A method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement

Abstract

The present invention relates to a method for preparing a high-performance cement-based material by using carbonized high-belite sulphoaluminate cement. The method mainly comprises the following steps: (1) mixing the high-belite sulphoaluminate cement with water, and introducing a precise dose of carbon dioxide during the stirring process, wherein the median particle size of the high-belite sulphoaluminate cement is ≤18 μm, the dicalcium silicate content is 35-45 wt.%, and the anhydrous calcium sulphoaluminate content is 20-40 wt.%. (2) adding silicate cement and water to the cement slurry stirred in step (1) and stirring evenly, wherein the calcium oxide content of the silicate cement is 68-75 wt.%. The method promotes the reaction of the high-belite sulphoaluminate cement by using carbon dioxide and mixes it into the silicate cement, thereby strengthening the cement hydration product hydrated calcium silicate gel (C-S-H), and simultaneously generating hydrated calcium silicate aluminate gel (C-A-S-H) with a longer chain length, thereby achieving the effect of improving the performance of the cement-based material and sealing carbon dioxide.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing cement-based composite materials by utilizing carbon dioxide, and particularly relates to a method for preparing high-performance cement-based materials by utilizing carbonized high-belite sulphoaluminate cement. Background Art

[0002] Cement, one of the world's most widely used building materials, emits significant amounts of carbon dioxide (CO2) into the environment through its production. The production of one ton of cement clinker produces approximately 0.98 tons of CO2. However, it is estimated that approximately 43% of CO2 emissions from cement production can be offset through carbonation throughout its lifecycle. Therefore, accelerated carbonation curing of cementitious materials has become an effective way to sequester CO2. During carbonation curing, CO2 dissolved in the pore solution reacts with calcium silicate hydrate (CSH) and calcium hydroxide (CH) in the cementitious material to form calcium carbonate (CaCO3), which fills the pores, or reacts with aluminum to form hemicarbonate (MC), which improves the early strength of the cementitious material. However, because CO2 can only contact the surface of the cementitious material, the degree of carbonation is low. Increasing the CO2 pressure or carbonation time incurs additional energy consumption, and this carbonation curing method requires large-scale curing equipment. Therefore, it is limited to prefabricated cementitious products.

[0003] In order to further expand the scope of application and increase carbonization efficiency, some scholars have proposed injecting a certain amount of carbon dioxide during the mixing process of cement-based materials. However, there are the following problems: (1) it can only improve the early strength, and the later strength improvement is not obvious; (2) when stirring in a closed mixing instrument, when more than 1wt.% of the mass of the cement-based material is injected with carbon dioxide, the working performance is significantly reduced, resulting in a large number of pores in the sample and thus reduced strength; (3) because carbon dioxide can only be injected within a few minutes of stirring, the carbon dioxide absorption efficiency of the cement-based material is low. Usually, the carbon dioxide absorption of cement-based material products in 28 days is 4-5wt.%. Currently disclosed related patents, such as CN114919068A, disclose a method for preparing cement-based foam materials using carbon dioxide. By adding foam water with a foaming agent to cement-based dry materials and stirring, and continuously spraying a precise amount of carbon dioxide gas, the 28-day compressive strength is increased by 42% to 5.63MPa. Although the strength improvement is large, the final strength is still low. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a cement-based material with high carbon dioxide absorption efficiency and high strength throughout the process, which is convenient, efficient, and easy to mass-produce.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a high-performance cement-based material using carbonized high-belite sulphoaluminate cement comprises the following steps:

[0007] Step 1: placing high belite sulphoaluminate cement accounting for 5-50 wt.% of the total cementitious material weight and water in a stirring container, stirring at a low speed for 90-120 seconds, and then stirring at a high speed, and continuously introducing carbon dioxide gas accounting for 0.05-6 wt.% of the total cementitious material weight during the stirring process, wherein the weight ratio of the water to the high belite sulphoaluminate cement is 0.2-2, and the particle size D of the high belite sulphoaluminate cement is 0. 10 The median particle size is 2.2-3.0 μm, D 50 ≤18μm, D 90 The particle size is 68-75 μm, the content of dicalcium silicate is 35-45 wt.%, and the content of anhydrous calcium sulfoaluminate is 20-40 wt.%.

