Regeneration method of waste concrete and regenerated building material

Abstract

The invention relates to a regeneration method of waste concrete and a regenerated building material, and relates to the technical field of building materials.The regeneration method of the waste concrete comprises the following steps that the waste concrete is crushed and screened, and waste concrete particles are obtained; adding the waste concrete particles, a silane coupling agent and ionic liquid into a polyethylene glycol aqueous solution, and stirring and mixing to obtain a first mixture; and alternately and circularly treating the first mixture in an ultrasonic field and a pulsed electric field, and the like. Through an innovative waste concrete regeneration mode of combined treatment of physical modification and chemical modification, not only is the water absorption rate of the obtained recycled aggregate reduced, but also the activity of the obtained recycled aggregate is improved. The modified coconut shell powder and other components are subsequently matched for use, so that the compressive strength, cracking resistance and other comprehensive mechanical properties of the regenerated building material are remarkably improved, and the regenerated building material can meet the use requirements in low-temperature and other severe working environments.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a method for regenerating waste concrete and a regenerated building material. Background Art

[0002] The traditional way to deal with waste concrete is mainly landfilling. However, this method not only occupies a large amount of land resources, especially arable land, but also causes serious environmental pollution. Waste concrete contains recyclable components such as cement and sand and gravel. Direct landfilling is a huge waste of resources. Therefore, how to effectively treat and reuse waste concrete has become a hot topic of research.

[0003] Recycled Concrete (RAC), also known as Recycled Aggregate Concrete (RAC), is a recycled building material made by crushing, cleaning, grading, mixing with grading in a certain proportion, partially or completely replacing natural aggregates such as sand and gravel, and preparing with other additives. This not only solves the problem of waste concrete disposal, but also reduces the demand for natural resource mining and environmental pollution. However, since recycled aggregates made from waste concrete often have disadvantages such as high water absorption and low strength, the resulting recycled building materials have low strength and severe cracking, which cannot meet the use requirements in harsh operating environments such as low temperature. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for recycling waste concrete and recycled building materials.

[0005] In a first aspect, the present invention provides a method for regenerating waste concrete, the method comprising the following steps:

[0006] Crushing and screening the waste concrete to obtain waste concrete particles;

[0007] Adding the waste concrete particles, silane coupling agent and ionic liquid into the polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture;

[0008] The first mixture is subjected to alternating cycle treatment in an ultrasonic field and a pulse electric field, and then filtered, dried, ball-milled and sieved to obtain recycled aggregate.

[0009] Furthermore, the weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:(3-7):(10-20).

[0010] Furthermore, the particle size of the waste concrete particles is ≤40 mm; the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane; and the ionic liquid is a pyridine-type ionic liquid containing a linear alkyl group with 7 to 10 carbon atoms.

[0011] Furthermore, the pyridine-type ionic liquid containing a linear alkyl group with a carbon number of 7 to 10 includes N-heptyl-3-methylpyridine bromide, N-octyl-3-methylpyridine bromide and N-octyl-4-methylpyridine bromide.

[0012] Furthermore, in terms of weight percentage, the polyethylene glycol concentration in the polyethylene glycol aqueous solution is 15-35%, and the polyethylene glycol includes at least one of PEG500 and PEG1000; the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:(0.5-2).

[0013] Furthermore, the first mixture is subjected to alternating cycle treatment in an ultrasonic field and a pulse electric field, and then filtered, dried, ball-milled and screened to obtain the recycled aggregate, which comprises the following process:

[0014] The first mixed material is placed in an ultrasonic field with an ultrasonic power of 200-350W and an ultrasonic frequency of 30-50kHz for ultrasonic treatment for 1-5 minutes, and then the peak current density is 0.3-2A / cm 2 and a pulse electric field with a pulse frequency of 1-5 Hz for 0.5-2 minutes, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 3-5 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 10-20 seconds, to obtain a second mixed material;

[0015] The second mixture is filtered, dried, ball-milled and sieved to obtain recycled aggregate.

[0016] Furthermore, the particle size of the recycled aggregate is 5 to 20 mm.

