Anti-cracking and anti-hollowing building concrete and preparation method thereof

Abstract

This invention relates to the field of concrete technology and discloses a crack-resistant and anti-hollow concrete and its preparation method. The concrete, by weight, comprises 350-380 parts cement, 65-85 parts fly ash, 40-50 parts slag powder, 280-300 parts coarse aggregate, 220-260 parts fine aggregate, 2-4 parts basalt chopped fibers, 1-3 parts modified nano-calcium carbonate, 2-3 parts quaternary ammonium salt modified POSS, 1-2 parts polycarboxylate superplasticizer, and 95-110 parts water. This invention utilizes basalt fibers to construct a crack-resistant network, modified nano-calcium carbonate to refine the matrix pores, and quaternary ammonium salt modified POSS to enhance interfacial bonding and system compatibility. The synergistic effect of these three components significantly reduces concrete drying shrinkage, improves tensile strength and interfacial bonding performance, and effectively solves the problems of concrete cracking and hollowness.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a crack-resistant and hollow-resistant building concrete and its preparation method. Background Technology

[0002] Concrete, as the most widely used inorganic cementitious composite material in civil engineering, boasts core advantages such as readily available raw materials, high plasticity, stable mechanical properties, and excellent durability. It is widely applied in all aspects of construction in industrial and civil buildings, including floor leveling, wall plastering, structural beam and column casting, flooring projects, and secondary structure construction, making it an indispensable core material for modern building engineering. However, existing ordinary concrete has significant drawbacks in practical applications: First, it is prone to drying shrinkage and thermal shrinkage deformation during the hardening process, leading to internal stress concentration and surface and deep cracking, reducing structural strength and durability. Second, the interfacial adhesion between concrete and the base wall and floor is insufficient, making it susceptible to hollowing and detachment due to changes in environmental temperature and humidity, which not only affects the building's appearance but also poses serious safety hazards.

[0003] Currently, the industry often improves concrete performance by adding fibers or water-reducing agents alone. However, the effect of single modification methods is limited and cannot simultaneously achieve both crack resistance and interfacial bonding performance. Moreover, some modified concretes have unreasonable mix proportions, resulting in excessive heat of hydration and large shrinkage rates, which still cannot solve the problems of cracking and hollowing. Therefore, developing a building concrete with both excellent crack resistance and low hollowing rate has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a crack-resistant and anti-hollow concrete for building concrete and its preparation method, which has good mechanical properties and anti-cracking and anti-hollow effects.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a crack-resistant and anti-hollow-out building concrete, comprising the following weight components: 350-380 parts by weight of cement, 65-85 parts by weight of fly ash, 40-50 parts by weight of slag powder, 280-300 parts by weight of coarse aggregate, 220-260 parts by weight of fine aggregate, 2-4 parts by weight of basalt chopped fibers, 1-3 parts by weight of modified nano-calcium carbonate, 2-3 parts by weight of quaternary ammonium salt modified POSS, 1-2 parts by weight of polycarboxylate superplasticizer, and 95-110 parts by weight of water.

[0006] Furthermore, the preparation method of the quaternary ammonium salt modified POSS is as follows: S1. 1,4-dichlorobenzyl and tert-butyl (2-(dimethylamino)ethyl)carbamate were added to a reaction flask containing isopropanol and refluxed at 80-85°C. After the reaction was completed, the mixture was concentrated, washed with petroleum ether, and the crude product was purified by recrystallization in ethanol. Then, the product was added to dichloromethane, and trifluoroacetic acid was added dropwise. The mixture was reacted at room temperature for 2-3 hours. After the reaction was completed, the solvent was removed by concentration, and the product was purified in ethanol to obtain amino quaternary ammonium salt intermediate 1. S2. Add amino quaternary ammonium salt intermediate 1 and acryloyl chloride to N,N-dimethylformamide solvent, stir and mix, add triethylamine catalyst, react at room temperature for 2-3 h, after which distill under reduced pressure, wash, and obtain alkenyl quaternary ammonium salt intermediate 2. S3. Add vinyl POSS, alkenyl quaternary ammonium salt intermediate 2, hydroxypropyl acrylate, and acrylic acid to a reaction flask containing ethyl acetate, stir and mix, purge with nitrogen for protection, reflux at 110-120℃ for 20-30 min, keep the temperature constant, continue to add benzoyl peroxide dissolved in ethyl acetate, keep the reaction at the temperature, cool to room temperature after the reaction is completed, add the reaction solution to cold methanol to precipitate, let stand to separate the layers, remove the upper clear liquid, wash the lower product with methanol 2-3 times, remove the solvent by vacuum distillation, and obtain quaternary ammonium salt modified POSS.

