CN112299745B - Slow-release concrete curing agent and preparation method and application thereof - Google Patents
Slow-release concrete curing agent and preparation method and application thereof Download PDFInfo
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- CN112299745B CN112299745B CN202011146692.2A CN202011146692A CN112299745B CN 112299745 B CN112299745 B CN 112299745B CN 202011146692 A CN202011146692 A CN 202011146692A CN 112299745 B CN112299745 B CN 112299745B
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
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Abstract
The invention discloses a slow-release concrete curing agent, which is a microcapsule prepared by taking divinylbenzene-sodium carboxymethylcellulose copolymerization modified nano vermiculite dispersion liquid as a capsule core and hollow silica particles as capsule wall materials; the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid is prepared by compounding divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite, hydrolyzed polymaleic anhydride and water serving as raw materials. The slow-release curing agent can slowly release curing moisture in concrete, provides better support for later strength increase of the concrete, can exert better curing effect on the whole age of the concrete, and the microcapsules after water release play a certain limiting role in self-shrinkage of a concrete structure, reduce cracks caused by the self-shrinkage of the concrete structure and improve the durability of the concrete structure; and the related preparation method is simple, the maintenance operation is simple and easy to implement, and the method is suitable for popularization and application.
Description
Technical Field
The invention belongs to the technical field of additives, and particularly relates to a slow-release concrete curing agent as well as a preparation method and application thereof.
Background
The performance of the concrete as one of the most used building materials in the building engineering depends on the composition and proportion of raw materials, more of the concrete is related to later maintenance, and if the concrete is not maintained timely after construction, the water in the concrete is evaporated to the outside through capillary pores of a system, so that the hydration of a cementing material is insufficient, hydration products are reduced, and further, the performance of the concrete is reduced. Therefore, curing is critical to the development of concrete properties.
Traditional concrete curing modes mainly comprise water curing, steam curing, landfill curing, plastic film covering and the like, the curing modes are time-consuming, labor-consuming and energy-consuming, the curing quality is difficult to control, and the requirements of modern high-rise and large-scale buildings and building engineering in arid water-deficient areas cannot be met. The curing agent curing is divided into external curing and internal curing at present, wherein the external curing is to mix related chemical film forming agents after concrete construction or in a concrete mixture, chemical substances with film forming property and permeability are formed on the surface layer of the concrete mixture, and the substances form a uniform and continuous compact film in a short time, so that the evaporation of water in the concrete is inhibited, and the full hydration of a cementing material is promoted.
At present, domestic internal curing agents mainly comprise super absorbent resin, water-absorbing ceramsite and water-retaining additive, and the aim of curing is achieved mainly by maintaining the internal water of concrete in the early stage. However, the internal curing agent has short water retention time and rapid water loss within 72 hours, cannot meet the requirement of 7-day curing in actual engineering, and is limited in engineering application. Therefore, further development of a concrete internal curing agent which has good storage stability, is beneficial to improving various performances of concrete after use, and has small influence on the ecological environment after use is a problem to be solved in the technical field of concrete.
Disclosure of Invention
Aiming at the defects in the prior art, the invention mainly aims to provide the slow-release concrete curing agent which is a microcapsule prepared by taking the copolymerization modified nano vermiculite dispersion liquid as a capsule core and taking the silica particles as capsule wall materials, has good curing effect on the whole age of concrete when being applied to the concrete, and is beneficial to further improving the strength of the concrete.
In order to achieve the purpose, the invention adopts the technical scheme that:
a slow-release concrete curing agent is a microcapsule which is prepared by taking Divinylbenzene (DVB) -sodium carboxymethylcellulose (CMC-Na) copolymerization modified nano vermiculite dispersion liquid as a capsule core and silicon dioxide particles as capsule wall materials; the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid is prepared by compounding divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite, hydrolyzed polymaleic anhydride and water serving as raw materials.
In the scheme, the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid comprises, by weight, 10-20 parts of divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite, 2-3 parts of hydrolyzed polymaleic anhydride (HPMA) and 80-90 parts of water; the preparation method comprises the steps of mixing divinylbenzene-sodium carboxymethyl cellulose copolymer modified nano vermiculite, hydrolyzed polymaleic anhydride and water, and stirring under the conditions of ultraviolet irradiation and protective atmosphere.
In the scheme, the stirring treatment speed is 240-280rpm, and the time is 25-35min
In the scheme, the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite is prepared by mixing nano vermiculite with sodium carboxymethylcellulose and divinylbenzene, and performing polymerization reaction, washing, drying and crushing (600-900 nm) under the oxygen-free condition and the initiator condition.