[0017] In a second aspect, the present invention provides a recycled building material, which comprises the following components in parts by weight:

[0018] 150-220 parts of cement, 350-450 parts of sand, 1550-1650 parts of recycled aggregate, 25-35 parts of modified coconut shell powder and 200-300 parts of water;

[0019] The recycled aggregate is obtained by the method for recycling waste concrete as described in any one of the first aspects;

[0020] The modified coconut shell powder is obtained by placing the coconut shell powder soaked in alkali solution in a magnetic field sintering furnace for heat treatment.

[0021] Furthermore, the preparation method of the modified coconut shell powder comprises the following process:

[0022] The coconut shell powder with a particle size of 200-300 meshes is placed in an ammonia solution with a mass fraction of 60-70% and soaked overnight at room temperature, and then filtered and dried to obtain coconut shell powder soaked in alkali solution;

[0023] The coconut shell powder soaked in alkali solution is placed in a magnetic field sintering furnace, the flux coil current is set to 6-10A, the temperature is raised from room temperature to 600-750°C at a speed of 10-15°C / min and heat-treated for 1-2 hours, and the modified coconut shell powder is obtained by cooling with the furnace.

[0024] Furthermore, the recycled building material comprises the following components in parts by weight:

[0025] 200 parts of cement, 390 parts of sand, 1600 parts of recycled aggregate, 30 parts of modified coconut shell powder and 260 parts of water.

[0026] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0027] The embodiments of the present invention provide a method for recycling waste concrete and recycled building materials. The present invention uses an innovative method for recycling waste concrete by combining physical modification and chemical modification, which not only reduces the water absorption rate of the recycled aggregate, but also improves the activity of the recycled aggregate. It is subsequently applied to recycled building materials and used in combination with modified coconut shell powder and other components to significantly improve the comprehensive mechanical properties of the recycled building materials, such as compressive strength and crack resistance, so that the recycled building materials can adapt to the use requirements in harsh working environments such as low temperature. Specifically:

[0028] 1. Chemical modification stage: By introducing an appropriate amount of silane coupling agent and a pyridine-type ionic liquid containing a linear alkyl carbon number of 7 to 10, chemical bonds and strong electrostatic adsorption are formed with components such as silicates on the surface of waste concrete particles, which not only improves its surface properties, but also enhances the interfacial bonding between recycled aggregates and cement-based materials.

[0029] 2. Physical modification stage: Ultrasonic waves produce strong cavitation effect and micro-jet effect in the liquid, which can destroy the microstructure of the surface of waste concrete particles and increase their specific surface area and porosity. This is not only conducive to the deeper penetration of silane coupling agents and ionic liquids into the interior of waste concrete particles, but also further physically activates the waste concrete particles, providing more reaction sites for pulsed electric field treatment; the pulsed electric field accelerates the distribution and reaction of ionic liquids in the system through the action of electric field force; during the alternating cycle treatment of ultrasonic field and pulsed electric field, the two physical fields produce a synergistic effect and act together on the first mixture system, so that the comprehensive properties of recycled aggregates such as water absorption and activity are significantly improved.

[0030] In summary, the present invention provides a method for regenerating waste concrete. Through the interaction of introducing silane coupling agent and pyridine-type ionic liquid containing linear alkyl carbon number of 7 to 10, ultrasonic field and pulse electric field alternating cycle treatment and other steps, the water absorption rate of recycled aggregate is successfully reduced and its activity is significantly improved. This method provides an effective way for the recycling of waste concrete. At the same time, it is subsequently applied to recycled building materials and used in combination with modified coconut shell powder and other components to significantly improve the comprehensive mechanical properties of recycled building materials such as compressive strength and crack resistance, so that the recycled building materials can adapt to the use requirements in harsh working environments such as low temperature. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0033] In a first aspect, the present invention provides a method for regenerating waste concrete, the method comprising the following steps:

[0034] Crushing and screening the waste concrete to obtain waste concrete particles;

[0035] Adding the waste concrete particles, silane coupling agent and ionic liquid into the polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture;

[0036] The first mixture is subjected to alternating cycle treatment in an ultrasonic field and a pulse electric field, and then filtered, dried, ball-milled and sieved to obtain recycled aggregate.

