepare an active cementitious material with aluminum-carbon synergistic reaction.

[0008] According to the above scheme, the regulator used in step (1) is selected from one or any combination of ammonium nitrate, ammonium chloride, sodium silicate, potassium silicate, sodium carbonate, sodium bicarbonate, potassium carbonate, aluminum hydroxide, polyacrylamide, triethanolamine, polyacrylic acid, and polycarboxylate superplasticizer.

[0009] According to the above scheme, the concentration of the regulator solution in step (1) is 0.1~0.5 mol / L; the weight ratio of the mixed slurry liquid to solid is (0.5~20):1.

[0010] According to the above scheme, the main mineral composition of the calcium-based solid waste material in step (1) includes one or more of calcium silicate, calcium aluminate, calcium iron aluminate, calcium sulfoaluminate and calcium fluoroaluminate; specifically, it is one or any mixture of steel slag, waste concrete sand powder, red mud, fly ash, slag powder, and carbide slag powder, with a particle size of 100~400 mesh.

[0011] According to the above scheme, the CO2-containing industrial exhaust gas in step (2) comes from the steel industry, cement industry, power industry, chemical industry, glass industry or ceramic industry.

[0012] According to the above scheme, the CO2 concentration in the industrial exhaust gas containing CO2 in step (2) is not less than 5%, and the ventilation rate is 0.05~1.0 L / min / g solid.

[0013] According to the above scheme, the moisture content of the active carbonate admixture after drying and dehydration in step (2) is 10wt% to 20wt%.

[0014] According to the above scheme, the calcium carbonate crystal form in the active carbonate admixture obtained in step (2) includes one or more of calcite, aragonite, spheroidal aragonite and amorphous calcium carbonate.

[0015] According to the above scheme, the volcanic ash material in step (3) is one or any mixture of fly ash, slag powder, metakaolin, and volcanic ash rock powder.

[0016] According to the above scheme, the mass ratio of active carbonate admixture, volcanic ash material and ordinary silicate cement in step (3) is (10-40): (20-60): (20-60).

[0017] According to the above scheme, step (3) yields an active gelling material with a liquid-to-solid ratio of 0.3 to 0.6.

[0018] This invention mixes cement-based solid waste materials with a regulator solution and utilizes industrial tail gas containing CO2 to carry out a solid-liquid carbonation reaction under ambient temperature conditions. After solid-liquid separation, an active carbonate admixture is obtained. The regulator solution used in this invention is a key factor in achieving the synergistic aluminum-carbon reaction. Its mechanism of action lies in promoting the reaction of calcium-based solid waste with Ca through ion regulation and pH buffering. 2+ Dissolution and migration; at the same time, the regulator can induce calcium carbonate crystal transformation and promote the synergistic formation of aluminate and CASH composite gel, thereby constructing a dense and continuous framework structure.

[0019] Subsequently, the activated carbonate admixture was combined with pozzolanic materials and ordinary silicate cement, and water was added to prepare an activated cementitious material with a synergistic aluminum-carbon reaction. The activated carbonate admixture obtained by CO2 solid-liquid carbonation treatment in this invention has a high specific surface area and lattice defect characteristics, which significantly improves the reactivity of the carbonate component. In the subsequent composite process, the admixture forms a dynamic coupling reaction with the aluminate phase and the active pozzolanic components: in the early stage, the dissolved Ca... 2+ With CO3 2- Rapidly combines to form nanoscale calcium carbonate crystal nuclei, promoting Al(OH)₂ formation. 4- and SiO3 2- On its surface, synergistic adsorption and gelation generate aluminocarbonate and CASH co-gels, achieving simultaneous aluminate activation and carbonate mineralization. In the middle and later stages, the residual moderately active carbonates further react with aluminates, continuously generating aluminocarbonate phases that fill pores and enhance the continuity of the framework structure. Thus, the activated carbonate admixture effectively overcomes the problem of "asynchronous aluminum-carbon reaction" in traditional systems, forming a synergistic reaction channel and significantly improving the early strength, structural density, and carbon fixation efficiency of the material.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Improved mechanical properties: Through the synergistic effect of active carbonate and aluminate gel, a dense and continuous skeleton structure is constructed, which significantly improves the early and late compressive strength of the material. 2) Improve carbon sequestration capacity: Solid-liquid carbonization treatment using industrial tail gas containing CO2 can efficiently seal CO2, significantly increasing the carbon sequestration capacity of a single material. 3) Promote resource utilization: It has realized the synergistic utilization of various carbonate and aluminate industrial solid wastes such as steel slag, marble powder, red mud, and waste concrete powder, which has reduced the amount of ordinary silicate cement clinker used and reduced energy consumption and carbon emissions. Attached Figure Description

