Fiber-reinforced, crack-resistant, impermeable concrete material and method for its production

Abstract

The application discloses a kind of fiber-reinforced anti-cracking impermeable concrete materials and preparation method thereof, belong to concrete processing technical field.The application is used to solve the technical problem that the anti-cracking impermeable performance of concrete material in prior art needs to be further improved, a kind of fiber-reinforced anti-cracking impermeable concrete material includes the following composition by weight parts:80-100 parts of cement, 3-6 parts of modified fiber, 6-12 parts of modified capsule, 250-300 parts of aggregate and 30-50 parts of auxiliary material.The application prepares the modified fiber of surface modification maleimide structure, which is jointly enhanced with the modified capsule of modified epoxy monomer as core material through Diels-Alder reaction concrete material, not only can improve its anti-cracking impermeable performance, but also can improve its mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of concrete processing technology, specifically to a fiber-reinforced crack-resistant and impermeable concrete material and its preparation method. Background Technology

[0002] Concrete, as one of the most widely used structural materials in modern civil engineering, has a decisive impact on structural safety and durability due to its crack resistance and impermeability. With the increasing demands for durability in underground engineering, high-rise buildings, water conservancy facilities, and marine structures, the problems of easy cracking and high permeability in traditional ordinary concrete have become increasingly apparent, prompting crack-resistant and impermeable concrete materials to become a key research and engineering application area. Currently, common methods for improving the crack resistance and impermeability of concrete mainly include inorganic chemical admixture technologies such as expansive agents, water-reducing agents, water-repellent agents, and fine mineral admixtures, as well as fiber reinforcement technology. Among these, fiber reinforcement methods, by introducing high-molecular or inorganic fibers such as steel fibers, polypropylene fibers, basalt fibers, and PVA fibers into concrete, can effectively inhibit the initiation and propagation of microcracks, improving the ductility and crack resistance of concrete.

[0003] While the aforementioned materials and modification methods have improved the crack resistance and impermeability of concrete to some extent, existing technologies still have several limitations. Conventional fibers tend to agglomerate in concrete, resulting in uneven dispersion. Furthermore, some fibers have weak interfacial bonding with the cement matrix, making it difficult to achieve the expected reinforcement effect on concrete. In addition, although adding fibers to concrete can inhibit crack formation in the early stages and improve the tensile and flexural mechanical properties of concrete, it cannot repair existing cracks in concrete. The seepage channels persist, leading to a decrease in the overall impermeability of concrete. Moreover, the impermeability performance of fibers depends on the physical barrier of the fiber structure rather than chemical sealing, resulting in limited long-term service stability.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber-reinforced crack-resistant and impermeable concrete material and its preparation method, in order to solve the technical problem that the crack resistance and impermeability of concrete materials in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a fiber-reinforced crack-resistant and impermeable concrete material, comprising the following components by weight: 80-100 parts cement, 3-6 parts modified fiber, 6-12 parts modified capsule, 250-300 parts aggregate and 30-50 parts auxiliary materials;

[0007] The cement is silicate cement, and the aggregate is composed of coarse aggregate and fine aggregate in a mass ratio of 2-4:3-5. The coarse aggregate is crushed stone of 5-20mm, and the fine aggregate is quartz sand of 1-4mm. The auxiliary materials are composed of water-reducing agent, curing agent and dispersant in a mass ratio of 1-2:2-4:6-8. The water-reducing agent is polycarboxylate water-reducing agent, the curing agent is diethylenetriamine, and the dispersant is water.

[0008] Furthermore, the modified capsule is prepared by the following steps:

[0009] A1. Place urea and formaldehyde aqueous solution in a reaction vessel and stir. Add triethanolamine to adjust the pH to 8-9. Heat the reaction vessel to 65-75℃ and keep it at this temperature for 60-90 minutes to obtain a mixed solution.

[0010] The reaction principle for preparing the mixture is as follows:

[0011] During the reaction, under alkaline heating conditions, the carbonyl carbon of formaldehyde is nucleophilically attacked by the amino group of urea to generate hydroxymethyl urea intermediate. The methyl groups further undergo condensation and dehydration with each other or with other urea molecules to generate cross-linked structures such as C–N–C or C–NH–CH2–NH–C. The system gradually becomes viscous and forms a milky white prepolymer mixture.

[0012] A2. Place the modified epoxy monomer, sodium dodecyl sulfonate and deionized water in a reaction vessel and stir at room temperature for 30-60 min. Add the mixture and stir at room temperature for 15-30 min. Add resorcinol solution and add dilute hydrochloric acid to adjust the pH to 3-4. Heat the reaction vessel to 55-65℃ and keep it at that temperature for 2-4 h. Post-process to obtain the modified capsule precursor.

[0013] The reaction principle for preparing modified capsule precursors is as follows:

[0014] During the reaction, the modified epoxy monomer is stirred in the presence of an emulsifier to form a stable emulsion. Dilute hydrochloric acid is added to adjust the reaction system to be acidic, which promotes further condensation and cross-linking of urea-formaldehyde resin and deposits it at the oil-water interface to form a solid microcapsule structure. Resorcinol acts as a co-crosslinking agent to enhance the rigidity and thermal stability of the urea-formaldehyde resin wall material. Sodium chloride changes the ionic strength of the aqueous phase, which helps the microcapsule structure to form a dense nucleation. The result is a modified capsule precursor with a core material of modified epoxy monomer and a shell of cross-linked urea-formaldehyde resin.

