CN117917443B - Starch-based cement-based material internal curing agent with high water absorption and high salt tolerance, and preparation method and application thereof - Google Patents
Starch-based cement-based material internal curing agent with high water absorption and high salt tolerance, and preparation method and application thereof Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 218
- 238000010521 absorption reaction Methods 0.000 title claims abstract description 110
- 239000004568 cement Substances 0.000 title claims abstract description 88
- 239000000463 material Substances 0.000 title claims abstract description 70
- 239000003795 chemical substances by application Substances 0.000 title claims abstract description 61
- 229920002472 Starch Polymers 0.000 title claims abstract description 59
- 239000008107 starch Substances 0.000 title claims abstract description 59
- 235000019698 starch Nutrition 0.000 title claims abstract description 59
- 230000015784 hyperosmotic salinity response Effects 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000000178 monomer Substances 0.000 claims abstract description 101
- 239000012153 distilled water Substances 0.000 claims abstract description 60
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 58
- 239000003999 initiator Substances 0.000 claims abstract description 52
- 238000006243 chemical reaction Methods 0.000 claims abstract description 32
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229920002261 Corn starch Polymers 0.000 claims abstract description 27
- 239000008120 corn starch Substances 0.000 claims abstract description 27
- 238000000227 grinding Methods 0.000 claims abstract description 25
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 24
- 238000005406 washing Methods 0.000 claims abstract description 20
- 230000000977 initiatory effect Effects 0.000 claims abstract description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 14
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- 239000007795 chemical reaction product Substances 0.000 claims abstract description 13
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 54
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 36
- DZSVIVLGBJKQAP-UHFFFAOYSA-N 1-(2-methyl-5-propan-2-ylcyclohex-2-en-1-yl)propan-1-one Chemical compound CCC(=O)C1CC(C(C)C)CC=C1C DZSVIVLGBJKQAP-UHFFFAOYSA-N 0.000 claims description 27
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- 238000000034 method Methods 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 20
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 18
- 230000035484 reaction time Effects 0.000 claims description 18
- XMPZTFVPEKAKFH-UHFFFAOYSA-P ceric ammonium nitrate Chemical compound [NH4+].[NH4+].[Ce+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O XMPZTFVPEKAKFH-UHFFFAOYSA-P 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 16
- 238000013461 design Methods 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
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- HKVFISRIUUGTIB-UHFFFAOYSA-O azanium;cerium;nitrate Chemical compound [NH4+].[Ce].[O-][N+]([O-])=O HKVFISRIUUGTIB-UHFFFAOYSA-O 0.000 claims description 11
- 150000002500 ions Chemical class 0.000 claims description 10
- ZIUHHBKFKCYYJD-UHFFFAOYSA-N n,n'-methylenebisacrylamide Chemical group C=CC(=O)NCNC(=O)C=C ZIUHHBKFKCYYJD-UHFFFAOYSA-N 0.000 claims description 10
- 229920000642 polymer Polymers 0.000 claims description 8
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 2
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- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 8
- 150000003460 sulfonic acids Chemical class 0.000 description 8
- 238000003795 desorption Methods 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 6
- CNCOEDDPFOAUMB-UHFFFAOYSA-N N-Methylolacrylamide Chemical compound OCNC(=O)C=C CNCOEDDPFOAUMB-UHFFFAOYSA-N 0.000 description 5
- 244000269722 Thea sinensis Species 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
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- 239000003208 petroleum Substances 0.000 description 5
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 5
- 235000010265 sodium sulphite Nutrition 0.000 description 5
- NLVXSWCKKBEXTG-UHFFFAOYSA-N vinylsulfonic acid Chemical compound OS(=O)(=O)C=C NLVXSWCKKBEXTG-UHFFFAOYSA-N 0.000 description 5
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- 150000001875 compounds Chemical class 0.000 description 4
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- XHZPRMZZQOIPDS-UHFFFAOYSA-N 2-Methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid Chemical compound OS(=O)(=O)CC(C)(C)NC(=O)C=C XHZPRMZZQOIPDS-UHFFFAOYSA-N 0.000 description 2
- 239000004971 Cross linker Substances 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
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- 230000007423 decrease Effects 0.000 description 2
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- 229910052739 hydrogen Inorganic materials 0.000 description 2
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- 239000002994 raw material Substances 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000004583 superabsorbent polymers (SAPs) Substances 0.000 description 2
- 238000010257 thawing Methods 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- RNIHAPSVIGPAFF-UHFFFAOYSA-N Acrylamide-acrylic acid resin Chemical compound NC(=O)C=C.OC(=O)C=C RNIHAPSVIGPAFF-UHFFFAOYSA-N 0.000 description 1
- 229920000945 Amylopectin Polymers 0.000 description 1
- 229920000856 Amylose Polymers 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 229920006322 acrylamide copolymer Polymers 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
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- 229920001002 functional polymer Polymers 0.000 description 1
- 238000010413 gardening Methods 0.000 description 1
- 108010025899 gelatin film Proteins 0.000 description 1
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- 238000011056 performance test Methods 0.000 description 1
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- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 1
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- 238000000518 rheometry Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 1
- 241000894007 species Species 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
- C04B24/24—Macromolecular compounds
- C04B24/38—Polysaccharides or derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Polymerisation Methods In General (AREA)
Abstract
An internal curing agent of a starch-based cement-based material with high water absorption and high salt resistance and a preparation method and application thereof, belonging to the technical field of building material production. In order to improve the water absorption and salt tolerance of the super absorbent polymer, the invention takes the mass of hydrophilic monomers as the basis, adds distilled water with certain mass into corn starch, carries out gelatinization reaction under the protection of nitrogen, then drops initiator solution for initiating reaction, then drops hydrophilic monomer solution and cross-linking agent solution for polymerization reaction under the protection of nitrogen, cools to room temperature after reaction to obtain reaction products until washing solution becomes neutral, then uses ethanol solution for soaking and washing to obtain crude products, dries to constant weight in an oven, and then uses a grinder for grinding to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance. The invention has the characteristics of high water absorption, strong salt tolerance, strong water retention and long water release time, and can effectively reduce the self-shrinkage in the cement paste with low water-cement ratio.
