High-strength recycled concrete and preparation method thereof

Abstract

The present application discloses a high-strength recycled concrete and a preparation method thereof, which relates to the field of concrete. The high-strength recycled concrete comprises raw materials, by weight, including 120-200 parts of cement, 850-1000 parts of hydrophobically modified recycled coarse aggregate, 180-280 parts of recycled fine aggregate, 220-360 parts of sand, 400-650 parts of fly ash, 60-120 parts of silica fume, 20-35 parts of water reducer, 22-35 parts of modified waste rubber powder, and 80-120 parts of water; the hydrophobically modified recycled coarse aggregate comprises The recycled concrete prepared by the method comprises the following components: 10-16 parts recycled coarse aggregate, 15-27 parts hydrophobic desulfurized gypsum powder, 3-5 parts polyethylene glycol, 24-36 parts acrylic resin, and 30-40 parts water; the hydrophobic desulfurized gypsum powder raw material comprises the following components: 15-21 parts desulfurized gypsum, 10-15 parts sodium hydroxide, 5-7 parts sodium sulfate, 18-24 parts silane coupling agent, 2-5 parts anionic surfactant, and 45-65 parts solvent. The recycled concrete produced by the method exhibits high compressive strength, splitting tensile strength, and strong crack resistance.

Description

Technical Field

[0001] The present application relates to the field of concrete, and in particular to a high-strength recycled concrete and a preparation method thereof. Background Art

[0002] Recycled aggregate concrete, or simply recycled concrete, refers to new concrete made by partially or completely replacing natural aggregate with crushed, cleaned, and graded waste concrete. Concrete production consumes significant amounts of natural resources, such as sand and stone. As concrete consumption continues to increase, these natural aggregates are becoming increasingly depleted. Therefore, recycling waste concrete can help offset this resource shortfall.

[0003] For related technology, reference may be made to the Chinese invention patent application with publication number CN113024165A, which discloses a recycled concrete mainly comprising the following raw materials: 450 parts of cement, 200 parts of water, 710 parts of recycled aggregate, 5 parts of water reducer, 500 parts of sand, 25 parts of fly ash, and 210 parts of crushed stone.

[0004] However, since the surface of recycled aggregate contains a large amount of old mortar and pores, the water absorption rate of recycled coarse aggregate increases, the density decreases, and the wear resistance deteriorates. Therefore, when used in concrete production, the durability and mechanical properties of the concrete produced are significantly different from those of ordinary concrete, which limits the development of recycled concrete. Summary of the Invention

[0005] In order to improve the durability and mechanical properties of recycled concrete, the present application provides a high-strength recycled concrete and a preparation method thereof.

[0006] This application provides a high-strength recycled concrete, which adopts the following technical solution:

[0007] A high-strength recycled concrete, the raw materials of which include, by weight: 120-200 parts of cement, 850-1000 parts of hydrophobically modified recycled coarse aggregate, 180-280 parts of recycled fine aggregate, 220-360 parts of sand, 400-650 parts of fly ash, 60-120 parts of silica fume, 20-35 parts of

[0008] Water reducing agent, 22-35 parts of modified waste rubber powder, 80-120 parts of water.

[0009] By adopting the above technical solution, the recycled coarse aggregate is modified so that the gaps in the recycled coarse aggregate are filled, the wear resistance is enhanced, and the water absorption rate is reduced. When used in recycled concrete, the mechanical properties of the recycled concrete can be effectively improved; at the same time, by adding waste rubber powder, the anti-seepage ability of the recycled concrete can be effectively enhanced.

[0010] Preferably, the hydrophobically modified recycled coarse aggregate raw material comprises the following components: 10-16 parts of recycled coarse aggregate, 15-27 parts of hydrophobic desulfurized gypsum powder, 3-5 parts of polyethylene glycol, 24-36 parts of acrylic resin, and 30-40 parts of water.

[0011] By adopting the above technical solution, the hydrophobic desulfurized gypsum powder can be used to expand and fill the recycled coarse aggregate. The hydrophobic desulfurized gypsum powder is mixed with water to form a plastic slurry, which becomes a hard solid after drying. It has the function of filling and cutting the capillary pores of the recycled coarse aggregate, and can reduce the porosity of the recycled coarse aggregate. Since gypsum has strong hygroscopicity, the absorbed water will weaken the bonding force between the gypsum grains, significantly reducing the strength. By hydrophobic modification of the desulfurized gypsum, the water absorption of the desulfurized gypsum can be reduced. At the same time, acrylic resin has excellent adhesion and can bond the fine cracks of the recycled coarse aggregate itself. Polyethylene glycol has excellent adhesion and dispersibility. While further bonding the fine cracks of the recycled coarse aggregate, it can make the desulfurized gypsum powder evenly dispersed, thereby improving the defects of the recycled coarse aggregate such as high water absorption, low density and poor wear resistance. When used in concrete production, it can improve the durability and mechanical properties of the recycled concrete.

