Modified waste rubber powder with temperature-sensitive property and preparation method and application thereof

Abstract

The application relates to the field of environment-friendly materials, and specifically discloses a modified waste rubber powder with temperature-sensitive characteristics as well as a preparation method and application thereof. The preparation method of the modified waste rubber powder comprises the following steps: S1, waste rubber powder pretreatment: after the waste rubber powder is cleaned to remove impurities, the waste rubber powder is immersed in a sodium hydroxide solution, then washed with water and dried, and pretreated waste rubber powder is prepared; S2, the pretreated waste rubber powder is mixed with a dilute sulfuric acid solution and dried, and initial modified waste rubber powder is prepared; S3, the initial modified waste rubber powder is mixed and dispersed with carboxylated nanosilica, then pressure impregnation treatment is carried out in a modification liquid, and then drying is carried out, and modified waste rubber powder is prepared; the modification liquid mainly comprises PAMAM, polyisopropyl acrylamide, genipin, polyvinyl alcohol and hydroxypropyl beta-cyclodextrin; the application also discloses the modified waste rubber powder prepared by the above method and application of the modified waste rubber powder in concrete materials, and the application has the advantages that the waste rubber powder is modified to improve the strength and durability of the waste rubber powder applied in concrete.

Description

Technical Field

[0001] This application relates to the field of environmentally friendly materials, and more specifically, to a modified waste rubber powder with temperature-sensitive properties, its preparation method, and its application. Background Technology

[0002] Waste rubber powder refers to powdered rubber materials obtained by crushing and processing waste rubber products. It mainly originates from waste tires and other rubber products, which are difficult to degrade under natural conditions, resulting in serious resource waste. Applying waste rubber powder to concrete not only effectively utilizes these wastes but also achieves resource reuse, aligning with the concept of sustainable development. Furthermore, research has found that incorporating waste rubber powder into concrete can form structural deformation centers that absorb strain energy, improving the concrete's impact resistance and seismic resistance. Additionally, waste rubber powder can reduce concrete volume shrinkage and prevent crack formation because its high elastic modulus and tensile strength effectively inhibit concrete shrinkage deformation.

[0003] Although the application of waste adhesive powder in concrete has achieved remarkable results, the compatibility between waste adhesive powder and cement matrix is ​​currently poor, and the strength of concrete decreases significantly with the increase of waste adhesive powder production.

[0004] As the construction industry continues to develop, the demand for high-performance concrete is increasing. Although traditional concrete can meet most engineering requirements, its strength and durability still need to be improved. Therefore, it is necessary to modify waste adhesive powder and add it to further improve the strength and crack resistance of concrete, thereby enhancing its durability. Summary of the Invention

[0005] In order to modify waste rubber powder to improve its strength and durability in concrete, this application provides a modified waste rubber powder with temperature-sensitive properties, its preparation method and application.

[0006] In a first aspect, this application provides a method for preparing modified waste rubber powder with temperature-sensitive properties, using the following technical solution:

[0007] A method for preparing modified waste rubber powder with temperature-sensitive properties includes the following steps:

[0008] S1. Waste rubber powder pretreatment: After cleaning the waste rubber powder to remove impurities, it is soaked in sodium hydroxide solution, washed with water and dried to obtain pretreated waste rubber powder.

[0009] S2. The pretreated waste rubber powder is mixed with dilute sulfuric acid solution and then dried to obtain the initially modified waste rubber powder.

[0010] S3. After mixing and dispersing the pre-modified waste rubber powder with carboxylated nano-silica, the mixture is impregnated under pressure in the modification solution and then dried to obtain modified waste rubber powder.

[0011] The modified liquid mainly includes PAMAM, polyisopropylacrylamide, genipin, polyvinyl alcohol, and hydroxypropyl β-cyclodextrin.