[0037] The embodiment of the present invention provides a method for regenerating waste concrete. The present invention uses an innovative method for regenerating waste concrete by combining physical modification and chemical modification, which not only reduces the water absorption rate of the obtained recycled aggregate, but also improves the activity of the obtained recycled aggregate. Specifically:

[0038] 1. Chemical modification stage: By introducing an appropriate amount of silane coupling agent and a pyridine-type ionic liquid containing a linear alkyl carbon number of 7 to 10, chemical bonds and strong electrostatic adsorption are formed with components such as silicates on the surface of waste concrete particles, which not only improves its surface properties, but also enhances the interfacial bonding between recycled aggregates and cement-based materials.

[0039] 2. Physical modification stage: Ultrasonic waves produce strong cavitation effect and micro-jet effect in the liquid, which can destroy the microstructure of the surface of waste concrete particles and increase their specific surface area and porosity. This is not only conducive to the deeper penetration of silane coupling agents and ionic liquids into the interior of waste concrete particles, but also further physically activates the waste concrete particles, providing more reaction sites for pulsed electric field treatment; the pulsed electric field accelerates the distribution and reaction of ionic liquids in the system through the action of electric field force; during the alternating cycle treatment of ultrasonic field and pulsed electric field, the two physical fields produce a synergistic effect and act together on the first mixture system, so that the comprehensive properties of recycled aggregates such as water absorption and activity are significantly improved.

[0040] In some specific embodiments, the waste concrete comes from waste concrete beams, waste concrete columns, waste concrete slabs, etc., from which other materials such as steel bars, wood chips, and plastics are removed.

[0041] In some specific embodiments, the weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:(3-7):(10-20), preferably 1000:5:17.

[0042] In some specific embodiments, the particle size of the waste concrete particles is ≤40 mm; the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane, preferably γ-glycidyloxypropyltrimethoxysilane; and the ionic liquid is a pyridine-type ionic liquid containing a linear alkyl group with a carbon number of 7 to 10.

[0043] In some specific embodiments, the pyridine-type ionic liquid containing a linear alkyl group with a carbon number of 7 to 10 includes N-heptyl-3-methylpyridine bromide, N-octyl-3-methylpyridine bromide and N-octyl-4-methylpyridine bromide, preferably N-octyl-4-methylpyridine bromide.

[0044] In some specific embodiments, the polyethylene glycol concentration in the polyethylene glycol aqueous solution is 15-35%, preferably 30%, by weight percentage; the polyethylene glycol includes at least one of PEG500 and PEG1000, preferably PEG500; the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:(0.5-2), preferably 1:1.

[0045] In some specific embodiments, the first mixture is subjected to alternating cycles of ultrasonic field and pulse electric field, and then filtered, dried, ball-milled and screened to obtain the recycled aggregate, which comprises the following process:

[0046] The first mixed material is placed in an ultrasonic field with an ultrasonic power of 200-350W and an ultrasonic frequency of 30-50kHz for ultrasonic treatment for 1-5 minutes, and then the peak current density is 0.3-2A / cm 2 and a pulse electric field with a pulse frequency of 1-5 Hz for 0.5-2 minutes, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 3-5 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 10-20 seconds, to obtain a second mixed material;

[0047] The second mixture is filtered, dried, ball-milled and sieved to obtain recycled aggregate.

[0048] In some specific embodiments, the ultrasonic power of the ultrasonic treatment is preferably 300 W and the ultrasonic frequency is 40 kHz.

[0049] In some specific embodiments, the peak current density of the pulsed electric field treatment is preferably 1.5 A / cm 2 And the pulse frequency is preferably 3 Hz.

[0050] In some specific embodiments, the working condition parameters of the ball mill include: a ball-to-material ratio of (10-15):1.

[0051] In some specific embodiments, the particle size of the recycled aggregate is 5 to 20 mm.

[0052] In the second aspect, based on the same inventive concept, the present invention provides a recycled building material, which comprises the following components in parts by weight:

[0053] 150-220 parts of cement, 350-450 parts of sand, 1550-1650 parts of recycled aggregate, 25-35 parts of modified coconut shell powder and 200-300 parts of water;

[0054] The recycled aggregate is obtained by the method for recycling waste concrete as described in any one of the first aspects;

[0055] The modified coconut shell powder is obtained by placing the coconut shell powder soaked in alkali solution in a magnetic field sintering furnace for heat treatment.