[0012] Preferably, the hydrophobic desulfurized gypsum powder raw material comprises the following components: 15-21 parts desulfurized gypsum, 10-15 parts

[0013] Sodium hydroxide, 5-7 parts of sodium sulfate, 18-24 parts of silane coupling agent, 2-5 parts of anionic surfactant, 45-65 parts of solvent.

[0014] By adopting the above technical solution, the desulfurized gypsum is hydroxylated with sodium hydroxide and sodium sulfate to increase the amount of hydroxyl groups on the surface of the desulfurized gypsum. Then, a silane coupling agent and an anionic surfactant react with the hydroxyl groups on the surface to graft hydrophobic groups onto the surface of the desulfurized gypsum, thereby reducing the water absorption of the desulfurized gypsum powder and improving the problem of high water absorption of recycled coarse aggregate.

[0015] Preferably, the modified waste rubber powder raw material comprises the following components: 10-15 parts of waste rubber, 20-32 parts of silane coupling agent, and 1-2 parts of calcium carbonate.

[0016] By adopting the above technical solution and using waste rubber, the crack resistance of recycled concrete can be effectively improved, the crack expansion rate and the length and width of the crack mouth can be delayed, thereby effectively alleviating the phenomenon of stress concentration inside the recycled concrete and reducing the probability of cracking caused by stress in the recycled concrete; modification by silane coupling agent can increase the adhesion of rubber in cement, thereby enhancing the toughness and strength of concrete; at the same time, silane coupling agent can improve the dispersibility of the waste rubber surface, and can improve the problem that the waste rubber powder is prone to agglomeration due to its small particle size, thereby further enhancing the crack resistance.

[0017] Preferably, the water reducer includes polycarboxylic acid high-efficiency water reducer, naphthalene-based high-efficiency water reducer, and sodium sulfate, with a weight ratio of 1: (0.3-0.8): (0.08-0.16).

[0018] By adopting the above technical solution, using a combination of a polycarboxylate superplasticizer, a naphthalene-based superplasticizer, and sodium sulfate as a water reducer, cement usage can be reduced while maintaining concrete strength. The superplasticizer molecules can be directed to adsorb onto the surface of cement particles, imparting a uniform charge to the surfaces. This creates an electrostatic repulsion, promoting the mutual dispersion of cement particles and disrupting the flocculation structure, releasing trapped water and allowing it to flow, thereby effectively increasing the fluidity of the concrete mixture. The polycarboxylate superplasticizer and naphthalene-based superplasticizer have a strong dispersing effect on cement, resulting in a high water reduction rate and maintaining excellent mechanical properties of the concrete.

[0019] This application also provides a method for preparing high-strength recycled concrete, which adopts the following technical solution:

[0020] A method for preparing high-strength recycled concrete comprises the following steps:

[0021] Mix 120-200 parts of cement, 850-1000 parts of hydrophobically modified recycled coarse aggregate, 180-280 parts of recycled fine aggregate, 220-360 parts of sand, 400-650 parts of fly ash, 60-120 parts of silica fume, 20-35 parts of water reducer, 22-35 parts of modified waste rubber powder, and 80-120 parts of water, stir well, and obtain recycled concrete.

[0022] By adopting the above technical solution, the use of silica fume and fly ash can improve the durability and mechanical properties of recycled concrete. Silica fume can significantly improve the compression, flexural, impermeability, corrosion resistance, impact resistance and wear resistance of recycled concrete, and has the functions of retaining water, preventing segregation and bleeding, and greatly reducing the resistance of concrete pumping; fly ash can play an active role in concrete, which can make the gap between cement and fly ash smaller. At the same time, fly ash plays a filling role, which can increase the structural density. By adding silica fume and fly ash, not only can the durability and mechanical properties of the recycled concrete be improved, but also the amount of cement can be reduced.

[0023] Preferably, the method for preparing the hydrophobically modified recycled coarse aggregate comprises the following steps:

[0024] S1. Take waste concrete, crush it, wash it, dry it, and screen it to obtain recycled coarse aggregate and recycled fine aggregate after crushing;

[0025] S2. The obtained recycled coarse aggregate is immersed in a modifier for modification. After the modification is completed, the hydrophobically modified recycled coarse aggregate is obtained by filtering and drying.

