CN108997535B - Early-strength polycarboxylate water reducing agent and preparation method thereof - Google Patents
Early-strength polycarboxylate water reducing agent and preparation method thereof Download PDFInfo
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Abstract
The invention relates to an early-strength polycarboxylate water reducing agent and a preparation method thereof, wherein prenyl polyoxyethylene ether with a water reducing function, 3-allyloxy-1-hydroxypropanesulfonic acid and monomer formic acid with an early-strength function are introduced in a synthesis process·Dimethylaminoethyl acrylate, 3-acryloxy-2-hydroxypropyl trimethyl ammonium chloride, N-hydroxyethyl-N' -acrylurea and monomer methoxyethoxyethyl acrylate with slump retaining function are neutralized by triethanolamine with early strength and triisopropanolamine with late strength after the reaction is finished. The synthesized early-strength polycarboxylate water reducer has outstanding fast-dispersing, high-dispersing and fast-hydrating functions on cement, the early-strength water reducer is doped into concrete, the reinforcing effect is obvious, the early-strength is greatly improved, the later-strength can be stably developed, and the purposes of high concrete strength and good durability are achieved.
Description
Technical Field
The invention belongs to the technical field of concrete admixture synthesis, and particularly relates to an early-strength polycarboxylic acid water reducer and a preparation method thereof.
Background
The polycarboxylic acid high-performance water reducing agent has the advantages of good dispersibility, high water reducing rate, low mixing amount, strong slump retentivity, low shrinkage, no three wastes generated in the production process, environmental protection and the like, and is greatly concerned by people. In recent years, polycarboxylic acid high-performance water reducing agents have been widely used in the above infrastructure construction, and have played an important role. At present, the construction industry in China is developed at a high speed, particularly the construction development of a new male security area is rapid, the new male security area needs to be built into an international first-class, green, modern and intelligent new city, more than 90 percent of buildings are applied to green fabricated buildings, and reproducible 'male security mode' construction technology is established for the construction of other cities. A large number of prefabricated components are needed for the fabricated building, and the key influencing the production efficiency of the prefabricated components is the large demand on the early-strength polycarboxylate superplasticizer. The early-strength polycarboxylate superplasticizer has the effects of accelerating cement hydration, shortening the standing time, obviously improving the early strength, reducing the steam curing time of prefabricated parts, accelerating the turnover of concrete templates, improving the production efficiency and the like. The sina company researches an early strength water reducing agent specially for prefabricated parts, and has a good demonstration effect. However, the research on the early strength type polycarboxylate water reducer is reported in China, but the actual application effect is not ideal, so that the research and development on the early strength type polycarboxylate water reducer are urgent, and the research and development on the early strength type polycarboxylate water reducer have very important significance.
Disclosure of Invention
The invention aims to provide an early-strength polycarboxylate water reducer, which is characterized in that a monomer with a water reducing function, a monomer with an early-strength function and a monomer with a slump retaining function are introduced in the synthesis process, and the cement reinforcing effect of the water reducer is optimized so as to improve the early strength and the later strength of concrete. The invention also aims to provide a preparation method of the early-strength polycarboxylic acid water reducing agent
The technical scheme of the invention is as follows: an early strength type polycarboxylic acid water reducing agent is synthesized by introducing monomer isopentenol polyoxyethylene ether with molecular weight M being 5000 large molecular weight and having a water reducing function, 3-allyloxy-1-hydroxypropanesulfonic acid, monomer formic acid, dimethylaminoethyl acrylate, 3-acryloxy-2-hydroxypropyl trimethyl ammonium chloride, N-hydroxyethyl-N' -acrylurea and monomer methoxyethoxyethyl acrylate with a slump retaining function into a synthesis process, and neutralizing by using organic base triethanolamine with early strength and organic base triisopropanolamine with late strength after the reaction is finished.
The preparation method of the early-strength polycarboxylic acid water reducer comprises the following steps:
the first step is as follows: preparation of dimethylaminoethyl formate/acrylate
Quantitative formic acid and deionized water with equal mass are added into a 1000mL four-neck flask, and dimethylaminoethyl acrylate with equal molar quantity with formic acid is dripped into the flask by a peristaltic pump under the stirring at the constant temperature of 15 ℃. After reacting for 1.5h at the temperature of 15 ℃, adding deionized water to ensure that the solid content is 50 percent (mass), thus obtaining the aqueous solution of the formic acid-acrylic acid dimethylamino ethyl ester.