In the scheme, the mass ratio of the nano vermiculite to the sodium carboxymethylcellulose to the divinyl benzene is (30-50) to (30-40) to (20-30).
In the scheme, the molecular weight of the sodium carboxymethyl cellulose is 90000-110000.
In the scheme, the polymerization reaction temperature is 30-40 ℃, and the reaction time is 8-15 min.
In the scheme, the initiator is ammonium sulfate, and the dosage of the initiator is 0.1-0.3% of the mass sum of the sodium carboxymethyl cellulose and the divinylbenzene.
In the scheme, the preparation method of the nano vermiculite comprises the following steps: drying and dehydrating the vermiculite to constant weight at the temperature of 100-110 ℃; then cooling and crushing to the particle size of 200-300 nm.
In the scheme, the crushing step is to use a nanometer high-voltage pulse crusher for electric impact.
In the scheme, the preparation method of the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite specifically comprises the following steps:
1) adding carboxymethyl cellulose into a four-neck flask under the condition of ice-water bath, adding NaOH under the condition of stirring, and controlling the neutralization degree to be 70-90% (the calculation formula of the neutralization degree is as follows: mNaOH =40*MCarboxymethyl celluloseNeutralization degree/240) to obtain sodium carboxymethylcellulose (molecular weight of 9000-110000);
2) adding Divinylbenzene (DVB) into the sodium carboxymethylcellulose obtained in the step 1) and uniformly stirring;
3) adding nano vermiculite, adding an initiator under the conditions of an oxygen-free environment and a water bath, and carrying out stirring reaction (graft polymerization reaction); stopping stirring when the viscosity is increased to be difficult to stir, continuously introducing nitrogen, and taking out the obtained reactant when the obtained reactant is viscous colloid; soaking and washing the obtained reactant by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
4) drying the product obtained in the step 3) to constant weight, cooling to room temperature, and crushing to obtain the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite with the particle size of 600-900 nm.
In the scheme, the drying temperature in the step 4) is 100-110 ℃.
The preparation method of the slow-release concrete curing agent comprises the following steps:
1) dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) in an alcohol water solution, and uniformly mixing to obtain a mixed solution I;
2) reacting NH3·H2Adding O and divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid into the mixed liquid I, mechanically stirring for 20-30min at the temperature of 30-40 ℃ and the rotating speed of 200-300rpm, dropwise adding Tetraethoxysilane (TEOS), and continuously stirring for 7.5-8.5h to obtain suspension liquid II;
3) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
In the scheme, the mass ratio of the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid to the tetraethoxysilane is (70-80) to (5-7).
In the above scheme, the hexadecyl trimethyl ammonium bromide and NH3·H2The mass ratio of O to tetraethoxysilane is (2-4) to (10-12) to (5-7).
In the scheme, the volume ratio of ethanol to water in the alcohol-water solution is 1 (1.5-2.5); preferably 1: 2.
Compared with the prior art, the invention has the following beneficial effects:
1) according to the invention, the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid is loaded in the microcapsule, so that the obtained slow-release curing agent can slowly release curing moisture in the concrete, provides better support for later strength increase of the concrete, and can exert better curing effect on the concrete in the whole age period;
2) in the using process of the concrete, the modified vermiculite after slow water release can further generate hydration reaction, so that the strength of the concrete is improved, and the mechanical property of the obtained concrete is ensured;
3) the slow-release concrete curing agent can be directly doped into a concrete mixture to realize long-acting curing of concrete, and the related curing method is simple and convenient to operate and is suitable for popularization and application.
4) Compared with the traditional internal maintenance method, the method has higher long-term effect on the humidity inside the concrete structure, and the maintenance time can reach about 10 days when the humidity is more than 75%; the microcapsules after water release have a certain limiting effect on the self-shrinkage of the concrete structure, so that cracks caused by the self-shrinkage are reduced, and the durability of the concrete structure is further improved.
Drawings
FIG. 1 is an SEM photograph of the slow-release type concrete curing agent obtained in example 4.
FIG. 2 is an SEM photograph of the slow-release type concrete curing agent obtained in comparative example 1.
FIG. 3 is an SEM photograph of the slow-release type concrete curing agent obtained in comparative example 2.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.
