Concrete waste recovery method and system based on freeze-thaw cycle cracking

Abstract

The invention provides a concrete waste recycling method and system based on freeze-thaw cycle cracking. The method mainly comprises the steps that concrete waste of a building site is preliminarily sorted and transported to a recycling point in a centralized mode; the concrete waste is preliminarily crushed to form concrete blocks with proper sizes, and impurities are separated at the same time; foreign matters attached to the surface of the concrete block are removed, and the concrete block is soaked to a saturated state; placing the saturated concrete block into a freeze-thaw cycle cabin, and promoting cracking of the concrete block through multiple freeze-thaw cycles; secondarily crushing the cracked concrete blocks, and dispersing the concrete blocks into concrete materials with different particle sizes; and the concrete material is subjected to graded recovery according to the particle size. The concrete is physically cracked through freezing and thawing circulation, the concrete waste recycling efficiency and the resource utilization rate are remarkably improved by combining an intelligent device and a control system, and the system is low in energy consumption, small in pollution and suitable for large-scale treatment of concrete waste in building construction and demolition scenes.

Description

Technical Field

[0001] This invention relates to the field of construction waste recycling technology, specifically to a method and system for recycling concrete waste based on freeze-thaw cycle pyrolysis, which is applicable to the green resource utilization of waste concrete generated from building demolition. Background Technology

[0002] In the context of the global push for sustainable development and the "carbon peaking and carbon neutrality" strategy, the green and resource-based transformation of the construction industry has become an inevitable trend. However, the construction of new buildings or the demolition of old buildings generate a large amount of waste concrete. Most of this waste concrete is transported to the countryside for dumping or landfill without any treatment, which not only occupies land resources but also easily causes environmental pollution. Recycling concrete waste and producing recycled concrete for reuse is of great significance for conserving resources and protecting the environment.

[0003] Traditional methods for recycling large concrete waste primarily rely on mechanical crushing, such as jaw crushers and hammer crushers. These methods use mechanical force to directly break down the concrete waste into smaller aggregates for subsequent screening, washing, and reuse.

[0004] This crushing method has significant drawbacks:

[0005] (1) A large amount of dust will be generated during the crushing process, which will not only pollute the surrounding environment, but also endanger the health of workers on site;

[0006] (2) It causes great wear and tear on the equipment, and the equipment parts need to be replaced regularly, which increases the equipment maintenance cost;

[0007] (3) Mechanical crushing equipment is large in size, consumes a lot of energy, and generates strong industrial noise.

[0008] In recent years, the improved concrete waste recycling methods mostly improve the concrete waste recycling efficiency by optimizing the crushing mode of concrete waste and take noise reduction measures to solve the noise problem. For example, CN109012860A discloses a concrete recycling material crushing device, which improves the processing efficiency in the concrete production process through multiple crushing and grinding equipment, and reduces the use noise by assisting dust and noise reduction devices, and improves the practicability of the equipment; CN112808421A discloses a concrete crushing and recycling device and a method thereof, which crushes the concrete by microwave and cavitation water jet, effectively separates the mortar attached to the surface of the aggregate, recovers the steel bars by the magnetic attraction device, and separates and recovers the aggregate by the screen. Although the above two methods optimize and improve the crushing mode of concrete waste, CN109012860A still essentially adopts the traditional mechanical crushing method and cannot solve the problems of high energy consumption and high loss of mechanical equipment; CN112808421A utilizes the selective characteristics of microwave heating to realize the internal cracking of concrete waste, but the temperature gradient and stress gradient generated at the interface of the aggregate and the mortar are insufficient, which makes it difficult to fully crack the concrete waste, and the strong crushing effect of the self-excited oscillation cavitation water jet is still needed to achieve full crushing.

[0009] Therefore, in order to meet the green and resource transformation needs of the construction industry, a low-dust and low-loss concrete waste recycling method is urgently needed. SUMMARY

[0010] In order to solve the problems of serious dust pollution, high equipment loss and high energy consumption in the existing mechanical crushing of concrete waste, the present application provides a concrete waste recycling method and system based on freeze-thaw cycle cracking. By destroying the microstructure of concrete through freeze-thaw cycle, microcrack propagation is induced and macroscopic cracking is realized, achieving low-dust, low-loss and clean treatment effect, and promoting the green development of construction waste recycling industry.