[0021] Figure 1 Thermogravimetric analysis of the hydration products in Example 5. Detailed Implementation

[0022] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. It should be noted that those skilled in the art should understand that the described embodiments are only for illustrating this application and are not intended to limit the scope of protection of this application. All equivalent substitutions, modifications or combinations made within the scope defined by this application should be covered within the scope of protection of this application.

[0023] The calcium-based solid waste materials and volcanic ash materials used in this invention are both derived from industrially available solid waste resources and undergo pretreatment to ensure the reproducibility of experiments and production. Specifically: Steel slag powder: derived from converter steel slag produced by the converter steelmaking process of a certain steel enterprise, after magnetic separation to remove iron, crushing, drying and grinding to a specific surface area of ​​approximately 420 m². 2 / kg. Its main chemical components (wt%) are: CaO 42.6%, SiO2 13.8%, Al2O3 3.9%, Fe2O3 20.5%, MgO 8.7%, MnO 4.5%, SO3 0.3%.

[0024] Waste concrete powder: derived from waste concrete from building demolition, processed through crushing, impurity removal, and ball milling, with a particle size of less than 200 mesh. Its main components are: CaO 48.2%, SiO2 24.7%, Al2O3 6.2%, Fe2O3 2.3%, MgO 1.9%, Na2O+K2O 0.8%.

[0025] Calcium carbide slag powder: Derived from calcium carbide slag, a byproduct of acetylene production, it is used after drying, crushing, and sieving. Its main components are: Ca(OH)3 72.4%, CaCO3 18.3%, SiO2 3.5%, Al2O3 1.6%, Fe2O3 0.7%.

[0026] Volcanic ash material (slag powder): Selected from blast furnace slag produced by a steel company, dried and ground to a specific surface area of ​​approximately 450 m². 2 / kg. Its chemical composition (wt%) is: CaO 37.5%, SiO2 34.2%, Al2O3 13.7%, MgO 8.9%, Fe2O3 1.2%, SO3 0.4%.

[0027] All the aforementioned materials, after testing, conform to the typical compositional distribution of general industrial by-product solid waste, demonstrating availability and representativeness. This invention does not use any specific brand or patent-limited commercial raw materials; the experimental results are universally applicable and scalable. Unless otherwise specified, all other components were obtained commercially.

[0028] Example 1 Step 1: Prepare ammonium chloride solution. Weigh ammonium chloride and dissolve it in water to prepare a 0.05 mol / L regulator solution; Step 2: Raw material mixing. Add the steel slag powder and the ammonium chloride solution obtained in Step 1 to a mixing device at a liquid-to-solid mass ratio of 10:1, and stir until a uniform slurry is formed. Step 3: Carbonization treatment. The mixture obtained in Step 2 is placed in a carbonization device, and industrial tail gas containing CO2 with a CO2 concentration of 10% is introduced. The mixture is reacted and carbonized at 25 °C for 60 min to obtain the carbonized product. Step 4: Solid-liquid separation. The carbonized product obtained in Step 3 is dehydrated through a solid-liquid separation unit to obtain an admixture containing active carbonates; Step 5: Composite preparation. The active carbonate admixture obtained in Step 4 is added to the mixing device along with slag powder and ordinary Portland cement (OPC) in a mass ratio of 20:40:40. At the same time, an appropriate amount of water is added to adjust the liquid-solid ratio to 0.4. The mixture is stirred evenly to obtain a composite slurry. Step 6: Molding and curing. Pour the mixed slurry obtained in Step 5 into a 100 mm × 100 mm × 100 mm cube mold, vibrate it on a vibratory compactor for about 2 minutes to remove air bubbles, then wrap the mold with a polyvinyl chloride film and place it in a standard curing chamber (temperature 20±2 ℃, relative humidity ≥95%) for 24 h. Step 7: Demolding and Continued Curing. Demold the test block after curing for 24 hours in Step 6, wrap it with PVC film, and place it back in the standard curing chamber for continued curing for 28 days to finally obtain the target test block.