[0012] By adopting the above technical solution, this application first soaks the waste rubber powder in a sodium hydroxide solution to remove the zinc stearate on the surface of the waste rubber powder. Then, the pretreated waste rubber powder is impregnated in a dilute sulfuric acid solution to introduce oxygen-containing functional groups such as hydroxyl or carboxyl groups onto the surface of the waste rubber powder. Then, it is mixed with carboxylated nano-silica and impregnated under pressure in a modification solution. In the modification solution, PAMAM, as a water-soluble polyamide-amine dendritic macromolecule, contains a large number of amino functional groups that, under acidic conditions, combine with the carboxyl groups and other oxygen-containing functional groups introduced from the waste rubber powder to form... The amide bond, and the amino group in PAMAM can also form a chemical bond with the carboxyl functional group in the carboxylated nano silica. PAMAM can improve the interfacial bonding between the carboxylated nano silica and the waste adhesive powder, thereby introducing the carboxylated nano silica material into the waste adhesive powder. Through the filling effect and interfacial effect of the nanomaterial, the compatibility between the waste adhesive powder and the concrete matrix is ​​improved. Nano silica can also react with calcium hydroxide in concrete to generate hydrated calcium silicate gel, which further enhances the interfacial bonding force and improves the strength of concrete.

[0013] Furthermore, in this application, polyisopropylacrylamide (PPAMAM) is used as a temperature-sensitive material. When the temperature rises, PPAMAM absorbs moisture, causing it to expand in volume and fill tiny cracks in the concrete. When the temperature drops, PPAMAM releases moisture and shrinks in volume. This characteristic allows the waste adhesive powder to regulate the internal stress state of the concrete during temperature changes, thereby reducing crack formation and improving the durability of the concrete. The addition of genipin enables crosslinking between PPAMAM and PAMAM, and also enables crosslinking between PAMAM and carboxylated nano-dioxide. The cross-linking between amide bonds formed by silicon dioxide and the cross-linking between amide bonds formed by PAMAM and the carboxyl groups of waste rubber powder ultimately form a macromolecular structure. Moreover, its surface contains a large number of amino groups, which improves its compatibility with the concrete matrix. The bonding effect of polyvinyl alcohol enhances the combination of waste rubber powder and carboxylated nano-silica, resulting in a better reinforcing effect. The addition of hydroxypropyl β-cyclodextrin, utilizing its oleophilic cavity structure and hydrophilic shell structure, achieves the coating of the oleophilic part on the surface of the modified waste rubber powder, improves the compatibility between the modified waste rubber powder and the concrete matrix, and further enhances the reinforcing effect.

[0014] Optionally, in step S2, after the pretreated waste adhesive powder is mixed with dilute sulfuric acid solution and dried, it is also added to the impregnation solution for impregnation treatment and then dried. The impregnation solution mainly includes maleic anhydride, initiator and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0015] By adopting the above technical solution, the pretreated waste rubber powder in this application is impregnated and dried in a dilute sulfuric acid solution, and then treated in the impregnation solution. Under the action of an initiator, maleic anhydride undergoes a grafting reaction with the waste rubber powder, introducing carboxyl functional groups onto the waste rubber powder. This allows it to crosslink with PAMAM and polyisopropylacrylamide in the modification solution. N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, as a silane coupling agent, contains a silane group and two amino groups. Through the hydrolysis of its silane group to form silanol, it forms a coupling effect with the waste rubber powder and introduces amino groups. It can form chemical bonds with carboxylated nano-silica and can also crosslink with the modifier in the modification solution. Ultimately, the waste rubber powder in this application not only introduces temperature-sensitive... The material is polyisopropylacrylamide (PNIPAN), which is also loaded with nano-silica. The nano-silica can fill the gaps between waste adhesive powder and concrete, enhance the interfacial bonding force between waste adhesive powder and concrete, thereby improving the compatibility between waste adhesive powder and concrete matrix and playing a reinforcing role. Moreover, the macromolecular network structure formed between PNIPAN, waste adhesive powder and modified liquid further solves the problem of strength loss caused by the addition of waste adhesive powder and improves strength. Furthermore, since the PNIPAN macromolecular polymer has a certain elastic modulus, it can play a certain volume buffering role for the shrinkage or expansion of polyisopropylacrylamide (PNIPAN) due to temperature changes, further improving its self-curing performance and improving the durability of concrete.

