A method for preparing a cement-based material for carbon sequestration and utilization

Abstract

The application discloses a preparation method of cement-based material for carbon sequestration and utilization, and comprises the following steps: drying a porous aggregate carrier compatible with the cement-based material, then placing the porous aggregate carrier in a sealed space and replacing air in the sealed space with carbon dioxide; stirring the porous aggregate carrier to make it fully contact and adsorb the carbon dioxide; after the adsorption is completed, spraying a sealing liquid on the porous aggregate carrier to form a sealing film on the surface of the porous aggregate carrier, wherein the sealing film is dissolved in water or in an alkaline environment of the concrete; mixing various components of the concrete, and finally adding the sealed porous aggregate carrier, mixing, and then pouring and forming; during the hydration process of the concrete component, the sealing film on the surface of the porous aggregate carrier is dissolved in water or in the alkaline environment of the concrete, carbon dioxide is released, and the concrete component is maintained. During the carbonation process of the concrete from the inside to the outside, the concrete inside presents a scattered and blooming carbonation mode, cement-based material around the porous carrier has the maximum probability of contacting the carbon dioxide, and therefore the interface transition zone of the porous carrier is reinforced.

Description

Technical Field

[0001] This invention belongs to the field of cement-based materials, specifically relating to a method for preparing cement-based materials that realize carbon sequestration and utilization. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Carbon dioxide is a major cause of global warming, and the cement industry accounts for approximately 8% of global anthropogenic carbon dioxide emissions. As infrastructure construction continues, the demand for cement continues to increase, while cement production itself generates carbon dioxide. Using low-carbon raw materials or supplementary cementitious materials, as well as carbon capture and utilization technologies, can reduce emissions from the cement industry. Preparing zero-carbon concrete requires consuming the carbon dioxide generated during concrete preparation.

[0004] Efficiently utilizing carbon dioxide is a feasible approach to achieving low-carbon preparation of cement-based materials. The traditional method involves carbonation curing of concrete after molding. However, in this method, the capillaries are filled with free water, and carbon dioxide is blocked on the surface of the concrete, preventing carbonation at areas far from the surface. If carbon dioxide curing is performed after pre-curing, the capillary water is consumed, providing a channel for carbon dioxide to enter the interior of the concrete, resulting in a significant increase in curing depth compared to the previous method. Even so, for large concrete components, the carbon dioxide curing depth is insufficient to reach the innermost part of the concrete, and the carbon dioxide curing process requires a sealed container filled with carbon dioxide, making it impractical for the carbonation curing of large-volume concrete components. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing cement-based materials to realize carbon sequestration and utilization.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for preparing a cement-based material for carbon sequestration and utilization includes the following steps:

[0008] The porous aggregate carrier, which is compatible with cement-based materials, is dried, and then the porous aggregate carrier is placed in a closed space, where the air is replaced with carbon dioxide.

[0009] Stir the porous aggregate carrier to ensure it is in full contact with and adsorbs carbon dioxide.

[0010] After adsorption is complete, a sealing liquid is sprayed onto the porous aggregate carrier to form an encapsulation film on the surface of the porous aggregate carrier. The encapsulation film dissolves in water or in the alkaline environment of concrete.

[0011] After the various components of the concrete are mixed evenly, the encapsulated porous aggregate carrier is added, mixed, and then poured into shape.

[0012] During the hydration process of concrete components, the encapsulation film on the surface of the porous aggregate carrier dissolves in water or in the alkaline environment of the concrete, releasing carbon dioxide and thus curing the concrete components.

[0013] In the preparation of concrete materials, the encapsulating aggregate is added last to prevent premature addition, which could damage the encapsulating film or cause it to dissolve and fail during the mixing process.

