Modified waste rubber powder with temperature-sensitive characteristic as well as preparation method and application of modified waste rubber powder

Abstract

The invention relates to the field of environment-friendly materials, and particularly discloses modified waste rubber powder with a temperature-sensitive characteristic and a preparation method and application thereof.The preparation method of the modified waste rubber powder comprises the following steps that S1, waste rubber powder pretreatment is conducted, specifically, after waste rubber powder is cleaned to remove impurities, the waste rubber powder is soaked in a sodium hydroxide solution and then washed and dried, and pretreated waste rubber powder is prepared; s2, mixing the pretreated waste rubber powder with a dilute sulphuric acid solution, and drying to obtain primarily modified waste rubber powder; s3, mixing and dispersing the primarily modified waste rubber powder and carboxylated nano silicon dioxide, performing pressurized dipping treatment in a modification solution, and drying to obtain modified waste rubber powder; the modified liquid is mainly prepared from PAMAM (Polyamidoamine), polyisopropylacrylamide, genipin, polyvinyl alcohol and hydroxypropyl beta-cyclodextrin; the invention also discloses the modified waste rubber powder prepared by adopting the method and application of the prepared modified waste rubber powder in a concrete material. According to the invention, the waste rubber powder is modified so as to improve the strength and durability of concrete applied with the waste rubber powder.

Description

Technical Field

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

[0002] Waste rubber powder refers to the powdered rubber material obtained by crushing and processing waste rubber products. Waste rubber powder mainly comes from waste tires and other rubber products. These products are difficult to degrade under natural conditions, resulting in serious waste of resources. Applying waste rubber powder to concrete can not only effectively digest these wastes, but also achieve resource recycling, which is in line with the concept of sustainable development. Moreover, research has found that adding waste rubber powder to concrete can form a structural deformation center that absorbs strain energy, improve the impact resistance and seismic resistance of concrete, etc.; and waste rubber powder can reduce the volume shrinkage of concrete and avoid the generation of cracks. This is because the elastic modulus and tensile strength of waste rubber powder are very high, which can effectively prevent the shrinkage and deformation of concrete.

[0003] Although the application of waste rubber powder in concrete has achieved remarkable results, the compatibility of waste rubber powder with cement matrix is ​​poor. With the increase of waste rubber powder output, the strength of concrete is significantly reduced.

[0004] With the continuous development of the construction industry, the demand for high-performance concrete is increasing. Although traditional concrete can meet most engineering needs, its strength and durability still need to be improved. Therefore, it is necessary to modify the waste rubber powder and add it to further improve the strength and crack resistance of the concrete, thereby improving the durability of the concrete. Summary of the invention

[0005] In order to modify the waste rubber powder to improve the strength and durability of the concrete to which it is applied, the present application provides a modified waste rubber powder with temperature-sensitive properties, a preparation method thereof, and an application thereof.

[0006] In the first aspect, the present application provides a method for preparing a modified waste rubber powder having temperature-sensitive properties, using the following technical solution: A method for preparing modified waste rubber powder with temperature-sensitive properties comprises the following steps: S1. Pretreatment of waste rubber powder: washing the waste rubber powder to remove impurities, immersing it in a sodium hydroxide solution, washing it with water, and drying it to obtain pretreated waste rubber powder; S2, mixing the pretreated waste rubber powder with a dilute sulfuric acid solution and drying the mixture to obtain primary modified waste rubber powder; S3, mixing and dispersing the initially modified waste rubber powder and carboxylated nano-silicon dioxide, and then immersing them in a modified liquid under pressure and drying them to obtain modified waste rubber powder; Among them, the modified liquid mainly includes PAMAM, polyisopropylacrylamide, genipin and polyvinyl alcohol and hydroxypropyl β-cyclodextrin.