[0015] A3. The modified capsule precursor, 3,3,3-trifluoropropyltriethoxysilane, ethanol and deionized water were placed in a reaction vessel and stirred. The reaction vessel was heated to 45-55℃, and an ammonia solution was added. The reaction was kept at this temperature for 2-4 hours, and the modified capsules were obtained after post-treatment.

[0016] The reaction principle for the preparation of modified capsules is as follows:

[0017] During the reaction, under alkaline conditions, the siloxane bonds of 3,3,3-trifluoropropyltriethoxysilane hydrolyze into silanols, which then undergo a condensation reaction with the hydroxyl groups on the surface of the modified capsule precursor to obtain modified capsules modified with silane coupling agents.

[0018] Further, in step A1, the ratio of urea to formaldehyde aqueous solution is 2-4g:15-20mL, and the concentration of formaldehyde aqueous solution is 37-40wt%; in step A2, the ratio of modified epoxy monomer, sodium dodecyl sulfonate, deionized water, mixed solution, and resorcinol solution is 5-10g:0.5-1.5g:80-120mL:20-25mL:100-120mL, the resorcinol solution is composed of resorcinol, sodium chloride, and deionized water in a ratio of 2-4g:1-2g:80-100mL, the concentration of dilute hydrochloric acid is 0.5-1mol / L, and the post-treatment step includes: after the reaction is completed, waiting for the reaction system to cool to a certain temperature. At room temperature, filter under vacuum. Wash the filter cake 2-4 times with deionized water and ethanol, transfer it to an oven at 50-60℃, and dry it to constant weight to obtain the modified capsule precursor. In step A3, the ratio of the modified capsule precursor, 3,3,3-trifluoropropyltriethoxysilane, ethanol, deionized water, and ammonia solution is 4-6g:1-2g:50-70mL:5-10mL:2-4mL, and the concentration of the ammonia solution is 50-70wt%. The post-processing steps include: after the reaction is completed, wait for the reaction system to cool to room temperature, filter under vacuum, wash the filter cake 2-4 times with deionized water and ethanol, transfer it to an oven at 50-60℃, and dry it to constant weight to obtain the modified capsules.

[0019] Furthermore, the dosage ratio of the modified epoxy monomer is:

[0020] B1. Tris(2-aminoethyl)amine, 5-hydroxyfurfural and ethanol were placed in a reaction vessel and stirred. The reaction vessel was heated to 70-80℃ and kept at this temperature for 2-4 hours. After post-treatment, intermediate I was obtained.

[0021] B2. Place epichlorohydrin, tetrabutylammonium bisulfate and N,N-dimethylformamide in a nitrogen-protected reactor and stir. Slowly add intermediate I. During the addition process, maintain the reaction system temperature at 20-25℃ and keep the reaction at this temperature for 4-6 hours. Add sodium hydroxide aqueous solution and keep the reaction at this temperature for 1-2 hours. Post-treatment yields the modified epoxy monomer.

[0022] The reaction formula for preparing modified epoxy monomers is as follows:

[0023]

[0024] The reaction principle for the preparation of modified epoxy monomers is as follows:

[0025] During the reaction, under heating conditions, the three amino groups of tris(2-aminoethyl)amine undergo condensation reactions with the aldehyde group of 5-hydroxyfurfural to generate intermediate I with an imine structure. Furthermore, the hydroxyl group in 5-hydroxyfurfural forms an alkoxy anion under alkaline conditions, which undergoes a ring-opening reaction with the epoxy group on the epichlorohydrin molecule. After the addition of sodium hydroxide aqueous solution, the terminal –CH2Cl group undergoes further intramolecular cyclization under alkaline conditions to obtain a modified epoxy monomer.

[0026] Further, in step B1, the ratio of tris(2-aminoethyl)amine, 5-hydroxyfurfural, and ethanol is 4-6 g: 2-4 g: 100-120 mL. The post-processing steps include: after the reaction is complete, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with ethanol and deionized water, transferred to an oven at 50-60°C, and dried to constant weight to obtain intermediate I; in step B2, the epichlorohydrin, tetrabutylammonium bisulfate, N,N-dimethylformamide, The ratio of intermediate I to sodium hydroxide aqueous solution is 6-8g:0.2-0.4g:80-100mL:4-6g:100-150mL, and the concentration of sodium hydroxide aqueous solution is 50-60wt%. The post-treatment steps include: after the reaction is completed, adding 80-100mL of diethyl ether, washing 2-4 times, adding deionized water, washing 2-4 times, transferring the organic phase to a rotary evaporator at a temperature of 90-100℃, and evaporating until no liquid is collected to obtain the modified epoxy monomer.

[0027] Furthermore, the modified carbon fiber is prepared by the following steps:

[0028] C1. Place carbon fiber and nitric acid solution in a reaction vessel and stir. Heat the reaction vessel to 65-75℃ and keep it at this temperature for 1-2 hours. Post-treatment yields acidified carbon fiber.

[0029] The reaction principle for preparing acidified carbon fiber is as follows:

[0030] During the reaction, under heating conditions, nitric acid acts as an oxidant, causing the carbon atoms on the surface of the carbon fiber to lose electrons and generate carboxyl groups, thus obtaining acidified carbon fiber.

