Modified recycled aggregate and preparation method and production device thereof

Abstract

This invention belongs to the field of building materials technology, specifically disclosing a modified recycled aggregate, its preparation method, and production apparatus. The preparation method of the modified recycled aggregate includes the following steps: first immersing the recycled aggregate in a nano-silica solution while setting an electric field in the solution; removing the nano-silica solution and immersing it in a magnesium oxide solution; removing the magnesium oxide solution and immersing the recycled aggregate in a second nano-silica solution, heating the solution to 40–95°C, thus obtaining the modified recycled aggregate. This invention also provides a production apparatus for the modified recycled aggregate, the modified recycled aggregate itself, and recycled aggregate concrete. The modification cycle of the preparation method of this invention is short, significantly improving production efficiency and ensuring industrial production. The modified recycled aggregate prepared by this invention significantly reduces the water absorption rate and crushing index of the recycled aggregate, and increases its apparent density, showing excellent application prospects.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a modified recycled aggregate, its preparation method, and production apparatus. Background Technology

[0002] Recycled aggregates generally refer to mixtures made from concrete, mortar, gravel, or bricks and tiles from construction waste. Due to factors in the formation process of recycled aggregates, they have high internal porosity, numerous microcracks, and many interfaces between old and new aggregates. They also suffer from high water absorption, poor strength, and poor interfacial properties, thus limiting their high-value applications. Some related technologies utilize recycled aggregate modifiers to effectively fill internal voids, repair microcracks, and improve the performance of recycled aggregates. For example, Chinese patent "201210261716.8" soaks recycled aggregate in a 10-40 wt% nano-silica hydrocolloid for more than 5 days, resulting in an increase in the specific gravity and a decrease in water absorption of the recycled aggregate, effectively improving its performance. Chinese patent "202310412375.8" uses an inorganic strengthening-organic modification mechanism combined with stepwise curing methods to sequentially strengthen the recycled aggregate with inorganic polymers and then with organic polymers, achieving a composite strengthening effect that can significantly reduce the water absorption rate of the recycled aggregate. Chinese patent "201711056033.8" mixes Bacillus spores H4 with a mineralization culture solution to obtain a mixed culture solution, and sprays the recycled aggregate with the mineralization culture solution for 10-35 days to obtain strengthened recycled aggregate, which significantly reduces the water absorption coefficient and water absorption rate of the recycled aggregate.

[0003] However, in some current technical solutions for modifying and strengthening recycled aggregates, the strengthening cycle of recycled aggregates ranges from 15 hours to several tens of days. The long strengthening cycle makes it difficult to meet the needs of large-scale and batch industrial production. Some technical solutions are still in the laboratory stage, with low strengthening efficiency and high production costs, which greatly restricts the process of high-value utilization of recycled aggregates from construction waste.

[0004] Therefore, in view of the problems existing in the above-mentioned related technical solutions, there is an urgent need for a new method for modifying and strengthening recycled aggregates to achieve the goals of accelerating the modification cycle, improving strengthening efficiency, and reducing production costs. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for preparing modified recycled aggregate. The modified recycled aggregate preparation method of this invention has a short modification cycle, significantly reduces aggregate soaking time, improves production efficiency, and provides a guarantee for the industrial production of modified recycled aggregate. Furthermore, the modified recycled aggregate prepared using the method of this invention significantly reduces the water absorption rate and crushing index of the recycled aggregate, and significantly increases its apparent density. The modified recycled aggregate prepared by the optimal scheme can meet the Class I standard requirements of the national standard GB / T 25177-2010, and even approaches the Class I standard requirements of natural crushed stone, showing excellent application prospects.

[0006] The present invention also provides a production apparatus for the preparation method of the above-mentioned modified recycled aggregate.

[0007] The present invention also provides a modified recycled aggregate.

[0008] The present invention also provides recycled aggregate concrete.

[0009] In a first aspect, the present invention provides a method for preparing modified recycled aggregate, comprising the following steps:

[0010] S1. The recycled aggregate is soaked in a nano-silica solution for the first time, and an electric field is set in the solution;

[0011] S2. Remove the nano-silica solution and soak it in magnesium oxide solution;

[0012] S3. Remove the magnesium oxide solution, then soak the recycled aggregate in a second nano-silica solution and heat it to 40-95℃ to obtain the modified recycled aggregate.

[0013] According to specific embodiments of the present invention, the method for preparing modified recycled aggregate provided by the present invention has at least the following beneficial effects: the modification cycle of the preparation process is short, improving production efficiency and providing a guarantee for the industrial production of modified recycled aggregate; in addition, the modified recycled aggregate prepared using the method of the present invention significantly reduces the water absorption rate and crushing index of the recycled aggregate, and significantly improves its apparent density. The modified recycled aggregate prepared by the optimal scheme can meet the Class I standard requirements of the national standard GB / T25177-2010, and even approach the Class I standard requirements of natural crushed stone; the two-step nano-silica solution soaking and the intermediate one-time magnesium oxide solution soaking treatment of the present invention achieve optimal modification and strengthening of recycled aggregate, and combined with some process treatments in the soaking modification process, further improves the modification and strengthening efficiency.

[0014] The recycled aggregate in this invention specifically refers to coarse aggregate with a particle size greater than 4.75 mm, formed by crushing and screening waste concrete and mortar.

[0015] In some embodiments of the present invention, the recycled aggregate described in step S1 is pre-soaked in water and then air-dried to surface dryness before being soaked in nano-silica solution.

[0016] In this invention, pre-soaking treatment fully wets the recycled aggregate, displacing alkaline substances within it, resulting in a weakly alkaline wastewater solution. Air drying allows the recycled aggregate to reach a surface-dry state under strong winds during transport, while maintaining internal moisture. This surface-dry state facilitates the rapid adhesion of nano-silica to the surface of the recycled aggregate, thus promoting its penetration into the interior.

[0017] In some preferred embodiments of the present invention, the pre-soaking time is 6 to 24 hours.

[0018] In some more preferred embodiments of the present invention, the pre-soaking time is 10 to 24 hours.

[0019] In some embodiments of the present invention, the concentration of the nano-silica solution used for the first nano-silica solution soaking in step S1 is 0.5 to 7 wt%.

[0020] In this invention, the nano-silica solution is prepared by mixing nano-silica powder with alkaline wastewater. The alkaline wastewater is the supernatant obtained by natural sedimentation of wastewater generated from pre-soaking for 8-12 hours. During the preparation of the nano-silica solution, the nano-silica powder and alkaline wastewater should be continuously stirred and dispersed during production to prevent agglomeration of the nano-silica. The stirring time is 2-3 hours.

[0021] In some preferred embodiments of the present invention, the concentration of the nano-silica solution used for the first nano-silica solution soaking in step S1 is 0.8–5 wt%.

[0022] In some more preferred embodiments of the present invention, the concentration of the nano-silica solution used for the first nano-silica solution soaking in step S1 is 1-3 wt%.

[0023] In some embodiments of the present invention, the soaking time of the first nano-silica solution in step S1 is 8 to 20 minutes.

