Anti-cracking concrete and preparation method thereof

Abstract

The invention discloses anti-cracking concrete and a preparation method thereof, and the anti-cracking concrete is prepared from the following raw materials in parts by weight: 400-450 parts of cement, 600-700 parts of fine aggregate, 900-1000 parts of gravel, 70-80 parts of a composite additive, 30-40 parts of modified fiber, 4-5 parts of a water reducing agent and 160-180 parts of water, the composite additive is prepared from fly ash, modified sepiolite, calcium sulphoaluminate and an air entraining agent; the modified sepiolite is obtained by taking sepiolite as a raw material, pretreating the sepiolite through a silane coupling agent and then sequentially reacting the pretreated sepiolite with sulfanilamide and dodecyl chloride. According to the invention, through the synergistic effect of the composite additive and the modified fiber, the comprehensive improvement of the crack resistance and mechanical strength of the concrete is realized, in the composite additive, the moderate expansion of calcium sulphoaluminate compensates the early shrinkage stress, the microbubble system formed by the air entraining agent relieves the stress concentration, and the dispersion effect of the polycarboxylate superplasticizer is matched, so that the crack resistance and mechanical strength of the concrete are improved. The hardened body forms a compact and uniform microstructure, and the tensile strength of the concrete is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to a crack-resistant concrete and a preparation method thereof. Background Art

[0002] Concrete is one of the most important civil engineering materials in modern times. It is a kind of artificial stone prepared by mixing cementitious materials, granular aggregates (also known as aggregates), water, and, if necessary, admixtures and mineral admixtures in a certain proportion, followed by uniform mixing, dense molding, and curing and hardening. Concrete has the advantages of rich raw materials, low cost, simple production process, strong plasticity, high strength, good durability, etc., making it the building engineering material with the largest consumption and the widest application range in the world today. However, concrete also has disadvantages such as low tensile strength, easy cracking, and small ultimate elongation, which greatly limit its application in specific engineering structures.

[0003] Concrete cracking is one of the problems widely concerned in the engineering field. The reasons for its occurrence are complex and diverse, mainly including: temperature stress caused by temperature changes, dry shrinkage and wet swelling caused by humidity changes, external load effects, uneven settlement of the foundation, steel bar corrosion, alkali-aggregate reaction, etc. These factors act alone or jointly, resulting in stress concentration inside the concrete. When the stress exceeds the tensile strength of the concrete, cracks will occur. The existence of cracks not only affects the aesthetics of the building, but also reduces the bearing capacity, durability and impermeability of the structure. In severe cases, it may even lead to structural failure, endangering people's lives and property safety.

[0004] To solve the problem of concrete cracking, various technical means have been developed. For example, fiber materials (such as steel fibers, polypropylene fibers, etc.) are incorporated into concrete to improve its tensile strength and toughness; expansive agents or shrinkage-reducing agents are used to compensate for the shrinkage of concrete; the concrete mix design is optimized to control the water-cement ratio and cement dosage; the curing during the construction process is strengthened to control the temperature and humidity changes; prestress technology is adopted to apply pre-compressive stress to the concrete. Chinese Patent Application CN109133740A discloses an anti-cracking concrete, the raw materials of which by weight include: 55-68 parts of cement, 70-100 parts of quartz sand, 20-40 parts of ceramic sand, 0.5-1.1 parts of mixed fiber, 3-8 parts of cordierite, 0.9-2.7 parts of light-burned magnesia, 7-15 parts of microsilica, 1.8-2.8 parts of zeolite, 4-8 parts of limestone powder, 1-3 parts of lead-zinc tailing composite powder, 0.2-1.3 parts of steel slag powder, 1.2-3.5 parts of rice husk, 0.5-2 parts of alumina hollow spheres, 0.5-2 parts of calcite powder, 0.1-0.28 parts of epoxy resin emulsion, 1-1.8 parts of waterproof agent, 20-28 parts of water, 0.6-2.6 parts of water reducer, 0.1-0.32 parts of sludge. The anti-cracking concrete proposed by this invention has high strength, good toughness, anti-cracking property and long service life. Another example is that Chinese Patent Application CN114349424A discloses a low-shrinkage anti-cracking concrete, the key points of its technical solution are that the concrete by weight includes 580-610 parts of cementitious materials, 780-880 parts of manufactured sand, 900-940 parts of crushed stone, 25-35 parts of admixtures, 130-160 parts of water, wherein the cementitious materials include cement, fly ash, slag powder and granulated blast furnace slag, and by weight ratio, cement:fly ash:slag powder:granulated blast furnace slag is 5:(1.6-2.1):(1.2-1.7):(0.9-1.3), achieving the effect of reducing the shrinkage rate of concrete.

