Fly ash-based composite sound-absorbing material and preparation method thereof

Abstract

The application belongs to the technical field of solid waste resource utilization, and particularly relates to a fly ash-based composite sound-absorbing material and a preparation method thereof, which is prepared from the following raw materials in parts by mass: base fly ash 100 parts, modified sound-absorbing aggregate 30-70 parts, alkali activator 8-25 parts, water reducing agent 0.1-1.5 parts, defoaming agent 0.05-0.5 parts, and water 15-40 parts. The modified sound-absorbing aggregate prepared in advance improves the interface affinity of fly ash and perlite, solves the problem of easy pulverization after dry molding, and further improves the structural strength, anti-pulverization capacity and sound-absorbing performance of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically a fly ash-based composite sound-absorbing material and its preparation method. Background Technology

[0002] Noise pollution has become a significant issue affecting the human living environment, making the development of efficient, low-carbon, and environmentally friendly sound-absorbing materials a research hotspot in the fields of architectural acoustics and environmental engineering. Fly ash, as a massive industrial solid waste, is often used as a basic raw material for preparing sound-absorbing materials due to its porous and lightweight characteristics. In existing technologies, the preparation of sound-absorbing gel materials by compounding fly ash with expanded perlite, utilizing the open pore structure of perlite and the pozzolanic activity of fly ash to synergistically construct a lightweight porous network, is considered a cost-effective and resource-efficient technological approach. However, existing fly ash-based sound-absorbing materials still have some limitations in balancing structural strength, anti-pulverization ability, and sound absorption performance, affecting their practical application under complex working conditions. The prominent problems with the perlite-fly ash sound-absorbing gel system are as follows: the significant difference between the surface of perlite particles and the fly ash-based slurry leads to easy stratification and agglomeration during wet mixing, making it difficult to ensure uniform dispersion. Simultaneously, insufficient affinity between the inorganic gel precursor and the perlite interface often results in uneven local gelation reactions, leading to a detuned distribution of the internal pore structure of the material. This weakens the sound absorption coefficient in the mid-to-low frequency range and increases the risk of pulverization after drying and molding. These dispersibility and interfacial compatibility challenges have become key bottlenecks restricting the performance improvement and engineering application of this composite material.

[0003] CN108911689A discloses a sound-absorbing material composed of modified expanded perlite, sodium silicate, calcium silicate, and other raw materials. The porous nature of perlite improves the material's sound absorption performance. However, due to the lack of a reinforcing fiber skeleton, the sound-absorbing material modified with perlite alone exhibits insufficient toughness and is prone to brittle fracture under vibration or impact loads.

[0004] CN105174924A discloses a low-temperature sintered perlite sound-absorbing board and its preparation method. The method involves weighing 20-30 parts open-cell perlite, 30-40 parts closed-cell perlite, 15-20 parts borosilicate glass powder, 10-15 parts silica sol, 1-5 parts fly ash, 1-5 parts white clay, 1-3 parts aluminum dihydrogen phosphate, 1-3 parts sodium fluorosilicate, and 25-30 parts water according to a specific ratio. The mixture is then thoroughly mixed, pressed into shape, demolded, dried, and finally fired in a kiln. The perlite sound-absorbing board produced by this invention has high compressive strength and good sound absorption performance, with a large mid-to-high frequency sound absorption coefficient. However, the firing process not only increases costs but also easily leads to the closure of pores on the perlite surface, resulting in a decrease in sound absorption performance. Summary of the Invention

[0005] This invention provides a fly ash-based composite sound-absorbing material and its preparation method. By using pre-prepared modified sound-absorbing aggregate, the interfacial affinity between fly ash and perlite is improved, solving the problem of easy pulverization after drying and molding, thereby enhancing the structural strength, pulverization resistance and sound absorption performance of the composite material.

