A device for pre-soaking and vacuum strengthening recycled coarse aggregate

Abstract

The present application relates to the technical field of low-carbon green building materials, and particularly relates to a recycled coarse aggregate pre-soaking and vacuum strengthening device, which comprises a pre-soaking and leaching unit and a carbonation reaction unit which are independent of each other. The pre-soaking and leaching unit comprises a pre-soaking tank, a detachable mesh basket tray, a movable support structure and a stirring assembly, and is used for carrying the aggregate to ascend and descend between a soaking position and a leaching position and supplement calcium source. The carbonation reaction unit comprises a sealed carbonation reaction box, an internal tray, a CO2 cylinder, a vacuum pump and an environmental monitoring assembly, and is used for evacuating pores after vacuumizing and filling CO2 for carbonation strengthening. The present application has the advantages of simple process, controllable parameters and stable treatment effect, and solves the problem of uneven carbonation and improves the aggregate compactness through the synergistic effect of calcium supplementing and vacuum-assisted carbonation.

Description

Technical Field

[0001] This invention relates to the field of low-carbon green building materials technology, and in particular to a device for pre-soaking and vacuum strengthening of recycled coarse aggregate. Background Technology

[0002] With the acceleration of urbanization and the upgrading of infrastructure, a large amount of construction waste is generated, of which waste concrete accounts for a very high proportion. Crushing and screening waste concrete to prepare recycled coarse aggregate, thereby realizing the resource utilization of construction waste, is an important way to alleviate the depletion of natural sand and gravel resources and reduce carbon emissions.

[0003] However, recycled coarse aggregates typically have a large amount of old cement paste adhering to their surface, and contain numerous microcracks and interconnected pores, resulting in defects such as high water absorption, high porosity, low elastic modulus, and poor interfacial bonding performance. Existing pretreatment methods for recycled coarse aggregates are mainly divided into single modification treatments (such as single carbonization, single nano-silica treatment, acid-alkali treatment, etc.) and simple composite modification treatments (such as mechanical grinding combined with acid washing, mechanical grinding combined with carbonization, carbonization combined with nano-silica, slurry coating combined with mineral admixtures, etc.). These existing technologies have bottlenecks in terms of permeability, uniformity, synergy, and efficiency, exhibiting problems such as poor carbonization uniformity, easy agglomeration of nanoparticles, damage to aggregate edges and corrosion of the matrix, limited carbonization depth and uneven reaction, and difficulty in controlling the uniformity and thickness of the coating layer. Therefore, they cannot achieve efficient and stable improvement in the quality of recycled coarse aggregates.

[0004] Therefore, there is an urgent need for a device for pre-soaking and vacuum strengthening of recycled coarse aggregates to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-soaking and vacuum strengthening device for recycled coarse aggregate. Through the Ca(OH)2 pre-soaking-vacuum synergistic carbonization strengthening device, the carbonization effect is synergistically strengthened, thereby improving the strength of recycled coarse aggregate. It is necessary to solve the problem of uneven carbonization during the pretreatment of recycled aggregate.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a pre-soaking and vacuum strengthening device for recycled coarse aggregate, comprising a pre-soaking leaching unit and a carbonization reaction unit that are independent of each other. The recycled coarse aggregate after being treated by the pre-soaking leaching unit is transferred to the carbonization reaction unit for carbonization strengthening. The pre-soaking and draining unit includes a pre-soaking tank for holding soaking liquid, and a detachable wire basket tray for carrying the first recycled coarse aggregate is provided in the pre-soaking tank. The detachable wire basket tray is raised and lowered between the soaking position and the draining position by the drive of the movable support structure. A stirring component for agitating the soaking liquid is provided in the pre-soaking tank. The carbonization reaction unit includes a sealed carbonization reaction chamber, inside which is an internal tray for placing the second recycled coarse aggregate; the carbonization reaction chamber is connected to a CO2 cylinder and a vacuum pump, the CO2 cylinder is used to supply CO2 into the carbonization reaction chamber, and the vacuum pump is used to evacuate the carbonization reaction chamber; the carbonization reaction chamber is equipped with an environmental monitoring component for monitoring the environment inside the chamber.

[0007] Preferably, the pre-soaking and draining unit further includes a guide rail disposed vertically on the pre-soaking tank, the movable support structure being slidably disposed on the guide rail, and a locking module for locking the position between the movable support structure and the guide rail, for locking the movable support structure in the draining position or the soaking position.