[0007] By adopting the above technical scheme, in the present application, the waste rubber powder is first soaked in a sodium hydroxide solution to remove the zinc stearate on the surface of the waste rubber powder, and then the pretreated waste rubber powder is immersed in a dilute sulfuric acid solution to introduce oxygen-containing functional groups such as hydroxyl or carboxyl groups on the surface of the waste rubber powder, and then the waste rubber powder is mixed with carboxylated nano-silicon dioxide and then immersed in a modified liquid under pressure. The PAMAM in the modified liquid is a water-soluble polyamide-amine dendrimer macromolecule containing a large number of amino functional groups, which form a carbonyl group under acidic conditions with the oxygen-containing functional groups such as carboxyl groups introduced into the waste rubber powder. Amide bond. At the same time, the amino group in PAMAM can also form a chemical bond with the carboxyl functional group in carboxylated nano-silica. The interface bonding between carboxylated nano-silica and waste rubber powder is improved through PAMAM, and the carboxylated nano-silica material is introduced into the waste rubber powder. The compatibility between the waste rubber powder and the concrete matrix is ​​improved through the filling effect and interface effect of the nano-material. Nano-silica can also react with calcium hydroxide in concrete to generate hydrated calcium silicate gel, which further enhances the interface bonding force and improves the strength of the concrete. In addition, in the present application, polyisopropylacrylamide is used as a temperature-sensitive material. When the temperature rises, polyisopropylacrylamide absorbs moisture, expands its volume, and fills the tiny cracks in the concrete; when the temperature drops, polyisopropylacrylamide releases moisture and shrinks its volume. This property enables the waste rubber powder to adjust the stress state inside the concrete when the temperature changes, thereby reducing the generation of cracks, thereby improving the durability of the concrete. The addition of genipin can achieve cross-linking of polyisopropylacrylamide and PAMAM, and can also achieve cross-linking of polyisopropylacrylamide with PAMAM and carboxylated nanodioxide. The cross-linking between the amide bonds formed by silicon and the cross-linking between the amide bonds formed by PAMAM and the carboxyl groups of the waste rubber powder eventually form a macromolecular structure, and its surface contains a large number of amino groups, which improves its compatibility with the concrete matrix. The bonding effect of polyvinyl alcohol improves the combination of waste rubber powder and carboxylated nano-silica, which plays a better reinforcing role. The addition of hydroxypropyl β-cyclodextrin, using its lipophilic cavity structure and hydrophilic shell structure, realizes the coating of the lipophilic part of the surface of the modified waste rubber powder, improves the compatibility between the modified waste rubber powder and the concrete matrix, and further plays a reinforcing role.

[0008] Optionally, after the pretreated waste rubber powder is mixed and dried with the dilute sulfuric acid solution in step S2, it is also added to an impregnation solution for impregnation treatment and drying, and the impregnation solution mainly includes maleic anhydride, an initiator and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0009] By adopting the above technical scheme, the pre-treated waste rubber powder in the present application is immersed in a dilute sulfuric acid solution and dried, and then treated in the immersion solution. Under the action of the initiator, maleic anhydride and the waste rubber powder undergo a grafting reaction to introduce a carboxyl functional group on the waste rubber powder, so that it can form a crosslink with PAMAM and polyisopropylacrylamide in the modifying solution. N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is used as a silane coupling agent, which contains a silane group and two amino groups. The silane group is hydrolyzed to form a silanol to form a coupling effect with the waste rubber powder and introduce an amino group, which can form a chemical bond with the carboxylated nano-silica, and it can also form a crosslinking effect with the modifier in the modifying solution. Finally, the waste rubber powder in the present application is not only introduced with a thermosensitive The present invention relates to a novel polymer material polyisopropyl acrylamide, which is also loaded with nano-silica. Nano-silica can fill the gap between the waste rubber powder and the concrete, enhance the interfacial bonding force between the waste rubber powder and the concrete, thereby improving the compatibility between the waste rubber powder and the concrete matrix and playing a reinforcing role. Moreover, the macromolecular network structure formed between the waste rubber powder, the waste rubber powder and the modified liquid further solves the problem of strength loss due to the addition of waste rubber powder and improves the strength. Moreover, since the PAMAM macromolecular polymer has a certain elastic modulus, it can play a certain volume buffering role for the contraction or expansion of polyisopropyl acrylamide PNIPAN due to temperature changes, further improving its self-curing performance and improving the durability of concrete.