[0008] Step 2: Add 50-95 wt.% of Portland cement and water to the cement paste stirred in step 1 and stir evenly, wherein the weight ratio of water to Portland cement is 0.3-0.8.

[0009] In the aforementioned method for preparing a high-performance cement-based material using carbonized high-belite sulfoaluminate cement, the stirring container in step 1 is a sealed stirrer, the low-speed stirring speed is 60-90 r / min, the high-speed stirring speed is 320-400 r / min, the continuous introduction time of carbon dioxide gas during the high-speed stirring process should be equal to 3 / 5 to 4 / 5 of the total high-speed stirring time, and the carbon dioxide gas concentration is 10-99.9%.

[0010] In the aforementioned method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement, the chemical component calcium oxide content of the silicate cement in step 2 is 68-75 wt.%.

[0011] In the aforementioned method for preparing a high-performance cement-based material using carbonized high-belite sulphoaluminate cement, the cumulative water consumption of steps one and two and the water-cement ratio of the total cementitious material are 0.4-0.6. When the mass ratio of the high-belite sulphoaluminate cement in step one to the silicate cement in step two is ≥0.68, and the mass of the carbon dioxide gas introduced in step one is ≥3 wt.%, the weight ratio of water to the high-belite sulphoaluminate cement in step one should be ≥0.5.

[0012] After the high-performance cement-based material prepared by using carbonized high-belite sulphoaluminate cement is prepared, it is placed in an environment with a relative humidity of ≥95% and a temperature of 20±2° C. for standard curing.

[0013] Beneficial effects

[0014] Compared to existing technologies, the present invention utilizes high-belite sulfoaluminate cement, a fast-reaction cement, by first mixing it with water to rapidly hydrate and produce large quantities of hydrated aluminum hydroxide gel (AH3) and ettringite (Aft). Because the hydrated Aft product is susceptible to carbonation, the continuous introduction of carbon dioxide during the mixing process effectively increases CO2 absorption efficiency. Within just a few minutes of stirring, the sample's 28-day CO2 absorption reaches approximately 7.3 wt.%, compared to the approximately 4-5 wt.% of Portland cement samples. This represents an increase of approximately 46-82%, significantly improving CO2 absorption efficiency. Furthermore, the rapid reaction of Aft with CO2 promotes hydration and carbonation, generating more AH3 and calcium carbonate (CaCO3), and potentially generating additional Aft, potentially increasing early strength by approximately 37%.

[0015] Injecting carbon dioxide during the mixing process of high-belite sulfoaluminate cement effectively stimulates the latent activity of silicate minerals in the cement. The addition of carbon dioxide to the Portland cement strengthens the CSH gel and, in the later stages of curing, generates longer-chain CASH gel. This can increase the later compressive strength by approximately 14 MPa, raising the concrete strength by approximately three grades. Furthermore, high-belite sulfoaluminate cement, due to its lower calcination temperature than Portland cement, is less expensive and can reduce carbon dioxide emissions by approximately 30-50%. Using this method to prepare cement-based materials (e.g., concrete) offers advantages such as ease of operation and scalability, as well as indirect reductions in cement-related carbon dioxide emissions. Furthermore, due to the increased strength, the amount of cement and other cementitious materials used can be significantly reduced while maintaining the same strength grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Thermogravimetric analysis diagrams of Example 1 and Example 2 are shown.

[0017] Figure 2 The following is a Fourier transform infrared absorption spectrum analysis diagram of Example 1 and its comparative example. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to specific implementation cases, but this is not intended to limit the present invention.

[0019] Example 1, a method for preparing a high-performance cement-based material using carbonized high-belite sulphoaluminate cement, comprising the following steps:

[0020] Step 1: High-belite sulphoaluminate cement accounting for 10 wt.% of the total cementitious material weight is mixed with water in a weight ratio of 1:1, and stirred at a low speed of 90 r / min for 90 seconds, and then at a high speed of 400 r / min for 150 seconds. During the high-speed stirring process, carbon dioxide gas accounting for 3 wt.% of the total cementitious material weight is continuously introduced.