[0007] Further, in S1, the ratio of 1,4-dichlorobenzyl, tert-butyl (2-(dimethylamino)ethyl)carbamate, and trifluoroacetic acid is 4-6 mmol: 8-13 mmol: 65-75 mmol.

[0008] Furthermore, in S1, the reflux reaction time is 14-16 hours.

[0009] Furthermore, in S2, the ratio of aminoquaternary ammonium salt intermediate 1, acryloyl chloride, and triethylamine catalyst is 3-4 mmol: 6-8 mmol: 0.01-0.012 g.

[0010] Further, in S3, the ratio of vinyl POSS, alkenyl quaternary ammonium salt intermediate 2, hydroxypropyl acrylate, acrylic acid, and benzoyl peroxide is 2.2-2.6g: 0.8-1.2mmol: 0.3-0.5g: 0.2-0.4g, 0.02-0.03g.

[0011] Furthermore, in S3, the heat preservation reaction time is 2-3 hours.

[0012] Furthermore, the preparation method of the crack-resistant and hollow-resistant building concrete is as follows: cement, fly ash, slag powder, coarse aggregate, fine aggregate, basalt short fiber, modified nano calcium carbonate, quaternary ammonium salt modified POSS, polycarboxylate superplasticizer, and water are added to a mixer and mixed for 2-3 minutes to obtain crack-resistant and hollow-resistant building concrete.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: This invention utilizes nano-calcium carbonate modified with a composite of lauric acid, sodium stearate, and palmitic acid, with long-chain alkyl hydrophobic groups and carboxylic acid hydrophilic groups grafted onto its surface. This solves the problem of easy agglomeration in ordinary nano-calcium carbonate. The modified nano-calcium carbonate can fill the micropores and mesopores between the CSH gels in cement hydration, refine the pore structure, reduce porosity, improve the density of the matrix, reduce capillary shrinkage stress during hardening, and reduce drying shrinkage deformation. In addition, the surface modification groups can reduce the surface energy of the powder, achieve uniform dispersion, avoid agglomeration and the formation of internal defects, and synergistically improve the compressive and tensile strength of concrete and enhance the crack resistance and bearing capacity of the matrix.

[0014] The quaternary ammonium salt modified POSS of this invention is an organic-inorganic hybrid nanomaterial. Its molecular structure comprises a cage-like inorganic Si-O-Si framework, quaternary ammonium salt cationic groups, hydroxyl, carboxyl, and ester groups, forming a variety of functional groups. It is a key component for achieving crack resistance and anti-cavitation properties in concrete. The inorganic POSS cage-like framework possesses ultra-high rigidity; after embedding into the cement matrix, it can withstand stress, hinder microcrack propagation, and improve the matrix's fracture toughness and deformation resistance. The quaternary ammonium salt cationic groups can be adsorbed onto the surfaces of cement particles, fibers, and aggregates through electrostatic interactions, reducing interphase interfacial tension and solving the problems of basalt fiber entanglement and nanoparticle agglomeration. The hydroxyl and carboxyl polar groups can form strong hydrogen bonds and chemical coordination bonds with cement hydration products and the surface of the building substrate, improving the interfacial bond strength between concrete and the substrate and reducing interfacial debonding and delamination problems. Simultaneously, the polar groups can regulate the cement hydration rate, making the hydration products denser and reducing shrinkage, thus achieving both crack resistance and anti-cavitation properties. Basalt short-cut fibers, modified nano-calcium carbonate, and quaternary ammonium salt-modified POSS form a synergistic system of crack resistance, micro-densification, and interface enhancement. Basalt fibers construct a three-dimensional network skeleton to achieve stress dispersion and crack bridging. Modified nano-calcium carbonate completes micropore filling and hydration optimization, improving matrix density. Quaternary ammonium salt-modified POSS optimizes system compatibility and strengthens interfacial adhesion. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Cement: Ordinary Portland cement with P·O42.5.

[0017] Fly ash: Grade II fly ash.

[0018] Slag powder: S95 grade slag powder.

