Method and device for efficiently carbonizing and reinforcing recycled aggregate prefabricated part by using high-pressure saturated carbonic acid solution

Abstract

The invention relates to a method and device for efficiently carbonizing and reinforcing a recycled aggregate prefabricated part by using a high-pressure saturated carbonic acid solution, and the method comprises the following steps: placing the recycled aggregate prefabricated part into a wet carbonization box, then feeding the high-pressure saturated carbonic acid solution into the wet carbonization box to generate a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles, and carrying out carbonization treatment to obtain the recycled aggregate prefabricated part. And the reinforcement of the recycled aggregate prefabricated part is completed. Compared with the prior art, the saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is produced in a manner of releasing pressure after high-pressure saturation, and is used for carbonizing the recycled aggregate prefabricated part, so that the problems that the dissolving speed of carbon dioxide in pore liquid of the prefabricated part is low in dry-method carbonization and the utilization efficiency of carbon dioxide is low in wet-method carbonization can be solved; the migration speed of carbonic acid in pore water of the recycled aggregate prefabricated part is accelerated, and the substance exchange rate between reaction interfaces is enhanced, so that the carbonization reaction speed is accelerated, and the carbon sequestration rate is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of reinforced recycled aggregate prefabricated components, and relates to a method and device for efficiently carbonizing reinforced recycled aggregate prefabricated components by using a high-pressure saturated carbonic acid solution. Background Art

[0002] The traditional construction industry is characterized by high energy consumption and high carbon emissions. Carbon emissions from the entire construction lifecycle include emissions from building material production, construction, maintenance, demolition, and disposal. Building material production and construction waste disposal are the primary sources of carbon emissions. Therefore, the use of low-carbon methods to recycle construction waste has become a key research area for carbon reduction in the construction industry.

[0003] Mechanically crushing, cleaning, and screening construction waste to produce recycled aggregate, which can then be reused in concrete as a replacement for natural aggregate, is a primary method for treating construction waste. However, the production of recycled concrete using recycled aggregate still results in significant CO2 emissions. This is because recycled aggregate has weaker physical and mechanical properties than natural aggregate, requiring more cement to maintain its mechanical properties. Cement production, however, generates significant amounts of CO2. Compared to cement, magnesium oxide (MgO) emits less CO2 during its production process because its firing temperature, approximately 850°C, is much lower than cement's temperature of over 1450°C. Furthermore, MgO exhibits excellent carbon capture capacity, and the basic magnesium carbonate formed by hydration and carbonation possesses excellent mechanical properties. Therefore, using MgO cement, with MgO as the primary binder, to bind recycled aggregate in the production of recycled aggregate precast components can reduce CO2 emissions, promote resource recycling, and contribute to sustainable development.

[0004] When using magnesium oxide as the main cementing material to bind recycled aggregate to produce low-carbon recycled aggregate prefabricated components, two main reactions occur during the carbonization process: 1) The active substances Ca(OH)2, CSH, and unhydrated C3S in the old mortar on the surface of the recycled aggregate, C2S react with carbon dioxide to form CaCO3 and SiO2. The carbonization products fill the pores on the surface of the recycled aggregate, improving the physical and mechanical properties of the recycled aggregate; 2) The hydration product Mg(OH)2 of magnesium oxide reacts with carbon dioxide to form various basic carbonates. The production of basic magnesium carbonate effectively links the aggregate particles, forming a bond between the particles and providing the main strength of the prefabricated components. The typical reaction is shown below:

[0005] Ca(OH)2+CO2→CaCO3+H2O

[0006] (3CaO·2SiO2·3H2O)+3CO2→(3CaCO3·2SiO2·3H2O)