[0024] In some preferred embodiments of the present invention, the soaking time of the first nano-silica solution in step S1 is 10 to 15 minutes.

[0025] In some embodiments of the present invention, the voltage of the electric field in step S1 is 150 to 550V.

[0026] In some preferred embodiments of the present invention, the voltage of the electric field in step S1 is 200 to 500 V.

[0027] In this invention, nano-silica contains surface chemical functional groups such as silicon-oxygen bonds (Si-O) and surface hydroxyl groups (-OH) in aqueous solution. The ionization of these surface functional groups generates silica clusters that create cavities near the surface of the nano-silica. In aqueous solution, these clusters are easily surrounded by negative ions and become negatively charged. Under high pH conditions, the surface hydroxyl groups lose H+ ions, enhancing their electronegativity. The nano-silica dispersion is alkaline wastewater, making the reaction system weakly alkaline and further enhancing the electronegativity of the nano-silica. Under the influence of an electric field, the nano-silica particles move rapidly in the opposite direction of the electric field, entering the interior of the recycled aggregate. Under the action of friction, they gradually fill the internal cracks and voids.

[0028] In some embodiments of the present invention, during the soaking process described in step S1, an ultrasonic generating system is also used to generate ultrasound to ensure uniform dispersion of nano-silica.

[0029] In some embodiments of the present invention, the concentration of the magnesium oxide solution used for immersion in the magnesium oxide solution in step S2 is 15% to 30 wt%.

[0030] In this invention, magnesium oxide is dissolved in water to form magnesium hydroxide, and the solution is alkaline. Under alkaline conditions, nano-silica inside the recycled aggregate reacts with calcium hydroxide inside the recycled aggregate to form a new CSH gel, which strengthens the interface between the old and new aggregates. At the same time, the nano-silica reacts with magnesium hydroxide to form magnesium silicate, which fills the cracks inside the aggregate and strengthens the aggregate.

[0031] In some preferred embodiments of the present invention, the concentration of the magnesium oxide solution used for immersion in the magnesium oxide solution in step S2 is 16% to 25 wt%.

[0032] In some more preferred embodiments of the present invention, the concentration of the magnesium oxide solution used for immersion in the magnesium oxide solution in step S2 is 20% to 25 wt%.

[0033] In some embodiments of the present invention, the soaking time of the magnesium oxide solution in step S2 is 8 to 20 minutes.

[0034] In some preferred embodiments of the present invention, the soaking time of the magnesium oxide solution in step S2 is 10 to 15 minutes.

[0035] In some embodiments of the present invention, the liquid is further agitated by a wind-driven turbulence system 602 during the soaking process described in step S2.

[0036] In some embodiments of the present invention, the concentration of the nano-silica solution used for the second nano-silica solution soaking in step S3 is 0.5-5 wt%.

[0037] In some preferred embodiments of the present invention, the concentration of the nano-silica solution used for the second nano-silica solution soaking in step S3 is 0.8–5 wt%.

[0038] In some more preferred embodiments of the present invention, the concentration of the nano-silica solution used for the second nano-silica solution soaking in step S3 is 1-3 wt%.

[0039] In some embodiments of the present invention, the soaking time of the second nano-silica solution in step S3 is 8 to 20 minutes.

[0040] In some preferred embodiments of the present invention, the soaking time of the second nano-silica solution in step S3 is 10 to 15 minutes.

[0041] In some embodiments of the present invention, the heating temperature in step S3 is set to 50–90°C.

[0042] In some embodiments of the present invention, during the soaking process described in step S3, the material is continuously stirred using a forward stirring rod and a reverse stirring rod.

[0043] In this invention, during the second soaking in the nano-silica solution, the reaction is accelerated by increasing the temperature of the reaction system and increasing the internal free energy of the reaction system. At the same time, the reaction is further accelerated by continuously disturbing the material and accelerating the flow of matter.

[0044] In the industrial production of modified aggregates, the key node affecting production efficiency is the modification stage. Other pretreatment, solution preparation, and curing steps are all carried out in the material silo and do not affect production efficiency. The total modification time of the modified and reinforced recycled aggregates in this invention is as short as 24 minutes, which can significantly reduce the aggregate modification soaking time, improve production efficiency, and provide a guarantee for the industrial production of modified recycled aggregates.

[0045] In some embodiments of the present invention, the method for preparing the modified recycled aggregate further includes a mist curing step S4: mist curing is performed using a 0.5-5 wt% nano silica solution for a mist curing time of 2-10 days.

[0046] In some embodiments of the present invention, the concentration of the nano-silica solution used for atomized curing is 0.8–5 wt%.

[0047] In some preferred embodiments of the present invention, the concentration of the nano-silica solution used for atomized curing is 1-3 wt%.

[0048] In some embodiments of the present invention, the atomization maintenance is intermittent maintenance, with each maintenance session lasting 10 to 15 minutes and the maintenance interval lasting 6 to 10 hours.

[0049] A second aspect of the present invention provides a production apparatus for the preparation method of the modified recycled aggregate described in the first aspect of the present invention, comprising a field traction module, an alkali enrichment module, and an accelerated reaction module.

[0050] In some embodiments of the present invention, the production apparatus further includes a pre-soaking module, a forced air feeding module, a sedimentation module, a solution conditioning tank, and a storage module.

[0051] In some embodiments of the present invention, the process flow of the production device is as follows: after the recycled aggregate is soaked in the pre-soaking module, wetted recycled aggregate and alkaline wastewater are obtained. The alkaline wastewater enters the sedimentation module for sedimentation and is ready for use. The recycled aggregate is loaded into the strong wind conveying module for surface drying treatment. At the same time, after the alkaline wastewater is precipitated in the sedimentation module, the supernatant is taken and dispersed together with nano-silica powder in the solution conditioning tank to obtain nano-silica solution. Under the operation of the concrete placing machine, the recycled aggregate enters the field traction module, and the nano-silica solution is introduced at the same time. The electric field generation system and the ultrasonic generation system are started to pull the nano-silica into the interior of the recycled aggregate. Under the action of the screw propeller, it enters the alkali enrichment module and is introduced with magnesium oxide solution conditioned by the solution conditioning tank for alkali enrichment soaking treatment. Under the action of the belt conveyor, it enters the accelerated reaction module through the concrete placing machine to accelerate the chemical reaction rate of the system. Finally, it enters the storage module for curing and is ready for sale.

[0052] In some embodiments of the present invention, the pre-soaking module includes a spraying system, a material stockpile, recycled aggregate, a water collection channel, and a water collection channel outlet. The spraying system is evenly distributed directly above the material stockpile, the recycled aggregate is stored inside the material stockpile, the water collection channel is located outside one side of the material stockpile, and the water collection channel outlet is located at one end of the water collection channel.