[0006] In a first aspect, the present invention provides a fly ash-based composite sound-absorbing material, which is prepared from raw materials comprising the following parts by weight: 100 parts of fly ash as base material, 30-70 parts of modified sound-absorbing aggregate, 8-25 parts of alkali activator, 0.1-1.5 parts of water-reducing agent, 0.05-0.5 parts of defoamer, and 15-40 parts of water. The modified sound-absorbing aggregate is prepared by the following method: First, 3-10 parts of phosphate binder are dissolved in 60-120 parts of water to obtain a phosphate solution; 2-8 parts of chopped fiber are added to the phosphate solution and stirred and dispersed at 300-600 r / min for 8-20 min; then 5-10 parts of coated fly ash are added and stirred at 150-300 r / min for 5-15 min to obtain a composite coated slurry; 100 parts of perlite are added to the composite coated slurry and stirred and soaked at 60-120 r / min for 10-30 min; after being taken out and drained, it is dried at 40-60℃ for 4-12 h until the mass is constant to obtain the modified sound-absorbing aggregate. The perlite has a particle size distribution of 2-4 mm, the chopped fibers have an average length of 1-3 mm, and the fly ash coated with D... 50 The D of the base material fly ash is 15-30 μm. 50 The thickness is 5-15 μm; the phosphate binder is either aluminum dihydrogen phosphate or magnesium dihydrogen phosphate; the drying weight gain of the modified sound-absorbing aggregate relative to perlite is 5%-15%.

[0007] This invention pre-prepares modified sound-absorbing aggregate, allowing chopped fibers and coated fly ash to form a composite coating layer on the surface of perlite particles under the action of a phosphate binder. During subsequent mixing with a fly ash-based slurry, the inorganic gel phase formed by the phosphate binder acts as a bridging structure, significantly enhancing the interfacial bonding strength between the perlite and the fly ash matrix. The three-dimensional network structure formed by the chopped fibers in the modified sound-absorbing aggregate plays a synergistic reinforcing role in the final composite material, effectively improving its toughness and impact resistance. The D-coated fly ash... 50 D greater than the base material fly ash 50This particle size design creates a transition interface between the modified sound-absorbing aggregate and the matrix, which is beneficial for stress transfer and sound wave propagation. The phosphate binder should ensure a sufficiently thick coating layer while avoiding excessive binder that could clog the pores of the perlite. The weight gain ratio is a low-cost and efficient process indicator reflecting the thickness of the coating layer on the surface of the modified sound-absorbing aggregate; a ratio below 5% indicates an excessively thin coating layer, which may result in an inadequate effective interfacial bonding layer. The water used in the preparation process of the modified sound-absorbing aggregate is not the same as the water used in the raw material components described in fly ash-based composite sound-absorbing materials.

[0008] Preferably, the base material fly ash is low-calcium F-type fly ash or high-calcium C-type fly ash, and the specific surface area of ​​the base material fly ash is controlled at 400-600 m². 2 / kg; the alkali activator is sodium silicate or potassium silicate with a modulus of 1.0-1.6, or a composite activator of sodium hydroxide and sodium silicate. When the composite activator is used, the mass ratio of sodium hydroxide to sodium silicate is 1:2-1:5; the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent or a naphthalene-based water-reducing agent, and the water reduction rate of the water-reducing agent is not less than 20%; the defoamer is an organosilicon defoamer.

[0009] Preferably, the chopped fiber is one or both of glass fiber and sisal fiber; when sisal fiber is used, the sisal fiber needs to undergo chemical modification treatment before use. The chemical modification treatment is to soak the fiber in a sodium hydroxide solution with a mass fraction of 2%-5% for 1-2 hours, then wash it with water at least 3 times until it is neutral and then dry it; the soaking time of the chemically modified sisal fiber in the composite coating slurry shall not exceed 15 minutes.

[0010] Preferably, the phosphate solution should be used within 24 hours of preparation. This is to prevent hydrolysis or polymerization of the phosphate, which could affect the bonding properties.

[0011] Preferably, the stirring method for the stirring and soaking in step one is intermittent forward and reverse stirring, with an alternation period of 30-60 seconds between forward and reverse rotation; the volume of the composite coating slurry is more than twice the volume of the perlite.

[0012] Preferably, the drying temperature is 40-50℃ and the drying time is 8-12 hours; when the drying temperature is 50-60℃, the drying time is 4-8 hours. Controlling the drying temperature and time ensures that the moisture in the modified sound-absorbing aggregate evaporates fully, while avoiding decomposition of the phosphate binder or aging of the fibers due to excessively high temperatures.

[0013] Preferably, if the weight gain after drying in step one is less than 5%, the composite coating slurry is prepared again according to step one. The modified sound-absorbing aggregate is then added to the prepared composite coating slurry and soaked for 5-15 minutes at a speed of 60-120 r / min. The aggregate is then drained again and dried at 40-60℃ to constant weight until the weight gain reaches 5%-15%.