[0029] Example 2 Step 1: Prepare sodium carbonate solution. Weigh sodium carbonate and dissolve it in water to prepare a 0.1 mol / L regulator solution; Step 2: Raw material mixing. Add the waste concrete powder and the sodium carbonate solution obtained in Step 1 to a mixing device at a liquid-to-solid mass ratio of 5:1, and mix thoroughly to form a slurry. Step 3: Carbonization treatment. The mixture obtained in Step 2 is placed in a carbonization device, and power plant tail gas with a CO2 concentration of 12% is introduced. Carbonization is carried out at 35 °C for 90 min. Step 4: Solid-liquid separation. The carbonized product obtained in Step 3 is dehydrated to obtain an admixture containing active carbonates; Step 5: Composite preparation. The active carbonate admixture obtained in Step 4 is mixed with fly ash and OPC in a mass ratio of 25:35:40 and a liquid-solid ratio of 0.35. The mixture is stirred evenly to obtain a slurry. Step 6: Molding and curing. Pour the mixed slurry obtained in Step 5 into a 100 mm × 100 mm × 100 mm mold, vibrate for 2 min, wrap with film, and place in a standard curing chamber for 24 h; Step 7: Demolding and Continued Curing. Demold the test block obtained in Step 6 and wrap it with film again. Place it in a standard curing chamber for 28 days to obtain the target test block.

[0030] Example 3 Step 1: Prepare sodium silicate solution. Weigh sodium silicate and dissolve it in water to prepare a 0.2 mol / L regulator solution; Step 2: Raw material mixing. The red mud powder and the sodium silicate solution obtained in Step 1 are mixed evenly at a liquid-to-solid mass ratio of 8:1 to form a slurry; Step 3: Carbonization treatment. The slurry obtained in Step 2 is placed in a carbonization device, and chemical tail gas with a CO2 concentration of 20% is introduced. Carbonization is carried out at 45 ℃ for 60 min with a stirring rate of 500 rpm. Step 4: Solid-liquid separation. The carbonized product obtained in Step 3 is dehydrated to obtain an admixture containing active carbonates; Step 5: Compound preparation. Mix the admixture obtained in Step 4 with slag powder and OPC in a mass ratio of 30:30:40 and a liquid-solid ratio of 0.4, and stir until homogeneous; Step 6: Molding and curing. Pour the mixed slurry obtained in Step 5 into the mold, vibrate for 2 minutes, wrap with a film, and place in a standard curing chamber for 24 hours; Step 7: Demolding and Continued Curing. Demold the test block obtained in Step 6 and wrap it with film again. Place it in a standard curing chamber for 28 days to obtain the target test block.

[0031] Example 4 Step 1: Prepare the composite solution. Weigh out sodium bicarbonate and triethanolamine, dissolve them in water, and prepare a 0.05 mol / L regulator solution; Step 2: Raw material mixing. The steel slag powder and the solution obtained in Step 1 are mixed evenly at a liquid-to-solid mass ratio of 4:1 to form a slurry. Step 3: Carbonization treatment. The mixture obtained in Step 2 is placed in a carbonization device, and glass factory exhaust gas with a CO2 concentration of 8% is introduced. Carbonization is carried out at 25 ℃ for 120 min with a stirring rate of 600 rpm. Step 4: Solid-liquid separation. The carbonized product obtained in Step 3 is dehydrated to obtain an admixture containing active carbonates; Step 5: Composite preparation. The admixture obtained in Step 4 is mixed with fly ash and OPC in a mass ratio of 20:30:50 and a liquid-to-solid ratio of 0.38. The mixture is stirred evenly to obtain a slurry. Step 6: Molding and Curing. Pour the mixed slurry obtained in Step 5 into the mold, compact it, wrap it with a film, and place it in a standard curing chamber for 24 hours. Step 7: Demolding and Continued Curing. Demold the test block obtained in Step 6 and wrap it with film again. Place it in a standard curing chamber for 28 days to obtain the target test block.