[0007] (3CaO·2SiO2)+3CO2+nH2O→3CaCO3+SiO2·nH2O

[0008] (2CaO·2SiO2)+2CO2+nH2O→2CaCO3+SiO2·nH2O

[0009] Mg(OH)2+CO2+2H2O→MgCO3·3H2O

[0010] 5Mg(OH)2+4CO2+H2O→(Mg)5(CO3)4(OH)2·5H2O

[0011] 5Mg(OH)2+4CO2→(Mg)5(CO3)4(OH)2·4H2O

[0012] However, due to the low concentration of carbon dioxide in the atmosphere (approximately 0.041%), the carbonation reaction rate is extremely slow. To address this, researchers have sought a variety of more efficient carbonation methods. For example, carbon dioxide gas is directly injected into the concrete mixing process (Application Publication No. CN116969710A). The carbon dioxide converts Ca(OH)2 and calcium silicate in the fresh cement paste into CaCO3 and SiO2, providing crystal nucleation sites for cement hydration products, thereby promoting cement hydration while absorbing carbon dioxide. However, due to the short injection time and relatively small amount of carbon dioxide used, the carbon sequestration capacity of the pre-carbonization method is limited. Another carbonization method is to place the recycled concrete in a carbonation box filled with gas (Application Publication Nos. CN107814502A, CN118081980A). By adjusting variables such as carbon dioxide concentration, temperature, humidity, carbonation time, and carbonation pressure, the concrete can quickly absorb carbon dioxide gas, thereby improving carbonation efficiency. This carbonization method is called dry carbonization and is the most widely used. But dry carbonization often requires a long curing time (24h-14d not etc.), because the migration speed of carbon dioxide in concrete internal micropore is slower. Latest research has found that after carbon dioxide is dissolved in water to form carbonate ion, carbonate ion can pass through concrete internal micropore by capillary action with water molecules, improves reaction rate and reaction depth, and is more feasible. Because this carbonization method needs recycled concrete to be immersed in solution, the method is referred to as wet carbonization (application publication number CN117819852A, CN112125541A), its main principle is that carbon dioxide is dispersed and injected into liquid and is dissolved to produce carbonic acid, utilizes carbonic acid and the recycled aggregate or recycled aggregate product that need carbonization to complete carbonization reaction in liquid, thus improves carbonization reaction rate.

[0013] Analysis shows that the carbonization depth of existing wet carbonization methods is limited, and it is generally difficult to achieve carbonization inside the recycled aggregate product; at the same time, its utilization rate of carbon dioxide gas is also extremely low. Since the solubility of carbon dioxide gas in liquid is limited in a normal pressure environment, in addition, existing wet carbonization equipment is mostly set in an open environment, and most of the carbon dioxide that is not dissolved in the solution directly escapes into the air.

[0014] The present invention is proposed based on this. Summary of the Invention

[0015] The purpose of the present invention is to provide a method and device for efficiently carbonizing and strengthening recycled aggregate prefabricated components using high-pressure saturated carbonic acid solution, so as to improve the carbonization rate and carbonization effect of recycled aggregate prefabricated components.

[0016] The purpose of the present invention can be achieved by the following technical solutions:

[0017] On the one hand, the present invention provides a method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution. The recycled aggregate prefabricated components are placed in a wet carbonization box, and a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is then fed into the wet carbonization box for carbonization treatment to complete the strengthening of the recycled aggregate prefabricated components.

[0018] Furthermore, the temperature of the carbonization treatment is 20±5°C, the volume ratio of the saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles to the recycled aggregate prefabricated component is greater than 5:1, and here, the pressure in the wet carbonization box is the same as the atmospheric pressure.

[0019] Furthermore, the saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is a water-based solution, which is obtained by dissolving in a high-pressure carbon dioxide atmosphere and then reducing the pressure.

[0020] Furthermore, the pressure of the carbon dioxide atmosphere in the high-pressure saturated bottle is 4-5 MPa.

[0021] Furthermore, during the carbonization process, a fresh saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is used to continuously replace the post-reaction unsaturated carbonic acid solution in the wet carbonization box.

[0022] Furthermore, the replacement frequency satisfies: 1 / 10 of the unsaturated carbonic acid solution in the wet carbonization box is replaced every 15 to 20 seconds.

[0023] Furthermore, the total time of the carbonization treatment is 15 to 60 minutes.

[0024] Furthermore, the recycled aggregate prefabricated component is prepared by the following method:

[0025] Portland cement and magnesium oxide are mixed in a mass ratio of 1:2-4 as a gelling agent, and the gelling agent is then mixed with recycled fine aggregate with a particle size of no more than 4.75 mm in a mass ratio of 1:2.5-3 as a dry material;

[0026] Add water to the evenly mixed dry material and stir, with the mass ratio of water to gelling agent being 0.5-0.6:1, then pour into a mold, vibrate to compact, scrape the surface, maintain, and demould to obtain a prefabricated component sample, which is a recycled aggregate prefabricated component.

[0027] Furthermore, the size of the recycled aggregate prefabricated component is (35-105) mm*(35-105) mm*(90-170) mm.