[0005] Although the existing technologies have alleviated the problem of concrete cracking to a certain extent, there are still some deficiencies. For example, the compatibility of some fiber materials with the cement matrix is poor, which is likely to cause uneven fiber distribution and affect the anti-cracking effect; the use of expansive agents may lead to out-of-control expansion in the later stage and generate new cracks; the prestress technology has high requirements for construction technology and relatively high costs.

[0006] Therefore, developing a concrete with good durability, high strength and anti-cracking property has important engineering application value and broad market prospects. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technologies, the purpose of the present invention is to provide an anti-cracking concrete and its preparation method. This concrete has good durability, and at the same time has relatively high mechanical properties and anti-cracking property, and has good application prospects.

[0008] To achieve the above object, the present invention provides the following technical solutions: An anti-cracking concrete, by weight, comprises the following raw materials: 400 - 450 parts of cement, 600 - 700 parts of fine aggregate, 900 - 1000 parts of gravel, 70 - 80 parts of composite additive, 30 - 40 parts of modified fiber, 4 - 5 parts of water-reducing agent, 160 - 180 parts of water; the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate and air-entraining agent; The modified sepiolite is prepared by using sepiolite as the raw material, pretreating it with a silane coupling agent, and then reacting it with sulfanilamide and dodecyl chloride in sequence.

[0009] In the present invention, through the synergistic effect of the composite additive and the modified fiber, the comprehensive improvement of the anti-cracking performance and mechanical strength of the concrete is realized. In the composite additive, the moderate expansion of calcium sulfoaluminate compensates for the early shrinkage stress, and the microbubble system formed by the air-entraining agent alleviates the stress concentration. Combined with the dispersion effect of the polycarboxylate water-reducing agent, a dense and uniform microstructure is formed in the hardened body, improving the tensile strength of the concrete.

[0010] Preferably, an anti-cracking concrete, by weight, comprises the following raw materials: 420 - 450 parts of cement, 650 - 700 parts of fine aggregate, 900 - 950 parts of gravel, 75 - 80 parts of composite additive, 30 - 35 parts of modified fiber, 4 - 4.5 parts of water-reducing agent, 170 - 180 parts of water.

[0011] Preferably, the fine aggregate is river sand with a particle size of 0.45 - 0.65 mm; the gravel is one or more of basalt gravel, limestone gravel, and granite gravel with a particle size of 1 - 2 cm; the water-reducing agent is a polycarboxylate water-reducing agent; the mass ratio of fly ash, modified sepiolite, calcium sulfoaluminate and air-entraining agent is 30 - 40:15 - 20:15 - 20:0.3 - 0.5.

[0012] Preferably, the preparation method of the modified sepiolite is as follows: S1. Add sepiolite to dilute hydrochloric acid, perform impregnation treatment, then wash, dry and ball mill it. Subsequently, add it to an ethanol aqueous solution, then add γ-glycidoxypropyltrimethoxysilane, adjust the pH to 4 - 5, and carry out a stirring reaction. After the reaction is completed, filter, wash and dry to obtain pretreated sepiolite; S2. Add the pretreated sepiolite in step S1 to methyl ethyl ketone, then add sulfanilamide and pyridine, and carry out a constant temperature reaction. After the reaction is completed, filter, wash and dry to obtain organic sepiolite; S3. Add the organic sepiolite obtained in step S2 into toluene, then add dodecyl chloride and triethylamine, and carry out a heating reaction under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0013] Preferably, in step S1, the temperature of the impregnation treatment is 30 - 40 °C, and the time is 2 - 3 h; the mass ratio of the sepiolite to γ - glycidoxypropyltrimethoxysilane is 60 - 70:7 - 9, the temperature of the stirring reaction is 50 - 60 °C, and the time is 3 - 4 h.

[0014] In the present invention, through acid leaching treatment, impurities such as carbonates on the surface of sepiolite are removed, and its reaction activity is improved. Subsequently, it reacts with γ - glycidoxypropyltrimethoxysilane to introduce epoxy groups onto the sepiolite.

[0015] Preferably, in step S2, the mass ratio of the pretreated sepiolite, sulfanilamide, and pyridine is 60 - 70:6 - 8:0.8 - 1.1, the temperature of the constant - temperature reaction is 60 - 70 °C, and the time is 5 - 7 h.