[0056] Based on the method for recycling waste concrete provided in the first aspect above, the present invention further applies the obtained recycled aggregate to recycled building materials, and uses it in combination with components such as modified coconut shell powder, which significantly improves the comprehensive mechanical properties of the recycled building materials such as compressive strength and crack resistance, thereby enabling the recycled building materials to adapt to the use requirements in harsh working environments such as low temperature.

[0057] In some specific embodiments, the method for preparing the modified coconut shell powder comprises the following process:

[0058] The coconut shell powder with a particle size of 200-300 meshes is placed in an ammonia solution with a mass fraction of 60-70% and soaked overnight at room temperature, and then filtered and dried to obtain coconut shell powder soaked in alkali solution;

[0059] The coconut shell powder soaked in alkali solution is placed in a magnetic field sintering furnace, the flux coil current is set to 6-10A, the temperature is raised from room temperature to 600-750°C at a speed of 10-15°C / min and heat-treated for 1-2 hours, and the modified coconut shell powder is obtained by cooling with the furnace.

[0060] In some specific embodiments, when the coconut shell powder is immersed in an ammonia solution having a mass fraction of 60-70% at room temperature overnight, the amount of the ammonia solution used can ensure that the coconut shell powder can be immersed in the ammonia solution.

[0061] In some specific embodiments, the recycled building material includes the following components by weight:

[0062] 200 parts of cement, 390 parts of sand, 1600 parts of recycled aggregate, 30 parts of modified coconut shell powder and 260 parts of water.

[0063] In some specific embodiments, the cement is P·O42.5 ordinary Portland cement, and the sand is river sand with a fineness modulus of 2.8.

[0064] It should be noted that, for the method for recycling waste concrete and the component raw materials involved in the recycled building materials provided in the embodiments of the present invention, unless otherwise specified or explained, each component can be directly commercially available or homemade according to existing public processes; the operating steps involved, unless otherwise specified or explained, can be carried out in accordance with the operating methods disclosed in the prior art or using existing equipment according to its usage methods.

[0065] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0066] Example 1

[0067] This example provides a method for recycling waste concrete, which comprises the following steps:

[0068] Step (1): crushing and screening the waste concrete to obtain waste concrete particles with a particle size of ≤40 mm;

[0069] Step (2): adding the waste concrete particles, silane coupling agent and ionic liquid obtained in step (1) into a polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture;

[0070] The weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:5:17, the silane coupling agent is γ-glycidyloxypropyltrimethoxysilane, the ionic liquid is N-octyl-4-methylpyridinium bromide, the weight percentage concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 30%, the polyethylene glycol is PEG500, and the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:1;

[0071] Step (3): The first mixed material obtained in step (2) is placed in an ultrasonic field with an ultrasonic power of 300 W and an ultrasonic frequency of 40 kHz for 3 minutes, and then the peak current density is 1.5 A / cm 2 and a pulse electric field with a pulse frequency of 3 Hz for 1 minute, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 4 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 15 seconds, to obtain a second mixed material;

[0072] Step (4): The second mixed material obtained in step (3) is filtered, vacuum dried, ball-milled and sieved, with a ball-to-material ratio of 12:1, to obtain recycled aggregate with a particle size of 5 to 20 mm.

[0073] Example 2

[0074] This example provides a method for recycling waste concrete, which comprises the following steps:

[0075] Step (1): crushing and screening the waste concrete to obtain waste concrete particles with a particle size of ≤40 mm;

[0076] Step (2): adding the waste concrete particles, silane coupling agent and ionic liquid obtained in step (1) into a polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture;

[0077] Wherein, the weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:3:10, the silane coupling agent is γ-aminopropyltriethoxysilane, the ionic liquid is N-octyl-4-methylpyridinium bromide, the weight percentage concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 30%, the polyethylene glycol is PEG500, and the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:1;

[0078] Step (3): The first mixed material obtained in step (2) is placed in an ultrasonic field with an ultrasonic power of 200 W and an ultrasonic frequency of 50 kHz for 5 minutes, and then the peak current density is 0.3 A / cm 2 and a pulse electric field with a pulse frequency of 5 Hz for 2 minutes, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 4 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 15 seconds, to obtain a second mixed material;

[0079] Step (4): The second mixed material obtained in step (3) is filtered, vacuum dried, ball-milled and sieved, with a ball-to-material ratio of 12:1, to obtain recycled aggregate with a particle size of 5 to 20 mm.