[0021] Step 2: Add 90 wt.% of Portland cement and water in a weight ratio of 3:1 to the high-belite sulphoaluminate cement slurry that has been carbonized and stirred in step 1, first stirring at a low speed of 90 r / min for 150 s, and then stirring at a high speed of 400 r / min for 60 s.

[0022] Step 3: Place the mixed slurry obtained in step 2 into a 40×40×40 mm mold and vibrate for 1 minute to form the mixture. The mixture is then placed in a standard environment with a relative humidity of ≥95% and a temperature of 20±2°C for curing.

[0023] The median particle size (D 50 ) is 17 μm, D 10 2.4μm, D 90 The particle size is 70 μm, and the content of dicalcium silicate as a mineral component is 40 wt.%, and the content of anhydrous calcium sulfoaluminate is 31 wt.%.

[0024] In the step 1, the concentration of carbon dioxide gas is 99.9%, and the continuous introduction time of the gas is 108 s.

[0025] The chemical component calcium oxide content in the silicate cement in step 2 is 70 wt.%.

[0026] The water-cement ratio of the cumulative water consumption of step 1 and step 2 to the total cementitious material is 0.4.

[0027] To verify the technical effects of the present invention, Comparative Examples 1-1, 1-2, and 1-3 were prepared. The main difference between the preparation process of Comparative Example 1-1 and Example 1 is that the cementitious material is 100% Portland cement, and the water-cement ratio is 0.4. According to step 2, the cementitious material is stirred at a low speed of 90 r / min for 150 seconds, then at a high speed of 400 r / min for 60 seconds, and then the standard curing process of step 3 is carried out.

[0028] The main difference between the preparation process of Comparative Example 1-2 and Example 1 is that the cementitious material is 10 wt.% high-belite sulfoaluminate cement and 90 wt.% Portland cement. The dry material is first stirred at a low speed of 90 r / min for 30 seconds, and then, under a water-cement ratio of 0.4, according to step 2, stirred at a low speed of 90 r / min for 150 seconds, and then stirred at a high speed of 400 r / min for 60 seconds, and then the standard curing of step 3 is carried out.

[0029] The main difference between the preparation process of Comparative Examples 1-3 and Example 1 is that the cementitious material is 10 wt.% high-belite sulfoaluminate cement and 90 wt.% Portland cement. The dry material is first stirred at a low speed of 90 r / min for 30 seconds, and then stirred at a low speed of 90 r / min for 150 seconds under a water-cement ratio of 0.4, and then stirred at a high speed of 400 r / min for 150 seconds. During the high-speed stirring process, carbon dioxide gas accounting for 3 wt.% of the total weight of the cementitious material is continuously introduced. The gas is continuously introduced for 108 seconds, and then step 3 standard curing is performed.

[0030] Compressive strength tests were conducted on Example 1, Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3 in accordance with GB / T 17671-1999, "Test Method for Cement Mortar Strength (ISO Method)." The test results are shown in Table 1. The results indicate that Example 1 exhibited a 30% increase in one-day compressive strength and a 12.1 MPa increase in 28-day compressive strength relative to Comparative Example 1-1 (100% Portland cement). The one-day compressive strength of Example 1 increased by approximately 37% and a 14.0 MPa increase in 28-day compressive strength relative to Comparative Example 1-3.

[0031] Table 1 Compressive strength test results of Example 1 and its comparative example (MPa)

[0032]

[0033]

[0034] Thermogravimetric analysis of the 28-day sample of Example 1 was performed to calculate the carbon dioxide absorption, as shown in FIG. Figure 1 As shown in the figure, this preparation method, with only a few minutes of stirring, can achieve a 28-day carbon dioxide absorption rate of 7.3 wt.%, compared to the 28-day carbon dioxide absorption rate of Portland cement samples of 4-5 wt.%, an increase of 46-82%.

[0035] In addition, the 28-day samples of Example 1, Comparative Example 1-1, Comparative Example 1-2 and Comparative Example 1-3 were subjected to Fourier transform infrared absorption spectroscopy analysis. Figure 2As shown in the figure, this stirring method can produce chain-length CASH gel, which effectively ensures the compressive strength of the sample for 28 days.

