Humidity-responsive porous cement-based sound absorption material and preparation method thereof

Abstract

The invention discloses a humidity-responsive porous cement-based sound absorption material and a preparation method thereof, and belongs to the technical field of porous sound absorption materials. The humidity-responsive porous cement-based sound absorption material is prepared from the following components in parts by weight: 100 parts of cement, 50 parts of water, 16 to 22 parts of amino acid modified starch-based copolymer, 3 parts of hydrogen peroxide, 1.2 to 6 parts of ferrite and 0.2 part of nano aluminum oxide. The hydrogen peroxide, the ferrous salt, the amino acid modified starch-based copolymer and the nanometer aluminum oxide are added into cement paste, the prepared material is not of a static porous structure any more, but is a system with humidity response capacity, in a high-humidity environment, a high-molecular polymer in the porous structure can rapidly absorb water and swell, and the humidity response capacity is improved. Therefore, a pore channel is automatically and reversibly blocked, a dynamic waterproof barrier is formed, water invasion is effectively prevented, and freeze-thaw damage is avoided; and when the environment humidity is reduced, the polymer in the pore shrinks due to water loss, and the pore channel is opened again to recover the excellent sound absorption performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of porous sound-absorbing materials, and particularly relates to a humidity-responsive porous cement-based sound-absorbing material and a preparation method thereof. BACKGROUND

[0002] Cement-based sound-absorbing materials are widely used in noise control engineering such as traffic sound barriers, building outer walls, and tunnel inner walls due to their low cost. In order to achieve high sound-absorbing performance and long-term use stability, existing cement-based sound-absorbing materials usually rely on physical or chemical foaming agents to form static pore structures, such as aluminum powder or hydrogen peroxide.

[0003] There is also a Chinese patent CN108640574A which discloses a preparation method of a compression-resistant sound-absorbing brick. According to the weight parts, 70-80 parts of Portland cement, 15-20 parts of a modified additive, 8-12 parts of a treatment agent, 2-8 parts of reinforcing fibers, 1-5 parts of sodium chloride, 1-5 parts of calcium bicarbonate, and 50-60 parts of water are sequentially weighed. The modified additive in the technical solution contains silicon dioxide with a pore structure, which can effectively improve the porosity in the product after being added to the product, thereby improving the sound absorption efficiency and sound insulation performance of the product. The technical solution prepares a material with high open porosity, thereby obtaining excellent sound absorption performance.

[0004] There is also CN119774957A which discloses a foam cement-based sound-absorbing material with adjustable pore structure and a preparation method thereof. The raw materials include P.O42.5R Portland cement 1000-1300 parts, water 400-600 parts, composite foaming agent 20-100 parts, micropore structure adjusting agent 10-35 parts, composite pore-forming agent 5-30 parts, and accelerating agent 1-20 parts. The high open porosity static porous network is constructed by the combined action of hydrogen peroxide and physical foaming agent, combined with complex processes such as freeze-drying.

[0005] However, the above-mentioned prior art has the defect that the pore structure is static and permanently open, which is equivalent to opening a highway straight into the material interior for external moisture. In a high-humidity or rain environment, water vapor and liquid water will pass through these open pores into the core of the material without any hindrance, not only causing the sound-absorbing function to be completely lost due to the pores being filled with water, but also causing freeze-thaw cycles in winter, which will internally collapse the material structure and severely damage its durability.

[0006] There are also patents like Chinese patent CN101360778A, which discloses an organic foam plastic body with excellent heat resistance and durability. To improve durability, an inorganic coating is applied to the surface of the organic foam. This coating creates a large water contact angle when exposed to water, preventing water from penetrating the expandable plastic foam material and thus improving water resistance. While this achieves long-term use and water and moisture resistance, it can clog sound-absorbing pores, reducing the material's porosity and sound absorption performance, thus failing to effectively achieve its sound absorption function.

