Modified limestone, and preparation method and application thereof

Abstract

The application relates to the field of building materials and discloses modified limestone as well as a preparation method and application thereof, the modified limestone is prepared by using octamethylcyclotetrasiloxane, tetraethyl orthosilicate and gamma-methacryloyloxypropyl trimethoxysilane as organosilicon monomers, double bond limestone, isoamyl alcohol polyoxyethylene ether and acrylic monomers performing free radical copolymerization, initiating copolymerization of the double bonds on the limestone surface, the double bonds on the solution three hybrid emulsion microparticles, the isoamyl alcohol polyoxyethylene ether and the acrylic monomers, and firmly fixing the polymer shell layer on the limestone surface through chemical bonding to prepare coated limestone, and then using phosphoric acid, triethanolamine, aluminum hydroxide and the coated limestone as raw materials to prepare the modified limestone, the prepared modified limestone is applied to concrete, excellent compressive strength and durability are given to the concrete, and the concrete has good impermeability and fluidity.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a modified limestone, its preparation method, and its application. Background Technology

[0002] In today's booming construction industry, concrete is widely used as a core building material. Traditional concrete is mostly cement concrete, which uses cement as a binder, sand and stone as aggregates, and water and other raw materials in a certain proportion. Concrete is widely used in civil engineering due to its advantages such as readily available and abundant raw materials and excellent performance.

[0003] Limestone powder, with its abundant supply, low price, and potential pozzolanic activity, has become a promising mineral admixture. Currently, the main method for processing limestone powder is as a cementitious admixture. However, this method does not significantly improve the performance of cement and concrete, and its low dosage results in very limited technical and economic benefits. Furthermore, directly using it as a mineral admixture in concrete at large dosages not only reduces the strength grade of the concrete but also accelerates the hydration reaction of cement, leading to a faster loss of workability. Due to the low activity of limestone powder itself, although using it as a mineral admixture can improve the early strength and fluidity of concrete to some extent, it is significantly insufficient in terms of later-stage strength. In addition, limestone powder suffers from poor impermeability and insufficient compressive strength. These performance shortcomings make it difficult for limestone powder to meet the high durability requirements of concrete in special engineering environments, thus limiting its application potential. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a modified limestone, its preparation method, and its application. The modified limestone prepared is applied to concrete, giving the concrete excellent compressive strength and durability, while also possessing good impermeability and fluidity.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing modified limestone includes the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Ethanol, deionized water, glacial acetic acid, pretreated limestone, hydroquinone and γ-methacryloyloxypropyltrimethoxysilane were placed in a reactor, ultrasonically dispersed evenly, and reacted at 70~85℃ for 20~24h. Then, the mixture was cooled to room temperature, centrifuged, washed and dried to prepare double-bonded limestone. S3. Take deionized water, dodecylbenzenesulfonic acid and octylphenol polyoxyethylene ether in a reactor, heat to 40~50℃ and stir to mix evenly to obtain solution one. Take dodecylbenzenesulfonic acid and octylphenol polyoxyethylene ether and dissolve them in deionized water. Then add octamethylcyclotetrasiloxane, tetraethyl orthosilicate and γ-methacryloyloxypropyltrimethoxysilane and mix evenly to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 2-3 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 8-10 using sodium hydroxide aqueous solution, and heat to 75-85℃ to obtain solution 3. S5. Take double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and deionized water. Then, add isopentenyl alcohol polyoxyethylene ether, ethylene glycol dimethacrylate, dodecyl mercaptan, acrylic acid and initiator dropwise. The dropwise addition time is 3-4 hours, and the temperature is controlled at 55-65℃. After the dropwise addition is completed, place it at 75-85℃ for 5-6 hours to react. After the reaction is completed, centrifuge, wash and dry to prepare coated limestone. S6. Take phosphoric acid, triethanolamine and deionized water into a reactor, add aluminum hydroxide in portions, stir evenly and react at room temperature for 20-24 hours, then add coated limestone, continue stirring and react for 2-3 hours, then let stand and react for 5-6 hours, then add calcium hydroxide with a mass fraction of 6-8%, mix and stir evenly to prepare modified limestone.

[0006] Preferably, the pretreated limestone has a particle size of 2~8µm.

