A structure and method for improving the interfacial bonding performance of concrete repair by carbonation

Abstract

This invention discloses a structure and method for improving the interfacial bonding performance of concrete repair through carbonation. The method includes a concrete substrate to be repaired, a cement-based repair material layer containing a carbon-fixing carrier, and a regular cement-based repair material layer. The carbon-fixing carrier layer is located between the concrete substrate and the regular cement-based repair material layer. The carbon-fixing carrier in the cement-based repair material is a porous carbon-supported aggregate encapsulated with carbon dioxide. The encapsulation film dissolves in water or alkaline environments, and the pressure of the encapsulated carbon dioxide is 0.2-5 MPa. The repair material layer on the surface to be repaired contains a carbon-fixing carrier, facilitating the release of carbon dioxide to the interfacial transition zone. This process improves the interfacial bonding while consuming carbon dioxide waste. Carbon dioxide reacts with calcium hydroxide enriched at the repair interface to generate calcium carbonate. This process consumes the calcium hydroxide enriched at the interface, preventing preferential orientation of calcium hydroxide enrichment and achieving a dense interface. This results in improved interfacial bonding performance.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a structure and method for improving the bonding performance of concrete repair interfaces through carbonation. Background Technology

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

[0003] Concrete building structures may experience surface cracking, crazing, and color inconsistencies during use, requiring repair. Concrete repair typically involves removing the damaged concrete, cleaning it, and then filling it with a concrete repair agent. The repair interface is a weak point in the repair system; calcium hydroxide tends to accumulate and preferentially orient in this area, leading to a loose and porous interface transition zone and a weak interface.

[0004] Currently, most methods to improve interface performance involve roughening the surface to enhance mechanical interlocking force, a method that improves mechanical interlocking force on a macroscopic scale. Another method increases the bonding area to improve mechanical interlocking force, such as the gradient repair method and structure based on optimizing the pore structure of the transition zone at the repair interface (2023118038943). This method uses a first-gradient repair material and a second-gradient repair material, after fluidized fusion treatment, to solidify in a single step, achieving low interface porosity. This increases the bonding area between the repair material and the existing concrete, enhancing mechanical interlocking force. No roughening treatment is required on the repair surface, significantly improving the bonding performance of the repair interface and ensuring the full utilization of the repair material's performance. However, these methods cannot improve the bonding strength of the interface layer, offering limited improvement to the interface layer's performance.

[0005] To improve the microscale, the hydration of the repair material can be controlled, thereby improving the preferred orientation of strong calcium oxide in the interfacial transition zone. For example, adding silica fume and calcium hydroxide to the repair material can react to form calcium silicate gel, reducing the preferred orientation of calcium hydroxide at the repair interface and eliminating the loose and porous phenomenon at the calcium hydroxide-rich interface. This process requires the introduction of modifying components for the repair material, such as carbonizing the repair surface before pouring the repair material. Although this method can improve interfacial bonding performance, its essence is based on the increase in the structural strength of the concrete matrix through carbonization, and it cannot affect the hydration process of the repair material in the vicinity of the repair surface. If the area or volume of the concrete matrix at the repair site is large, it is impossible to provide a carbon dioxide atmosphere for carbonization. Moreover, using external carbon dioxide or other carbonization repair systems for carbonization repair is limited by the permeability of carbon dioxide; the interior of the repair system interface cannot be reached by carbon dioxide, so the carbonization area is limited, and it is also impossible to improve the bonding performance of the repair interface. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a structure and method for improving the interfacial bonding performance of concrete repair by carbonation.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] In a first aspect, the present invention provides a structure for improving the bonding performance of concrete repair interface by carbonation, comprising a concrete substrate to be repaired, a cement-based repair material layer containing a carbon fixation carrier, and a common cement-based repair material layer, wherein the cement-based repair material layer containing a carbon fixation carrier is located between the concrete substrate to be repaired and the common cement-based repair material layer.

[0009] The carbon carrier in the cement-based repair material containing carbon fixation carrier is a porous carbon aggregate encapsulated with carbon dioxide. The encapsulation film dissolves in water or alkaline environments, and the pressure of the encapsulated carbon dioxide is 0.2-5 MPa.

[0010] Secondly, the present invention provides a method for improving the interfacial bonding performance of concrete repair by carbonation, comprising the following steps:

[0011] Clean the concrete surface to be repaired;

[0012] A porous carbon aggregate encapsulated with carbon dioxide is prepared. The encapsulation film dissolves in water or alkaline environments, and the pressure of the encapsulated carbon dioxide is 0.2-5 MPa.