[0016] In the present invention, the epoxy groups on the sepiolite react with the amino groups on sulfanilamide, and sulfanilamide is introduced into the sepiolite in the form of covalent bonds. On the one hand, the sulfanilamide molecule contains sulfonamide groups and amino groups, and these groups have strong polarity and reaction activity. The sulfonamide groups can interact with harmful ions in concrete (such as chloride ions, sulfate ions, etc.), and adsorb these ions on the surface of sepiolite through hydrogen bonding, electrostatic adsorption, or coordination, etc., reducing their concentration in the pore solution of concrete, thereby slowing down or preventing the erosion of these ions on concrete and improving the durability of concrete.

[0017] Preferably, in step S3, the mass ratio of the organic sepiolite, dodecyl chloride, and triethylamine is 70 - 80:6 - 7:4.5 - 5.5, the temperature of the heating reaction is 70 - 80 °C, and the time is 4 - 6 h.

[0018] In the present invention, the sulfonamide groups on sulfanilamide react with the chlorine atoms on dodecyl chloride, thereby introducing long - chain alkyl groups onto the sepiolite, making the modified sepiolite form a structure similar to the function of a surfactant. It can reduce the surface tension of the pore solution in concrete, thereby reducing the capillary tension and shrinkage stress, achieving the purpose of reducing shrinkage and cracking, and thus improving the anti - cracking property of concrete.

[0019] Preferably, the preparation method of the modified fiber is as follows: Add antigorite fibers into an ethanol aqueous solution, then add vinyltriethoxysilane, and carry out a stirring reaction. After the reaction is completed, filter, wash, and dry to obtain pretreated antigorite fibers; add the pretreated antigorite fibers and sodium dodecyl sulfate into deionized water, add methyl acrylate, acrylic acid, and potassium persulfate, and carry out a reaction. After the reaction is completed, filter and dry to obtain the modified fibers.

[0020] Preferably, the mass ratio of the antigorite fibers to vinyltriethoxysilane is 30 - 40:5 - 6, the temperature of the stirring reaction is 50 - 60 °C, and the time is 3 - 4 h; the mass ratio of the pretreated antigorite fibers, sodium dodecyl sulfate, deionized water, methyl acrylate, acrylic acid, and potassium persulfate is 30 - 40:0.3 - 0.5:500 - 600:3 - 4:7 - 10:0.1 - 0.15, the temperature of the reaction is 65 - 75 °C, and the time is 1 - 2 h.

[0021] In the present invention, by modifying the antigorite fibers, their dispersion performance can be improved. At the same time, introducing vinyltriethoxysilane can enhance their free radical reaction with methyl acrylate and acrylic acid. The hydrophilic groups in the methyl acrylate - acrylic acid copolymer can enhance the water absorption and water retention ability of the antigorite fibers, enabling them to play the role of a "miniature reservoir" in the cement matrix, delaying the loss of water, and thus reducing drying shrinkage.

[0022] The present invention also protects a preparation method of the anti - cracking concrete as described above, including the following steps: Weigh the raw materials according to the formula. Add fine aggregate, crushed stone, and composite additive into a concrete mixer and dry - mix for 4 - 6 min. Then add cement, modified fibers, and water - reducing agent, and continue to stir for 7 - 10 min. Then add water and mix for 5 - 10 min. Subsequently, pour into a mold and cure in a standard curing box to obtain the anti - cracking concrete.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) For the anti - cracking concrete provided by the present invention, through the synergistic effect of the composite additive, modified fibers, and optimized mix proportion design, the anti - cracking performance, mechanical properties, and durability of the concrete are significantly improved. In the composite additive, the micro - aggregate effect and secondary hydration reaction of fly ash, the nano - scale strengthening and adsorption effect of modified sepiolite, the micro - expansion effect of calcium sulfoaluminate, and the tiny air bubbles introduced by the air - entraining agent jointly improve the microscopic structure of the concrete, increasing the density and anti - cracking property; the modified fibers introduce methyl acrylate - acrylic acid copolymer through chemical bonds, enhancing the interfacial bonding force with the cement matrix, effectively inhibiting the generation and expansion of cracks. The two work together to reduce the shrinkage and temperature stress of the concrete, improving the anti - cracking performance and durability of the concrete.