[0016] Optionally, the modified liquid includes the following raw materials in parts by weight:

[0017] 15-22 parts PAMAM, 25-35 parts polyisopropylacrylamide, 2-4 parts genipin, 3-5 parts polyvinyl alcohol, 10-20 parts hydroxypropyl β-cyclodextrin, and 40-60 parts water.

[0018] Optionally, the impregnation solution comprises the following raw materials in parts by weight:

[0019] 10-18 parts maleic anhydride, 3-5 parts initiator, 20-30 parts N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25-35 parts water, 10-20 parts ethanol, and 1-3 parts sodium dodecyl sulfate.

[0020] Optionally, the initiator in the impregnation solution may be a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:(1.2-1.5).

[0021] By adopting the above technical solutions and controlling the above conditions, the modification effect of waste adhesive powder is better, and the overall performance of concrete compatibility, reinforcement and durability is better.

[0022] Optionally, in step S3, when the modified liquid is impregnated under pressure, the impregnation temperature is 55-65℃ and the impregnation pressure is 2-3MPa.

[0023] By adopting the above technical solution and using the above impregnation temperature and pressure, it is more conducive to the cross-linking modification of the primary modified waste rubber powder by the active substances in the modified liquid, thereby improving its comprehensive performance.

[0024] Optionally, the carboxylated nano-silica is prepared by the following method:

[0025] Nano-silica, carboxymethyl cellulose, and water were mixed in a mass ratio of 1:(0.1-0.2):(4-6) to obtain mixture A;

[0026] Mixture B was prepared by mixing succinic anhydride and ethanol at a mass ratio of 1:(2-3).

[0027] Mixture A is heated to 50-60℃, and mixture B is added to mixture A under a nitrogen atmosphere. After reacting for 1-2 hours, the mixture is centrifuged, washed with water, and dried to obtain carboxylated nano-silica. The mass ratio of nano-silica to succinic anhydride is 1:(0.4-0.6).

[0028] By adopting the above technical solution, this application uses succinic anhydride as a carboxylation modifying agent. Nano-silica is first dispersed in an aqueous solvent, then succinic anhydride is dissolved in ethanol and added to the dispersion of nano-silica. There are a large number of hydroxyl groups on the surface of nano-silica. Succinic anhydride undergoes ring-opening in heating and aqueous solvent to generate linear molecules with two carboxyl groups. These molecules react with the hydroxyl groups on nano-silica, thereby introducing carboxyl functional groups to the surface of nano-silica, thus achieving carboxylation modification of nano-silica. The introduction of carboxyl groups on the surface of nano-silica allows them to interact with the main components in the modification solution and soaking solution to achieve the modification effect on waste rubber powder.

[0029] Optionally, in step S1, the mass concentration of the sodium hydroxide solution is 45-50%, and the amount of sodium hydroxide solution added is 4-6 times the mass of the waste adhesive powder.

[0030] In step S2, the dilute sulfuric acid is selected as a sulfuric acid solution with a mass concentration of 60-65%, and the amount of dilute sulfuric acid solution added is 5-8 times the mass of the pretreated waste rubber powder. The mixing time between the pretreated waste rubber powder and the dilute sulfuric acid solution is 40-60 min, and the mixing temperature is 50-60℃. In step S3, the mass ratio of the initially modified waste rubber powder to the carboxylated nano-silica is 1:(0.2-0.3), and the amount of the modified solution added is 8-10 times the mass of the initially modified waste rubber powder.

[0031] Secondly, this application provides a modified waste rubber powder with temperature-sensitive properties, using the following technical solution: a modified waste rubber powder with temperature-sensitive properties is prepared by the aforementioned preparation method.