[0014] This invention also proposes a method for preparing the above-mentioned fly ash-based composite sound-absorbing material, comprising the following steps: Step 1: Preparation of modified sound-absorbing aggregate; Step 2, Molding and Main Curing of Composite Sound Absorbing Material: Weigh out 100 parts of base material fly ash, 30-70 parts of modified sound-absorbing aggregate obtained in Step 1, 8-25 parts of alkali activator, 0.1-1.5 parts of water-reducing agent, 0.05-0.5 parts of defoamer, and 15-40 parts of water according to the proportions. Add these to a mixer and stir at 40-70 r / min for 3-6 seconds. The uniform slurry is obtained by pouring it into a mold and allowing it to stand for 1-4 hours at 20-30℃ for initial setting. Then, it is transferred to a curing chamber and cured for 24-48 hours at 50-80℃ and 90%-100% relative humidity. During the first 12 hours of curing, the curing temperature is controlled at 50-60℃, and then the temperature is raised to 60-80℃. After curing, the specimen is demolded and placed in a drying oven to dry at 65℃ until constant weight, thus obtaining the fly ash-based composite sound-absorbing material.

[0015] This invention prepares composite sound-absorbing materials using a two-step method: First, modified sound-absorbing aggregates are prepared, and a composite coating layer formed by chopped fibers and coated fly ash under the action of a phosphate binder is attached to the surface of perlite. Then, this modified sound-absorbing aggregate is mixed with fly ash, an alkali activator, etc., and formed through an alkali-activated gelation reaction. The phosphate binder in the modified sound-absorbing aggregate works synergistically with the alkali activator during subsequent curing to further enhance interfacial bonding. A stepped temperature-increasing curing regime allows the matrix to gradually solidify, avoiding internal stress concentration and cracking caused by excessively rapid temperature rise.

[0016] Preferably, the stirring speed in step two is 50-60 r / min; the optimized conditions for the main curing are: curing temperature 60-70℃, relative humidity 95%-100%, and curing time 36h.

[0017] The fly ash-based composite sound-absorbing material mentioned in this invention can be used for indoor sound insulation in buildings, road sound barriers, or noise reduction in industrial plants.

[0018] The present invention has the following significant improvements over the prior art: 1. This invention effectively solves the technical problem of insufficient interfacial affinity between perlite and fly ash-based slurry in existing technologies by pre-preparing modified sound-absorbing aggregates. The phosphate binder in the modified sound-absorbing aggregate forms an inorganic binder phase on the perlite surface. This binder phase has a similar chemical composition and crystal structure to the alkali-activated cementitious products in the fly ash matrix, allowing for chemical bonding and significantly improving interfacial bonding strength. The network structure formed by chopped fibers in the modified sound-absorbing aggregate acts as a bridge and stress transfer agent in the composite material, effectively inhibiting crack propagation and improving the material's toughness and impact resistance.

[0019] 2. The preparation method of this invention uses an alkali-activated gelation system, eliminating the need for high-temperature sintering and avoiding the problem of reduced sound absorption caused by the closure of pores on the perlite surface during sintering. Simultaneously, the lower curing temperature and relatively simpler process conditions reduce production costs and improve production efficiency. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical inventions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] Example 1 A method for preparing a fly ash-based composite sound-absorbing material includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Take 5 parts of aluminum dihydrogen phosphate and dissolve it in 80 parts of water, stirring until completely dissolved to obtain a phosphate solution; add 4 parts of chopped glass fiber to the phosphate solution and disperse using a high-speed disperser at 400 r / min for 12 min to ensure the glass fiber is fully and evenly dispersed in the phosphate solution; then add D 50 Eight parts of 20μm coated fly ash were stirred at 250 r / min for 8 min to obtain a uniform composite coating slurry. One hundred parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred at 100 r / min for 20 min to ensure the perlite particles were fully wetted and absorbed by the composite coating slurry. After removing the perlite, excess slurry was drained, and the mixture was dried in a drying oven at 50℃ for 8 h until the mass remained constant, thus obtaining the modified sound-absorbing aggregate. The mass of the dried modified sound-absorbing aggregate was measured, and the weight gain relative to the perlite was calculated to be 10%. Step 2, Molding and Curing of Composite Sound-Absorbing Materials: The following raw materials were weighed according to the specified proportions: 100 parts of low-calcium type F fly ash, 50 parts of the modified sound-absorbing aggregate obtained in step one, 15 parts of sodium silicate activator with a modulus of 1.3, 0.8 parts of polycarboxylate superplasticizer, 0.2 parts of silicone defoamer, and 25 parts of water; the specific surface area of ​​the low-calcium type F fly ash was 480 m². 2 / kg, D 50 The diameter is 10 μm; the average length of the chopped glass fibers is 2 mm. The above raw materials were put into a concrete mixer and mixed at 55 r / min for 4 min to obtain a uniform slurry. The slurry was then poured into a 100mm×100mm×50mm mold and allowed to set for 2 hours at 25℃. The mold was then transferred to a curing chamber and cured for 36 hours at 55℃ and 95% relative humidity. The temperature was controlled at 55℃ for the first 12 hours, and then the temperature was raised to 60℃ and maintained until the end of curing. After curing, the mold was removed and the demolded specimen was placed in a drying oven and dried at 65℃ to constant weight to obtain the fly ash-based composite sound-absorbing material of this embodiment.