[0008] Preferably, the locking module includes an independently configured upper positioning pin and a lower positioning pin. The upper positioning pin is used to lock the movable support structure in the draining position, and the lower positioning pin is used to lock the movable support structure in the soaking position.

[0009] Preferably, the stirring assembly includes a telescopic guide rod, with a stirring paddle at the bottom end of the telescopic guide rod and a low-speed stirrer connected to the top end of the telescopic guide rod. The low-speed stirrer drives the stirring paddle to intermittently rotate and stir below the surface of the soaking liquid.

[0010] Preferably, the carbonization reaction chamber is provided with an openable and closable door, and a compression lock and a silicone sealing strip are provided between the door and the chamber body to achieve a sealed and locked door.

[0011] Preferably, the environmental monitoring components include a temperature and humidity sensor, a CO2 concentration sensor, and a pressure gauge disposed on the top of the carbonization reaction chamber.

[0012] Preferably, the CO2 cylinder is connected to the carbonization reaction chamber via a CO2 filling pipe, and the CO2 filling pipe is equipped with a CO2 one-way inlet valve that allows CO2 to enter the carbonization reaction chamber in only one direction.

[0013] Preferably, the vacuum pump is connected to the carbonization reaction chamber via a gas extraction pipeline, and a vacuum valve for controlling the on / off state is provided on the gas extraction pipeline.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention discloses a pre-soaking and vacuum strengthening device for recycled coarse aggregate, including a pre-soaking leaching unit and a carbonization reaction unit that are independent of each other. The recycled coarse aggregate after being treated by the pre-soaking leaching unit is transferred to the carbonization reaction unit for carbonization strengthening. This can realize the separate control of the pre-soaking calcium supplementation and carbonization strengthening processes, avoid mutual interference of environmental parameters, facilitate independent parameter optimization and batch production line operation, and improve processing efficiency and process stability. The pre-soaking and draining unit includes a pre-soaking tank for holding the soaking solution, which contains a detachable wire basket tray for carrying the first recycled coarse aggregate. The tray is driven by a movable support structure to move up and down between the soaking and draining positions, allowing the soaking and calcium supplementation and draining processes to be completed in the same tank. This eliminates the need for manual handling, enabling the separation of aggregate from the soaking solution, reducing labor intensity, and avoiding secondary damage during the transfer process. The pre-soaking tank is also equipped with a stirring component, which agitates the soaking solution to promote the penetration of saturated Ca(OH)2 solution into the old mortar layer and open pores on the surface of the aggregate, improving the uniformity and efficiency of calcium source supplementation and avoiding local concentration gradients and insufficient penetration caused by static soaking. The carbonization reaction unit includes a sealed carbonization reaction chamber with an internal tray for placing the second recycled coarse aggregate, ensuring that the aggregate is in full contact with CO2 gas in a stable environment. The carbonization reaction chamber is connected to a CO2 cylinder and a vacuum pump. The CO2 cylinder supplies CO2, and the vacuum pump creates a vacuum. By first creating a vacuum, air inside the chamber and residual gas in the pores of the aggregate are actively removed, eliminating the resistance of pore gas to CO2 diffusion and opening up permeation channels for CO2 to diffuse more deeply and evenly into the pores of the aggregate. Subsequently, CO2 is introduced, reacting with the Ca(OH)2 and other carbonizable components already added inside the aggregate to generate CaCO3, achieving in-situ filling of pores and microcracks. The carbonization reaction chamber is equipped with an environmental monitoring component that can monitor parameters such as temperature, humidity, CO2 concentration, and pressure in real time to ensure that the carbonization reaction is always under optimal process conditions, guaranteeing the stability and repeatability of the carbonization effect. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the carbonization reaction unit structure of the present invention; Figure 2 This is a schematic diagram of the pre-soaking drain unit structure of the present invention; In the diagram: 1. CO2 cylinder; 2. Compression lock; 3. Silicone sealing strip; 4. Vacuum pump; 5. Carbonization reaction chamber; 6. Temperature and humidity sensor; 7. CO2 concentration sensor; 8. Pressure gauge; 9. Exhaust valve; 10. CO2 one-way inlet valve; 11. Internal tray; 12. Second recycled coarse aggregate; 13. Vacuum valve; 14. CO2 charging pipe; 15. Guide rail; 16. Stirring paddle; 17. Lifting handle; 18. Low-speed stirrer; 19. Upper positioning pin; 20. Lower positioning pin; 21. Ca(OH)2 solution level; 22. Removable mesh basket tray; 23. Drain valve; 24. First recycled coarse aggregate; 25. Telescopic guide rod; 26. Movable support structure. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Reference Figure 1 and Figure 2 As shown, this embodiment provides a pre-soaking and vacuum strengthening device for recycled coarse aggregate, including a pre-soaking leaching unit and a carbonization reaction unit that are independent of each other. The recycled coarse aggregate after being treated by the pre-soaking leaching unit is transferred to the carbonization reaction unit for carbonization strengthening. The pre-soaking and draining unit includes a pre-soaking tank for holding soaking liquid, and a detachable wire basket tray 22 for carrying the first recycled coarse aggregate 24 is provided in the pre-soaking tank. The detachable wire basket tray 22 is raised and lowered between the soaking position and the draining position by the drive of the movable support structure 26. A stirring component for agitating the soaking liquid is provided in the pre-soaking tank. The carbonization reaction unit includes a sealed carbonization reaction chamber 5, inside which is an internal tray 11 for placing the second recycled coarse aggregate 12; the carbonization reaction chamber 5 is connected to a CO2 cylinder 1 and a vacuum pump 4, the CO2 cylinder 1 is used to supply CO2 into the carbonization reaction chamber 5, and the vacuum pump 4 is used to evacuate the carbonization reaction chamber 5; the carbonization reaction chamber 5 is equipped with an environmental monitoring component for monitoring the environment inside the chamber.