[0007] Currently, there are also attempts to introduce humidity-responsive functionality into porous materials by simply mixing traditional cement foaming technology with ordinary superabsorbent polymer (SAP). However, under the alkaline conditions of cement, existing technologies will undergo rapid alkaline hydrolysis in environments with a pH greater than 12, resulting in the breakage of polymer chains and the destruction of cross-linking networks. As a result, the humidity-responsive functionality is easily lost after a few months, degenerating into ordinary, non-moisture-resistant, high-porosity materials.

[0008] There is also a Chinese patent, CN109098104A, which discloses a sound barrier composed of a multi-cavity and porous sound-absorbing material combination. The sound barrier body is made of alkali-resistant glass fiber reinforced cement, which comprises the following components by weight: cement 40-60 parts, sand 40-55 parts, alkali-resistant glass fiber 2-4 parts, expanded perlite 10-20 parts, vinyl acetate-ethylene copolymer emulsion 0.3-3 parts, calcium stearate 1-3 parts, and water 30-100 parts. While the alkali-resistant glass fiber reinforced cement contains vinyl acetate-ethylene copolymer emulsion, its purpose is to improve the overall toughness and adhesion of the material. The polymer introduced in this prior art does not possess the ability to construct a dynamic humidity-responsive structure within the pores to achieve intelligent moisture-proofing, nor does it solve the stability problem of SAP in a strongly alkaline environment.

[0009] There is also a Chinese patent, CN117486560A, which discloses a cement-based penetrating crystalline waterproof material and its preparation method. The raw materials include water, quartz sand, organic additives, and the following substances in parts by weight: the organic additives include 0.6-1.5 parts of polyacrylamide or 0.5-1 parts of maleic anhydride; the cement includes aluminate cement and silicate cement; the mass of aluminate cement accounts for 30-50% of the total mass of cement, and the mass of silicate cement accounts for 50-70% of the total mass of cement; the mass ratio of quartz sand to the total mass of cement, dihydrate gypsum, and hydrated lime is 1:(0.4-0.6); the ferrous salt includes ferrous sulfate. The mixing includes the following steps: first mixing cement, dihydrate gypsum, hydrated lime, ferrous salt, organic additives, water-based epoxy resin, and water to obtain a cement-based mixture; and second mixing quartz sand with the cement-based mixture. The aforementioned existing technologies stabilize volume and suppress volume deformation by introducing ferrous salts to inhibit the conversion of hydration products AFm to AFt; and by adding organic additives such as polyacrylamide to improve density. However, the starting point and ultimate goal of this technical solution is to pursue ultimate density and waterproofing, and its technical path runs counter to the high porosity structure required for sound-absorbing materials.

[0010] To address the aforementioned issues, this application provides a humidity-responsive porous cement-based sound-absorbing material and its preparation method. Summary of the Invention

[0011] To address the deficiencies in the aforementioned technical solutions, the present invention aims to provide a humidity-responsive porous cement-based sound-absorbing material and its preparation method. This objective is achieved through the following technical solution: A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following components: 100 parts cement, 50 parts water, 16-22 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 1.2-6 parts ferrous salt, and 0.2 parts nano-alumina.

[0012] The amino acid in the amino acid-modified starch-based copolymer is any one of glutamic acid, lysine, or aspartic acid and glycine.

[0013] In one or more embodiments, the amino acid in the amino acid-modified starch-based copolymer is lysine.

[0014] The ferrous salt is any one of ferrous chloride, ferrous nitrate, ferrous carbonate, ferrous acetate, and ferrous sulfate.

[0015] In one or more embodiments, the ferrous salt is ferrous sulfate.

[0016] The cement is P.O42.5R ordinary Portland cement.

[0017] The nano-alumina is γ-phase nano-alumina powder; The nano-alumina has an average particle size of 20-50 nanometers and a specific surface area greater than 150 m². 2 / g.

[0018] Furthermore, the humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina; wherein the amino acid-modified starch-based copolymer is a lysine-modified starch-based copolymer.

[0019] The preparation method of the amino acid-modified starch-based copolymer includes: the preparation of starch-based copolymer and the preparation of amino acid-modified starch-based copolymer.