[0080] Example 3

[0081] This example provides a method for recycling waste concrete, which comprises the following steps:

[0082] Step (1): crushing and screening the waste concrete to obtain waste concrete particles with a particle size of ≤40 mm;

[0083] Step (2): adding the waste concrete particles, silane coupling agent and ionic liquid obtained in step (1) into a polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture;

[0084] The weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:7:20, the silane coupling agent is γ-aminopropyltriethoxysilane, the ionic liquid is N-octyl-4-methylpyridinium bromide, the weight percentage concentration of polyethylene glycol in the polyethylene glycol aqueous solution is 30%, the polyethylene glycol is PEG500, and the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:1;

[0085] Step (3): The first mixed material obtained in step (2) is placed in an ultrasonic field with an ultrasonic power of 350 W and an ultrasonic frequency of 30 kHz for 1 minute, and then the mixture is treated with a current peak density of 2 A / cm 2 and a pulse electric field with a pulse frequency of 1 Hz for 0.5 minutes, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 4 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 15 seconds, to obtain a second mixed material;

[0086] Step (4): The second mixed material obtained in step (3) is filtered, vacuum dried, ball-milled and sieved, with a ball-to-material ratio of 12:1, to obtain recycled aggregate with a particle size of 5 to 20 mm.

[0087] Example 4

[0088] This example provides a recycled building material, which includes the following components by weight:

[0089] 200 parts of cement, 390 parts of sand, 1600 parts of recycled aggregate, 30 parts of modified coconut shell powder and 260 parts of water;

[0090] The cement is P·O42.5 ordinary Portland cement;

[0091] The sand is river sand with a fineness modulus of 2.8;

[0092] The recycled aggregate is obtained by the method for recycling waste concrete described in Example 1;

[0093] The preparation method of the modified coconut shell powder comprises the following process:

[0094] Step (1): immersing coconut shell powder with a particle size of 200 to 300 meshes in a 65% ammonia solution at room temperature for 24 hours, filtering and drying to obtain coconut shell powder treated with alkali solution;

[0095] Step (2): placing the coconut shell powder soaked in alkali solution obtained in step (1) in a magnetic field sintering furnace, setting the flux coil current to 8A, heating from room temperature to 700°C at a rate of 10°C / min and heat-treating for 1.5 hours, cooling with the furnace, and obtaining the modified coconut shell powder.

[0096] Example 5

[0097] This example provides a recycled building material, which includes the following components by weight:

[0098] 150 parts of cement, 350 parts of sand, 1550 parts of recycled aggregate, 25 parts of modified coconut shell powder and 200 parts of water;

[0099] The cement is P·O42.5 ordinary Portland cement;

[0100] The sand is river sand with a fineness modulus of 2.8;

[0101] The recycled aggregate is obtained by the method for recycling waste concrete described in Example 2;

[0102] The preparation method of the modified coconut shell powder comprises the following process:

[0103] Step (1): immersing coconut shell powder with a particle size of 200 to 300 meshes in a 60% ammonia solution at room temperature for 24 hours, filtering and drying to obtain coconut shell powder treated with alkali solution;

[0104] Step (2): placing the coconut shell powder soaked in alkali solution obtained in step (1) in a magnetic field sintering furnace, setting the flux coil current to 6A, heating from room temperature to 600°C at a rate of 10°C / min and heat-treating for 2 hours, cooling with the furnace, and obtaining the modified coconut shell powder.