[0028] In a second aspect, the present invention provides a device for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution, which is used to implement the method according to the first aspect, and the device comprises:

[0029] CO2 gas source, used for providing CO2 gas;

[0030] A pressure pump, used for pressurizing the CO2 gas output from the CO2 gas source;

[0031] High-pressure saturation bottle, used to receive pressurized CO2 gas and process the matrix solution to obtain high-pressure saturated carbonic acid solution;

[0032] The wet saturation box is used to reduce the pressure of the high-pressure saturated carbonic acid solution to generate a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles and to place the recycled aggregate prefabricated components to be processed. The bottom of the box is provided with a saturated carbonic acid solution inlet connected to the liquid outlet of the high-pressure saturation bottle, and the top is provided with an unsaturated carbonic acid solution outlet that returns to the liquid inlet of the high-pressure saturation bottle.

[0033] Furthermore, a carbon dioxide escape port is provided on the top of the wet saturation box, and the carbon dioxide escape port is sequentially connected to the gas storage bag and the inlet of the pressure pump through a pipeline, so that the escaped carbon dioxide can participate in secondary carbonization.

[0034] The biggest difference between the high-pressure saturated carbonic acid solution used in the present invention and the normal-pressure saturated carbonic acid solution is that when the high-pressure saturated solution enters a normal-pressure environment, the carbon dioxide in the solution changes from a saturated state to a supersaturated state. The carbon dioxide exceeding the saturated amount will precipitate in the form of micro-nano bubbles and be present in the solution, forming a saturated carbonic acid solution rich in micro-nano carbonic acid bubbles. Compared with ordinary saturated carbonic acid solutions, due to the appearance of micro-nano carbonic acid bubbles, the material exchange rate on the reaction interface is significantly improved, further increasing the carbonization rate. The present invention replaces the saturated carbonic acid solution of a single liquid phase with a saturated carbonic acid solution rich in micro-nano carbonic acid bubbles containing a gas-liquid two-phase. The purpose of this is to utilize the disturbance of the gas-liquid two-phase at the reaction interface to increase the material exchange rate of the reaction interface, thereby breaking through the carbonization reaction rate in the normal-pressure saturated carbonic acid solution that is limited by the material exchange rate of the reaction interface.

[0035] Compared with the prior art, the present invention prepares a high-pressure saturated carbonic acid solution in a high-pressure saturation manner and inputs it into a normal-pressure wet carbonization box. Due to the sudden drop in ambient pressure, the carbon dioxide gas in the high-pressure saturated carbonic acid solution precipitates in the form of micro-nano bubbles and is stably suspended in the saturated carbonic acid solution, forming a saturated carbonic acid solution rich in micro-nano carbonic acid bubbles, which replaces the matrix solution (unsaturated carbonic acid solution) in ordinary wet carbonization. The fast migration speed of carbonic acid molecules in capillary pores is utilized to improve the carbonization depth of recycled aggregate prefabricated components. The ability of micro-nano carbonic acid bubbles to form a stable gas-liquid two-phase disturbance between the saturated carbonic acid solution and the recycled aggregate specimen is utilized to enhance the material exchange rate at the reaction interface. The high-pressure saturation method is used to improve the solubility of carbon dioxide in the matrix solution and accelerate the reaction speed. In addition, a gas storage bag is provided to recycle the escaped carbon dioxide, thereby improving the carbon dioxide utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0037] Figure 2 It is a process flow chart of the present invention;

[0038] Figure 3 The solubility of carbon dioxide in water at different temperatures and pressures shown in existing experimental data;

[0039] Description of the marks in the figure:

[0040] 1-CO2 gas source; 2-gas source valve; 3-gas booster pump; 4-booster pump valve; 5-unsaturated carbonic acid solution outlet valve; 6-unsaturated carbonic acid solution outlet; 7-carbon dioxide escape outlet; 8-wet carbonization box; 9-metal cage; 10-prefabricated component; 11-matrix solution; 12-saturated carbonic acid solution inlet; 13-carbonization box bracket; 14-agitator; 15-flow guide tube; 16-saturated carbonic acid solution outlet valve; 17-base; 18-high-pressure saturation bottle; 19-saturation bottle bracket; 20-gas storage bag; 21-gas storage bag valve. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0043] The terms "and / or", "or / and", and "and / or" used herein include any one of two or more related listed items, and also include any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND" and technical solutions connected by "logical OR".

[0044] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0045] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0046] Only certain numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0047] The temperature parameters in this application, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0048] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0049] In this application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0050] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0051] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0052] Unless otherwise stated, all formulations and tests herein took place at 25°C.