[0020] The preparation method of the starch-based copolymer is as follows: Weigh 100 parts by mass of starch and place it in a reaction vessel equipped with a stirrer, thermometer, and dropping funnel. Add 900 parts by mass of deionized water. Under continuous stirring, heat to 80-90°C and maintain the temperature for 1 hour to completely gelatinize the starch, forming a uniform, particle-free starch paste. Then, cool the system to 50-60°C for later use. Under nitrogen protection, add 0.3 parts by mass of Fenton's reagent to the starch paste and stir until completely dissolved. Then, slowly add a solution containing 3 parts by mass of 30% hydrogen peroxide, maintaining a stable temperature during the addition. Subsequently, slowly add 150 parts by mass of acrylic acid monomer through a dropping funnel. The dropping rate should be controlled so that the temperature fluctuation of the reaction system does not exceed ±2°C. After the addition is complete, continue to maintain the reaction at 50-60°C for 2-4 hours to ensure complete polymerization. After the reaction, the pH of the product system was adjusted to neutral with an alkaline solution. Subsequently, the resulting gel-like product was precipitated and broken down with excess ethanol or acetone to precipitate the solid polymer. The solid product was repeatedly washed several times with an ethanol / water mixture to thoroughly remove unreacted acrylic monomers, acrylic homopolymers, etc. Finally, the purified solid product was dried to constant weight in a vacuum oven at 60-80℃, pulverized, and sieved to obtain a white powdered starch-based copolymer.

[0021] In one or more embodiments, the starch is potato starch with a whiteness of not less than 90% and a Brabant peak viscosity of not less than 1200 BU.

[0022] Preparation method of amino acid-modified starch-based copolymer: Weigh 10 parts by weight of powdered starch-based copolymer and disperse it in 200 parts by weight of deionized water. Stir thoroughly at room temperature until swollen. Add 10 parts by weight of lysine to the dispersion and stir until dissolved. Then, slowly add sodium hydroxide solution dropwise to precisely adjust the pH of the reaction system to 11. Heat the reactor to 70°C and react at this temperature for 10 hours under nitrogen protection.

[0023] After the reaction was complete, the resulting reaction solution was transferred to a dialysis bag; dialysis was performed continuously for 72 hours using a large amount of deionized water as the dialysis fluid, with the dialysis fluid being replaced every 6-8 hours. This process is crucial for removing all unreacted glycine, small molecule salts, and other impurities, and is the core step in obtaining the high-purity target product. The purified product solution was then freeze-dried to obtain a loose, porous solid. This solid was ground into powder, which is the final product: the amino acid-modified starch-based copolymer.

[0024] A method for preparing a humidity-responsive porous cement-based sound-absorbing material includes the following steps: Step 1: Weigh the amino acid-modified starch-based copolymer and nano-alumina, add a small amount of water and perform ultrasonic dispersion treatment until a uniform suspension is formed; add hydrogen peroxide to the above suspension and stir evenly to obtain the active premix for use. Step 2: Prepare cement-based slurry. Weigh cement and place it in a mixer. Add water while mixing and mix at high speed to form a uniform cement paste. Add all the active premix prepared in Step 1 to the cement paste in Step 2 and mix thoroughly to form a foamed cement slurry. Step 3: Add ferrous salt and nano alumina to the above-mentioned cement foaming slurry, stir thoroughly, pour into a mold, let it stand to cure and then demold. Cur the demolded test block under the preset curing conditions until the specified age, thus obtaining a humidity-responsive porous cement-based sound-absorbing material.