[0010] Optionally, the modified liquid includes the following raw materials in parts by weight: 15-22 parts of PAMAM, 25-35 parts of polyisopropylacrylamide, 2-4 parts of genipin and 3-5 parts of polyvinyl alcohol, 10-20 parts of hydroxypropyl beta-cyclodextrin and 40-60 parts of water.

[0011] Optionally, the impregnation solution includes the following raw materials in parts by weight: 10-18 parts of maleic anhydride, 3-5 parts of initiator and 20-30 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25-35 parts of water and 10-20 parts of ethanol and 1-3 parts of sodium dodecyl sulfate.

[0012] Optionally, 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).

[0013] By adopting the above technical solution and controlling the above conditions, the modification effect of waste rubber powder is ultimately better, and the compatibility with concrete and the comprehensive performance of enhancement and durability are better.

[0014] Optionally, in step S3, during the pressurized immersion treatment in the modifying liquid, the immersion temperature is 55-65° C. and the immersion pressure is 2-3 MPa.

[0015] By adopting the above technical solution, using the above impregnation temperature and impregnation pressure, it is more conducive to the cross-linking modification of the primary modified waste rubber powder by the active substances in the modifying liquid, thereby improving its comprehensive performance.

[0016] Optionally, the carboxylated nano-silica is prepared by the following method: Mix nano-silicon dioxide, carboxymethyl cellulose and water in a mass ratio of 1:(0.1-0.2):(4-6) to prepare a mixture A; Succinic anhydride and ethanol are mixed in a mass ratio of 1:(2-3) to prepare a mixture B; Mixture A is heated to 50-60° C., 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, wherein the added mass ratio of nano-silica to succinic anhydride is 1:(0.4-0.6).

[0017] By adopting the above technical scheme, succinic anhydride is used as a carboxylation modification agent in the present application, nano-silica is first dispersed in an aqueous solvent, and then succinic anhydride is dissolved in ethanol and then added to the dispersion of nano-silica. A large number of hydroxyl groups exist on the surface of nano-silica. Succinic anhydride is ring-opened in heating and aqueous solvent to generate linear molecules with two carboxyl groups, which react with the hydroxyl groups on the nano-silica, thereby introducing carboxyl functional groups into the surface of nano-silica, thereby realizing the carboxylation modification of nano-silica, introducing carboxyl groups into the surface of nano-silica, thereby reacting with the main components in the modification liquid and the soaking liquid to realize the modification of waste rubber powder.

[0018] Optionally, the mass concentration of the sodium hydroxide solution in step S1 is 45-50%, and the amount of sodium hydroxide solution added is 4-6 times the mass of the waste rubber powder; In step S2, the dilute sulfuric acid is selected from a sulfuric acid solution with a mass concentration of 60-65%, and the amount of the dilute sulfuric acid solution added is 5-8 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 40-60 minutes, and the mixing temperature is 50-60°C; in step S3, the added mass ratio of the initial modified waste rubber powder to the carboxylated nano-silicon dioxide is 1: (0.2-0.3), and the amount of the modified liquid added is 8-10 times the mass of the initial modified waste rubber powder.

[0019] In a second aspect, the present application provides a modified waste rubber powder having temperature-sensitive properties, using the following technical solution: a modified waste rubber powder having temperature-sensitive properties is prepared by the preparation method.

[0020] By adopting the above technical scheme, the modified waste rubber powder is modified by the method in the present application. On the one hand, the thermosensitive polymer polyisopropylacrylamide PNIPAM is introduced on the surface of the waste rubber powder and introduced on the waste rubber powder particles, so that the waste rubber powder has a thermosensitive property, and changes its ability to absorb or release water under specific temperature conditions, thereby realizing the self-regulating supply of internal water so that the waste rubber powder can adjust the stress state inside the concrete when the temperature changes, thereby reducing the occurrence of cracks, thereby improving the durability of the concrete. On the other hand, the waste rubber powder and carboxylated nano-silica composite in the present application solves the problem of reduced strength of concrete due to the addition of waste rubber powder, and improves the interfacial bonding force between the two and the compatibility between the modified waste rubber powder and the concrete matrix through the addition of the modifying liquid, thereby playing a reinforcing role.