[0024] (2) The anti-cracking concrete provided by the present invention incorporates modified sepiolite, which has been triple-modified with a silane coupling agent, sulfanilamide, and dodecyl chloride, significantly enhancing its reinforcing effect and functionality in the concrete. The silane coupling agent introduces organic groups onto the surface of sepiolite, improving its compatibility with the cement matrix. The introduction of sulfanilamide endows sepiolite with the ability to adsorb harmful substances. The long-chain alkyl structure of dodecyl chloride enables the modified sepiolite to form a structure similar to that of a surfactant, which can reduce the surface tension of the pore solution in the concrete, thereby reducing the capillary tension and shrinkage stress, achieving the purpose of shrinkage reduction and crack resistance, and thus improving the anti-cracking property of the concrete. Through multi-step modification of sepiolite, a surfactant-functional compound is introduced onto sepiolite by chemical grafting. Compared with direct physical blending, it can be evenly dispersed in the cement matrix, avoiding local over-concentration or under-concentration. At the same time, sepiolite can also play a certain protective role, reducing its direct contact with the cement hydration environment and enhancing the durability of its shrinkage reduction effect. The modified sepiolite can not only improve the density and strength of the concrete as a nano-scale reinforcing material but also enhance the durability of the concrete.

[0025] (3) The anti-cracking concrete provided by the present invention incorporates modified fibers. By introducing a methyl acrylate-acrylic acid copolymer onto the surface of brucite fibers, the hydrophilicity of the brucite fibers is improved, and at the same time, the interfacial bonding strength between the fibers and the cement matrix is enhanced. The added sodium dodecyl sulfate reduces the surface tension of the fibers, enabling better wetting of the fibers by methyl acrylate and acrylic acid, and resulting in a stronger bonding force between the methyl acrylate-acrylic acid copolymer and the fibers. The modified fibers can more effectively bridge microcracks, prevent crack propagation, and improve the anti-cracking performance and toughness of the concrete. Detailed implementation mode

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work shall fall within the scope of protection of the present invention.

[0027] In the following embodiments, the cement used is Conch brand P·Ⅱ 52.5R Portland cement, the sepiolite has a mesh number of 800 mesh, the fiber length of the brucite fibers is 3 - 6 mm, and the air-entraining agent is a rosin-based air-entraining agent, preferably sodium rosinate.

[0028] Example 1 An anti-cracking concrete, by weight, comprises the following raw materials: 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additive, 35 parts of modified fiber, 4.5 parts of polycarboxylate superplasticizer, 170 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, and the crushed stone is basalt crushed stone with a particle size of 1 - 2 cm. The composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 35:18:17:0.4.

[0029] The preparation method of the modified sepiolite is as follows: S1. Add 65 g of sepiolite to 5 wt% dilute hydrochloric acid, impregnate at 35 °C for 2.5 h, wash and dry after treatment, ball mill at 1000 r / min for 30 min, then add it to 800 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidoxypropyltrimethoxysilane, adjust the pH to 4.5 with glacial acetic acid, stir and react at 55 °C for 3.5 h, filter, wash and dry after the reaction to obtain pretreated sepiolite; S2. Add 65 g of the pretreated sepiolite in step S1 to 800 mL of butanone, then add 7 g of sulfanilamide and 1 g of pyridine, react at a constant temperature of 65 °C for 6 h, filter, wash and dry after the reaction to obtain organic sepiolite; S3. Add 75 g of the organic sepiolite in step S2 to 900 mL of toluene, then add 6.5 g of dodecyl chloride and 5 g of triethylamine, react at 75 °C for 5 h under nitrogen protection, filter, wash and dry after the reaction to obtain modified sepiolite.

[0030] The preparation method of the modified fiber is as follows: Add 35 g of brucite fiber to 600 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 5.5 g of vinyltriethoxysilane, react at 55 °C for 3.5 h, filter, wash and dry after the reaction to obtain pretreated brucite fiber; add 35 g of the pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate to 550 g of deionized water, then add 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, react at 70 °C for 1.5 h, filter and dry after the reaction to obtain the modified fiber.

[0031] A preparation method of crack-resistant concrete includes the following steps: Weigh the raw materials according to the formula, add the fine aggregate, crushed stone, and composite additive to a concrete mixer and dry mix for 5 min, then add cement, modified fiber, and superplasticizer, continue to stir for 9 min, then add water and mix for 8 min, then pour into a mold for molding, and place it in a standard curing box for curing to obtain the crack-resistant concrete.

