Concrete expansive agent and preparation method thereof

Abstract

The invention relates to the technical field of concrete, and discloses a concrete expansive agent and a preparation method thereof.The concrete expansive agent is obtained by adding modified chitosan, carboxymethyl cellulose, calcium sulphoaluminate, quartz powder, sodium citrate and calcium oxide into a stirrer and stirring. The concrete expanding agent is obtained by adding the modified chitosan, the carboxymethyl cellulose, the calcium sulphoaluminate, the quartz powder, the sodium citrate and the calcium oxide into a stirrer and stirring. Chitosan in the modified chitosan can be used as an expanding agent of concrete, and reacts with a cement hydration product to generate gas and form tiny pores, so that the volume of the concrete is increased, the crack resistance of the concrete is improved, and the overall durability of the concrete is further improved; when siloxane reacts with calcium hydroxide and other components in cement, a certain volume expansion effect can be generated, and the expansion effect is beneficial to improving the compactness and durability of concrete.

Description

Technical Field

[0001] The 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, expansion agent is an important admixture, which is mainly used to improve the impermeability, crack resistance and durability of concrete. Traditional expansion agents mainly include sulfoaluminates, calcium oxides and composite expansion agents thereof. These expansion agents will have the problem of low expansion in the later stage during use, so how to avoid this phenomenon is the key to solving the problem. For example, patent CN107140864 discloses a concrete expansion agent and a preparation method thereof. The concrete expansion agent of the invention can prevent the cracking of large-volume concrete, improve the impermeability, have micro-expansion to prevent concrete shrinkage, 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 issues to be resolved

[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] (II) Technical solution

[0006] To achieve the above object, 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, aminoethylaminopropyl silsesquioxane and itaconic anhydride into a reaction vessel, introducing nitrogen, reacting at 65-80° C. for 8-15 hours, distilling under reduced pressure, and recrystallizing the product with toluene to obtain carboxyl-modified alkenyl silane;

[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 to dissolve, then adding a sodium hydroxide aqueous solution with a molar concentration of 4-5 mol / L, reacting at 65-80° C., and after completion, adding dilute hydrochloric acid dropwise for neutralization, concentrating to remove the solvent, filtering, washing and drying to obtain an intermediate 1;

[0010] (3) dissolving the carboxyl-modified alkenyl silane 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 h. After the reaction, cooling, filtering the solvent, and washing with ethanol to obtain intermediate 2;

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

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

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

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

[0015] Preferably, in the (4), the ratio of olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst 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. Add 5-10 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve, heat in a water bath at 60-85°C, add 5-8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, react for 6-9h, wash with anhydrous ethanol after the reaction, dry, dialyze, and concentrate to obtain quaternized chitosan;

[0018] S2. Add 6-9 parts by weight of quaternized chitosan and 7-13 parts by weight of acrylic acid to N,N-dimethylformamide solvent, stir evenly, then add 0.3-0.5 parts by weight of p-toluenesulfonic acid catalyst thereto, react at 90-115°C for 8-12h, and then perform vacuum distillation, filter and dry 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, stirring for 2-4 minutes, and obtaining the concrete expansion agent.

[0020] (III) Beneficial technical effects

[0021] The invention prepares the concrete expansion agent by adding modified chitosan, carboxymethyl cellulose, calcium sulphoaluminate, 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 further improving the overall durability of concrete; the quaternary ammonium salt groups contained therein can also be used as a concrete expansion agent and improve its durability; the cyclodextrin therein can significantly increase the density of concrete, thereby improving the mechanical properties, and cyclodextrin has a high degree of substitution, which further improves its mechanical properties; the siloxane therein can produce a certain volume expansion effect when reacting with components such as calcium hydroxide in cement, and 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) adding 4 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-di(bromomethyl)-1,3-propylene glycol to an acetone solvent, stirring to dissolve, then adding a 4 mol / L sodium hydroxide aqueous solution, reacting at 65° C. for 6 h, and then dropping dilute hydrochloric acid to neutralize, concentrating to remove the solvent, filtering, washing and drying to obtain an intermediate 1;

[0026] (3) dissolving the carboxyl-modified alkenyl silane and intermediate 1 in N,N-dimethylformamide solvent, and then adding 4-dimethylaminopyridine and N,N-dicyclohexylcarbodiimide, wherein the carboxyl-modified alkenyl silane, intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide are in a ratio of 0.8:1:0.01:0.02, and reacting at 110° C. for 20 h under reflux. After the reaction, cooling, filtering the solvent, and washing 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, 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, stirred evenly, and 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 into a stirrer 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, distilling under reduced pressure, and recrystallizing the product with toluene to obtain carboxyl-modified alkenyl silane;