[0021] In a third aspect, the present application provides an application of modified waste rubber powder having temperature-sensitive properties, using the following technical solution: Application of modified waste rubber powder with temperature-sensitive properties in concrete.

[0022] By adopting the above technical solution, when the modified waste rubber powder in the present application is used in concrete, not only its durability is significantly improved, but also its strength and mechanical properties are excellent.

[0023] In summary, this application has the following beneficial effects: The modified waste rubber powder is modified by the method in the present application. On the one hand, a temperature-sensitive polymer polyisopropylacrylamide (PNIPAM) is introduced on the surface of the waste rubber powder and introduced on the waste rubber powder particles, so that the waste rubber powder has temperature-sensitive properties and changes its ability to absorb or release water under specific temperature conditions, thereby realizing self-regulating supply of internal water so that the waste rubber powder can adjust the stress state inside the concrete when the temperature changes, thereby reducing the occurrence of cracks and improving the durability of the concrete. On the other hand, the waste rubber powder and carboxylated nano-silica composite in the present application solves the problem of reduced strength of concrete due to the addition of waste rubber powder, and improves the interfacial bonding force between the two and the compatibility between the modified waste rubber powder and the concrete matrix through the addition of the modifying liquid, thereby playing a reinforcing role. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0025] Example 1 A method for preparing modified waste rubber powder with temperature-sensitive properties comprises the following steps: S1. Pretreatment of waste rubber powder: After cleaning the waste rubber powder to remove impurities, immerse it in a sodium hydroxide solution with a mass concentration of 48%, wash it with water and dry it to obtain pretreated waste rubber powder, wherein the amount of sodium hydroxide solution added is 5 times the mass of the waste rubber powder; S2, mixing the pretreated waste rubber powder with a dilute sulfuric acid solution with a mass concentration of 65% and drying the mixture to obtain the primary modified waste rubber powder, wherein the amount of the 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 minutes, and the mixing temperature is 55°C; S3. The initially modified waste rubber powder and carboxylated nano-silicon dioxide are mixed and dispersed in a mass ratio of 1:0.25, and then the mixture is immersed in a modifying liquid under pressure and dried. The amount of the modifying liquid added is 9 times the mass of the initially modified waste rubber powder, and the immersion temperature is 60°C, the immersion pressure is 2.5 MPa, and the immersion time is 1 hour to obtain the modified waste rubber powder.

[0026] The modified liquid is prepared by mixing 20g PAMAM, 30g polyisopropylacrylamide, 3g genipin, 4g polyvinyl alcohol, 15g hydroxypropyl β-cyclodextrin and 50g water; Carboxylated nano-silica is prepared by the following method: Nano-silicon dioxide, carboxymethyl cellulose and water were mixed in a mass ratio of 1:0.1:5 to prepare a mixture A; Succinic anhydride and ethanol are mixed in a mass ratio of 1:2.5 to prepare a mixture B; The mixture A was heated to 55° C., and the mixture B was added to the mixture A under a nitrogen atmosphere. After reacting for 1.5 hours, the mixture was centrifuged, washed with water, and dried to obtain carboxylated nano-silica.

[0027] Example 2 A method for preparing modified waste rubber powder with temperature-sensitive properties comprises the following steps: S1. Pretreatment of waste rubber powder: After cleaning the waste rubber powder to remove impurities, immerse it in a sodium hydroxide solution with a mass concentration of 45%, wash it with water and dry it to obtain pretreated waste rubber powder, wherein the amount of sodium hydroxide solution added is 4 times the mass of the waste rubber powder; S2, mixing the pretreated waste rubber powder with a dilute sulfuric acid solution with a mass concentration of 60% and drying it to obtain the primary modified waste rubber powder, wherein the amount of the 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 minutes, and the mixing temperature is 60°C; S3. The initially modified waste rubber powder and carboxylated nano-silicon dioxide are mixed and dispersed in a mass ratio of 1:0.2, and then the mixture is immersed in a modifying liquid under pressure and dried. The amount of the modifying liquid added is 8 times the mass of the initially modified waste rubber powder, and the immersion temperature is 55°C, the immersion pressure is 2MPa, and the immersion time is 2h to obtain the modified waste rubber powder.