[0053] In some embodiments of the present invention, the forced-air feeding module includes a vibrating feeder, a forced-air system, a sealed housing, a screen conveyor, and a material distributor. The vibrating feeder is located above one end of the screen conveyor, the forced-air system is located directly above the screen conveyor and is enclosed by the sealed housing, which also seals the screen conveyor. The material distributor is located below one end of the screen conveyor, opposite to the vibrating feeder. The belt of the screen conveyor is composed of a flexible screen with a mesh size of 2-4 mm for draining residual water. The forced-air system ducts are evenly distributed throughout the screen conveyor, relying on airflow to dry the surface moisture of the recycled aggregate. The compressed air pressure is 1 MPa to 2.25 MPa. The sealed housing prevents residual water from splashing.

[0054] In some embodiments of the present invention, the field traction module includes a mixed liquid inlet, a stirring motor, an aggregate inlet, an electric field generating system, a propeller, an ultrasonic generating system, an aggregate outlet, and a residual liquid discharge outlet. The mixed liquid inlet is located on the upper side of one end of the main body of the field traction module; the stirring motor is located in the center of one end of the main body of the field traction module, on the same side as the mixed liquid inlet; the aggregate inlet is located directly above the main body of the field traction module; the electric field generating system is located around the internal cavity of the main body of the field traction module, with a dual electric field design, arranging two electric fields with perpendicular directions to each other. By changing the direction of the electric field, the migration efficiency of nano-silica is accelerated, quickly filling the interior of the recycled aggregate; the screw propeller is located in the internal cavity of the main body of the field traction module, spirally conveying the material; the ultrasonic generating system is located in the center of one end of the main body of the field traction module, opposite to the stirring motor, dispersing the nano-silica solution and preventing agglomeration; the aggregate outlet is located on the upper side of one end of the main body of the field traction module, opposite to the mixed liquid inlet; the residual liquid discharge outlet is located at the bottom of one side of the main body of the field traction module, used to recover the remaining solution and remove slag; the field traction module is a dual-module design to ensure continuous production and increase capacity.

[0055] In some embodiments of the present invention, the sedimentation module includes a primary sedimentation tank inlet, a primary sedimentation tank, a primary sedimentation tank outlet, a primary sedimentation tank sludge discharge outlet, a secondary sedimentation tank inlet, a secondary sedimentation tank, a secondary sedimentation tank outlet, and a secondary sedimentation tank sludge discharge outlet. The primary sedimentation tank inlet is located on one side of the upper end of the primary sedimentation tank; the primary sedimentation tank outlet is located on one side of the primary sedimentation tank and connected to the secondary sedimentation tank inlet; the primary sedimentation tank sludge discharge outlet is located on one side of the lower end of the primary sedimentation tank; the secondary sedimentation tank inlet is located on one side of the upper end of the secondary sedimentation tank and connected to the primary sedimentation tank outlet; the secondary sedimentation tank outlet is located on one side of the upper end of the secondary sedimentation tank; and the secondary sedimentation tank sludge discharge outlet is located on one side of the lower end of the secondary sedimentation tank. The primary and secondary sedimentation tanks are designed in series to ensure that the supernatant of the alkaline wastewater does not contain waste residue, so as not to affect the dispersion effect of nano-silica.

[0056] In some embodiments of the present invention, the solution conditioning tank includes a water inlet, a solid material inlet, a stirring motor, a stirring rod, and a solution outlet. The water inlet is located on one side of the upper end of the solution conditioning tank body; the solid material inlet is located on one side of the upper end of the solution conditioning tank body; the stirring motor is located in the center of the upper end of the solution conditioning tank body, with a stirring rate of 60-120 r / min; the stirring rod is located inside the solution conditioning tank body; the solution outlet is located at the lower end of one side of the solution conditioning tank body; the solution conditioning tank includes a nano-silica solution conditioning tank and a magnesium oxide solution conditioning tank, which are used for conditioning respectively.

[0057] In some embodiments of the present invention, the alkali-rich module includes a belt conveyor, a wind-driven turbulence system, an immersion tank, and a residual liquid recovery port. The belt conveyor passes through one end of the immersion tank, extends to the bottom, and exits upwards from the other end. The belt conveyor is made of an alkali-resistant corrosion-resistant material. The wind-driven turbulence system is located on both sides of the immersion tank and is evenly distributed in multiple layers. The compressed air pressure is 1 MPa to 2.25 MPa. By flushing the liquid, it forms turbulence and accelerates the chemical reaction of the system. The residual liquid recovery port is located at one end of the bottom of the immersion tank and is used for the recovery and reuse of magnesium oxide residual liquid.

[0058] In some embodiments of the present invention, the accelerated reaction module includes an alkali inlet, a stirring motor, an aggregate inlet, a forward stirring rod, a counter-rotating stirring rod, an auxiliary heat generator, an aggregate outlet, and a residual liquid recovery outlet. The alkali inlet is located on the upper side of one end of the accelerated reaction module body; the stirring motor is located in the center of one end of the accelerated reaction module body, with a stirring frequency of 30-60 r / min; the aggregate inlet is located at the top of the accelerated reaction module body; the forward stirring rod and the reverse stirring rod are coaxially connected and located inside the accelerated reaction module body. When the material needs to be stirred, the forward stirring rod and the reverse stirring rod move in opposite directions. When the material needs to be conveyed, the forward stirring rod and the reverse stirring rod move in the same direction (the reverse stirring rod moves 180° first), serving two purposes on one shaft; the auxiliary heat generator is located at one end of the accelerated reaction module body, opposite to the stirring motor. The heating pipes are evenly laid inside the accelerated reaction module body and are lower than the liquid level during soaking, with a heating rate of 10-15℃ / min; the aggregate outlet is located on the upper side of one end of the accelerated reaction module body; the residual liquid recovery port is located at one end of the accelerated reaction module body and is used for the recovery and reuse of the nano-silica solution.

[0059] In some embodiments of the present invention, the storage module includes a storage bin, an atomization system, and a discharge port. The atomization system is evenly distributed around the storage bin; the discharge port is located at the bottom of the storage bin and is used for material discharge, following a first-in, first-out (FIFO) principle.

[0060] In a third aspect, the present invention provides a modified recycled aggregate, which is prepared using the method for preparing modified recycled aggregate described in the first aspect of the present invention and the practical apparatus described in the second aspect of the present invention.

[0061] The modified recycled aggregate of the present invention is prepared using the method for preparing modified recycled aggregate described in the first aspect of the present invention, and therefore has at least all the beneficial effects of the method for preparing modified recycled aggregate described in the first aspect.

[0062] In a fourth aspect, the present invention provides a recycled aggregate concrete, the raw materials of which include: the modified recycled aggregate described in the third aspect of the present invention, cement, water, and sand.

[0063] In some embodiments of the present invention, the modified recycled aggregate of the third aspect of the present invention comprises recycled aggregates in two particle size ranges.

[0064] In some embodiments of the present invention, the modified recycled aggregate of the third aspect of the present invention includes recycled aggregate with a particle size range of 5 to 10 mm and recycled aggregate with a particle size range of 10 to 30 mm.