[0007] Preferably, the addition ratio of ethanol, deionized water, glacial acetic acid, pretreated limestone, hydroquinone and γ-methacryloyloxypropyltrimethoxysilane is 80~100mL: 5~15mL: 1~1.5mL: 5g: 0.05~0.07g: 2.5~3mL.

[0008] Preferably, the mass ratio of octamethylcyclotetrasiloxane, tetraethyl orthosilicate, γ-methacryloyloxypropyltrimethoxysilane, isopentenyl polyoxyethylene ether, acrylic acid, ethylene glycol dimethacrylate, and dodecanethiol is 41.5:8.5:25.2~31.5:10.8~13.5:5.7~7.1:0.36~0.45:0.18~0.22.

[0009] Preferably, the initiator is either ammonium persulfate or potassium persulfate.

[0010] Preferably, the addition ratio of phosphoric acid, triethanolamine, deionized water, aluminum hydroxide and coated limestone is 10mL:8~12mL:7~10mL:3~4g:3~5g.

[0011] A modified limestone, prepared by the method described above.

[0012] Application of a modified limestone as described above in concrete.

[0013] Preferably, the concrete comprises the following raw materials in parts by weight: 320-450 parts cement, 50-120 parts silica fume, 85-150 parts fly ash, 300-450 parts fine aggregate, 140-220 parts quartz sand, 60-100 parts modified limestone, 4-10 parts water-reducing agent, and 140-260 parts water; The preparation method includes the following steps: weigh each raw material according to the weight parts, add cement, silica fume, fine aggregate, quartz sand and modified limestone into a mixer, mix and then add water, fly ash and water-reducing agent, mix evenly, and prepare concrete.

[0014] Preferably, the cement is any one of P·O42.5 grade ordinary Portland cement or P·O52.5 grade ordinary Portland cement; the fine aggregate is river sand with a fineness modulus between 2.4 and 2.8; the water-reducing agent is any one of polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, or sulfonate-based water-reducing agent; and the quartz sand has a particle size of 100-210µm.

[0015] The beneficial effects of this invention are: This invention utilizes the silanol groups generated from the hydrolysis of γ-methacryloxypropyltrimethoxysilane to undergo dehydration condensation with the hydroxyl groups on the surface of pretreated limestone, preparing double-bonded limestone. Then, using octamethylcyclotetrasiloxane, tetraethyl orthosilicate, and γ-methacryloxypropyltrimethoxysilane as organosilicon monomers, a free radical copolymerization reaction is carried out between the double-bonded limestone, isopentenyl alcohol polyoxyethylene ether, and acrylic acid monomers. Ethylene glycol dimethacrylate is used as a crosslinking agent, dodecyl mercaptan as a chain transfer agent, and dodecylbenzenesulfonic acid and octylphenol polyoxyethylene ether as emulsifiers. Under heating conditions, the initiator decomposes to generate free radicals, initiating the polymerization of the limestone. The double bonds on the surface, the double bonds on the hybrid emulsion particles in the solution, isopentenyl alcohol polyoxyethylene ether and acrylic monomer undergo a copolymerization reaction, and the polymer shell is firmly fixed to the limestone surface through chemical bonding to form a strong core-shell structure, thus preparing coated limestone. This grafting of organosiloxane long chains and polycarboxylate superplasticizer onto the limestone surface can enhance the dispersibility of limestone, enabling it to uniformly fill the pores of the matrix material. Furthermore, the macromolecular polymer on the limestone surface can entangle with the hydration products of the matrix, optimizing the internal structure of the matrix material, thereby enhancing the density, durability and mechanical strength of concrete.