[0105] Example 6

[0106] This example provides a recycled building material, which includes the following components by weight:

[0107] 220 parts of cement, 450 parts of sand, 1650 parts of recycled aggregate, 35 parts of modified coconut shell powder and 300 parts of water;

[0108] The cement is P·O42.5 ordinary Portland cement;

[0109] The sand is river sand with a fineness modulus of 2.8;

[0110] The recycled aggregate is obtained by the method for recycling waste concrete described in Example 3;

[0111] The preparation method of the modified coconut shell powder comprises the following process:

[0112] Step (1): immersing coconut shell powder with a particle size of 200 to 300 meshes in a 60% ammonia solution at room temperature for 24 hours, filtering and drying to obtain coconut shell powder treated with alkali solution;

[0113] Step (2): placing the coconut shell powder soaked in alkali solution obtained in step (1) in a magnetic field sintering furnace, setting the flux coil current to 6A, heating from room temperature to 750°C at a rate of 10°C / min and heat-treating for 1 hour, cooling with the furnace, and obtaining the modified coconut shell powder.

[0114] Comparative Example 1

[0115] This example provides a method for recycling waste concrete, which comprises the following steps:

[0116] Step (1): crushing and screening the waste concrete to obtain waste concrete particles with a particle size of ≤40 mm;

[0117] Step (2): The waste concrete particles obtained in step (1) are ball-milled and screened, with a ball-to-material ratio of 12:1, to obtain recycled aggregate with a particle size of 5 to 20 mm.

[0118] Comparative Example 2

[0119] This example provides a method for regenerating waste concrete, which is different from Example 1 only in that N-octyl-4-methylpyridine bromide is adjusted to N-ethyl-4-methylpyridine bromide.

[0120] Comparative Example 3

[0121] This example provides a recycled building material, which includes the following components by weight:

[0122] 230 parts of cement, 390 parts of sand, 1600 parts of recycled aggregate and 260 parts of water;

[0123] The cement is P·O42.5 ordinary Portland cement;

[0124] The sand is river sand with a fineness modulus of 2.8;

[0125] The recycled aggregate is obtained by the method for recycling waste concrete described in Example 1.

[0126] Comparative Example 4

[0127] This example provides a recycled building material, which is different from Example 4 only in that the weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid in the recycled aggregate preparation process is adjusted to 1000:5:97; the remaining steps and parameters are the same.

[0128] Test Example 1

[0129] In this example, the water absorption rate of the recycled aggregates obtained in Examples 1 to 3 and Comparative Examples 1 to 2 was measured according to GB / T 14685 "Pebble and Crushed Stone for Construction", and a mixture of crushed stone and natural sand with a particle size of 5 to 20 mm was used as a basic control. The measurement results are shown in Table 1.

[0130] Table 1

[0131]

[0132] It can be seen from Table 1 that compared with the recycled aggregate obtained without physical modification-chemical modification combined treatment (i.e., Comparative Example 1) and Comparative Example 2, the recycled aggregate provided by the embodiment of the present invention has a lower water absorption rate, and has no significant difference from the mixture of crushed stone and natural sand.

[0133] Test Example 2

[0134] In this example, the performance of the recycled building materials provided by Examples 4 to 6 and Comparative Examples 3 to 4 was tested.

[0135] Test method: Mix and stir the components according to the proportion, and then cure under the same conditions to obtain a cubic test block with a side length of 150 mm for 28-day compressive strength test (refer to GB / T 50081 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete"). The test results are shown in Table 2.

[0136] Table 2

[0137]

[0138] In addition, this example refers to GB / T50085-2009 "Test method for long-term performance and durability of ordinary concrete" to conduct freeze-thaw cycle anti-cracking tests on the recycled building materials provided by Examples 4 to 6 and Comparative Examples 3 to 4, and records the number of freeze-thaw cycles corresponding to the appearance of visible cracks on the surface of the test block. The test results are shown in Table 3.

[0139] Table 3

[0140]

[0141] As can be seen from Table 2 and Table 3, the embodiments of the present invention provide a method for regenerating waste concrete and a recycled building material. The waste concrete regeneration method provided by the present invention successfully reduces the water absorption rate of the recycled aggregate and significantly improves its activity through the interaction of the steps of introducing a silane coupling agent and a pyridine-type ionic liquid containing a straight-chain alkyl carbon number of 7 to 10, and alternating cyclic treatment of an ultrasonic field and a pulsed electric field. This method provides an effective way for the recycling of waste concrete. At the same time, it is subsequently applied to recycled building materials and used in combination with components such as modified coconut shell powder to significantly improve the comprehensive mechanical properties of the recycled building materials such as compressive strength and crack resistance, so that the recycled building materials can adapt to the use requirements in harsh working environments such as low temperature.

