A concrete expansion agent and preparation method thereof

Abstract

The present invention relates to the field of concrete technology and discloses a concrete expansion agent and a preparation method thereof. Modified chitosan, carboxymethyl cellulose, calcium sulfoaluminate, quartz powder, sodium citrate, and calcium oxide are added to a blender and stirred to obtain the concrete expansion agent. The present invention provides a concrete expansion agent by adding modified chitosan, carboxymethyl cellulose, calcium sulfoaluminate, quartz powder, sodium citrate, and calcium oxide to a blender and stirring. The chitosan in the modified chitosan can be used as an expansion agent for concrete. It reacts with cement hydration products to generate gas, forming micropores, thereby increasing the volume of the concrete, improving its crack resistance, and further enhancing the overall durability of the concrete. The siloxane in the modified chitosan can produce a certain volume expansion effect when reacting with components such as calcium hydroxide in the cement. This expansion effect helps improve the density and durability of the concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, in particular to a concrete expansion agent and a preparation method thereof. Background Art

[0002] In concrete construction projects, expansive agent is an important admixture, mainly used to improve the impermeability, crack resistance and durability of concrete. Traditional expansive agents mainly include sulfoaluminates, calcium oxides and composite expansive agents thereof. During the use of these expansive agents, the problem of low expansion in the later stage will occur. Therefore, how to avoid this phenomenon is the key to solving the problem. For example, patent CN107140864 discloses a concrete expansive agent and a preparation method thereof. The concrete expansive agent of the invention can prevent the cracking of large-volume concrete, improve the impermeability, have micro-expansion to prevent concrete shrinkage, and can be waterproof, anti-seepage and crack-resistant in engineering construction, but the expansion effect in the later stage is poor. Summary of the Invention

[0003] (1) Technical problems solved

[0004] In view of the deficiencies in the prior art, the present invention provides a concrete expansion agent and a preparation method thereof, which can give full play to the strengthening effect of the expansion agent on concrete and improve the durability of concrete.

[0005] (2) Technical solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a concrete expansion agent comprising the following components by weight: 6-8 parts by weight of modified chitosan, 12-16 parts by weight of carboxymethyl cellulose, 30-40 parts by weight of calcium sulfoaluminate, 25-40 parts by weight of quartz powder, 6-8 parts by weight of sodium citrate, and 25-40 parts by weight of calcium oxide.

[0007] Preferably, the preparation method of the modified chitosan is:

[0008] (1) adding toluene solvent, aminoethylaminopropylsilsesquioxane, and itaconic anhydride to a reaction vessel, introducing nitrogen, reacting at 65-80° C. for 8-15 hours, and distilling under reduced pressure. The product is recrystallized from toluene to obtain a carboxyl-modified alkenylsilane;

[0009] (2) adding 4-8 parts by weight of β-cyclodextrin and 2-3 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stirring and dissolving, then continuously adding a sodium hydroxide aqueous solution with a molar concentration of 4-5 mol / L, reacting at 65-80° C., and then dropping dilute hydrochloric acid to neutralize the mixture, concentrating to remove the solvent, filtering, washing, and drying to obtain an intermediate 1;

[0010] (3) dissolving the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, and reflux at 110-130°C for 20-25 hours. After the reaction, cooling, filtering the solvent, and washing with ethanol to obtain intermediate 2;

[0011] (4) Under nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto and the reaction was carried out at 90-115° C. for 12-15 h. After the reaction was completed, the reaction mixture was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

[0012] Preferably, the mass ratio of aminoethylaminopropylsilsesquioxane to itaconic anhydride in (1) is 1:0.3-0.5.

[0013] Preferably, the reaction time in (2) is 6-8 hours.

[0014] Preferably, the ratio of carboxyl-modified alkenylsilane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide in (3) is 0.8-1.1:1:0.01-0.03:0.02-0.04.

[0015] Preferably, the ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst in (4) is 1:1.1-1.5:1.2-1.4:0.02-0.03.

[0016] Preferably, the preparation method of the olefinated chitosan in (4) is:

[0017] S1. 5-10 parts by weight of chitosan was dissolved in dimethyl sulfoxide solvent, heated in a water bath at 60-85 ° C, 5-8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride was added at constant pressure, and the reaction was allowed to proceed for 6-9h. After the reaction, the mixture was washed with anhydrous ethanol, dried, dialyzed, and concentrated to obtain quaternized chitosan.

[0018] S2. 6-9 parts by weight of quaternized chitosan and 7-13 parts by weight of acrylic acid are added to N,N-dimethylformamide solvent and stirred evenly. Then, 0.3-0.5 parts by weight of p-toluenesulfonic acid catalyst is added thereto. The reaction is carried out at 90-115° C. for 8-12 hours. After the reaction, the reaction is carried out by vacuum distillation, filtration and drying to obtain olefinated chitosan.