[0019] This invention discloses a pre-soaking and vacuum strengthening device for recycled coarse aggregate, comprising an independent pre-soaking leaching unit and a carbonization reaction unit. The recycled coarse aggregate after being treated by the pre-soaking leaching unit is transferred to the carbonization reaction unit for carbonization strengthening. This device can separate and control the pre-soaking calcium supplementation and carbonization strengthening processes, avoid mutual interference of environmental parameters, facilitate independent parameter optimization and batch production line operation, and improve processing efficiency and process stability. The pre-soaking and draining unit includes a pre-soaking tank for holding the soaking solution, which contains a detachable wire basket tray 22 for carrying the first recycled coarse aggregate 24. The tray is driven by a movable support structure 26 to move up and down between the soaking and draining positions, allowing the soaking and calcium supplementation and draining processes to be completed in the same tank. This eliminates the need for manual handling, enabling the separation of aggregate and soaking solution, reducing labor intensity, and avoiding secondary damage during the transfer process. The pre-soaking tank is also equipped with a stirring component, which agitates the soaking solution to promote the penetration of saturated Ca(OH)2 solution into the old mortar and open pores on the surface of the aggregate, improving the uniformity and efficiency of calcium source supplementation and avoiding local concentration gradients and insufficient penetration caused by static soaking. The carbonization reaction unit includes a sealed carbonization reaction chamber 5, which contains an internal tray 11 for placing the second recycled coarse aggregate 12, ensuring that the aggregate is in full contact with CO2 gas in a stable environment. The carbonization reaction chamber 5 is connected to a CO2 cylinder 1 and a vacuum pump 4. The CO2 cylinder 1 is used to supply CO2, and the vacuum pump 4 is used to create a vacuum. By first creating a vacuum, the air inside the chamber and the residual gas in the pores of the aggregate are actively removed, eliminating the resistance of pore gas to CO2 diffusion and opening up a permeation channel for CO2 to diffuse more deeply and evenly into the pores inside the aggregate. Then, CO2 is introduced, which reacts with the Ca(OH)2 and other carbonizable components already added inside the aggregate to generate CaCO3, achieving in-situ filling of pores and microcracks. The carbonization reaction chamber 5 is equipped with an environmental monitoring component, which can monitor parameters such as temperature, humidity, CO2 concentration and pressure inside the chamber in real time to ensure that the carbonization reaction is always under optimal process conditions, ensuring the stability and repeatability of the carbonization effect.