[0142] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0143] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for recycling waste concrete, characterized in that: The method for regenerating waste concrete comprises the following steps: Crushing and screening the waste concrete to obtain waste concrete particles; Adding the waste concrete particles, silane coupling agent and ionic liquid into the polyethylene glycol aqueous solution and stirring and mixing to obtain a first mixture; The first mixture is subjected to alternating cycle treatment in an ultrasonic field and a pulse electric field, and then filtered, dried, ball-milled and sieved to obtain recycled aggregate.

2. The method for recycling waste concrete according to claim 1, characterized in that: The weight ratio of the waste concrete particles, the silane coupling agent and the ionic liquid is 1000:(3-7):(10-20).

3. The method for recycling waste concrete according to claim 1, characterized in that: The particle size of the waste concrete particles is ≤40 mm; the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane; and the ionic liquid is a pyridine-type ionic liquid containing a linear alkyl group with 7 to 10 carbon atoms.

4. The method for recycling waste concrete according to claim 4, characterized in that: The pyridine-type ionic liquid containing a linear alkyl group with carbon number of 7 to 10 includes N-heptyl-3-methylpyridine bromide, N-octyl-3-methylpyridine bromide and N-octyl-4-methylpyridine bromide.

5. The method for recycling waste concrete according to claim 1, characterized in that: In terms of weight percentage, the polyethylene glycol concentration in the polyethylene glycol aqueous solution is 15-35%, and the polyethylene glycol includes at least one of PEG500 and PEG1000; the weight ratio of the waste concrete particles to the polyethylene glycol aqueous solution is 1:(0.5-2).

6. The method for recycling waste concrete according to claim 1, characterized in that: The first mixture is subjected to alternating cycle treatment in an ultrasonic field and a pulse electric field, and then filtered, dried, ball-milled and screened to obtain the recycled aggregate, which comprises the following process: The first mixture is placed in an ultrasonic field with an ultrasonic power of 200-350W and an ultrasonic frequency of 30-50kHz for ultrasonic treatment for 1-5 minutes, and then subjected to a pulse electric field treatment for 0.5-2 minutes in a pulse electric field with a current peak density of 0.3-2A / cm2 and a pulse frequency of 1-5Hz, the ultrasonic field and the pulse electric field are subjected to alternating cycle treatment for 3-5 times, and the interval between each ultrasonic treatment and each pulse electric field treatment is 10-20 seconds, to obtain a second mixture; The second mixture is filtered, dried, ball-milled and sieved to obtain recycled aggregate.

7. The method for recycling waste concrete according to claim 6, characterized in that: The particle size of the recycled aggregate is 5 to 20 mm.

8. A recycled building material, characterized in that: The recycled building material comprises the following components in parts by weight: 150-220 parts of cement, 350-450 parts of sand, 1550-1650 parts of recycled aggregate, 25-35 parts of modified coconut shell powder and 200-300 parts of water; The recycled aggregate is obtained by the method for recycling waste concrete as claimed in any one of claims 1 to 7; The modified coconut shell powder is obtained by placing the coconut shell powder soaked in alkali solution in a magnetic field sintering furnace for heat treatment.

9. The recycled building material according to claim 8, characterized in that: The preparation method of the modified coconut shell powder comprises the following process: The coconut shell powder with a particle size of 200-300 meshes is placed in an ammonia solution with a mass fraction of 60-70% and soaked overnight at room temperature, and then filtered and dried to obtain coconut shell powder soaked in alkali solution; The coconut shell powder soaked in alkali solution is placed in a magnetic field sintering furnace, the flux coil current is set to 6-10A, the temperature is raised from room temperature to 600-750°C at a speed of 10-15°C / min and heat-treated for 1-2 hours, and the modified coconut shell powder is obtained by cooling with the furnace.

10. The recycled building material according to claim 8, characterized in that: The recycled building material comprises the following components in parts by weight: 200 parts of cement, 390 parts of sand, 1600 parts of recycled aggregate, 30 parts of modified coconut shell powder and 260 parts of water.

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