[0053] As used herein, the terms "comprise," "include," "contain," "have," "have," or other variations thereof are intended to encompass non-exclusive inclusions, and no distinction is made between these terms. The term "comprising" means that other steps and ingredients that do not affect the end result may be added. The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. As used herein, no distinction is made between the terms "efficacy," "performance," "effect," and "efficacy."

[0054] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0055] Unless otherwise specified, all steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0056] In order to improve the carbonization efficiency and carbonization effect of recycled aggregate prefabricated components, the present invention provides a device for efficiently carbonizing and strengthening recycled aggregate prefabricated components using high-pressure saturated carbonic acid solution, such as Figure 1 As shown, it includes a CO2 gas source 1, a gas source valve 2, a gas pressure pump 3, a pressure pump valve 4, a flow guide 15, a high-pressure saturation bottle 18, and a wet carbonization box 8, which are connected in sequence. The wet carbonization box 8 is also provided with a saturated carbonate solution inlet 12 (directly connected via a pipeline to a saturated carbonate solution outlet valve 16 at the bottom of the high-pressure saturation bottle 18), an unsaturated carbonate solution outlet 6, and a carbon dioxide escape port 7. The unsaturated carbonate solution outlet 6 returns to the flow guide 15 via the unsaturated carbonate solution outlet valve 5. The carbon dioxide escape port 7 is also connected via a pipeline to a gas storage bag 20, which in turn connects to the inlet of the gas pressure pump 3 via a gas storage bag valve 21. A metal cage 9 for accommodating prefabricated components 10 is provided within the wet carbonization box 8. A stirrer 14 is also provided at the bottom of the wet carbonization box 8. The wet carbonization box 8 is supported by a carbonization box bracket 13, and the high-pressure saturation bottle 18 is supported by a saturation bottle bracket 19. Together, the wet carbonization box 8 is mounted on a base 17.

[0057] The present invention will be described in more detail below with reference to specific embodiments.

[0058] Example 1:

[0059] The recycled aggregate prefabricated component production materials used in this embodiment are as follows:

[0060] Activated magnesium oxide cement and ordinary Portland cement were used as the primary binders. Magnesium oxide was purchased from Hebei Longkai New Materials Co., Ltd., Portland cement from Conch Cement, and recycled aggregate was obtained from the demolition of old buildings in Qixia District, Nanjing.

[0061] Table 1 Oxide composition of the main components of each material

[0062] <![CDATA[SiO2]]> CaO <![CDATA[AL2O3]]> <![CDATA[Fe2O3]]> MgO <![CDATA[Na2O]]> <![CDATA[K2O]]> Cl Recycled Aggregates 40.819 32.901 12.136 5.851 3.598 1.035 1.403 0.063 magnesium oxide 0.08 0.02 / 1 99.2 / 0.05 Portland cement 21.28 59.60 4.76 2.70 5.12 / / /

[0063] Preparation of prefabricated components using recycled aggregates:

[0064] Recycled aggregate prefabricated components with sizes of 40 mm*40 mm*160 mm and 100 mm*100 mm*100 mm are prepared, and the raw materials include recycled fine aggregate (0-4.75 mm), magnesium oxide, Portland cement and water.

[0065] Magnesium oxide and Portland cement were mixed in a mass ratio of 1:3 to serve as a gelling agent;

[0066] The gelling agent and recycled fine aggregate were mixed in a mass ratio of 1:2.75 as dry material;

[0067] Add water to the mixed dry materials and stir, with the mass ratio of water to gelling agent being 0.55;

[0068] Pour the mixed recycled aggregate concrete into the mold. The mold is a 40mm*40mm*160mm cuboid and a 100mm*100mm*100mm cube. Use a vibrating table to compact the concrete during the pouring process.

[0069] Use a scraper to smooth the surface of the concrete mix during the vibration process;

[0070] Place the poured concrete mix together with the mold in a standard curing room and cure for 24 hours to develop a certain strength;

[0071] The precast component samples that have developed strength are demoulded.

[0072] Optimal carbon dioxide gas pressure during the preparation of saturated carbonic acid solution:

[0073] Table 2 Physical parameters of carbon dioxide

[0074]

[0075] Henry's Law: Proposed by British scientist William Henry in 1803. It reveals the relationship between the solubility of a gas in a liquid and the partial pressure of the gas at a constant temperature.

[0076] C=k H ·P

[0077] C is the solubility of the gas in the liquid (e.g., expressed in molar concentration mol / L).

[0078] k H is Henry's constant, which depends on the nature of the gas, the nature of the liquid, and the temperature (usually expressed in mol / L). P is the partial pressure of the gas at the surface of the liquid (usually expressed in atm.).