[0031] C2. Place acidified carbon fiber, 2-aminoterephthalic acid, zirconium tetrachloride and N,N-dimethylformamide in a reaction vessel, heat the reaction vessel to 75-85℃, keep the reaction at this temperature for 6-8 hours, and then process to obtain ammoniated carbon fiber.

[0032] The reaction principle for preparing ammoniated carbon fiber is as follows:

[0033] During the reaction, zirconium tetrachloride hydrolyzes to Zr in N,N-dimethylformamide. 4 The two carboxyl groups in ⁺,2-aminoterephthalic acid and the carboxyl groups on the surface of acidified carbon fibers react with Zr.4 ⁺ Coordination occurs, forming Zr6O4(OH)4(CO2) 12 With a three-dimensional topological structure as the core, under hydrothermal conditions, the metal-organic framework is grown on the surface of carbon fiber, and ammoniated carbon fiber is obtained.

[0034] C3. Place ammoniated carbon fiber and acetone in a reaction vessel and stir. Slowly add maleic anhydride solution and react at room temperature for 1-2 hours. Add sodium acetate, acetic anhydride and triethylamine. Heat the reaction vessel to 55-65℃ and keep it at that temperature for 10-12 hours. Post-treatment yields modified fiber.

[0035] The reaction principle for the preparation of modified fibers is as follows:

[0036] During the reaction, the amino groups of the ammoniated carbon fiber undergo a nucleophilic addition reaction with maleic anhydride. After the addition of sodium acetate, acetic anhydride and triethylamine, the intermediate is further dehydrated and cyclized to form a maleimide structure, thus obtaining the modified fiber.

[0037] Further, in step C1, the ratio of carbon fiber to nitric acid solution is 5-10g:100-150mL, the nitric acid solution is a 50-60wt% aqueous nitric acid solution, and the post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed with deionized water until neutral, transferred to an oven at 90-100℃, and dried to constant weight to obtain acidified carbon fiber;

[0038] Further, in step C2, the ratio of the acidified carbon fiber, 2-aminoterephthalic acid, zirconium tetrachloride and N,N-dimethylformamide is 5-10g:0.5-1g:0.5-1g:150-200mL. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed with ethanol 2-4 times, transferred to an oven at 90-100℃, and dried to constant weight to obtain ammoniated carbon fiber.

[0039] Further, in step C3, the ratio of the ammoniated carbon fiber, acetone, maleic anhydride solution, sodium acetate, acetic anhydride, and triethylamine is 10-15g:50-100mL:40-60mL:0.5-1g:4-6mL:2-4mL. The maleic anhydride solution is a 1-1.5mol / L maleic anhydride-acetone solution. The post-treatment steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water, transferred to an oven at 50-60℃, and dried to constant weight to obtain modified fiber.

[0040] A method for preparing a fiber-reinforced crack-resistant and impermeable concrete material includes the following steps:

[0041] S1. Add cement, aggregate and modified capsules to the mixer and mix for 2-4 minutes to obtain the mixture;

[0042] S2. Add the mixture and auxiliary materials to the mixer, mix at low speed for 1-2 minutes, mix at high speed for 1-2 minutes, add the modified fiber, and mix at high speed for 2-4 minutes to obtain the concrete material.

[0043] The present invention has the following beneficial effects:

[0044] 1. This invention introduces carboxyl groups into carbon fibers through acidification treatment, and further synthesizes a metal-organic framework containing amino groups on the acidified carbon fibers via a hydrothermal method. Further post-synthetic modification of the metal-organic framework yields modified fibers with a maleimide-modified surface. These modified fibers can undergo a Diels-Alder reaction with modified epoxy monomers released from modified capsules at crack locations, generating a stable covalent cross-linked network. This forms a new network structure locally within the crack, effectively sealing the crack and blocking media penetration, restoring the mechanical properties of concrete, and improving the crack resistance and impermeability of concrete materials. After surface functionalization, the roughness of the fiber is significantly increased, which not only improves its dispersibility in concrete but also enhances its mechanical embedding and interfacial bonding with the cement matrix. The rough surface provides more micro-protrusions and pores, which is conducive to the adhesion of cement hydration products and improves the density and stability of the interfacial transition zone. At the same time, the rough structure promotes the effective transfer of stress between the fiber and the matrix, significantly improving the fiber's pull-out resistance and overall crack resistance. Combined with the chemical reactivity of the surface functional groups, a dual reinforcement mechanism of physical embedding and chemical bonding is achieved, effectively improving the mechanical properties and crack resistance and impermeability of concrete.

[0045] 2. This invention prepares modified epoxy monomers through phenolic condensation and epoxy group end-capping. A modified capsule precursor, using polyurea-formaldehyde resin as the wall material and the modified epoxy monomer as the core material, is then prepared via interfacial polymerization. The modified capsule precursor is further modified with a silane coupling agent to obtain modified capsules. These modified capsules can rupture when concrete cracks form, releasing the epoxy monomers. The epoxy monomers react with the curing agent and the maleimide structure on the surface of the modified fibers to form a new reversible cross-linked network structure, thereby sealing the cracks and restoring structural strength, thus improving the crack resistance of the concrete. The modified capsules exhibit improved impermeability and mechanical properties. Furthermore, the trifluoropropyl groups on the exterior of the capsules possess low surface energy and strong hydrophobicity. After modification, the van der Waals forces and polar attraction between capsule particles can be effectively reduced, thereby inhibiting the agglomeration of capsules in the cement system and improving their fluidity and dispersion uniformity in the mixing system. When concrete curing specimens are subjected to external forces, the modified capsules can disperse local stress concentration at the microscale, slowing down the initiation of microcracks. This structure can reduce peak stress before the material cracks, delay crack formation, and improve the crack resistance, impermeability, and mechanical properties of concrete materials. Detailed Implementation

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 are within the scope of protection of the present invention.