[0028] The modified liquid is prepared by mixing 15g PAMAM, 25g polyisopropylacrylamide, 2g genipin, 3g polyvinyl alcohol, 10g hydroxypropyl β-cyclodextrin and 40g water; Carboxylated nano-silica is prepared by the following method: Nano-silicon dioxide, carboxymethyl cellulose and water were mixed in a mass ratio of 1:0.1:4 to prepare a mixture A; Succinic anhydride and ethanol are mixed in a mass ratio of 1:2 to prepare a mixture B; The mixture A was heated to 50° C., and the mixture B was added to the 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.

[0029] Example 3 A method for preparing modified waste rubber powder with temperature-sensitive properties comprises the following steps: S1. Pretreatment of waste rubber powder: After cleaning the waste rubber powder to remove impurities, immerse it in a sodium hydroxide solution with a mass concentration of 50%, wash it with water and dry it to obtain pretreated waste rubber powder, wherein the amount of sodium hydroxide solution added is 6 times the mass of the waste rubber powder; S2, mixing the pretreated waste rubber powder with a dilute sulfuric acid solution with a mass concentration of 65% and drying the mixture to obtain the primary modified waste rubber powder, wherein the amount of the 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 minutes, and the mixing temperature is 50°C; S3. The initially modified waste rubber powder and carboxylated nano-silicon dioxide are mixed and dispersed in a mass ratio of 1:0.3, and then the mixture is immersed in a modifying liquid under pressure and dried. The amount of the modifying liquid added is 10 times the mass of the initially modified waste rubber powder, and the immersion temperature is 65°C, the immersion pressure is 3 MPa, and the immersion time is 40 min to obtain the modified waste rubber powder.

[0030] The modified liquid is prepared by mixing 22g PAMAM, 35g polyisopropylacrylamide, 4g genipin, 5g polyvinyl alcohol, 20g hydroxypropyl β-cyclodextrin and 60g water; Carboxylated nano-silica is prepared by the following method: Nano-silicon dioxide, carboxymethyl cellulose and water were mixed in a mass ratio of 1:0.2:6 to prepare a mixture A; Succinic anhydride and ethanol are mixed in a mass ratio of 1:3 to prepare a mixture B; The mixture A was heated to 60° C., and the mixture B was added to the 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.

[0031] Example 4 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 S2, after the pretreated waste rubber powder is mixed and dried with a dilute sulfuric acid solution, it is further added to an impregnation liquid for impregnation treatment for 40 minutes, the impregnation temperature is 55° C., and then dried to obtain an initial modified waste rubber powder, wherein the amount of the impregnation liquid added is 5 times the mass of the pretreated waste rubber powder, and the impregnation liquid is obtained by mixing the following raw materials: 15g maleic anhydride, 4g initiator and 25g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 30g water and 15g ethanol and 2g sodium dodecyl sulfate.

[0032] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.3.

[0033] Example 5 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that, in step S2, after the pretreated waste rubber powder is mixed and dried with a dilute sulfuric acid solution, it is further added to an impregnation liquid for impregnation treatment for 30 minutes, the impregnation temperature is 60° C., and then dried to obtain the primary modified waste rubber powder, wherein the amount of the impregnation liquid added is 4 times the mass of the pretreated waste rubber powder, and the impregnation liquid is obtained by mixing the following raw materials: 10g maleic anhydride, 3g initiator and 20g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25g water and 10g ethanol and 1g sodium dodecyl sulfate.

[0034] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.2.