[0079] Table 3 Solubility of carbon dioxide in water at different pressures at 20°C calculated by Henry's law

[0080] Pressure (Atm.) <![CDATA[Solubility (g CO2 / L H2O)]]> 1 1.45233 5 7.26165 10 14.5233 15 21.78495 20 29.0466 25 36.30825 30 43.5699 35 50.83155 40 58.0932 45 65.35485 50 72.6165

[0081] According to Table 3 and Figure 3 It can be seen that the solubility of carbon dioxide in water increases with decreasing temperature and increasing pressure. When the temperature is below the critical temperature and the pressure is greater than the critical pressure, carbon dioxide will transform into a liquid state. However, when the temperature is above the critical temperature, carbon dioxide will remain in a gaseous state regardless of the applied pressure. Therefore, lowering the temperature while increasing the pressure will facilitate the dissolution of carbon dioxide in water, but too low a temperature will affect the hydration of prefabricated components. Therefore, the temperature of the carbonization process is set to 20°C.

[0082] Nanobubbles are ultrafine bubbles with a diameter of less than 1000 μm. Compared to ordinary bubbles, nanobubbles offer two key advantages in terms of physicochemical properties: higher mass transfer rates and greater stability. Specifically, nanobubbles have a significantly higher surface-to-volume ratio. For the same volume of carbon dioxide gas, the mass transfer coefficient can be increased by up to 11 times. Due to buoyancy, ordinary bubbles rise to the surface of the solution and burst within seconds of generation. However, due to their high surface area and the resulting rapid dissolution of the internal gas, nanobubbles tend to shrink, resulting in reduced buoyancy. Simultaneously, the high zeta potential of nanobubbles leads to strong inter-bubble repulsion, which reduces the coalescence of adjacent bubbles and increases their stability. When a high-pressure saturated carbonic acid solution enters the wet carbonization chamber, the sudden pressure drop produces a large number of carbon dioxide nanobubbles, which facilitates the carbonization reaction. Therefore, the pressure in the wet carbonization chamber is set at atmospheric pressure.

[0083] The specific process of the method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution provided in this embodiment is as follows:

[0084] Step 1: Place 12 cuboid-shaped recycled aggregate prefabricated components with a volume of 0.256 L or 3 cubic-shaped recycled aggregate prefabricated components with a volume of 1 L into a metal cage;

[0085] Step 2: Place the metal cage and prefabricated components into a wet carbonization box, with the highest point of the prefabricated components required to be lower than the outlet of the unsaturated carbonic acid solution;

[0086] Step 3: Open the valve connecting the high-pressure saturation bottle and the inlet and outlet of the unsaturated carbonic acid solution of the wet carbonization box;

[0087] Step 4: Weigh 30L of matrix solution and add it to the wet carbonization box and the high-pressure saturation bottle. The volume ratio of the solution in the high-pressure saturation bottle to the wet carbonization box is about 1:10. The liquid level should be higher than the outlet of the unsaturated carbonic acid solution but lower than the outlet of the escaping gas. Stop adding the matrix solution when the matrix solution can no longer enter the high-pressure saturation bottle due to the liquid level difference.

[0088] Step 5: Turn on the stirrer in the wet carbonization box at a speed of 30 rpm and close the door of the wet carbonization box;

[0089] Step 6: Close the valve connecting the high-pressure saturation bottle and the inlet and outlet of the unsaturated carbonic acid solution of the wet carbonization box, and open the valve connecting the high-pressure saturation bottle and the gas pressure pump;

[0090] Step 7: Open the carbon dioxide gas source or gas storage bag, turn on the gas pressure pump, pressurize the carbon dioxide gas in the high-pressure saturation bottle to 4.5 MPa, and maintain it for 15 seconds to allow the carbon dioxide to quickly dissolve in the matrix solution;

[0091] Step 8: Close the valve connecting the high-pressure saturation bottle and the gas pressure pump, open the sluice gate connecting the high-pressure saturation bottle and the saturated carbonic acid solution inlet of the wet carbonization box, and pressurize the high-pressure saturated carbonic acid solution into the wet carbonization box by air pressure to form a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles;

[0092] Step 9: Close the sluice gate connecting the high-pressure saturation bottle and the saturated carbonate solution inlet of the wet carbonization tank, and open the valve connecting the high-pressure saturation bottle and the unsaturated carbonate solution inlet and outlet of the wet carbonization tank to allow the unsaturated carbonate solution to re-enter the high-pressure saturation bottle through the liquid level difference (the amount of solution entering the high-pressure saturation bottle each time is about 1 / 10 of the total amount in the carbonization tank);