[0065] In some preferred embodiments of the present invention, the raw materials of the recycled aggregate concrete, by weight, include: 250-350 parts of recycled aggregate with a particle size range of 5-10 mm, 550-650 parts of recycled aggregate with a particle size range of 10-30 mm, 450-550 parts of cement, 130-170 parts of water, and 600-700 parts of sand.

[0066] In some more preferred embodiments of the present invention, the raw materials of the recycled aggregate concrete, by weight, include: 280-320 parts of recycled aggregate with a particle size range of 5-10 mm, 580-620 parts of recycled aggregate with a particle size range of 10-30 mm, 480-520 parts of cement, 140-160 parts of water, and 630-650 parts of sand.

[0067] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0068] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0069] Figure 1 This is a flowchart of the recycled aggregate production process of the present invention;

[0070] Figure 2 This is a schematic diagram of the pre-soaking module in the recycled aggregate production device of the present invention;

[0071] Figure 3 This is a schematic diagram of the forced air feeding module in the recycled aggregate production device of the present invention.

[0072] Figure 4 This is a cross-sectional view of the field traction module structure in the recycled aggregate production device of the present invention.

[0073] Figure 5 This is a top view of the field traction module structure in the recycled aggregate production device of the present invention.

[0074] Figure 6 This is a schematic diagram of the sedimentation module structure in the recycled aggregate production device of the present invention;

[0075] Figure 7 This is a schematic diagram of the solution conditioning tank in the recycled aggregate production apparatus of the present invention;

[0076] Figure 8 This is a schematic diagram of the alkali-rich module in the recycled aggregate production device of the present invention.

[0077] Figure 9 This is a cross-sectional view of the accelerated reaction module structure in the recycled aggregate production apparatus of the present invention;

[0078] Figure 10 This is a top view of the accelerated reaction module structure in the recycled aggregate production apparatus of the present invention;

[0079] Figure 11 This is a schematic diagram of the material storage module in the recycled aggregate production device of the present invention.

[0080] Figure reference numerals: 100-Pre-soaking module; 101-Spraying system; 102-Material stockpile; 103-Recycled aggregate; 104-Water collection channel; 105-Water collection channel drain outlet; 200-High-pressure air feeding module; 201-Vibrating feeder; 202-High-pressure air system; 203-Sealed box; 204-Screw conveyor; 205-Bulking machine; 300-Field traction module; 301-Mixed liquid inlet; 302-Agitator motor; 303-Aggregate inlet; 304-Electric field generating system; 305-Propeller; 306-Ultrasonic generating system; 307-Aggregate outlet; 308-Residual liquid discharge outlet; 400-Sedimentation module; 401-Primary sedimentation tank inlet; 402-Primary sedimentation tank; 403-Primary sedimentation tank outlet; 404-Primary sedimentation tank slag discharge outlet; 405 - Secondary sedimentation tank inlet; 406- Secondary sedimentation tank; 407- Secondary sedimentation tank outlet; 408- Secondary sedimentation tank slag discharge outlet; 500- Solution conditioning tank; 501- Water inlet; 502- Solid material inlet; 503- Stirring motor; 504- Stirring rod; 505- Solution outlet; 600- Alkali enrichment module; 601- Belt conveyor; 602- Wind-driven turbulent flow system; 603- Soaking tank; 604- Residual liquid recovery outlet; 700- Accelerated reaction module; 701- Alkali solution inlet; 702- Stirring motor; 703- Aggregate inlet; 704- Forward stirring rod; 705- Opposite stirring rod; 706- Auxiliary heat generator; 707- Aggregate outlet; 708- Residual liquid recovery outlet; 800- Storage module; 801- Storage silo; 802- Atomization system; 803- Outlet. Detailed Implementation

[0081] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0082] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0083] Example 1

[0084] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, the specific production steps are as follows:

[0085] (1) Take 100 parts of recycled aggregate and add it to the mixture. Figure 2 In the pre-soaking module 100 shown, tap water is used for pre-wetting and soaking for 12 hours via a spray system 101. After soaking, alkaline wastewater is discharged and collected through a collection channel 104. Figure 6 The precipitation module 400 shown is for later use;

[0086] (2) The pre-wetted recycled aggregate is transferred by a loading vehicle to Figure 3 In the strong air feeding module 200 shown, recycled aggregate enters the strong air system 202 through the vibrating feeder 201, with the air pressure set at 1.25MPa. It is then air-dried to surface dry on the screen conveyor and enters the material distribution machine 205 to be distributed.

[0087] (3) The alkaline wastewater collected in step (1) is settled in sedimentation module 400. Primary sedimentation is carried out in primary sedimentation tank 402 for 10 hours. The supernatant is transferred to secondary sedimentation tank 406 for secondary sedimentation for 10 hours. After sedimentation, the supernatant is taken for use.

[0088] (4) Add the supernatant obtained after the secondary precipitation in step (3) and nano-silica to the solution. Figure 7 In the solution preparation tank 500 shown, the final concentration of nano-silica was adjusted to 3wt%, and the mixture was stirred and dispersed for 2.5 hours to prepare a fully prepared nano-silica solution for later use.

[0089] (5) The air-dried recycled aggregate from step (2) is fed into the feeder. Figure 4 and Figure 5The field traction module shown is used to simultaneously inject the nano-silica solution obtained in step (4) until it is completely soaked; the electric field generating system 304 is started and the voltage is set to 200V. The electric field causes the nano-silica to enter the internal cracks and voids of the recycled aggregate. At the same time, the ultrasonic generating system 306 is started to ensure that the nano-silica is evenly dispersed. The soaking time is 10 minutes; the soaked recycled aggregate is transferred to the field traction module under the action of the screw propeller 305. Figure 8 The alkali-rich module 600 shown;

[0090] (6) Add tap water and magnesium oxide solid to solution conditioning tank 500 and stir to dissolve, forming a magnesium oxide solution with a final concentration of 25wt%, for later use;

[0091] (7) The recycled aggregate soaked in step (6) is fed into the soaking tank 603 via belt conveyor 601. At the same time, magnesium oxide solution is introduced until the soaking is complete. The liquid is disturbed under the action of wind turbulence system 602. The soaking time is 10 minutes. The soaked recycled aggregate is fed into the spreading machine via belt conveyor 601 to wait for spreading.

[0092] (8) The recycled aggregate after soaking in step (7) is fed into the concrete feeding machine. Figure 9 and Figure 10 The accelerated reaction module 700 shown simultaneously introduces a 3wt% nano-silica solution until complete soaking. The heat generator 706 is activated to heat the solution to 90°C. Under the action of the forward stirring rod 704 and the counter-rotating stirring rod 705, the material is continuously stirred. The soaking time is 10 minutes. The soaked recycled aggregate is then transferred through the forward stirring rod 704 and the counter-rotating stirring rod 705 to… Figure 11 The storage module 800 shown yields modified and reinforced recycled aggregate.