[0025] The beneficial effects of this invention are as follows: 1. The technical solution of the present invention, by adding a specific amino acid-modified starch-based copolymer to a porous cement-based sound-absorbing material and supplementing it with the synergistic protection of nano-alumina, enables the polymer to exist stably for a long time in the alkaline environment formed by cement hydration, unlike ordinary superabsorbent polymer (SAP) which will fail due to alkaline hydrolysis after several months, thus ensuring that the porous cement-based sound-absorbing material prepared in this application has a longer service life. 2. This invention achieves in-situ integrated generation of foaming and pore-forming with a functional polymer network by adding hydrogen peroxide, ferrous salt, amino acid-modified starch-based copolymer, and nano-alumina to cement slurry. The resulting material is no longer a static porous structure, but a system with humidity responsiveness. In high humidity environments, the polymer inside the pore structure rapidly absorbs water and swells, thereby automatically and reversibly blocking the pore channels and forming a dynamic waterproof barrier to effectively prevent water intrusion and avoid freeze-thaw damage. When the ambient humidity decreases, the polymer inside the pores loses water and shrinks, reopening the pores and restoring its excellent sound absorption performance. Attached Figure Description

[0026] Figure 1 This is a SEM image of the humidity-responsive porous cement-based sound-absorbing material in Embodiment 3 of this application under closed conditions in high humidity; Figure 2 These are SEM images of the humidity-responsive porous cement-based sound-absorbing material in Embodiment 3 of this application under low humidity open conditions; Figure 3 These are high-magnification SEM images of embodiments of this application at a scale bar of 2μm; Figure 4 This is a low-magnification SEM image of an embodiment of this application with a scale bar of 10μm. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for explanation only and are not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] In the following examples, "parts" refers to parts by weight.

[0032] Example 1 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 16 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 1.2 parts ferrous salt, and 0.2 parts nano-alumina.

[0033] The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer.

[0034] The ferrous salt is specifically ferrous sulfate.

[0035] The cement is P.O42.5R ordinary Portland cement; The nano-alumina is γ-phase nano-alumina powder; The nano-alumina has an average particle size of 20-50 nanometers and a specific surface area greater than 150 m². 2 / g.

[0036] The preparation method of the amino acid-modified starch-based copolymer includes: the preparation of starch-based copolymer and the preparation of amino acid-modified starch-based copolymer.

[0037] The method for preparing the starch-based copolymer is as follows: Weigh 100 parts by weight of starch and place it in a reaction vessel equipped with a stirring device, thermometer and dropping funnel. Add 900 parts by weight of deionized water, heat to 80-90°C under continuous stirring, and keep warm for 1 hour to completely gelatinize the starch and form a uniform, particle-free starch paste. Then cool the reaction system to 50-60°C for later use. Then, under nitrogen protection, 0.3 parts by mass of Fenton's reagent was added to the starch paste and stirred until completely dissolved; then, a solution containing 3 parts by mass of 30% hydrogen peroxide was slowly added dropwise, while maintaining the temperature of the reaction system stable during the addition process. After the addition is complete, slowly add 150 parts by weight of acrylic monomer through a dropping funnel; control the dropping rate so that the temperature fluctuation of the reaction system does not exceed ±2℃; after all the addition is complete, continue to keep the reaction at 50-60℃ for 2-4 hours to ensure that the polymerization reaction is complete; after the reaction is completed, adjust the pH value of the reaction system to neutral with sodium hydroxide solution. Subsequently, excess ethanol or acetone is used to precipitate and break the gel, precipitating out the solid polymer; the solid product is then repeatedly washed several times with an ethanol / water mixture to thoroughly remove unreacted acrylic monomers, acrylic homopolymers, etc. Finally, the purified solid product was dried to constant weight in a vacuum oven at 60-80℃, pulverized, and sieved to obtain a white powdery starch-based copolymer.

[0038] The starch is potato starch, with a whiteness of not less than 90% and a Brabant peak viscosity of not less than 1200 BU. The Fenton reagent comprises H2O2 and FeSO4•7H2O, wherein the molar ratio of H2O2 to FeSO4•7H2O is 5:1.

[0039] The preparation method of the amino acid modified starch-based copolymer is as follows: 10 parts by mass of powdered starch-based copolymer are weighed and dispersed in 200 parts by mass of deionized water, and stirred and swollen at room temperature; 10 parts by mass of lysine are added to the above dispersion and stirred to dissolve it; then, sodium hydroxide solution is slowly added dropwise to precisely adjust the pH value of the reaction system to 11; alkaline conditions are beneficial to the subsequent chemical reaction.