[0047] The silicate cement used in this invention is white in color, has a service temperature range of -30 to 156°C, is grade one, and has a content of 100%.

[0048] The crushed stone used in this invention has a specific gravity of 1.7, a porosity of 5.2%, a size of 5-20mm, and a mud content of 0.01%.

[0049] The quartz sand used in this invention has a size of 1-4mm, a hardness of 7.5, and a porosity of 56%.

[0050] The polycarboxylate superplasticizer used in this invention has a solid content of 65%, a pH of 9.2, and a moisture content of 2.45%.

[0051] The carbon fibers used in this invention are 1-3 cm in length, have a carbon content of 99.9-99.99%, and a resistivity of 5·10⁻⁶-13·10⁻⁶ Ω·m.

[0052] Example 1

[0053] This embodiment provides a method for preparing modified fibers for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0054] Step I: Preparation of acidified carbon fibers

[0055] Weigh 50g of carbon fiber and 1000mL of 50wt% nitric acid aqueous solution and place them in a reaction vessel and stir. Heat the reaction vessel to 65℃ and keep it at that temperature for 1h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake with deionized water until neutral, transfer it to an oven at 90℃ and dry it to constant weight to obtain acidified carbon fiber.

[0056] Step II: Preparation of ammoniated carbon fibers

[0057] Weigh out 50g of acidified carbon fiber, 5g of 2-aminoterephthalic acid, 5g of zirconium tetrachloride and 1500mL of N,N-dimethylformamide and place them in a reaction vessel. Heat the reaction vessel to 75℃ and keep it at that temperature for 6 hours. After the reaction is complete, cool the reaction system to room temperature, filter it, wash the filter cake twice with ethanol, transfer it to an oven at 90℃ and dry it to constant weight to obtain ammoniated carbon fiber.

[0058] Step III: Preparation of modified fibers

[0059] Weigh 100g of ammoniated carbon fiber and 500mL of acetone and place them in a reaction vessel and stir. Slowly add 400mL of 1mol / L maleic anhydride acetone solution and react at room temperature for 1h. Add 5g of sodium acetate, 40mL of acetic anhydride and 20mL of triethylamine. Heat the reaction vessel to 55℃ and keep it at that temperature for 10h. After the reaction is complete, cool the reaction system to room temperature, filter, wash the filter cake twice with deionized water, transfer it to an oven at 50℃ and dry it to constant weight to obtain modified fiber.

[0060] Example 2

[0061] This embodiment provides a method for preparing modified fibers for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0062] Step I: Preparation of acidified carbon fibers

[0063] Weigh 70g of carbon fiber and 1250mL of 55wt% nitric acid aqueous solution and place them in a reaction vessel and stir. Heat the reaction vessel to 70℃ and keep it at that temperature for 1.5h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake with deionized water until neutral, transfer it to an oven at 95℃ and dry it to constant weight to obtain acidified carbon fiber.

[0064] Step II: Preparation of ammoniated carbon fibers

[0065] Weigh out 70g of acidified carbon fiber, 7g of 2-aminoterephthalic acid, 7g of zirconium tetrachloride and 1750mL of N,N-dimethylformamide and place them in a reaction vessel. Heat the reaction vessel to 80℃ and keep it at that temperature for 7h. After the reaction is complete, cool the reaction system to room temperature, filter it, wash the filter cake three times with ethanol, transfer it to an oven at 95℃ and dry it to constant weight to obtain ammoniated carbon fiber.

[0066] Step III: Preparation of modified fibers

[0067] Weigh 125g of ammoniated carbon fiber and 700mL of acetone and place them in a reaction vessel and stir. Slowly add 500mL of 1.2mol / L maleic anhydride acetone solution and react at room temperature for 1.5h. Add 7g of sodium acetate, 50mL of acetic anhydride and 30mL of triethylamine. Heat the reaction vessel to 60℃ and keep it at that temperature for 11h. After the reaction is complete, cool the reaction system to room temperature, filter, wash the filter cake three times with deionized water, transfer it to an oven at 55℃ and dry it to constant weight to obtain modified fiber.

[0068] Example 3

[0069] This embodiment provides a method for preparing modified fibers for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0070] Step I: Preparation of acidified carbon fibers

[0071] Weigh 100g of carbon fiber and 1500mL of 60wt% nitric acid aqueous solution and place them in a reaction vessel and stir. Heat the reaction vessel to 75℃ and keep it at that temperature for 2h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake with deionized water until neutral, transfer it to an oven at 100℃ and dry it to constant weight to obtain acidified carbon fiber.