[0032] Example 2 An anti-cracking concrete, by weight, comprises the following raw materials: 400 parts of cement, 600 parts of fine aggregate, 900 parts of crushed stone, 70 parts of composite additive, 30 parts of modified fiber, 4 parts of polycarboxylate superplasticizer, 160 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, and the crushed stone is limestone crushed stone with a particle size of 1 - 2 cm. The composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate and air-entraining agent with a mass ratio of 30:15:15:0.3.

[0033] The preparation method of the modified sepiolite is as follows: S1. Add 60 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate at 30 °C for 3 h, wash and dry after treatment, ball mill at 1000 r / min for 30 min, then add it into 800 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 7 g of γ-glycidoxypropyltrimethoxysilane, adjust the pH to 5 with glacial acetic acid, stir and react at 50 °C for 4 h, filter, wash and dry after the reaction to obtain pretreated sepiolite; S2. Add 60 g of the pretreated sepiolite in step S1 into 800 mL of butanone, then add 6 g of sulfanilamide and 0.8 g of pyridine, react at a constant temperature of 60 °C for 7 h, filter, wash and dry after the reaction to obtain organic sepiolite; S3. Add 70 g of the organic sepiolite in step S2 into 900 mL of toluene, then add 6 g of dodecyl chloride and 4.5 g of triethylamine, react at 70 °C for 6 h under nitrogen protection, filter, wash and dry after the reaction to obtain modified sepiolite.

[0034] The preparation method of the modified fiber is as follows: Add 30 g of brucite fiber into 600 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 5 g of vinyltriethoxysilane, react at 50 °C for 4 h, filter, wash and dry after the reaction to obtain pretreated brucite fiber; add 30 g of the pretreated brucite fiber and 0.3 g of sodium dodecyl sulfate into 500 g of deionized water, then add 3 g of methyl acrylate, 7 g of acrylic acid and 0.1 g of potassium persulfate, react at 65 °C for 2 h, filter and dry after the reaction to obtain the modified fiber.

[0035] A preparation method of an anti-cracking concrete, comprising the following steps: Weigh the raw materials according to the formula. Add the fine aggregate, crushed stone, and composite additive into a concrete mixer and dry mix for 4 minutes. Then add the cement, modified fiber, and water reducing agent, and continue to mix for 7 minutes. Next, add water and mix for 5 minutes. Subsequently, pour into a mold and cure in a standard curing box to obtain the anti-cracking concrete.

[0036] Example 3 An anti-cracking concrete, by weight, comprises the following raw materials: 450 parts of cement, 700 parts of fine aggregate, 1000 parts of crushed stone, 80 parts of composite additive, 40 parts of modified fiber, 5 parts of polycarboxylate water reducing agent, and 180 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, and the crushed stone is granite crushed stone with a particle size of 1 - 2 cm. The composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 40:20:20:0.5.

[0037] The preparation method of the modified sepiolite is as follows: S1. Add 70 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate at 40 °C for 2 h. After the treatment, wash and dry, ball mill at 1000 r / min for 30 min. Then add it into 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidoxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4, stir and react at 60 °C for 3 h. After the reaction, filter, wash, and dry to obtain pretreated sepiolite; S2. Add 70 g of the pretreated sepiolite in step S1 into 800 mL of methyl ethyl ketone, then add 8 g of sulfanilamide and 1.1 g of pyridine, react at a constant temperature of 70 °C for 5 h. After the reaction, filter, wash, and dry to obtain organic sepiolite; S3. Add 80 g of the organic sepiolite in step S2 into 900 mL of toluene, then add 7 g of dodecyl chloride and 5.5 g of triethylamine, react at 80 °C for 4 h under nitrogen protection. After the reaction, filter, wash, and dry to obtain modified sepiolite.

[0038] The preparation method of the modified fiber is as follows: Add 40 g of brucite fiber into 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 6 g of vinyltriethoxysilane, react at 60 °C for 3 h. After the reaction, filter, wash, and dry to obtain pretreated brucite fiber; Add 40 g of the pretreated brucite fiber and 0.5 g of sodium dodecyl sulfate into 600 g of deionized water, then add 4 g of methyl acrylate, 10 g of acrylic acid, and 0.15 g of potassium persulfate, react at 75 °C for 1 h. After the reaction, filter and dry to obtain the modified fiber.

[0039] A preparation method of crack-resistant concrete comprises the following steps: Weigh the raw materials according to the formula, add fine aggregate, crushed stone, and composite additive into a concrete mixer and dry-mix for 6 min, then add cement, modified fiber, and water reducer, continue to mix for 10 min, then add water and mix for 10 min, then pour into a mold for molding, and place in a standard curing box for curing to obtain the crack-resistant concrete.