[0026] By adopting the above technical solution and modifying the recycled coarse aggregate physically and chemically, the surface roughness, porosity and water absorption of the recycled coarse aggregate can be reduced, and the crushing index can be improved, so that the concrete produced can have high strength, strong durability and stable quality.

[0027] Preferably, the preparation method of the modifier comprises the following steps:

[0028] Add 15-27 parts of hydrophobic desulfurized gypsum powder to 30-40 parts of water and stir until completely dissolved. Then add 3-5 parts of polyethylene glycol and 24-36 parts of acrylic resin and stir evenly to obtain a modifier.

[0029] By adopting the above technical solution and using hydrophobic desulfurized gypsum powder, polyethylene glycol and acrylic resin to prepare the modifier, the porosity and water absorption of the recycled coarse aggregate can be reduced.

[0030] Preferably, the method for preparing the hydrophobic desulfurized gypsum powder comprises the following steps:

[0031] S1. The desulfurized gypsum was ground and sieved to obtain desulfurized gypsum powder; the desulfurized gypsum powder was calcined to obtain anhydrous desulfurized gypsum powder;

[0032] S2. 15-21 parts of anhydrous desulfurized gypsum powder are added to a mixture of 10-15 parts of sodium hydroxide and 5-7 parts of sodium sulfate, heated and mixed to obtain pretreated desulfurized gypsum powder;

[0033] S3. The pretreated desulfurized gypsum powder is added to a mixture of 18-24 parts of a silane coupling agent, 2-5 parts of an anionic surfactant, and 45-65 parts of a solvent, and heated and mixed to obtain a hydrophobic desulfurized gypsum powder.

[0034] By adopting the above technical solution, the desulfurized gypsum is hydroxylated with sodium hydroxide and sodium sulfate to increase the amount of hydroxyl groups on the surface of the desulfurized gypsum. Then, a silane coupling agent and an anionic surfactant react with the hydroxyl groups on the surface to graft hydrophobic groups onto the surface of the desulfurized gypsum, thereby reducing the water absorption of the desulfurized gypsum powder and improving the problem of high water absorption of recycled coarse aggregate.

[0035] Preferably, the method for processing waste rubber comprises the following steps:

[0036] S1. The waste rubber is washed, dried, crushed, and sieved to obtain waste rubber powder;

[0037] S2. Add 20-32 parts of silane coupling agent and 1-2 parts of calcium carbonate to 10-15 parts of waste rubber powder, stir and disperse, and then dry to obtain modified waste rubber powder.

[0038] By adopting the above technical solution and using waste rubber, the crack resistance of recycled concrete can be effectively improved, the crack expansion rate and the length and width of the crack mouth can be delayed, thereby effectively alleviating the phenomenon of stress concentration inside the recycled concrete and reducing the probability of recycled concrete cracking due to stress; however, due to the small particle size of the waste powder, it is easy to agglomerate, which affects its performance, so it is modified with a silane coupling agent to improve its dispersibility, thereby further enhancing the crack resistance.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. By adopting the above technical solution, the hydrophobic desulfurized gypsum powder can be used to expand and fill the recycled coarse aggregate. The hydrophobic desulfurized gypsum powder is mixed with water to form a plastic slurry, which becomes a hard solid after drying. It has the function of filling and cutting the capillary pores of the recycled coarse aggregate, thereby reducing the porosity of the recycled coarse aggregate. Since gypsum has strong hygroscopicity, the absorbed water will weaken the bonding force between the gypsum grains, significantly reducing the strength. By hydrophobically modifying the desulfurized gypsum, the water absorption of the desulfurized gypsum can be reduced. At the same time, acrylic resin has excellent bonding properties and can bond the fine cracks of the recycled coarse aggregate itself. Polyethylene glycol has excellent bonding and dispersibility. While further bonding the fine cracks of the recycled coarse aggregate, it can make the desulfurized gypsum powder evenly dispersed, thereby improving the defects of the recycled coarse aggregate such as high water absorption, low density and poor wear resistance. When used in concrete production, it can improve the durability and mechanical properties of the recycled concrete.