Description
Technical Field
The invention belongs to the technical field of building material production, and particularly relates to a starch-based cement-based material internal curing agent with high water absorption and high salt resistance, a preparation method and application thereof.
Background
The super absorbent polymer (SuperAbsorbent Polymer, SAP) is a functional polymer material with a three-dimensional network structure, and expands when contacted with water, so that the water absorption capacity of the super absorbent polymer reaches hundreds to thousands times of the self weight. SAP has wide application in various fields such as agriculture, gardening, medicine and health. The introduction of SAP in cementitious materials has been found to have effects of reducing self-shrinkage, improving rheology, and enhancing freeze resistance. Currently, SAPs in the field of building materials are mainly represented by sodium Polyacrylate (PAA) and acrylic acid-acrylamide copolymer (PAM). However, these SAPs are not specifically developed for building materials, and have disadvantages in practical use, such as too low water absorption in cement filtrate, and the alkaline environment of the cement-based material reduces the water absorption of the SAP and prematurely desorbs water during the plastic phase of the slurry, reducing the self-shrinkage mitigation effect. Meanwhile, the petroleum-based SAP is mainly prepared from petroleum derivatives-propylene compounds, and has high price and poor degradation performance.
Starch-based SAPs have advantages in terms of biodegradability, reproducibility, and low cost compared to petroleum-based SAPs. Starch is a natural biopolymer extracted from plants and can be classified into amylose and amylopectin according to the source. It is also one of the earliest raw materials used to synthesize modified natural polymers to produce SAPs. The synthesis of superabsorbent polymers using starch has been a long development but there are problems at present. For example, starch-based SAPs synthesized with acrylic acid or acrylamide as hydrophilic monomers are not very different from petroleum-based SAPs (PAA, PAM) in water absorption properties. Secondly, most of the synthesis of SAP is mainly qualitative research, and quantitative design of SAP synthesis is lacking. Whether petroleum-based SAP or bio-based SAP, the water absorption performance of the SAP in deionized water or sodium chloride solution is used as a good and bad standard, and the design, synthesis and application of the internal curing agent for cement-based materials are not proposed yet.
Disclosure of Invention
The invention aims to solve the problem of improving the water absorption and salt tolerance of a super absorbent polymer, and provides a super absorbent and high salt tolerance starch-based cement-based material internal curing agent, a preparation method and application thereof.
In order to achieve the above purpose, the present invention is realized by the following technical scheme:
A preparation method of a starch-based cement-based material internal curing agent with high water absorption and high salt resistance comprises the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
S2, adding distilled water with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
S7, drying the crude product obtained in the step S6 to constant weight in an oven, and grinding by a grinder to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt resistance.
Further, the hydrophilic monomers in the step S1 are divided into amides and sulfonic acids, wherein the amides hydrophilic monomers comprise one of acrylamide, methacrylamide, N-alkylacrylamide, N-alkylacrylamide and N-hydroxyalkyl acrylamide, and the sulfonic acids comprise one of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and 4-allylbenzenesulfonic acid; the initiator is a redox initiator of a compound initiation system and comprises one or more of ammonium persulfate, potassium persulfate, ammonium cerium nitrate, sodium sulfite and sodium bisulfite; the cross-linking agent is amide, and comprises one of N, N' -methylene bisacrylamide and N-methylol acrylamide.
Further, the hydrophilic monomer in the step S1 is a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, the initiator is a mixture of ceric ammonium nitrate and ammonium persulfate, and the cross-linking agent is N, N' -methylenebisacrylamide; the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 3-5:1; the mass ratio of the hydrophilic monomer to the corn starch is 5-7:1, the mass ratio of the hydrophilic monomer to the initiator is 1:0.5-1.5%, the mass ratio of cerium ammonium nitrate to ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.05-0.15%, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 6.4-8.6:1.
Further, in the step S2, the mass ratio of the corn starch to the distilled water is 1:12-20, the gelatinization reaction temperature is 80-85 ℃ under the water bath condition, and the reaction time is 1-1.5h.
Further, in the step S3, the mass ratio of the initiator to the distilled water is 1:1-2, and the initiation reaction time is 15-20min.
Further, in the step S4, the mass ratio of the hydrophilic monomer to the distilled water is 1:1-4, and the mass ratio of the cross-linking agent to the distilled water is 1:1-2.