[0040] Comparative Example 1 A kind of crack-resistant concrete, by weight, comprises the following raw materials: 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additive, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, 170 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, the crushed stone is basalt crushed stone with a particle size of 1 - 2 cm, and the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 35:18:17:0.4.

[0041] The preparation method of the modified sepiolite is as follows: S1. Add 65 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate at 35 °C for 2.5 h, after treatment, wash and dry, ball-mill at 1000 r / min for 30 min, then add into 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidoxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55 °C for 3.5 h, after the reaction is completed, filter, wash, and dry to obtain pretreated sepiolite; S2. Add 65 g of the pretreated sepiolite in step S1 into 800 mL of methyl ethyl ketone, then add 7 g of sulfanilamide and 1 g of pyridine, react at a constant temperature of 65 °C for 6 h, after the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0042] The preparation method of the modified fiber is as follows: Add 35 g of brucite fiber into 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 5.5 g of vinyltriethoxysilane, react at 55 °C for 3.5 h, after the reaction is completed, filter, wash, and dry to obtain pretreated brucite fiber; add 35 g of the pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate into 550 g of deionized water, then add 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, react at 70 °C for 1.5 h, after the reaction is completed, filter and dry to obtain the modified fiber.

[0043] A preparation method of crack-resistant concrete, comprising the following steps: Weigh the raw materials according to the formula, add fine aggregate, crushed stone, and composite additive into a concrete mixer and dry mix for 5 min, then add cement, modified fiber, and water reducer, continue to mix for 9 min, then add water and mix for 8 min, then pour into a mold for molding, and place it in a standard curing box for curing to obtain the crack-resistant concrete.

[0044] Compared with Example 1, dodecyl chloride was not introduced into the modified sepiolite in this comparative example.

[0045] Comparative Example 2 A kind of crack-resistant concrete, by weight, comprises the following raw materials: 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additive, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, the crushed stone is basalt crushed stone with a particle size of 1 - 2 cm, and the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 35:18:17:0.4.

[0046] The preparation method of the modified sepiolite is as follows: S1. Add 65 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate at 35 °C for 2.5 h, after treatment, wash and dry, ball mill at 1000 r / min for 30 min, then add it into 800 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidoxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55 °C for 3.5 h, after the reaction is completed, filter, wash, and dry to obtain pretreated sepiolite; S2. Add 75 g of the pretreated sepiolite in step S2 into 900 mL of toluene, then add 6.5 g of dodecyl chloride and 5 g of triethylamine, react at 75 °C for 5 h under nitrogen protection, after the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0047] The preparation method of the modified fiber is as follows: Add 35 g of brucite fiber into 600 mL of ethanol aqueous solution (volume ratio of ethanol to water is 4:1), then add 5.5 g of vinyltriethoxysilane, react at 55 °C for 3.5 h, after the reaction is completed, filter, wash, and dry to obtain pretreated brucite fiber; add 35 g of the pretreated brucite fiber, 0.4 g of sodium dodecyl sulfate into 550 g of deionized water, then add 3.5 g of methyl acrylate, 9 g of acrylic acid, 0.13 g of potassium persulfate, react at 70 °C for 1.5 h, after the reaction is completed, filter and dry to obtain the modified fiber.

[0048] A preparation method of crack-resistant concrete comprises the following steps: Weigh the raw materials according to the formula. Add fine aggregate, gravel, and composite additive into a concrete mixer and dry-mix for 5 min. Then add cement, modified fiber, and water-reducing agent, and continue to mix for 9 min. Next, add water and mix for 8 min. Subsequently, pour into a mold for molding and place it in a standard curing box for curing to obtain the crack-resistant concrete.

[0049] Compared with Example 1, p-aminobenzenesulfonamide was not introduced into the modified sepiolite in this comparative example.

[0050] Comparative Example 3 A kind of crack-resistant concrete, by weight, comprises the following raw materials: 430 parts of cement, 650 parts of fine aggregate, 950 parts of gravel, 75 parts of composite additive, 35 parts of modified fiber, 4.5 parts of polycarboxylate water-reducing agent, and 170 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, the gravel is basalt gravel with a particle size of 1 - 2 cm, and the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 35:18:17:0.4.