[0014] The mixed concrete is poured into shape. As the concrete hydrates, the porous aggregate encapsulation membrane dissolves in water or in the alkaline environment of the concrete, releasing carbon dioxide. As the water in the capillaries within the concrete is consumed, the carbon dioxide curing channels open, thus curing the concrete. Because the concrete is relatively enclosed from the outside environment, the carbon dioxide exists inside the concrete until it is completely consumed. The entire carbon dioxide release and curing process requires no external equipment, eliminating the need for the sealed containers required in traditional carbon dioxide curing processes. This is particularly suitable for the carbonation curing of large-volume concrete components.

[0015] Carbonation is a spontaneous, inside-out curing process that occurs after concrete pouring. The start time and area of ​​curing can be designed. For larger curing areas, the aggregate content, density, and spacing between aggregates can be adjusted. The carbonation mechanism is as follows: unhydrated cement particles and calcium hydroxide (a hydration product of calcium silicate) react with carbon dioxide. Carbon dioxide dissolves in water to form carbonic acid. This carbonic acid reacts rapidly with calcium silicate in liquid form to form calcium carbonate and hydrated calcium silicate gel. The hydrated calcium silicate gel further carbonates to become calcium carbonate and silica gel. This process makes the concrete microstructure denser.

[0016] After the carbonation process is completed, the microstructure around the porous aggregate carrier is carbonized, the hardness increases, the arch shell structure with the porous aggregate carrier as its outline is strengthened, the macroscopic mechanical properties of concrete are improved, and the purpose of turning waste into treasure is achieved.

[0017] In some embodiments, the porous aggregate carrier is selected from lightweight aggregates, ceramsite, cenospheres, zeolite, or hollow microspheres.

[0018] Preferably, the porosity of the porous aggregate carrier is not less than 20%.

[0019] Preferably, the porous aggregate carrier has a particle size of 6-20 mm. The porous aggregate carrier acts as aggregate in concrete, possessing porous characteristics. The cavities within the aggregate serve as storage spaces for carbon dioxide. The particle size of the aggregate is determined according to the design of the target concrete.

[0020] In some embodiments, the porous aggregate carrier is dried at a temperature of 60-80°C for 6-24 hours. The purpose of drying is to remove impurities, such as water, from the porous aggregate and to clear the space to allow carbon dioxide to enter.

[0021] In some embodiments, the pressure of carbon dioxide introduced into the sealed space is 0.2-6 MPa. The relatively high pressure of the sealed carbon dioxide is conducive to its diffusion, which in turn helps to improve the quality of carbonation curing of concrete components.

[0022] Preferably, the aggregate is mixed for 2-24 hours to allow the internal and external gases of the aggregate to reach a dynamic equilibrium.

[0023] In some embodiments, the sealing liquid is a PVA solution with a concentration of 6-12 wt%. PVA solution curing results in a water-soluble film, also known as a PVA (PVOH) film. This film is characterized by the transformation of an oil-liquid phase into a solid phase, and the solid phase is soluble in water or alkaline environments. Water-soluble packaging films can also be used to encapsulate carbon-loaded aggregates and prevent gas escape.

[0024] Preferably, the thickness of the encapsulation film is 1-100 μm, and more preferably 5-50 μm.

[0025] The carbon dioxide concentration sealed inside the porous carrier is the same as the carbon dioxide concentration filling the sealed container. The carbon dioxide concentration inside the encapsulated aggregate is related to the pressure resistance of the encapsulation membrane. If the concentration inside the encapsulated aggregate is high, the thickness of the encapsulation membrane needs to be thicker to withstand the pressure. Secondly, the thickness of the encapsulation membrane is related to the design of the carbon dioxide release time of the aggregate in the concrete. If the carbon dioxide release time in the concrete is to be earlier, the encapsulation membrane should be thinner. For example, if carbonation is required to begin 12 hours after concrete pouring, the thickness of the encapsulation membrane needs to be determined in advance as 10-20 μm.

[0026] After the porous aggregate carrier is sealed, the sealed container is slowly vented, and then the sealed aggregate is removed, allowing carbon dioxide to be stably sealed inside the porous aggregate. The sealed aggregate is easy to store and transport.

