Sulfate-resistant concrete and preparation method thereof

Abstract

The present application discloses a sulfate-resistant concrete and a preparation method thereof, which relates to the field of concrete. The raw materials include: 340-420 parts of cement, 88-128 parts of fly ash, 569-669 parts of sand, 1028-1128 parts of stone, 6.3-10.3 parts of water reducer, 21.4-27.4 parts of hydrophobic rust inhibitor, 118-145 parts of water, 12-15 parts of modified carbon nanotubes, and 3-7 parts of composite fiber; the hydrophobic rust inhibitor includes the following components: 0.3-0.5 parts of formic acid, 0.2-0.4 parts of polydimethylsiloxane, 3-7 parts of nano-silicon dioxide, 3-7 parts of triethanolamine, and 1-3 parts of N,N-bis(hydroxyethyl)-1-ol. The invention relates to a method for preparing sulfate-resistant concrete comprising: a mixture of 0.3-0.6 parts of carbon nanotubes, 0.2-0.5 parts of acetyl monoethanolamine, 0.3-0.6 parts of NaNO₃, 15-20 parts of concentrated HNO₃, 2-5 parts of KMnO₄, 2-5 parts of H₂O₂, and 20-30 parts of hydrochloric acid solution; and a composite fiber comprising polypropylene fiber, ceramic fiber, and steel fiber in a weight ratio of 1:(2.5-3):(2.5-3). The invention further comprises mixing the above raw materials to produce sulfate-resistant concrete. The concrete has strong sulfate resistance, high impermeability, and high compressive strength.

Description

Technical Field

[0001] The present application relates to the field of concrete, and in particular to a sulfate-resistant concrete and a preparation method thereof. Background Art

[0002] Accumulation, until the expansion pressure exceeds its ultimate tensile stress, thereby causing micro cracks, usually to achieve the concrete being attacked by sulfate is essentially an expansion reaction process: sulfate ions in the solution gradually penetrate into the interior of the concrete, and react chemically with the calcium compounds of the cement to generate expansive corrosion products, filling the concrete pores, thereby increasing the density of the concrete. As the corrosion reaction proceeds, the expansion products continue to resist sulfate corrosion, and the calcium compounds in the cement will be reduced.

[0003] For related materials, please refer to the Chinese invention patent CN104671729B, which discloses a sulfate-resistant concrete, including cementitious materials, sand, gravel, admixtures and mineral admixtures mixed with water, with a total cementitious material content of 450-660 kg / m 3 The total amount of sand is 720-890kg / m 3 The total amount of crushed stone is 900-1180kg / m 3 ; Among them: cement accounts for 55-67% of the total weight of the cementitious material, 95# granulated blast furnace slag accounts for 11-25% of the total weight of the cementitious material, silica fume accounts for 4-10% of the total weight of the cementitious material, fly ash accounts for 15-18% of the total weight of the cementitious material, preservative accounts for 0.8-1.5% of the total weight of the cementitious material, water reducer accounts for 0.5-1.0% of the total weight of the cementitious material, rust inhibitor accounts for 0.5-1.0% of the total weight of the cementitious material, air entraining agent accounts for 0.01-0.02% of the total weight of the cementitious material, the cement is No. 42.5 ordinary Portland cement, and the rust inhibitor is a high-performance polycarboxylic acid-based rust inhibitor.

[0004] Regarding the above-mentioned related technologies, the inventors believe that there are the following defects: the organic rust inhibitors used have relatively simple functions and only play a rust-inhibiting role by adsorbing on the surface of the steel bars to form a film. After the concrete is formed, it cannot prevent the entry of external corrosive ions and can only passively protect the steel bars from corrosion. As a result, the concrete's ability to resist sulfates is low and the durability of the concrete is low. Summary of the Invention

[0005] In order to improve the sulfate resistance of concrete, the present application provides a sulfate-resistant concrete and a preparation method thereof.

[0006] The present application provides a sulfate-resistant concrete, which adopts the following technical solution:

[0007] A sulfate-resistant concrete comprises, by weight, 340-420 parts of cement, 88-128 parts of fly ash, 569-669 parts of sand, 1028-1128 parts of stone, 6.3-10.3 parts of a water reducer, 21.4-27.4 parts of a hydrophobic rust inhibitor, and 118-145 parts of water. The hydrophobic rust inhibitor comprises the following components: 0.3-0.5 parts of formic acid, 0.2-0.4 parts of polydimethylsiloxane, 3-7 parts of nano-silicon dioxide, 3-7 parts of triethanolamine, 1-3 parts of N,N-bis(hydroxyethyl)dodecylamide, and 82-92 parts of water.

[0008] By adopting the above technical solution, a hydrophobic rust inhibitor is used, and polydimethylsiloxane is used to graft the rust inhibitor molecules of the multi-hydroxyamine group, so that the rust inhibitor has a strong hydrophobic group and a multi-site adsorption group. The rust inhibitor molecules are hydrolyzed with the hydroxyl group to achieve the response release of the multi-site adsorption group and the strong hydrophobic group. The released multi-site adsorption group competes with the sulfate ion for adsorption, and forms a film on the surface of the steel bar, isolating the contact between the corrosive ions and the steel bar, thereby improving the corrosion resistance of the steel bar. At the same time, the strong hydrophobic group and the Ca 2+ The insoluble fatty acid calcium formed can cover the pore wall of concrete cement stone, reduce the porosity of concrete, and form a hydrophobic film on the pore wall, improve the hydrophobicity of the concrete pore wall, and delay the transmission speed of sulfate ions in concrete. Through the synergistic effect of the above two aspects, the sulfate resistance of concrete is effectively improved.