[0033] (2) adding 8 parts by weight of β-cyclodextrin and 3 parts by weight of 2,2-di(bromomethyl)-1,3-propylene glycol to an acetone solvent, stirring to dissolve, then adding a 5 mol / L sodium hydroxide aqueous solution, reacting at 80° C. for 8 h, and then dropping dilute hydrochloric acid to neutralize, concentrating to remove the solvent, filtering, washing and drying to obtain an 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 h under reflux. After the reaction, cooling, filtering the solvent, and washing 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, stirring evenly, then adding 0.5 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 115° C. for 12 hours, 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, stirred evenly, and 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, reacted at 115°C for 15h, cooled to room temperature after reaction, 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 into a stirrer 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, distilling under reduced pressure, and recrystallizing the product with toluene to obtain carboxyl-modified alkenyl silane;

[0041] (2) adding 6 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-di(bromomethyl)-1,3-propylene glycol to an acetone solvent, stirring to dissolve, then adding a 4 mol / L sodium hydroxide aqueous solution, reacting at 75° C. for 7 h, and then dropping dilute hydrochloric acid to neutralize, concentrating to remove the solvent, filtering, washing and drying to obtain an 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, cooling, filtering the solvent, and washing 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, stirring evenly, then adding 0.4 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 100° C. for 10 hours, 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, stirred evenly, and 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 into a stirrer 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) adding 4 parts by weight of β-cyclodextrin and 2 parts by weight of 2,2-di(bromomethyl)-1,3-propylene glycol to an acetone solvent, stirring to dissolve, then adding a 4 mol / L sodium hydroxide aqueous solution, reacting at 65° C. for 6 h, and then dropping dilute hydrochloric acid to neutralize, concentrating to remove the solvent, filtering, washing and drying to obtain an 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 h under reflux. After the reaction, cooling, filtering the solvent, and washing 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, stirring evenly, then adding 0.4 parts by weight of p-toluenesulfonic acid catalyst thereto, reacting at 100° C. for 10 hours, 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, stirred evenly, and 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 into a stirrer 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 method for the limited expansion rate and the test method for the compressive strength of mortar specified in GB / T23439-2017 "Concrete Expansion Agent", mortar specimens were prepared to test the limited expansion rate after curing in water for 7 days and in air for 21 days, and the compressive strength of the mortar specimens at 7 days and 28 days of curing was tested. The results of the limited 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] It can be seen from Table 1 that 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] It can be seen from Table 2 that 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 only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. 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 sulphoaluminate, 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.

2. The concrete expansion agent according to claim 1, characterized in that The preparation method of the modified chitosan is: (1) adding toluene solvent, aminoethylaminopropyl silsesquioxane and itaconic anhydride into a reaction vessel, introducing nitrogen, reacting at 65-80° C. for 8-15 hours, distilling under reduced pressure, and recrystallizing the product with toluene to obtain carboxyl-modified alkenyl silane; (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 to dissolve, then adding a sodium hydroxide aqueous solution with a molar concentration of 4-5 mol / L, reacting at 65-80° C., and after completion, adding dilute hydrochloric acid dropwise for neutralization, concentrating to remove the solvent, filtering, washing and drying to obtain an intermediate 1; (3) dissolving the carboxyl-modified alkenyl silane 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 h. After the reaction, cooling, filtering the solvent, and washing with ethanol to obtain intermediate 2; (4) Under a nitrogen atmosphere, olefinated chitosan, intermediate 2, and acrylic acid are added to a reactor and stirred evenly. Azobisisobutyronitrile catalyst is continuously added thereto and reacted at 90-115° C. for 12-15 h. After the reaction is completed, the reaction is cooled to room temperature, washed with deionized water, and dried to obtain modified chitosan.

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

5.

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

5. The concrete expansion agent according to claim 2, characterized in that: The carboxyl-modified alkenyl silane, the intermediate 1, 4-dimethylaminopyridine, and N,N-dicyclohexylcarbodiimide in (3) are 0.8-1.1:1:0.01-0.03:0.02-0.

04.

6. The concrete expansion agent according to claim 2, characterized in that: The olefinated chitosan, intermediate 2, acrylic acid, and azobisisobutyronitrile catalyst 1 in (4): 1.1-1.5:1.2-1.4:0.02-0.03。 7. The concrete expansion agent according to claim 2, characterized in that: The preparation method of olefinated chitosan in (4) is as follows: S1. Add 5-10 parts by weight of chitosan to dimethyl sulfoxide solvent to dissolve, heat in a water bath at 60-85°C, add 5-8 parts by weight of 2,3-epoxypropyltrimethylammonium chloride at constant pressure, react for 6-9h, wash with anhydrous ethanol after the reaction, dry, dialyze, and concentrate to obtain quaternized chitosan; S2. Add 6-9 parts by weight of quaternized chitosan and 7-13 parts by weight of acrylic acid to N,N-dimethylformamide solvent, stir evenly, then add 0.3-0.5 parts by weight of p-toluenesulfonic acid catalyst thereto, react at 90-115°C for 8-12h, and then perform vacuum distillation, filter and dry to obtain olefinated chitosan.

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

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