In the following examples, the adopted carboxymethyl cellulose is provided for the ford chemical reagent factory in Tianjin, sodium hydroxide is provided for the maotan chemical reagent factory in Tianjin, divinylbenzene is provided for the repeated fine research institute in Tianjin, vermiculite is provided for the maotan ore products company Limited in Shijiazhuang, the specification is 800 meshes, ammonium persulfate is provided for the ford chemical reagent factory in Tianjin, hydrolyzed polymaleic anhydride is provided for the Delhi chemical industry Co., Ltd. in Guangzhou, hexadecyl trimethyl ammonium bromide is provided for the Tianjin Mimi chemical reagent company Limited, and ethyl orthosilicate is provided for the Tianjin Komi chemical reagent Co., Ltd. The purity of the chemical agents is analytical purity.
The ball milling step described in the examples below employs a nano high pressure pulse mill.
The test method of the water absorption rate in the following examples is a measuring cylinder method, a slow-release concrete curing agent and water are added into a measuring cylinder, and the water absorption rate is determined according to the mass ratio of the height of water reduction to a dry curing agent; the humidity inside the concrete structure is measured by adopting a pre-embedded humidity sensor.
In the following examples, the nano vermiculite is obtained by nano surface activation of vermiculite, and the specific steps are as follows: drying and dehydrating vermiculite at 105 ℃ to constant weight; then cooling in a drying dish, weighing 10g of dried vermiculite, putting into a nano high-pressure pulse grinder, and carrying out electric shock grinding to obtain the nano surface activated vermiculite powder with the particle size of 250 nm.
Example 1
A divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite comprises the following steps:
1) adding 40g of carboxymethyl cellulose into a four-neck flask under the condition of ice-water bath, and adding 4.7g of NaOH (the neutralization degree is controlled to be 70%) under the condition of stirring to obtain sodium carboxymethyl cellulose (the molecular weight is 90000-110000); then adding 30g of divinylbenzene, and uniformly stirring to obtain a mixed monomer;
2) weighing 30g parts of nano vermiculite, adding the nano vermiculite into the four-neck flask, placing the four-neck flask in a water bath kettle, keeping the constant temperature of the four-neck flask to 35 ℃, introducing nitrogen (in an oxygen-free environment), keeping adding 0.2% of ammonium persulfate (accounting for the mass sum of the divinylbenzene and the sodium carboxymethyl cellulose), stopping stirring when the viscosity is increased to be difficult to stir (about 10 min), continuously introducing the nitrogen, and taking out a reactant when the reactant is a viscous colloid; soaking and washing the product by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
3) drying the product (gel slice) obtained in the step 2) in a drying oven at the temperature of (105 +/-5) DEG C to constant weight, cooling the product in a drying dish to room temperature, and then using a nano high-pressure pulse pulverizer to mechanically impact the modified vermiculite to reach the particle size of 800nm to obtain the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite.
The test shows that the water absorption of the modified nano vermiculite on tap water is 1425 ml/g.
Example 2
A divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite comprises the following steps:
1) adding 40g of carboxymethyl cellulose into a four-neck flask under the condition of ice-water bath, and adding 5.3g of NaOH (the neutralization degree is controlled to be 80%) under the condition of stirring to obtain sodium carboxymethyl cellulose (the molecular weight is 90000-110000); then adding 30g of divinylbenzene and stirring uniformly;
2) weighing 30g parts of nano vermiculite, adding into the four-neck flask, placing into a water bath kettle, keeping the temperature to 35 +/-5 ℃, introducing nitrogen (in an oxygen-free environment), keeping adding 0.2% of ammonium persulfate (accounting for the mass sum of the divinylbenzene and the sodium carboxymethylcellulose), stopping stirring when the viscosity is increased to be difficult to stir (10 min), continuously introducing the nitrogen, and taking out a reactant when the reactant is a viscous colloid; soaking and washing the product by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
3) drying the product (gel slice) obtained in the step 2) in a drying oven at the temperature of (105 +/-5) DEG C to constant weight, cooling the product in a drying dish to room temperature, and then using a nano high-pressure pulse pulverizer to mechanically impact the modified vermiculite to reach the particle size of 800nm to obtain the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite.
The test shows that the water absorption of the modified nano vermiculite on tap water is 1868 ml/g.