[0020] In one embodiment of the present invention, a large amount of old cement mortar adheres to the surface of the recycled coarse aggregate. Carbon dioxide can enter the aggregate through the mortar pores and react with the internal moisture to generate carbonic acid. The carbonic acid can then react chemically with the internal calcium ions to generate calcium carbonate, which adheres to the interior of the aggregate. This calcium carbonate can fill the microcracks in the recycled aggregate, improve the transition zone between the aggregate and the mortar, and provide structural support for the aggregate. Simultaneously, there are other carbonatable substances inside the aggregate, such as hydrated calcium silicate (CSH), unhydrated tricalcium silicate, and dicalcium silicate. Carbon dioxide can also react with these carbonatable substances to generate calcium carbonate and silica gel. The internal reaction formula includes: Further optimizing the design, the pre-soaking and draining unit also includes a guide rail 15 vertically mounted on the pre-soaking tank. A movable support structure 26 is slidably mounted on the guide rail 15. A locking module is provided between the movable support structure 26 and the guide rail 15 to lock the movable support structure 26 in either the draining or soaking position. With the guide rail 15 vertically mounted on the pre-soaking tank, the detachable mesh basket tray 22 slides smoothly on the guide rail 15 via the movable support structure 26. The locking module between the movable support structure 26 and the guide rail 15 can fix the mesh basket tray at two different heights: the soaking position and the draining position. This ensures the stability and positional accuracy of the mesh basket tray during lifting and lowering, preventing swaying that could cause aggregate impact or soaking liquid splashing. Simultaneously, the locking module allows for quick switching and reliable fixing between the soaking and draining working positions, simplifying and ensuring safe operation, improving process conversion efficiency, and guaranteeing sufficient draining without dripping or polluting the environment.

[0021] The design is further optimized by incorporating an independently configured upper positioning pin 19 and a lower positioning pin 20. The upper positioning pin 19 locks the movable support structure 26 in the draining position, while the lower positioning pin 20 locks it in the soaking position. The locking module utilizes two independently configured pins: the upper positioning pin 19 and the lower positioning pin 20. The upper positioning pin 19 locks the basket tray in the draining position above the liquid surface, facilitating aggregate draining and handling. The lower positioning pin 20 locks the basket tray in the soaking position below the liquid surface, ensuring the aggregate remains stably submerged in the solution during soaking. This allows for independent locking of the soaking and draining positions. The mechanical structure is simple, reliable, and cost-effective. Operation is simple: just insert and remove the corresponding pins to quickly switch working states, eliminating the need for complex electrical controls. The two positions do not interfere with each other, providing high positioning accuracy and effectively preventing tray slippage or positional displacement due to accidental loosening.

[0022] In one embodiment of the present invention, see Appendix Figure 2 As shown, the Ca(OH)2 solution surface 21 is located between the soaking position and the draining position.

[0023] In one embodiment of the present invention, a drain valve 23 is provided at the bottom of the pre-soaking tank. The drain valve 23 is connected to the lowest end of the inner cavity of the pre-soaking tank and is used to drain or replace the Ca(OH)2 solution in the pre-soaking tank. When the concentration of the solution decreases or precipitation occurs after multiple uses, the drain valve 23 can be opened to drain the old solution for tank cleaning and replenishment with fresh solution. In addition, during equipment maintenance, repair, or shutdown, the solution in the tank must be completely drained through the drain valve 23 to prevent long-term storage of the solution from causing crystallization or corrosion of the tank. This facilitates solution management and equipment maintenance, supports solution recycling, and reduces operating costs.

[0024] Further optimization of the design includes a retractable guide rod 25, with a stirring paddle 16 at its bottom and a low-speed agitator 18 connected to its top. The low-speed agitator 18 drives the stirring paddle 16 to intermittently rotate and stir below the surface of the soaking solution. The mixing assembly consists of the retractable guide rod 25, the stirring paddle 16, and the low-speed agitator 18. The stirring paddle 16 is installed at the bottom of the retractable guide rod 25 and can extend below the liquid surface via the extension and retraction of the guide rod, allowing for easy adjustment of the stirring paddle 16's immersion depth to accommodate different liquid levels. The low-speed agitator 18 is connected to the top of the guide rod, driving the stirring paddle 16 to perform intermittent rotation and stirring, reducing mechanical damage to the mortar adhering to the aggregate surface and preventing the generation of fine powder between aggregate particles due to continuous friction. Low-speed stirring also prevents air bubbles from being trapped, ensuring that the Ca(OH)2 solution fully penetrates the aggregate pores.