[0093] Step 10: Repeat steps 6 to 9 30 times, with a total reaction time of 30 seconds each time (15 seconds for carbon dioxide saturation plus 15 seconds for carbonization reaction), continuously inputting a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles into the wet carbonization box, and continuously inputting an unsaturated carbonic acid solution into the high-pressure saturated bottle to ensure that the carbonization reaction in the wet carbonization box and the dissolution of carbon dioxide in the high-pressure saturated bottle continue to occur efficiently;

[0094] Step 11: turn off the carbon dioxide gas source, air pump, stirrer, and all valves, open the wet carbonization box, take out the prefabricated components in the metal cage, and obtain the carbonized and strengthened recycled aggregate prefabricated components.

[0095] CO2 absorption capacity detection method: By weighing the total mass difference between the CO2 gas source and the gas storage bag before and after the test, the CO2 absorption capacity during the carbonization process can be obtained.

[0096] Carbonization depth detection method: Use a cutting machine to cut the sample in half along the center line of the short side of the sample, and spray phenolphthalein on the cut surface. The principle of phenolphthalein developing color in an alkaline environment is used to indicate the carbonization effect. The reddened area is the uncarbonized area, and the non-reddened area is the uncarbonized area.

[0097] CO2 escape volume detection method: Measure the volume change of the gas storage bag during the test, and the total volume increment is the escaped gas volume.

[0098] CO2 single utilization rate detection method: Use the device described in the present invention to carry out carbonization. By recycling the escaped CO2, the overall CO2 utilization rate can reach almost 100%. The CO2 single utilization rate refers to the utilization rate of CO2 in a single carbonization process before recycling. It can be calculated by subtracting the CO2 escape mass from the mass difference before and after the CO2 gas source test and dividing it by the mass difference before and after the CO2 gas source test.

[0099] Strength testing method: The compressive strength of prefabricated components was measured using an unconfined compression test with a loading speed of 1 mm / min.

[0100] The test results are shown in Table 4 and Table 5.

[0101] Comparative Example 1

[0102] Replace steps 7, 8, 9, 10 and 11 in Example 1 with:

[0103] Step 7: Open the water gate connecting the high-pressure saturation bottle and the saturated carbonic acid solution inlet of the wet carbonization box;

[0104] Step 8: Turn on the carbon dioxide gas source, turn on the gas pressure pump, and inject carbon dioxide gas into the high-pressure saturated bottle at a pressure of 0.1 MPa, so that the carbon dioxide gas can directly enter the wet carbonization box at a pressure close to atmospheric pressure through the high-pressure saturated bottle and the saturated carbonic acid solution inlet (in this state, the carbon dioxide pressure is close to atmospheric pressure and the flow rate is about 10L / min);

[0105] Step 9: Maintain continuous injection of carbon dioxide gas, with a total reaction time of 15 minutes;

[0106] Step 10: Turn off the carbon dioxide gas source, air pump, stirrer, and all valves, open the wet carbonization box, take out the prefabricated components in the metal cage, and obtain the carbonized and strengthened recycled aggregate prefabricated components.

[0107] Method for measuring the amount of unrecycled CO2 gas escaping under normal pressure conditions: After carbonization is completed, the volume change of the gas storage bag is measured. Since the gas storage bag is not connected to the gas pressure pump in this embodiment, the volume of CO2 gas stored in the gas storage bag is the actual volume of CO2 gas escaping.

[0108] The test results are shown in Table 4 and Table 5.

[0109] Example 2

[0110] Compared with Example 1, the pressure in the high-pressure saturation bottle was adjusted, and the prefabricated components were carbonized using saturated carbonic acid solutions saturated at pressures of 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa (i.e., Example 1), 5.0 MPa, and 5.5 MPa, respectively, which are Examples 2-1 to 2-10.

[0111] The test results are shown in Table 4 and Table 5.

[0112] Example 3

[0113] The number of repetitions of step 10 in Example 1 was changed to 60 times while keeping the other steps unchanged.

[0114] The test results are shown in Table 4 and Table 5.

[0115] Example 4

[0116] The number of repetitions of step 10 in Example 1 was changed to 120 times while keeping the other steps unchanged.

[0117] The test results are shown in Table 4 and Table 5.

[0118] Example 5

[0119] The number of repetitions of step 10 in Example 1 was changed to 240 times while keeping the other steps unchanged.