[0072] Step II: Preparation of ammoniated carbon fibers

[0073] Weigh out 100g of acidified carbon fiber, 10g of 2-aminoterephthalic acid, 10g of zirconium tetrachloride and 2000mL of N,N-dimethylformamide and place them in a reaction vessel. Heat the reaction vessel to 85℃ and keep it at that temperature for 8 hours. After the reaction is complete, cool the reaction system to room temperature, filter it, wash the filter cake four times with ethanol, transfer it to an oven at 100℃ and dry it to constant weight to obtain ammoniated carbon fiber.

[0074] Step III: Preparation of modified fibers

[0075] Weigh 150g of ammoniated carbon fiber and 1000mL of acetone and place them in a reaction vessel and stir. Slowly add 600mL of 1.5mol / L maleic anhydride acetone solution and react at room temperature for 2h. Add 10g of sodium acetate, 60mL of acetic anhydride and 40mL of triethylamine. Heat the reaction vessel to 65℃ and keep it at that temperature for 12h. After the reaction is complete, cool the reaction system to room temperature, filter, wash the filter cake 4 times with deionized water, transfer it to an oven at 60℃ and dry it to constant weight to obtain modified fiber.

[0076] Example 4

[0077] This embodiment provides a method for preparing modified epoxy monomers for modified capsules used in fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0078] Step ①: Preparation of intermediate I

[0079] Weigh out 40g of tris(2-aminoethyl)amine, 20g of 5-hydroxyfurfural and 1000mL of ethanol and place them in a reaction vessel and stir. Heat the reaction vessel to 70℃ and keep it at that temperature for 2h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with ethanol and deionized water, transfer it to an oven at 50℃ and dry it to constant weight to obtain intermediate I.

[0080] Step 2: Preparation of modified epoxy monomers

[0081] Weigh 60g of epichlorohydrin, 2g of tetrabutylammonium hydrogen sulfate, and 800mL of N,N-dimethylformamide and place them in a nitrogen-protected reactor. Stir slowly and slowly add 40g of intermediate I. During the addition process, maintain the reaction system temperature at 20℃ and keep the reaction at this temperature for 4 hours. Add 1000mL of 50wt% sodium hydroxide aqueous solution and keep the reaction at this temperature for 1 hour. After the reaction is complete, add 800mL of diethyl ether and wash twice. Add deionized water and wash twice. Transfer the organic phase to a rotary evaporator at 90℃ and evaporate until no liquid is collected to obtain the modified epoxy monomer.

[0082] Example 5

[0083] This embodiment provides a method for preparing modified epoxy monomers for modified capsules used in fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0084] Step ①: Preparation of intermediate I

[0085] Weigh out 50g of tris(2-aminoethyl)amine, 30g of 5-hydroxyfurfural and 1100mL of ethanol and place them in a reaction vessel and stir. Heat the reaction vessel to 75℃ and keep it at that temperature for 3h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with ethanol and deionized water, transfer it to an oven at 55℃ and dry it to constant weight to obtain intermediate I.

[0086] Step 2: Preparation of modified epoxy monomers

[0087] Weigh out 70g of epichlorohydrin, 3g of tetrabutylammonium hydrogen sulfate and 90mL of N,N-dimethylformamide and place them in a reaction vessel under nitrogen atmosphere and stir. Slowly add 50g of intermediate I. During the addition process, maintain the reaction system temperature at 22℃ and keep the reaction at this temperature for 5h. Add 1250mL of 55wt% sodium hydroxide aqueous solution and keep the reaction at this temperature for 1.5h. After the reaction is complete, add 900mL of diethyl ether and wash 3 times. Add deionized water and wash 3 times. Transfer the organic phase to a rotary evaporator at 95℃ and evaporate until no liquid is collected to obtain the modified epoxy monomer.

[0088] Example 6

[0089] This embodiment provides a method for preparing modified epoxy monomers for modified capsules used in fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0090] Step ①: Preparation of intermediate I

[0091] Weigh out 60g of tris(2-aminoethyl)amine, 40g of 5-hydroxyfurfural and 1200mL of ethanol and place them in a reaction vessel and stir. Heat the reaction vessel to 80℃ and keep it at that temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake 4 times with ethanol and deionized water, transfer it to an oven at 60℃ and dry it to constant weight to obtain intermediate I.

[0092] Step 2: Preparation of modified epoxy monomers

[0093] Weigh 80g of epichlorohydrin, 4g of tetrabutylammonium hydrogen sulfate, and 1000mL of N,N-dimethylformamide and place them in a nitrogen-protected reactor. Stir slowly and slowly add 60g of intermediate I. During the addition process, maintain the reaction system temperature at 25℃ and keep the reaction at this temperature for 6 hours. Add 1500mL of 60wt% sodium hydroxide aqueous solution and keep the reaction at this temperature for 2 hours. After the reaction is complete, add 1000mL of diethyl ether and wash 4 times. Add deionized water and wash 4 times. Transfer the organic phase to a rotary evaporator at 100℃ and evaporate until no liquid is collected to obtain the modified epoxy monomer.

[0094] Example 7

[0095] This embodiment provides a method for preparing modified capsules for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0096] Step (1) Preparation of the mixture

[0097] Weigh out 20g of urea and 150mL of 37wt% formaldehyde aqueous solution and place them in a reaction vessel. Stir, add triethanolamine to adjust the pH to 8, heat the reaction vessel to 65℃, and keep it at this temperature for 60min to obtain a mixed solution.