[0035] Example 6 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 S2, after the pretreated waste rubber powder is mixed and dried with a dilute sulfuric acid solution, it is further added to an impregnation liquid for impregnation treatment for 50 minutes, the impregnation temperature is 50° C., and then dried to obtain an initial modified waste rubber powder, wherein the amount of the impregnation liquid added is 6 times the mass of the pretreated waste rubber powder, and the impregnation liquid is obtained by mixing the following raw materials: 18g maleic anhydride, 5g initiator and 30g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 35g water and 20g ethanol and 3g sodium dodecyl sulfate.

[0036] The initiator is a mixture of ammonium persulfate and benzoyl peroxide in a mass ratio of 1:1.5.

[0037] Example 7 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 4, except that an equal amount of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in the impregnation solution is replaced by KH-550.

[0038] Example 8 A method for preparing 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 raw material of the impregnation solution.

[0039] Comparative Example 1 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that step S3 is not performed.

[0040] Comparative Example 2 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that PAMAM is not added to the modified liquid in step S3.

[0041] Comparative Example 3 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that in step S3, an equal amount of hydroxypropyl β-cyclodextrin in the modifying liquid is replaced by polyvinyl alcohol.

[0042] Comparative Example 4 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that no genipin is added to the modified liquid in step S3.

[0043] Comparative Example 5 A method for preparing modified waste rubber powder with temperature-sensitive properties is carried out according to the method in Example 1, except that the modifying liquid in step S3 is a mixture of KH-550 silane coupling agent and water in a mass ratio of 1:4.

[0044] Comparative Example 6 A method for preparing 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 modified liquid in step S3.

[0045] Performance Testing The modified waste rubber powder prepared in the examples and comparative examples of the present application is applied to concrete to obtain test concrete. Specifically, the test concrete is prepared by the following method: 230 g of cement (PO 42.5 ordinary Portland cement), 880 g of crushed stone (continuous grade crushed stone with a particle size of 5-10 mm), and 400 g of sand (with a particle size of 60-100 mesh) are mixed, 20 g of steel fiber is added, and the mixture is stirred. Then, 40 g of the modified waste rubber powder obtained in the examples or comparative examples of the present application is added, and the mixture is stirred to obtain a primary mixture. 5 g of polycarboxylate water-reducing agent and 80 g of water were mixed and stirred, and then added into the prepared initial mixture and stirred to prepare concrete.

[0046] In addition, the modified waste rubber powder in the above test concrete was replaced with an equal amount of unmodified waste rubber powder as a control test group, and no modified waste rubber powder was added to the test concrete as a blank test group.

[0047] The 28d compressive strength and crack resistance of the above-mentioned test concrete, the control test group and the blank test group concrete were tested respectively. The crack resistance area refers to the cracking area of ​​concrete in GB / T50082-2019 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete". The test results are shown in Table 1 below.

[0048] Table 1: Table 1 continued: Combined with the test results of Table 1 above, the modified waste rubber powder prepared in the present application has excellent mechanical properties and crack resistance, and the slump of the concrete prepared in the examples of the present application is between 180-190 mm, and the fluidity meets the requirements. Referring to the test results of Example 1 and Examples 4-6, the pre-treated waste rubber powder is mixed with dilute sulfuric acid and dried, and then treated with an impregnation liquid to further improve the compressive strength and crack resistance of the concrete. This is because the impregnation liquid treatment can further introduce carboxyl functional groups into the waste rubber powder, thereby forming a better cross-linking effect with the modified liquid, improving the compatibility with the concrete, and is also conducive to forming a macromolecular network structure, further improving the strength and crack resistance. Referring to the test results of Example 7, when the N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in the impregnation liquid is replaced with an equal amount of ordinary silane coupling agent, it can be seen that its strength and crack resistance are reduced. This is because the introduction of 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, improving the strength and crack resistance. Combined with the test results of Example 8, when maleic anhydride is not added to the impregnation liquid raw material in Example 8, the introduction of carboxyl functional groups on the surface of the waste rubber powder is reduced, and the final strength and crack resistance are reduced.