[0013] Porous carbon-supported aggregate is laid on the surface to be repaired, and then a layer of cement slurry is poured to obtain the first repair layer;

[0014] Alternatively, porous carbon-loaded aggregate can be prepared into a cement-based repair material and then laid on the concrete surface to be repaired to obtain the first repair layer.

[0015] Then, pour concrete repair material onto the surface of the first repair layer, and allow it to cure.

[0016] After the repair material is poured, the aggregate containing carbon dioxide is distributed near the repair interface. As the pouring is completed and the hydration reaction proceeds, the encapsulation film of the carbon fixation carrier dissolves, opening the channel for gas exchange between the carbon fixation carrier and the external environment. The water in the capillary pores of the cement-based repair material is consumed, providing a channel for the escape of carbon dioxide from the aggregate. Because the aggregate is close to the repair interface and the carbon dioxide pressure is relatively high, the carbon dioxide can escape through the cement-based repair material in the interface area to reach the microstructure of the concrete surface to be repaired.

[0017] The reaction mechanism is as follows: The substances reacted with carbon dioxide mainly consist of unhydrated cement particles and calcium hydroxide, a hydration product of calcium silicate. The reaction between carbon dioxide and calcium silicate involves two steps: carbon dioxide dissolves in water to form carbonic acid, which then reacts with calcium silicate to produce calcium carbonate and hydrated calcium silicate gel. The hydrated calcium silicate gel further carbonizes, transforming into calcium carbonate and silica gel.

[0018] The repaired concrete surface has been cured. The repaired surface contains alkaline substances such as calcium hydroxide and hydrated calcium silicate gel, which react with carbon dioxide to produce calcium carbonate and silica gel, filling the pores and cracks of the concrete repaired surface. The dense structure is beneficial to improving the interfacial bonding performance.

[0019] The carbonization process described above affects the interfacial bonding performance. The carbonized microstructure of the repair material and the concrete matrix surface in the interfacial area is dense, and the mechanical properties of the material itself are improved. Since the entire process consumes calcium hydroxide near the repair interface area, it overcomes the disadvantage of calcium hydroxide in the interface area being easy to accumulate and preferentially oriented, and improves the loose and porous phenomenon and weak interface in the interfacial transition area.

[0020] Because existing technologies include self-healing aggregates, which encapsulate liquid repair agents (such as ammonium bicarbonate solution, ammonium carbamate solution, etc.), the inventors attempted to use this type of aggregate encapsulated with liquid repair agents during the experiment. However, the interface repair effect was poor. The reasons are as follows: the water in the liquid repair agent encapsulated in the aggregate will be lost, and the liquid viscosity is high. The internal pressure of the repair agent is low, and the diffusion channel path is relatively narrow, resulting in limited diffusion ability. It cannot reach the microstructure of the concrete surface to be repaired, and thus cannot effectively improve the interface bonding performance.

[0021] In some embodiments, the pressure of the encapsulated carbon dioxide is 0.2-3 MPa. The relatively high pressure of the encapsulated carbon dioxide facilitates its diffusion during curing, enabling carbonization of the interface region and improving the overall bonding strength of the interface region.

[0022] In some embodiments, the method for cleaning the concrete surface to be repaired is water cleaning or air blowing. This achieves the purpose of removing surface impurities and dust, facilitating the penetration of repair materials into the microstructure of the repair surface, and allowing carbon dioxide to diffuse into the microstructure.

[0023] In some embodiments, the encapsulation film is a PVA film. The thickness of the encapsulation film is adjusted according to the pressure of the encapsulated carbon dioxide.

[0024] In some embodiments, the porous carbon-supported aggregate is activated carbon, ceramsite, or cenospheres, with a porosity of not less than 18%.

[0025] Preferably, the porous carbon-supported aggregate has a particle size of 5-15 mm.

[0026] In some embodiments, the material composition of the first repair layer is: 300-560 parts cement, 120-220 parts water, 0-280 parts sand, and 1400-1900 parts porous carbonaceous aggregate.

[0027] Preferably, the thickness of the first repair layer is 4-7 times the maximum particle size of the porous carbon-supported aggregate.

[0028] Preferably, the concrete repair material consists of: 460-820 parts cement, 180-330 parts water, 100-400 parts sand, and 700-1500 parts aggregate.