[0032] Example 5 Step 1: Prepare sodium aluminate solution. Weigh sodium aluminate and dissolve it in water to prepare a 0.05 mol / L regulator solution; Step 2: Raw material mixing. Add the calcium carbide slag powder and the sodium aluminate solution obtained in Step 1 to the mixing device at a liquid-to-solid mass ratio of 6:1, and stir evenly to form a mixed slurry; Step 3: Carbonation treatment. The mixture obtained in Step 2 is placed in a carbonation device, and cement kiln exhaust gas with a CO2 concentration of 25% is introduced. Carbonation is carried out at 30 ℃ for 60 min with a stirring rate of 400 rpm. Step 4: Solid-liquid separation. The carbonization product obtained in step 3 is dehydrated through a solid-liquid separation unit to obtain an admixture containing active calcium carbonate; Step 5: Composite preparation. The active carbonate admixture obtained in Step 4 is added to the mixing device along with metakaolin and ordinary Portland cement (OPC) in a mass ratio of 25:35:40. At the same time, an appropriate amount of water is added to adjust the liquid-solid ratio to 0.36. The mixture is stirred evenly to obtain a composite slurry. Step 6: Molding and curing. Pour the mixed slurry obtained in Step 5 into a 100 mm × 100 mm × 100 mm mold, vibrate it on a vibratory compactor for about 2 minutes to remove air bubbles, then wrap the mold with a polyvinyl chloride film and place it in a standard curing chamber (temperature 20±2 ℃, relative humidity ≥95%) for 24 h. Step 7: Demolding and Continued Curing. Demold the test block after curing for 24 hours in Step 6, wrap it with PVC film, and place it back in the standard curing chamber for continued curing for 3–28 days to obtain the target test block.

[0033] Appendix Figure 1The thermogravimetric analysis (TG-DTG) curves of the hydration products of the active cementitious material obtained in this embodiment at 28 days of age are shown. As can be seen from the figure, a significant weight loss peak appears in the range of approximately 30–100 °C, corresponding to the removal of adsorbed water and some bound water in the CSH and CASH gels; the weight loss peak in the range of 100–200 °C is mainly attributed to the decomposition of aluminocarbonates (such as Mc, Hc, etc.); the significant weight loss peak in the range of 350–450 °C corresponds to the decomposition of calcium hydroxide (CH); and the broad, gradual weight loss peak in the range of 600–800 °C is related to the decomposition of calcium carbonate (CaCO3) to generate CaO and CO2. These thermogravimetric analysis results indicate that both carbonate and aluminate hydration products exist in the system, verifying the occurrence of a synergistic aluminum-carbon reaction and providing a structural basis for improving the material's strength and carbon impregnation capability.

[0034] Comparative Example 1 Repeat Example 1, but replace the ammonium chloride solution in step 2 with the same mass of water, leaving everything else unchanged.

[0035] Comparative Example 2 Repeat Example 1, except that the active carbonate admixture in step 5 is replaced with the same mass of steel slag powder, and everything else remains the same.

[0036] The performance of the test blocks obtained from the above embodiments and comparative examples is shown in Table 1.

[0037] Table 1

[0038] As shown in Table 1, the 3-day compressive strength of the embodiments of the present invention ranged from 14.8 to 18.8 MPa, and the 28-day compressive strength ranged from 47.2 to 52.8 MPa, which were significantly higher than those of the comparative samples. Among them, Examples 3 and 4 showed the highest strength, indicating that different regulator systems could effectively improve the early reaction activity and structural compactness. In contrast, the strengths of Comparative Examples 1 and 2 were significantly lower, with 3-day strengths of only 12 MPa and 8.8 MPa, and 28-day strengths of 38.4 MPa and 31.2 MPa, respectively, which were about 20% to 40% lower than the average values ​​of the embodiments. This indicates that the regulator and the carbonization activation process played a key role in improving the performance of the system.

