Anti-cracking concrete and preparation method thereof

Abstract

The present invention discloses a kind of anti-cracking concrete and preparation method thereof, and comprises the following raw materials by weight: 400-450 parts of cement, 600-700 parts of fine aggregate, 900-1000 parts of crushed stone, 70-80 parts of composite additives, 30-40 parts of modified fiber, 4-5 parts of water reducer, and 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 pretreated by a silane coupling agent with sepiolite as raw material, and then reacted with p-aminobenzenesulfonamide and dodecyl chloride in sequence. In the present invention, the comprehensive improvement of concrete crack resistance and mechanical strength is achieved by the synergistic effect of the composite additive and the modified fiber. 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 relieves stress concentration, cooperates with the dispersing effect of the polycarboxylate water reducer, so that the hardened body forms a dense and uniform microstructure, thereby improving the tensile strength of the concrete.

Description

Technical Field

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

[0002] Concrete is one of the most important civil engineering materials today. It is an artificial stone material made by mixing cementitious materials, granular aggregates (also known as aggregates), water, and, if necessary, admixtures and additives in specific proportions. The mixture is then uniformly mixed, compacted, and cured to harden. Concrete boasts abundant raw materials, low cost, simple production processes, strong plasticity, high strength, and excellent durability, making it the most widely used and widely used construction material in the world. However, concrete also has disadvantages such as low tensile strength, susceptibility to cracking, and low ultimate elongation, which significantly limit its application in specific engineering structures.

[0003] Concrete cracking is a common concern in the engineering community. Its causes are complex and diverse, primarily including: thermal stress caused by temperature fluctuations, shrinkage and expansion caused by humidity changes, external loads, uneven foundation settlement, steel corrosion, and alkali-aggregate reaction. These factors, acting individually or in combination, lead to stress concentrations within the concrete. When these stresses exceed the concrete's tensile strength, cracks form. The presence of cracks not only affects the building's aesthetics but also reduces the structure's bearing capacity, durability, and impermeability. In severe cases, they can even lead to structural failure, endangering people's lives and property.

[0004] To address concrete cracking, various technical approaches have been developed. These include incorporating fiber materials (such as steel fibers and polypropylene fibers) into concrete to increase its tensile strength and toughness; using expansion agents or shrinkage reducers to compensate for concrete shrinkage; optimizing concrete mix design to control the water-cement ratio and cement content; strengthening maintenance during construction to control temperature and humidity fluctuations; and employing prestressing technology to apply pre-compressive stress to concrete. Chinese patent application CN109133740A discloses a crack-resistant concrete, the raw materials of which include, by weight: 55-68 parts of cement, 70-100 parts of quartz sand, 20-40 parts of pottery 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 tailings composite powder, 0.2-1.3 parts of steel slag powder, 1.2-3.5 parts of rice husk, 0.5-2 parts of hollow alumina spheres, 0.5-2 parts of calcite powder, 0.1-0.28 parts of epoxy resin emulsion, 1-1.8 parts of waterproofing agent, 20-28 parts of water, 0.6-2.6 parts of water reducer, and 0.1-0.32 parts of sludge. The crack-resistant concrete proposed in this invention has high strength, good toughness, crack resistance, and a long service life. For another example, Chinese patent application CN114349424A discloses a low-shrinkage, crack-resistant concrete. The key technical solution is that the concrete comprises, by weight, 580-610 parts of cementitious material, 780-880 parts of manufactured sand, 900-940 parts of crushed stone, 25-35 parts of admixture, and 130-160 parts of water. The cementitious material comprises cement, fly ash, mineral powder, and slag, with a weight ratio of cement: fly ash: mineral powder: slag of 5: (1.6-2.1): (1.2-1.7): (0.9-1.3), thereby reducing the shrinkage of the concrete.

[0005] While existing technologies have alleviated concrete cracking to some extent, some shortcomings remain. For example, some fiber materials have poor compatibility with the cement matrix, which can lead to uneven fiber distribution and compromise crack resistance. The use of expansive agents can cause uncontrolled expansion later in the concrete, creating new cracks. Prestressed concrete technology requires sophisticated construction techniques and is relatively expensive.