[0009] Preferably, the sulfate-resistant concrete raw materials also include 12-15 parts of modified carbon nanotubes, and the modified carbon nanotube raw materials include the following components: 0.3-0.6 parts of carbon nanotubes, 0.2-0.5 parts of acetyl monoethanolamine, 0.3-0.6 parts of NaNO3, 15-20 parts of concentrated HNO3, 2-5 parts of KMnO4, 2-5 parts of H2O2, and 20-30 parts of hydrochloric acid solution.

[0010] By adopting the above technical solution, modified carbon nanotubes are used and modified by acetyl monoethanolamine, which can reduce the surface activity of the carbon nanotubes and prevent the carbon nanotubes from agglomerating. Through the dispersion ability of the carbon nanotubes, the carbon nanotubes can be combined with cement hydration products to bridge the microcracks in the concrete and improve the aggregate interface transition zone, forming a certain adhesion structure between the microcracks, reducing the porosity of the cement paste, making the concrete have a certain inhibitory effect on sulfate erosion, and improving the sulfate resistance of the concrete. At the same time, the effect of the carbon nanotubes on the structure of the concrete also enhances the compressive strength of the concrete.

[0011] Preferably, the sulfate-resistant concrete raw material further comprises 3-7 parts of composite fibers, wherein the composite fibers comprise polypropylene fibers, ceramic fibers, and steel fibers in a weight ratio of 1:(2.5-3):(2.5-3).

[0012] By adopting the above technical solution, a composite fiber of polypropylene fiber, ceramic fiber and steel fiber is used. The fibers are used to reduce the formation and expansion of early shrinkage cracks in concrete, thereby reducing the porosity inside the concrete. In addition, after adding fibers to the concrete, the migration of water between the various gaps can be reduced, and the number of capillaries formed due to water loss can be reduced, thereby achieving the effect of reducing capillary tension, thereby improving the anti-permeability performance of the concrete; the steel fiber is larger in size and can inhibit the expansion of macro cracks and improve the tensile strength and toughness of the matrix concrete; the polypropylene fiber has a smaller geometric size, a low modulus but a higher ductility, which can inhibit the generation and expansion of micro cracks in concrete and is easy to disperse in concrete; the ceramic fiber has strong chemical resistance, can withstand acid and alkali environments for a long time, and can maintain its chemical stability in concrete. By compounding the three, they stimulate and complement each other at different scales and performance levels, effectively improving the anti-permeability and sulfate resistance of the concrete.

[0013] Preferably, the water reducer is a mixture of one or more of naphthalene-based water reducer, polycarboxylic acid water reducer, and sulfonic acid-based water reducer.

[0014] By adopting the above technical solution, using naphthalene-based water reducers, polycarboxylic acid water reducers, and sulfonic acid-based water reducers, the compressive strength and impermeability of concrete can be improved through the adsorption and dispersion effect of the water reducers on cement. At the same time, without changing the water consumption of concrete, the fluidity of concrete can be increased and the workability can be improved.

[0015] The present application also provides a method for preparing sulfate-resistant concrete, which adopts the following technical solution:

[0016] A method for preparing sulfate-resistant concrete comprises the following steps:

[0017] 340-420 parts of cement, 88-128 parts of fly ash, 569-669 parts of sand, 1028-1128 parts of stone, 6.3-10.3 parts of water reducer, 21.4-27.4 parts of hydrophobic rust inhibitor, 118-145 parts of water, 12-15 parts of modified carbon nanotubes, and 3-7 parts of composite fibers are uniformly mixed to obtain crack-resistant concrete.

[0018] By adopting the above technical solution, using an appropriate water-cement ratio, adding a water reducer, a hydrophobic rust inhibitor, modified carbon nanotubes, and composite fibers, a concrete material with strong sulfate resistance, high impermeability, compressive strength, and slump can be produced.

[0019] Preferably, the preparation method of the hydrophobic rust inhibitor comprises the following steps:

[0020] S1. Heat 82-92 parts of water to 45-55 ° C, add 0.3-0.5 parts of formic acid while stirring and mix thoroughly, add 0.2-0.4 parts of polydimethylsiloxane, and stir to obtain a mixture;

[0021] S2. Add 3-7 parts of nano-silicon dioxide dispersion to the mixed solution obtained in S1 and stir evenly. Then add 3-7 parts of triethanolamine and 1-3 parts of N, N-bis(hydroxyethyl)dodecylamide and continue stirring to obtain a hydrophobic rust inhibitor.

[0022] By adopting the above technical solution, polydimethylsiloxane is used to graft the polyhydroxyamine-based rust inhibitor molecules, so that the rust inhibitor has strong hydrophobic groups and multi-site adsorption groups. The addition of hydrophobic rust inhibitor can effectively improve the sulfate resistance of concrete.