[0019] Coarse aggregate: 5~20mm continuously graded crushed stone, with needle-like and flaky particle content ≤5% and mud content ≤0.5%.

[0020] Fine aggregate: medium sand, fineness modulus 2.6~3.0, mud content ≤1.0%.

[0021] Basalt short-cut fibers: 10mm in length.

[0022] Polycarboxylate superplasticizer: water reduction rate ≥25%.

[0023] Vinyl POSS (purity ≥95%): Industrial grade, Hubei Jusheng Technology.

[0024] Preparation of modified nano-calcium carbonate: 2.6 g of Ca(OH)₂ was placed in a high-gravity micro-interface reactor. The circulation pump and cooling device were turned on. When the reaction temperature reached 25℃, the CO₂ gas flow meter was turned on and the volumetric flow rate was set to 3 m³ / g. 3 The reaction was stopped when the pH reached the endpoint of 7. The flow meter and circulation pump were then turned off to obtain nano-calcium carbonate. 0.016 g of lauric acid, 0.023 g of sodium stearate, and 0.025 g of palmitic acid were added to 12 mL of ethanol solvent and sonicated for 10 min. The mixture was then thoroughly mixed to obtain a homogeneous solution. The homogeneous solution was then added to 1.2 g of nano-calcium carbonate and reacted at 68 °C. After the reaction was completed, the mixture was filtered and dried in an oven to obtain modified nano-calcium carbonate.

[0025] Example 1 A type of crack-resistant and anti-hollow concrete for building concrete comprises the following components by weight: 380 parts by weight of cement, 85 parts by weight of fly ash, 50 parts by weight of slag powder, 300 parts by weight of coarse aggregate, 260 parts by weight of fine aggregate, 4 parts by weight of basalt chopped fiber, 3 parts by weight of modified nano-calcium carbonate, 3 parts by weight of quaternary ammonium salt modified POSS, 2 parts by weight of polycarboxylate superplasticizer, and 110 parts by weight of water.

[0026] The preparation method of the quaternary ammonium salt modified POSS is as follows: S1. 6 mmol of 1,4-dichlorobenzyl and 13 mmol of tert-butyl (2-(dimethylamino)ethyl)carbamate were added to a reaction flask containing 65 mL of isopropanol and refluxed at 85 °C for 16 h. After the reaction was completed, the mixture was concentrated, washed with petroleum ether, and the crude product was purified by recrystallization in ethanol. Then, the product was added to dichloromethane, and 75 mmol of trifluoroacetic acid was added dropwise. The mixture was reacted at room temperature for 3 h. After the reaction was completed, the solvent was removed by concentration, and the product was purified in ethanol to obtain amino quaternary ammonium salt intermediate 1. S2. Add 4 mmol of amino quaternary ammonium salt intermediate 1 and 8 mmol of acryloyl chloride to 60 mL of N,N-dimethylformamide solvent, stir and mix, add 0.012 g of triethylamine catalyst, react at room temperature for 3 h, after which distill under reduced pressure, wash, and obtain alkenyl quaternary ammonium salt intermediate 2. S3. Add 2.6 g vinyl POSS, 1.2 mmol alkenyl quaternary ammonium salt intermediate 2, 0.5 g hydroxypropyl acrylate, and 0.4 g acrylic acid to a reaction flask containing 40 mL ethyl acetate, stir and mix, purge with nitrogen for protection, reflux at 120 °C for 30 min, keep the temperature constant, continue to add 0.03 g benzoyl peroxide dissolved in 10 mL ethyl acetate, keep the reaction at this temperature for 3 h, cool to room temperature after the reaction is completed, add the reaction solution to cold methanol to precipitate, allow to stand and separate into layers, remove the supernatant, wash the lower product three times with methanol, remove the solvent by vacuum distillation, and obtain quaternary ammonium salt modified POSS.

[0027] The preparation method of crack-resistant and hollow-resistant building concrete is as follows: cement, fly ash, slag powder, coarse aggregate, fine aggregate, basalt short fiber, modified nano calcium carbonate, quaternary ammonium salt modified POSS, polycarboxylate superplasticizer, and water are added to a mixer and mixed for 3 minutes to obtain crack-resistant and hollow-resistant building concrete.