Further, in the step S5, the dripping time of the hydrophilic monomer solution is 2 hours, the cross-linking agent solution is added after the monomer is added, the polymerization reaction temperature is 60-80 ℃, and the polymerization reaction time is 2.5-3.5 hours.
Further, the drying temperature in the drying oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2-3 minutes, and screening is carried out after grinding.
The preparation method of the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is characterized in that the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is prepared based on molecular design and aqueous solution polymerization.
The application of the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is applied to the field of buildings.
The invention has the beneficial effects that:
The preparation method of the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance provided by the invention is based on a polymer water absorption theory, and a starch-based super absorbent polymer (SSP) with sufficient water absorption, stable water storage and lasting water release is quantitatively and qualitatively synthesized through molecular design and orthogonal experiments. The best condition for synthesizing SSP is that the mass ratio of acrylamide to 2-acrylamide-2-methylpropanesulfonic acid is 4.5:1, the initiator and the cross-linking agent are respectively 0.85 percent and 0.15 percent of the mass of the monomer, and the polymerization temperature is 75 ℃. Under this condition, SSP had water absorption of 1360g/g and 97g/g in deionized water, cement filtrate, much higher than PAA (480 g/g and 20 g/g) and PAM (410 g/g and 50 g/g). When added to the cement slurry, the shrinkage strain relief amplitudes of PAA, PAM and SSP were 58.1%, 29.7% and 12.2%, respectively, compared to the control group. Compared with PAA and PAM, SSP has higher water absorption rate and longer water release time, can effectively slow down the self-shrinkage of cement paste, and is more suitable for practical engineering application as an internal curing agent.
The starch-based cement-based material internal curing agent with high water absorption and high salt tolerance has the characteristics of high water absorption, high salt tolerance, high water retention rate and long water release time, and can effectively reduce self-shrinkage in low water-cement ratio cement paste.
Drawings
FIG. 1 is a flow chart of a method for preparing a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the invention;
FIG. 2 is a schematic diagram of the design flow of a method for preparing a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the invention;
FIG. 3 is a synthetic schematic diagram of a method for preparing a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the invention;
FIG. 4 is a graph showing the comparison of the water absorption of a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the present invention;
FIG. 5 is a graph showing the comparison of the water retention rate of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance according to the present invention;
FIG. 6 is a graph showing the comparison of the water release time of a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the present invention;
FIG. 7 is an infrared spectrum of a curing agent in a starch-based cement-based material with high water absorption and high salt tolerance according to the invention;
FIG. 8 is a scanning electron micrograph of a curing agent in a highly water-absorbent, highly salt-tolerant starch-based cement-based material according to the present invention;
FIG. 9 is a scanning electron micrograph of a high water and salt tolerant starch-based cement-based material internal curing agent according to the present invention after water absorption in the cement filtrate;
FIG. 10 is a graph showing the comparison of the effect of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance on the self-shrinkage of cement paste.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and detailed description. It should be understood that the embodiments described herein are for purposes of illustration only and are not intended to limit the invention, i.e., the embodiments described are merely some, but not all, of the embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein can be arranged and designed in a wide variety of different configurations, and the present invention can have other embodiments as well.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
For further understanding of the invention, the following detailed description of the invention will be presented with reference to fig. 1-10, and is provided in detail as follows:
The first embodiment is as follows:
A preparation method of a starch-based cement-based material internal curing agent (SSP) with high water absorption and high salt resistance comprises the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
Further, the hydrophilic monomer in the step S1 is a mixture of Acrylamide (AM) and 2-acrylamide-2-methylpropanesulfonic Acid (AMPS), the initiator is a mixture of Ceric Ammonium Nitrate (CAN) and Ammonium Persulfate (APS), and the cross-linking agent is N, N' -Methylenebisacrylamide (MBA); the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 3-5:1;
Further, in the step S1, the mass ratio of the hydrophilic monomer to the corn starch is 5-7:1, the mass ratio of the hydrophilic monomer to the initiator is 1:0.5-1.5%, the mass ratio of the cerium ammonium nitrate to the ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.05-0.15%, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 6.4-8.6:1;
S2, adding Distilled Water (DW) with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
further, in the step S2, the mass ratio of the corn starch to the distilled water is 1:12-20, the gelatinization reaction temperature is 80-85 ℃ under the water bath condition, and the reaction time is 1-1.5h;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
Further, in the step S3, the mass ratio of the initiator to the distilled water is 1:1-2, and the initiation reaction time is 15-20min;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
Further, in the step S4, the mass ratio of the hydrophilic monomer to the distilled water is 1:1-4, and the mass ratio of the cross-linking agent to the distilled water is 1:1-2;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
Further, in the step S5, the dripping time of the hydrophilic monomer solution is 2 hours, the crosslinking agent solution is added after the monomer is added, the polymerization reaction temperature is 60-80 ℃, and the polymerization reaction time is 2.5-3.5 hours;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
s7, drying the crude product obtained in the step S6 in an oven to constant weight, and grinding by a grinder to obtain a starch-based cement-based material internal curing agent (SAP) with high water absorption and high salt resistance;
Further, the drying temperature in the drying oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2-3 minutes, and screening is carried out after grinding.