[0051] The preparation method of the modified sepiolite is as follows: Add 65 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate at 35 °C for 2.5 h. After the treatment, wash and dry, then ball-mill at 1000 r / min for 30 min. Subsequently, add it into 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidoxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, and stir and react at 55 °C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain the modified sepiolite; The preparation method of the modified fiber is as follows: Add 35 g of brucite fiber into 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 5.5 g of vinyltriethoxysilane, and react at 55 °C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain the pretreated brucite fiber; add 35 g of pretreated brucite fiber, 0.4 g of sodium dodecyl sulfate into 550 g of deionized water, then add 3.5 g of methyl acrylate, 9 g of acrylic acid, 0.13 g of potassium persulfate, and react at 70 °C for 1.5 h. After the reaction is completed, filter and dry to obtain the modified fiber.

[0052] A preparation method of crack-resistant concrete comprises the following steps: Weigh the raw materials according to the formula. Add fine aggregate, crushed stone, and composite additive into a concrete mixer and dry mix for 5 minutes. Then add cement, modified fiber, and water reducing agent, and continue to mix for 9 minutes. Then add water and mix for 8 minutes. Subsequently, mold it and place it in a standard curing box for curing to obtain the anti-cracking concrete.

[0053] Compared with Example 1, in this comparative example, p-aminobenzenesulfonamide and dodecyl chloride are not introduced into the modified sepiolite.

[0054] Comparative Example 4 An anti-cracking concrete, by weight, comprises the following raw materials: 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additive, 35 parts of antigorite fiber, 4.5 parts of polycarboxylate water reducing agent, and 170 parts of water; The fine aggregate is river sand with a particle size of 0.45 - 0.65 mm, the crushed stone is basalt crushed stone with a particle size of 1 - 2 cm, and the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent with a mass ratio of 35:18:17:0.4.

[0055] The preparation method of the modified sepiolite is as follows: S1. Add 65 g of sepiolite into 5 wt% dilute hydrochloric acid, impregnate it at 35 °C for 2.5 h. After the treatment, wash and dry it, ball mill it at 1000 r / min for 30 min, then add it into 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1). Then add 8 g of γ-glycidoxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, and stir and react at 55 °C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain pretreated sepiolite; S2. Add 65 g of the pretreated sepiolite in step S1 into 800 mL of butanone, then add 7 g of p-aminobenzenesulfonamide and 1 g of pyridine, and react at a constant temperature of 65 °C for 6 h. After the reaction is completed, filter, wash, and dry to obtain organic sepiolite; S3. Add 75 g of the organic sepiolite in step S2 into 900 mL of toluene, then add 6.5 g of dodecyl chloride and 5 g of triethylamine, and react at 75 °C for 5 h under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0056] A preparation method of an anti-cracking concrete, comprising the following steps: Weigh the raw materials according to the formula. Add fine aggregate, crushed stone, and composite additive into a concrete mixer and dry mix for 5 minutes. Then add cement, antigorite fiber, and water reducing agent, and continue to mix for 9 minutes. Then add water and mix for 8 minutes. Subsequently, mold it and place it in a standard curing box for curing to obtain the anti-cracking concrete.

[0057] Compared with Example 1, the antigorite fiber was not modified in this comparative example.

[0058] After curing the crack-resistant concrete prepared in Examples 1-3 and Comparative Examples 1-4 for 28 days in an environment with a temperature of 20±5°C and a relative humidity of over 95%, the size of the concrete specimens was 100 mm×100 mm×100 mm. According to the "Standard Test Method for Physical and Mechanical Properties of Concrete" GB / T50081-2019, the compressive strength, flexural strength, and splitting tensile strength of the specimens were tested; referring to the "Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete" GB / T 50082-2009, the total cracking area per unit area of the specimens was determined; according to the "Test Method for Shrinkage of Cement Concrete" T574-2020, the drying shrinkage test (age 30 days) was carried out on the concrete prepared in each example and comparative example, and the test results are shown in Table 1 below: As can be seen from Table 1 above, the crack-resistant concrete prepared by the present invention has good compressive strength and flexural strength, and at the same time has good splitting tensile strength, and has a small total cracking area at 28 days and a drying shrinkage rate at 30 days, indicating that it has excellent crack resistance characteristics and durability, and has good application prospects.