[0040] The reaction vessel was heated to 70°C and reacted at a constant temperature for 10 hours under nitrogen protection. Under these conditions, the amino groups on the amino acid molecules reacted with the carboxyl groups on the side chains of the powdered starch-based copolymer to form amide bonds, thus successfully attaching the amino acid to the polymer side chains. After the reaction, the resulting reaction solution was transferred to a dialysis bag with a molecular weight cutoff of 7000 Da. Dialysis was performed continuously for 72 hours using a large amount of deionized water as the dialysis fluid, with the dialysis fluid being replaced every 6-8 hours. By utilizing the difference in molecular size, all unreacted glycine, small molecule salts, and other impurities were completely removed. Finally, the purified product solution was freeze-dried to obtain a loose and porous solid. This solid was then ground into powder to prepare the lysine-modified starch-based copolymer.

[0041] A method for preparing a humidity-responsive porous cement-based sound-absorbing material includes the following steps: Step 1: Weigh the amino acid-modified starch-based copolymer and nano-alumina, add a small amount of water and perform ultrasonic dispersion treatment until a uniform suspension is formed; add hydrogen peroxide to the above suspension and stir evenly to obtain the active premix for use.

[0042] Step 2: Prepare cement-based slurry. Weigh the cement and place it in a mixer. Add water while mixing and stir at high speed to form a uniform cement paste. Add all the active premix prepared in Step 1 to the cement paste in Step 2 and mix them thoroughly to form a foamed cement slurry.

[0043] Step 3: Add ferrous salt and nano alumina to the above-mentioned cement foaming slurry, stir thoroughly, pour into a mold, let it stand to cure and then demold. Cur the demolded test block under the preset curing conditions until the specified age, thus obtaining a humidity-responsive porous cement-based sound-absorbing material.

[0044] Example 2 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 22 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of the humidity-responsive porous cement-based sound-absorbing material in Example 2 are the same as those in Example 1.

[0045] Example 3 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Example 3 are the same as those in Example 1.

[0046] Example 4 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 5.5 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of the humidity-responsive porous cement-based sound-absorbing material in Example 4 are the same as those in Example 1.

[0047] Example 5 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 22 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 4.5 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Example 5 are the same as those in Example 1.

[0048] Example 6 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 18 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 2.5 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of the humidity-responsive porous cement-based sound-absorbing material in Example 6 are the same as those in Example 1.

[0049] Comparative Example 1 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a glutamic acid-modified starch-based copolymer; Specifically, the glutamic acid modified starch-based copolymer is prepared by replacing lysine with glutamic acid in the preparation method of amino acid modified starch-based copolymer. Otherwise, the preparation method is the same as in Example 1.

[0050] The ferrous salt is specifically ferrous sulfate; The preparation method of the humidity-responsive porous cement-based sound-absorbing material in Comparative Example 1 is the same as that in Example 3.

[0051] Comparative Example 2 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically an aspartic acid-modified starch-based copolymer. Specifically, the aspartic acid modified starch-based copolymer is prepared by replacing lysine with aspartic acid in the preparation method of amino acid modified starch-based copolymer. Otherwise, the preparation method is the same as in Example 1.

[0052] The ferrous salt is specifically ferrous sulfate; The preparation method of the humidity-responsive porous cement-based sound-absorbing material in Comparative Example 1 is the same as that in Example 3.

[0053] Comparative Example 3 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a glycine-modified starch-based copolymer; Specifically, the glycine-modified starch-based copolymer is prepared by replacing lysine with glycine in the preparation method of amino acid-modified starch-based copolymer in Example 1. Otherwise, the preparation method is the same as in Example 1.

[0054] The ferrous salt is specifically ferrous sulfate; The preparation method of the humidity-responsive porous cement-based sound-absorbing material in Comparative Example 1 is the same as that in Example 3.

[0055] Comparative Example 4 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 35 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The difference between Comparative Example 4 and Example 3 is that the amount of amino acid-modified starch-based copolymer added was increased to 35 parts; otherwise, the preparation method of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 4 are the same as those in Example 3.