[0041] 2. By adopting the above technical solution, using a polycarboxylate superplasticizer, a naphthalene-based superplasticizer, and a sodium sulfate composite as a water reducer, cement usage can be reduced while maintaining concrete strength. The water reducer molecules can be directionally adsorbed on the surface of cement particles, imparting a uniform charge to the cement particles, creating an electrostatic repulsion effect that promotes mutual dispersion of cement particles, disrupting the flocculation structure and releasing trapped water to participate in flow, thereby effectively increasing the fluidity of the concrete mixture. The polycarboxylate superplasticizer and naphthalene-based superplasticizer have a strong dispersing effect on cement, resulting in a high water reduction rate, which maintains good mechanical properties of the concrete.

[0042] 3. By adopting the above technical solution and using waste rubber, the crack resistance of recycled concrete can be effectively improved, the crack expansion rate and the length and width of the crack mouth can be delayed, thereby effectively alleviating the stress concentration phenomenon inside the recycled concrete and reducing the probability of cracking caused by stress in the recycled concrete; modification by silane coupling agent can increase the adhesion of rubber in cement, thereby enhancing the toughness and strength of concrete. At the same time, silane coupling agent can improve the dispersibility of the waste rubber surface, and can improve the problem that the waste rubber powder is prone to agglomeration due to its small particle size, thereby further enhancing the crack resistance. DETAILED DESCRIPTION

[0043] The present application is further described in detail below with reference to the embodiments.

[0044] Preparation Example

[0045] Preparation Example 1

[0046] S1. The desulfurized gypsum was ground into a grinder and passed through a 400-mesh sieve to obtain desulfurized gypsum powder; the desulfurized gypsum powder was calcined at 450 ° C for 4h to obtain anhydrous desulfurized gypsum powder;

[0047] S2 15g of anhydrous desulfurized gypsum powder was added to a mixture of 10g of sodium hydroxide and 5g of sodium sulfate, mixed at 80 ° C for 1.5h, and hydroxylated to obtain pretreated desulfurized gypsum powder;

[0048] S3. The pretreated desulfurized gypsum powder was added to a mixture of 18 g of a silane coupling agent, 2 g of anionic surfactant, and 45 g of a solvent, and mixed at 70°C for 2.5 h to perform surface modification to obtain a hydrophobic desulfurized gypsum powder; the silane coupling agent used in this preparation example was KH-550; the anionic surfactant used was sodium lauryl sulfate; and the solvent used was an ethanol solution.

[0049] Preparation Example 2

[0050] S1. The desulfurized gypsum was ground into a grinder and passed through a 400-mesh sieve to obtain desulfurized gypsum powder; the desulfurized gypsum powder was calcined at 500 ° C for 4.5h to obtain anhydrous desulfurized gypsum powder;

[0051] S2 18g of anhydrous desulfurized gypsum powder was added to a mixture of 12.5g of sodium hydroxide and 6g of sodium sulfate, mixed at 85 ° C for 2h, and hydroxylated to obtain pretreated desulfurized gypsum powder;

[0052] S3. The pretreated desulfurized gypsum powder was added to a mixture of 21 g of a silane coupling agent, 3.5 g of anionic surfactant, and 55 g of a solvent, and mixed at 80°C for 3 h to perform surface modification to obtain a hydrophobic desulfurized gypsum powder; the silane coupling agent used in this preparation example was KH-550; the anionic surfactant used was sodium lauryl sulfate; and the solvent used was an ethanol solution.

[0053] Preparation Example 3

[0054] S1. The desulfurized gypsum was ground into a grinder and passed through a 400-mesh sieve to obtain desulfurized gypsum powder; the desulfurized gypsum powder was calcined at 550 ° C for 5h to obtain anhydrous desulfurized gypsum powder;

[0055] S2 21g of anhydrous desulfurized gypsum powder was added to a mixture of 15g of sodium hydroxide and 7g of sodium sulfate, mixed at 95 ° C for 1h, and hydroxylated to obtain pretreated desulfurized gypsum powder;

[0056] S3. The pretreated desulfurized gypsum powder was added to a mixture of 24 g of a silane coupling agent, 5 g of anionic surfactant, and 65 g of a solvent, and mixed at 90°C for 3.5 h to perform surface modification to obtain a hydrophobic desulfurized gypsum powder; the silane coupling agent used in this preparation example was KH-550; the anionic surfactant used was sodium lauryl sulfate; and the solvent used was an ethanol solution.