[0025] In one embodiment of the present invention, a lifting handle 17 is provided above the low-speed mixer 18 for lifting the low-speed mixer 18.

[0026] Further optimization of the design involves installing an openable and closable door on the carbonization reaction chamber 5. A pressure-locking latch 2 and a silicone sealing strip 3 are used to seal and lock the door between it and the chamber body. The pressure-locking latch 2 presses the door firmly against the chamber body, while the silicone sealing strip 3 fills the gap between the door and the chamber body. Together, they achieve a complete seal when the door is closed, preventing gas leakage and ensuring the airtightness of the carbonization reaction chamber 5 during vacuuming and CO2 filling processes. This prevents outside air from interfering with the reaction environment and avoids waste and safety hazards caused by CO2 leakage. It also maintains a stable negative or slightly positive pressure state, providing a reliable environmental guarantee for the carbonization reaction.

[0027] To further optimize the design, the environmental monitoring components include a temperature and humidity sensor 6, a CO2 concentration sensor 7, and a pressure gauge 8, all located at the top of the carbonization reaction chamber 5. These sensors are centrally located at the top of the chamber to monitor the internal temperature, relative humidity, carbon dioxide concentration, and pressure in real time. Operators can use this data to understand the environmental conditions inside the chamber and make corresponding adjustments. This facilitates centralized reading and unified management of the monitoring data, ensuring that the carbonization reaction is always under optimal environmental conditions (e.g., 20℃, 60% humidity, 20% CO2 concentration). When parameters deviate from the set range, timely intervention and adjustment are possible, ensuring the stability and repeatability of the carbonization effect for different batches of aggregate.

[0028] The scheme is further optimized. CO2 cylinder 1 is connected to carbonization reaction chamber 5 via CO2 filling pipe 14. CO2 filling pipe 14 is equipped with a CO2 one-way inlet valve 10 that allows CO2 to enter carbonization reaction chamber 5 in only one direction. CO2 cylinder 1 is connected to carbonization reaction chamber 5 through a dedicated filling pipeline. A one-way inlet valve is installed on the filling pipeline, allowing CO2 gas to flow only from the cylinder to the carbonization reaction chamber 5, while preventing gas from flowing back from the chamber to the cylinder. This ensures the safety and directional controllability of the filling process and prevents CO2 gas or the mixed gas in the reaction chamber from flowing back to the cylinder during the vacuuming stage or when the pressure inside the chamber fluctuates, thus avoiding contamination of the cylinder or damage to the pipeline. At the same time, CO2 can only enter the chamber in one direction during filling, maintaining the stability of the CO2 concentration inside the chamber, simplifying the operation process and improving the safety of equipment use.

[0029] Further optimizing the design, vacuum pump 4 is connected to carbonization reaction chamber 5 via an extraction pipeline, on which a vacuum valve 13 is installed to control its on / off state. Vacuum pump 4 is connected to carbonization reaction chamber 5 via an extraction pipeline, and a vacuum valve 13 is installed on the extraction pipeline to control the on / off state of the extraction pipeline. When vacuuming is required, the valve is opened to start the vacuum pump; when vacuuming is complete or when maintaining the vacuum level is necessary, the valve is closed to cut off the pipeline and maintain the vacuum state inside the chamber. This eliminates the need for continuous operation of the vacuum pump, saving energy. Simultaneously, the closed valve prevents outside air from being drawn back into the chamber through the pump body, ensuring the stability of the negative pressure environment inside the chamber and creating favorable conditions for subsequent CO2 filling.

[0030] In one embodiment of the present invention, an exhaust valve 9 is provided at the top of the carbonization reaction chamber 5 to release the gas pressure inside the carbonization reaction chamber 5 after the carbonization process is completed or when it is necessary to open the chamber door midway. After carbonization is completed, the exhaust valve 9 is opened first to discharge the residual CO2 gas inside the chamber, so as to balance the pressure inside and outside the chamber and facilitate the safe opening of the chamber door. In addition, if sampling and testing are required during the carbonization process, the pressure must also be released through the exhaust valve 9 first to avoid high-pressure gas ejection and causing safety hazards, thus ensuring the safety and convenience of equipment operation.