[0023] Preferably, S1. At -10-10 ℃, to a mixture of 0.3-0.6 parts of carbon nanotubes and 0.3-0.6 parts of NaNO3, 15-20 parts of concentrated HNO3 are added, stirred evenly, heated to 30-40 ℃, 2-5 parts of KMnO4 are added, stirred evenly, 25-45 parts of water are added and the temperature is raised to 80-100 ℃ and stirred again; finally, 2-5 parts of H2O2 solution are added, stirred and mixed, cooled, washed with distilled water until neutral, and vacuum dried to obtain carboxylated carbon nanotubes;

[0024] S2. Take carboxylated carbon nanotubes and add 20-30 parts of hydrochloric acid solution, and then evenly disperse 0.2-0.5 parts of acetyl monoethanolamine to the carbon nanotube hydrochloric acid solution, and evenly disperse the mixture. The reaction temperature was controlled at -5-5 ° C, stirred for 1-2h, and allowed to stand.

[0025] S3. The product obtained in S2 is filtered, washed with distilled water and ethanol in sequence, and dried under vacuum to obtain acetyl monoethanolamine-modified carbon nanotubes.

[0026] By adopting the above technical solution, carbon nanotubes are modified by acetyl monoethanolamine, which can reduce the surface activity of carbon nanotubes, prevent carbon nanotubes from agglomerating, improve the dispersion ability of carbon nanotubes, and add modified carbon nanotubes to improve the sulfate resistance of concrete. At the same time, the effect of carbon nanotubes on the structure of concrete also enhances the compressive strength of concrete.

[0027] Preferably, the method for preparing the composite fiber comprises the following steps:

[0028] Polypropylene fiber, ceramic fiber, and steel fiber are weighed in a weight ratio of 1:(2.5-3):(2.5-3), and 0.8-1.5 parts of a dispersant are added to each of them for mixing. Short fibers are obtained by crushing, sieving, acid washing, and drying. After the short fibers are mixed, 1-3 parts of a toughening agent are added and stirred to obtain the composite fiber.

[0029] By adopting the above technical solution, a composite fiber of polypropylene fiber, ceramic fiber and steel fiber is used. Through the compounding of the three, they stimulate and complement each other at different scales and performance levels, effectively improving the concrete's impermeability and sulfate resistance.

[0030] Preferably, the dispersant is calcium carbonate, and the high-strength agent is barium sulfate.

[0031] By adopting the above technical solution and using calcium carbonate, the dispersion performance of the fibers can be improved and the fibers can be prevented from agglomerating. At the same time, calcium carbonate can improve the impact toughness of the fibers during the crushing process, and improve the bending strength, dimensional stability and thermal stability of the fibers during the crushing process. Barium sulfate has great strength and can play a bearing role in the preparation of composite fibers, thereby producing a certain reinforcement effect, which is conducive to obtaining composite fibers with high strength and high toughness.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. By adopting the above technical solution, a hydrophobic rust inhibitor is used, and polydimethylsiloxane is used to graft the rust inhibitor molecules of the polyhydroxylamine group, so that the rust inhibitor has a strong hydrophobic group and a multi-site adsorption group. The rust inhibitor molecules are hydrolyzed with the hydroxyl group, and the multi-site adsorption group and the strong hydrophobic group are released in response. The released multi-site adsorption group competes with sulfate ions for adsorption, and forms a film on the surface of the steel bar, isolating the contact between the corrosive ions and the steel bar, and improving the corrosion resistance of the steel bar. At the same time, the strong hydrophobic group forms an insoluble fatty acid calcium with Ca2+, which can cover the pore wall of the concrete cement stone, reduce the porosity of the concrete, and form a hydrophobic film on the pore wall, thereby improving the hydrophobicity of the concrete pore wall and delaying the transmission speed of sulfate ions in the concrete. Through the synergistic effect of the above two aspects, the sulfate resistance of the concrete is effectively improved;

[0034] 2. By adopting the above technical solution, modified carbon nanotubes are used. Modifying the carbon nanotubes with acetyl monoethanolamine can reduce the surface activity of the carbon nanotubes, prevent the carbon nanotubes from agglomerating, and enhance the dispersion ability of the carbon nanotubes. The carbon nanotubes can combine with cement hydration products, bridge microcracks in the concrete, improve the aggregate interface transition zone, and form a certain adhesion structure between the microcracks. This reduces the porosity of the cement paste, makes the concrete have a certain inhibitory effect on sulfate attack, and improves the concrete's sulfate resistance. At the same time, the carbon nanotubes' effect on the concrete structure also enhances the concrete's compressive strength.

[0035] 3. By adopting the above technical solution, a composite fiber of polypropylene fiber, ceramic fiber and steel fiber is used. The fibers are used to reduce the formation and expansion of early shrinkage cracks in concrete, thereby reducing the porosity inside the concrete. In addition, after adding fibers to the concrete, the migration of water between the various gaps is reduced, and the number of capillaries formed due to water loss is reduced, thereby achieving the effect of reducing capillary tension, thereby improving the anti-permeability of the concrete; the steel fiber is larger in size and can inhibit the expansion of macro cracks and improve the tensile strength and toughness of the matrix concrete; the polypropylene fiber has a smaller geometric size, a low modulus but a higher ductility, which can inhibit the generation and expansion of micro cracks in concrete and is easy to disperse in concrete; the ceramic fiber has strong chemical resistance, can withstand acid and alkali environments for a long time, and can maintain its chemical stability in concrete. By compounding the three, they stimulate and complement each other at different scales and performance levels, effectively improving the anti-permeability and sulfate resistance of the concrete. DETAILED DESCRIPTION

[0036] The present application is further described in detail below with reference to the embodiments.