The second step is that: preparation of early-strength polycarboxylic acid water reducer
Adding a certain amount of prenyl polyoxyethylene ether macromonomer with the molecular weight of 5000 and a certain amount of deionized water into a 2000mL four-neck flask, heating to 30 ℃, and stirring to dissolve the macromonomer. After dissolving the prenol polyoxyethylene ether, adding ammonium persulfate accounting for 0.8 percent of the total mass of the monomers and hydrogen peroxide accounting for 0.4 percent of the total mass of the monomers, and uniformly stirring, wherein the total mass of the monomers is the total mass of all monomers participating in polymerization. And respectively dripping the solution A, the solution B, the solution C and the solution D by using a peristaltic pump at the temperature of 30 ℃, wherein the solution A, the solution B and the solution C are respectively dripped for 3.5 hours, and the solution D is dripped for 4.0 hours. The temperature is not controlled in the dripping process, and after the dripping is finished, the reaction is continued for 1.5h under the finishing temperature of the dripping. Cooling to 30 ℃, adding organic alkali triethanolamine and triisopropanolamine for neutralization, and supplementing deionized water to ensure that the solid content of the product is 40% (by mass), thereby obtaining the early-strength polycarboxylic acid water reducer. Wherein: the solution A is a 60 mass percent aqueous solution consisting of 4.5 to 6.0 mass percent of acrylic acid and 1.5 to 2.5 mass percent of 3-allyloxy-1-hydroxypropanesulfonic acid based on the mass of the prenol polyoxyethylene ether macromonomer; the solution B is a 50 mass% aqueous solution consisting of 2.5-4.0 mass% of dimethylaminoethyl formate and acrylate and 2.5-4.0 mass% of 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride based on the mass of the prenol polyoxyethylene ether macromonomer; the solution C is a 50 mass percent aqueous solution consisting of 0.5 to 1.5 mass percent of N-hydroxyethyl-N' -acrylurea and 2.5 to 4.0 mass percent of methoxyethoxyethyl acrylate based on the mass of the prenyl alcohol polyoxyethylene ether macromonomer; the solution D is a 5 mass% aqueous solution composed of 0.2 mass% of vitamin C and 0.4 mass% of 3-mercaptopropionic acid based on the total mass of the monomers.
The addition amount of the organic base triethanolamine is 65% of the theoretical molar amount of acrylic acid, and the addition amount of the triisopropanolamine is 35% of the theoretical molar amount of acrylic acid.
The early-strength polycarboxylate water reducer has the outstanding functions of fast dispersion, high dispersion and fast hydration to cement, the early-strength water reducer is doped into concrete to achieve obvious enhancement effect, the early strength of the concrete is greatly improved, and the later strength can be stably developed, so that the concrete is high in strength and good in durability. The method is widely applied to steam-cured concrete, concrete with urgent need for early strength in low-temperature environment and concrete with early formwork removal requirement, and can obviously shorten the plastering and initial setting time of the formed formwork, remove the formwork in advance and improve the turnover rate of the formwork, thereby greatly shortening the construction period, and accelerating the construction progress and labor productivity.
The invention uses high molecular weight monomer (molecular weight M is 5000) isopentenol polyoxyethylene ether and 3-allyloxy-1-hydroxypropane sulfonic acid with water reducing function, monomer formic acid and acrylic acid dimethylaminoethyl ester with early strength function, 3-acryloxy-2-hydroxypropyl trimethyl ammonium chloride and N-hydroxyethyl-N' -acryloyl urea, and monomer methoxyethoxyethyl acrylate with slump retaining function. The water reducing agent polymer uses macromonomers with large molecular weight, namely long-chain macromonomers, can form a thicker three-dimensional surrounding layer on the surface of cement particles, is beneficial to fast dispersion and high dispersion of cement materials, accelerates hydration of cement, and advances the setting time. Sulfonic acid group and ureide compounds, namely 3-allyloxy-1-hydroxypropanesulfonic acid and N-hydroxyethyl-N' -acrylurea, are introduced into the polymer, so that the high dispersibility of the polymer is improved, and the hydration reaction of minerals in cement is promoted. The cationic monomers of formic acid-dimethylaminoethyl acrylate and 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride are introduced into polymer molecules, can be adsorbed on electronegative cement minerals, can promote the hydration process of cement, shorten the setting time of the cement, and are favorable for quick setting and early strength. The methoxy ethoxy ethyl acrylate is introduced to play a role in plastic retention and slump loss reduction, and the repeated plastering and light collection during the standing waiting period after the concrete of the component is poured and molded can be ensured. After the reaction is finished, organic alkali triethanolamine and triisopropanolamine are adopted for neutralization, so that the alkali content of the product can be reduced, and the early and later strength of the concrete can be improved.