[0031] The pre-soaking and vacuum strengthening process of recycled coarse aggregate in this invention: First, the aggregate is soaked in a saturated calcium hydroxide solution, allowing the calcium solution to penetrate into the pores of the aggregate and replenish the calcium source, thus solving the problem of insufficient calcium source. In the pre-soaking and leaching unit, the first recycled coarse aggregate 24 is filled into a detachable wire basket tray 22. The wire basket tray is driven down to the soaking position by the moving support structure 26 and locked by the lower positioning pin 20, so that the first recycled coarse aggregate 24 is completely submerged in the saturated Ca(OH)2 solution. The stirring assembly is started to intermittently disturb the soaking solution, so that the Ca(OH)2 solution can fully penetrate into the surface old mortar and interconnected pores of the first recycled coarse aggregate 24 to replenish the carbonizable calcium source. Then, the aggregate is lifted and drained, and placed in a constant temperature and humidity environment to adjust the moisture content to a suitable range, ensuring a suitable moisture environment for the carbonization reaction. After pre-soaking, the lower positioning pin 20 is unlocked, and the basket tray is lifted to the draining position by the moving support structure 26 and locked by the upper positioning pin 19, so that the first recycled coarse aggregate 24 stays above the liquid surface for draining to remove surface free liquid. Then, the drained first recycled coarse aggregate 24 is placed in a constant temperature and humidity environment for humidification treatment, and its moisture content changes are monitored until the pre-carbonization moisture content of the first recycled coarse aggregate 24 reaches the target range suitable for the carbonization reaction, forming the second recycled coarse aggregate 12. Next, the conditioned aggregate is placed in the carbonization chamber and a vacuum is drawn to remove air from the chamber and the pores of the aggregate, thus opening the CO2 diffusion channel. The conditioned second recycled coarse aggregate 12 is evenly spread on the inner tray 11 inside the carbonization reaction chamber 5. The chamber door is closed and sealed using the clamping latch 2 and the silicone sealing strip 3. The vacuum pump 4 is started and the vacuum valve 13 is opened to evacuate the inside of the carbonization reaction chamber 5 to a predetermined negative pressure value and maintain it for a certain period of time to remove air from the carbonization reaction chamber 5 and residual gas from the pores of the second recycled coarse aggregate 12, thereby providing a channel for CO2 diffusion. Finally, CO2 is introduced for carbonation, generating calcium carbonate to fill the pores, effectively solving the problems of uneven carbonation and limited penetration depth in existing technologies, and significantly reducing the water absorption rate of aggregates. Vacuum valve 13 is closed and vacuum pump 4 is stopped. CO2 one-way inlet valve 10 is opened, and CO2 gas is introduced into the carbonation reaction chamber 5 from CO2 cylinder 1 through CO2 filling pipe 14. The temperature, relative humidity and CO2 concentration inside the chamber are monitored in real time by environmental monitoring components and controlled within the preset range for carbonation reaction. During carbonation, the second recycled coarse aggregate 12 is turned over periodically so that CO2 reacts fully with the carbonizable components in the second recycled coarse aggregate 12 to generate CaCO3, which fills the pores and microcracks of the second recycled coarse aggregate 12.

[0032] The scheme was further optimized by periodically turning the second recycled coarse aggregate 12 during the carbonization process to improve carbonization uniformity. The progress of the carbonization reaction was judged by monitoring the mass change of the second recycled coarse aggregate 12 during the carbonization reaction. When the mass growth rate change was less than a predetermined threshold, the carbonization reaction was considered to have stabilized and the carbonization process was terminated. During the carbonization process, the second recycled coarse aggregate 12 in the carbonization box was turned over at regular intervals to ensure that all surfaces of the second recycled coarse aggregate 12 were evenly exposed to CO2 gas, avoiding the problem of insufficient local carbonization caused by aggregate stacking and improving the overall carbonization uniformity. At the same time, the mass of the aggregate was sampled and weighed periodically, and the mass growth rate was calculated. When the mass growth rate change of two consecutive measurements was less than a predetermined threshold, the carbonization reaction was judged to be basically completed. This method is more scientific and accurate than fixing the time based on experience, ensuring sufficient carbonization while avoiding over-processing and wasting time. It is simple to operate, reliable in judgment, and suitable for industrial mass production.

[0033] Specific examples: Step 1: Select crushed construction waste or waste concrete, remove steel bars, bricks, mud and other impurities, and then mechanically crush and screen to obtain recycled coarse aggregate with a particle size of 5mm to 31.5mm; in accordance with the relevant provisions of GB / T 25177—2010 "Recycled Coarse Aggregate for Concrete", screen the recycled coarse aggregate into continuous particle sizes of 5mm to 16mm, 5mm to 20mm, 5mm to 25mm or 5mm to 31.5mm.