[0011] To achieve the above purpose, the present application is implemented as follows:

[0012] S10, the construction waste on the construction site is preliminarily sorted and separated from other waste to obtain concrete waste and is transported to the recycling point;

[0013] S20, the concrete waste after preliminary crushing and separation is crushed to form concrete blocks with appropriate size, and further separates fine impurities;

[0014] S30, removing foreign matters attached to the surface of the concrete blocks and soaking them to saturation state;

[0015] S40, placing the concrete blocks into a freeze-thaw cycle cabin to promote cracking through multiple freeze-thaw cycles;

[0016] S50, the concrete blocks after secondary crushing and cracking are made discrete into concrete materials of different particle sizes;

[0017] S60, the concrete materials are graded and recycled according to particle sizes.

[0018] In some embodiments, in S10, the preliminary sorting and centralized transportation of the concrete waste materials of the construction site to the recycling point comprises:

[0019] Setting up a temporary classification and storage point at the demolition site;

[0020] Carrying out the preliminary sorting of the concrete waste materials by manual or small machinery;

[0021] Orderly loading the sorted concrete waste materials into airtight transportation carriers;

[0022] After the airtight transportation carriers are full, carrying out transportation to the recycling point.

[0023] In some embodiments, in S20, the preliminary crushing of the concrete waste materials to form concrete blocks of appropriate sizes while separating impurities comprises:

[0024] S201, uniformly feeding the concrete waste materials into a primary crushing device to obtain primary crushed materials;

[0025] S202, then feeding into a heavy-duty vibrating screen to screen the primary crushed materials and separate large-sized concrete blocks;

[0026] S203, feeding the concrete blocks into a belt conveyor and removing ferromagnetic impurities through a ferromagnetic impurity separation device;

[0027] S204, finally sorting non-ferromagnetic impurities in the concrete blocks at the end of the belt conveyor.

[0028] In some embodiments, in S30, the soaking of the concrete blocks to a saturated state comprises:

[0029] Transferring the concrete blocks into a soaking pool to ensure complete immersion in water;

[0030] Continuously soaking the concrete blocks until a saturated state is reached;

[0031] Transferring the saturated concrete blocks out of the soaking pool for subsequent steps.

[0032] In some embodiments, the determination of the saturated state can be carried out as follows:

[0033] Starting the weight monitoring element built-in the soaking pool at the initial moment of starting soaking the concrete blocks.

[0034] continuously monitoring the rate of change of the readings of the weight monitoring element;

[0035] when the rate of change tends to be stable to zero, it is determined that the concrete block has reached a saturated state.

[0036] In some embodiments, in S40, the multiple freeze-thaw cycles can be carried out as follows:

[0037] Start the refrigeration system to uniformly and rapidly reduce the temperature in the freeze-thaw cycle cabin to -40℃~-20℃, and maintain the frozen temperature for at least two hours to ensure that the pore water inside the concrete block forms ice crystal organization completely;

[0038] Turn off the refrigeration system, start the heating system or use the ambient temperature to naturally warm up, so that the ice crystal organization completely melts into water;

[0039] Repeat the above freezing and melting process multiple times until the concrete block is completely cracked.

[0040] In some embodiments, the complete cracking determination of the concrete block can be carried out as follows:

[0041] During the multiple freeze-thaw cycles, continuously operate the acoustic emission detection unit built-in the freeze-thaw cycle cabin, when the cracking acoustic energy inside the concrete block detected by it tends to be stable, it is determined to be completely cracked.

[0042] In some embodiments, the concrete block after secondary crushing and cracking includes:

[0043] Put the concrete block into the secondary crushing device to make it crack along the internal microcracks to obtain concrete materials with different particle sizes.

[0044] In some embodiments, in S60, the classification and recovery of the concrete materials according to particle size includes:

[0045] Put the concrete materials into the multi-layer vibrating screen through the feeding port, and the multi-layer vibrating screen at least includes upper layer screen, middle layer screen and bottom layer screen arranged from top to bottom;

[0046] Wherein, the aperture of the upper layer screen is 25mm, the aperture of the middle layer screen is 5mm, and the aperture of the bottom layer screen is 1mm;

[0047] Separate the concrete materials through the multi-layer vibrating screen into:

[0048] Coarse aggregate with particle size greater than 25mm;

[0049] High-quality recycled coarse aggregate with particle size between 5mm and 25mm;

[0050] recycled fine aggregate with a particle size of 1mm to 5mm; and

[0051] a mortar slurry mixture with a particle size of less than 1mm.

[0052] The concrete waste recycling system based on freeze-thaw cycle cracking for realizing the above method specifically comprises:

[0053] The closed transportation carrier is internally provided with a positioning system and a weight monitoring element, and is used for optimizing a logistics transportation route, counting material throughput, and realizing traceability management.