[0037] Example

[0038] Example 1

[0039] S1. 82g of water was heated to 45°C, 0.3g of formic acid was added while stirring, and the mixture was thoroughly mixed for 40 minutes. 0.2g of polydimethylsiloxane was added, and the mixture was stirred at 45°C for 10 hours to obtain a uniform mixture. 3g of nano-silica dispersion was added to the resulting mixture, and the mixture was stirred for 30 minutes. 3g of triethanolamine and 1g of N,N-bis(hydroxyethyl)dodecylamide were added, and the mixture was stirred for another 3 hours to obtain a hydrophobic rust inhibitor.

[0040] S2. At -10 ° C, 15 g of concentrated HNO3 with a mass fraction of 68% was added to a mixture of 0.3 g of carbon nanotubes and 0.3 g of NaNO3, stirred for 40 min, and then heated to 30 ° C and 2 g of KMnO4, after stirring for 1.5h, 25g of water was added and the temperature was raised to 80℃ and stirred for another 1.5h; finally, 2g of 30% H2O2 solution was added, stirred for 10min, cooled, washed with distilled water until neutral, and vacuum dried at 50℃ for 3h to obtain carboxylated carbon nanotubes; the carboxylated carbon nanotubes were added to 20g of 36.5% hydrochloric acid solution, dispersed at 200rpm for 20min to obtain a carbon nanotube hydrochloric acid solution, 0.2g of acetyl monoethanolamine was added to the carbon nanotube hydrochloric acid solution, and continued to disperse at 200rpm for 20min. The reaction temperature was controlled at -5℃, stirred for 1h, and then allowed to stand for 1.5h; the obtained product was filtered and washed with distilled water and ethanol in sequence. After washing, it was vacuum dried at 65℃ to obtain acetyl monoethanolamine-modified carbon nanotubes;

[0041] S3. 15 g of polypropylene fiber, 37.5 g of ceramic fiber, and 37.5 g of steel fiber were weighed in a mass ratio, and 0.8 g of calcium carbonate was added to each of them. The fibers were crushed, passed through a 300-mesh sieve, washed with 10% dilute hydrochloric acid, and dried at 110°C for 3 h to obtain short fibers. The three short fibers were mixed and fed into a blender, 1 g of barium sulfate was added, and stirred for 30 seconds to obtain the composite fiber.

[0042] S4. 340g of cement, 88g of fly ash, 569g of sand, 1028g of stone, 6.3g of water reducer, 21.4g of hydrophobic rust inhibitor, 118g of water, 12g of modified carbon nanotubes, and 3g of composite fiber are mixed evenly to obtain crack-resistant concrete. The cement used in this embodiment is Yuexiu P.Ⅱ.42.5, the fly ash is Class II fly ash, the fineness is 14%, the water demand ratio is 98.5%, the loss on ignition is 2.25%, and the water reducer is a naphthalene-based water reducer.

[0043] Example 2

[0044] S1. 87 g of water was heated to 50°C, 0.4 g of formic acid was added while stirring, and the mixture was thoroughly mixed for 50 minutes. 0.2 g of polydimethylsiloxane was added, and the mixture was stirred at 55°C for 11 hours to obtain a uniform mixture. 5 g of the nano-silica dispersion was added to the resulting mixture, and the mixture was stirred for 40 minutes. 5 g of triethanolamine and 2 g of N, N-bis(hydroxyethyl)dodecylamide were added, and the mixture was stirred for 3.5 hours to obtain a hydrophobic rust inhibitor.

[0045] S2. At 0 ° C, 17 g of 68% concentrated HNO3 was added to a mixture of 0.3 g of carbon nanotubes and 0.45 g of NaNO3, stirred for 50 min, and then heated to 35 ° C and 3.5 g of KMnO4, after stirring for 2h, 30g of water was added and the temperature was raised to 90℃ and stirred for another 2h; finally, 3.5g of 30% H2O2 solution was added, stirred for 15min, cooled, washed with distilled water until neutral, and vacuum dried at 60℃ for 3.5h to obtain carboxylated carbon nanotubes; the carboxylated carbon nanotubes were added to 25g of 36.5% hydrochloric acid solution, dispersed at 300rpm for 30min to obtain a carbon nanotube hydrochloric acid solution, 0.2g of acetyl monoethanolamine was added to the carbon nanotube hydrochloric acid solution, and continued to disperse at 300rpm for 30min. The reaction temperature was controlled at 0℃, stirred for 1.5h and then allowed to stand for 2h; the obtained product was filtered and washed with distilled water and ethanol in sequence. After washing, it was vacuum dried at 75℃ to obtain acetyl monoethanolamine-modified carbon nanotubes;

[0046] S3. 15 g of polypropylene fiber, 37.5 g of ceramic fiber, and 37.5 g of steel fiber were weighed in a mass ratio, and 1.1 g of calcium carbonate was added to each of them. The fibers were crushed, passed through a 400-mesh sieve, washed with 10% dilute hydrochloric acid, and dried at 120 ° C for 3.5 h to obtain short fibers; the three short fibers were mixed and fed into a blender, 2 g of barium sulfate was added, and stirred for 45 seconds to obtain the composite fiber;

[0047] S4. 380g of cement, 108g of fly ash, 619g of sand, 1078g of stone, 8.3g of water reducer, 21.4g of hydrophobic rust inhibitor, 132g of water, 12g of modified carbon nanotubes, and 3g of composite fiber are mixed evenly to obtain crack-resistant concrete. The cement used in this embodiment is Yuexiu P.Ⅱ.42.5, the fly ash is Class II fly ash, the fineness is 14%, the water demand ratio is 98.5%, the loss on ignition is 2.25%, and the water reducer is a naphthalene-based water reducer.