[0034] Step Two: Place the sieved recycled coarse aggregate in a washing device and rinse its surface with high-pressure water to remove mud, loose old mortar particles, and other impurities adhering to the surface of the recycled coarse aggregate. The pressure of the high-pressure water flow is 0.3MPa to 0.8MPa, and the rinsing time is 3 to 10 minutes, until the rinse water is basically clear. After rinsing, spread the recycled coarse aggregate on a permeable screen with a thickness of 30mm, and place it in a well-ventilated, rain-protected indoor environment free from secondary pollution to air dry naturally. During the drying process, turn the recycled coarse aggregate every 6 to 12 hours to promote uniform evaporation of surface moisture. When the mass change rate obtained from two consecutive weighings is less than 0.1%, the recycled coarse aggregate is considered to have reached a constant weight state, and the dried recycled coarse aggregate is obtained.

[0035] Step 3: To improve the carbonization reaction efficiency of the recycled coarse aggregate and increase its internal carbonatable phase content, the aggregate is pre-soaked in a saturated calcium hydroxide solution. During use, a Ca(OH)₂ solution is added to the pre-soaking tank until the solution level reaches the set height. Then, the first recycled coarse aggregate 24, after screening, washing, and drying, is placed in a removable wire mesh tray 22, ensuring that the first recycled coarse aggregate 24 is evenly distributed within the tray.

[0036] Step 4: Install the detachable mesh basket tray 22 containing the first recycled coarse aggregate 24 onto the vertically movable support structure 26. The movable support structure can smoothly rise and fall vertically along the guide rail 15. Then, release the upper positioning pin 19, allowing the detachable mesh basket tray 22 to descend along the guide rail with manual assistance. When the detachable mesh basket tray descends to the lower positioning pin 20, insert the lower positioning pin 20 into the corresponding positioning hole to fix the detachable mesh basket tray 22 in the soaking position. The recycled coarse aggregate in the detachable mesh basket tray is completely or substantially immersed in the Ca(OH)2 solution, with a liquid-to-solid ratio preferably of 4:1, to ensure that the solution can fully contact the surface of the first recycled coarse aggregate 24 and the connecting pores.

[0037] Step 5: Place the retractable guide rod 25 connected to the stirring paddle 16 below the surface of the Ca(OH)2 solution. During the pre-soaking process, start the low-speed stirrer 18, control the stirring temperature at 22±2℃, and the stirring speed at 50-60 rpm. The total soaking time is 24 hours. Stir for 5-10 minutes every 45 minutes to promote the penetration of calcium hydroxide solution into the old mortar and open pores on the surface of the first recycled coarse aggregate 24, while avoiding long-term continuous strong stirring that could cause the aggregate to detach from the mortar or the particles to wear off.

[0038] Step Six: After soaking, pull out the lower positioning pin 20 and lift the detachable mesh basket tray 22 upwards along the guide rail 15 to the position of the upper positioning pin 19, fixing the detachable mesh basket tray 22 in the draining position; the preferred ambient temperature for humidification is 22±2℃, and the preferred relative humidity is 60% to 70%. During the humidification process, the moisture content is controlled based on the dry basis weight of the aggregate, keeping the pre-carbonization moisture content of the first recycled coarse aggregate 24 between 6% and 8%. The moisture content calculation formula is as follows. When the moisture content of the first recycled coarse aggregate 24 reaches the target range, the second recycled coarse aggregate 12 is formed, and then immediately enters the subsequent carbonization process. The drain valve 23 at the bottom of the pre-soaking tank can be used to drain or replace the Ca(OH)2 solution for subsequent cleaning, replenishment, or recycling.

[0039] In the formula: The current moisture content of the recycled coarse aggregate is %; The current mass of recycled coarse aggregate during the conditioning process, in grams; The dry weight (g) of this batch of recycled coarse aggregate after drying to constant weight.

[0040] Step 7: Evenly spread the conditioned second recycled coarse aggregate 12 in the inner tray 11 of the carbonization reaction box 5. The spreading thickness is controlled to be 30mm to 50mm. The amount of material in a single tray should be enough to form 1 to 2 layers of particle thickness. The total loading volume should not exceed 1 / 2 of the effective volume of the carbonization reaction box 5.