[0054] The pretreatment subsystem comprises, in sequence, a feeding device, a primary crushing device, a primary screening device, a ferromagnetic impurity separation device, and a sorting device, the primary crushing device is used for receiving the concrete waste unloaded from the closed transportation carrier, and the devices of the pretreatment subsystem are connected through belt conveyors to form a material transmission path.

[0055] The soaking pool is provided with an aeration pipe and is used for soaking the concrete blocks treated by the pretreatment subsystem and intermittently releasing microbubbles to disturb the water body during the soaking process, so as to accelerate water absorption and saturation of the concrete blocks.

[0056] The freeze-thaw cycle cabin is used for performing multiple freeze-thaw cycle treatments on the concrete blocks in the saturated state, so that the concrete blocks are fully cracked.

[0057] The secondary crushing device is used for crushing the concrete blocks with a significantly reduced structural strength after freeze-thaw cracking.

[0058] The screening device is connected to the discharge port of the secondary crushing device and is provided with multiple replaceable screens and is used for screening aggregates according to different particle size requirements.

[0059] The concrete blocks in the saturated state are placed in a freeze-thaw environment, multiple freeze-thaw cycle treatments are performed, mechanical crushing is avoided, and the concrete is more easily cracked.

[0060] The beneficial effects of the present application relative to the prior art are:

[0061] (1) Large crushing equipment is not required, the equipment wear is small, and the energy consumption is low.

[0062] (2) Environmentally friendly and pollution-free: almost no dust is generated during the entire process, the working environment is greatly improved, dust pollution and health hazards to operators are prevented.

[0063] (3) Low noise: high-noise strong mechanical impact is avoided, the main noise source is the refrigeration unit, and the noise is easy to isolate and control.

[0064] It should be understood that the implementation of any embodiment of the present application does not mean that all or part of the above beneficial effects are simultaneously achieved or achieved. BRIEF DESCRIPTION OF DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only exemplary, and those skilled in the art can also obtain other implementation drawings according to the provided drawings without creative labor.

[0066] The structures, proportions, sizes, etc. shown in the specification are only used to cooperate with the content disclosed in the specification, to be understood and read by those skilled in the art, and are not used to limit the limiting conditions of the implementation of the present application, so they do not have technical substantive significance. Any modification of structure, change of proportion relationship or adjustment of size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0067] Figure 1 The flowchart of the concrete waste recycling method based on freeze-thaw cycle cracking provided by the embodiment of the present application;

[0068] Figure 2 The schematic diagram of the concrete waste recycling system based on freeze-thaw cycle cracking provided by the embodiment of the present application;

[0069] Figure 3 The schematic diagram of the soaking pool provided by the embodiment of the present application;

[0070] Markings in the figure: 1-open porosity, 2-closed porosity, 3-weight monitoring element.

[0071] The same or corresponding markings in the figure represent the same or corresponding parts. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear and obvious, the embodiments of the present application will be further described in detail below in combination with the embodiments and drawings. Here, the illustrative embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation of the present application.

[0073] In the present application, unless specifically defined and limited otherwise, the terms "mounting", "connected", "connection", "fixed", and the like, should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements or interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0074] It should be understood that the terms "comprising / including", "consisting of" or any other variant thereof are intended to cover non-exclusive inclusion, so that the product, device, process or method including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such product, device, process or method. Without more limitation, the elements defined by the statement "comprising / including", "consisting of" do not exclude the presence of other identical elements in the product, device, process or method comprising the elements.

[0075] It should also be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices, components or structures referred to must have a particular orientation, be constructed or operated in a particular orientation, and cannot be understood as a limitation on the present application.

[0076] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0077] Referring to Figure 1 As shown, according to the embodiment of the present application, a concrete waste recycling method based on freeze-thaw cycle cracking is provided, which mainly comprises: preliminarily sorting the concrete waste of the construction site and transporting it to the recycling point; preliminarily crushing the concrete waste to form concrete blocks with appropriate size, while separating impurities; removing foreign matter attached to the surface of the concrete blocks and soaking them to saturation; placing the saturated concrete blocks into a freeze-thaw cycle cabin to promote their cracking through multiple freeze-thaw cycles; secondary crushing the cracked concrete blocks to disperse them into concrete materials of different particle sizes; and grading and recycling the concrete materials according to particle size.

[0078] The various steps of the analysis method are described in detail below in connection with preferred embodiments and specific diagrams.