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

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a crack-resistant concrete and a preparation method thereof, wherein the concrete has good durability, high mechanical properties and crack resistance, and has good application prospects.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0010] 400-450 parts of cement, 600-700 parts of fine aggregate, 900-1000 parts of crushed stone, 70-80 parts of composite additives, 30-40 parts of modified fiber, 4-5 parts of water reducer, and 160-180 parts of water; the composite additives are composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air entraining agent;

[0011] The modified sepiolite is prepared by using sepiolite as a raw material, pre-treating it with a silane coupling agent, and then reacting it with p-aminobenzenesulfonamide and dodecyl chloride in sequence.

[0012] In the present invention, the synergistic effect of the composite additive and the modified fiber is used to achieve a comprehensive improvement in the crack resistance and mechanical strength of concrete. In the composite additive, the moderate expansion of calcium sulfoaluminate compensates for the early shrinkage stress, the microbubble system formed by the air-entraining agent relieves stress concentration, and the dispersing effect of the polycarboxylate water-reducing agent enables the hardened body to form a dense and uniform microstructure, thereby improving the tensile strength of the concrete.

[0013] Preferably, a crack-resistant concrete comprises the following raw materials, calculated by weight: 420-450 parts of cement, 650-700 parts of fine aggregate, 900-950 parts of crushed stone, 75-80 parts of composite additives, 30-35 parts of modified fiber, 4-4.5 parts of water reducer, and 170-180 parts of water.

[0014] Preferably, the fine aggregate is river sand with a particle size of 0.45-0.65 mm; the crushed stone is one or more of basalt crushed stone, limestone crushed stone, and granite crushed stone with a particle size of 1-2 cm; the water reducer is a polycarboxylic acid-based water reducer; and the mass ratio of the fly ash, modified sepiolite, calcium sulfoaluminate, and air entraining agent is 30-40:15-20:15-20:0.3-0.5.

[0015] Preferably, the preparation method of the modified sepiolite is as follows:

[0016] S1, adding sepiolite to dilute hydrochloric acid, immersing the mixture, washing, drying, and ball-milling the mixture, then adding the mixture to an ethanol aqueous solution, adding γ-glycidyloxypropyltrimethoxysilane, adjusting the pH to 4-5, and stirring the mixture for reaction. After the reaction is completed, filtering, washing, and drying the mixture to obtain the pretreated sepiolite;

[0017] S2, adding the pretreated sepiolite in step S1 to butanone, then adding p-aminobenzenesulfonamide and pyridine, and reacting at a constant temperature. After the reaction is completed, filtering, washing, and drying to obtain organic sepiolite;

[0018] S3. Add the organic sepiolite in step S2 to toluene, then add dodecyl chloride and triethylamine, and heat the mixture under nitrogen protection to react. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0019] Preferably, the immersion treatment temperature in step S1 is 30-40°C and the time is 2-3 hours; the mass ratio of sepiolite and γ-glycidyloxypropyltrimethoxysilane is 60-70:7-9, and the stirring reaction temperature is 50-60°C and the time is 3-4 hours.

[0020] In the present invention, impurities such as carbonate on the surface of sepiolite are removed by acid leaching and its reactivity is improved, and then epoxy groups are introduced into the sepiolite by reacting with γ-glycidyloxypropyltrimethoxysilane.

[0021] Preferably, in step S2, the mass ratio of the pretreated sepiolite, p-aminobenzenesulfonamide, and pyridine is 60-70:6-8:0.8-1.1, the temperature of the isothermal reaction is 60-70° C., and the time is 5-7 hours.

[0022] In the present invention, p-aminobenzenesulfonamide is introduced into the sepiolite in the form of a covalent bond by utilizing the reaction between the epoxy groups on the sepiolite and the amino groups on the p-aminobenzenesulfonamide. On the one hand, the p-aminobenzenesulfonamide molecule contains sulfonamide groups and amino groups, which have strong polarity and reactivity. The sulfonamide groups can interact with harmful ions in concrete (such as chloride ions, sulfate ions, etc.), adsorbing these ions on the sepiolite surface through hydrogen bonding, electrostatic adsorption or coordination, thereby reducing their concentration in the concrete pore solution, thereby slowing down or preventing the corrosion of concrete by these ions and improving the durability of concrete.