[0041] Step 8: After closing the chamber door, start the vacuum pump 4 and use the vacuum valve 13 located in the carbonization reaction chamber 5 to pump the pressure inside the chamber to -0.08MPa and maintain it for 5 to 10 minutes to remove the air inside the carbonization reaction chamber 5 and some of the gas in the connecting pores of the second recycled coarse aggregate 12.

[0042] Step 9: Then close the vacuum valve 13 and fill the chamber with gas through the CO2 filling pipe 14 to make the CO2 concentration in the chamber 20%±3%; the temperature control is 20±2℃; the relative humidity control is 60%; the carbonization time control is 48h; the pressure in the chamber is maintained in the range of 0 to 0.05MPa; the aggregate is turned over every 6h to 12h during the carbonization process to improve the uniformity of carbonization.

[0043] Step 10: During the carbonization process, take out a portion of the recycled coarse aggregate sample every 6 to 12 hours, wipe off the surface dust, weigh it, and calculate its mass growth rate. When the change in the mass growth rate obtained from two consecutive tests is less than 0.2%, the carbonization reaction is considered to be stabilizing.

[0044] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0045] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for pre-soaking and vacuum strengthening of recycled coarse aggregate, characterized in that: It includes a pre-soaking leaching unit and a carbonization reaction unit that are independent of each other. The recycled coarse aggregate after being treated by the pre-soaking leaching unit is transferred to the carbonization reaction unit for carbonization strengthening. The pre-soaking and draining unit includes a pre-soaking tank for holding soaking liquid, and a detachable wire basket tray (22) for carrying the first recycled coarse aggregate (24) is provided in the pre-soaking tank. The detachable wire basket tray (22) is raised and lowered between the soaking position and the draining position by the drive of the movable support structure (26). The pre-soaking tank is provided with a stirring component for agitating the soaking liquid. The carbonization reaction unit includes a sealed carbonization reaction chamber (5), and the carbonization reaction chamber (5) is provided with an internal tray (11) for placing the second recycled coarse aggregate (12); the carbonization reaction chamber (5) is connected to a CO2 cylinder (1) and a vacuum pump (4), the CO2 cylinder (1) is used to supply CO2 into the carbonization reaction chamber (5), and the vacuum pump (4) is used to evacuate the carbonization reaction chamber (5); the carbonization reaction chamber (5) is provided with an environmental monitoring component for monitoring the environment inside the chamber.

2. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The pre-soaking and draining unit also includes a guide rail (15) arranged vertically on the pre-soaking tank. The movable support structure (26) is slidably arranged on the guide rail (15). A locking module for locking the position is provided between the movable support structure (26) and the guide rail (15) to lock the movable support structure (26) in the draining position or the soaking position.

3. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 2, characterized in that: The locking module includes an independently configured upper positioning pin (19) and a lower positioning pin (20). The upper positioning pin (19) is used to lock the movable support structure (26) in the draining position, and the lower positioning pin (20) is used to lock the movable support structure (26) in the soaking position.

4. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The stirring assembly includes a telescopic guide rod (25), with a stirring paddle (16) at the bottom end of the telescopic guide rod (25) and a low-speed stirrer (18) connected to the top end of the telescopic guide rod (25). The low-speed stirrer (18) drives the stirring paddle (16) to rotate and stir intermittently below the surface of the soaking liquid.

5. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The carbonization reaction chamber (5) is equipped with an openable door. A pressure-locking buckle (2) and a silicone sealing strip (3) are provided between the door and the chamber body to achieve sealing and locking of the door.

6. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The environmental monitoring components include a temperature and humidity sensor (6), a CO2 concentration sensor (7), and a pressure gauge (8) installed on the top of the carbonization reaction chamber (5).

7. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The CO2 cylinder (1) is connected to the carbonization reaction chamber (5) through a CO2 filling pipe (14). The CO2 filling pipe (14) is equipped with a CO2 one-way inlet valve (10) that allows CO2 to enter the carbonization reaction chamber (5) in only one direction.

8. The pre-soaking and vacuum strengthening device for recycled coarse aggregate according to claim 1, characterized in that: The vacuum pump (4) is connected to the carbonization reaction chamber (5) through a gas extraction pipeline, and a vacuum valve (13) is provided on the gas extraction pipeline to control the on / off state.

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