[0093] The structure of the production apparatus for preparing modified recycled aggregates according to the present invention will be described in conjunction with the process flow diagram and various schematic diagrams:

[0094] The soaking module 100 includes a spray system 101, a material storage yard 102, recycled aggregate 103, a water collection channel 104, and a water collection channel drain outlet 105. The spray system 101 is evenly distributed above the material storage yard 102. The recycled aggregate 103 is stored inside the material storage yard 102. The water collection channel 104 is located outside one side of the material storage yard 102, and the water collection channel drain outlet 105 is located at one end of the water collection channel 104.

[0095] The forced-air feeding module 200 includes a vibrating feeder 201, a forced-air system 202, a sealed housing 203, a screen conveyor 204, and a material placing machine 205. The vibrating feeder 201 is located above one end of the screen conveyor 204, and the forced-air system 202 is located directly above the screen conveyor 204 and is enclosed by the sealed housing 203. The sealed housing 203 also seals the screen conveyor 204. The material placing machine 205 is located below one end of the screen conveyor 204, opposite to the vibrating feeder 201. The belt of the screen conveyor 204 is composed of a flexible screen with a screen aperture of 2-4 mm for draining residual water. The forced-air system 202 has air ducts evenly distributed in the screen conveyor 204, relying on wind power to dry the surface moisture of the recycled aggregate. The compressed air pressure is 1 MPa to 2.25 MPa. The sealed housing 203 prevents residual water from splashing.

[0096] The field traction module 300 includes a mixed liquid inlet 301, a stirring motor 302, an aggregate inlet 303, an electric field generating system 304, a propeller 305, an ultrasonic generating system 306, an aggregate outlet 307, and a residual liquid discharge outlet 308. The mixed liquid inlet 301 is located on the upper side of one end of the main body of the field traction module 300. The stirring motor 302 is located in the center of one end of the main body of the field traction module 300, on the same side as the mixed liquid inlet 301. The aggregate inlet 303 is located directly above the main body of the field traction module 300. The electric field generating system 304 is located around the internal cavity of the main body of the field traction module 300, featuring a dual electric field design with two electric fields arranged perpendicular to each other. By changing the direction of the electric field, the migration efficiency of nano-silica is accelerated, and it quickly fills the interior of the recycled aggregate. The screw propeller 305 is located inside the cavity of the main body of the field traction module 300, and it conveys the material by screw. The ultrasonic generating system 306 is located in the middle of one end of the main body of the field traction module 300, opposite to the stirring motor 302, to disperse the nano-silica solution and prevent agglomeration. The aggregate discharge port 307 is located on the upper side of one end of the main body of the field traction module 300, opposite to the mixed liquid inlet 301. The residual liquid discharge port 308 is located at the bottom of one side of the main body of the field traction module 300, and is used to recover the remaining solution and discharge slag. The field traction module 300 is a dual-module design to ensure continuous production and improve capacity.

[0097] The sedimentation module 400 includes a primary sedimentation tank inlet 401, a primary sedimentation tank 402, a primary sedimentation tank outlet 403, a primary sedimentation tank sludge discharge outlet 404, a secondary sedimentation tank inlet 405, a secondary sedimentation tank 406, a secondary sedimentation tank outlet 407, and a secondary sedimentation tank sludge discharge outlet 408. The primary sedimentation tank inlet 401 is located on one side of the upper end of the primary sedimentation tank 402. The primary sedimentation tank outlet 403 is located on the upper side of the primary sedimentation tank 402 and is connected to the secondary sedimentation tank inlet 405. The slag discharge port of sedimentation tank 404 is located at the bottom of one side of primary sedimentation tank 402; the liquid inlet of secondary sedimentation tank 405 is located at the top of secondary sedimentation tank 406 and is connected to the liquid outlet of primary sedimentation tank 403; the liquid outlet of secondary sedimentation tank 407 is located at the top of secondary sedimentation tank 406; the slag discharge port of secondary sedimentation tank 408 is located at the bottom of one side of secondary sedimentation tank 406; the primary sedimentation tank 406 and secondary sedimentation tank 408 are designed in series to ensure that the supernatant of alkaline wastewater does not contain waste residue, so as not to affect the dispersion effect of nano-silica;

[0098] The solution preparation tank 500 includes a water inlet 501, a solid material inlet 502, a stirring motor 503, a stirring rod 504, and a solution outlet 505. The water inlet 501 is located on one side of the upper part of the solution preparation tank 500 body; the solid material inlet 502 is located on one side of the upper part of the solution preparation tank 500 body; the stirring motor 503 is located in the center of the upper part of the solution preparation tank 500 body, with a stirring speed of 60-120 r / min; the stirring rod 504 is located inside the solution preparation tank 500 body; the solution outlet 505 is located at the lower end of one side of the solution preparation tank 500 body; the solution preparation tank 500 includes a nano-silica solution preparation tank and a magnesium oxide solution preparation tank, which are prepared separately.

[0099] The alkali-rich module 600 includes a belt conveyor 601, a wind-driven turbulence system 602, an immersion tank 603, and a residual liquid recovery port 604. The belt conveyor 601 passes through one end of the immersion tank 603, descends to the bottom, and exits from the other end. The belt conveyor is made of alkali-resistant corrosion-resistant material. The wind-driven turbulence system 602 is located on both sides of the immersion tank 603, with multiple layers evenly distributed. The compressed air pressure is 1 MPa to 2.25 MPa. By flushing the liquid, it forms turbulence and accelerates the chemical reaction of the system. The residual liquid recovery port 604 is located at the bottom of the immersion tank 603 and is used for the recovery and reuse of magnesium oxide residual liquid.

[0100] The accelerated reaction module 700 includes an alkali inlet 701, a stirring motor 702, an aggregate inlet 703, a forward stirring rod 704, a reverse stirring rod 705, an auxiliary heat generator 706, an aggregate outlet 707, and a residual liquid recovery port 708. The alkali inlet 701 is located on the upper side of one end of the accelerated reaction module 700 body. The stirring motor 702 is located in the center of one end of the accelerated reaction module 700 body, with a stirring frequency of 30-60 r / min. The aggregate inlet 703 is located at the top of the accelerated reaction module 700 body. The forward stirring rod 704 and the reverse stirring rod 705 are coaxially connected and located inside the accelerated reaction module 700 body. When the material needs to be stirred, the forward stirring rod 704... 04 moves in the opposite direction to the counter-rotating stirring rod 705. When materials need to be conveyed, the forward stirring rod 704 moves in the same direction as the counter-rotating stirring rod 705 (the counter-rotating stirring rod 705 moves 180° first), serving two purposes with one shaft; the auxiliary heat generator 706 is located at one end of the main body of the accelerated reaction module 700, opposite to the stirring motor 702. The heating pipes are evenly laid inside the main body of the accelerated reaction module 700 and are lower than the liquid level during soaking. The heating rate is 10-15℃ / min; the aggregate outlet 707 is located on the upper side of one end of the main body of the accelerated reaction module 700; the residual liquid recovery port 708 is located at one end of the bottom of the main body of the accelerated reaction module 700 and is used for the recycling of nano-silica solution;

[0101] The storage module 800 includes a storage bin 801, an atomization system 802, and a discharge port 803; the atomization system 802 is evenly distributed around the storage bin 801; the discharge port 803 is located at the bottom of the storage bin 801 and is used for material discharge, with a first-in, first-out (FIFO) principle.