[0019] Preferably, the preparation method of the concrete expansion agent is: adding modified chitosan, carboxymethyl cellulose, calcium sulfoaluminate, quartz powder, sodium citrate, and calcium oxide into a stirrer, and stirring for 2-4 minutes to obtain the concrete expansion agent.

[0020] (3) Beneficial technical effects

[0021] The invention prepares the concrete expansion agent by adding modified chitosan, carboxymethyl cellulose, calcium sulfoaluminate, quartz powder, sodium citrate and calcium oxide into a stirrer and stirring the mixture.

[0022] The chitosan in the modified chitosan can be used as an expansion agent for concrete. It generates gas by reacting with cement hydration products to form tiny pores, thereby increasing the volume of concrete, improving its crack resistance, and thus improving the overall durability of concrete; the quaternary ammonium salt groups contained in it can also be used as a concrete expansion agent and improve its durability; the cyclodextrin in it can significantly increase the density of concrete, thereby improving its mechanical properties, and cyclodextrin has a high degree of substitution, which further improves its mechanical properties; the siloxane in it can produce a certain volume expansion effect when reacting with components such as calcium hydroxide in cement. This expansion effect helps to improve the density and durability of concrete. DETAILED DESCRIPTION

[0023] Example 1

[0024] (1) adding toluene solvent, aminoethylaminopropyl silsesquioxane, and itaconic anhydride into a reaction vessel, wherein the mass ratio of aminoethylaminopropyl silsesquioxane to itaconic anhydride is 1:0.3, introducing nitrogen, reacting at 65° C. for 8 h, and distilling under reduced pressure. The product is recrystallized from toluene to obtain carboxyl-modified alkenyl silane;

[0025] (2) Add 4 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stir and dissolve, then continue to add a 4 mol / L sodium hydroxide aqueous solution, react at 65° C. for 6 h, and then dropwise add dilute hydrochloric acid to neutralize, concentrate to remove the solvent, filter, wash and dry to obtain intermediate 1;

[0026] (3) dissolving the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, and then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, wherein the carboxyl-modified alkenylsilane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide are in a ratio of 0.8:1:0.01:0.02, and reflux at 110°C for 20 hours. After the reaction, the reaction is cooled, the solvent is filtered, and the product is washed with ethanol to obtain intermediate 2;

[0027] (4) adding 5 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 60° C., adding 5 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 6 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan;

[0028] (5) adding 6 parts by weight of quaternized chitosan and 7 parts by weight of acrylic acid to N,N-dimethylformamide solvent and stirring evenly, then adding 0.3 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 90° C. for 8 h, and then distilling under reduced pressure, filtering and drying to obtain olefinated chitosan;

[0029] (6) Under a nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto in a ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst of 1:1.1:1.2:0.02. The reaction was carried out at 90°C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

[0030] (7) 6 parts by weight of modified chitosan, 12 parts by weight of carboxymethyl cellulose, 30 parts by weight of calcium sulfoaluminate, 25 parts by weight of quartz powder, 6 parts by weight of sodium citrate, and 25 parts by weight of calcium oxide were added to a blender and stirred for 2 minutes to obtain a concrete expansion agent.

[0031] Example 2

[0032] (1) adding toluene solvent, aminoethylaminopropyl silsesquioxane, and itaconic anhydride into a reaction vessel, wherein the mass ratio of aminoethylaminopropyl silsesquioxane to itaconic anhydride is 1:0.5, introducing nitrogen, reacting at 80° C. for 15 h, and distilling under reduced pressure. The product is recrystallized from toluene to obtain carboxyl-modified alkenyl silane;

[0033] (2) Add 8 parts by weight of β-cyclodextrin and 3 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stir and dissolve, then continue to add a 5 mol / L sodium hydroxide aqueous solution, react at 80° C. for 8 h, and then dropwise add dilute hydrochloric acid to neutralize, concentrate to remove the solvent, filter, wash and dry to obtain intermediate 1;

[0034] (3) dissolving the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, and then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, wherein the carboxyl-modified alkenylsilane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide are in a ratio of 1.1:1:0.03:0.04, and reacting at 130°C for 25 hours under reflux. After the reaction, the reaction is cooled, the solvent is filtered, and the product is washed with ethanol to obtain intermediate 2;

[0035] (4) adding 10 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 85° C., adding 8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 9 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan;

[0036] (5) adding 9 parts by weight of quaternized chitosan and 13 parts by weight of acrylic acid to N,N-dimethylformamide solvent and stirring evenly, then adding 0.5 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 115° C. for 12 h, and then distilling under reduced pressure, filtering and drying to obtain olefinated chitosan;

[0037] (6) Under a nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto in a ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst of 1:1.5:1.4:0.03. The reaction was carried out at 115°C for 15 h. After the reaction was completed, the reaction was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

[0038] (7) 8 parts by weight of modified chitosan, 16 parts by weight of carboxymethyl cellulose, 40 parts by weight of calcium sulfoaluminate, 40 parts by weight of quartz powder, 8 parts by weight of sodium citrate, and 40 parts by weight of calcium oxide were added to a blender and stirred for 4 minutes to obtain a concrete expansion agent.