[0028] Example 2 A type of crack-resistant and anti-hollow concrete for building concrete comprises the following components by weight: 350 parts by weight of cement, 65 parts by weight of fly ash, 40 parts by weight of slag powder, 280 parts by weight of coarse aggregate, 220 parts by weight of fine aggregate, 2 parts by weight of basalt chopped fiber, 1 part by weight of modified nano-calcium carbonate, 2 parts by weight of quaternary ammonium salt modified POSS, 1 part by weight of polycarboxylate superplasticizer, and 95 parts by weight of water.

[0029] The preparation method of the quaternary ammonium salt modified POSS is as follows: S1. 4 mmol of 1,4-dichlorobenzyl and 8 mmol of tert-butyl (2-(dimethylamino)ethyl)carbamate were added to a reaction flask containing 55 mL of isopropanol and refluxed at 80 °C for 14 h. After the reaction was completed, the mixture was concentrated, washed with petroleum ether, and the crude product was purified by recrystallization in ethanol. Then, the product was added to dichloromethane, and 65 mmol of trifluoroacetic acid was added dropwise. The mixture was reacted at room temperature for 2 h. After the reaction was completed, the solvent was removed by concentration, and the product was purified in ethanol to obtain amino quaternary ammonium salt intermediate 1. S2. Add 3 mmol of amino quaternary ammonium salt intermediate 1 and 6 mmol of acryloyl chloride to 50 mL of N,N-dimethylformamide solvent, stir and mix, add 0.01 g of triethylamine catalyst, react at room temperature for 2 h, after which distill under reduced pressure and wash to obtain alkenyl quaternary ammonium salt intermediate 2. S3. Add 2.2g vinyl POSS, 0.8mmol alkenyl quaternary ammonium salt intermediate 2, 0.3g hydroxypropyl acrylate, and 0.2g acrylic acid to a reaction flask containing 35mL ethyl acetate, stir and mix, purge with nitrogen for protection, reflux at 110℃ for 20min, keep the temperature constant, continue to add 0.02g benzoyl peroxide dissolved in 5mL ethyl acetate, keep the reaction at this temperature for 2h, cool to room temperature after the reaction is completed, add the reaction solution to cold methanol to precipitate, allow to stand and separate into layers, remove the supernatant, wash the lower product twice with methanol, remove the solvent by vacuum distillation, and obtain quaternary ammonium salt modified POSS.

[0030] The preparation method of crack-resistant and hollow-resistant building concrete is as follows: cement, fly ash, slag powder, coarse aggregate, fine aggregate, basalt short fiber, modified nano calcium carbonate, quaternary ammonium salt modified POSS, polycarboxylate superplasticizer, and water are added to a mixer and mixed for 2 minutes to obtain crack-resistant and hollow-resistant building concrete.

[0031] Example 3 A type of crack-resistant and anti-hollow concrete for building concrete comprises the following weight components: 365 parts by weight of cement, 75 parts by weight of fly ash, 45 parts by weight of slag powder, 290 parts by weight of coarse aggregate, 240 parts by weight of fine aggregate, 3 parts by weight of basalt chopped fibers, 2 parts by weight of modified nano-calcium carbonate, 2.5 parts by weight of quaternary ammonium salt modified POSS, 1.5 parts by weight of polycarboxylate superplasticizer, and 100 parts by weight of water.

[0032] The preparation method of the quaternary ammonium salt modified POSS is as follows: S1. 5 mmol of 1,4-dichlorobenzyl and 10 mmol of tert-butyl (2-(dimethylamino)ethyl)carbamate were added to a reaction flask containing 60 mL of isopropanol and refluxed at 82 °C for 15 h. After the reaction was completed, the mixture was concentrated, washed with petroleum ether, and the crude product was purified by recrystallization in ethanol. Then, the product was added to dichloromethane, and 70 mmol of trifluoroacetic acid was added dropwise. The mixture was reacted at room temperature for 3 h. After the reaction was completed, the solvent was removed by concentration, and the product was purified in ethanol to obtain amino quaternary ammonium salt intermediate 1. S2. Add 3.5 mmol of amino quaternary ammonium salt intermediate 1 and 7 mmol of acryloyl chloride to 55 mL of N,N-dimethylformamide solvent, stir and mix, add 0.01 g of triethylamine catalyst, react at room temperature for 3 h, after which distill under reduced pressure, wash, and obtain alkenyl quaternary ammonium salt intermediate 2. S3. Add 2.4 g vinyl POSS, 1 mmol alkenyl quaternary ammonium salt intermediate 2, 0.4 g hydroxypropyl acrylate, and 0.3 g acrylic acid to a reaction flask containing 36 mL ethyl acetate, stir and mix, purge with nitrogen for protection, reflux at 115 °C for 25 min, keep the temperature constant, continue to add 0.025 g benzoyl peroxide dissolved in 7 mL ethyl acetate, keep the reaction at this temperature for 2 h, cool to room temperature after the reaction is completed, add the reaction solution to cold methanol to precipitate, allow to stand and separate into layers, remove the supernatant, wash the lower product three times with methanol, remove the solvent by vacuum distillation, and obtain quaternary ammonium salt modified POSS.