[0029] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0030] (1) The repair material layer on the concrete surface to be repaired contains a carbon fixation carrier, which can release carbon dioxide to the interface transition zone. The carbon dioxide reacts with the calcium hydroxide enriched at the repair interface to generate calcium carbonate. This process consumes the calcium hydroxide enriched at the interface, avoids the preferential orientation of calcium hydroxide enrichment, and achieves a dense interface effect. It improves the adhesion of the repair interface while consuming carbon dioxide waste.

[0031] (2) No additional hydration-regulating components are introduced into the repair material, which avoids the impact on other properties of the repair material, such as the hydration performance of cement-based materials after mixing. The carbonation reaction does not require external equipment assistance and is suitable for large-scale on-site repair construction. The carbonation process not only affects the structure of the concrete matrix being repaired, but also affects the hydration of the repair material near the repair area, which is beneficial to improving the interfacial bonding strength. Attached Figure Description

[0032] 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.

[0033] Figure 1 This is a flowchart illustrating how carbonization enhances the bonding performance of the repair interface in this invention.

[0034] Figure 2 This is a construction schematic diagram of Embodiment 1 of the present invention;

[0035] Figure 3 This is a construction schematic diagram of Embodiment 2 of the present invention. Detailed Implementation

[0036] 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.

[0037] The present invention will be further described below with reference to the embodiments.

[0038] Example 1

[0039] Clean the repaired surface with clean water to remove impurities, dust, and debris.

[0040] Carbon fixation carrier aggregate encapsulation: The carbon fixation carrier uses porous ceramsite aggregate with a particle size of 8-12 mm. The porous aggregate is dried in a vacuum drying oven at 60℃. The porous aggregate is then placed in a sealed container filled with carbon dioxide at a pressure of 0.9 MPa. A stirring device is placed in the sealed container to ensure sufficient contact between the porous aggregate and the gas in the sealed container, quickly achieving dynamic equilibrium between the gas inside and outside the aggregate. The stirring time is 12 hours. Then, the carbon fixation carrier is encapsulated to cut off the exchange of gas between the carrier and the outside environment. The encapsulation film needs to react with water or an alkaline environment. The encapsulation film is a PVA film, sprayed with an 8% PVA solution.

[0041] Finally, the encapsulated carbon carrier is removed and used as an independent, sealed carbon storage medium to prepare cement-based repair materials.

[0042] like Figure 2 As shown, the spatial relationship between the carbon fixation carrier and the repair interface is designed by pouring cement slurry on the repair surface, pressing the prepared carbon fixation carrier aggregate into the repair surface, and then pouring other repair materials, so that the carbon fixation carrier aggregate is as close to the interface as possible to facilitate the diffusion of carbon dioxide to the interface in the later stage.

[0043] Porous carrier aggregate is pressed onto the repair surface, and then cement-based repair mortar is poured to form the first repair layer, which is 50mm thick. This repair layer directly contacts the repair interface. Then, the mixed ordinary aggregate concrete is placed on the first repair layer to finally form the repair material system structure.

[0044] The material composition is as follows:

[0045] The first repair layer consists of 390 parts cement, 180 parts water, 2600 parts sand, and 1600 parts aggregate.

[0046] Ordinary aggregate concrete consists of 620 parts cement, 230 parts water, 360 parts sand, and 890 parts aggregate.

[0047] The bonding strength of the repair interface and the microhardness of the transition zone of the repair interface were tested at different ages.

[0048] The control group followed the same steps as in Example 1, but the difference was that the porous aggregate was replaced with ordinary aggregate, and there was no carbon sequestration step.

[0049] The results showed that the tensile bond strength at the interface of Example 1 and the control group was 3.2 MPa and 2.6 MPa, respectively, indicating that the present invention improved the interfacial bonding performance by 23%. The microhardness of the transition zone at the interface of Example 1 and the control group was 66 MPa and 45 MPa, respectively, indicating that the present invention improved the interfacial bonding performance by 47%, thus proving the feasibility of the method.

[0050] Example 2

[0051] Blow air to clean the repaired surface and remove impurities, dust, and debris.

[0052] Carbon fixation carrier aggregate encapsulation: The carbon fixation carrier is selected from porous activated carbon aggregate with a particle size of 6-10 mm. The porous aggregate is dried in a vacuum drying oven at 50℃. The porous aggregate is then placed in a sealed container filled with carbon dioxide at a pressure of 0.6 MPa. A stirring device is placed in the sealed container to ensure sufficient contact between the porous aggregate and the gas in the sealed container, quickly achieving dynamic equilibrium between the gas inside and outside the aggregate. The stirring time is 18 hours. Then, the carbon fixation carrier is encapsulated to cut off the exchange of gas between the carrier and the outside environment. The encapsulation film needs to react with water or an alkaline environment. The encapsulation film is a PVA film, sprayed with a 6% PVA solution.