[0016] This invention utilizes phosphoric acid, triethanolamine, aluminum hydroxide, and coated limestone as raw materials to prepare modified limestone. The Si-OH groups on the surface of the coated limestone can undergo a condensation reaction with the P-OH groups in the aluminophosphate network to form Si-OP or Si-O-Al chemical bonds. Simultaneously, the coated limestone is effectively dispersed and integrated into the reaction system, fully utilizing its effective properties. Furthermore, the added calcium hydroxide neutralizes the remaining free phosphoric acid in the system and provides abundant calcium ions required for subsequent pozzolanic reactions in concrete. Additionally, triethanolamine, a commonly used concrete accelerator, introduces phosphate groups that react with Ca... 2+ It has a strong complexing ability, which can generate more adsorption on the surface of cement particles. The increased adsorption increases the repulsive force between cement particles, thereby improving the fluidity of the paste. At the same time, it can improve the dispersion of cement particles, which is conducive to the full hydration of cement. It optimizes the pore structure, making the internal structure of concrete more compact, thereby improving the later strength of concrete. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: A method for preparing modified limestone, comprising the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Take 90 mL of ethanol, 10 mL of deionized water, 1.2 mL of glacial acetic acid, 5 g of pretreated limestone, 0.06 g of hydroquinone and 2.8 mL of γ-methacryloyloxypropyltrimethoxysilane into a reactor, disperse them evenly by ultrasonication, react them at 80 °C for 24 h, then cool to room temperature, centrifuge, wash and dry to prepare double-bonded limestone; S3. Take 200 mL of deionized water, 1.8 g of dodecylbenzenesulfonic acid, and 0.9 g of octylphenol polyoxyethylene ether in a reactor, heat to 45 °C, and stir until homogeneous to obtain solution one. Take 1.5 g of dodecylbenzenesulfonic acid and 0.8 g of octylphenol polyoxyethylene ether and dissolve them in 150 mL of deionized water. Then add 41.5 g of octamethylcyclotetrasiloxane, 8.5 g of tetraethyl orthosilicate, and 25.7 g of γ-methacryloyloxypropyltrimethoxysilane and mix until homogeneous to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 2 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 8.5 using a 3% sodium hydroxide aqueous solution, and heat to 80℃ to obtain solution 3. S5. Take 5g of double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and 20mL of deionized water. Then, simultaneously add 10.8g of isopentenyl polyoxyethylene ether, 0.36g of ethylene glycol dimethacrylate, 0.18g of dodecyl mercaptan, 5.8g of acrylic acid, and 0.09g of potassium persulfate aqueous solution (10% by mass) as an initiator. The addition time is 3.5h, and the temperature is controlled at 60℃. After the addition is completed, the mixture is placed at 80℃ for 5h. After the reaction is completed, the mixture is centrifuged, washed, and dried to prepare coated limestone. S6. Take 10 mL of phosphoric acid, 8 mL of triethanolamine and 7 mL of deionized water into a reactor, add 3.5 g of aluminum hydroxide in portions, stir evenly and react at room temperature for 24 h, then add 3.5 g of coated limestone, continue stirring and react for 2 h, then let stand and react for 5 h, then add 6% calcium hydroxide by mass, mix and stir evenly to prepare modified limestone.

[0019] Example 2 A method for preparing modified limestone, comprising the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Take 90 mL of ethanol, 10 mL of deionized water, 1.2 mL of glacial acetic acid, 5 g of pretreated limestone, 0.06 g of hydroquinone and 2.8 mL of γ-methacryloyloxypropyltrimethoxysilane into a reactor, disperse them evenly by ultrasonication, react them at 80 °C for 24 h, then cool to room temperature, centrifuge, wash and dry to prepare double-bonded limestone; S3. Take 200 mL of deionized water, 1.8 g of dodecylbenzenesulfonic acid, and 0.9 g of octylphenol polyoxyethylene ether in a reactor, heat to 45 °C, and stir until homogeneous to obtain solution one. Take 1.5 g of dodecylbenzenesulfonic acid and 0.8 g of octylphenol polyoxyethylene ether and dissolve them in 150 mL of deionized water. Then add 41.5 g of octamethylcyclotetrasiloxane, 8.5 g of tetraethyl orthosilicate, and 26.6 g of γ-methacryloyloxypropyltrimethoxysilane and mix until homogeneous to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 2 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 9 using a 3% sodium hydroxide aqueous solution, and heat to 80℃ to obtain solution 3. S5. Take 5g of double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and 20mL of deionized water. Then, simultaneously add 11.7g of isopentenyl polyoxyethylene ether, 0.41g of ethylene glycol dimethacrylate, 0.19g of dodecyl mercaptan, 6.6g of acrylic acid, and 0.12g of potassium persulfate aqueous solution (10% by mass) as an initiator. The addition time is 3.5h, and the temperature is controlled at 60℃. After the addition is completed, the mixture is placed at 80℃ for 5h. After the reaction is completed, the mixture is centrifuged, washed, and dried to prepare coated limestone. S6. Take 10 mL of phosphoric acid, 10 mL of triethanolamine and 8 mL of deionized water into a reactor, add 3.5 g of aluminum hydroxide in portions, stir evenly and react at room temperature for 24 h, then add 4.2 g of coated limestone, continue stirring and react for 2.5 h, then let stand and react for 5 h, then add 7% calcium hydroxide by mass, mix and stir evenly to prepare modified limestone.