[0022] Example 2 A method for preparing a fly ash-based composite sound-absorbing material includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Take 3 parts of magnesium dihydrogen phosphate and dissolve it in 120 parts of water, stirring until completely dissolved to obtain a phosphate solution; add 2 parts of chopped sisal fiber to the phosphate solution, and disperse using a high-speed disperser at 300 r / min for 20 min to ensure the sisal fiber is fully and evenly dispersed in the phosphate solution; then add D 50 Five parts of 15μm coated fly ash were stirred at 150 r / min for 15 min to obtain a uniform composite coating slurry. One hundred parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred at 60 r / min for 30 min to ensure the perlite particles were fully wetted and adsorbed by the composite coating slurry. After removing the perlite, excess slurry was drained, and the mixture was placed in a drying oven and dried at 40℃ for 12 h until the mass remained constant, thus obtaining the modified sound-absorbing aggregate. The mass of the dried modified sound-absorbing aggregate was measured, and the weight gain relative to perlite was calculated to be 6%.

[0023] The sisal fiber undergoes chemical modification treatment before use: it is soaked in a 2% sodium hydroxide solution for 2 hours, then washed with water three times until neutral and dried; the modified sisal fiber is soaked in the composite coating slurry for 30 minutes, of which the effective soaking time is 30 minutes (the alkali-treated sisal fiber participates in the phosphate slurry throughout the process). Step 2, Molding and Curing of Composite Sound-Absorbing Materials: The following raw materials were weighed according to the following proportions: 100 parts of high-calcium C-type base fly ash, 30 parts of modified sound-absorbing aggregate obtained in step one, 25 parts of potassium silicate activator with a modulus of 1.0, 1.5 parts of naphthalene-based water-reducing agent, 0.5 parts of organosilicon defoamer, and 40 parts of water; the specific surface area of ​​the high-calcium C-type fly ash was 600 m². 2 / kg, D 50 The fiber diameter is 5 μm; the average length of the sisal fiber is 3 mm. The above raw materials were put into a concrete mixer and mixed at 40 r / min for 6 min to obtain a uniform slurry. The slurry was then poured into a 100mm×100mm×50mm mold and allowed to set for 4 hours at 20℃. The mold was then transferred to a curing chamber and cured for 48 hours at 50℃ and 90% relative humidity. The temperature was controlled at 50℃ for the first 12 hours, and then the temperature was raised to 80℃ and maintained until the end of curing. After curing, the mold was removed and the demolded specimen was placed in a drying oven and dried at 65℃ to constant weight to obtain the fly ash-based composite sound-absorbing material of this embodiment.