[0057] Example

[0058] Example 1

[0059] S1 take waste concrete, which is crushed, washed, dried, and then screened to obtain recycled fine aggregate with a particle size of 5mm or less and 5-20mm recycled coarse aggregate;

[0060] S2 15g of the hydrophobic desulfurization gypsum powder obtained in Preparation Example 1 was added to 30g of water and stirred until completely dissolved, and then 3g of polyethylene glycol, 24g of acrylic resin were added and stirred to obtain a modifier;

[0061] S3 10g of the pretreated recycled concrete obtained by S1 was immersed in the modifier obtained by S2, stirred at a temperature of 45 ° C and a speed of 80 rpm for 8h, filtered after stirring, and dried at 130 ° C for 3h to obtain a hydrophobically modified recycled coarse aggregate;

[0062] S4. The waste rubber was immersed in a 75% mass fraction of ethanol solution for 3h and dried at 80 ℃ for 1.5h to obtain clean waste rubber; the cleaned waste rubber was cut, crushed, and passed through an 80-mesh sieve to obtain waste rubber powder. To 10g of the waste rubber powder were added 20g of a silane coupling agent and 1g of calcium carbonate, and the mixture was stirred and dispersed at a temperature of 60 ℃ and a speed of 400 rpm for 6h. After stirring, the mixture was dried at 120 ℃ for 3h to obtain modified waste rubber powder; the silane coupling agent used in this embodiment is methyltrimethoxysilane;

[0063] S5. 120 g of cement, 850 g of the hydrophobically modified recycled coarse aggregate obtained from S3, 180 g of the recycled fine aggregate obtained from S1, 220 g of sand, 400 g of fly ash, 60 g of silica fume, 20 g of a water reducer, 22 g of the waste rubber powder obtained from S4, and 80 g of water are mixed and stirred evenly to obtain recycled concrete; the water reducer includes a polycarboxylic acid high-efficiency water reducer, a naphthalene-based high-efficiency water reducer, and sodium sulfate, in a weight ratio of 1:0.3:0.08.

[0064] Example 2

[0065] S1 take waste concrete, which is crushed, washed, dried, and then screened to obtain recycled fine aggregate with a particle size of 5mm or less and 5-20mm recycled coarse aggregate;

[0066] S2 21g of the hydrophobic desulfurization gypsum powder obtained in Preparation Example 1 was added to 35g of water and stirred until completely dissolved, and then 4g of polyethylene glycol, 30g of acrylic resin were added and stirred to obtain a modifier;

[0067] S3 13g of pretreated recycled concrete obtained by S1 was impregnated in the modifier obtained by S2 and stirred at a temperature of 40 ° C and a speed of 70 rpm for 9h. After stirring, the mixture was filtered and dried at 140 ° C for 3.5h to obtain a hydrophobically modified recycled coarse aggregate;

[0068] S4. The waste rubber was immersed in a 75% ethanol solution by mass for 3.5h and dried at 90 ° C for 2h to obtain clean waste rubber; the cleaned waste rubber was cut, crushed, and passed through an 80-mesh sieve to obtain waste rubber powder. To 12.5g of waste rubber powder were added 26g of a silane coupling agent and 1.5g of calcium carbonate. The mixture was stirred and dispersed at a temperature of 65 ° C and a speed of 450 rpm for 7h. After stirring, the mixture was dried at 130 ° C for 3.5h to obtain modified waste rubber powder; the silane coupling agent used in this embodiment is methyltrimethoxysilane;

[0069] S5. 160 g of cement, 850 g of the hydrophobically modified recycled coarse aggregate obtained from S3, 230 g of the recycled fine aggregate obtained from S1, 290 g of sand, 525 g of fly ash, 80 g of silica fume, 20 g of a water reducer, 22 g of the waste rubber powder obtained from S4, and 100 g of water are mixed and stirred evenly to obtain recycled concrete; the water reducer includes a polycarboxylic acid high-efficiency water reducer, a naphthalene-based high-efficiency water reducer, and sodium sulfate, in a weight ratio of 1:0.3:0.08.

[0070] Example 3

[0071] S1 take waste concrete, which is crushed, washed, dried, and then screened to obtain recycled fine aggregate with a particle size of 5mm or less and 5-20mm recycled coarse aggregate;

[0072] S2 27g of the hydrophobic desulfurization gypsum powder obtained in Preparation Example 1 was added to 40g of water and stirred until completely dissolved, and then 5g of polyethylene glycol, 36g of acrylic resin were added and stirred to obtain a modifier;

[0073] S3 10g of the pretreated recycled concrete obtained by S1 was immersed in the modifier obtained by S2, stirred at a temperature of 50 ° C and a speed of 85 rpm for 7h, filtered after stirring, and dried at 120 ° C for 4h to obtain a hydrophobically modified recycled coarse aggregate;