[0102] Example 2

[0103] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 1, except that: in step (8) of this embodiment, the concentration of nano silica is 1wt%, the solution is heated to 50°C by the heat generator 706, and the soaking time is 15min.

[0104] Example 3

[0105] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 1, except that: the concentration of the nano silica solution in step (4) of this embodiment is 2wt%, the soaking time in step (5) is 12min and the voltage is 350V, the concentration of the magnesium oxide solution in step (6) is 22wt%, the soaking time in step (7) is 12min, and the concentration of the nano silica in step (8) is 2wt%, the heat generator 706 heats the solution to 70℃ and the soaking time is 12min.

[0106] Example 4

[0107] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 1, except that: the concentration of the nano silica solution in step (4) of this embodiment is 1wt%, the soaking time in step (5) is 15min and the voltage is 500V, and the concentration of the magnesium oxide solution in step (6) is 20wt%.

[0108] Example 5

[0109] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 1, except that: in this embodiment, the soaking time in step (5) is 12 min and the voltage is 350V, the magnesium oxide solution concentration in step (6) is 22wt%, the soaking time in step (7) is 12 min, and the concentration of nano silica in step (8) is 2wt%, the solution is heated to 70°C by the heat generator 706, and the soaking time is 12 min.

[0110] Example 6

[0111] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (4) of this embodiment is 1 wt%.

[0112] Example 7

[0113] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (4) of this embodiment is 5wt%.

[0114] Example 8

[0115] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (4) of this embodiment is 7wt%.

[0116] Example 9

[0117] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (5) of this embodiment is 8 minutes.

[0118] Example 10

[0119] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (5) of this embodiment is 10 minutes.

[0120] Example 11

[0121] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (5) of this embodiment is 15 minutes.

[0122] Example 12

[0123] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the voltage in step (5) of this embodiment is 200V.

[0124] Example 13

[0125] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the voltage in step (5) of this embodiment is 500V.

[0126] Example 14

[0127] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of the magnesium oxide solution in step (6) of this embodiment is 16wt%.

[0128] Example 15

[0129] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of the magnesium oxide solution in step (6) of this embodiment is 18wt%.

[0130] Example 16

[0131] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of the magnesium oxide solution in step (6) of this embodiment is 20 wt%.

[0132] Example 17

[0133] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of the magnesium oxide solution in step (6) of this embodiment is 25 wt%.

[0134] Example 18

[0135] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (7) of this embodiment is 8 minutes.

[0136] Example 19

[0137] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (7) of this embodiment is 10 minutes.

[0138] Example 20

[0139] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (7) of this embodiment is 15 minutes.

[0140] Example 21

[0141] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (8) of this embodiment is 1 wt%.

[0142] Example 22

[0143] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (8) of this embodiment is 3wt%.

[0144] Example 23

[0145] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the concentration of nano-silica in step (8) of this embodiment is 5wt%.

[0146] Example 24

[0147] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (8) of this embodiment is 8 minutes.

[0148] Example 25

[0149] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (8) of this embodiment is 10 minutes.

[0150] Example 26

[0151] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that the soaking time in step (8) of this embodiment is 15 minutes.

[0152] Example 27

[0153] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that in step (8) of this embodiment, the heat generator 706 heats the solution to 40°C.

[0154] Example 28

[0155] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that in step (8) of this embodiment, the heat generator 706 heats the solution to 50°C.

[0156] Example 29

[0157] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 5, except that in step (8) of this embodiment, the heat generator 706 heats the solution to 90°C.

[0158] Example 30

[0159] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1As shown, this embodiment is basically the same as embodiment 3. The difference is that this embodiment adds a step (9) of atomization strengthening curing process on the basis of embodiment 3: the recycled aggregate in step (8) is stored in the storage module 800, and 2wt% nano silica solution is introduced into the atomization system 802. The recycled aggregate is atomized and strengthened through the atomization system 802. The total atomization curing time is 3 days, each atomization treatment is 12 minutes, and the interval between each atomization is 8 hours.

[0160] Example 31

[0161] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 30, except that the total atomization maintenance time of step (9) in this embodiment is 5 days.

[0162] Example 32

[0163] This embodiment provides a modified and strengthened production process for recycled aggregates, as shown in the process flow diagram below. Figure 1 As shown, this embodiment is basically the same as embodiment 30, except that the total atomization maintenance time of step (9) in this embodiment is 7 days.

[0164] Example 33

[0165] This embodiment provides concrete prepared using modified recycled aggregate. By mass, the concrete raw material composition is: 500 parts cement, 150 parts water, 642 parts sand, 300 parts modified recycled aggregate produced by the process of Example 3 using recycled aggregate with a particle size range of 5-10 mm, and 600 parts modified recycled aggregate produced by the process of Example 3 using recycled aggregate with a particle size range of 10-30 mm.

[0166] Example 34

[0167] This embodiment provides concrete prepared using modified recycled aggregate. By mass, the concrete raw material composition is: 500 parts cement, 150 parts water, 642 parts sand, 300 parts modified recycled aggregate produced by the process of Example 30 using recycled aggregate with a particle size range of 5 to 10 mm, and 600 parts modified recycled aggregate produced by the process of Example 30 using recycled aggregate with a particle size range of 10 to 30 mm.

[0168] Example 35

[0169] This embodiment provides concrete prepared using modified recycled aggregate. By mass, the concrete raw material composition is: 500 parts cement, 150 parts water, 642 parts sand, 300 parts modified recycled aggregate produced by the process of Example 31 using recycled aggregate with a particle size range of 5 to 10 mm, and 600 parts modified recycled aggregate produced by the process of Example 31 using recycled aggregate with a particle size range of 10 to 30 mm.

[0170] Example 36

[0171] This embodiment provides concrete prepared using modified recycled aggregate. By mass, the concrete raw material composition is: 500 parts cement, 150 parts water, 642 parts sand, 300 parts modified recycled aggregate produced by the process of Example 32 using recycled aggregate with a particle size range of 5 to 10 mm, and 600 parts modified recycled aggregate produced by the process of Example 32 using recycled aggregate with a particle size range of 10 to 30 mm.

[0172] Comparative Example 1

[0173] This comparative example provides the production of modified and strengthened recycled aggregates. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as those in Example 1. The omits steps are: the treatment in the alkali-rich module and the accelerated reaction module, namely steps (6), (7) and (8).

[0174] Comparative Example 2

[0175] This comparative example provides the production of modified and reinforced recycled aggregate. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as those in Example 1. The omits steps are: the processing in the field traction module and the accelerated reaction module, namely steps (5) and (8).

[0176] Comparative Example 3

[0177] This comparative example provides the production of modified and strengthened recycled aggregates. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as those in Example 1. The omits steps are: the treatment in the field traction module and the alkali-rich module, namely steps (5), (6) and (7).