[0024] Example 3 A method for preparing a fly ash-based composite sound-absorbing material includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Take 10 parts of aluminum dihydrogen phosphate and dissolve it in 60 parts of water, stirring until completely dissolved to obtain a phosphate solution; add 8 parts of chopped glass fiber to the phosphate solution, and disperse using a high-speed disperser at 600 r / min for 8 min to ensure the glass fiber is fully and evenly dispersed in the phosphate solution; then add D 50 Ten parts of 30μm coated fly ash were stirred at 300 r / min for 5 min to obtain a uniform composite coating slurry. One hundred parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred and soaked at 120 r / min for 10 min. The stirring and soaking method was intermittent forward and reverse stirring, with an alternation cycle of 40 s, to ensure that the perlite particles were fully wetted and absorbed by the composite coating slurry. After removing the perlite, excess slurry was drained, and the mixture was placed in a drying oven and dried at 60℃ for 4 h until the mass was constant, thus obtaining the modified sound-absorbing aggregate. The mass of the dried modified sound-absorbing aggregate was measured, and the weight gain relative to perlite was calculated to be 15%. Step 2, Molding and Curing of Composite Sound-Absorbing Materials: The following raw materials were weighed according to the following proportions: 100 parts of low-calcium type F fly ash, 70 parts of the modified sound-absorbing aggregate obtained in step one, 8 parts of sodium silicate activator with a modulus of 1.6, 0.1 parts of polycarboxylate-based high-efficiency water-reducing agent, 0.05 parts of organosilicon defoamer, and 15 parts of water; the specific surface area of ​​the low-calcium type F fly ash was 400 m².2 / kg, D 50 The diameter is 15 μm; the average length of the chopped glass fibers is 1 mm. The above raw materials were put into a concrete mixer and stirred at 70 r / min for 3 min to obtain a uniform slurry. The slurry was then poured into a 100mm×100mm×50mm mold and allowed to set for 1 hour at 30℃. The mold was then transferred to a curing chamber and cured for 24 hours at 80℃ and 100% relative humidity. The temperature was controlled at 60℃ for the first 12 hours, and then the temperature was raised to 80℃ and maintained until the end of curing. After curing, the mold was removed and the demolded specimen was placed in a drying oven and dried at 65℃ to constant weight to obtain the fly ash-based composite sound-absorbing material of this embodiment.

[0025] Example 4 A method for preparing a fly ash-based composite sound-absorbing material includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Take 7 parts of magnesium dihydrogen phosphate and dissolve it in 100 parts of water, stirring until completely dissolved to obtain a phosphate solution; add 5 parts of chopped sisal fiber to the phosphate solution, and disperse using a high-speed disperser at 500 r / min for 15 min to ensure the sisal fiber is fully and evenly dispersed in the phosphate solution; then add D 50 Eight parts of 25μm coated fly ash were stirred at 200 r / min for 10 min to obtain a uniform composite coating slurry. One hundred parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred at 90 r / min for 20 min to ensure the perlite particles were fully wetted and absorbed by the composite coating slurry. After removing the perlite, excess slurry was drained, and the mixture was dried in a drying oven at 55℃ for 6 h until the mass remained constant, thus obtaining the modified sound-absorbing aggregate. The mass of the dried modified sound-absorbing aggregate was measured, and the weight gain relative to perlite was calculated to be 12%.

[0026] The sisal fiber undergoes chemical modification treatment before use: it is soaked in a 5% sodium hydroxide solution for 1 hour, then washed with water four times until neutral and dried; the modified sisal fiber is soaked in the composite coating slurry for 20 minutes. Step 2, Molding and Curing of Composite Sound-Absorbing Materials: The following raw materials were weighed according to the following proportions: 100 parts of high-calcium C-type base fly ash, 50 parts of modified sound-absorbing aggregate obtained in step one, 20 parts of composite activator, 0.6 parts of polycarboxylate-based high-efficiency water-reducing agent, 0.3 parts of organosilicon defoamer, and 30 parts of water; the composite activator is a mixture of sodium hydroxide and sodium silicate, wherein the mass ratio of sodium hydroxide to sodium silicate is 1:3; the specific surface area of ​​the high-calcium C-type fly ash is 520 m².2 / kg, D 50 The fiber diameter is 12 μm; the average length of the sisal fiber is 2 mm. The above raw materials were put into a concrete mixer and mixed at 60 r / min for 5 min to obtain a uniform slurry. The slurry was then poured into a 100mm×100mm×50mm mold and allowed to set for 3 hours at 25℃. The mold was then transferred to a curing chamber and cured for 36 hours at 65℃ and 98% relative humidity. The temperature was controlled at 55℃ for the first 12 hours, and then the temperature was raised to 65℃ and maintained until the end of curing. After curing, the mold was removed and the demolded specimen was placed in a drying oven and dried at 65℃ to constant weight to obtain the fly ash-based composite sound-absorbing material of this embodiment.