[0074] S4. The waste rubber was immersed in a 75% mass fraction of ethanol solution for 4h and dried at 95 ℃ for 2.5h to obtain clean waste rubber; the cleaned waste rubber was cut, crushed, and passed through an 80-mesh sieve to obtain waste rubber powder. To 15g of the waste rubber powder were added 32g of a silane coupling agent and 2g of calcium carbonate, and the mixture was stirred and dispersed at a temperature of 70 ℃ and a speed of 500 rpm for 8h. After stirring, the mixture was dried at 140 ℃ for 2.5h to obtain a modified waste rubber powder; the silane coupling agent used in this embodiment is methyltrimethoxysilane;

[0075] S5. 200 g of cement, 850 g of the hydrophobically modified recycled coarse aggregate obtained from S3, 280 g of the recycled fine aggregate obtained from S1, 360 g of sand, 650 g of fly ash, 120 g of silica fume, 20 g of a water reducer, 22 g of the waste rubber powder obtained from S4, and 120 g of water are mixed and stirred evenly to obtain recycled concrete; the water reducer includes a polycarboxylic acid high-efficiency water reducer, a naphthalene-based high-efficiency water reducer, and sodium sulfate, in a weight ratio of 1:0.3:0.08.

[0076] Example 4

[0077] The difference between Example 4 and Example 1 is that the mass of the hydrophobically modified recycled coarse aggregate used in S5 of Example 4 is 925 g.

[0078] Example 5

[0079] The difference between Example 5 and Example 1 is that the mass of the hydrophobically modified recycled coarse aggregate used in S5 of Example 5 is 1000 g.

[0080] Example 6

[0081] The difference between Example 6 and Example 1 is that the mass of the water reducing agent used in S5 of Example 6 is 27 g.

[0082] Example 7

[0083] The difference between Example 7 and Example 1 is that the mass of the water reducer used in S5 of Example 7 is 35 g.

[0084] Example 8

[0085] The difference between Example 8 and Example 1 is that the weight ratio of the water reducer polycarboxylic acid high-efficiency water reducer, naphthalene-based high-efficiency water reducer, and sodium sulfate used in S5 of Example 8 is 1:0.55:0.12.

[0086] Example 9

[0087] The difference between Example 9 and Example 1 is that the weight ratio of the water reducer polycarboxylic acid high-efficiency water reducer, naphthalene-based high-efficiency water reducer, and sodium sulfate used in S5 of Example 9 is 1:0.8:0.16.

[0088] Example 10

[0089] The difference between Example 10 and Example 1 is that the mass of the modified waste rubber powder used in S5 of Example 10 is 28 g.

[0090] Example 11

[0091] The difference between Example 11 and Example 1 is that the mass of the modified waste rubber powder used in S5 of Example 11 is 35 g.

[0092] Example 12

[0093] The difference between Example 12 and Example 1 is that the hydrophobic desulfurization gypsum powder used in S2 of Example 12 comes from Preparation Example 2.

[0094] Example 13

[0095] The difference between Example 13 and Example 1 is that the hydrophobic desulfurization gypsum powder used in S2 of Example 12 comes from Preparation Example 3.

[0096] Comparative Example

[0097] Comparative Example 1

[0098] The difference between Comparative Example 1 and Example 1 is that the mass of the hydrophobically modified recycled coarse aggregate used in S5 of Comparative Example 1 is 750 g.

[0099] Comparative Example 2

[0100] The difference between Comparative Example 2 and Example 1 is that the mass of the hydrophobically modified recycled coarse aggregate used in S5 of Comparative Example 2 is 1100 g.

[0101] Comparative Example 3

[0102] The difference between Comparative Example 3 and Example 1 is that the mass of the water reducing agent used in S5 of Comparative Example 3 is 0 g.

[0103] Comparative Example 4

[0104] The difference between Comparative Example 4 and Example 1 is that the mass of the water reducing agent used in S5 of Comparative Example 4 is 42 g.

[0105] Comparative Example 5

[0106] The difference between Comparative Example 5 and Example 1 is that the weight ratio of the water reducer polycarboxylic acid high-efficiency water reducer, naphthalene-based high-efficiency water reducer, and sodium sulfate used in S5 of Comparative Example 5 is 1:0.1:0.04.

[0107] Comparative Example 6

[0108] The difference between Comparative Example 6 and Example 1 is that the weight ratio of the water reducer polycarboxylic acid high-efficiency water reducer, naphthalene-based high-efficiency water reducer, and sodium sulfate used in S5 of Comparative Example 6 is 1:1.1:0.2.