[0032] By adopting the above technical solution and the method in this application, the modification treatment of waste rubber powder is achieved. On the one hand, the thermosensitive polymer polyisopropylacrylamide (PNIPAM) is introduced onto the surface of the waste rubber powder particles, giving the waste rubber powder thermosensitive properties. Under specific temperature conditions, it changes its ability to absorb or release water, thereby achieving self-regulating supply of internal moisture. This allows the waste rubber powder to regulate the stress state inside the concrete when the temperature changes, thereby reducing the generation of cracks and improving the durability of the concrete. On the other hand, the waste rubber powder and carboxylated nano-silica composite in this application solve the problem of reduced concrete strength due to the addition of waste rubber powder. Moreover, the addition of the modifying liquid improves the interfacial bonding force between the two and the compatibility between the modified waste rubber powder and the concrete matrix, thus playing a reinforcing role.

[0033] Thirdly, this application provides an application of modified waste rubber powder with temperature-sensitive properties, using the following technical solution:

[0034] Application of a temperature-sensitive modified waste adhesive powder in concrete.

[0035] By adopting the above technical solution, when the modified waste adhesive powder in this application is used in concrete, it not only significantly improves its durability but also has excellent strength and mechanical properties.

[0036] In summary, this application has the following beneficial effects:

[0037] The method described in this application achieves the modification treatment of waste rubber powder. On the one hand, a thermosensitive polymer, polyisopropylacrylamide (PNIPAM), is introduced onto the surface of the waste rubber powder particles, giving it thermosensitive properties. Under specific temperature conditions, it changes its ability to absorb or release water, thereby achieving self-regulating internal moisture supply. This allows the waste rubber powder to regulate the internal stress state of concrete when the temperature changes, thus reducing crack formation and improving concrete durability. On the other hand, the waste rubber powder combined with carboxylated nano-silica in this application solves the problem of reduced concrete strength due to the addition of waste rubber powder. Furthermore, the addition of a modifying liquid improves the interfacial bonding force between the two and the compatibility between the modified waste rubber powder and the concrete matrix, thus playing a reinforcing role. Detailed Implementation

[0038] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0039] Example 1

[0040] A method for preparing modified waste rubber powder with temperature-sensitive properties includes the following steps:

[0041] S1. Waste rubber powder pretreatment: After cleaning and removing impurities, the waste rubber powder is immersed in a sodium hydroxide solution with a mass concentration of 48%, then washed with water and dried to obtain pretreated waste rubber powder. The amount of sodium hydroxide solution added is 5 times the mass of the waste rubber powder.

[0042] S2. The pretreated waste rubber powder is mixed with a 65% dilute sulfuric acid solution and then dried to obtain pre-modified waste rubber powder. The amount of dilute sulfuric acid solution added is 6 times the mass of the pretreated waste rubber powder, and the mixing time of the pretreated waste rubber powder and the dilute sulfuric acid solution is 50 min, and the mixing temperature is 55℃.

[0043] S3. The pre-modified waste rubber powder and carboxylated nano-silica are mixed and dispersed at a mass ratio of 1:0.25, then impregnated in the modification solution under pressure and dried. The amount of modification solution added is 9 times the mass of the pre-modified waste rubber powder, and the impregnation temperature is 60℃, the impregnation pressure is 2.5MPa, and the impregnation time is 1h to obtain the modified waste rubber powder.

[0044] The modified solution was prepared by mixing 20g PAMAM, 30g polyisopropylacrylamide, 3g genipin, 4g polyvinyl alcohol, 15g hydroxypropyl β-cyclodextrin and 50g water.

[0045] Carboxylated nano-silica was prepared by the following method:

[0046] Mixture A was prepared by mixing nano-silica, carboxymethyl cellulose and water in a mass ratio of 1:0.1:5;

[0047] Mixture B was prepared by mixing succinic anhydride and ethanol at a mass ratio of 1:2.5.