According to the preparation method of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance, the reaction mechanism is shown in fig. 3, after starch is gelatinized, an initiator is heated and decomposed to generate active Ce 4+, a 2, 3-position C-C bond of glucose is attacked, C 3 is oxidized into C=O, C 2 generates primary free radicals, and the primary free radicals form two new active centers together with AM and AMPS. The free radical starch-AM and the free radical starch-AMPS undergo a grafting reaction to generate a starch-AM-AMPS monomer graft, and as the reaction proceeds, active chains continuously grow to form long-chain grafts, and the active long chains are crosslinked with each other under the action of MBA after losing the reaction activity, SO that a three-dimensional space network copolymer with starch molecules as a framework and grafted amide groups (-CONH 2) and sulfonic acid groups (-SO 3 H) is obtained.
The preparation method of the high-water-absorption high-salt-tolerance starch-based cement-based material internal curing agent is used for performance test, wherein the water absorption and release test method comprises the following steps: the water absorption of SAP was measured using the tea bag method. SAP was first vacuum dried for 24 hours (m 0) with a particle size of 0.25-0.5mm. Subsequently, the SAP was placed in a wet tea bag (m 1) and beaker, 200mL of solution (DW, TW, SC and CF) were added, DW and TW were deionized water and tap water, SC was a sodium chloride solution with a mass fraction of 0.9%, CF was cement filtrate obtained by filtration with a water to cement ratio (w/c) of 10. After the solution is absorbed for 12 hours, the tea bag is taken down, the surface (m) of the tea bag is wiped off, and the water absorption rate calculation formula is (m-m 1-m 0)/m 0. SAP absorbed for 12h (m 2) was wrapped in tea bag, placed in CF for 6h, and weighed (m 3). The water storage amount calculation formula is (m 3/m 2) multiplied by 100 percent. The SAP absorbed for 12h was placed in an evaporation dish (temperature: 20.+ -. 5 ℃ C., humidity: 40.+ -. 5%). The water absorption at various times is considered to be the water release rate of the SAP.
The water absorption of SSP is affected by factors such as monomer ratio, initiator amount, crosslinker amount, and reaction temperature. The synthesis factors of SSP were thus analyzed by orthogonal experiments to determine the best synthesis process, as shown in tables 1 and 2.
TABLE 1L 9(34) analysis of orthogonal test results
TABLE 2 extremely bad analysis
As can be seen from tables 1 and 2, the effect of the amount of monomer on the grafting ratio was greatest. The higher the dose, the higher the probability of grafting. The initiator directly affects the number of molecular grafting sites. Too low a crosslink density can result in segregation of monomer branches that have been grafted, reducing the amount of grafted monomer. The polymerization temperature affects the transfer and termination of the molecular chains, reducing the possibility of grafting. In summary, the best synthesis conditions for SSP were AM: AMPS ratio of 4.5:1, initiator and crosslinker amounts of 0.85% and 0.15% by mass of monomer, respectively, and polymerization temperature of 75 ℃. In DW and CF, SSP has water absorption of 1360g/g and 97g/g, respectively, meeting the requirements of high water absorption and salt tolerance.
The second embodiment is as follows:
The starch-based cement-based material internal curing agent with high water absorption and high salt tolerance prepared by the method for preparing the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance according to the first embodiment is synthesized based on a molecular design and an aqueous solution polymerization method, and utilizes a Flory-Huggins model.
The starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is synthesized according to the optimal synthesis condition of the specific embodiment, wherein the optimal synthesis condition of SSP is AM: AMPS ratio of 4.5:1, the dosage of an initiator and a cross-linking agent is 0.85% and 0.15%, and the polymerization temperature is 75 ℃.
According to the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance, a classical Flory-Huggins theory is established based on a high molecular thermodynamic theory by using Flory and Huggins, the gel swelling water absorption capacity of the SAPs is described, and three key factors affecting the water absorption performance of the SAPs are quantitatively described: the external solution ion osmotic pressure, the affinity for moisture and the crosslinking density are calculated as follows:
Wherein Q, i/V u,V1,and Ve/V0 represents the water absorption rate, charge density, specific volume and crosslinking density of the polymer, and S and χ 1 represents the ionic strength of the external solution and the interaction force with the polymer.
The Flory-Huggins formula can be divided into charge densitiesHydrophilic power of groupAnd crosslink density (V e/V0), so that the water absorption capacity of SAPs is mainly determined by these three points.
Through molecular structure design, the quantitative design is carried out on the SAPs, and the SAPs with the functions of full water absorption, stable water storage and controllable water release are synthesized. The water absorption performance is improved by regulating and controlling the charge density inside the polymer, and the hydrophilic capacity of the hydrophilic group is as follows: -SO 3H>-COOH>-CONH2 > -OH, and controlling the crosslinking density by the doping amount, thereby realizing the molecular design of the SAPs structure.
Firstly, analyzing a super absorbent polymer, taking Flory-Huggins models proposed by Flory and Huggins as theoretical basis for analyzing influence factors of the water absorption performance of the SAP, and taking the improvement of the water absorption rate and the salt tolerance as targets, and selecting each factor of SAP synthesis in a targeted and targeted manner. Secondly, corn starch is used as a main raw material, after preliminary treatment is carried out on the corn starch, corresponding reactants such as an initiator, a cross-linking agent and the like are added, and a corresponding high molecular polymerization method and process are selected to preliminarily synthesize the polymer with water absorption performance. Based on the method, the optimal synthesis process of SSP is optimized by adopting orthogonal design, and the water absorption performance is compared with that of PAA and PAM. Finally, adding a plurality of SAP into cement, and researching the improvement of the SAP on the self-shrinkage of the cement paste.