[0033] The preparation method of crack-resistant and hollow-resistant building concrete is as follows: cement, fly ash, slag powder, coarse aggregate, fine aggregate, basalt short fiber, modified nano calcium carbonate, quaternary ammonium salt modified POSS, polycarboxylate superplasticizer, and water are added to a mixer and mixed for 2.5 minutes to obtain crack-resistant and hollow-resistant building concrete.

[0034] Comparative Example 1 The main difference between this comparative example and Example 3 is that no basalt short-cut fibers are added, while the other raw material ratios and preparation methods are exactly the same.

[0035] Comparative Example 2 The main difference between this comparative example and Example 3 is that no modified nano-calcium carbonate is added, while the other raw material ratios and preparation methods are exactly the same.

[0036] Comparative Example 3 The main difference between this comparative example and Example 3 is that no quaternary ammonium salt was added to modify POSS, while the other raw material ratios and preparation methods are exactly the same.

[0037] Performance testing methods The concrete mixture specimens prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were subjected to performance tests after standard curing (temperature 20±2℃, relative humidity ≥95%) for 28 days, in accordance with current national standards. The test items and applicable standards are as follows: 1. Compressive strength test: The 28-day compressive strength was tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete"; 2. Splitting tensile strength test: According to GB / T50081-2019, the 28-day splitting tensile strength was tested using cubic specimens; 3. Drying shrinkage test: According to GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", 100mm×100mm×515mm prism specimens were used to test the 28-day drying shrinkage value. 4. Interface bond strength test: The tensile bond strength of the concrete-cement mortar substrate was tested at 28 days using a concrete-cement mortar substrate tensile bond test. 5. Early crack resistance test: According to GB / T50082-2009 plate constraint method, observe the crack initiation for 24 hours and evaluate the crack resistance level (Level I is the best, Level III is the worst). 6. Hollow Area Rate Test: Simulate building floor construction, form a 10㎡ specimen, cure for 28 days, and test by tapping with a hollow hammer. Calculate the hollow area percentage to determine the hollow area rate.

[0038] Table 1: Performance Tests

[0039] Table 1 shows that Comparative Example 1 did not add basalt short-cut fibers. Basalt short-cut fibers are crack-resistant and toughening components of the concrete matrix. They can be uniformly dispersed in the matrix and form a spatial network structure, which can effectively bridge microcracks, disperse internal shrinkage stress and temperature stress, and prevent microcracks from propagating into macroscopic cracks. At the same time, the fibers can improve the toughness and tensile strength of the matrix and reduce drying shrinkage deformation. Without these fibers, the internal stress of the concrete cannot be effectively released, cracks are prone to rapid initiation and propagation, tensile and shrinkage resistance are significantly reduced, and the interfacial deformation resistance decreases, resulting in a significant increase in the hollow rate. Comparative Example 2 did not add modified nano-calcium carbonate. Nanoparticles can fill the tiny pores between cement hydration products, refine the pore structure, improve the density of the matrix, and reduce pore shrinkage deformation. Without modified nano-calcium carbonate, the porosity of the concrete matrix increases, the structure becomes loose, drying shrinkage deformation intensifies, the interfacial transition zone becomes weak, the bonding performance decreases, and ultimately the crack resistance decreases and the hollow problem is aggravated. Comparative Example 3 did not include quaternary ammonium salt-modified POSS. Quaternary ammonium salt-modified POSS is an organic-inorganic hybrid nanomaterial. It can form hydrogen bonds and chemical adsorption with cement hydration products, aggregate surfaces, and the substrate through polar groups, which is key to improving interfacial bond strength and suppressing hollow areas. Without this component, the interfacial transition zone has high porosity and a loose structure, with the concrete and substrate relying solely on physical and mechanical bonding, resulting in extremely low adhesion. Under the action of concrete drying shrinkage, the interface is prone to debonding and delamination, leading to an increase in the hollow area rate and a decrease in anti-hollow performance.