[0048] Mixture A was heated to 55°C, and mixture B was added to mixture A under a nitrogen atmosphere. After reacting for 1.5 h, the mixture was centrifuged, washed with water, and dried to obtain carboxylated nano-silica.

[0049] Example 2

[0050] A method for preparing modified waste rubber powder with temperature-sensitive properties includes the following steps:

[0051] S1. Waste rubber powder pretreatment: After cleaning the waste rubber powder to remove impurities, it is immersed in a sodium hydroxide solution with a mass concentration of 45%, then washed with water and dried to obtain pretreated waste rubber powder, wherein the amount of sodium hydroxide solution added is 4 times the mass of the waste rubber powder.

[0052] S2. The pretreated waste rubber powder is mixed with a 60% mass concentration dilute sulfuric acid solution and then dried to obtain the pre-modified waste rubber powder. The amount of dilute sulfuric acid solution added is 5 times the mass of the pretreated waste rubber powder, and the mixing time of the pretreated waste rubber powder and the dilute sulfuric acid solution is 40 min, and the mixing temperature is 60℃.

[0053] S3. The pre-modified waste rubber powder and carboxylated nano-silica are mixed and dispersed at an addition mass ratio of 1:0.2, then impregnated in the modification liquid under pressure and dried. The amount of modification liquid added is 8 times the mass of the pre-modified waste rubber powder, and the impregnation temperature is 55℃, the impregnation pressure is 2MPa, and the impregnation time is 2h to obtain modified waste rubber powder.

[0054] The modified solution was prepared by mixing 15g PAMAM, 25g polyisopropylacrylamide, 2g genipin, 3g polyvinyl alcohol, 10g hydroxypropyl β-cyclodextrin and 40g water.

[0055] Carboxylated nano-silica was prepared by the following method:

[0056] Mixture A was prepared by mixing nano-silica, carboxymethyl cellulose and water in a mass ratio of 1:0.1:4;

[0057] Mixture B was prepared by mixing succinic anhydride and ethanol at a mass ratio of 1:2.

[0058] Mixture A was heated to 50°C, and mixture B was added to mixture A under a nitrogen atmosphere. After reacting for 2 hours, the mixture was centrifuged, washed with water, and dried to obtain carboxylated nano-silica.

[0059] Example 3

[0060] A method for preparing modified waste rubber powder with temperature-sensitive properties includes the following steps:

[0061] S1. Waste rubber powder pretreatment: After cleaning the waste rubber powder to remove impurities, it is immersed in a 50% sodium hydroxide solution, washed with water and dried to obtain pretreated waste rubber powder, wherein the amount of sodium hydroxide solution added is 6 times the mass of the waste rubber powder.

[0062] S2. The pretreated waste rubber powder is mixed with a 65% dilute sulfuric acid solution and then dried to obtain pre-modified waste rubber powder. The amount of dilute sulfuric acid solution added is 8 times the mass of the pretreated waste rubber powder, and the mixing time of the pretreated waste rubber powder and the dilute sulfuric acid solution is 60 min, and the mixing temperature is 50℃.

[0063] S3. The pre-modified waste rubber powder and carboxylated nano-silica are mixed and dispersed at a mass ratio of 1:0.3, then impregnated in the modification solution under pressure and dried. The amount of modification solution added is 10 times the mass of the pre-modified waste rubber powder, and the impregnation temperature is 65℃, the impregnation pressure is 3MPa, and the impregnation time is 40min to obtain the modified waste rubber powder.

[0064] The modified solution was prepared by mixing 22g PAMAM, 35g polyisopropylacrylamide, 4g genipin, 5g polyvinyl alcohol, 20g hydroxypropyl β-cyclodextrin and 60g water.