[0023] Preferably, 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 heating reaction temperature is 70-80° C. and the reaction time is 4-6 hours.

[0024] In the present invention, the sulfonamide group on p-aminobenzenesulfonamide is reacted with the chlorine atom on dodecyl chloride to introduce a long-chain alkyl group into the sepiolite, so that the modified sepiolite forms a structure with a surfactant-like function, which can reduce the surface tension of the concrete pore solution, thereby reducing capillary tension and shrinkage stress, achieving the purpose of shrinkage reduction and crack resistance, thereby improving the crack resistance of concrete.

[0025] Preferably, the preparation method of the modified fiber is as follows:

[0026] Brucite fiber is added to an ethanol aqueous solution, followed by adding vinyltriethoxysilane, and stirred for reaction. After the reaction is completed, the mixture is filtered, washed, and dried to obtain pretreated brucite fiber. Pretreated brucite fiber and sodium lauryl sulfate are added to deionized water, followed by adding methyl acrylate, acrylic acid, and potassium persulfate, and reacted. After the reaction is completed, the mixture is filtered and dried to obtain modified fiber.

[0027] Preferably, the mass ratio of the brucite fiber and vinyltriethoxysilane is 30-40:5-6, the stirring reaction temperature is 50-60°C, and the time is 3-4 hours; the mass ratio of the pretreated brucite fiber, sodium lauryl 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 reaction temperature is 65-75°C, and the time is 1-2 hours.

[0028] In the present invention, the dispersion performance of brucite fiber can be improved by modifying the fiber. Meanwhile, the introduction of vinyl triethoxysilane can enhance the free radical reaction between the fiber and methyl acrylate and acrylic acid. The hydrophilic groups in the methyl acrylate-acrylic acid copolymer can enhance the water absorption and retention capacity of the brucite fiber, thereby enabling the fiber to act as a "micro-reservoir" in the cement matrix, delaying water loss and thus reducing drying shrinkage.

[0029] The present invention also protects a method for preparing the above-mentioned crack-resistant concrete, comprising the following steps:

[0030] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 4-6 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 7-10 minutes. Then, water is added and mixed for 5-10 minutes. Subsequently, the mixture is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The crack-resistant concrete provided by the present invention significantly improves the crack resistance, mechanical properties, and durability of concrete through the synergistic effect of composite additives, modified fibers, and optimized mix design. The composite additives include the micro-aggregate effect and secondary hydration reaction of fly ash, the nano-scale reinforcement and adsorption of modified sepiolite, the micro-expansion effect of calcium sulfoaluminate, and the tiny bubbles introduced by the air-entraining agent, which together improve the microstructure of the concrete, increasing its density and crack resistance. The modified fibers introduce methyl acrylate-acrylic acid copolymer through chemical bonds, enhancing the interfacial bonding with the cement matrix and effectively inhibiting the generation and expansion of cracks. The combined effect of the two reduces the shrinkage and temperature stress of concrete, improving the crack resistance and durability of the concrete.

[0033] (2) The crack-resistant concrete provided by the present invention has modified sepiolite added thereto, which is triple-modified with a silane coupling agent, p-aminobenzenesulfonamide, and dodecyl chloride, thereby significantly improving its reinforcing effect and functionality in concrete. Silane coupling agent introduces organic groups on the surface of sepiolite, improving its compatibility with the cement matrix. The introduction of p-aminobenzenesulfonamide gives sepiolite the ability to adsorb harmful substances. The long-chain alkyl structure of dodecyl chloride enables the modified sepiolite to form a structure similar to the function of a surfactant, which can reduce the surface tension of the concrete pore solution, thereby reducing capillary tension and shrinkage stress, achieving the purpose of shrinkage reduction and crack resistance, thereby improving the crack resistance of concrete. Through multi-step modification of sepiolite, surfactant-functional compounds are introduced into the sepiolite by chemical grafting. Compared with direct physical blending, they can be evenly dispersed in the cement matrix to avoid local concentrations that are too high or too low. At the same time, sepiolite can also play a certain protective role, reducing its direct contact with the cement hydration environment and improving the durability of its shrinkage reduction effect. Modified sepiolite can not only be used as a nano-level reinforcing material to improve the density and strength of concrete, but also improve the durability of concrete.