[0079] Referring to Figure 2 The concrete waste recycling system based on freeze-thaw cycle cracking on which the embodiment relies mainly includes a closed transport carrier, a pretreatment subsystem, an immersion pool, a freeze-thaw cycle cabin, a secondary crushing device, and a screening device. The following is described taking this system as an example, but it should be understood that this system is obviously not the only form and should not be interpreted as a limitation on the analysis method of the embodiment of the present application.

[0080] S10, the concrete waste of the construction site is preliminarily sorted and transported to the recycling point.

[0081] Specifically, the construction waste generated at the construction site usually includes large pieces of concrete waste (such as beam column fragments generated by floor demolition, small pieces of waste generated by wall demolition) and other waste (such as plastic, wood, fabric), before being concentrated for recycling, the large pieces of concrete waste need to be separated from them (which can be manually sorted). Preferably, the embodiment uses a small sorting device, such as a mobile mud separator (disc screen), to sort construction waste on site. In the embodiment, the small sorting device is provided with a feed inlet and a discharge outlet, the discharge outlet is adjacent to the closed transport carrier and maintains a certain height difference with it, so that the concrete blocks can be automatically thrown into the closed transport carrier from the discharge outlet under the action of gravity. Preferably, the closed self-unloading truck is selected as the closed transport carrier in the embodiment, during the sorting process, the workers throw the construction waste into the feed inlet, the large pieces of concrete waste after sorting are thrown into the closed self-unloading truck compartment through the discharge outlet, and after full load, the transportation of the concrete waste is carried out.

[0082] Preferably, the closed self-unloading truck used in the embodiment is also provided with anti-sticking and dust-proof measures, specifically, the compartment is made of high-strength steel plate, and the surface is coated with an anti-sticking coating to prevent wet concrete from sticking to the compartment box. Further, the top of the compartment is provided with a closed tarpaulin or cover plate, which is laid on the surface of the concrete blocks after full load, to ensure that no dust is dispersed or cement is leaked during transportation, so as to meet the requirements of environmental protection regulations on the transportation of construction waste.

[0083] Further, the closed self-unloading truck also has a GPS satellite signal positioning system and a weight monitoring element, which transmit transportation data information to a central control system in real time, and output an optimal logistics route and calculate material throughput after intelligent algorithm processing, and perform traceability management. It is easy to understand that the GPS satellite signal positioning system and the weight monitoring element can obtain position information and axle load information of the closed self-unloading truck in real time, and assist the closed self-unloading truck to flexibly adjust the transportation route while avoiding weight limit sections, maximize the transportation efficiency, and realize digital monitoring and green transportation of material flow, thereby laying a foundation for stable feeding for subsequent processing.

[0084] S20, the concrete waste is preliminarily crushed to form concrete blocks with appropriate sizes, and impurities are separated.

[0085] The preliminary crushing of the concrete waste in the embodiment is completed by a pretreatment subsystem. Preferably, the pretreatment subsystem includes a belt conveyor, a feeder, a jaw crusher, a heavy-duty vibrating screen, a magnetic separator, and a manual sorting platform. The feeder, the jaw crusher, the heavy-duty vibrating screen, the magnetic separator, and the manual sorting platform are connected by the belt conveyor.

[0086] The preliminary crushing of the concrete waste can be performed as follows:

[0087] After the closed transportation carrier arrives at the recycling site, the concrete waste is first unloaded into the feeder inlet. Under the driving of the feeder, the concrete waste is uniformly conveyed to the jaw crusher inlet by the belt conveyor and is preliminarily crushed into concrete blocks with sizes meeting the requirements of the freeze-thaw cycle cabin feeding specifications. In the embodiment, the size of the concrete blocks is preferably controlled within 0.3 m.

[0088] The concrete blocks are conveyed from the jaw crusher outlet to the heavy-duty vibrating screen inlet by the belt conveyor. In the embodiment, a heavy-duty vibrating screen with one screen and a screen size of 0.1 m is preferably selected. When the system is operating, the oversize material on the screen is oversized concrete blocks, and the undersize material is mainly broken bricks, soil, and other attached construction impurities. A storage bin is arranged below the screen for storing the undersize material, which can also be separately recycled and processed.

[0089] The screened concrete blocks are conveyed to the magnetic separator by the belt conveyor. The device can efficiently remove ferromagnetic impurities such as steel bars and iron wires mixed in the concrete blocks. The separated ferromagnetic impurities are stored in the storage bin at the ferromagnetic material outlet of the magnetic separator, which can also be separately recycled and processed.

[0090] In addition, in order to improve the sorting purity, the end of the belt conveyor is also provided with a manual sorting platform for removing non-magnetic impurities such as plastics and wood, or a robot vision sorting system can be used to replace the manual sorting platform, further improving the automation level of the entire pretreatment step.