Example 3
A divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite comprises the following steps:
1) adding 40g of carboxymethyl cellulose into a four-neck flask under the ice-water bath condition, and adding 6g of NaOH (the neutralization degree is controlled to be 90%) while stirring to obtain sodium carboxymethyl cellulose (the molecular weight is 90000-110000); then adding 30g of divinylbenzene and stirring uniformly;
2) weighing 30g parts of nano vermiculite, adding into the four-neck flask, placing into a water bath kettle, keeping the temperature to 35 +/-5 ℃, introducing nitrogen (in an oxygen-free environment), keeping adding 0.2% of ammonium persulfate (accounting for the mass sum of the divinylbenzene and the sodium carboxymethylcellulose), stopping stirring when the viscosity is increased to be difficult to stir (about 10 min), continuously introducing the nitrogen, and taking out a reactant when the reactant is a viscous colloid; soaking and washing the product by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
3) drying the product (gel slice) obtained in the step 2) in a drying oven at the temperature of (105 +/-5) DEG C to constant weight, cooling the product in a drying dish to room temperature, and then using a nano high-pressure pulse pulverizer to electrically impact the modified vermiculite to reach the particle size of 800nm to obtain the divinyl benzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite.
The modified nano vermiculite obtained in the embodiment has water absorption of 1245ml/g to tap water through testing.
Example 4
The preparation method of the slow-release concrete curing agent comprises the following steps:
1) preparing divinyl benzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid microcapsules: adding 15g of modified nano vermiculite obtained in example 2 (nano-grade high water absorption modified vermiculite), 2g of hydrolyzed polymaleic anhydride (HPMA) and 85g of water into a three-neck flask, irradiating by using an ultraviolet lamp, and then introducing nitrogen at room temperature and stirring at the mechanical rotation speed of 260rpm for 30 min; preparing modified nano vermiculite dispersion liquid;
2) dissolving 3g of Cetyl Trimethyl Ammonium Bromide (CTAB) in an alcohol-water solution (40 ml of ethanol and 80ml of water) to obtain a mixed solution I; it was transferred to a 250ml three-necked flask and 12g of NH were added3·H2Adding O and 80g of modified nano vermiculite dispersion liquid into the mixed liquid, heating to 35 ℃, mechanically stirring at the rotating speed of 250rpm for 25min, dropwise adding 5g of Tetraethoxysilane (TEOS) by using a peristaltic pump (4 rpm), and continuously stirring for 8h to obtain a suspension II;
3) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
The SEM image of the slow-release concrete curing agent obtained in the embodiment is shown in figure 1, and the result shows that the obtained product is in a nano-sphere shape and has a stable particle structure.
Example 5
The preparation method of the slow-release concrete curing agent comprises the following steps:
1) adding 40g of carboxymethyl cellulose into a four-neck flask under the condition of ice-water bath, and adding 5.3g of NaOH (the neutralization degree is controlled to be 80%) under the condition of stirring to obtain sodium carboxymethyl cellulose (the molecular weight is 90000-110000); then adding 30g of divinylbenzene and stirring uniformly;
2) weighing 30g parts of nano vermiculite, adding into the four-neck flask, placing into a water bath kettle, keeping the temperature to 35 +/-5 ℃, introducing nitrogen (in an oxygen-free environment), keeping adding 0.2% of ammonium persulfate (accounting for the mass sum of the divinylbenzene and the sodium carboxymethyl cellulose), stopping stirring when the viscosity is increased to be difficult to stir (10 min), continuously introducing the nitrogen, and taking out a reactant when the reactant is viscous colloid; soaking and washing the product by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
3) drying the product (gel slice) obtained in the step 2) in a drying oven at the temperature of (105 +/-5) DEG C to constant weight, cooling the product in a drying dish to room temperature, and then using a nano high-pressure pulse pulverizer to mechanically impact modified vermiculite to reach the particle size of 800nm to obtain the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite;
4) preparing divinyl benzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid microcapsules: adding 15g of the obtained modified nano vermiculite, 2g of hydrolyzed polymaleic anhydride (HPMA) and 85g of water into a three-neck flask, irradiating by using an ultraviolet lamp, and then introducing nitrogen at room temperature and stirring at the mechanical rotation speed of 260rpm for 30 min; preparing modified nano vermiculite dispersion liquid;