[0059] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An anti-cracking concrete, characterized in that, By weight parts, it includes the following raw materials: 400 - 450 parts of cement, 600 - 700 parts of fine aggregate, 900 - 1000 parts of crushed stone, 70 - 80 parts of composite additive, 30 - 40 parts of modified fiber, 4 - 5 parts of water reducer, 160 - 180 parts of water; the composite additive is composed of fly ash, modified sepiolite, calcium sulfoaluminate and air-entraining agent; The modified sepiolite uses sepiolite as the raw material, is pretreated by a silane coupling agent, and then reacts with sulfanilamide and dodecyl chloride in sequence to obtain; The preparation method of the modified fiber is as follows: Add antigorite fiber into an ethanol aqueous solution, then add vinyltriethoxysilane, and carry out a stirring reaction. After the reaction is completed, filter, wash and dry to obtain pretreated antigorite fiber; add the pretreated antigorite fiber and sodium dodecyl sulfate into deionized water, add methyl acrylate, acrylic acid and potassium persulfate, and carry out a reaction. After the reaction is completed, filter and dry to obtain the modified fiber.

2. The crack-resistant concrete according to claim 1, wherein, By weight parts, it includes the following raw materials: 420 - 450 parts of cement, 650 - 700 parts of fine aggregate, 900 - 950 parts of crushed stone, 75 - 80 parts of composite additive, 30 - 35 parts of modified fiber, 4 - 4.5 parts of water reducer, 170 - 180 parts of water.

3. The anti-cracking concrete according to claim 1, wherein The fine aggregate is river sand, and the particle size of the river sand is 0.45 - 0.65 mm; the crushed stone is one or several of basalt crushed stone, limestone crushed stone, granite crushed stone, and the particle size is 1 - 2 cm; the water reducer is a polycarboxylate water reducer; the mass ratio of fly ash, modified sepiolite, calcium sulfoaluminate and air-entraining agent is 30 - 40:15 - 20:15 - 20:0.3 - 0.

5.

4. The anti-cracking concrete according to claim 1, characterized in that, The preparation method of the modified sepiolite is as follows: S1. Add sepiolite into dilute hydrochloric acid, after impregnation treatment, wash, dry and ball-mill, then add it into an ethanol aqueous solution, then add γ-glycidoxypropyltrimethoxysilane, adjust the pH to 4 - 5, and carry out a stirring reaction to obtain pretreated sepiolite; S2. Add the pretreated sepiolite into butanone, then add sulfanilamide and pyridine, and carry out a constant-temperature reaction to obtain organic sepiolite; S3. Add the organic sepiolite into toluene, then add dodecyl chloride and triethylamine, and carry out a heating reaction to obtain modified sepiolite.

5. The anti-cracking concrete according to claim 4, characterized in that, In step S1, the temperature of the impregnation treatment is 30 - 40 °C, and the time is 2 - 3 h; the mass ratio of sepiolite to γ-glycidoxypropyltrimethoxysilane is 60 - 70:7 - 9, and the temperature of the stirring reaction is 50 - 60 °C, and the time is 3 - 4 h.

6. The anti-cracking concrete according to claim 4, characterized in that, In step S2, the mass ratio of the pretreated sepiolite, sulfanilamide and pyridine is 60 - 70:6 - 8:0.8 - 1.1, and the temperature of the constant-temperature reaction is 60 - 70 °C, and the time is 5 - 7 h.

7. The anti-cracking concrete according to claim 4, wherein In step S3, the mass ratio of the organic sepiolite, dodecyl chloride and triethylamine is 70 - 80:6 - 7:4.5 - 5.5, and the temperature of the heating reaction is 70 - 80 °C, and the time is 4 - 6 h.

8. The anti-cracking concrete according to claim 1, wherein, The mass ratio of the brucite fiber to vinyltriethoxysilane is 30 - 40:5 - 6, the temperature of the stirring reaction is 50 - 60 °C, and the time is 3 - 4 h; the mass ratio of the pretreated brucite fiber, sodium dodecyl sulfate, deionized water, methyl acrylate, acrylic acid, and potassium persulfate is 30 - 40:0.3 - 0.5:500 - 600:3 - 4:7 - 10:0.1 - 0.15, the temperature of the reaction is 65 - 75 °C, and the time is 1 - 2 h.

9. A method for preparing the anti-cracking concrete according to any one of claims 1-8, characterized in that, It includes the following steps: Weigh the raw materials according to the formula, add the fine aggregate, gravel, and composite additive into the concrete mixer and dry - mix for 4 - 6 min, then add cement, modified fiber, and water - reducing agent, continue to stir for 7 - 10 min, then add water and mix for 5 - 10 min, then mold, and place it in a standard curing box for curing to obtain the anti - cracking concrete.

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