[0048] Example 3

[0049] S1. 92g of water was heated to 55°C, 0.5g of formic acid was added while stirring and mixed thoroughly for 60 minutes, 0.2g of polydimethylsiloxane was added, and the mixture was stirred at 65°C for 12 hours to obtain a uniform mixture; 7g of nano-silica dispersion was added to the resulting mixture and stirred uniformly for 50 minutes, followed by 7g of triethanolamine and 1g of N,N-bis(hydroxyethyl)dodecylamide, and stirring was continued for 4 hours to obtain a hydrophobic rust inhibitor;

[0050] S2. At 10 ° C, add 20g of 68% concentrated HNO3 to a mixture of 0.3g carbon nanotubes and 0.6g NaNO3, stir for 60min, heat to 40 ° C and add 5g KMnO4, after stirring for 2.5 hours, 45g of water was added and the temperature was raised to 100℃ and stirred for another 2.5 hours; finally, 5g of 30% H2O2 solution was added, stirred for 20 minutes, cooled, washed with distilled water until neutral, and vacuum dried at 70℃ for 4 hours to obtain carboxylated carbon nanotubes; the carboxylated carbon nanotubes were added to 30g of 36.5% hydrochloric acid solution, dispersed at 400rpm for 40 minutes to obtain a carbon nanotube hydrochloric acid solution, 0.2g of acetyl monoethanolamine was added to the carbon nanotube hydrochloric acid solution, and continued to disperse at 400rpm for 40 minutes. The reaction temperature was controlled at 5℃, stirred for 2 hours, and then allowed to stand for 2.5 hours; the obtained product was filtered and washed with distilled water and ethanol in sequence. After washing, it was vacuum dried at 85℃ to obtain acetyl monoethanolamine-modified carbon nanotubes;

[0051] S3. 15 g of polypropylene fiber, 37.5 g of ceramic fiber, and 37.5 g of steel fiber were weighed in a mass ratio, and 1.5 g of calcium carbonate was added to each of them. The fibers were crushed, passed through a 500-mesh sieve, washed with 10% dilute hydrochloric acid, and dried at 130 ° C for 4 h to obtain short fibers. The three short fibers were mixed and fed into a blender, 3 g of barium sulfate was added, and stirred for 60 s to obtain the composite fiber.

[0052] S4. 420g of cement, 128g of fly ash, 669g of sand, 1128g of stone, 10.3g of water reducer, 21.4g of hydrophobic rust inhibitor, 145g of water, 12g of modified carbon nanotubes, and 3g of composite fiber were mixed to obtain crack-resistant concrete. The cement used in this embodiment is Yuexiu P.Ⅱ.42.5, the fly ash is Class II fly ash, the fineness is 14%, the water demand ratio is 98.5%, the loss on ignition is 2.25%, the water reducer is 3g of naphthalene-based water reducer, and 3.3g of polycarboxylic acid water reducer.

[0053] Example 4

[0054] The difference between Example 4 and Example 1 is that the mass of polydimethylsiloxane used in S1 of Example 4 is 0.3 g.

[0055] Example 5

[0056] The difference between Example 5 and Example 1 is that the mass of polydimethylsiloxane used in S1 of Example 5 is 0.4 g.

[0057] Example 6

[0058] The difference between Example 6 and Example 1 is that the mass of N,N-bishydroxyethyl dodecylamide used in S1 of Example 6 is 2 g.

[0059] Example 7

[0060] The difference between Example 7 and Example 1 is that the mass of N,N-bishydroxyethyl dodecylamide used in S1 of Example 7 is 3 g.

[0061] Example 8

[0062] The difference between Example 8 and Example 1 is that the mass of the carbon nanotubes used in S2 in Example 8 is 0.45 g.

[0063] Example 9

[0064] The difference between Example 9 and Example 1 is that the mass of the carbon nanotubes used in S2 of Example 9 is 0.6 g.

[0065] Example 10

[0066] The difference between Example 10 and Example 1 is that the mass of acetyl monoethanolamine used in S2 of Example 10 is 0.35 g.

[0067] Example 11

[0068] The difference between Example 11 and Example 1 is that the mass of acetyl monoethanolamine used in S2 of Example 11 is 0.5 g.

[0069] Example 12

[0070] The difference between Example 12 and Example 1 is that in Example 12, 15 g of polypropylene fiber, 40.5 g of ceramic fiber, and 40.5 g of steel fiber are used in S3.

[0071] Example 13

[0072] The difference between Example 13 and Example 1 is that in Example 13, 15 g of polypropylene fiber, 45 g of ceramic fiber, and 45 g of steel fiber are used in S3.

[0073] Example 14

[0074] The difference between Example 14 and Example 1 is that the water reducer used in S4 of Example 14 is 6.3 g of polycarboxylic acid water reducer.

[0075] Example 15

[0076] The difference between Example 15 and Example 1 is that the water reducer used in S4 of Example 15 is 6.3 g of sulfonate water reducer.

[0077] Example 16

[0078] The difference between Example 16 and Example 1 is that the water reducer used in S4 of Example 16 is 6.3 g of naphthalene-based water reducer.