[0049] Combining the test results of Example 1 with the blank group and the control group, it can be seen that when waste rubber powder is added to the concrete, the strength is reduced compared to the blank group without waste rubber powder, but its crack resistance is significantly improved. It can be seen that the addition of waste rubber powder helps to improve the crack resistance but its strength loss is large. In Example 1, the modified waste rubber powder not only helps to improve its strength but also has better crack resistance. Referring to the test results of Comparative Example 1, the modified waste rubber powder is not treated in the modifying liquid, but only treated with acid and alkali. Although its strength is improved compared with the control group, it is still far weaker than that of Example 1. Combined with the test results of Comparative Example 2, when PAMAM is not added to the modifying liquid, there is a lack of connection and bridging between the modified waste rubber 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 is replaced with polyvinyl alcohol, its strength is reduced compared with that in Example 1. Hydroxypropyl β-cyclodextrin coats the lipophilic part, thereby improving its compatibility with the concrete system, thereby improving its strength. When no genipin is added in Comparative Example 4, its strength and crack resistance are also significantly reduced. Genipin acts as a cross-linking agent. Combined with the test results of Comparative Example 6, when no temperature-sensitive material is added in Comparative Example 6, its crack resistance is significantly reduced. Referring to Comparative Example 5, when the waste rubber powder is modified with a silane coupling agent, although its strength is improved compared with the control group, it is still relatively low.

[0050] 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 modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing modified waste rubber powder with temperature-sensitive properties, characterized in that: The following steps are involved: S1. Pretreatment of waste rubber powder: washing the waste rubber powder to remove impurities, immersing it in a sodium hydroxide solution, washing it with water, and drying it to obtain pretreated waste rubber powder; S2, mixing the pretreated waste rubber powder with a dilute sulfuric acid solution and drying the mixture to obtain primary modified waste rubber powder; S3, mixing and dispersing the initially modified waste rubber powder and carboxylated nano-silicon dioxide, and then immersing them in a modified liquid under pressure and drying them to obtain modified waste rubber powder; Among them, the modified liquid mainly includes PAMAM, polyisopropylacrylamide, genipin and polyvinyl alcohol and hydroxypropyl β-cyclodextrin.

2. The method for preparing a modified waste rubber powder with temperature-sensitive properties according to claim 1, characterized in that: In step S2, after the pretreated waste rubber powder is mixed with the dilute sulfuric acid solution and dried, it is also added to the impregnation liquid for impregnation treatment and drying. The impregnation liquid mainly includes maleic anhydride, initiator and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

3. The method for preparing a modified scrap rubber powder having temperature-sensitive properties according to claim 1, characterized in that: The modified liquid includes the following raw materials in parts by weight: 15-22 parts of PAMAM, 25-35 parts of polyisopropylacrylamide, 2-4 parts of genipin and 3-5 parts of polyvinyl alcohol, 10-20 parts of hydroxypropyl beta-cyclodextrin and 40-60 parts of water.

4. The method for preparing a modified waste rubber powder having temperature-sensitive properties according to claim 2, characterized in that: The impregnation solution includes the following raw materials in parts by weight: 10-18 parts of maleic anhydride, 3-5 parts of initiator and 20-30 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 25-35 parts of water and 10-20 parts of ethanol and 1-3 parts of sodium dodecyl sulfate.

5. The method for preparing a modified waste rubber powder with temperature-sensitive properties according to claim 4, 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).

6. The method for preparing a modified scrap rubber powder having temperature-sensitive properties according to claim 1, characterized in that: In step S3, during the pressurized immersion treatment in the modifying liquid, the immersion temperature is 55-65° C. and the immersion pressure is 2-3 MPa.

7. The method for preparing a modified scrap rubber powder having temperature-sensitive properties according to claim 1, characterized in that: The carboxylated nano-silica is prepared by the following method: Nano-silicon dioxide, carboxymethyl cellulose and water are mixed in a mass ratio of 1: (0.1-0.2): (4-6) to prepare a mixture A; Succinic anhydride and ethanol are mixed in a mass ratio of 1:(2-3) to prepare a mixture B; The mixture A is heated to 50-60° C., and the mixture B is added to the 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.

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

9. A modified waste rubber powder with temperature-sensitive properties, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the modified waste rubber powder with temperature-sensitive properties as claimed in claim 9 in concrete.

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