[0034] (3) The anti-cracking concrete provided by the present invention has modified fibers added thereto. By introducing methyl acrylate-acrylic acid copolymer on the surface of brucite fibers, the hydrophilicity of brucite fibers is improved, and the interfacial bonding strength between brucite fibers and cement matrix is ​​enhanced. The added sodium lauryl sulfate reduces the surface tension of the fibers, allowing methyl acrylate and acrylic acid to better infiltrate the fibers, 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 expansion, and improve the crack resistance and toughness of concrete. DETAILED DESCRIPTION

[0035] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] In the following examples, the cement is Conch brand P·II52.5R Portland cement, the mesh size of the sepiolite is 800 mesh, the fiber length of the brucite fiber is 3-6 mm, and the air entraining agent is a rosin-based air entraining agent, preferably sodium rosinate.

[0037] Example 1

[0038] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0039] 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additives, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water;

[0040] 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 consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 35:18:17:0.4.

[0041] The preparation method of the modified sepiolite is as follows:

[0042] S1. Add 65 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 35° C. for 2.5 h, wash and dry after treatment, and ball mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55° C. for 3.5 h. After completion of the reaction, filter, wash, and dry to obtain pretreated sepiolite;

[0043] S2, adding 65g of pretreated sepiolite in step S1 to 800mL of butanone, followed by adding 7g of p-aminobenzenesulfonamide and 1g of pyridine, and reacting at a constant temperature of 65°C for 6h. After the reaction is completed, filtering, washing, and drying to obtain organic sepiolite;

[0044] 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, and react at 75 ° C for 5 h under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0045] The preparation method of the modified fiber is as follows:

[0046] 35 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 5.5 g of vinyltriethoxysilane, and the reaction was carried out at 55°C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 35 g of pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate were added to 550 g of deionized water, followed by the addition of 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, and the reaction was carried out at 70°C for 1.5 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0047] A method for preparing crack-resistant concrete comprises the following steps:

[0048] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 5 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 9 minutes. Then, water is added and mixed for 8 minutes. Subsequently, the concrete is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0049] Example 2

[0050] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0051] 400 parts of cement, 600 parts of fine aggregate, 900 parts of crushed stone, 70 parts of composite additives, 30 parts of modified fiber, 4 parts of polycarboxylate water reducer, and 160 parts of water;

[0052] The fine aggregate is river sand with a particle size of 0.45-0.65 mm, the crushed stone is limestone with a particle size of 1-2 cm, and the composite additive consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 30:15:15:0.3.

[0053] The preparation method of the modified sepiolite is as follows:

[0054] S1. Add 60 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 30° C. for 3 h, wash and dry, and ball-mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 7 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 5, stir and react at 50° C. for 4 h, filter, wash, and dry after the reaction to obtain pretreated sepiolite;

[0055] S2, adding 60g of pretreated sepiolite in step S1 to 800mL of butanone, followed by adding 6g of p-aminobenzenesulfonamide and 0.8g of pyridine, and reacting at a constant temperature of 60°C for 7h. After the reaction is completed, filtering, washing, and drying to obtain organic sepiolite;

[0056] S3. Add 70 g of the organic sepiolite in step S2 to 900 mL of toluene, then add 6 g of dodecyl chloride and 4.5 g of triethylamine, and react at 70 ° C for 6 h under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0057] The preparation method of the modified fiber is as follows:

[0058] 30 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 5 g of vinyltriethoxysilane, and the reaction was carried out at 50°C for 4 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 30 g of pretreated brucite fiber and 0.3 g of sodium dodecyl sulfate were added to 500 g of deionized water, followed by the addition of 3 g of methyl acrylate, 7 g of acrylic acid, and 0.1 g of potassium persulfate, and the reaction was carried out at 65°C for 2 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0059] A method for preparing crack-resistant concrete comprises the following steps:

[0060] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 4 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 7 minutes. Then, water is added and mixed for 5 minutes. Subsequently, the concrete is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0061] Example 3

[0062] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0063] 450 parts of cement, 700 parts of fine aggregate, 1000 parts of crushed stone, 80 parts of composite additives, 40 parts of modified fiber, 5 parts of polycarboxylic acid water reducer, and 180 parts of water;

[0064] The fine aggregate is river sand with a particle size of 0.45-0.65 mm, the crushed stone is granite crushed stone with a particle size of 1-2 cm, and the composite additive consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 40:20:20:0.5.