[0065] Carboxylated nano-silica was prepared by the following method:

[0066] Mixture A was prepared by mixing nano-silica, carboxymethyl cellulose and water in a mass ratio of 1:0.2:6;

[0067] Mixture B was prepared by mixing succinic anhydride and ethanol at a mass ratio of 1:3.

[0068] Mixture A was heated to 60°C, and mixture B was added to mixture A under a nitrogen atmosphere. After reacting for 1 hour, the mixture was centrifuged, washed with water, and dried to obtain carboxylated nano-silica.

[0069] Example 4

[0070] A method for preparing a temperature-sensitive modified waste rubber powder is carried out according to the method in Example 1, except that in step S2, after mixing and drying the pretreated waste rubber powder with a dilute sulfuric acid solution, it is further added to an impregnation solution for impregnation treatment for 40 minutes at an impregnation temperature of 55°C, and then dried to obtain the initial modified waste rubber powder. The amount of impregnation solution added is 5 times the mass of the pretreated waste rubber powder, and the impregnation solution is obtained by mixing the following raw materials:

[0071] 15g maleic anhydride, 4g initiator, 25g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 30g water, 15g ethanol, and 2g sodium dodecyl sulfate.

[0072] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.3.

[0073] Example 5

[0074] A method for preparing a temperature-sensitive modified waste rubber powder is carried out according to the method in Example 1, except that in step S2, after mixing and drying the pretreated waste rubber powder with a dilute sulfuric acid solution, it is further added to an impregnation solution for impregnation for 30 minutes at an impregnation temperature of 60°C, and then dried to obtain the initial modified waste rubber powder. The amount of impregnation solution added is four times the mass of the pretreated waste rubber powder, and the impregnation solution is obtained by mixing the following raw materials:

[0075] 10g maleic anhydride, 3g initiator, 20g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25g water, 10g ethanol, and 1g sodium dodecyl sulfate.

[0076] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.2.

[0077] Example 6

[0078] A method for preparing a temperature-sensitive modified waste rubber powder is carried out according to the method in Example 1, except that in step S2, after the pretreated waste rubber powder is mixed with dilute sulfuric acid solution and dried, it is further added to an impregnation solution for impregnation treatment for 50 minutes at an impregnation temperature of 50°C, and then dried to obtain the initial modified waste rubber powder. The amount of impregnation solution added is 6 times the mass of the pretreated waste rubber powder, and the impregnation solution is obtained by mixing the following raw materials:

[0079] 18g maleic anhydride, 5g initiator, 30g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 35g water, 20g ethanol, and 3g sodium dodecyl sulfate.

[0080] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.5.

[0081] Example 7

[0082] A method for preparing a modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 4, except that N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in the impregnation solution is replaced with KH-550 in equal amounts.

[0083] Example 8

[0084] A method for preparing a modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 4, except that maleic anhydride is not added to the impregnation solution raw material.

[0085] Comparative Example 1

[0086] A method for preparing a modified waste adhesive powder with temperature-sensitive properties is carried out according to the method in Example 1, except that step S3 is not performed.

[0087] Comparative Example 2

[0088] A method for preparing a modified waste adhesive powder with temperature-sensitive properties is carried out according to the method in Example 1, except that PAMAM is not added to the modification liquid in step S3.

[0089] Comparative Example 3

[0090] A method for preparing a modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that in step S3, hydroxypropyl β-cyclodextrin in the modified liquid is replaced with polyvinyl alcohol in equal amounts.

[0091] Comparative Example 4

[0092] A method for preparing a modified waste adhesive powder with temperature-sensitive properties is carried out according to the method in Example 1, except that genipin is not added to the modification liquid in step S3.

[0093] Comparative Example 5

[0094] A method for preparing a modified waste adhesive powder with temperature-sensitive properties is carried out according to the method in Example 1, except that the modification liquid in step S3 is obtained by mixing KH-550 silane coupling agent and water at a mass ratio of 1:4.

[0095] Comparative Example 6

[0096] A method for preparing a modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that polyisopropylacrylamide is not added to the modification liquid in step S3.