[0027] Example 5 A method for preparing a fly ash-based composite sound-absorbing material includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Take 6 parts of aluminum dihydrogen phosphate and dissolve it in 90 parts of water, stirring until completely dissolved to obtain a phosphate solution; add 3 parts of chopped glass fiber and 3 parts of chopped sisal fiber to the phosphate solution, and disperse using a high-speed disperser at 450 r / min for 18 min to ensure that the two fibers are fully and evenly dispersed in the phosphate solution; then add D 50 Nine parts of 18μm coated fly ash were stirred at 220 r / min for 12 min to obtain a uniform composite coating slurry. One hundred parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred at 80 r / min for 25 min to ensure the perlite particles were fully wetted and absorbed by the composite coating slurry. After removing the perlite, excess slurry was drained, and the mixture was dried in a drying oven at 45℃ for 10 h until the mass remained constant, thus obtaining the modified sound-absorbing aggregate. The mass of the dried modified sound-absorbing aggregate was measured, and the weight gain relative to perlite was calculated to be 8%.

[0028] The sisal fiber undergoes chemical modification treatment before use: it is soaked in a 3% sodium hydroxide solution for 1.5 hours, then washed with water three times until neutral and dried; the modified sisal fiber is soaked in the composite coating slurry for 25 minutes. Step 2, Molding and Curing of Composite Sound-Absorbing Materials: The following raw materials were weighed according to the specified proportions: 100 parts of low-calcium F-type base fly ash, 60 parts of modified sound-absorbing aggregate obtained in step one, 12 parts of sodium silicate activator with a modulus of 1.4, 0.4 parts of naphthalene-based water-reducing agent, 0.15 parts of organosilicon defoamer, and 35 parts of water; the specific surface area of ​​the low-calcium F-type fly ash was 550 m² / g. 2 / kg, D50 The diameter is 8μm; the average length of the chopped glass fiber is 2mm, and the average length of the chopped sisal fiber is 2mm; The above raw materials were put into a concrete mixer and mixed at 50 r / min for 5 min to obtain a uniform slurry. The slurry was then poured into a 100mm×100mm×50mm mold and allowed to set for 2.5 h at 28℃. The mold was then transferred to a curing chamber and cured for 40 h at 70℃ and 92% relative humidity. The temperature was controlled at 55℃ for the first 12 h, and then the temperature was raised to 70℃ and maintained until the end of curing. After curing, the mold was removed and the demolded specimen was placed in a drying oven and dried at 65℃ to constant weight to obtain the fly ash-based composite sound-absorbing material of this embodiment.

[0029] Comparative Example 1 The difference from Example 1 is that no modified sound-absorbing aggregate was prepared, and no chopped fibers were added, specifically: Weigh the following raw materials according to the proportions: 100 parts of low-calcium F-type base material fly ash, 50 parts of unmodified perlite particles, 12 parts of sodium silicate activator with a modulus of 1.4, 0.4 parts of naphthalene-based water-reducing agent, 0.15 parts of organosilicon defoamer, and 35 parts of water; the remaining steps are the same as in Example 1.

[0030] Comparative Example 2 The difference from Example 1 is that no modified sound-absorbing aggregate was prepared, and short-cut fibers were added, specifically: Weigh the following raw materials according to the proportions: 100 parts of low-calcium F-type base material fly ash, 45 parts of perlite particles as in Example 1, 5 parts of short-cut fibers as in Example 1, 12 parts of sodium silicate activator with a modulus of 1.4, 0.4 parts of naphthalene-based water-reducing agent, 0.15 parts of organosilicon defoamer, and 35 parts of water; the remaining steps and parameters are the same as in Example 1.

[0031] Comparative Example 3 The difference from Example 1 is that the perlite was not stirred and soaked in the composite coating slurry for a sufficient time in step one, and the weight gain of the modified sound-absorbing aggregate after drying was only 3% relative to the perlite; the remaining steps and parameters are the same as in Example 1.

[0032] Comparative Example 4 The difference from Example 1 is that the coating fly ash and the base fly ash are from the same batch of fly ash, namely D. 50 All were 20 μm; the remaining steps and parameters were the same as in Example 1.

[0033] Comparative Example 5 The difference from Example 1 is that in step one, the preparation of the modified sound-absorbing aggregate: Ten parts of aluminum dihydrogen phosphate were dissolved in 60 parts of water and stirred until completely dissolved to obtain a phosphate solution. Eight parts of chopped glass fiber were added to the phosphate solution and dispersed using a high-speed disperser at 600 r / min for 8 min to ensure the glass fiber was fully and evenly dispersed in the phosphate solution. Subsequently, 100 parts of perlite with a particle size distribution of 2-4 mm were added to the composite coating slurry and stirred and soaked at 120 r / min for 10 min to ensure the perlite particles were fully wetted and adsorbed into the composite coating slurry. After removal, excess slurry was drained from the surface, and the mixture was placed in a drying oven and dried at 60℃ for 4 h until the mass was constant to obtain the modified sound-absorbing aggregate. The mass of the modified sound-absorbing aggregate after drying was measured, and the weight gain relative to perlite was calculated to be 4%. The aggregate was then added back into the newly prepared composite coating slurry of this comparative example and stirred and soaked until the weight gain was 5%. The remaining steps and parameters were the same as in Example 1.