[0091] S30, removing foreign matters attached to the surface of the concrete block and soaking it to a saturated state.

[0092] The pretreated concrete block is manually transported to a soaking operation room. In the embodiment, the soaking operation room is provided with an operation platform and a soaking device. Preferably, the soaking device is a large-volume soaking pool, and the bottom of the soaking pool is provided with a weight monitoring element 3 for monitoring the contact force between the concrete block and the pool bottom surface. In addition, the soaking pool is also provided with an aeration pipe, a water level and quality monitoring device, and a water circulation and filtration system to realize the full utilization of the water body.

[0093] Specifically, the concrete block is first placed on the operation platform, and the operator uses a high-pressure spraying device to wash the surface of the concrete block to completely remove the attached silt and impurities. This not only effectively reduces the pollution risk of the water body in the subsequent soaking pool, but also fully guarantees the water absorption performance of the block itself.

[0094] Preferably, the sprayed concrete block is placed in a corrosion-resistant metal basket by a grab bucket and then neatly stacked in the pool. After the concrete block is placed in the pool, the water level of the soaking pool is observed to ensure that all the concrete blocks are completely immersed in the water body. In the embodiment, a small amount of non-ionic surfactant is added to the water body based on tap water to reduce the surface tension of the water body and enhance its penetration ability and rate into the fine cracks and pores of the concrete. It should be noted that the grab bucket is only a preferred exemplary transfer method for transferring the concrete block, and other conventional material transfer methods such as a crane can also be used.

[0095] Further, in order to accelerate the replacement process of the air in the pores of the concrete block and the water body, the aeration pipe at the bottom of the soaking pool intermittently releases micro-bubbles during the soaking period. The micro-bubbles can drive the water flow in the pores of the concrete block by agitating the water body on one hand, and form a gas-water-solid three-phase composite flow channel in cooperation with the surfactant on the other hand, effectively breaking through the air resistance limitation in the pores of the concrete and significantly improving the penetration efficiency of the water into the interior.

[0096] In the embodiment, an exemplary saturated determination method for the concrete block is provided:

[0097] Referring to Figure 3 When the concrete block is placed in the soaking pool, the concrete block is subjected to a downward gravity G and an upward buoyancy F in the vertical direction v , and an upward contact force F N, the three constitute the following formula shown in the balance relationship:

[0098] G=F v +F N

[0099] Wherein:

[0100] G=mg

[0101]

[0102] In the formula:

[0103] m is the mass of the concrete block, g is the acceleration of gravity, is the density of the water body in the soaking pool, is the volume of the concrete block in the water body in the soaking pool.

[0104] From the above formula, F N is essentially the difference between the gravity and the buoyancy of the concrete block. At the initial moment when the concrete block begins to soak, the internal closed pore 2 has not been infiltrated by the water body, and the mass part m is only composed of the solid part of the concrete block; after the concrete block is soaked to the saturated state, the mass part m is composed of the solid part and the water part in the closed pore 2, and its mass shows an increasing trend during the soaking process. In an aspect, at the initial moment of soaking, is the volume of the concrete block itself, and after the concrete block is soaked to the saturated state, the open pore 1 and the closed pore 2 are both filled with water, and the saturation of the outer pore makes decrease, and the water in the closed pore 2 is not connected with the water in the soaking pool, that is, it does not provide additional buoyancy, so the buoyancy F v shows a decreasing trend during the soaking process. In summary, F N will increase with the changes of G and F v during the soaking process, and when the concrete block is soaked to the saturated state, the change stops immediately, so by monitoring the change rate of the contact force F v between the concrete block and the bottom surface of the soaking pool, the soaking state of the concrete block can be effectively determined, that is, when the change rate of F v stably tends to zero, it is determined that the concrete block has been soaked to the saturated state. In this embodiment, the weight monitoring element 3 is arranged on the bottom of the soaking pool, and it is easy to understand that the weight reading of the weight monitoring element 3 substantially reflects the contact force F v between the concrete block and the bottom surface of the soaking pool, so the soaking state of the concrete block can be grasped in real time by the change rate of the weight reading of the weight monitoring element 3.

[0105] S40, the saturated concrete block is placed in a freeze-thaw cycle chamber, and is cracked by multiple freeze-thaw cycles.

[0106] Preferably, after the concrete blocks reach saturation, the metal cages with the concrete blocks inside are lifted out of the soaking pool using a grab bucket, and the concrete blocks are manually transferred to the freeze-thaw cycle device.