5) dissolving 3g of Cetyl Trimethyl Ammonium Bromide (CTAB) in an alcohol-water solution (40 ml of ethanol and 80ml of water) to obtain a mixed solution I; it was transferred to a 250ml three-necked flask and 12g of NH were added3·H2Adding O and 80g of modified nano vermiculite dispersion liquid into the mixed liquid, heating to 35 ℃, mechanically stirring at the rotating speed of 250rpm for 25min, dropwise adding 5g of Tetraethoxysilane (TEOS) by using a peristaltic pump (4 rpm), and continuously stirring for 8h to obtain a suspension II;
6) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
Comparative example 1
The preparation method of the slow-release concrete curing agent comprises the following steps:
1) preparing divinyl benzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid microcapsules: adding 15g of the nano-grade high-water-absorption modified vermiculite obtained in the example 2, 2g of hydrolyzed polymaleic anhydride (HPMA) and 85g of water into a three-neck flask, irradiating by using an ultraviolet lamp, and then introducing nitrogen at room temperature and stirring at the mechanical rotating speed of 260rpm for 30min to prepare a modified nano-vermiculite dispersion liquid;
2) dissolving 1.0g of Cetyl Trimethyl Ammonium Bromide (CTAB) in an alcohol-water solution (40 ml of ethanol and 80ml of water) to obtain a mixed solution I; it was transferred to a 250ml three-necked flask and 12g of NH were added3·H2Adding O and 80g of modified nano vermiculite dispersion liquid into the mixed liquid, and heatingMechanically stirring at the rotating speed of 250rpm for 25min at the temperature of 35 ℃, dropwise adding 6g of Tetraethoxysilane (TEOS) by using a peristaltic pump (4 rpm), and continuously stirring for 8h to obtain a suspension II;
3) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
The SEM image of the slow-release concrete curing agent obtained in the comparative example is shown in figure 2, and the obtained composite particle product is easy to collapse.
Comparative example 2
The preparation method of the slow-release concrete curing agent comprises the following steps:
1) preparing powder of vermiculite by ball milling with a common planetary ball mill: drying and dehydrating vermiculite at 105 ℃ to constant weight; then cooling in a drying dish, weighing 10g of dried vermiculite, putting into a planetary ball mill, and carrying out ball milling for 1h until the particle size reaches the minimum value (the particle size of the powder measured by multiple ball milling sampling is constant and does not change any more), so as to obtain vermiculite powder;
2) preparing divinylbenzene-sodium carboxymethylcellulose copolymerized modified vermiculite: adding 40g of carboxymethyl cellulose into a four-neck flask under the condition of ice-water bath, and adding 5.3g of NaOH (controlling the neutralization degree to be 80%) under the condition of stirring; then adding 30g of divinylbenzene and stirring uniformly;
3) weighing 30g parts of vermiculite powder, adding into the four-neck flask, placing into a water bath kettle, keeping the temperature to 35 ℃, introducing nitrogen (in an oxygen-free environment), keeping adding 0.2% ammonium persulfate (accounting for the mass sum of the divinylbenzene and the sodium carboxymethylcellulose), stopping stirring when the viscosity is increased to be difficult to stir (10 min), continuously introducing the nitrogen, and taking out a reactant when the reactant is viscous colloid; soaking and washing the product by absolute ethyl alcohol, and washing off residual alkali and monomers in the reaction product;
4) drying the product (gel slice) obtained in the step 2) in a drying oven at the temperature of (105 +/-5) DEG C to constant weight, cooling the product in a drying dish to room temperature, and then carrying out ball milling in a planetary ball mill for 1 hour until the particle size reaches the maximum value to obtain the divinylbenzene-sodium carboxymethylcellulose copolymerized modified vermiculite;
5) preparing a divinylbenzene-sodium carboxymethylcellulose copolymerized modified vermiculite dispersion microcapsule: adding 15g of the obtained copolymerization modified vermiculite, 2g of hydrolyzed polymaleic anhydride (HPMA) and 85g of water into a three-neck flask, irradiating by using an ultraviolet lamp, and then introducing nitrogen at room temperature and stirring at the mechanical rotating speed of 260rpm for 30min to prepare a modified vermiculite dispersion liquid;
6) dissolving 3g of Cetyl Trimethyl Ammonium Bromide (CTAB) in an alcohol-water solution (40 ml of ethanol and 80ml of water) to obtain a mixed solution I; it was transferred to a 250ml three-necked flask and 12g of NH were added3·H2Adding O and 80g of modified vermiculite dispersion liquid into the mixed liquid, heating to 35 ℃, mechanically stirring at the rotating speed of 250rpm for 25min, dropwise adding 5g of Tetraethoxysilane (TEOS) by using a peristaltic pump (4 rpm), and continuously stirring for 8h to obtain suspension II;
7) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
The SEM image of the slow-release concrete curing agent obtained in the comparative example is shown in figure 3, and the structure of the obtained composite particle product does not form a microcapsule.