[0034] Comparative Example 6 The difference from Example 1 is that the drying temperature in step one is too high, at 100°C; the remaining steps and parameters are the same as in Example 1.

[0035] Comparative Example 7 The difference from Example 1 is that in step two, the mixture is put into a mixer and stirred at a speed of 100 r / min; the remaining steps and parameters are the same as in Example 1.

[0036] Comparative Example 8 The difference from Example 1 is that the average length of the chopped glass fibers is 0.5 mm; the remaining steps and parameters are the same as in Example 1.

[0037] For the specimens prepared in the above embodiments and comparative examples, a blank group (made of pure fly ash) was added and its performance was tested according to the following method: 1. Sound absorption coefficient: The sound absorption coefficient was measured using the transfer function method according to GB / T18696.2-2002 "Measurement of sound absorption coefficient and specific acoustic impedance in acoustic impedance tubes". The test frequency range was 100-5000 Hz. The average sound absorption coefficient was recorded (the average value of six center frequencies: 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz).

[0038] 2. Compressive strength: The test shall be conducted in accordance with the loading rate and failure load recording method in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The specimen size shall be 100mm×100mm×50mm. The compressive strength shall be calculated by dividing the failure load by the area under pressure.

[0039] 3. Anti-pulverization performance: Place the specimen on a vibrating screen and vibrate at a frequency of 50 Hz for 30 minutes. Measure the mass loss rate before and after vibration. The lower the mass loss rate, the better the anti-pulverization performance.

[0040] The test data is summarized in Table 1.

[0041] Table 1. Test results of the examples and comparative examples.

[0042] The test data of the examples and comparative examples show clear grouping characteristics. The examples are significantly better than the comparative examples in terms of sound absorption coefficient, compressive strength and mass loss rate, and there is no significant loss in mechanical properties compared with the blank group.

[0043] Compared to Example 1, Comparative Example 1 did not prepare modified sound-absorbing aggregate and did not add chopped fibers, which addresses the compatibility issue mentioned in the background section, resulting in poor overall performance. This demonstrates that the pre-preparation of modified sound-absorbing aggregate is the core means to solve the interfacial compatibility problem. Although Comparative Example 2 added chopped fibers, they were randomly dispersed in the matrix, failing to alter the surface of the perlite particles, resulting in limited reinforcement and a performance improvement far less than that of the Example. Comparative Example 3 had a low weight gain and its performance was inferior to Example 1, indicating that the coating layer thickness was insufficient to establish an effective interfacial transition zone between the perlite and the matrix, resulting in insufficient interfacial bonding strength and a decrease in both mechanical and sound absorption properties compared to the Example. In Comparative Example 4, the coated fly ash and the base fly ash had the same particle size, the particle size gradient structure disappeared, and the average sound absorption coefficient and compressive strength decreased. This indicates that the gradient design of the coated fly ash particle size being larger than that of the base fly ash has a substantial contribution to both acoustic and mechanical properties. Comparative Example 5, which did not include coated fly ash in the preparation of modified sound-absorbing aggregate, showed a decrease in acoustic and mechanical properties, as well as a simultaneous decrease in anti-pulverization ability, indicating that coated fly ash is an indispensable component in the structure of modified sound-absorbing aggregate. Comparative Example 6, with a drying temperature reaching 100℃, exceeded the upper limit set by this invention, resulting in a performance decline compared to Example 1, demonstrating that the drying temperature does affect performance. In Comparative Example 7, the high main stirring speed caused some fibers and coated fly ash to peel off from the perlite surface, resulting in overall performance inferior to Example 1, verifying the necessity of low-speed stirring for protecting the structural integrity of modified sound-absorbing aggregate. In Comparative Example 8, the chopped fibers were too short, leading to a decrease in anti-pulverization effect compared to Example 1.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical invention of this application, and not to limit it; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical invention described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical invention to deviate from the scope of the technical invention of the embodiments of this application.