[0020] Example 3 A method for preparing modified limestone, comprising the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Take 90 mL of ethanol, 10 mL of deionized water, 1.2 mL of glacial acetic acid, 5 g of pretreated limestone, 0.06 g of hydroquinone and 2.8 mL of γ-methacryloyloxypropyltrimethoxysilane into a reactor, disperse them evenly by ultrasonication, react them at 80 °C for 24 h, then cool to room temperature, centrifuge, wash and dry to prepare double-bonded limestone; S3. Take 200 mL of deionized water, 1.8 g of dodecylbenzenesulfonic acid, and 0.9 g of octylphenol polyoxyethylene ether in a reactor, heat to 45 °C, and stir until homogeneous to obtain solution one. Take 1.5 g of dodecylbenzenesulfonic acid and 0.8 g of octylphenol polyoxyethylene ether and dissolve them in 150 mL of deionized water. Then add 41.5 g of octamethylcyclotetrasiloxane, 8.5 g of tetraethyl orthosilicate, and 31.2 g of γ-methacryloyloxypropyltrimethoxysilane and mix until homogeneous to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 3 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 10 using a 3% sodium hydroxide aqueous solution, and heat to 85℃ to obtain solution 3. S5. Take 5g of double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and 20mL of deionized water. Then, simultaneously add 13.2g of isopentenyl polyoxyethylene ether, 0.44g of ethylene glycol dimethacrylate, 0.21g of dodecyl mercaptan, 7.1g of acrylic acid, and 0.15g of potassium persulfate aqueous solution (10% by mass) as an initiator. The addition time is 4h, and the temperature is controlled at 65℃. After the addition is completed, the mixture is placed at 75℃ for 6h. After the reaction is completed, the mixture is centrifuged, washed, and dried to prepare coated limestone. S6. Take 10 mL of phosphoric acid, 12 mL of triethanolamine and 10 mL of deionized water into a reactor, add 3.8 g of aluminum hydroxide in portions, stir evenly and react at room temperature for 24 h, then add 5 g of coated limestone, continue stirring and react for 3 h, then let stand and react for 6 h, then add 8% calcium hydroxide by mass, mix and stir evenly to prepare modified limestone.

[0021] Example 4 A concrete comprises the following raw materials in parts by weight: 325 parts of P·O42.5 grade ordinary Portland cement, 57 parts of silica fume (loss on ignition 4%), 90 parts of fly ash (Class F, Grade I), 310 parts of fine aggregate (river sand with a fineness modulus of 2.5), 145 parts of quartz sand, 66 parts of modified limestone prepared in Example 1, 4.5 parts of polycarboxylate superplasticizer, and 150 parts of water; The above-mentioned concrete preparation method includes the following steps: weigh each raw material according to the weight parts, add cement, silica fume, fine aggregate, quartz sand and modified limestone into a mixer, mix and then add water, fly ash and water-reducing agent, mix evenly, and prepare concrete.

[0022] Example 5 A concrete comprises the following raw materials in parts by weight: 400 parts of P·O42.5 grade ordinary Portland cement, 88 parts of silica fume (loss on ignition 4%), 120 parts of fly ash (Class F, Grade I), 400 parts of fine aggregate (river sand with a fineness modulus of 2.5), 180 parts of quartz sand, 86 parts of modified limestone prepared in Example 2, 7.1 parts of polycarboxylate superplasticizer, and 200 parts of water; The method for preparing the concrete described above is the same as in Example 4.