[0056] Comparative Example 5 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 8 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The difference between Comparative Example 5 and Example 3 is that the amount of amino acid-modified starch-based copolymer added was reduced to 8 parts; otherwise, the preparation method of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 5 are the same as those in Example 3.

[0057] Comparative Example 6 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 8 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous chloride; The difference between Comparative Example 6 and Example 3 is that ferrous sulfate was replaced with ferrous chloride. The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 6 are the same as those in Example 3.

[0058] Comparative Example 7 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 8 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous nitrate; The difference between Comparative Example 7 and Example 3 is that ferrous sulfate was replaced with ferrous nitrate. The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 7 are the same as those in Example 3.

[0059] Comparative Example 8 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 8 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous carbonate; The difference between Comparative Example 8 and Example 3 is that ferrous sulfate was replaced with ferrous carbonate. The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 8 are the same as those in Example 3.

[0060] Comparative Example 9 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 8 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous acetate; The difference between Comparative Example 9 and Example 3 is that ferrous sulfate was replaced with ferrous acetate. The preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 9 are the same as those in Example 3.

[0061] Comparative Example 10 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 0.4 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The difference between Comparative Example 10 and Example 3 is that the amount of ferrous salt was reduced to 0.4 parts. Otherwise, the preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 10 are the same as those in Example 3.

[0062] Comparative Example 11 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, 10 parts ferrous salt, and 0.2 parts nano-alumina. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The difference between Comparative Example 11 and Example 3 is that the amount of ferrous salt was increased to 10 parts. Otherwise, the preparation methods of the amino acid-modified starch-based copolymer and the preparation method of a humidity-responsive porous cement-based sound-absorbing material in Comparative Example 11 are the same as those in Example 3.

[0063] Comparative Example 12 A humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts amino acid-modified starch-based copolymer, 3 parts hydrogen peroxide, and 3.6 parts ferrous salt. The amino acid-modified starch-based copolymer is specifically a lysine-modified starch-based copolymer; The ferrous salt is specifically ferrous sulfate; The difference between Comparative Example 12 and Example 3 is that the addition of nano-alumina is omitted. Otherwise, the preparation methods of amino acid-modified starch-based copolymer and humidity-responsive porous cement-based sound-absorbing material in Comparative Example 12 are the same as those in Example 3.

[0064] Test case All samples were prepared into block specimens of 100mm×50mm×50mm and were cured for 28 days under standard curing conditions (temperature 20±2℃, relative humidity ≥95%) before performance testing.

[0065] Determination of average sound absorption coefficient and initial noise reduction coefficient: Refer to GB / T 18696.1 "Measurement of sound absorption and impedance in acoustic impedance tubes - Part 1: Standing wave ratio method" to complete the initial performance determination of the test block and the subsequent performance determination after freeze-thaw. Determination of water absorption rate of test blocks: The water absorption rate of the test blocks was tested in accordance with the water absorption rate test method in GB / T 50081 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Porosity determination of the test block: The porosity of the test block was determined using the saturated surface-dry method. The dried test block was weighed (m0); the test block was boiled in water for 5 hours, and then naturally cooled in water for 24 hours to ensure that the internal pores were completely saturated; the test block was removed, and the surface was wiped dry with a towel until it reached a saturated surface-dry state, and its mass (m1) was measured; the suspended mass (m2) of the test block in water was then measured; the porosity was calculated as (m1-m0) / (m1-m2)*100%. Determination of average sound absorption coefficient and noise reduction coefficient after freeze-thaw: The test block was placed in a freeze-thaw test chamber and subjected to 20 freeze-thaw cycles; the center temperature of each cycle alternated between (-18±2)℃ and (5±2)℃, and the humidity inside the freeze-thaw test chamber was set to 100%; after completing 20 cycles, the test block was removed and completely dried, and the average sound absorption coefficient and initial noise reduction coefficient were measured again, so that the average sound absorption coefficient and noise reduction coefficient after freeze-thaw can be obtained.