[0045] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fly ash-based composite sound-absorbing material, characterized in that, It is prepared from the following raw materials in parts by weight: 100 parts base material fly ash, 30-70 parts modified sound-absorbing aggregate, 8-25 parts alkali activator, 0.1-1.5 parts water-reducing agent, 0.05-0.5 parts defoamer, and 15-40 parts water; The modified sound-absorbing aggregate is prepared by the following method: first, 3-10 parts of phosphate binder are dissolved in 60-120 parts of water to obtain a phosphate solution; 2-8 parts of chopped fiber are added to the phosphate solution, and after stirring and dispersing, 5-10 parts of coated fly ash are added and stirred to obtain a composite coated slurry; Add 100 parts of perlite to the composite coating slurry, stir, soak, drain, and dry until the quality is constant to obtain the modified sound-absorbing aggregate. The perlite has a particle size distribution of 2-4 mm, the chopped fibers have an average length of 1-3 mm, and the fly ash coated with D... 50 The D of the base material fly ash is 15-30 μm. 50 The thickness is 5-15 μm; the phosphate binder is either aluminum dihydrogen phosphate or magnesium dihydrogen phosphate; the drying weight gain of the modified sound-absorbing aggregate relative to perlite is 5%-15%.

2. The fly ash-based composite sound-absorbing material according to claim 1, characterized in that, The base material fly ash is low-calcium F-type fly ash or high-calcium C-type fly ash, and the specific surface area of ​​the base material fly ash is controlled at 400-600 m². 2 / kg; the alkali activator is sodium silicate or potassium silicate with a modulus of 1.0-1.6, or a composite activator of sodium hydroxide and sodium silicate; the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent or a naphthalene-based water-reducing agent; the defoamer is an organosilicon defoamer.

3. The fly ash-based composite sound-absorbing material according to claim 1, characterized in that, The chopped fibers are one or both of glass fibers and sisal fibers. When sisal fibers are used, the sisal fibers need to undergo chemical modification treatment before use. The chemical modification treatment is to soak the fibers in a sodium hydroxide solution with a mass fraction of 2%-5% for 1-2 hours, then wash them with water at least 3 times until they are neutral and then dry them.

4. The fly ash-based composite sound-absorbing material according to claim 1, characterized in that, The stirring and soaking process is carried out by intermittent forward and reverse stirring, with an alternation period of 30-60 seconds between forward and reverse rotation.

5. The fly ash-based composite sound-absorbing material according to claim 1, characterized in that, If the weight gain of the modified sound-absorbing aggregate relative to perlite is less than 5%, the modified sound-absorbing aggregate should be added to a newly prepared composite coating slurry and soaked for 5-15 minutes at a speed of 60-120 r / min, drained again, and dried at 40-60℃ to constant weight until the weight gain reaches 5%-15%.

6. A method for preparing a fly ash-based composite sound-absorbing material as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1, Preparation of modified sound-absorbing aggregate: Modified sound-absorbing aggregate is prepared according to the method for preparing modified sound-absorbing aggregate as described in claim 1; Step 2, molding and main curing of composite sound-absorbing material: Weigh 100 parts of base material fly ash, 30-70 parts of modified sound-absorbing aggregate obtained in Step 1, 8-25 parts of alkali activator, 0.1-1.5 parts of water-reducing agent, 0.05-0.5 parts of defoamer, and 15-40 parts of water according to the proportion, and put them into a mixer to stir to obtain a uniform slurry; pour the uniform slurry into a mold, let it stand for initial setting, and then transfer it to a curing box for main curing at a temperature of 50-80℃ and a relative humidity of 90%-100% for 24-48 hours; after the main curing is completed, demold and dry to constant weight to obtain the fly ash-based composite sound-absorbing material.

7. The method for preparing fly ash-based composite sound-absorbing material according to claim 6, characterized in that, In step two, the mixer is stirred at a speed of 40-70 r / min for 3-6 minutes.

8. The method for preparing fly ash-based composite sound-absorbing material according to claim 6, characterized in that, During the first 12 hours of the main curing process, the curing temperature should be controlled at 50-60℃, and then the temperature should be raised to 60-80℃ to continue curing.

9. The method for preparing fly ash-based composite sound-absorbing material according to claim 6, characterized in that, The demolded specimens were dried in a drying oven at 65°C.

10. The fly ash-based composite sound-absorbing material according to any one of claims 1-5 is applied to indoor sound insulation in buildings, road sound barriers, or noise reduction in industrial plants.

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