[0178] Comparative Example 4

[0179] This comparative example provides the production of modified and strengthened recycled aggregates. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as those in Example 1. The omits step is: the processing in the field traction module, i.e., step (5).

[0180] Comparative Example 5

[0181] This comparative example provides the production of modified and strengthened recycled aggregates. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as those in Example 1. The omits steps are: the treatment in the alkali-rich module, i.e., steps (6) and (7).

[0182] Comparative Example 6

[0183] This comparative example provides a modified and reinforced production of recycled aggregate. Compared with Example 1, this comparative example omits some steps, while the other process steps are the same as in Example 1. The omits step is the processing in the accelerated reaction module, i.e., step (8).

[0184] Test Example 1

[0185] The modified recycled aggregates prepared in Examples 1-29 and Comparative Examples 1-6 were tested, and a blank control group of unmodified recycled aggregates from the same batch was set up. The performance of the modified recycled aggregates was tested using the test methods provided in the national standard GB / T 25177-2010 "Recycled Coarse Aggregate for Concrete". In order to better compare the examples and comparative examples, the examples and comparative examples were divided into 5 groups: A, B, C, D, and E. Group A consists of Example 1 and Examples 2-4 with adjusted preparation parameters; Group B consists of Comparative Examples 1-6, which are compared with the processing technology of one or two modules of the default field traction module, alkali-rich module, and accelerated reaction module of Example 1; Group C consists of Examples 5-13, which are used to explore the optimal parameters of each production process of the field traction module; Group D consists of Examples 14-20, which are used to explore the optimal parameters of each production process of the alkali-rich module; and Group E consists of Examples 21-29, which are used to explore the optimal parameters of each production process of the accelerated reaction module. The setting table of process parameters for each example and comparative example is shown in Table 1, and the test results are shown in Table 2.

[0186] Table 1. Process parameter settings for Examples 1-29 and Comparative Examples 1-6

[0187]

[0188]

[0189] Table 2 shows the performance test results of the modified recycled aggregates from Examples 1-34 and Comparative Examples 1-6, and the blank control.

[0190]

[0191]

[0192]

[0193] In the industrial production of modified aggregates, the key node affecting production efficiency is the modification stage. Other steps such as pretreatment, solution proportioning, and curing are carried out in the material silo and do not affect production efficiency. As can be seen from the various embodiments of the present invention, the total modification and strengthening time of the recycled aggregates in the key field traction module, alkali enrichment module, and accelerated reaction module of the present invention is within 45 minutes, and can be controlled as short as 24 minutes. This has high efficiency in industrial mass production.

[0194] The test results above show that, compared with the blank control group, the water absorption rate of Example 4 decreased by 49.46%, the crushing index decreased by 33.33%, and the apparent density increased by 5.05%; the water absorption rate of Example 3 decreased by 68.04%, the crushing index decreased by 55.56%, and the apparent density increased by 7.69%; the water absorption rate of Example 2 decreased by 72.68%, the crushing index decreased by 55.56%, and the apparent density increased by 8.79%; and the water absorption rate of Example 1 decreased by 77.14%, the crushing index decreased by 61.11%, and the apparent density increased by 10.33%. Test results show that using the method of the present invention to modify and strengthen recycled aggregates significantly improves the comprehensive performance of recycled aggregates. The modified recycled aggregate prepared in Example 4 meets the Class II standard requirements of the national standard GB / T25177-2010, the modified recycled aggregates prepared in Examples 2 and 3 meet the Class I standard requirements of the national standard GB / T25177-2010, and the modified recycled aggregate prepared in Example 1 even approaches the Class I standard requirements of natural crushed stone, achieving the best technical effect.

[0195] In Group B, Comparative Examples 1-6, lacking one or two of the key processing steps of the field traction module, alkali enrichment module, and accelerated reaction module in this invention, resulted in varying degrees of decline in the properties of the modified recycled aggregates compared to the examples, with only slight improvements compared to the blank control. Comparative Example 1, after soaking only in the field traction module, showed a slight decrease in water absorption, essentially unchanged crushing index, and a slight increase in apparent density, indicating that nano-silica entered the interior of the recycled aggregate but did not initiate a chemical reaction, resulting in limited performance improvement. Comparative Example 2, after soaking only in the alkali enrichment module, showed no change in water absorption or crushing index, but a slight increase in apparent density, indicating that the magnesium oxide solution only entered the interior of the recycled aggregate without a chemical reaction. Comparative Example 3, after soaking only in the accelerated reaction module, showed a slight decrease in water absorption, essentially unchanged crushing index, and no change in crushing index. The apparent density of the recycled aggregate in Comparative Example 4, after soaking only in the alkali-rich module and the accelerated reaction module, decreased water absorption, crushing index, and increased apparent density, indicating that the nano-silica partially entered the recycled aggregate but did not completely fill it. In an alkaline environment, the nano-silica accelerated the chemical reaction of the system with increasing temperature, resulting in a near-complete reaction and the formation of new CSH gel, thus improving the recycled aggregate's performance. However, some properties still need further improvement. Comparative Example 5, after soaking only in the field traction module and the accelerated reaction module, showed a decrease in water absorption, crushing index, and increased apparent density. Compared to Comparative Example 4, the water absorption of the recycled aggregate decreased slightly. In summary, this indicates that more nano-silica entered the recycled aggregate than in Comparative Example 4. While the nano-silica accelerated the chemical reaction with increasing temperature, the crushing index and apparent density did not change significantly, indicating incomplete reaction and insufficient formation of new CSH gel. Therefore, the recycled aggregate's performance was improved. However, there is still room for improvement in various performance parameters. In Comparative Example 6, the water absorption rate and crushing index of the recycled aggregate after soaking in the field traction module and the alkali-rich module decreased, while the apparent density increased. Compared with the data of Comparative Example 4, the water absorption rate of the recycled aggregate increased slightly. Combined with the data analysis of Comparative Example 5, it can be concluded that the chemical reaction of the system is accelerated in the alkaline environment of nano-silica, but the crushing index and apparent density do not change much, indicating that the reaction is incomplete and the amount of new CSH gel formed is insufficient. The performance of the recycled aggregate is improved, but there is still room for improvement in various performance parameters.