[0027] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0028] (1) The prepared concrete is carbonized from the inside to the outside. The carbon dioxide carbonization process does not require carbonation equipment. The carbon dioxide is sealed inside the concrete until it is completely consumed. This method is carried out after the concrete is poured, not during the mixing process, and the carbonation start time can be designed independently.

[0029] (2) During the carbonation process of concrete from the inside to the outside, the concrete exhibits a scattered flowering carbonation pattern, which is not the traditional pattern in which the concrete specimen begins to carbonize after contacting carbon dioxide on the outside. The range of internal concrete carbonization can be designed independently according to the density of aggregate placement. The cement-based materials around the porous aggregate carrier are the first to come into contact with carbon dioxide, thus strengthening the transition zone of the porous aggregate carrier interface. This process is conducive to increasing the mechanical properties of the interface zone between the porous aggregate carrier and the cement-based materials. While making efficient use of carbon dioxide, it also improves the mechanical properties of concrete.

[0030] (3) The prepared porous aggregate carrier containing carbon dioxide is easy to store and convenient to transport. After the concrete structure is completed, the sealing film dissolves in water or the alkaline environment of the concrete, and the carbon dioxide is released inside the concrete, realizing the automatic carbonization process inside the concrete without external energy consumption. Compared with the concrete prepared from the original aggregate, this method has better performance and is suitable for use on the construction site of large-scale infrastructure. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 This is a flowchart illustrating the preparation process of cement-based materials for carbon sequestration and utilization according to an embodiment of the present invention. Detailed Implementation

[0033] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] The present invention will be further described below with reference to the embodiments.

[0035] Example 1

[0036] A porous aggregate carrier compatible with cement-based materials is selected, using ceramsite with a particle size of 10-12 mm. The porous aggregate carrier is dried at 70℃ for 12 hours and then placed in a sealed container connected to a carbon dioxide cylinder. The pressure in the sealed container is reduced to below -0.04 MPa using a vacuum pump, and then carbon dioxide gas is introduced at a uniform rate until the pressure reaches 0.6 MPa.

[0037] A mortar mixing device is placed inside a sealed container. The ceramsite carrier is placed in the mixing device, the mixing device is started, and the mixing is carried out for 12 hours to allow the ceramsite to reach equilibrium in the adsorption of carbon dioxide.

[0038] Then, PVA encapsulation solution was continuously sprayed onto the surface of the ceramsite carrier until the PVA encapsulation solution uniformly encapsulated the porous carrier surface. The PVA solution concentration was 8 wt%. At this point, the carbon dioxide concentration sealed inside the porous carrier was the same as the carbon dioxide concentration filling the sealed container, with a carbon dioxide pressure of 0.6 MPa. The thickness of the encapsulation film on the surface of the ceramsite carrier was 15 μm.

[0039] When preparing concrete, the sealed porous aggregate carrier is placed in the concrete mix. The concrete mix composition is 350 parts cement, 720 parts sand, 1200 parts ceramsite (sealed porous aggregate carrier), and 200 parts water.

[0040] Performance testing: The 3-day compressive strength of concrete and the microhardness of the porous aggregate interfacial transition zone were determined; control group. The aggregates were not encapsulated, and the proportions and tests were the same.

[0041] Results analysis:

[0042] The 3-day compressive strength of the concrete in Example 1 was 39 MPa, while that of the control group was 30 MPa. The method of this invention increased the concrete strength by 30%, and the failure of the concrete changed from cracks penetrating the aggregate-cement stone interface to cracks penetrating the aggregate.

[0043] In Example 1, the microhardness of the aggregate interface transition zone was 45 MPa, while the fiber hardness of the aggregate interface transition zone in the control group was 32 MPa. The fiber hardness of the interface transition zone was increased by 40% using the method of the present invention, proving that the aggregate interface was carbonized and the strength of the cement stone was improved.