[0079] Examples 17-22

[0080] The difference between Examples 17-22 and Example 1 is that the process parameters used in S4 of Examples 17-22 are different, as shown in Table 1:

[0081] Table 1 Process parameters used in S4 of Examples 17-22

[0082] Process parameters Hydrophobic rust inhibitor / g Modified carbon nanotubes / g Composite fiber / g Example 17 24.4 12 3 Example 18 27.4 12 3 Example 19 21.4 13.5 3 Example 20 21.4 15 3 Example 21 21.4 12 5 Example 22 21.4 12 7

[0083] Comparative Example

[0084] Comparative Example 1

[0085] The difference between Comparative Example 1 and Example 1 is that the mass of polydimethylsiloxane used in S1 of Comparative Example 4 is 0.1 g.

[0086] Comparative Example 2

[0087] The difference between Comparative Example 2 and Example 1 is that the mass of polydimethylsiloxane used in S1 in Comparative Example 2 is 0.5 g.

[0088] Comparative Example 3

[0089] The difference between Comparative Example 3 and Example 1 is that the mass of N,N-bishydroxyethyl dodecylamide used in S1 in Comparative Example 3 is 0.5 g.

[0090] Comparative Example 4

[0091] The difference between Comparative Example 4 and Example 1 is that the mass of N,N-bishydroxyethyl dodecylamide used in S1 of Comparative Example 4 is 4 g.

[0092] Comparative Example 5

[0093] The difference between Comparative Example 5 and Example 1 is that the mass of the carbon nanotubes used in S2 in Comparative Example 5 is 0.1 g.

[0094] Comparative Example 6

[0095] The difference between Comparative Example 6 and Example 1 is that the mass of the carbon nanotubes used in S2 in Comparative Example 6 is 0.8 g.

[0096] Comparative Example 7

[0097] The difference between Comparative Example 7 and Example 1 is that the mass of acetyl monoethanolamine used in S2 of Comparative Example 7 is 0.1 g.

[0098] Comparative Example 8

[0099] The difference between Comparative Example 8 and Example 1 is that the mass of acetyl monoethanolamine used in S2 of Comparative Example 8 is 0.6 g.

[0100] Comparative Example 9

[0101] The difference between Comparative Example 9 and Example 1 is that in Comparative Example 9, 15 g of polypropylene fiber, 30 g of ceramic fiber, and 30 g of steel fiber are used in S3.

[0102] Comparative Example 10

[0103] The difference between Comparative Example 10 and Example 1 is that in Comparative Example 10, 15 g of polypropylene fiber, 52.5 g of ceramic fiber, and 52.5 g of steel fiber are used in S3.

[0104] Comparative Example 11

[0105] The difference between Comparative Example 11 and Example 1 is that the water reducer used in S4 of Comparative Example 11 is sugar calcium water reducer.

[0106] Comparative Examples 12-17

[0107] The difference between Comparative Examples 12-17 and Example 1 is that the process parameters used in S4 of Comparative Examples 12-17 are different, as shown in Table 2:

[0108] Table 2 Process parameters used in S4 for comparative examples 12-17

[0109]

[0110]

[0111] Comparative Example 18

[0112] The difference between Comparative Example 18 and Example 1 is that the rust inhibitor used in S4 of Comparative Example 18 is ethanolamine.

[0113] Comparative Example 19

[0114] The difference between Comparative Example 19 and Example 1 is that Comparative Example 19 uses ordinary carbon nanotubes in S4.

[0115] Comparative Example 20

[0116] The difference between Comparative Example 20 and Example 1 is that the fiber used in S4 of Comparative Example 20 is steel fiber.

[0117] Performance testing

[0118] 1. The sulfate resistance and impermeability grade of the concrete prepared in Examples 1-22 and Comparative Examples 1-20 were tested using GB / T 50082-2009 “Test method for long-term performance and durability of ordinary concrete”.

[0119] 2. The slump of the concrete prepared in Examples 1-22 and Comparative Examples 1-20 was tested using GB / T 50080-2016 “Standard for Test Methods for Performance of Ordinary Concrete Mixtures”.

[0120] 3. The compressive strength of the concrete prepared in Examples 1-22 and Comparative Examples 1-20 was tested using GB / T 50081-2002 “Test methods for mechanical properties of ordinary concrete”.

[0121] The specific test results are shown in Table 3:

[0122] Table 3 Concrete performance test results

[0123]

[0124]

[0125]

[0126] It can be seen from the test results of Examples 1-3 that the process parameters of the concrete provided in this application can improve the sulfate resistance, impermeability grade, 28-day compressive strength and slump of the concrete, and within the parameter range provided in this application, the effect on the sulfate resistance, impermeability grade, 28-day compressive strength and slump of the concrete is small.

[0127] It can be seen from the test results of Examples 1, 4, 5 and Comparative Examples 1 and 2 that as the content of polydimethylsiloxane in the rust inhibitor increases, the strength loss rate of concrete after 150 sulfate dry-wet cycles becomes smaller, but when the mass of polydimethylsiloxane used to prepare the rust inhibitor reaches 0.4 g, the strength loss rate of concrete after 150 sulfate dry-wet cycles begins to increase; and the change in the mass of polydimethylsiloxane used to prepare the rust inhibitor has little effect on the impermeability grade, 28-day compressive strength and slump of the concrete.