The water absorption ratio comparison chart of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance in the embodiment is shown in fig. 4, wherein PAA and PAM are commercial comparison products, and as can be seen from fig. 4, the water absorption ratio of SAP gradually decreases with increasing ion content in the solution, but the water absorption ratio of SSP is still higher than that of PAA and PAM. The higher the ion concentration, the more pronounced the effect on the water absorption capacity of the SAP. In DW and TW, SSP has the highest water absorption, whereas PAA and PAM have similar water absorption but lower SSP than in SC. The water absorption of PAA and PAM in CF was only 20.6% and 51.5% of SSP. The main driving forces for PAA and PAM water absorption are ion osmotic pressure and hydrogen bonding, respectively. And SSP combines the two driving forces, reduces the influence of ion concentration and osmotic pressure, and enhances the diffusion capacity of molecular chains, thereby improving the water absorption rate.
Further, conventional superabsorbent polymers such as PAA and PAM have high water absorption in deionized water, but have a significant drop in salt solution (e.g., 0.9% sodium chloride solution by mass), such as about 500 times in deionized water, and only about 50 times in 0.9% sodium chloride solution. This is even further true in such low concentration solutions, and more so in slurry solutions of cement-based materials of higher ionic species and concentration, with specific values looking at the behavior in CF solution of fig. 4. The reason for the lower water absorption in salt solutions is the ion shielding effect and charge effect, as well as some of the complexation reactions that occur; the application environment of the internal curing agent is cement-based material, so that the more complex CF is taken as an absorption environment, and the water absorption rate of the super absorbent polymer in the CF can represent the salt tolerance of the super absorbent polymer.
The water retention ratio comparison chart of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance in the embodiment is shown in fig. 5, and it can be seen from fig. 5 that with the increase of ion type and concentration, the homoionic effect and ion complexation reaction can be generated, resulting in the decrease of the water absorption and structural stability of the SAP. The network structure of the SAP contracts under pressure, resulting in its desorbed water volume being greater than the water absorption volume. In the same solution, the desorption rate of SSP is highest. When the SAP gel is in a multi-ionic alkaline solution, the low ionization degree of SSP reduces the impact of the homoionic effect, resulting in a smaller degree of shrinkage of the network structure and thus lower hydrolytic absorption. However, due to the high initial water absorption of SSP, the amount of desorbed water is relatively high under the influence of the outside world, resulting in a high overall amount of desorbed water. In alkaline environments, the hydrolytic absorption of SAP is critical to the internal curing effect. The higher the desorption water amount of the gel material after hardening, the better the internal curing effect.
As shown in fig. 6, for example, the water release time of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance in the present embodiment is shown in fig. 6, it is clear from fig. 6 that the water content of SSP is reduced by a much higher extent than PAA and PAM in the first 24 hours, and the desorption rate is related to the initial water content. During the hydrolytic absorption of the SAP, the hydrophilic groups gradually protonate, resulting in hydrogen bonding interactions between adjacent groups, causing the network structure to shrink and drain outward until the humidity gradient is zero. SSP, PAA and PAM completed desorption of water in CF for 80h, 30h and 50h, respectively. Because SSP has excellent water absorption and salt tolerance, which is critical for the internal curing of cement-based materials, the water desorption time of SSP is longer under the same conditions.
The infrared spectrum of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance in the embodiment is shown in fig. 7, and as can be seen from fig. 7, peaks at 2930cm -1 and 1570cm -1 represent the C-H and O-H characteristic vibrations of-CH 3 and-CH 2 -groups in starch, which are two main structures in starch molecules. Peaks at 3310cm -1、1670cm-1、1540cm-1 and 1285cm -1 are characteristic oscillations of the-CONH 2 group and peaks at 1205cm -1、1055cm-1 and 630cm -1 are-SO 3 H group. Both structures were observed in SSP, indicating successful grafting of-SO 3 H and-CONH 2 onto the starch backbone. This molecular structure analysis verifies the correctness of the SSP molecular design.
As shown in fig. 8 and 9, the scanning electron microscope photographs of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance and the water absorption and swelling thereof are shown in fig. 8 and 9, the SSP has a highly porous surface, which increases the contact area with water molecules, allows water to rapidly permeate, and results in higher water absorption capacity. In SSP-CF there are many macropores (20-100 um), but the gel film is thicker. The presence of multiple ions in the CF results in thicker gel films and smaller pores, and SSP can fully form network space with the gel films.
The comparison curve of the effect of the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance on the self-shrinkage of the cement paste is shown in fig. 10, and it is known from fig. 10 that the self-shrinkage of 4 cement pastes respectively reaches a stable state at 72h, 120h, 136h and 156 h. At 168h, the Control Group (CG), PAA, PAM and SSP had self-shrinkage of 1520 μm/m, 870 μm/m, 440 μm/m and 120 μm/m, respectively. The shrinkage strains of PAA, PAM and SSP were 57.3%, 28.9% and 7.9%, respectively, compared to the control group. SSP has a better self-contraction relief effect than PAA and PAM. PAA is susceptible to early moisture desorption during the plastic phase of the cement slurry, resulting in an increased water to ash ratio, which has an adverse effect on slowing shrinkage. When the SAP content is the same, the effect of alleviating self-shrinkage is determined by the water absorption rate of the SAP. PAA desorbs water too quickly due to complexation with Ca 2+, whereas PAM absorbs water less than SSP. Under the same conditions, SSP has higher water absorption rate and longer water desorption time, and has better self-shrinkage slowing effect.