[0109] Comparative Example 7

[0110] The difference between Comparative Example 7 and Example 1 is that the mass of the modified waste rubber used in S5 of Comparative Example 7 is 0 g.

[0111] Comparative Example 8

[0112] The difference between Comparative Example 8 and Example 1 is that the mass of the modified waste rubber used in S5 in Comparative Example 8 is 42 g.

[0113] Comparative Example 9

[0114] The difference between Comparative Example 9 and Example 1 is that the water reducer used in S5 of Comparative Example 9 is a polycarboxylic acid high-efficiency water reducer with a mass of 30 g.

[0115] Comparative Example 10

[0116] The difference between Comparative Example 10 and Example 1 is that in S5 of Comparative Example 10, unmodified ordinary recycled coarse aggregate with a mass of 1000 g is used.

[0117] Comparative Example 11

[0118] The difference between Comparative Example 11 and Example 1 is that the desulfurized gypsum powder used in S2 of Comparative Example 11 is unmodified ordinary desulfurized gypsum powder.

[0119] Performance testing

[0120] The concrete obtained in Example 1-13 and Comparative Example 1-11 was used to make cubic specimens with a side length of 30 cm as test samples. After the test samples were cured for 28 days, the performance of the test samples was tested.

[0121] 1. The compressive strength and splitting tensile strength of the test samples of Examples 1-13 and Comparative Examples 1-12 were tested using GB / T 50081-2016 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The specific test results are shown in Table 1.

[0122] 2. The number of cracks per unit area and the total cracked area per unit area of ​​the test samples of Examples 1-13 and Comparative Examples 1-12 were tested using GB / T 50081-2016 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete". The specific test results are shown in Table 1.

[0123] The specific test results are as follows:

[0124] Table 1 Performance test results

[0125]

[0126]

[0127] As can be seen from the data in Table 1, the high-strength recycled concrete provided by this application not only has strong compressive strength and splitting tensile strength, but also has strong anti-permeability. The compressive strength reaches 73.0-75.9 MPa; the splitting compressive strength reaches 10.99-12.52 MPa; the maximum number of cracks is 4; the total crack area per unit area is 54.4 mm 2 / m 2 .

[0128] It can be seen from the test results of Examples 1-3 that the process conditions for preparing high-strength recycled concrete provided in this application are all conducive to improving the compressive strength, splitting tensile strength and impermeability of the recycled concrete.

[0129] It can be seen from the test results of Examples 1, 4, 5 and Comparative Examples 1, 2, and 10 that the hydrophobically modified recycled coarse aggregate used in S5 of the present application is significantly more conducive to improving the compressive strength, splitting tensile strength and crack resistance of the concrete than the unmodified concrete; and when the mass of the hydrophobically modified recycled coarse aggregate increases, the compressive strength of the concrete test sample gradually increases, the splitting tensile strength also increases accordingly, and the number of cracks and the total crack area per unit area decrease slightly; however, when the mass of the hydrophobically modified recycled coarse aggregate exceeds 1000 g, the compressive strength and splitting tensile strength of the concrete test sample no longer continue to increase, and the number of cracks and the crack area increase slightly.

[0130] It can be seen from the test results of Examples 1, 6, 7 and Comparative Examples 3 and 4 that when the present application uses a water reducer, the compressive strength, splitting tensile strength and impermeability of the concrete are all improved; when the mass of the water reducer used increases, the compressive strength of the concrete test sample gradually increases, the splitting tensile strength also increases accordingly, and the number of cracks and the total crack area per unit area gradually decrease; however, when the mass of the water reducer exceeds 35g, the compressive strength and splitting tensile strength of the concrete test sample begin to decrease, and the number of cracks and the crack area begin to increase.

[0131] It can be seen from the test results of Examples 1, 8, 9 and Comparative Examples 5, 6, and 9 that when the polycarboxylic acid high-efficiency water-reducing agent, naphthalene-based high-efficiency water-reducing agent, and sodium sulfate water-reducing agent used in S5 of the present application are significantly more conducive to improving the compressive strength, splitting tensile strength, and crack resistance of concrete than using a single water-reducing agent, calcium lignosulfonate; and when the ratio of the polycarboxylic acid high-efficiency water-reducing agent, the naphthalene-based high-efficiency water-reducing agent, and the sodium sulfate varies within the range of 1: (0.3-0.8): (0.08-0.16), the compressive strength, splitting tensile strength, number of cracks, and total crack area per unit area of ​​the concrete test sample do not change much. When the ratio of the three is lower than or exceeds this ratio, the compressive strength and splitting tensile strength of the concrete are significantly reduced, and the number of cracks and the total crack area per unit area are significantly increased.