[0098] Step 2: Preparation of modified capsule precursor

[0099] Mix resorcinol, sodium chloride and deionized water in a ratio of 2g:1g:80mL to obtain a resorcinol solution for later use.

[0100] Weigh 50g of the modified epoxy monomer prepared in Example 4, 5g of sodium dodecyl sulfonate, and 800mL of deionized water and place them in a reaction vessel. Stir at room temperature for 30min, add 200mL of the mixture, stir at room temperature for 15min, add 1000mL of resorcinol solution, add dilute hydrochloric acid to adjust the pH to 3, heat the reaction vessel to 55℃, and keep it at this temperature for 2h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake twice with deionized water and ethanol, transfer it to an oven at 50℃, and dry it to constant weight to obtain the modified capsule precursor.

[0101] Step 3: Preparation of modified capsules

[0102] Weigh out 40g of the modified capsule precursor, 10g of 3,3,3-trifluoropropyltriethoxysilane, 500mL of ethanol and 50mL of deionized water and place them in a reaction vessel and stir. Heat the reaction vessel to 45℃, add 50wt% ammonia solution, and keep the reaction at this temperature for 2h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake twice with deionized water and ethanol, transfer it to an oven at 50℃, and dry it to constant weight to obtain the modified capsules.

[0103] Example 8

[0104] This embodiment provides a method for preparing modified capsules for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0105] Step (1) Preparation of the mixture

[0106] Weigh out 30g of urea and 175mL of 38wt% formaldehyde aqueous solution and place them in a reaction vessel. Stir, add triethanolamine to adjust the pH to 8.5, heat the reaction vessel to 70℃, and keep it at this temperature for 70min to obtain a mixed solution.

[0107] Step 2: Preparation of modified capsule precursor

[0108] Mix resorcinol, sodium chloride, and deionized water in a ratio of 3g:1.5g:90mL to obtain a resorcinol solution for later use.

[0109] Weigh out 70g of the modified epoxy monomer prepared in Example 5, 10g of sodium dodecyl sulfonate, and 1000mL of deionized water and place them in a reaction vessel. Stir at room temperature for 45min, add 220mL of the mixture, stir at room temperature for 25min, add 1100mL of resorcinol solution, add dilute hydrochloric acid to adjust the pH to 3.5, heat the reaction vessel to 60℃, and keep it at that temperature for 3h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake three times with deionized water and ethanol, transfer it to an oven at 55℃, and dry it to constant weight to obtain the modified capsule precursor.

[0110] Step 3: Preparation of modified capsules

[0111] Weigh out 50g of the modified capsule precursor, 15g of 3,3,3-trifluoropropyltriethoxysilane, 600mL of ethanol and 700mL of deionized water and place them in a reaction vessel. Stir the vessel and heat it to 50℃. Add 60wt% ammonia solution and keep it at this temperature for 3 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with deionized water and ethanol, transfer it to an oven at 55℃ and dry it to constant weight to obtain the modified capsules.

[0112] Example 9

[0113] This embodiment provides a method for preparing modified capsules for fiber-reinforced crack-resistant and impermeable concrete materials, including the following steps:

[0114] Step (1) Preparation of the mixture

[0115] Weigh out 40g of urea and 200mL of 40wt% formaldehyde aqueous solution and place them in a reaction vessel. Stir, add triethanolamine to adjust the pH to 9, heat the reaction vessel to 75℃, and keep it at this temperature for 90min to obtain a mixed solution.

[0116] Step 2: Preparation of modified capsule precursor

[0117] Mix resorcinol, sodium chloride and deionized water in a ratio of 4g:2g:100mL to obtain a resorcinol solution for later use.

[0118] Weigh 100g of the modified epoxy monomer prepared in Example 6, 15g of sodium dodecyl sulfonate, and 1200mL of deionized water and place them in a reaction vessel. Stir at room temperature for 60min, add 250mL of the mixture, stir at room temperature for 30min, add 1200mL of resorcinol solution, add dilute hydrochloric acid to adjust the pH to 4, heat the reaction vessel to 65℃, and keep the reaction at this temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake 4 times with deionized water and ethanol, transfer it to an oven at 60℃, and dry it to constant weight to obtain the modified capsule precursor.

[0119] Step 3: Preparation of modified capsules

[0120] Weigh out 60g of the modified capsule precursor, 20g of 3,3,3-trifluoropropyltriethoxysilane, 700mL of ethanol and 100mL of deionized water and place them in a reaction vessel. Stir the vessel and heat it to 55℃. Add 70wt% ammonia solution and keep it at this temperature for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake four times with deionized water and ethanol, transfer it to an oven at 60℃ and dry it to constant weight to obtain the modified capsules.

[0121] Example 10

[0122] This embodiment provides a method for preparing fiber-reinforced crack-resistant and impermeable concrete material, including the following steps:

[0123] Mix 5mm crushed stone and 1mm quartz sand evenly at a mass ratio of 2:3 to obtain aggregate, and set aside for later use;

[0124] Polycarboxylate superplasticizer, diethylenetriamine and water are mixed evenly at a mass ratio of 1:2:6 to obtain the auxiliary material, which is then set aside.