[0065] The preparation method of the modified sepiolite is as follows:

[0066] S1. Add 70 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 40° C. for 2 h, wash and dry, and ball-mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 9 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4, stir and react at 60° C. for 3 h, filter, wash, and dry after the reaction to obtain pretreated sepiolite;

[0067] S2, adding 70g of pretreated sepiolite in step S1 to 800mL of butanone, followed by adding 8g of p-aminobenzenesulfonamide and 1.1g of pyridine, and reacting at 70°C for 5h. After the reaction is completed, filtering, washing, and drying to obtain organic sepiolite;

[0068] S3. Add 80 g of the organic sepiolite in step S2 to 900 mL of toluene, then add 7 g of dodecyl chloride and 5.5 g of triethylamine, and react at 80° C. for 4 h under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0069] The preparation method of the modified fiber is as follows:

[0070] 40 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 6 g of vinyltriethoxysilane, and the reaction was carried out at 60°C for 3 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 40 g of pretreated brucite fiber and 0.5 g of sodium dodecyl sulfate were added to 600 g of deionized water, followed by the addition of 4 g of methyl acrylate, 10 g of acrylic acid, and 0.15 g of potassium persulfate, and the reaction was carried out at 75°C for 1 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0071] A method for preparing crack-resistant concrete comprises the following steps:

[0072] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 6 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 10 minutes. Then, water is added and mixed for 10 minutes. Subsequently, the mixture is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0073] Comparative Example 1

[0074] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0075] 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additives, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water;

[0076] 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 consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 35:18:17:0.4.

[0077] The preparation method of the modified sepiolite is as follows:

[0078] S1. Add 65 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 35° C. for 2.5 h, wash and dry after treatment, and ball mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55° C. for 3.5 h. After completion of the reaction, filter, wash, and dry to obtain pretreated sepiolite;

[0079] S2. Add 65 g of the pretreated sepiolite in step S1 to 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 modified sepiolite.

[0080] The preparation method of the modified fiber is as follows:

[0081] 35 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 5.5 g of vinyltriethoxysilane, and the reaction was carried out at 55°C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 35 g of pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate were added to 550 g of deionized water, followed by the addition of 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, and the reaction was carried out at 70°C for 1.5 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0082] A method for preparing crack-resistant concrete comprises the following steps:

[0083] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 5 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 9 minutes. Then, water is added and mixed for 8 minutes. Subsequently, the concrete is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0084] Compared with Example 1, dodecyl chloride was not introduced into the modified sepiolite in this comparative example.

[0085] Comparative Example 2

[0086] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0087] 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additives, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water;

[0088] 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 consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 35:18:17:0.4.

[0089] The preparation method of the modified sepiolite is as follows:

[0090] S1. Add 65 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 35° C. for 2.5 h, wash and dry after treatment, and ball mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55° C. for 3.5 h. After completion of the reaction, filter, wash, and dry to obtain pretreated sepiolite;

[0091] S2. Add 75 g of the pretreated sepiolite in step S2 to 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.

[0092] The preparation method of the modified fiber is as follows:

[0093] 35 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 5.5 g of vinyltriethoxysilane, and the reaction was carried out at 55°C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 35 g of pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate were added to 550 g of deionized water, followed by the addition of 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, and the reaction was carried out at 70°C for 1.5 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0094] A method for preparing crack-resistant concrete comprises the following steps:

[0095] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 5 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 9 minutes. Then, water is added and mixed for 8 minutes. Subsequently, the concrete is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0096] Compared with Example 1, p-aminobenzenesulfonamide was not introduced into the modified sepiolite in this comparative example.

[0097] Comparative Example 3

[0098] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0099] 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additives, 35 parts of modified fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water;

[0100] 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 consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 35:18:17:0.4.