[0053] Finally, the encapsulated carbon carrier is removed and used as an independent, sealed carbon storage medium to prepare cement-based repair materials.

[0054] like Figure 3 As shown, the repair material for the first repair layer is a cement-based repair material prepared by mixing a carbon carrier as aggregate. The repair material for the first repair layer is placed upside down on the surface of the concrete substrate to obtain the first repair layer, which has a thickness of 50 mm. Then, the mixed ordinary aggregate concrete is placed on the repair material for the first repair layer to finally form the repair material system structure.

[0055] The material composition is as follows:

[0056] The materials for the first repair layer consist of 620 parts water, 240 parts sand, 230 parts aggregate, and 900 parts cement.

[0057] Ordinary aggregate concrete consists of 600 parts water, 2400 parts sand, 190 parts aggregate, and 1000 parts aggregate.

[0058] The bonding strength of the repair interface and the microhardness of the transition zone of the repair interface were tested at different ages.

[0059] The control group followed the same steps as in Example 2, but the porous aggregate was replaced with ordinary aggregate, and the carbon sequestration step was omitted.

[0060] The results showed that the tensile bond strength at the interface of Example 1 and the control group was 2.4 MPa and 1.8 MPa, respectively, indicating that the present invention improved the interfacial bonding performance by 33%. The microhardness of the transition zone at the interface of Example 1 and the control group was 49 MPa and 38 MPa, respectively, indicating that the present invention improved the interfacial bonding performance by 29%, thus proving the feasibility of the method.

[0061] 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 structure for enhancing the interfacial bond performance of concrete repairs with carbonation, characterized by: It includes a concrete substrate to be repaired, a cement-based repair material layer containing a carbon fixation carrier, and a cement-based repair material layer, wherein the cement-based repair material layer containing a carbon fixation carrier is located between the concrete substrate to be repaired and the cement-based repair material layer. The carbon carrier in the cement-based repair material containing carbon carrier is a porous carbon aggregate encapsulated with carbon dioxide. The encapsulation film dissolves in water or alkaline environments, and the pressure of the encapsulated carbon dioxide is 0.6-5 MPa.

2. A method of carbonation to enhance the interfacial bond performance of a concrete repair, characterized by: Using the structure of claim 1, the method comprises the following steps: Clean the concrete surface to be repaired; A porous carbon aggregate encapsulated with carbon dioxide is prepared. The encapsulation film dissolves in water or alkaline environments, and the pressure of the encapsulated carbon dioxide is 0.6-5 MPa. Porous carbon-supported aggregate is laid on the surface to be repaired, and then a layer of cement slurry is poured to obtain the first repair layer; Alternatively, porous carbon-loaded aggregate can be prepared into a cement-based repair material and then laid on the concrete surface to be repaired to obtain the first repair layer. Then, pour concrete repair material onto the surface of the first repair layer, and allow it to cure.

3. The structure for improving the interfacial bond performance of concrete repair according to claim 1 or the method for improving the interfacial bond performance of concrete repair according to claim 2, characterized in that: The pressure of the encapsulated carbon dioxide is 0.6-3 MPa.

4. The method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The methods for cleaning the concrete surface to be repaired are cleaning with water or blowing air.

5. The structure for improving the interfacial bonding performance of concrete repair by carbonation according to claim 1, or the method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The encapsulation film is a PVA film.

6. The structure for improving the interfacial bonding performance of concrete repair by carbonation according to claim 1, or the method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The porous carbon-supported aggregate is activated carbon, ceramsite, or cenospheres, with a porosity of not less than 18%.

7. The structure for improving the interfacial bonding performance of concrete repair by carbonation according to claim 1, or the method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The porous carbon-supported aggregate has a particle size of 5-15 mm.

8. The method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The material composition of the first repair layer is: 300-560 parts cement, 120-220 parts water, 0-280 parts sand, and 1400-1900 parts porous carbonaceous aggregate.

9. The method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The thickness of the first repair layer is 4-7 times the maximum particle size of the porous carbon-loaded aggregate.

10. The method for improving the interfacial bonding performance of concrete repair by carbonation according to claim 2, characterized in that: The composition of concrete repair materials is as follows: 460-820 parts cement, 180-330 parts water, 100-400 parts sand, and 700-1500 parts aggregate.

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