[0128] It can be seen from the test results of Examples 1, 6, 7 and Comparative Examples 3 and 4 that as the content of N, N-bishydroxyethyl dodecylamide in the rust inhibitor increases, the strength loss rate of concrete after 150 sulfate dry-wet cycles becomes smaller. When the mass of N, N-bishydroxyethyl dodecylamide used to prepare the rust inhibitor reaches 3 g, the strength loss rate of concrete after 150 sulfate dry-wet cycles no longer changes; and the change in the mass of N, N-bishydroxyethyl dodecylamide used to prepare the rust inhibitor has little effect on the impermeability grade, 28-day compressive strength and slump of the concrete.

[0129] From the test results of Examples 1, 8, 9 and Comparative Examples 5 and 6, it can be seen that with the increase of the carbon nanotube content in the modified carbon nanotubes, the strength loss rate of the concrete after 150 sulfate dry-wet cycles gradually decreases, and the impermeability grade, 28-day compressive strength and slump increase accordingly. When the mass of the carbon nanotubes used to prepare the modified carbon nanotubes reaches 0.45g, the impermeability grade and slump of the concrete no longer change, the strength loss rate after 150 sulfate dry-wet cycles slightly decreases, and the 28-day compressive strength slightly increases; when the mass of the carbon nanotubes used to prepare the modified carbon nanotubes reaches 0.6g, the strength loss rate of the concrete after 150 sulfate dry-wet cycles and its 28-day compressive strength no longer change.

[0130] From the test results of Examples 1, 10, 11 and Comparative Examples 7 and 8, it can be seen that with the increase of the content of acetyl monoethanolamine in the modified carbon nanotubes, the strength loss rate of the concrete after 150 sulfate dry-wet cycles gradually decreases, and the impermeability grade, 28-day compressive strength and slump increase accordingly; when the mass of the carbon nanotubes used to prepare the modified carbon nanotubes reaches 0.35g, the strength loss rate and impermeability grade of the concrete after 150 sulfate dry-wet cycles no longer change, and the 28-day compressive strength and slump increase slightly; when the mass of the carbon nanotubes used to prepare the modified carbon nanotubes reaches 0.5g, the strength loss rate of the concrete after 150 sulfate dry-wet cycles begins to increase, and the 28-day compressive strength begins to decrease.

[0131] From the test results of Examples 1, 12, 13 and Comparative Examples 9 and 10, it can be seen that with the increase of the weight ratio of polypropylene fiber, ceramic fiber and steel fiber, the impermeability grade and compressive strength of concrete increase. When the weight ratio of polypropylene fiber, ceramic fiber and steel fiber reaches 1:3:3, the sulfate resistance, impermeability grade, 28-day compressive strength and slump do not change.

[0132] From the test results of Examples 1, 14, 15, 16 and Comparative Example 11, it can be seen that the types of water reducers provided in the present application can improve the sulfate resistance, impermeability grade, 28-day compressive strength and slump of the concrete, and have little effect on the sulfate resistance, impermeability grade, 28-day compressive strength and slump of the concrete of the present application.

[0133] From the test results of Examples 1, 17, 18 and Comparative Examples 12 and 13, it can be seen that with the increase of the content of the hydrophobic rust inhibitor, the 150 sulfate dry-wet cycle strength loss rate of the concrete gradually decreases, and the impermeability grade, 28-day compressive strength and slump all increase; however, when the content of the hydrophobic rust inhibitor exceeds 27.4 g, the 150 sulfate dry-wet cycle strength loss rate begins to increase again, and the impermeability grade, 28-day compressive strength and slump begin to decrease; from Comparative Example 18, it can be seen that the rust inhibitor provided in the present application is more conducive to improving the sulfate resistance, impermeability grade, 28-day compressive strength and slump of concrete than ordinary rust inhibitors.

[0134] From the test results of Examples 1, 19, 20 and Comparative Examples 14 and 15, it can be seen that with the increase of the content of modified nanotubes, the strength loss rate of concrete after 150 sulfate dry-wet cycles gradually decreases, and the impermeability grade, 28-day compressive strength and slump all increase; however, when the content of modified nanotubes exceeds 15g, the strength loss rate after 150 sulfate dry-wet cycles begins to increase again, and the impermeability grade, 28-day compressive strength and slump begin to decrease; from Comparative Example 19, it can be seen that the modified carbon nanotubes provided in the present application are more conducive to improving the sulfate resistance, impermeability grade, 28-day compressive strength and slump of concrete than ordinary carbon nanotubes.

[0135] It can be seen from the test results of Examples 1, 21, 22 and Comparative Examples 16 and 17 that with the increase of the composite fiber content, the 150 sulfate dry-wet cycle strength loss rate of the concrete gradually decreases, and the impermeability grade, 28-day compressive strength and slump all increase; when the composite fiber content reaches 5g, the 28-day compressive strength of the concrete begins to decrease, and when the composite fiber content reaches 7g, the 150 sulfate dry-wet cycle strength loss rate begins to increase, and the impermeability grade and slump begin to decrease; it can be seen from Comparative Example 20 that the composite fiber provided in the present application is more conducive to improving the sulfate resistance, impermeability grade, 28-day compressive strength and slump of the concrete than ordinary single fibers.