[0101] The preparation method of the modified sepiolite is as follows:

[0102] 65 g of sepiolite was added to 5 wt % dilute hydrochloric acid and immersed at 35° C. for 2.5 h. After the treatment, the mixture was washed and dried, and ball-milled at 1000 rpm for 30 min. The mixture was then added to 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by 8 g of γ-glycidyloxypropyltrimethoxysilane. Glacial acetic acid was added to adjust the pH to 4.5, and the mixture was stirred at 55° C. for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified sepiolite.

[0103] The preparation method of the modified fiber is as follows:

[0104] 35 g of brucite fiber was added to 600 mL of ethanol aqueous solution (the volume ratio of ethanol to water was 4:1), followed by the addition of 5.5 g of vinyltriethoxysilane, and the reaction was carried out at 55°C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain pretreated brucite fiber. 35 g of pretreated brucite fiber and 0.4 g of sodium dodecyl sulfate were added to 550 g of deionized water, followed by the addition of 3.5 g of methyl acrylate, 9 g of acrylic acid, and 0.13 g of potassium persulfate, and the reaction was carried out at 70°C for 1.5 h. After the reaction was completed, the mixture was filtered and dried to obtain modified fiber.

[0105] A method for preparing crack-resistant concrete comprises the following steps:

[0106] The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 5 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 9 minutes. Then, water is added and mixed for 8 minutes. Subsequently, the concrete is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0107] Compared with Example 1, p-aminobenzenesulfonamide and dodecyl chloride were not introduced into the modified sepiolite in this comparative example.

[0108] Comparative Example 4

[0109] A crack-resistant concrete comprising the following raw materials in parts by weight:

[0110] 430 parts of cement, 650 parts of fine aggregate, 950 parts of crushed stone, 75 parts of composite additives, 35 parts of brucite fiber, 4.5 parts of polycarboxylate water reducer, and 170 parts of water;

[0111] 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 consists of fly ash, modified sepiolite, calcium sulfoaluminate and air entraining agent in a mass ratio of 35:18:17:0.4.

[0112] The preparation method of the modified sepiolite is as follows:

[0113] S1. Add 65 g of sepiolite to 5 wt % dilute hydrochloric acid, immerse at 35° C. for 2.5 h, wash and dry after treatment, and ball mill at 1000 r / min for 30 min. Then add 800 mL of ethanol aqueous solution (the volume ratio of ethanol to water is 4:1), then add 8 g of γ-glycidyloxypropyltrimethoxysilane, add glacial acetic acid to adjust the pH to 4.5, stir and react at 55° C. for 3.5 h. After completion of the reaction, filter, wash, and dry to obtain pretreated sepiolite;

[0114] S2, adding 65g of pretreated sepiolite in step S1 to 800mL of butanone, followed by adding 7g of p-aminobenzenesulfonamide and 1g of pyridine, and reacting at a constant temperature of 65°C for 6h. After the reaction is completed, filtering, washing, and drying to obtain organic sepiolite;

[0115] 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, and react at 75 ° C for 5 h under nitrogen protection. After the reaction is completed, filter, wash, and dry to obtain modified sepiolite.

[0116] A method for preparing crack-resistant concrete comprises the following steps:

[0117] Raw materials were weighed according to the formula, and fine aggregate, crushed stone, and composite additives were added to a concrete mixer and dry-mixed for 5 minutes. Cement, brucite fiber, and a water reducer were then added and stirred for 9 minutes. Water was then added and mixed for 8 minutes. The concrete was then injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

[0118] Compared with Example 1, the brucite fiber was not modified in this comparative example.

[0119] The crack-resistant concrete prepared in Examples 1-3 and Comparative Examples 1-4 was cured for 28 days in an environment with a temperature of 20±5°C and a relative humidity of 95% or higher. The concrete specimens had a size of 100 mm×100 mm×100 mm. The compressive strength, flexural strength, and splitting strength of the specimens were tested according to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete". The total crack area per unit area of ​​the specimens was measured with reference to GB / T 50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete". The concrete prepared in each Example and Comparative Example was subjected to a drying shrinkage test (age 30 days) according to T574-2020 "Test Method for Shrinkage of Cement Concrete". The test results are shown in Table 1 below:

[0120] As can be seen from Table 1 above, the crack-resistant concrete prepared by the present invention has good compressive strength and flexural strength, as well as good splitting strength, and has a small 28d total crack area and 30d drying shrinkage rate, indicating that it has excellent crack resistance and durability and has good application prospects.