[0036] Example 2. The main difference between this example and Example 1 is that: in step 1, 40 wt.% of the high belite sulphoaluminate cement accounting for the total weight of the cementitious material is mixed with water in a weight ratio of 4:1. In addition, 0.3 wt.% of the total weight of the cementitious material is continuously introduced into the mixture during the stirring process; in step 2, 60 wt.% of the Portland cement accounting for the total weight of the cementitious material and water are added in a weight ratio of 2:1 to the high belite sulphoaluminate cement slurry that has been carbonized and stirred in step 1.

[0037] To verify the technical effects of the present invention, Comparative Example 2 was prepared. The difference between the preparation process of Comparative Example 2 and Example 2 is that the cementitious material in Comparative Example 2 is 40 wt.% high-belite sulfoaluminate cement and 60 wt.% Portland cement. The dry material is first stirred at a low speed of 90 r / min for 30 seconds, and then, at a water-cement ratio of 0.4, the mixture is stirred at a low speed of 90 r / min for 150 seconds and then at a high speed of 400 r / min for 60 seconds according to step 2, and then the standard curing of step 3 is carried out.

[0038] Compressive strength tests were conducted on Example 2 and Comparative Example 2 with reference to GB / T 17671-1999, "Test Method for Strength of Cement Mortar (ISO Method)." The test results are shown in Table 2. The results show that the compressive strength of Example 2 increased by 32% at one day and by 6.1 MPa at 28 days relative to that of Comparative Example 2, and by 12.8 MPa at 28 days relative to that of 100% Portland cement (Comparative Example 1-1).

[0039] Table 2 Compressive strength test results of Example 2 and Comparative Example 2 (MPa)

[0040] Group 1 day 7 days 28 days Example 2 23.3 61.2 82.1 Comparative Example 2 17.7 51.0 76.0

[0041] Thermogravimetric analysis of the 28-day sample of Example 2 was performed to calculate the carbon dioxide absorption, as shown in FIG. Figure 1 As shown in the figure, the sample prepared by this method can absorb up to 5.98 wt.% of carbon dioxide in 28 days after only a few minutes of stirring.

Claims

1. A method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement, characterized in that: The following steps are involved: Step 1: First, high belite sulphoaluminate cement accounting for 5-50 wt.% of the total cementitious material weight and water are placed in a stirring container and mixed and stirred for 90-120 seconds, and then stirred at high speed, and carbon dioxide gas accounting for 0.05-6 wt.% of the total cementitious material weight is continuously introduced during the stirring process, the weight ratio of the water to the high belite sulphoaluminate cement is 0.2-2, and the particle size D of the high belite sulphoaluminate cement is 0. 10 The median particle size is 2.2-3.0 μm, D 50 ≤18μm, D 90 68-75 μm, dicalcium silicate content 35-45 wt.%, anhydrous calcium sulfoaluminate content 20-40 wt.%; Step 2: Add 50-95 wt.% of Portland cement and water to the cement paste stirred in step 1 and stir evenly, wherein the weight ratio of water to Portland cement is 0.3-0.

8.

2. The method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement according to claim 1, characterized in that: The stirring container in the step 1 is a sealed stirrer, the high-speed stirring speed is 320-400 r / min, and the continuous introduction time of carbon dioxide gas during the high-speed stirring process should be equal to 3 / 5 to 4 / 5 of the total high-speed stirring time.

3. The method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement according to claim 1, characterized in that: The silicate cement in step 2 has a calcium oxide content of 68-75 wt.%.

4. The method for preparing high-performance cement-based materials using carbonized high-belite sulphoaluminate cement according to claim 1, characterized in that: The water-cement ratio of the cumulative water consumption of step 1 and step 2 to the total cementitious material is 0.4-0.6, when the mass ratio of the high belite sulphoaluminate cement in step 1 to the silicate cement in step 2 is ≥ 0.68, and the mass of carbon dioxide gas introduced in step 1 is ≥3wt.%, the weight ratio of water to high-belite sulphoaluminate cement in step 1 should be ≥0.5.

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