[0125] Weigh out 80 parts by weight of silicate cement, 250 parts by weight of aggregate and 6 parts by weight of modified capsules prepared in Example 7 and add them to a mixer. Mix for 2 minutes. Add 30 parts by weight of auxiliary materials to the mixer and mix at low speed for 1 minute and at high speed for 1 minute. Add 3 parts by weight of modified fiber prepared in Example 1 and mix at high speed for 2 minutes to obtain concrete material.

[0126] Example 11

[0127] This embodiment provides a method for preparing fiber-reinforced crack-resistant and impermeable concrete material, including the following steps:

[0128] Mix 10mm crushed stone and 2mm quartz sand evenly at a mass ratio of 3:4 to obtain aggregate, and set aside for later use;

[0129] Polycarboxylate superplasticizer, diethylenetriamine and water are mixed evenly at a mass ratio of 1.5:3:7 to obtain the auxiliary material, which is then set aside.

[0130] Weigh out the following by weight: 90 parts silicate cement, 270 parts aggregate, and 8 parts modified capsules prepared in Example 8. Add them to a mixer and mix for 3 minutes. Add 40 parts auxiliary materials to the mixer and mix at low speed for 1.5 minutes and at high speed for 1.5 minutes. Add 5 parts modified fiber prepared in Example 2 and mix at high speed for 3 minutes to obtain concrete material.

[0131] Example 12

[0132] This embodiment provides a method for preparing fiber-reinforced crack-resistant and impermeable concrete material, including the following steps:

[0133] Mix 20mm crushed stone and 4mm quartz sand evenly at a mass ratio of 4:5 to obtain aggregate, and set aside for later use;

[0134] Polycarboxylate superplasticizer, diethylenetriamine and water are mixed evenly at a mass ratio of 2:4:8 to obtain the auxiliary material, which is then set aside.

[0135] Weigh out 100 parts by weight of silicate cement, 300 parts by weight of aggregate and 12 parts by weight of modified capsules prepared in Example 9 and add them to a mixer. Mix for 4 minutes. Add 50 parts by weight of auxiliary materials to the mixer and mix at low speed for 2 minutes and at high speed for 2 minutes. Add 6 parts by weight of modified fiber prepared in Example 3 and mix at high speed for 4 minutes to obtain concrete material.

[0136] Comparative Example 1

[0137] The difference between this comparative example and Example 12 is that, in the preparation of crack-resistant and impermeable concrete material, an equal amount of ammoniated carbon fiber is used to replace the modified fiber.

[0138] Comparative Example 2

[0139] The difference between this comparative example and Example 12 is that, in step (2) when preparing the modified capsule precursor, the addition of the modified epoxy monomer is omitted.

[0140] Comparative Example 3

[0141] The difference between this comparative example and Example 12 is that, in preparing the crack-resistant and impermeable concrete material, the modified epoxy capsule precursor is used in an equal amount to replace the modified capsule.

[0142] Performance testing:

[0143] Concrete specimens were made from the concrete materials prepared in Examples 10-12 and Comparative Examples 1-3 in accordance with the standard GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete".

[0144] The impermeability of the concrete specimens prepared in Examples 10-12 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete".

[0145] The water absorption, splitting tensile strength and flexural strength of the concrete specimens prepared in Examples 10-12 and Comparative Examples 1-3 were tested in accordance with the standard GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0146] See Table 1 for specific data.

[0147] Table 1 - Performance Test Data for Each Sample

[0148]

[0149] Data Analysis:

[0150] Comparative analysis of the data in Table 1 reveals that the concrete material prepared by this invention, after curing, exhibits a permeability grade of P10, a water absorption rate of 4.3%, a splitting tensile strength of 3.6 MPa, and a flexural strength of 8.5 MPa. All these data are superior to those of the comparative example. This invention achieves this by acidifying carbon fibers to introduce carboxyl groups, and then synthesizing a metal-organic framework containing amino groups on the acidified carbon fibers via a hydrothermal method. Post-synthetic modification of the metal-organic framework yields modified fibers with a maleimide structure. A modified epoxy monomer is prepared through phenolic condensation and epoxy group end-capping. A modified capsule precursor, using polyurea-formaldehyde resin as the wall material and the modified epoxy monomer as the core material, is then prepared via interfacial polymerization. Further modification of the modified capsule precursor with a silane coupling agent yields modified capsules. Adding modified capsules and modified fibers during the preparation of concrete materials not only improves their crack resistance and permeability but also enhances their mechanical properties.

[0151] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0152] 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.