[0040] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A crack and blister resistant construction concrete, characterized by, It comprises the following components by weight: 350-380 parts by weight of cement, 65-85 parts by weight of fly ash, 40-50 parts by weight of slag powder, 280-300 parts by weight of coarse aggregate, 220-260 parts by weight of fine aggregate, 2-4 parts by weight of basalt chopped fiber, 1-3 parts by weight of modified nano-calcium carbonate, 2-3 parts by weight of quaternary ammonium salt modified POSS, 1-2 parts by weight of polycarboxylate superplasticizer, and 95-110 parts by weight of water.

2. The crack and blister resistant architectural concrete according to claim 1, wherein, The preparation method of the quaternary ammonium salt modified POSS is as follows: S1. 1,4-dichlorobenzyl and tert-butyl (2-(dimethylamino)ethyl)carbamate were added to a reaction flask containing isopropanol and refluxed at 80-85°C. After the reaction was completed, the mixture was concentrated, washed with petroleum ether, and the crude product was purified by recrystallization in ethanol. Then, the product was added to dichloromethane, and trifluoroacetic acid was added dropwise. The mixture was reacted at room temperature for 2-3 hours. After the reaction was completed, the solvent was removed by concentration, and the product was purified in ethanol to obtain amino quaternary ammonium salt intermediate 1. S2. Add amino quaternary ammonium salt intermediate 1 and acryloyl chloride to N,N-dimethylformamide solvent, stir and mix, add triethylamine catalyst, react at room temperature for 2-3 h, after which distill under reduced pressure, wash, and obtain alkenyl quaternary ammonium salt intermediate 2. S3. Add vinyl POSS, alkenyl quaternary ammonium salt intermediate 2, hydroxypropyl acrylate, and acrylic acid to a reaction flask containing ethyl acetate, stir and mix, purge with nitrogen for protection, reflux at 110-120℃ for 20-30 min, keep the temperature constant, continue to add benzoyl peroxide dissolved in ethyl acetate, keep the reaction at the temperature, cool to room temperature after the reaction is completed, add the reaction solution to cold methanol to precipitate, let stand to separate the layers, remove the upper clear liquid, wash the lower product with methanol 2-3 times, remove the solvent by vacuum distillation, and obtain quaternary ammonium salt modified POSS.

3. The crack-resistant and hollow-resistant building concrete according to claim 2, characterized in that, In S1, the ratio of 1,4-dichlorobenzyl, tert-butyl (2-(dimethylamino)ethyl)carbamate, and trifluoroacetic acid is 4-6 mmol: 8-13 mmol: 65-75 mmol.

4. The crack-resistant and hollow-resistant building concrete according to claim 2, characterized in that, In S1, the reflux reaction time is 14-16 hours.

5. The crack-resistant and hollow-resistant building concrete according to claim 2, characterized in that, In S2, the ratio of aminoquaternary ammonium salt intermediate 1, acryloyl chloride, and triethylamine catalyst is 3-4 mmol: 6-8 mmol: 0.01-0.012 g.

6. The crack-resistant and hollow-resistant building concrete according to claim 2, characterized in that, In S3, the ratio of vinyl POSS, alkenyl quaternary ammonium salt intermediate 2, hydroxypropyl acrylate, acrylic acid, and benzoyl peroxide is 2.2-2.6g: 0.8-1.2mmol: 0.3-0.5g: 0.2-0.4g, 0.02-0.03g.

7. The crack-resistant and hollow-resistant building concrete according to claim 2, characterized in that, In the S3 process, the heat preservation reaction time is 2-3 hours.

8. A method for preparing crack-resistant and hollow-resistant building concrete as described in any one of claims 1-7, characterized in that, The method for preparing the crack-resistant and hollow-resistant building concrete is as follows: cement, fly ash, slag powder, coarse aggregate, fine aggregate, basalt short fiber, modified nano calcium carbonate, quaternary ammonium salt modified POSS, polycarboxylate superplasticizer, and water are added to a mixer and mixed for 2-3 minutes to obtain crack-resistant and hollow-resistant building concrete.

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