[0196] In Group C, comparing Examples 5 to 8, the water absorption rate of the recycled aggregate gradually decreased with increasing concentration of the nano-silica solution in the field traction module. Compared with the water absorption rate data of the blank control, the water absorption rate reduction rates of Examples 5 to 8 were 69.46%, 50.36%, 74.1%, and 78.93%, respectively. Therefore, the reduction was highest when the concentration of the nano-silica solution increased to 3 wt%, and then the reduction showed a decreasing trend. The crushing index and apparent density showed similar trends, so the higher the concentration of the nano-silica solution, the better. However, considering cost factors, choosing 1-3 wt% can achieve good performance while being more economical. Comparing Examples 5 and Examples 9 to 11, the water absorption rate of the recycled aggregate decreased with increasing soaking time in the field traction module. The water absorption rate gradually decreased. Compared with the blank control, the water absorption rate reduction rates of Examples 5, 9-11 were 69.46%, 54.82%, 63.75%, and 72.14%, respectively. The largest decrease occurred when the soaking time of the recycled aggregate was increased to 10 minutes, and then the decrease showed a downward trend. The crushing index and apparent density showed similar trends. However, considering the production process control and the strengthening effect, a soaking time of 10-15 minutes for the recycled aggregate has high production efficiency. Compared with Examples 5, 12, and 13, the water absorption rate of the recycled aggregate gradually decreased with the increase of voltage in the field traction module, but the change was not significant. Therefore, the voltage of the field traction module in this invention can be a normal voltage power supply. Considering all factors, 200-500V is preferable.

[0197] Comparing Examples 5 and Examples 14-17 of Group D, the water absorption rate of the recycled aggregate gradually decreased with the increase of magnesium oxide solution concentration in the alkali-rich module. Compared with the water absorption rate data of the blank control, the water absorption rate reduction rates of Examples 5 and Examples 14-17 were 69.46%, 48.04%, 55.54%, 65.36%, and 71.96%, respectively. The largest decrease was observed when the magnesium oxide solution concentration reached 20 wt%, followed by a decreasing trend. The crushing index and apparent density showed similar trends, indicating that a higher magnesium oxide solution concentration is better. Considering all factors, selecting 20-25 wt% achieves good performance while being more economical. Comparing Examples 5 and 18-20, as the soaking time of recycled aggregate in the alkali-rich module increased, the water absorption rate of the recycled aggregate gradually decreased. Compared with the water absorption rate data of the blank control, the water absorption rate reduction rates of Examples 5, 18-20 were 69.46%, 56.61%, 63.39%, and 70.54%, respectively. The increase was highest when the soaking time of the recycled aggregate increased to 10 minutes, and then the increase showed a decreasing trend. The crushing index and apparent density showed similar trends. Considering the production process control and the strengthening effect, a soaking time of 10-15 minutes for the recycled aggregate has high production efficiency.

[0198] Comparing Examples 5 and Examples 21-23 of Group E, the water absorption rate of the recycled aggregate gradually decreased with the increase of the concentration of the nano-silica solution in the accelerated reaction module. Compared with the water absorption rate data of the blank control, the water absorption rate reduction rates of Examples 5 and Examples 21-23 were 69.46%, 49.29%, 74.64%, and 77.68%, respectively. The reduction was highest when the concentration of the nano-silica solution increased to 2 wt%, and then the reduction showed a decreasing trend. The crushing index and apparent density showed similar trends. Therefore, the higher the concentration of the nano-silica solution, the better. However, considering cost factors and the selection of the nano-silica solution concentration range in the field traction module, a nano-silica solution concentration of 1-3 wt% is more economical in this module. Comparing Examples 5 and Examples 24-26, the water absorption rate of the recycled aggregate gradually decreased with the increase of the soaking time in the accelerated reaction module. Compared with the water absorption rate data of the blank control, the reduction rates of the recycled aggregate gradually decreased with the increase of the concentration of the nano-silica solution in the accelerated reaction module. The water absorption reduction rates of Examples 5 and 24-26 were 69.46%, 52.86%, 65.54%, and 73.04%, respectively. The reduction was highest when the soaking time of the recycled aggregate was increased to 10 minutes, and then the reduction showed a decreasing trend. The crushing index and apparent density showed similar trends. Considering the production process control and the strengthening effect, a soaking time of 10-15 minutes for the recycled aggregate has high production efficiency. Compared with Examples 5 and 27-29, the water absorption rate of the recycled aggregate gradually decreased with the increase of temperature in the accelerated reaction module. Compared with the water absorption rate data of the blank control, the water absorption reduction rates of Examples 5 and 27-29 were 69.46%, 57.5%, 67.32%, and 71.61%, respectively. The reduction reached its maximum when the temperature reached 50°C. Considering the production cost and various performance data, a soaking heating temperature of 50-90°C for the recycled aggregate is more economical and efficient.

[0199] Test Example 2

[0200] Modified recycled aggregate concrete prepared using the modified recycled aggregates prepared in Examples 3 and 30-32, respectively, was tested. The compressive strength and splitting tensile strength of the modified recycled aggregate concrete were tested using the test methods provided in the national standard GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The process parameter settings for preparing the modified recycled aggregates in Examples 3 and 30-32 are shown in Table 3, and the test results are shown in Table 4.

[0201] Table 4. Process parameter settings for Examples 3, 30-32

[0202]

[0203] Table 3. Performance test results of modified recycled aggregate concrete prepared in Examples 35-38

[0204] Compressive strength (MPa) Splitting strength (MPa) Example 33 74.6 3.24 Example 34 76.4 3.31 Example 35 77.9 3.38 Example 36 79.1 3.45

[0205] The test results above show that after modified recycled aggregates are treated with nano-silica atomization curing in the storage module, the compressive strength and splitting tensile strength of the recycled aggregate concrete prepared using them are improved to varying degrees. Furthermore, the data from Examples 34-36 show that the compressive strength and splitting tensile strength of the recycled aggregate concrete further increase with the increase of atomization curing time. This indicates that nano-silica atomization curing can provide significant positive effects on the later application of recycled aggregates. Nano-silica atomization curing can enhance the interfacial properties of modified recycled aggregates, and the concrete prepared after atomization curing has better performance parameters.

[0206] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing modified recycled aggregate, characterized in that, Includes the following steps: S1. After pre-soaking the recycled aggregate in water for 6-24 hours, air-dry it until it is surface dry, and then soak it in a nano-silica solution with a concentration of 0.5-7wt% for 8-20 minutes. During the soaking process, an electric field with a voltage of 150-550V is applied. There are two electric fields, and the directions of the two electric fields are perpendicular to each other, so as to accelerate the filling of the recycled aggregate with nano-silica. The nano-silica solution is prepared by mixing nano-silica powder with alkaline wastewater. The alkaline wastewater is the supernatant obtained by natural sedimentation of the wastewater generated during pre-soaking for 8-12 hours. S2. Remove the nano-silica solution and soak the recycled aggregate in a magnesium oxide solution with a concentration of 15%~30wt% for 8~20 minutes; S3. Remove magnesium oxide solution, immerse the recycled aggregate in a nano silica solution with a concentration of 0.5~5wt%, heat to 40~95℃ and soak for 8~20 minutes; S4. Use a 0.5~5wt% nano silica solution to perform atomization curing on the recycled aggregate. The atomization curing time is 2~10 days. The atomization curing is intermittent curing, with each curing time being 10~15 minutes and the curing interval being 6~10 hours.

2. A modified recycled aggregate, characterized in that, The modified recycled aggregate is prepared using the method for preparing the modified recycled aggregate according to claim 1.

3. A type of recycled aggregate concrete, characterized in that, The raw materials include the modified recycled aggregate as described in claim 2, cement, water, and sand.

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