Application example
The slow-release concrete curing agent obtained in the example 4 is applied to the preparation of a concrete test piece, and is compared with the conventional internal curing agents such as water-absorbing ceramsite (comparison group 1) and super absorbent resin (comparison group 2), wherein the preparation and the ratio of the prepared concrete test piece are shown in table 1; the results of the performance tests of the concrete samples obtained with the different curing agents are shown in table 2.
TABLE 1 concrete specimen mix and proportion (parts by weight)
| Cement | Fly ash | Mineral powder | Sand | Crushed stone of 5-20mm | 20-40mm broken stone | Water (W) | Water reducing agent |
| 160 | 105 | 105 | 714 | 583 | 583 | 160 | 1.4 |
TABLE 2 Performance test results of concrete samples obtained with different curing agents
| Numbering | Internal curing agent | Internal dampness after 3 days Degree (%) | Internal dampness after 10 days Degree (percent)） | Total opening per unit area Crack area (mm 2/m 2) | 28 day compressive strength |
| Application example 1 | Example 4 | 96 | 92 | 258 | 143% |
| Control group 1 | Commercially available water-absorbing ceramsite | 95 | 54 | 452 | 115% |
| Control group 2 | Commercially available super absorbent resin | 96 | 68 | 687 | 105% |
| Comparative example 2 | Vermiculite without nano activation modification | 96 | 65 | 367 | 112% |
It is apparent that the above embodiments are only examples for clearly illustrating and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.
Claims (8)
1. A slow-release concrete curing agent is characterized in that the curing agent is a microcapsule prepared by taking divinylbenzene-sodium carboxymethylcellulose copolymerization modified nano vermiculite dispersion liquid as a capsule core and silicon dioxide particles as capsule wall materials; wherein the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid is prepared by compounding divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite, hydrolyzed polymaleic anhydride and water as raw materials;
the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite is prepared by mixing nano vermiculite with sodium carboxymethylcellulose and divinylbenzene, and performing graft polymerization reaction, washing, drying and crushing under the anaerobic condition and the initiator condition;
the nano vermiculite is prepared by carrying out nano-scale surface activation on vermiculite, and comprises the following specific steps: drying and dehydrating the vermiculite at the temperature of 100-110 ℃ to constant weight, then cooling, and crushing to the particle size of 200-300 nm.
2. The slow-release concrete curing agent according to claim 1, wherein the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid comprises the following components in percentage by weight: 10-20 parts of divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite, 2-3 parts of hydrolyzed polymaleic anhydride and 80-90 parts of water; the polyethylene glycol modified nano-vermiculite is prepared by mixing divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano-vermiculite, hydrolyzed polymaleic anhydride and water, and stirring under the conditions of ultraviolet irradiation and protective atmosphere.
3. The slow-release concrete curing agent of claim 1, wherein the mass ratio of the nano vermiculite to the sodium carboxymethyl cellulose to the divinyl benzene is (30-50) to (30-40) to (20-30).
4. The slow-release concrete curing agent according to claim 1, wherein the graft polymerization reaction temperature is 30-40 ℃ and the reaction time is 8-15 min.
5. The slow-release concrete curing agent as claimed in claim 1, wherein the particle size of the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano-vermiculite is 600-900nm in the preparation process.
6. The preparation method of the slow-release concrete curing agent as claimed in any one of claims 1 to 5, characterized by comprising the following steps:
1) dissolving cetyl trimethyl ammonium bromide in an alcohol-water solution, and uniformly mixing to obtain a mixed solution I;
2) reacting NH3·H2Adding O and divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano vermiculite dispersion liquid into the mixed liquid I, mechanically stirring for 20-30min at the temperature of 30-40 ℃ and the rotating speed of 200-300rpm, dropwise adding tetraethoxysilane, and continuously stirring for 7.5-8.5h to obtain suspension liquid II;
3) and washing the obtained suspension II, and airing at room temperature to obtain the slow-release concrete curing agent.
7. The preparation method of claim 6, wherein the mass ratio of the divinylbenzene-sodium carboxymethylcellulose copolymerized modified nano-vermiculite dispersion to the tetraethoxysilane is (70-80): (5-7).
8. The method of claim 6, wherein the cetyltrimethylammonium bromide, NH3·H2The mass ratio of O to tetraethoxysilane is (2-4) to (10-12) to (5-7).
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