[0121] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A crack-resistant concrete, characterized in that: Calculated by weight, 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 additives, 30-40 parts of modified fiber, 4-5 parts of water reducer, and 160-180 parts of water; the composite additives are composed of fly ash, modified sepiolite, calcium sulfoaluminate, and air entraining agent; The modified sepiolite is prepared by pre-treating sepiolite with a silane coupling agent and then reacting with p-aminobenzenesulfonamide and dodecyl chloride in sequence. The preparation method of the modified sepiolite is as follows: S1, adding sepiolite to dilute hydrochloric acid, immersing the mixture, washing, drying, and ball-milling the mixture, then adding the mixture to an ethanol aqueous solution, and then adding γ-glycidyloxypropyltrimethoxysilane, adjusting the pH to 4-5, and stirring the mixture to react to obtain pretreated sepiolite; S2, adding the pretreated sepiolite to butanone, followed by adding p-aminobenzenesulfonamide and pyridine, and reacting at a constant temperature to obtain organic sepiolite; S3, adding organic sepiolite to toluene, followed by adding dodecyl chloride and triethylamine, and heating to react to obtain modified sepiolite; The immersion treatment temperature in step S1 is 30-40°C and the time is 2-3 hours; the mass ratio of the sepiolite and γ-glycidyloxypropyltrimethoxysilane is 60-70:7-9, the stirring reaction temperature is 50-60°C, and the time is 3-4 hours; the mass ratio of the pretreated sepiolite, p-aminobenzenesulfonamide, and pyridine in step S2 is 60-70:6-8:0.8-1.1, the constant temperature reaction temperature is 60-70°C, and the time is 5-7 hours; the mass ratio of the organic sepiolite, dodecyl chloride, and triethylamine in step S3 is 70-80:6-7:4.5-5.5, the heating reaction temperature is 70-80°C, and the time is 4-6 hours; The preparation method of the modified fiber is as follows: Brucite fiber is added to an ethanol aqueous solution, followed by adding vinyltriethoxysilane, and stirred for reaction. After the reaction is completed, the mixture is filtered, washed, and dried to obtain pretreated brucite fiber. Pretreated brucite fiber and sodium lauryl sulfate are added to deionized water, followed by adding methyl acrylate, acrylic acid, and potassium persulfate, and reacted. After the reaction is completed, the mixture is filtered and dried to obtain modified fiber.

2. The crack-resistant concrete according to claim 1, characterized in that: The raw materials include the following by weight: 420-450 parts of cement, 650-700 parts of fine aggregate, 900-950 parts of crushed stone, 75-80 parts of composite additives, 30-35 parts of modified fiber, 4-4.5 parts of water reducer and 170-180 parts of water.

3. The crack-resistant concrete according to claim 1, characterized in that: The fine aggregate is river sand with a particle size of 0.45-0.65 mm; the crushed stone is one or more of basalt crushed stone, limestone crushed stone, and granite crushed stone with a particle size of 1-2 cm; the water reducer is a polycarboxylic acid-based water reducer; and the mass ratio of the fly ash, modified sepiolite, calcium sulfoaluminate, and air-entraining agent is 30-40:15-20:15-20:0.3-0.

5.

4. The crack-resistant concrete according to claim 1, characterized in that: The mass ratio of the brucite fiber and vinyl triethoxysilane is 30-40:5-6, the stirring reaction temperature is 50-60°C, and the time is 3-4 hours; the mass ratio of the pretreated brucite fiber, sodium lauryl 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 reaction temperature is 65-75°C, and the time is 1-2 hours.

5. A method for preparing the crack-resistant concrete according to any one of claims 1 to 4, characterized in that: The following steps are involved: The raw materials are weighed according to the formula, and fine aggregate, crushed stone, and composite additives are added to a concrete mixer and dry-mixed for 4-6 minutes. Then, cement, modified fiber, and water reducer are added and stirred for 7-10 minutes. Then, water is added and mixed for 5-10 minutes. Subsequently, the mixture is injection-molded and placed in a standard curing box for curing to obtain the crack-resistant concrete.

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