And a third specific embodiment:
the application of the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is used in the field of building.
A starch-based cement-based material internal curing agent (SSP) with high water absorption and high salt tolerance is used as a novel internal curing agent of a cement-based material, and the main application of SSP in the cement-based material comprises the following steps:
SSP can be used to develop self-healing cement-based materials. The material can automatically repair tiny cracks. SSP is added to cement-based materials, and when micro cracks occur, SSP absorbs water to expand and fill the cracks, preventing penetration of moisture and harmful substances, and extending the service life of concrete structures.
SSP can reduce self-shrinkage of cement-based materials. Modern cement-based materials are developed in a low water to cement ratio, which is prone to self-shrinkage during hardening, which may lead to crack formation. By adding SSP to the cement-based material, additional moisture can be absorbed and the self-shrinkage of the slurry can be reduced, reducing the risk of cracking.
SSP can improve freeze-thaw resistance. In cold climates, cement-based materials are susceptible to freeze-thaw cycles. The addition of SSP helps to reduce water penetration, reduce risk of damage caused by freeze thawing, and improve freeze thawing resistance of cement-based materials.
SSP is used as an internal curing agent for cement-based materials. In concrete construction, curing with cement slurry is often required. SSP can be added to the cement slurry to provide a durable wet environment that helps maintain the strength and quality of the concrete.
In general, the use of SSP in curing cement-based materials can improve the performance of the materials, reduce maintenance costs, and extend the service life of the structure. These applications help to improve the engineering properties of cement-based materials, making them more suitable for various building and infrastructure projects.
The specific embodiment IV is as follows:
A preparation method of a starch-based cement-based material internal curing agent with high water absorption and high salt resistance comprises the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
Further, the hydrophilic monomers in the step S1 are divided into amides and sulfonic acids, wherein the amides hydrophilic monomers comprise one of acrylamide, methacrylamide, N-alkylacrylamide, N-alkylacrylamide and N-hydroxyalkyl acrylamide, and the sulfonic acids comprise one of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and 4-allylbenzenesulfonic acid; the initiator is a redox initiator of a compound initiation system and comprises one or more of ammonium persulfate, potassium persulfate, ammonium cerium nitrate, sodium sulfite and sodium bisulfite; the cross-linking agent is amide, and comprises one of N, N' -methylenebisacrylamide and N-methylolacrylamide;
Further, the hydrophilic monomer in the step S1 is a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, the initiator is a mixture of ceric ammonium nitrate and ammonium persulfate, and the cross-linking agent is N, N' -methylenebisacrylamide; the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 3:1;
Further, in the step S1, the mass ratio of the hydrophilic monomer to the corn starch is 5:1, the mass ratio of the hydrophilic monomer to the initiator is 1:0.5%, the mass ratio of the ammonium cerium nitrate to the ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.05%, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 6.4:1;
S2, adding distilled water with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
Further, in the step S2, the mass ratio of the corn starch to the distilled water is 1:12, the gelatinization reaction temperature is 80 ℃ in a water bath condition, and the reaction time is 1h;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
further, in the step S3, the mass ratio of the initiator to the distilled water is 1:1, and the initiation reaction time is 15min;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
Further, in the step S4, the mass ratio of the hydrophilic monomer to the distilled water is 1:1, and the mass ratio of the cross-linking agent to the distilled water is 1:1;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
Further, in the step S5, the dripping time of the hydrophilic monomer solution is 2 hours, the crosslinking agent solution is added after the monomer is added, the polymerization reaction temperature is 60 ℃, and the polymerization reaction time is 2.5 hours;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
S7, drying the crude product obtained in the step S6 in an oven to constant weight, and grinding by a grinder to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt resistance;
Further, the drying temperature in the oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2 minutes, and the screening is carried out after the grinding.