[0023] Example 6 A concrete comprises the following raw materials in parts by weight: 440 parts of P·O42.5 grade ordinary Portland cement, 115 parts of silica fume (loss on ignition 4%), 147 parts of fly ash (Class F, Grade I), 445 parts of fine aggregate (river sand with a fineness modulus of 2.5), 216 parts of quartz sand, 97 parts of modified limestone prepared in Example 3, 9.2 parts of polycarboxylate superplasticizer, and 250 parts of water; The method for preparing the concrete described above is the same as in Example 4.

[0024] Comparative Example 1: A method for preparing modified limestone, comprising the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Take 90 mL of ethanol, 10 mL of deionized water, 1.2 mL of glacial acetic acid, 5 g of pretreated limestone, 0.06 g of hydroquinone and 2.8 mL of γ-methacryloyloxypropyltrimethoxysilane into a reactor, disperse them evenly by ultrasonication, react them at 80 °C for 24 h, then cool to room temperature, centrifuge, wash and dry to prepare double-bonded limestone; S3. Take 200 mL of deionized water, 1.8 g of dodecylbenzenesulfonic acid, and 0.9 g of octylphenol polyoxyethylene ether in a reactor, heat to 45 °C, and stir until homogeneous to obtain solution one. Take 1.5 g of dodecylbenzenesulfonic acid and 0.8 g of octylphenol polyoxyethylene ether and dissolve them in 150 mL of deionized water. Then add 41.5 g of octamethylcyclotetrasiloxane, 8.5 g of tetraethyl orthosilicate, and 31.2 g of γ-methacryloyloxypropyltrimethoxysilane and mix until homogeneous to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 3 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 10 using a 3% sodium hydroxide aqueous solution, and heat to 85℃ to obtain solution 3. S5. Take 5g of double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and 20mL of deionized water. Then, simultaneously add 13.2g of isopentenyl alcohol polyoxyethylene ether, 0.44g of ethylene glycol dimethacrylate, 0.21g of dodecyl mercaptan, 7.1g of acrylic acid, and 0.15g of potassium persulfate aqueous solution (10% by mass) as an initiator. The addition time is 4h, and the temperature is controlled at 65℃. After the addition is completed, the mixture is placed at 75℃ for 6h. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain modified limestone.

[0025] Comparative Example 2: A method for preparing modified limestone, comprising the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Take 90 mL of ethanol, 10 mL of deionized water, 1.2 mL of glacial acetic acid, 5 g of pretreated limestone, 0.06 g of hydroquinone and 2.8 mL of γ-methacryloyloxypropyltrimethoxysilane into a reactor, disperse them evenly by ultrasonication, react them at 80 °C for 24 h, then cool to room temperature, centrifuge, wash and dry to prepare double-bonded limestone; S3. Take 200 mL of deionized water, 1.8 g of dodecylbenzenesulfonic acid and 0.9 g of octylphenol polyoxyethylene ether into a reactor, heat to 45 °C and stir to mix evenly to obtain solution one; S4. Take 5g of double-bonded limestone and ultrasonically disperse it in a mixed solution of solution one and 20mL of deionized water. Then, simultaneously add 13.2g of isopentenyl polyoxyethylene ether, 0.44g of ethylene glycol dimethacrylate, 0.21g of dodecyl mercaptan, 7.1g of acrylic acid, and 0.15g of potassium persulfate aqueous solution (10% by mass) as initiator. The addition time is 4h, and the temperature is controlled at 65℃. After the addition is completed, the mixture is placed at 75℃ for 6h. After the reaction is completed, the mixture is centrifuged, washed, and dried to prepare coated limestone. S5. Take 10 mL of phosphoric acid, 12 mL of triethanolamine and 10 mL of deionized water into a reactor, add 3.8 g of aluminum hydroxide in portions, stir evenly and react at room temperature for 24 h, then add 5 g of coated limestone, continue stirring and react for 3 h, then let stand and react for 6 h, then add 8% calcium hydroxide by mass, mix and stir evenly to prepare modified limestone.

[0026] Comparative Example 3: A type of concrete comprises the following raw materials in parts by weight: 440 parts of P·O42.5 grade ordinary Portland cement, 115 parts of silica fume (loss on ignition 4%), 147 parts of fly ash (Class F, Grade I), 445 parts of fine aggregate (river sand with a fineness modulus of 2.5), 216 parts of quartz sand, 97 parts of modified limestone prepared in Comparative Example 1, 9.2 parts of polycarboxylate superplasticizer, and 250 parts of water; The method for preparing the concrete described above is the same as in Example 4.