[0066] The test results of test blocks 1-6 in Examples are shown in Table 1: Table 1 As can be seen from the test results in Table 1, within the formulation range defined by this invention, by combining specific types of lysine-modified starch-based copolymers with specific types of ferrous sulfate in a specific dosage range, porous cement-based sound-absorbing materials with excellent initial sound absorption performance, an initial average sound absorption coefficient greater than 0.52, and excellent weather resistance and durability can be stably prepared.

[0067] like Figure 1 , Figure 2 The images shown are SEM images of Embodiment 3 of this application under a closed state with high humidity and an open state with low humidity, respectively.

[0068] Furthermore, in Examples 1-6 of this application, after undergoing 20 freeze-thaw cycles, the sound absorption performance retention rate is as high as 95% or more, and the water absorption rate remains at a low level. This indicates that the technical solution of the present invention successfully constructs an effective and long-term stable humidity-responsive structure within the material, thereby systematically solving the technical problem in the prior art where high sound absorption performance and high weather resistance cannot be simultaneously achieved.

[0069] like Figure 3 , Figure 4 The images shown are high-magnification SEM images at a scale bar of 2 μm and low-magnification SEM images at a scale bar of 10 μm, respectively, after freeze-thaw cycles in Example 3 of this application.

[0070] The test results of comparative examples 1-12 are shown in Table 2: Table 2 According to the data in Table 2, although Example 3 and Comparative Examples 1-3 all exhibited superior initial sound absorption performance, the results after freeze-thaw cycles showed a precipitous difference in performance. Example 3 showed almost no performance loss, while the performance of Comparative Examples 1-3 collapsed by more than 50%. This result was unforeseen by those skilled in the art. The inventors speculate that this may be because only the unique diamino structure of lysine can provide long-lasting chemical protection for the copolymer in the strongly alkaline environment of cement. It was through in-depth research in the intersection of cement water chemistry and polymer chemistry that the inventors discovered this key to achieving long-term weather resistance. This choice was not a simple substitution or combination, but rather a creative endeavor based on a profound understanding of the underlying mechanisms.

[0071] Comparing the test results of Example 3 with those of Comparative Examples 4 and 5, it is easy to see that when the amount of amino acid-modified starch-based copolymer is too small, the material may fail to form a complete waterproof barrier, resulting in a significant decrease in freeze-thaw performance; while when the amount of amino acid-modified starch-based copolymer is too large, the initial sound absorption performance may be greatly reduced due to pore blockage. This illustrates that the selection of formulation content in the embodiments of this application is not a linear optimization result that can be easily screened through conventional orthogonal experiments, but rather a technical effect achieved by the inventors through extensive experimentation and creative labor.

[0072] In Comparative Examples 6-9, after replacing the ferrous salt with ferrous chloride, ferrous nitrate, ferrous carbonate, and ferrous acetate, even though all other components and amounts were exactly the same as in the optimal Example 3, the initial sound absorption performance of the resulting material completely collapsed. A possible reason is that the sulfate ions in the ferrous salt may interact with the cement hydration products, thus creating a synergistic effect with the amino acid-modified starch-based copolymer. This also reflects that the choice of ferrous salt was a creative choice made by the inventors after a deep understanding of complex reaction systems. Furthermore, when the amount of ferrous sulfate is too low, the sound absorption performance of the sound-absorbing material is almost lost, and when the amount reaches 10 parts, exceeding the amount in the embodiments of this application, the structural integrity and sound absorption function of the material also completely collapse. The test results of Comparative Example 12 also indicate that, under the formulation components of this application, the synergistic protection of nano-alumina enables the porous sound-absorbing material to achieve longer-lasting sound absorption stability.

[0073] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A humidity-responsive porous cement-based sound-absorbing material, characterized in that, By weight, its composition is as follows: 100 parts cement, 50 parts water, 16-22 parts amino acid modified starch-based copolymer, 3 parts hydrogen peroxide, 1.2-6 parts ferrous salt, and 0.2 parts nano alumina.