[0107] Preferably, the freeze-thaw cycle cabin in this embodiment is a large heat-insulating and airtight cabin, and the cabin wall adopts a multi-layer composite structure composed of an outer shell and an inner liner. The space between the outer shell and the inner liner is filled with a heat insulation material such as polyurethane foam to effectively insulate heat exchange between the inside and outside of the cabin and ensure energy airtightness. The refrigeration system in the cabin can maintain the temperature inside the cabin at a low-temperature environment of -40°C to -20°C, and the control system can accurately adjust the cooling rate to avoid overcooling of the surface of the concrete blocks to form an insulating layer. The built-in heating system is based on the principle of microwave heating and can efficiently melt the ice crystal organization inside the concrete blocks. When the ice crystals melt, significant thermal stress is generated on the pore walls of the concrete blocks, causing the blocks to suffer strong fatigue damage. This process superimposes fatigue action on the basis of frost heaving force damage, promotes the concrete blocks to be fully and quickly broken, and significantly shortens the freeze-thaw cycle processing period. Preferably, the cabin is also provided with a low-temperature-resistant conveyor and an intelligent temperature sensing system, and the whole freeze-thaw process is controlled by a PLC program, which can automatically execute multiple cycles of “feeding-freezing-microwave melting” until the built-in acoustic emission detection system detects that the acoustic energy of the internal cracking of the blocks tends to be stable, and determines that the cracking is complete, and automatically discharges. A condensate water collection tank is arranged at the bottom of the cabin, and the collected condensate water is transported to the saturated water absorption module through a pipeline to realize the recycling of water resources.

[0108] In this embodiment, the operation process of the concrete blocks in the freeze-thaw cycle cabin can be carried out as follows:

[0109] After the concrete blocks enter the cabin, first start the refrigeration system to uniformly and quickly lower the temperature in the cabin to -40°C, and after cooling, keep the temperature for a period of time to ensure that the pore water inside the concrete blocks completely forms ice crystal organization. After sufficient freezing, the ice crystal organization expands by 9% compared to the original volume of the pores, and the pore walls and micro-cracks inside the concrete blocks are in a high stress state due to the expansion of the ice crystal organization.

[0110] Turn off the refrigeration system and start the heating system to quickly melt the ice crystal organization inside the concrete blocks under the action of microwaves, superimpose thermal stress and fatigue stress on the basis of frost heaving stress, and accelerate the expansion of micro-cracks; after the ice crystal organization is completely melted, the internal stress of the concrete blocks is released synchronously, but the micro-cracks generated in this freeze-thaw process are plastic deformation that cannot be restored, that is, the concrete blocks have undergone irreversible cracking and damage.

[0111] Repeat the above freezing-melting process until the acoustic emission detection system built in the cabin detects that the acoustic energy of the internal cracking of the blocks tends to be stable, determines that the cracking is complete, and automatically discharges.

[0112] It should be noted that the microwave heating method of the heating system in this embodiment is a preferred scheme, and of course, electric heating or natural ambient temperature recovery can also be used. However, the additional thermal stress and fatigue stress damage of microwave heating can effectively improve the freezing and thawing efficiency of the freezing and thawing cycle cabin, which is difficult to achieve by other conventional heating methods.

[0113] S50, the concrete blocks after secondary crushing and cracking are dispersed into concrete materials of different particle sizes.

[0114] After the freezing and thawing cycle, the internal structure of the concrete blocks is fully cracked, the structure tends to be loose, and the strength is also greatly reduced. At this stage, the secondary crushing device does not need to use traditional high-energy consumption and high-wear crushing equipment, and only needs a small crushing device (such as a roller crusher) to meet the requirements. Through the extrusion and shearing action of the device, the concrete blocks can be easily separated / broken along the existing microcracks, rather than "broken", so the energy consumption is significantly reduced.

[0115] Specifically, the concrete blocks after the freezing and thawing cycle are automatically transmitted to the secondary crushing operation room, the surface of which is provided with a closed dust cover, the feeding port and the discharging port of which are respectively connected with the discharging port of the upstream freezing and thawing cycle cabin and the feeding port of the downstream screening device, and the middle part is formed into a closed material flow through the roller crusher. The concrete blocks enter the secondary crushing operation room from the discharging port of the freezing and thawing cycle cabin, are conveyed to the roller crusher by the belt conveyor, are dispersed into concrete materials of different particle sizes under the action of the roller crusher, and then are transmitted to the feeding port of the screening device by the belt conveyor for subsequent screening operation. In addition, the dust cover is directly connected with the central dust collection pipeline at the top, and is connected with a bag dust collector to efficiently adsorb dust during the secondary crushing operation and ensure the cleanliness of the workshop environment.