[0027] Comparative Example 4: A type of concrete comprises the following raw materials in parts by weight: 440 parts of P·O42.5 grade ordinary Portland cement, 115 parts of silica fume (loss on ignition 4%), 147 parts of fly ash (Class F, Grade I), 445 parts of fine aggregate (river sand with a fineness modulus of 2.5), 216 parts of quartz sand, 97 parts of modified limestone prepared in Comparative Example 2, 9.2 parts of polycarboxylate superplasticizer, and 250 parts of water; The method for preparing the concrete described above is the same as in Example 4.

[0028] Comparative Example 5: A type of concrete comprises the following raw materials in parts by weight: 440 parts of P·O42.5 grade ordinary Portland cement, 115 parts of silica fume (loss on ignition 4%), 147 parts of fly ash (Class F, Grade I), 445 parts of fine aggregate (river sand with a fineness modulus of 2.5), 216 parts of quartz sand, 97 parts of pretreated limestone prepared in Example 1, 9.2 parts of polycarboxylate superplasticizer, and 250 parts of water; The method for preparing the concrete described above is the same as in Example 4.

[0029] Performance testing The concrete prepared in Examples 4-6 and Comparative Examples 3-5 were subjected to performance testing: (1) Flowability test: The slump (difference between the height of the cylinder and the highest point of the mixture) was measured according to GB / T 50080-2016 standard to evaluate the flowability of concrete. The data results are shown in Table 1.

[0030] (2) Compressive strength test: Using a YES-2000 compression testing machine with a loading rate of 0.5 mm / min, test specimens aged 7d, 14d, and 28d and record the failure load. The data results are shown in Table 1.

[0031] (3) Permeability test: According to GB / T 50082-2024 standard, the water seepage height method was used. Cylindrical specimens aged 28d and 56d were equipped with a permeability tester. The pressure was increased by 0.1MPa every 8 hours starting from 0.1MPa. After water seepage, the pressure was stopped. The specimen was split open and the water seepage height at 10 points was measured and the average value was taken. The data results are shown in Table 1.

[0032] Table 1 Sample performance test results As can be seen from the data in Table 1, the concrete samples prepared in Examples 4-6 of this invention exhibit higher compressive strength and durability, as well as better impermeability and fluidity compared to Comparative Examples 3-5. In Comparative Example 3, the modified limestone component did not contain phosphoric acid, triethanolamine, aluminum hydroxide, and calcium hydroxide. Its measured fluidity and compressive strength were significantly lower than those of Examples 4-6, and its impermeability was slightly lower. This indicates that the introduction of phosphoric acid, triethanolamine, aluminum hydroxide, and calcium hydroxide can improve the material's fluidity, compressive strength, and impermeability. In Comparative Example 4, the modified limestone component did not contain solution II. Its measured water penetration height and compressive strength were significantly lower than those of Examples 4-6. This is because the organosilicon monomers octamethylcyclotetrasiloxane, tetraethyl orthosilicate, and γ-methacryloyloxypropyltrimethoxy The introduction of silanes facilitates the formation of hydrophobic organosiloxane long chains and rigid silica networks, improving impermeability. Furthermore, the introduced Si-OH groups can undergo condensation reactions with the P-OH groups in the aluminophosphate network, optimizing the pore structure and enhancing the compressive strength and durability of the material. In Comparative Example 5, the modified limestone was replaced with an equal amount of pretreated limestone without modification. The measured flow properties, compressive strength, and impermeability were significantly lower than those in Examples 4-6, indicating that the addition of modified limestone greatly improves the flow properties, impermeability, compressive strength, and durability of the material to a certain extent.