[0097] Performance testing

[0098] The modified waste adhesive powder prepared in the embodiments and comparative examples of this application was applied to concrete to obtain test concrete. Specifically, the test concrete was prepared by the following method:

[0099] 230g of cement (P·O 42.5 ordinary Portland cement), 880g of crushed stone (continuous-sized crushed stone with a particle size of 5-10mm), and 400g of sand (with a particle size of 60-100 mesh) are mixed together, 20g of steel fiber is added, and the mixture is stirred. Then, 40g of modified waste rubber powder obtained in the examples or comparative examples of this application is added, and the mixture is stirred to obtain the initial mixture.

[0100] Mix 5g of polycarboxylate superplasticizer and 80g of water, then add the resulting initial mixture and stir to obtain concrete.

[0101] In addition, the modified waste adhesive powder in the above-mentioned test concrete was replaced with an equal amount of unmodified waste adhesive powder as the control test group, and the test concrete without the addition of modified waste adhesive powder was used as the blank test group.

[0102] The 28-day compressive strength and crack resistance of the above-mentioned test concrete, control test group, and blank test group concrete were tested respectively. The crack area refers to the crack area of ​​concrete in GB / T50082-2019 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The test results are shown in Table 1 below.

[0103] Table 1:

[0104]

[0105]

[0106] Continued from Table 1:

[0107]

[0108] Based on the test results in Table 1 above, the modified waste rubber powder prepared in this application exhibits excellent mechanical properties and crack resistance. Furthermore, the slump of the concrete prepared in the embodiments of this application is between 180-190 mm, and its fluidity meets the requirements. Referring to the test results of Examples 1 and 4-6, the pretreated waste rubber powder, after being mixed with dilute sulfuric acid and dried, was further treated with an impregnation solution to further improve the compressive strength and crack resistance of the concrete. This is because the impregnation solution treatment can further introduce carboxyl functional groups into the waste rubber powder, thereby forming a better cross-linking effect with the modified liquid, improving its compatibility with concrete, and also facilitating the formation of a macromolecular network structure, further improving strength and crack resistance. Referring to the test results of Example 7, when N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in the impregnation solution was replaced with an equal amount of ordinary silane coupling agent, it can be seen that its strength and crack resistance were reduced. This is because the introduction of the two amino groups in N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane can form chemical bonds with carboxylated nano-silica and temperature-sensitive materials, thereby improving the interfacial bonding force and improving the strength and crack resistance. Combining the test results of Example 8, when maleic anhydride was not added to the impregnation solution raw material in Example 8, the introduction of carboxyl functional groups on the surface of waste rubber powder was reduced, and the final strength and crack resistance were reduced.

[0109] Combining the test results of Example 1 with the blank group and the control group, it can be seen that when waste adhesive powder is added to concrete, although the strength is reduced compared to the blank group without waste adhesive powder, its crack resistance is significantly improved. It is evident that the addition of waste adhesive powder helps to improve crack resistance, but the strength loss is significant. In Example 1, the addition of modified waste adhesive powder not only helps to improve its strength but also has better crack resistance. Referring to the test results of Comparative Example 1, when the modified waste adhesive powder is not treated in the modification liquid but only treated with acid and alkali, although its strength is improved compared to the control group, it is still much weaker than that of Example 1. Combining the test results of Comparative Example 2, when PAMAM is not added to the modification liquid, there is a lack of connection bridging between the modified waste adhesive powder, the temperature-sensitive material, and the carboxylated nano-silica, and its strength and crack resistance are significantly reduced. Combined with the test results of Comparative Example 3, when hydroxypropyl β-cyclodextrin in the modified liquid was replaced with polyvinyl alcohol, its strength was lower than that in Example 1. Hydroxypropyl β-cyclodextrin coats the lipophilic portion, thereby improving its compatibility with the concrete system and thus increasing its strength. In Comparative Example 4, when genipin was not added, its strength and crack resistance were also significantly reduced. Genipin acts as a crosslinking agent. Combined with the test results of Comparative Example 6, when temperature-sensitive material was not added, its crack resistance was significantly reduced. Referring to Comparative Example 5, when waste rubber powder was modified using a silane coupling agent, although its strength was improved compared to the control group, it was still low.