[0116] S60, the concrete materials are graded and recovered according to the particle size.

[0117] In this embodiment, a multi-layer vibrating screen is preferably used as the screening device, and the grading and recovery operation of the concrete materials based on the device can be performed according to the following steps:

[0118] The screen mesh aperture is set according to the target product grade, and in this embodiment, the screen mesh apertures of the layers are exemplarily configured as 25mm for the upper layer, 5mm for the middle layer, and 1mm for the bottom layer; this configuration can separate the concrete materials into coarse aggregates greater than 25mm (which can be returned to the final crusher for secondary crushing), high-quality recycled coarse aggregates of 5-25mm, recycled fine aggregates (coarse sand) of 1-5mm, and mortar slurry mixture less than 1mm.

[0119] The coarse aggregate, high-quality recycled coarse aggregate and fine aggregate are directly dropped into the bunker for packaging; for the mortar slurry, it can flow into the multi-stage sedimentation tank, and is preliminarily concentrated through gravity settling, and the concentrated mortar is pumped into a centrifuge to realize solid-liquid separation, and the wet fine sand separated out is dried to obtain sand particles, which can be mixed into the ingredients and calcined to obtain recycled cement, and the wastewater generated by centrifugation enters the water treatment system, and after coagulation, flocculation, sedimentation and ph neutralization, the clear liquid can be used for the saturated water absorption module. The finally generated recycled products can be used to prepare recycled concrete or road base materials of different grades, and complete the green conversion from construction waste to construction resources.

[0120] From the above description, it can be seen that the recycling method of the present application can be summarized as follows: first, the concrete waste on the construction site is preliminarily sorted, and is transported to the recycling point along the optimal route through a closed transport carrier; second, the concrete waste is preliminarily crushed to form concrete blocks of appropriate size, and at the same time, ferromagnetic impurities and non-ferromagnetic impurities are sequentially separated through a ferromagnetic impurity separation device and manual sorting operation; third, after removing surface foreign matter through high-pressure spraying, the concrete blocks are immersed in a soaking pool, and the micro-bubbles in the pool and the non-ionic surfactant cooperate to promote the saturation process of the concrete blocks, and at the same time, the pool bottom weight monitoring element 3 is used to observe the block weight change rate in real time, and when the change rate stabilizes and approaches zero, it is determined that the soaking is complete. Fourth, the saturated concrete blocks are placed in a freeze-thaw cycle cabin, and the freeze-thaw cycle operation is performed cyclically, and when the acoustic emission detection system built in the freeze-thaw cycle cabin detects that the internal cracking acoustic energy of the concrete blocks tends to be stable, the system determines that the damage is complete, and automatically completes the discharge; fifth, the second crushed and cracked concrete blocks are dispersed into concrete materials of different particle sizes; sixth, according to the recycling requirements, a screening device screen is set, and the concrete materials are graded and recycled according to the particle size. The recycling method of the present application and the concrete recycling system relying on it use freeze-thaw cycle to damage the microstructure of concrete, induce microcrack expansion and realize macroscopic cracking, achieve clean treatment effect with low dust and low loss, and promote the green development of the construction waste recycling industry.

[0121] It is easy for those skilled in the art to understand that the above-mentioned preferred schemes can be freely combined and superimposed without conflict.

[0122] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for recycling concrete waste based on freeze-thaw cycle cracking, characterized by, The method comprises the following steps: S10, preliminary sorting and separating construction waste from other waste to obtain concrete waste and transporting the concrete waste to a recycling point; S20, preliminary crushing and separating the concrete waste to form concrete blocks with appropriate sizes and further separating fine impurities; S30, removing foreign matter attached to the surface of the concrete blocks and soaking the concrete blocks to a saturated state; S40, placing the concrete blocks into a freeze-thaw cycle cabin to promote the cracking of the concrete blocks through multiple freeze-thaw cycles; S50, secondary crushing and cracking the concrete blocks to disperse the concrete blocks into concrete materials with different particle sizes; S60, grading and recycling the concrete materials according to the particle sizes.

2. The freeze-thaw cycle based concrete waste recycling method according to claim 1, wherein, In S10, the preliminary sorting and separating construction waste from other waste to obtain concrete waste and transporting the concrete waste to a recycling point comprises the following steps: establishing a temporary classification and stacking point at the demolition site; carrying out the preliminary sorting of the concrete waste by manual or small machinery; sequentially loading the sorted concrete waste into a closed transport carrier; transporting the closed transport carrier to the recycling point after the closed transport carrier is fully loaded.