2. The humidity-responsive porous cement-based sound-absorbing material according to claim 1, characterized in that, The ferrous salt includes any one of ferrous chloride, ferrous nitrate, ferrous carbonate, ferrous acetate, and ferrous sulfate.

3. The humidity-responsive porous cement-based sound-absorbing material according to claim 2, characterized in that, The ferrous salt is ferrous sulfate.

4. The humidity-responsive porous cement-based sound-absorbing material according to claim 1, characterized in that, The nano-alumina is γ-phase nano-alumina powder.

5. The humidity-responsive porous cement-based sound-absorbing material according to claim 1, characterized in that, The humidity-responsive porous cement-based sound-absorbing material, by weight, comprises the following: 100 parts cement, 50 parts water, 20 parts lysine-modified starch-based copolymer, 3 parts hydrogen peroxide, 3.6 parts ferrous sulfate, and 0.2 parts nano-alumina.

6. The humidity-responsive porous cement-based sound-absorbing material according to claim 1, characterized in that, The preparation method of the amino acid-modified starch-based copolymer includes: preparation of starch-based copolymer and preparation of amino acid-modified starch-based copolymer; the preparation method of starch-based copolymer is as follows: weigh starch, place it in a reaction vessel, add deionized water, heat to 80-90℃, and keep it at this temperature for 1 hour to form starch paste; then cool to 50-60℃ for later use; then, under nitrogen protection, add Fenton's reagent to the above starch paste and stir to completely dissolve it; then, slowly add hydrogen peroxide solution; after the addition is completed, slowly add acrylic monomer through a dropping funnel; after the addition is completed, continue to keep the reaction at 50-60℃ for 2-4 hours; after the reaction is completed, adjust the pH of the reaction system to neutral; precipitate and break the gel with excess ethanol or acetone to precipitate solid polymer; wash the solid product repeatedly with an ethanol / water mixed solution several times, and finally dry the purified solid product to constant weight to obtain starch-based copolymer.

7. The humidity-responsive porous cement-based sound-absorbing material according to claim 6, characterized in that, The starch is potato starch, with a whiteness of not less than 90% and a Brabant peak viscosity of not less than 1200 BU.

8. The humidity-responsive porous cement-based sound-absorbing material according to claim 1, characterized in that, The preparation method of the amino acid modified starch-based copolymer is as follows: take the starch-based copolymer, disperse it in deionized water, and stir it thoroughly at room temperature to make it swell; add amino acids and stir to dissolve them; then, slowly add sodium hydroxide solution to adjust the pH value of the reaction system to 11; heat the reaction vessel to 70°C and react at a constant temperature for 10 hours under nitrogen protection; after the reaction is completed, transfer the obtained reaction solution to a dialysis bag, use a large amount of deionized water as the dialysis fluid, dialyze for 72 hours, and finally freeze-dry the purified product solution to obtain the amino acid modified starch-based copolymer.

9. A humidity-responsive porous cement-based sound-absorbing material according to claim 8, characterized in that, The amino acid in the amino acid-modified starch-based copolymer is any one of glutamic acid, lysine, aspartic acid, or glycine.

10. A method for preparing a humidity-responsive porous cement-based sound-absorbing material according to any one of claims 1-9, characterized in that, The preparation method of the porous cement-based sound-absorbing material includes the following steps: Step 1: Weigh the amino acid-modified starch-based copolymer and nano-alumina, add a small amount of water and perform ultrasonic dispersion treatment until a uniform suspension is formed; add hydrogen peroxide to the above suspension and stir evenly to obtain the active premix for use. Step 2: Prepare cement-based slurry. Weigh cement and place it in a mixer. Add water while mixing and mix at high speed to form a uniform cement paste. Add all the active premix prepared in Step 1 to the cement paste in Step 2 and mix thoroughly to form a foamed cement slurry. Step 3: Add ferrous salt and nano alumina to the above-mentioned cement foaming slurry, stir thoroughly, pour into a mold, let it stand to cure and then demold. Cur the demolded test block under the preset curing conditions until the specified age, thus obtaining a humidity-responsive porous cement-based sound-absorbing material.

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