[0110] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing modified waste rubber powder with temperature-sensitive properties, characterized in that, Includes the following steps: S1. Waste rubber powder pretreatment: After cleaning the waste rubber powder to remove impurities, it is soaked in sodium hydroxide solution, washed with water and dried to obtain pretreated waste rubber powder. S2. The pretreated waste rubber powder is mixed with dilute sulfuric acid solution and then dried to obtain the initially modified waste rubber powder. S3. After mixing and dispersing the pre-modified waste rubber powder with carboxylated nano-silica, the mixture is impregnated in the modification solution under pressure and then dried to obtain modified waste rubber powder. The modified liquid mainly includes PAMAM, polyisopropylacrylamide, genipin, polyvinyl alcohol, and hydroxypropyl β-cyclodextrin. In step S2, after the pretreated waste rubber powder is mixed with dilute sulfuric acid solution and dried, it is added to the impregnation solution for impregnation treatment and then dried. The impregnation solution mainly includes maleic anhydride, initiator and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. The modified liquid comprises the following raw materials in parts by weight: 15-22 parts PAMAM, 25-35 parts polyisopropylacrylamide, 2-4 parts genipin, 3-5 parts polyvinyl alcohol, 10-20 parts hydroxypropyl β-cyclodextrin, and 40-60 parts water; The impregnation solution comprises the following raw materials in parts by weight: 10-18 parts maleic anhydride, 3-5 parts initiator, 20-30 parts N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25-35 parts water, 10-20 parts ethanol, and 1-3 parts sodium dodecyl sulfate; The carboxylated nano-silica was prepared by the following method: Mixture A was prepared by mixing nano-silica, carboxymethyl cellulose and water in a mass ratio of 1:(0.1-0.2):(4-6); Mixture B was prepared by mixing succinic anhydride and ethanol at a mass ratio of 1:(2-3). Mixture A was heated to 50-60℃, and mixture B was added to mixture A under a nitrogen atmosphere. After reacting for 1-2 hours, the mixture was centrifuged, washed with water, and dried to obtain carboxylated nano-silica.

2. The method for preparing a modified waste rubber powder with temperature-sensitive properties according to claim 1, characterized in that: The initiator in the impregnation solution is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:(1.2-1.5).

3. The method for preparing a modified waste rubber powder with temperature-sensitive properties according to claim 1, characterized in that: In step S3, during the pressure impregnation treatment in the modified liquid, the impregnation temperature is 55-65℃ and the impregnation pressure is 2-3MPa.

4. The method for preparing a modified waste rubber powder with temperature-sensitive properties according to claim 1, characterized in that: In step S1, the mass concentration of the sodium hydroxide solution is 45-50%, and the amount of sodium hydroxide solution added is 4-6 times the mass of the waste adhesive powder. In step S2, the dilute sulfuric acid is selected as a sulfuric acid solution with a mass concentration of 60-65%, and the amount of dilute sulfuric acid solution added is 5-8 times the mass of the pretreated waste rubber powder. The mixing time of the pretreated waste rubber powder and the dilute sulfuric acid solution is 40-60 min, and the mixing temperature is 50-60℃. In step S3, the mass ratio of the initial modified waste rubber powder to the carboxylated nano silica is 1:(0.2-0.3), and the amount of modified liquid added is 8-10 times the mass of the initial modified waste rubber powder.

5. A modified waste adhesive powder with temperature-sensitive properties, characterized in that: It is prepared by the preparation method described in any one of claims 1-4.

6. The application of the modified waste adhesive powder with temperature-sensitive properties as described in claim 5 in concrete.

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