3. The freeze-thaw cycle based concrete waste recycling method as claimed in claim 1 wherein, In S20, the preliminary crushing and separating the concrete waste to form concrete blocks with appropriate sizes and further separating fine impurities comprises the following steps: S201, uniformly feeding the concrete waste into a primary crushing device to obtain primary crushed materials; S202, then feeding the primary crushed materials into a heavy-duty vibrating screen to separate large-sized concrete blocks; S203, feeding the concrete blocks into a belt conveyor and removing ferromagnetic impurities through a ferromagnetic impurity separation device; S204, finally, sorting non-ferromagnetic impurities in the concrete blocks at the end of the belt conveyor.

4. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, characterized by, In S30, the soaking of the concrete blocks to a saturated state comprises the following steps: transferring the concrete blocks into a soaking pool to ensure that the concrete blocks are completely immersed in water; continuously soaking the concrete blocks until the concrete blocks reach a saturated state; transferring the saturated concrete blocks out of the soaking pool for subsequent steps.

5. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, characterized by, The determination of the saturated state can be carried out in the following manner: starting the weight monitoring element built-in the soaking pool at the initial moment when the concrete blocks start to be soaked; continuously monitoring the reading change rate of the weight monitoring element; when the change rate tends to be zero, it is determined that the concrete blocks have reached a saturated state.

6. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, wherein, In S40, the multiple freeze-thaw cycles can be carried out in the following manner: starting a refrigeration system to uniformly and rapidly reduce the temperature in the freeze-thaw cycle cabin to -40℃~-20℃ and maintain the frozen temperature for at least two hours to ensure that the pore water inside the concrete blocks completely forms ice crystal organization; turning off the refrigeration system and starting a heating system or using the ambient temperature to naturally warm up to completely melt the ice crystal organization into water; repeating the above freezing and melting processes multiple times until the concrete blocks are completely cracked.

7. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, wherein, The determination of the complete cracking of the concrete blocks can be carried out in the following manner: continuously operating the acoustic emission detection unit built-in the freeze-thaw cycle cabin during the multiple freeze-thaw cycles, and when the acoustic emission energy detected by the acoustic emission detection unit tends to be stable, it is determined that the concrete blocks are completely cracked.

8. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, wherein, In S50, the concrete blocks after secondary crushing and cracking include: The concrete blocks are put into a secondary crushing device to crack along the internal micro-cracks to obtain concrete materials with different particle sizes.

9. The freeze-thaw cycle-based disintegration method for concrete waste recycling according to claim 1, wherein, In S60, the concrete materials are classified and recovered according to particle sizes, including: The concrete materials are fed into a multi-layer vibrating screen through a feeding port, and the multi-layer vibrating screen includes at least an upper layer screen, a middle layer screen and a bottom layer screen arranged from top to bottom. The upper layer screen has a pore size of 25 mm, the middle layer screen has a pore size of 5 mm, and the bottom layer screen has a pore size of 1 mm. The concrete materials are separated by the multi-layer vibrating screen into: Coarse aggregate with a particle size greater than 25 mm; High-quality recycled coarse aggregate with a particle size between 5 mm and 25 mm; Recycled fine aggregate with a particle size between 1 mm and 5 mm; and Mortar slurry mixture with a particle size less than 1 mm.

10. A freeze-thaw cycle based concrete waste recycling system as claimed in any one of claims 1 to 9, wherein, The system includes: A closed transportation carrier with a positioning system and a weight monitoring element for optimizing logistics transportation routes, calculating material throughput and achieving traceability management; A pretreatment subsystem including a feeding device, a primary crushing device, a primary screening device, a ferromagnetic impurity separation device and a sorting device connected in sequence, the primary crushing device being used to receive concrete waste unloaded from the closed transportation carrier, and the devices of the pretreatment subsystem being connected by belt conveyors to form a material transmission path; A soaking pool provided with an aeration pipe for soaking the concrete blocks treated by the pretreatment subsystem and intermittently releasing micro-bubbles to disturb the water body during the soaking process to accelerate the water absorption and saturation of the concrete blocks; A freeze-thaw cycle cabin for multiple freeze-thaw cycle treatments of the concrete blocks in a saturated state to fully crack them; A secondary crushing device for crushing the concrete blocks with significantly reduced structural strength after freeze-thaw cracking; A screening device connected to the discharge port of the secondary crushing device and equipped with multiple replaceable screens for screening aggregates according to different particle size requirements.

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