[0033] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing modified limestone, characterized in that, Includes the following steps: S1. The limestone is dried until the moisture content is less than 0.5%, and then the dried limestone is ball-milled to prepare pretreated limestone. S2. Ethanol, deionized water, glacial acetic acid, pretreated limestone, hydroquinone and γ-methacryloyloxypropyltrimethoxysilane were placed in a reactor, ultrasonically dispersed evenly, and reacted at 70~85℃ for 20~24h. Then, the mixture was cooled to room temperature, centrifuged, washed and dried to prepare double-bonded limestone. S3. Take deionized water, dodecylbenzenesulfonic acid and octylphenol polyoxyethylene ether in a reactor, heat to 40~50℃ and stir to mix evenly to obtain solution one. Take dodecylbenzenesulfonic acid and octylphenol polyoxyethylene ether and dissolve them in deionized water. Then add octamethylcyclotetrasiloxane, tetraethyl orthosilicate and γ-methacryloyloxypropyltrimethoxysilane and mix evenly to obtain solution two. S4. Slowly add solution 2 dropwise to solution 1. After the addition is complete, react for 2-3 hours. After the reaction is complete, cool to room temperature, adjust the pH of the system to 8-10 using sodium hydroxide aqueous solution, and heat to 75-85℃ to obtain solution 3. S5. Take double-bonded limestone and ultrasonically disperse it in a mixed solution of solution 3 and deionized water. Then, add isopentenyl alcohol polyoxyethylene ether, ethylene glycol dimethacrylate, dodecyl mercaptan, acrylic acid and initiator dropwise. The dropwise addition time is 3-4 hours, and the temperature is controlled at 55-65℃. After the dropwise addition is completed, place it at 75-85℃ for 5-6 hours to react. After the reaction is completed, centrifuge, wash and dry to prepare coated limestone. S6. Take phosphoric acid, triethanolamine and deionized water into a reactor, add aluminum hydroxide in portions, stir evenly and react at room temperature for 20-24 hours, then add coated limestone, continue stirring and react for 2-3 hours, then let stand and react for 5-6 hours, then add calcium hydroxide with a mass fraction of 6-8%, mix and stir evenly to prepare modified limestone.

2. The method for preparing modified limestone according to claim 1, characterized in that, The pretreated limestone has a particle size of 2~8µm.

3. The method for preparing modified limestone according to claim 1, characterized in that, The addition ratio of ethanol, deionized water, glacial acetic acid, pretreated limestone, hydroquinone, and γ-methacryloyloxypropyltrimethoxysilane is 80~100mL: 5~15mL: 1~1.5mL: 5g: 0.05~0.07g: 2.5~3mL.

4. The method for preparing modified limestone according to claim 1, characterized in that, The mass ratio of octamethylcyclotetrasiloxane, tetraethyl orthosilicate, γ-methacryloyloxypropyltrimethoxysilane, isopentenyl alcohol polyoxyethylene ether, acrylic acid, ethylene glycol dimethacrylate, and dodecyl mercaptan is 41.5:8.5:25.2~31.5:10.8~13.5:5.7~7.1:0.36~0.45:0.18~0.

22.

5. The method for preparing modified limestone according to claim 1, characterized in that, The initiator is either ammonium persulfate or potassium persulfate.

6. The method for preparing modified limestone according to claim 1, characterized in that, The addition ratio of phosphoric acid, triethanolamine, deionized water, aluminum hydroxide and coated limestone is 10mL:8~12mL:7~10mL:3~4g:3~5g.

7. A modified limestone, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. An application of the modified limestone according to claim 7 in concrete.

9. The application according to claim 8, characterized in that, The concrete comprises the following raw materials in parts by weight: 320-450 parts cement, 50-120 parts silica fume, 85-150 parts fly ash, 300-450 parts fine aggregate, 140-220 parts quartz sand, 60-100 parts modified limestone, 4-10 parts water-reducing agent, and 140-260 parts water. The preparation method includes the following steps: weigh each raw material according to the weight parts, add cement, silica fume, fine aggregate, quartz sand and modified limestone into a mixer, mix and then add water, fly ash and water-reducing agent, mix evenly, and prepare concrete.

10. The application according to claim 9, characterized in that, The cement is either P·O42.5 grade ordinary Portland cement or P·O52.5 grade ordinary Portland cement; the fine aggregate is river sand with a fineness modulus between 2.4 and 2.8; the water-reducing agent is either polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, or sulfonate-based water-reducing agent; and the quartz sand has a particle size of 100-210µm.

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