[0039] Example 3

[0040] (1) adding toluene solvent, aminoethylaminopropyl silsesquioxane, and itaconic anhydride into a reaction vessel, wherein the mass ratio of aminoethylaminopropyl silsesquioxane to itaconic anhydride is 1:0.4, introducing nitrogen, reacting at 75° C. for 12 h, and distilling under reduced pressure. The product is recrystallized from toluene to obtain a carboxyl-modified alkenyl silane;

[0041] (2) Add 6 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stir and dissolve, then continue to add a 4 mol / L sodium hydroxide aqueous solution, react at 75° C. for 7 h, and then dropwise add dilute hydrochloric acid to neutralize, concentrate to remove the solvent, filter, wash and dry to obtain intermediate 1;

[0042] (3) dissolving the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, and then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, wherein the carboxyl-modified alkenylsilane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide are in a ratio of 0.9:1:0.02:0.03, and reacting at 120°C for 22 hours under reflux. After the reaction, the reaction is cooled, the solvent is filtered, and the product is washed with ethanol to obtain intermediate 2;

[0043] (4) adding 8 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 75° C., adding 6 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 8 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan;

[0044] (5) adding 7 parts by weight of quaternized chitosan and 10 parts by weight of acrylic acid to N,N-dimethylformamide solvent and stirring evenly, then adding 0.4 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 100° C. for 10 h, and then distilling under reduced pressure, filtering and drying to obtain olefinated chitosan;

[0045] (6) Under a nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto in a ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst of 1:1.3:1.2:0.02. The reaction was carried out at 95°C for 14 h. After the reaction was completed, the reaction was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

[0046] (7) 7 parts by weight of modified chitosan, 14 parts by weight of carboxymethyl cellulose, 35 parts by weight of calcium sulfoaluminate, 28 parts by weight of quartz powder, 7 parts by weight of sodium citrate, and 30 parts by weight of calcium oxide were added to a blender and stirred for 3 minutes to obtain a concrete expansion agent.

[0047] Example 4

[0048] (1) adding toluene solvent, aminoethylaminopropyl silsesquioxane, and itaconic anhydride into a reaction vessel, wherein the mass ratio of aminoethylaminopropyl silsesquioxane to itaconic anhydride is 1:0.3, introducing nitrogen, reacting at 65° C. for 8 h, and distilling under reduced pressure. The product is recrystallized from toluene to obtain carboxyl-modified alkenyl silane;

[0049] (2) Add 4 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stir and dissolve, then continue to add a 4 mol / L sodium hydroxide aqueous solution, react at 65° C. for 6 h, and then dropwise add dilute hydrochloric acid to neutralize, concentrate to remove the solvent, filter, wash and dry to obtain intermediate 1;

[0050] (3) dissolving the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, and then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, wherein the carboxyl-modified alkenylsilane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide are in a ratio of 1.1:1:0.03:0.04, and reacting at 130°C for 25 hours under reflux. After the reaction, the reaction is cooled, the solvent is filtered, and the product is washed with ethanol to obtain intermediate 2;

[0051] (4) adding 10 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve it, heating it in a water bath at 85° C., adding 8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, reacting it for 9 hours, washing it with anhydrous ethanol after the reaction, drying it, dialyzing it, and concentrating it to obtain quaternized chitosan;

[0052] (5) adding 7 parts by weight of quaternized chitosan and 10 parts by weight of acrylic acid to N,N-dimethylformamide solvent and stirring evenly, then adding 0.4 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 100° C. for 10 h, and then distilling under reduced pressure, filtering and drying to obtain olefinated chitosan;

[0053] (6) Under a nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto in a ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst of 1:1.3:1.2:0.02. The reaction was carried out at 95°C for 14 h. After the reaction was completed, the reaction was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

[0054] (7) 7 parts by weight of modified chitosan, 14 parts by weight of carboxymethyl cellulose, 35 parts by weight of calcium sulfoaluminate, 28 parts by weight of quartz powder, 7 parts by weight of sodium citrate, and 30 parts by weight of calcium oxide were added to a blender and stirred for 3 minutes to obtain a concrete expansion agent.