Fifth embodiment:
A preparation method of a starch-based cement-based material internal curing agent with high water absorption and high salt resistance comprises the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
Further, the hydrophilic monomers in the step S1 are divided into amides and sulfonic acids, wherein the amides hydrophilic monomers comprise one of acrylamide, methacrylamide, N-alkylacrylamide, N-alkylacrylamide and N-hydroxyalkyl acrylamide, and the sulfonic acids comprise one of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and 4-allylbenzenesulfonic acid; the initiator is a redox initiator of a compound initiation system and comprises one or more of ammonium persulfate, potassium persulfate, ammonium cerium nitrate, sodium sulfite and sodium bisulfite; the cross-linking agent is amide, and comprises one of N, N' -methylenebisacrylamide and N-methylolacrylamide;
Further, the hydrophilic monomer in the step S1 is a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, the initiator is a mixture of ceric ammonium nitrate and ammonium persulfate, and the cross-linking agent is N, N' -methylenebisacrylamide; the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 5:1;
further, in the step S1, the mass ratio of the hydrophilic monomer to the corn starch is 7:1, the mass ratio of the hydrophilic monomer to the initiator is 1:1.5, the mass ratio of the ammonium cerium nitrate to the ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.15%, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 8.6:1;
S2, adding distilled water with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
Further, in the step S2, the mass ratio of the corn starch to the distilled water is 1:20, the gelatinization reaction temperature is 85 ℃ under the water bath condition, and the reaction time is 1.5h;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
further, in the step S3, the mass ratio of the initiator to the distilled water is 1:2, and the initiation reaction time is 20min;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
further, in the step S4, the mass ratio of the hydrophilic monomer to the distilled water is 1:4, and the mass ratio of the cross-linking agent to the distilled water is 1:2;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
Further, in the step S5, the dripping time of the hydrophilic monomer solution is 2 hours, the crosslinking agent solution is added after the monomer is added, the polymerization reaction temperature is 80 ℃, and the polymerization reaction time is 3.5 hours;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
S7, drying the crude product obtained in the step S6 in an oven to constant weight, and grinding by a grinder to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt resistance;
Further, the drying temperature in the drying oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2-3 minutes, and screening is carried out after grinding.
Specific embodiment six:
A preparation method of a starch-based cement-based material internal curing agent with high water absorption and high salt resistance comprises the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
Further, the hydrophilic monomers in the step S1 are divided into amides and sulfonic acids, wherein the amides hydrophilic monomers comprise one of acrylamide, methacrylamide, N-alkylacrylamide, N-alkylacrylamide and N-hydroxyalkyl acrylamide, and the sulfonic acids comprise one of 2-acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid and 4-allylbenzenesulfonic acid; the initiator is a redox initiator of a compound initiation system and comprises one or more of ammonium persulfate, potassium persulfate, ammonium cerium nitrate, sodium sulfite and sodium bisulfite; the cross-linking agent is amide, and comprises one of N, N' -methylenebisacrylamide and N-methylolacrylamide;
Further, the hydrophilic monomer in the step S1 is a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, the initiator is a mixture of ceric ammonium nitrate and ammonium persulfate, and the cross-linking agent is N, N' -methylenebisacrylamide; the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 4:1;
Further, in the step S1, the mass ratio of the hydrophilic monomer to the corn starch is 6:1, the mass ratio of the hydrophilic monomer to the initiator is 1:1, the mass ratio of the ammonium cerium nitrate to the ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.1, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 7:1;
S2, adding distilled water with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
further, in the step S2, the mass ratio of the corn starch to the distilled water is 1:15, the gelatinization reaction temperature is 85 ℃ under the water bath condition, and the reaction time is 1.2h;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
further, in the step S3, the mass ratio of the initiator to the distilled water is 1:1.5, and the initiation reaction time is 20min;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
Further, in the step S4, the mass ratio of the hydrophilic monomer to the distilled water is 1:3, and the mass ratio of the cross-linking agent to the distilled water is 1:1.5;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
Further, in the step S5, the dripping time of the hydrophilic monomer solution is 2 hours, the crosslinking agent solution is added after the monomer is added, the polymerization reaction temperature is 70 ℃, and the polymerization reaction time is 3 hours;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
S7, drying the crude product obtained in the step S6 in an oven to constant weight, and grinding by a grinder to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt resistance;
Further, the drying temperature in the drying oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2-3 minutes, and screening is carried out after grinding.
Seventh embodiment:
In a different aspect of this embodiment, the hydrophilic monomer is a mixture of methacrylamide and vinylsulfonic acid.
Eighth embodiment:
In a different aspect of this embodiment, the hydrophilic monomer is a mixture of N-alkylacrylamide and 4-allylbenzenesulfonic acid.
Detailed description nine:
in a variation of this embodiment, the hydrophilic monomer is a mixture of N, N-alkylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid.
Detailed description ten:
In a different aspect of this embodiment, the hydrophilic monomer is a mixture of N-hydroxyalkyl acrylamide and 2-acrylamido-2-methylpropanesulfonic acid.
Eleventh embodiment:
In this embodiment, the initiator is a mixture of ammonium cerium nitrate and potassium persulfate.
Twelve specific embodiments:
in this embodiment, the initiator is a mixture of ammonium cerium nitrate and sodium sulfite.
Thirteen specific embodiments:
In a different aspect of this embodiment, the initiator is a mixture of ammonium cerium nitrate and sodium bisulfite.
Fourteen specific embodiments:
in this embodiment, the initiator is a mixture of ammonium persulfate and sodium bisulfite.
Fifteen embodiments:
in this embodiment, the crosslinking agent is N-methylolacrylamide.
It is noted that relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Although the application has been described above with reference to specific embodiments, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, the features of the disclosed embodiments may be combined with each other in any manner so long as there is no structural conflict, and the exhaustive description of these combinations is not given in this specification solely for the sake of brevity and resource saving. Therefore, it is intended that the application not be limited to the particular embodiments disclosed herein, but that the application will include all embodiments falling within the scope of the appended claims.