[0120] The test results are shown in Table 4 and Table 5.

[0121] Table 4 Comparison of carbon dioxide gas utilization rate and carbonization effect under different saturation pressures (40*40*160mm components)

[0122]

[0123]

[0124] It can be seen that when the carbon dioxide is not saturated and directly input into the wet carbonization box at atmospheric pressure, most of the carbon dioxide cannot effectively participate in the carbonization reaction. The unreacted carbon dioxide directly escapes in the form of gas, resulting in extremely low carbon dioxide utilization (only 13%) and shallow carbonization depth (less than 1mm). As the carbon dioxide saturation pressure increases from atmospheric pressure to 4.5MPa, the carbonization depth and CO2 absorption capacity increase significantly. At 4.5MPa, the carbonization depth reaches 19.1mm and the CO2 absorption capacity reaches 278g. At this time, the carbon dioxide gas remaining in the high-pressure saturation bottle after the saturated carbonic acid solution is prepared can completely press the saturated carbonic acid solution into the wet carbonization box, and the CO2 utilization efficiency is the highest (>99%). When the carbon dioxide saturation pressure exceeds 4.5MPa, although the carbonation depth and CO2 absorption capacity continue to increase with the increase of saturation pressure, there is too much carbon dioxide gas remaining in the high-pressure saturation bottle after the saturated carbonic acid solution is prepared at too high a pressure. In addition to pressing the saturated carbonic acid solution into the wet carbonization box, it will also directly escape into the wet carbonization box, resulting in an increase in the CO2 escape volume and a decrease in the CO2 single utilization rate. Moreover, when the saturation pressure exceeds 4.5MPa, the increase in carbonization depth decreases. In summary, 4.5MPa is the preferred saturation pressure. At the same time, the carbonization efficiency and carbon dioxide utilization rate of carbonization using the high-pressure saturation carbonization method and equipment described in the present invention are much higher than those of existing carbonization methods.

[0125] Comparative Example 2

[0126] After demoulding, the prefabricated components of Example 1 were placed in a standard curing room for curing for 28 days. The humidity in the standard curing room was above 95%, the temperature was 20±2° C., and the carbon dioxide concentration was 0.04%.

[0127] The compressive strength and carbonization depth of the material were tested in accordance with relevant standards. The test results are shown in Table 4.

[0128] Comparative Example 3

[0129] The prefabricated components of Example 1 were demoulded and placed in a concrete carbonation test box for carbonization for 3 days. The temperature in the carbonization box was set at 20° C., the carbon dioxide concentration was 20%, and the humidity was 75%.

[0130] The compressive strength and carbonization depth of the material were tested in accordance with relevant standards. The test results are shown in Table 4.

[0131] Comparative Example 4

[0132] The prefabricated components of Example 1 were demoulded and placed in a concrete carbonation test box for carbonization for 7 days. The temperature in the carbonization box was set at 20° C., the carbon dioxide concentration was 20%, and the humidity was 75%.

[0133] The compressive strength and carbonization depth of the material were tested in accordance with relevant standards. The test results are shown in Table 4.

[0134] Comparative Example 5

[0135] The prefabricated components of Example 1 were demoulded and placed in a concrete carbonation test box for carbonization for 14 days. The temperature in the carbonization box was set at 20° C., the carbon dioxide concentration was 20%, and the humidity was 75%.

[0136] The compressive strength and carbonization depth of the material were tested in accordance with relevant standards. The test results are shown in Table 4.

[0137] Comparative Example 6

[0138] The prefabricated components of Example 1 were demoulded and placed in a concrete carbonation test box for carbonization for 28 days. The temperature in the carbonization box was set at 20° C., the carbon dioxide concentration was 20%, and the humidity was 75%.

[0139] The compressive strength and carbonization depth of the material were tested in accordance with relevant standards. The test results are shown in Table 4.

[0140] Table 5 Comparison of concrete compressive strength development obtained by the embodiment and the comparative example (100*100*100mm component)

[0141] Strength / MPa Carbonization depth / mm Example 1 4 19 Example 3 13 36 Example 4 25 45 Example 5 28 50 Comparative Example 2 8 0 Comparative Example 3 4 17 Comparative Example 4 18 37 Comparative Example 5 26 42 Comparative Example 6 30 50

[0142] The test results of the embodiments and comparative examples show that when the apparatus and method of the present invention are used to carbonize recycled aggregate prefabricated components, the strength of the recycled aggregate prefabricated components increases rapidly when the number of cycles increases from 30 to 120 (when the carbonization time increases from 15 minutes to 1 hour). However, when the number of cycles increases from 120 to 240 (when the carbonization time increases from 1 hour to 2 hours), the rate of strength growth of the recycled aggregate prefabricated components decreases significantly, indicating that the carbonization reaction is nearly complete. This result is consistent with the carbonization depth results, indicating that using the apparatus and method of the present invention to carbonize recycled aggregate prefabricated components, 120 cycles of carbonization (carbonization for 1 hour) can achieve near-complete carbonization, resulting in a final strength of more than 90%.