[0136] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A sulfate-resistant concrete, characterized in that: The raw materials include, by weight, 340-420 parts of cement, 88-128 parts of fly ash, 569-669 parts of sand, 1028-1128 parts of stone, 6.3-10.3 parts of water reducer, 21.4-27.4 parts of hydrophobic rust inhibitor, 118-145 parts of water, and 12-15 parts of modified carbon nanotubes; the hydrophobic rust inhibitor raw materials include the following components: 0.3-0.5 parts of formic acid, 0.2-0.4 parts of polydimethylsiloxane, 3-7 parts of nano-silicon dioxide, 3-7 parts of triethanolamine, 1-3 parts of N,N-bis(hydroxyethyl)dodecylamide, and 82-92 parts of water; The hydrophobic rust inhibitor is prepared by the following steps: S1. Heat 82-92 parts of water to 45-55 ° C, add 0.3-0.5 parts of formic acid while stirring and mix thoroughly, add 0.2-0.4 parts of polydimethylsiloxane, and stir to obtain a mixture; S2. 3-7 parts of the nano-silica dispersion were added to the mixture obtained in S1 and stirred evenly, followed by addition of 3-7 parts of triethanolamine and 1-3 parts of N, N-bis(hydroxyethyl)dodecylamide and continued stirring to obtain a hydrophobic rust inhibitor; The modified carbon nanotubes are prepared by the following steps: S1. To a mixture of 0.3-0.6 parts of carbon nanotubes and 0.3-0.6 parts of NaNO3 at -10-10°C, 15-20 parts of concentrated HNO3 were added, stirred, and heated to 30-40°C. 2-5 parts of KMnO4 were added, stirred, and 25-45 parts of water were added, and the temperature was raised to 80-100°C and stirred again. Finally, 2-5 parts of H2O2 solution were added, stirred, and then cooled. The mixture was washed with distilled water until neutral and dried in vacuo to obtain carboxylated carbon nanotubes. S2. Take carboxylated carbon nanotubes and add 20-30 parts of hydrochloric acid solution, and then evenly disperse 0.2-0.5 parts of acetyl monoethanolamine to the carbon nanotube hydrochloric acid solution, and evenly disperse the mixture. The reaction temperature was controlled at -5-5 ° C, stirred for 1-2h, and allowed to stand. S3. The product obtained in S2 is filtered, washed with distilled water and ethanol in sequence, and dried under vacuum to obtain acetyl monoethanolamine-modified carbon nanotubes.

2. The sulfate-resistant concrete according to claim 1, characterized in that: The sulfate-resistant concrete raw material also includes 3-7 parts of composite fibers; the composite fibers include: polypropylene fibers, ceramic fibers, and steel fibers, with a weight ratio of 1: (2.5-3): (2.5-3).

3. The sulfate-resistant concrete according to claim 1, characterized in that: The water reducer is a mixture of one or more of a naphthalene-based water reducer, a polycarboxylic acid-based water reducer, and a sulfonic acid-based water reducer.

4. A method for preparing sulfate-resistant concrete, characterized in that: Made by the following steps: 340-420 parts of cement, 88-128 parts of fly ash, 569-669 parts of sand, 1028-1128 parts of stone, 6.3-10.3 parts of water reducer, 21.4-27.4 parts of hydrophobic rust inhibitor, 118-145 parts of water, 12-15 parts of modified carbon nanotubes, and 3-7 parts of composite fibers are mixed uniformly to obtain crack-resistant concrete; The hydrophobic rust inhibitor is prepared by the following steps: S1. Heat 82-92 parts of water to 45-55 ° C, add 0.3-0.5 parts of formic acid while stirring and mix thoroughly, add 0.2-0.4 parts of polydimethylsiloxane, and stir to obtain a mixture; S2. 3-7 parts of the nano-silica dispersion were added to the mixture obtained in S1 and stirred evenly, followed by addition of 3-7 parts of triethanolamine and 1-3 parts of N, N-bis(hydroxyethyl)dodecylamide and continued stirring to obtain a hydrophobic rust inhibitor; The modified carbon nanotubes are prepared by the following steps: S1. To a mixture of 0.3-0.6 parts of carbon nanotubes and 0.3-0.6 parts of NaNO3 at -10-10°C, 15-20 parts of concentrated HNO3 were added, stirred, and heated to 30-40°C. 2-5 parts of KMnO4 were added, stirred, and 25-45 parts of water were added, and the temperature was raised to 80-100°C and stirred again. Finally, 2-5 parts of H2O2 solution were added, stirred, and then cooled. The mixture was washed with distilled water until neutral and dried in vacuo to obtain carboxylated carbon nanotubes. S2. Take carboxylated carbon nanotubes and add 20-30 parts of hydrochloric acid solution, and then evenly disperse 0.2-0.5 parts of acetyl monoethanolamine to the carbon nanotube hydrochloric acid solution, and evenly disperse the mixture. The reaction temperature was controlled at -5-5 ° C, stirred for 1-2h, and allowed to stand. S3. The product obtained in S2 is filtered, washed with distilled water and ethanol in sequence, and dried under vacuum to obtain acetyl monoethanolamine-modified carbon nanotubes.

5. The method for preparing sulfate-resistant concrete according to claim 4, wherein: The composite fiber is made by the following steps: Polypropylene fiber, ceramic fiber, and steel fiber are weighed in a weight ratio of 1: (2.5-3): (2.5-3), and 0.8-1.5 parts of a dispersant are added to each of them for mixing. Short fibers are obtained by crushing, sieving, acid washing, and drying. After the short fibers are mixed, 1-3 parts of a toughening agent are added and stirred to obtain the composite fiber.

6. The method for preparing sulfate-resistant concrete according to claim 5, wherein: The dispersant is calcium carbonate, and the toughening agent is barium sulfate.

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