[0044] Example 2

[0045] A porous aggregate carrier compatible with cement-based materials is selected, using zeolite material with a particle size of 6-8mm. The porous aggregate carrier is dried at 90℃ for 6 hours and then placed in a sealed container filled with carbon dioxide at a pressure of 1MPa. A mortar mixing device is placed in the sealed container, and the ceramsite carrier is placed in the mixing device. The mixing device is started and stirred for 16 hours to allow the adsorption of carbon dioxide by the zeolite to reach equilibrium.

[0046] PVA encapsulation solution is continuously sprayed into the stirring device until the PVA encapsulation solution uniformly encapsulates the surface of the porous carrier. The PVA solution concentration is 10 wt%. At this point, the carbon dioxide concentration sealed inside the porous carrier is the same as the carbon dioxide concentration filling the sealed container, with a carbon dioxide pressure of 1 MPa. The thickness of the encapsulation film on the surface of the porous carrier is 20 μm.

[0047] When preparing concrete, the sealed porous carrier is placed in the concrete mixture. The concrete mix composition is 830 parts cement, 1039 parts zeolite carrier, 210 parts silica fume, 230 parts water, 156 parts steel fiber, and 24 parts polycarboxylate.

[0048] Performance testing: The compressive strength of concrete after 3 days of curing and the microhardness of the transition zone at the interface of porous aggregate were measured. The control group consisted of unencapsulated aggregate, with the same proportions and testing.

[0049] Results analysis:

[0050] The concrete compressive strength of Example 2 was 80 MPa, while that of the control group was 65 MPa. The method of this invention increased the concrete strength by 23%, and the failure of the concrete changed from cracks penetrating the aggregate-cement stone interface to cracks penetrating the aggregate.

[0051] In Example 2, the microhardness of the aggregate interface transition zone was 69 MPa, while the fiber hardness of the aggregate interface transition zone in the control group was 56 MPa. The fiber hardness of the interface transition zone increased by 23% using the method of the present invention, proving that the aggregate interface was carbonized and the strength of the cement stone was improved.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of making a cementitious material that enables carbon sequestration and utilization, characterized by: The steps include the following: The porous aggregate carrier compatible with cement-based materials is dried, and then the porous aggregate carrier is placed in a closed space, and the air in it is replaced with carbon dioxide. The pressure of the carbon dioxide introduced into the closed space is 0.2-6 MPa. Stir the porous aggregate carrier to ensure it is in full contact with and adsorbs carbon dioxide. After adsorption is complete, a sealing liquid is sprayed onto the porous aggregate carrier to form an encapsulation film on the surface of the porous aggregate carrier. The encapsulation film dissolves in water or in the alkaline environment of concrete. The sealing liquid is a PVA solution with a concentration of 6-12 wt%. After the various components of the concrete are mixed evenly, the encapsulated porous aggregate carrier is added, mixed, and then poured into shape. During the hydration process of concrete components, the encapsulation film on the surface of the porous aggregate carrier dissolves in water or in the alkaline environment of the concrete, releasing carbon dioxide and thus curing the concrete components. The thickness of the encapsulation film is 15-100 μm; The porous aggregate carrier has a particle size of 6-20 mm.

2. The method of claim 1, wherein: The porous aggregate carrier is selected from lightweight aggregates, ceramsite, cenospheres, zeolite, or hollow microspheres.

3. The method of claim 2, wherein: The porosity of the porous aggregate carrier is not less than 20%.

4. The method for preparing cement-based materials for carbon sequestration and utilization according to claim 1, characterized in that: The porous aggregate carrier is dried at a temperature of 60-80℃ for 6-24 hours.

5. The method for preparing cement-based materials for carbon sequestration and utilization according to claim 1, characterized in that: The aggregate should be mixed for 2-24 hours.

6. The method for preparing cement-based materials for carbon sequestration and utilization according to claim 1, characterized in that: The thickness of the encapsulation film is 15-50 μm.

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