[0132] It can be seen from the test results of Examples 1, 10, 11 and Comparative Examples 7 and 8 that when the mass of the modified waste rubber powder used in S5 of the present application increases, the compressive strength of the concrete test sample gradually increases, the splitting tensile strength also increases accordingly, and the number of cracks and the total crack area per unit area gradually decrease; however, when the mass of the modified waste rubber powder exceeds 35g, the compressive strength and splitting tensile strength of the concrete test sample begin to decrease, and the number of cracks and the crack area begin to increase.

[0133] It can be seen from the test results of Examples 1, 12, 13 and Comparative Example 11 that the preparation process for preparing hydrophobic desulfurized gypsum powder provided in the present application is beneficial to improving the compressive strength, splitting tensile strength and impermeability of recycled concrete, and the change within the parameter range has little effect on the results; however, when unmodified ordinary desulfurized gypsum powder is used, the compressive strength and splitting tensile strength of the obtained concrete are significantly reduced, and the number of cracks and the crack area are significantly increased.

[0134] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high-strength recycled concrete, characterized by: The raw materials include, by weight, 120-200 parts of cement, 850-1000 parts of hydrophobically modified recycled coarse aggregate, 180-280 parts of recycled fine aggregate, 220-360 parts of sand, 400-650 parts of fly ash, 60-120 parts of silica fume, 20-35 parts of water reducer, 22-35 parts of modified waste rubber powder, and 80-120 parts of water; The hydrophobically modified recycled coarse aggregate raw material comprises the following components: 10-16 parts of recycled coarse aggregate, 15-27 parts of hydrophobic desulfurized gypsum powder, 3-5 parts of polyethylene glycol, 24-36 parts of acrylic resin, and 30-40 parts of water; The water reducer comprises a polycarboxylic acid high-efficiency water reducer, a naphthalene-based high-efficiency water reducer, and sodium sulfate, with a weight ratio of 1: (0.3-0.8): (0.08-0.16); The method for preparing the hydrophobically modified recycled coarse aggregate comprises the following steps: S1. Take waste concrete, crush it, wash it, dry it, and screen it to obtain recycled coarse aggregate and recycled fine aggregate after crushing; S2. The obtained recycled coarse aggregate was immersed in a modifier for modification. After the modification was completed, the hydrophobically modified recycled coarse aggregate was obtained by filtration and drying; The preparation method of the modifier comprises the following steps: Add 15-27 parts of hydrophobic desulfurized gypsum powder to 30-40 parts of water, stir until completely dissolved, add 3-5 parts of polyethylene glycol and 24-36 parts of acrylic resin, stir evenly to obtain a modifier; The method for preparing the hydrophobic desulfurized gypsum powder comprises the following steps: S1. The desulfurized gypsum was ground and sieved to obtain desulfurized gypsum powder; the desulfurized gypsum powder was calcined to obtain anhydrous desulfurized gypsum powder; S2. 15-21 parts of anhydrous desulfurized gypsum powder are added to a mixture of 10-15 parts of sodium hydroxide and 5-7 parts of sodium sulfate, heated and mixed to obtain pretreated desulfurized gypsum powder; S3. The pretreated desulfurization gypsum powder is added to a mixture of 18-24 parts of a silane coupling agent, 2-5 parts of anionic surfactant, 45-65 parts of a solvent, heated and mixed to obtain a hydrophobic desulfurization gypsum powder; The method for treating the modified waste rubber powder comprises the following steps: S1. The waste rubber is washed, dried, crushed, and sieved to obtain waste rubber powder; S2. Add 20-32 parts of silane coupling agent and 1-2 parts of calcium carbonate to 10-15 parts of waste rubber powder, stir and disperse, and then dry to obtain modified waste rubber powder.

2. A method for preparing the high-strength recycled concrete according to claim 1, characterized in that: The following steps are involved: Mix 120-200 parts of cement, 850-1000 parts of hydrophobically modified recycled coarse aggregate, 180-280 parts of recycled fine aggregate, 220-360 parts of sand, 400-650 parts of fly ash, 60-120 parts of silica fume, 20-35 parts of water reducer, 22-35 parts of modified waste rubber powder, and 80-120 parts of water, stir well, and obtain recycled concrete.

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