[0055] Comparative Example 1

[0056] Compared with Example 4, this comparative example differs in that chitosan is used instead of modified chitosan.

[0057] Referring to the test methods for restricted expansion rate and compressive strength of mortar specified in GB / T 23439-2017, "Concrete Expansion Agents," mortar specimens were prepared and tested for restricted expansion rate after 7 days of curing in water and 21 days of curing in air. The compressive strength of the mortar specimens was also tested at 7 and 28 days of curing. The results of the restricted expansion rate test are shown in Table 1, and the results of the compressive strength test are shown in Table 2.

[0058] Table 1: Limiting expansion rate tests.

[0059]

[0060] As can be seen from Table 1, Examples 1-4 of the present invention have better restricted expansion ratios than Comparative Example 1.

[0061] Table 2: Compressive strength test.

[0062] project 7d compressive strength (Mpa) 28d compressive strength (Mpa) Example 1 32.4 51.4 Example 2 33.6 52.7 Example 3 31.7 51.4 Example 4 30.8 50.9 Comparative Example 1 25.6 44.8

[0063] As can be seen from Table 2, Examples 1-4 of the present invention have better compressive strength than Comparative Example 1.

[0064] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A concrete expansion agent, characterized in that The invention comprises the following components by weight: 6-8 parts by weight of modified chitosan, 12-16 parts by weight of carboxymethyl cellulose, 30-40 parts by weight of calcium sulfoaluminate, 25-40 parts by weight of quartz powder, 6-8 parts by weight of sodium citrate, and 25-40 parts by weight of calcium oxide; The preparation method of the modified chitosan is: (1) Add toluene solvent, aminoethylaminopropyl silsesquioxane, and itaconic anhydride to a reaction vessel, introduce nitrogen, react at 65-80°C for 8-15 hours, and distill under reduced pressure. The product is recrystallized from toluene to obtain carboxyl-modified alkenyl silane; (2) Add 4-8 parts by weight of β-cyclodextrin and 2-3 parts by weight of 2,2-bis(bromomethyl)-1,3-propylene glycol to an acetone solvent, stir and dissolve, then continue to add a sodium hydroxide aqueous solution with a molar concentration of 4-5 mol / L, react at 65-80°C, add dilute hydrochloric acid dropwise to neutralize, concentrate to remove the solvent, filter, wash and dry to obtain intermediate 1; (3) Dissolve the carboxyl-modified alkenylsilane and intermediate 1 in N,N-dimethylformamide solvent, then add 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, and reflux at 110-130°C for 20-25 hours. After the reaction, cool, filter the solvent, and wash with ethanol to obtain intermediate 2; (4) Under nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid were added to the reactor and stirred evenly. Azobisisobutyronitrile catalyst was added thereto and the reaction was carried out at 90-115°C for 12-15 hours. After the reaction, the mixture was cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

2. The concrete expansion agent according to claim 1, characterized in that The mass ratio of aminoethylaminopropylsilsesquioxane to itaconic anhydride in (1) is 1:0.3-0.

5.

3. The concrete expansion agent according to claim 1, characterized in that The reaction time in (2) is 6-8h.

4. The concrete expansion agent according to claim 1, characterized in that The ratio of carboxyl modified alkenylsilane, intermediate 1,4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide in (3) is 0.8-1.1:1:0.01-0.03:0.02-0.

04.

5. The concrete expansion agent according to claim 1, characterized in that The ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst in (4) is 1:1.1-1.5:1.2-1.4:0.02-0.

03.

6. The concrete expansion agent according to claim 1, characterized in that The preparation method of the olefinated chitosan in (4) is as follows: S1. 5-10 parts by weight of chitosan was dissolved in dimethyl sulfoxide solvent, heated in a water bath at 60-85 ° C, 5-8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride was added at constant pressure, and the reaction was allowed to proceed for 6-9h. After the reaction, the mixture was washed with anhydrous ethanol, dried, dialyzed, and concentrated to obtain quaternized chitosan. S2. 6-9 parts by weight of quaternized chitosan and 7-13 parts by weight of acrylic acid are added to N,N-dimethylformamide solvent and stirred evenly. Then, 0.3-0.5 parts by weight of p-toluenesulfonic acid catalyst is added thereto. The reaction is carried out at 90-115° C. for 8-12 hours. After the reaction, the reaction is carried out by vacuum distillation, filtration and drying to obtain olefinated chitosan.

7. A method for preparing a concrete expansion agent according to any one of claims 1 to 6, characterized in that: The preparation method of the concrete expansion agent comprises the following steps: adding modified chitosan, carboxymethyl cellulose, calcium sulfoaluminate, quartz powder, sodium citrate and calcium oxide into a stirrer, and stirring for 2-4 minutes to obtain the concrete expansion agent.

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