[0039] Comparative Example 1 omitted the regulator solution and used only water for carbonization treatment, resulting in a decrease in Ca in the calcium-based solid waste. 2+ Al 3+ Insufficient dissolution of active ions limits the carbonization reaction, resulting in coarse and unevenly distributed CaCO3 crystals that are difficult to react synchronously with the aluminate phase. Consequently, the amount of CASH gel formed is small and the structure is loose, thus significantly reducing its strength.

[0040] Comparative Example 2 did not use active carbonate admixtures, but instead used uncarbonized raw steel slag powder. The system lacked highly active CaCO3 crystal nuclei and aluminate seeds. The aluminate and carbonate reacted asynchronously. The early hydration products were mainly a small amount of CSH gel and incompletely reacted calcium aluminate phase. The high porosity and discontinuous skeleton led to a further reduction in mechanical properties.

[0041] In contrast, the embodiments of the present invention, through the action of a regulator during the carbonation stage, form an active carbonate admixture rich in defects and with a high specific surface area, which improves the Ca... 2+ and CO3 2- The reactivity of the aluminate phase further promotes the synergistic reaction between the aluminate and carbonate phases during subsequent hydration, generating a large amount of aluminocarbonate and CASH composite gel, which significantly improves the continuity and density of the microstructure. Therefore, the active carbonate admixture prepared in this invention can effectively overcome the technical bottleneck of "asynchronous aluminum-carbon reaction" in traditional systems, achieving synchronous reaction and structural synergy, thereby significantly improving the early and late compressive strength of cementitious materials.

Claims

1. A method for preparing an active cementitious material based on aluminum-carbon synergistic reaction, characterized in that... Includes the following steps: (1) Mix calcium-based solid waste materials with a regulator solution to form a mixed slurry; (2) Introduce industrial tail gas containing CO2 into the mixed slurry and react it at 25~100℃ for 30~180 min for carbonation treatment. Then, separate the solid and liquid, dry and dehydrate to obtain active carbonate admixture. (3) The active carbonate admixture is mixed with volcanic ash material and ordinary silicate cement, and water is added to prepare an active cementitious material with aluminum-carbon synergistic reaction.

2. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... The regulator used in step (1) is selected from one or any combination of ammonium nitrate, ammonium chloride, sodium silicate, potassium silicate, sodium carbonate, sodium bicarbonate, potassium carbonate, aluminum hydroxide, polyacrylamide, triethanolamine, polyacrylic acid, and polycarboxylate superplasticizer.

3. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... In step (1), the concentration of the regulator solution is 0.1~0.5 mol / L; the weight ratio of the mixed slurry to solids is (0.5~20):

1.

4. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... The calcium-based solid waste material mentioned in step (1) is one or any mixture of steel slag, waste concrete sand powder, red mud, fly ash, slag powder, and carbide slag powder, with a particle size of 100~400 mesh.

5. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... The CO2-containing industrial exhaust gas mentioned in step (2) comes from the steel industry, cement industry, power industry, chemical industry, glass industry or ceramic industry, with a CO2 concentration of not less than 5% and a ventilation rate of 0.05~1.0 L / min / g solid.

6. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... Step (2) The moisture content of the dried and dehydrated active carbonate admixture is 10wt% to 20wt%, and the calcium carbonate crystal form includes one or more of calcite, aragonite, spheroidal aragonite and amorphous calcium carbonate.

7. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... The volcanic ash material mentioned in step (3) is one or any mixture of fly ash, slag powder, metakaolin, and volcanic ash rock powder.

8. The method for preparing the active cementitious material based on the synergistic reaction of aluminum and carbon as described in claim 1, characterized in that... In step (3), the mass ratio of active carbonate admixture, volcanic ash material and ordinary silicate cement is (10-40): (20-60): (20-60).

9. The preparation method of the active cementitious material based on aluminum-carbon synergistic reaction as described in claim 1, characterized in that... Step (3) yields an active cementitious material with a liquid-to-solid ratio of 0.3 to 0.

6.

10. An active cementitious material based on aluminum-carbon synergistic reaction, characterized in that... It is prepared by the method for preparing active cementitious materials based on aluminum-carbon synergistic reaction as described in any one of claims 1-9.

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