Claims (3)
1. The preparation method of the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance is characterized by comprising the following steps:
S1, based on the mass of a hydrophilic monomer, respectively weighing the hydrophilic monomer, corn starch, an initiator, a cross-linking agent and sodium hydroxide according to mass ratio for later use;
The hydrophilic monomer in the step S1 is a mixture of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, the initiator is a mixture of ceric ammonium nitrate and ammonium persulfate, and the cross-linking agent is N, N' -methylene bisacrylamide; the mass ratio of the acrylamide to the 2-acrylamide-2-methylpropanesulfonic acid is 4.5:1; the mass ratio of the hydrophilic monomer to the corn starch is 5-7:1, the mass ratio of the hydrophilic monomer to the initiator is 1:0.85%, the mass ratio of the ammonium cerium nitrate to the ammonium persulfate in the initiator is 1:9, the mass ratio of the hydrophilic monomer to the cross-linking agent is 1:0.15%, and the mass ratio of the 2-acrylamide-2-methylpropanesulfonic acid to the sodium hydroxide in the hydrophilic monomer is 6.4-8.6:1;
S2, adding distilled water with a certain mass into the corn starch weighed in the step S1, uniformly mixing, adding into a four-necked flask, and stirring under the protection of nitrogen to perform gelatinization reaction to obtain a first mixed solution;
in the step S2, the mass ratio of the corn starch to the distilled water is 1:12-20, the gelatinization reaction temperature is 80-85 ℃ under the water bath condition, and the reaction time is 1-1.5h;
S3, adding distilled water with a certain mass into the initiator weighed in the step S1, then dripping the distilled water into the first mixed solution obtained in the step S2, and standing for a certain time to perform an initiation reaction to obtain a second mixed solution;
In the step S3, the mass ratio of the initiator to the distilled water is 1:1-2, and the initiation reaction time is 15-20min;
s4, uniformly mixing the hydrophilic monomer weighed in the step S1 and sodium hydroxide, adding distilled water with a certain mass to obtain a hydrophilic monomer solution, and adding the cross-linking agent obtained in the step S1 into distilled water with a certain mass to obtain a cross-linking agent solution;
In the step S4, the mass ratio of hydrophilic monomer to distilled water in the hydrophilic monomer solution is 1:1-4, and the mass ratio of cross-linking agent to distilled water in the cross-linking agent solution is 1:1-2;
S5, dropwise adding the hydrophilic monomer solution obtained in the step S4 into the second mixed solution obtained in the step S3, then adding a cross-linking agent solution, stirring under the protection of nitrogen for polymerization reaction, and cooling to room temperature after the reaction to obtain a reaction product;
The time for dropwise adding the hydrophilic monomer solution in the step S5 is 2 hours, and after the monomer is added, the cross-linking agent solution is added, the polymerization reaction temperature is 75 ℃, and the polymerization reaction time is 2.5-3.5 hours;
S6, washing transparent gel in the reaction product obtained in the step S5 by deionized water until the washing solution becomes neutral, and then soaking and washing by ethanol solution to obtain a crude product;
S7, drying the crude product obtained in the step S6 in an oven to constant weight, and grinding by a grinder to obtain the starch-based cement-based material internal curing agent with high water absorption and high salt resistance;
in cement filtrate obtained by filtering with deionized water and water cement ratio of 10, the water absorption rate of the internal curing agent is 1360g/g and 97g/g respectively, so that the requirements of high water absorption rate and salt tolerance are met;
the classical Flory-Huggins theory is established based on the high molecular thermodynamic theory by using Flory and Huggins, the gel swelling and water absorption capacity of the internal curing agent is described, and three key factors affecting the water absorption performance of the internal curing agent are quantitatively described: the external solution ion osmotic pressure, the affinity for moisture and the crosslinking density are calculated as follows:
Wherein Q, i/V u,V1,and Ve/V0 represents the water absorption rate, charge density, specific volume and crosslinking density of the polymer, and S and χ 1 represent the ionic strength of the external solution and the interaction force with the polymer;
the Flory-Huggins formula can be divided into charge densities Hydrophilic power of groupAnd crosslinking density (V e/V0), so that the water absorption capacity of the internal curing agent is mainly determined by the three points;
quantitatively designing the internal curing agent through molecular structure design to synthesize the internal curing agent with controllable water absorption, stable water storage and water release; the water absorption performance is improved by regulating and controlling the charge density inside the polymer, and the hydrophilic capacity of the hydrophilic group is as follows:
And (3) controlling the crosslinking density through the doping amount of the-SO 3H>-COOH>-CONH2 -OH, SO as to realize the molecular design of the internal curing agent structure.
2. The method for preparing the curing agent in the starch-based cement-based material with high water absorption and high salt tolerance according to claim 1, wherein the drying temperature in the oven in the step S7 is 50 ℃, the power of the grinding machine is 100kW, the grinding time is 2-3 minutes, and the screening is carried out after the grinding.
3. The method for preparing the starch-based cement-based material internal curing agent with high water absorption and high salt tolerance according to any one of claims 1 to 2, which is characterized by being synthesized based on molecular design and an aqueous solution polymerization method.
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| CN103819614B (en) * | 2014-02-20 | 2016-08-17 | 桂林理工大学 | The preparation method of conserving material in alkali capacitive high moisture retention concrete |
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| CN102358773A (en) * | 2011-07-11 | 2012-02-22 | 桂林理工大学 | Preparation method for water-preserving and salt-tolerant alkaline concrete internal curing agent |
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