[0153] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fiber-reinforced, crack-resistant, and impermeable concrete material, characterized in that, It comprises the following components by weight: 80-100 parts cement, 3-6 parts modified fiber, 6-12 parts modified capsule, 250-300 parts aggregate and 30-50 parts auxiliary materials; The cement is silicate cement, and the aggregate is composed of coarse aggregate and fine aggregate in a mass ratio of 2-4:3-5. The coarse aggregate is crushed stone of 5-20mm, and the fine aggregate is quartz sand of 1-4mm. The auxiliary materials are composed of water-reducing agent, curing agent and dispersant in a mass ratio of 1-2:2-4:6-8. The water-reducing agent is polycarboxylate water-reducing agent, the curing agent is diethylenetriamine, and the dispersant is water. The modified capsules are prepared by the following steps: A1. Place urea and formaldehyde aqueous solution in a reaction vessel and stir. Add triethanolamine to adjust the pH to 8-9. Heat the reaction vessel to 65-75℃ and keep it at this temperature for 60-90 minutes to obtain a mixed solution. A2. Place the modified epoxy monomer, sodium dodecyl sulfonate and deionized water in a reaction vessel and stir at room temperature for 30-60 min. Add the mixture and stir at room temperature for 15-30 min. Add resorcinol solution and add dilute hydrochloric acid to adjust the pH to 3-4. Heat the reaction vessel to 55-65℃ and keep it at that temperature for 2-4 h. Post-process to obtain the modified capsule precursor. A3. The modified capsule precursor, 3,3,3-trifluoropropyltriethoxysilane, ethanol and deionized water were placed in a reaction vessel and stirred. The reaction vessel was heated to 45-55℃, and an ammonia solution was added. The reaction was kept at this temperature for 2-4 hours. The modified capsules were then obtained after post-treatment. The modified epoxy monomer is prepared by the following steps: B1. Tris(2-aminoethyl)amine, 5-hydroxyfurfural and ethanol were placed in a reaction vessel and stirred. The reaction vessel was heated to 70-80℃ and kept at this temperature for 2-4 hours. After post-treatment, intermediate I was obtained. B2. Place epichlorohydrin, tetrabutylammonium bisulfate and N,N-dimethylformamide in a nitrogen-protected reactor and stir. Slowly add intermediate I. During the addition process, maintain the reaction system temperature at 20-25℃ and keep the reaction at this temperature for 4-6 hours. Add sodium hydroxide aqueous solution and keep the reaction at this temperature for 1-2 hours. Post-treatment yields the modified epoxy monomer. The modified fiber is prepared by the following steps: C1. Place carbon fiber and nitric acid solution in a reaction vessel and stir. Heat the reaction vessel to 65-75℃ and keep it at this temperature for 1-2 hours. Post-treatment yields acidified carbon fiber. C2. Place acidified carbon fiber, 2-aminoterephthalic acid, zirconium tetrachloride and N,N-dimethylformamide in a reaction vessel, heat the reaction vessel to 75-85℃, keep the reaction at this temperature for 6-8 hours, and then process to obtain ammoniated carbon fiber. C3. Place ammoniated carbon fiber and acetone in a reaction vessel and stir. Slowly add maleic anhydride solution and react at room temperature for 1-2 hours. Add sodium acetate, acetic anhydride and triethylamine. Heat the reaction vessel to 55-65℃ and keep it at that temperature for 10-12 hours. Post-treatment yields modified fiber.

2. The fiber-reinforced crack-resistant and impermeable concrete material according to claim 1, characterized in that, In step A1, the ratio of urea to formaldehyde aqueous solution is 2-4g:15-20mL, and the concentration of formaldehyde aqueous solution is 37-40wt%; in step A2, the ratio of modified epoxy monomer, sodium dodecyl sulfonate, deionized water, mixed solution, and resorcinol solution is 5-10g:0.5-1.5g:80-120mL:20-25mL:100-120mL, and the resorcinol solution is composed of resorcinol, chlorine... The sodium hydroxide and deionized water are used in a ratio of 2-4g:1-2g:80-100mL, and the concentration of the dilute hydrochloric acid is 0.5-1mol / L; in step A3, the ratio of the modified capsule precursor, 3,3,3-trifluoropropyltriethoxysilane, ethanol, deionized water and ammonia solution is 4-6g:1-2g:50-70mL:5-10mL:2-4mL, and the concentration of the ammonia solution is 50-70wt%.

3. The fiber-reinforced crack-resistant and impermeable concrete material according to claim 1, characterized in that, In step B1, the ratio of tris(2-aminoethyl)amine, 5-hydroxyfurfural, and ethanol is 4-6 g: 2-4 g: 100-120 mL; in step B2, the ratio of epichlorohydrin, tetrabutylammonium hydrogen sulfate, N,N-dimethylformamide, intermediate I, and sodium hydroxide aqueous solution is 6-8 g: 0.2-0.4 g: 80-100 mL: 4-6 g: 100-150 mL, and the concentration of the sodium hydroxide aqueous solution is 50-60 wt%.

4. The fiber-reinforced crack-resistant and impermeable concrete material according to claim 1, characterized in that, In step C1, the ratio of carbon fiber to nitric acid solution is 5-10g:100-150mL, and the nitric acid solution is a 50-60wt% aqueous nitric acid solution; in step C2, the ratio of acidified carbon fiber, 2-aminoterephthalic acid, zirconium tetrachloride, and N,N-dimethylformamide is 5-10g:0.5-1g:0.5-1g:150-200mL; in step C3, the ratio of ammoniated carbon fiber, acetone, maleic anhydride solution, sodium acetate, acetic anhydride, and triethylamine is 10-15g:50-100mL:40-60mL:0.5-1g:4-6mL:2-4mL, and the maleic anhydride solution is a 1-1.5mol / L maleic anhydride-acetone solution.

5. A method for preparing fiber-reinforced crack-resistant and impermeable concrete material as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Add cement, aggregate and modified capsules to the mixer and mix for 2-4 minutes to obtain the mixture; S2. Add the mixture and auxiliary materials to the mixer, mix at low speed for 1-2 minutes, mix at high speed for 1-2 minutes, add the modified fiber, and mix at high speed for 2-4 minutes to obtain the concrete material.

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