[0143] Comparison with the results of the comparative example shows that the device and method of the present invention are highly efficient in carbonizing recycled aggregate prefabricated components. The physical and mechanical properties of the sample after 120 cycles of carbonization (1 hour of carbonization) using the device and method of the present invention are similar to those of the sample after 14 days of carbonization in the comparative example. Compared with the sample after 28 days of standard curing in the comparative example, the strength of the sample carbonized using the device and method of the present invention is significantly improved.

[0144] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution, characterized in that: The recycled aggregate prefabricated components are placed in a wet carbonization box, and a high-pressure saturated carbonic acid solution is fed into the wet carbonization box to generate a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles, and carbonization treatment is performed to complete the strengthening of the recycled aggregate prefabricated components.

2. The method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution according to claim 1, characterized in that: The temperature of the carbonization treatment is 20±5°C, and the volume ratio of the saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles to the recycled aggregate prefabricated component is greater than 5:

1.

3. The method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution according to claim 1, characterized in that: The saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is a water-based solution, which is obtained by dissolving in a high-pressure carbon dioxide atmosphere and then reducing the pressure.

4. The method of using a high-pressure saturated carbonic acid solution to efficiently carbonize and strengthen recycled aggregate prefabricated components according to claim 3, characterized in that: The pressure of the high-pressure carbon dioxide atmosphere is 4-5 MPa.

5. The method of utilizing high-pressure saturated carbonic acid solution to efficiently carbonize and strengthen recycled aggregate prefabricated components according to claim 1, characterized in that: During the carbonization process, fresh saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles is used to continuously replace the reacted unsaturated carbonic acid solution in the wet carbonization box.

6. The method for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution according to claim 5, characterized in that: The replacement frequency satisfies the following requirement: 1 / 10 of the saturated carbonic acid solution in the wet carbonization box is replaced every 15 to 20 seconds.

7. The method of claim 1 for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution, characterized in that: The recycled aggregate prefabricated component is prepared by the following method: Portland cement and magnesium oxide are mixed in a mass ratio of 1:2-4 as a gelling agent, and the gelling agent is then mixed with recycled fine aggregate with a particle size of no more than 4.75 mm in a mass ratio of 1:2.5-3 as a dry material; Add water to the evenly mixed dry material and stir, with the mass ratio of water to gelling agent being 0.5-0.6:1, then pour into a mold, vibrate to compact, scrape the surface, maintain, and demould to obtain a prefabricated component sample, which is a recycled aggregate prefabricated component.

8. The method of claim 1 for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution, characterized in that: The size of the recycled aggregate prefabricated component is (35-105) mm*(35-105) mm*(90-170) mm.

9. A device for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution, which is used to implement the method according to any one of claims 1 to 8, characterized in that: The device comprises: CO2 gas source, used for providing CO2 gas; A pressure pump, used for pressurizing the CO2 gas output from the CO2 gas source; High-pressure saturation bottle, used to receive pressurized CO2 gas and process the matrix solution to obtain high-pressure saturated carbonic acid solution; The wet saturation box is used to reduce the pressure of the high-pressure saturated carbonic acid solution to generate a saturated carbonic acid solution rich in micro-nano carbon dioxide bubbles and to place the recycled aggregate prefabricated components to be processed. The bottom of the box is provided with a saturated carbonic acid solution inlet connected to the liquid outlet of the high-pressure saturation bottle, and the top is provided with an unsaturated carbonic acid solution outlet that returns to the liquid inlet of the high-pressure saturation bottle.

10. The device for efficiently carbonizing and strengthening recycled aggregate prefabricated components using a high-pressure saturated carbonic acid solution according to claim 9, characterized in that: The top of the wet saturation box is also provided with a carbon dioxide escape port, which is connected in sequence to the gas storage bag and the inlet of the pressure pump through a pipeline, so that the escaped carbon dioxide can participate in secondary carbonization and improve the utilization rate of carbon dioxide.

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