According to the early-strength polycarboxylate water reducer and the preparation method thereof, the monomer with the water reducing function, the monomer with the early-strength function and the monomer with the slump retaining function are introduced in the synthesis process, so that the cement reinforcing effect of the water reducer is optimized, and the early strength and the later strength of concrete are improved. In the synthesis process, the dripping of various small monomers is carried out simultaneously, the use time is the same, and the dripping time of auxiliary materials is more than 0.5 h. The dropwise adding mode can enable each reactant to react more uniformly, stably, fully, coordinately, stably and effectively, and each applied component is respectively attractive, reasonably combined, closely matched and synergistic, so that the molecular structure of the water reducing agent is optimized, the performance is improved, and the efficacy, the quality and the stability of the product are improved.
The early-strength polycarboxylate water reducing agent prepared by the invention can effectively improve the pore structure of concrete, increase the compactness of concrete, improve the performances of the concrete such as frost resistance, carbonization resistance, corrosion resistance, elastic modulus, impermeability and the like, and can reduce the drying shrinkage and creep of the concrete. The early-strength polycarboxylic acid water reducing agent produced by the invention not only greatly improves the early strength, leads to early demoulding and improves the turnover rate of a template, but also can shorten the construction period and accelerate the construction progress and labor productivity.
Detailed Description
The present invention will be described in detail with reference to examples. The scope of protection of the invention is not limited to the embodiments, and any modification made by those skilled in the art within the scope defined by the claims also falls within the scope of protection of the invention.
The early-strength polycarboxylate water reducer is synthesized by introducing monomer high molecular weight (molecular weight M is 5000) isopentenol polyoxyethylene ether and 3-allyloxy-1-hydroxypropanesulfonic acid with water reducing function, monomer formic acid/dimethylaminoethyl acrylate, 3-acryloxy-2-hydroxypropyl trimethyl ammonium chloride and N-hydroxyethyl-N' -acryloyl urea with early strength, and monomer methoxyethoxyethyl acrylate with slump retaining function into a synthesis process under the influence of a molecular structure on product performance, and neutralizing with organic base triethanolamine with early strength and organic base triisopropanolamine with late strength after reaction is finished.
The invention uses the following main raw materials: isopentenol polyoxyethylene ether
(molecular weight: 5000, hereinafter referred to as macromonomer), acrylic acid (CH)2CHCOOH), formic acid (HCOOH), methoxyethoxyethyl acrylate (CH)2＝CHCOOCH2CH2OCH2CH2OCH3) Dimethylaminoethyl acrylate [ CH2＝CHCOOCH2CH2N(CH3)2]3-acryloyloxy-2-hydroxypropyltrimethylammonium chloride (content: 80%) [ CH2＝CHCOOCH2CHOHCH2N+(CH3)3Cl-]3-mercaptopropionic acid (HSCH)2CH2COOH), N-hydroxyethyl-N' -acryloylurea (CH)2＝CHCONHCONHCH2CH2OH), 3-allyloxy-1-hydroxypropanesulfonic acid (CH)2＝CHCH2OCH2CH2CHOHSO3H) Triethanolamine [ N (CH)2CH2OH)3](85% strength), triisopropanolamine [ N (CH) ]2CHOHCH3)3]Ammonium persulfate (concentration of 85%), hydrogen peroxide (concentration of 27.5%) and vitamin C.
Wherein the monomer with the water reducing function is as follows: prenol polyoxyethylene ether, acrylic acid and 3-allyloxy-1-hydroxypropanesulfonic acid; the monomers with early strength function are: dimethylaminoethyl formate acrylate, 3-acryloyloxy-2-hydroxypropyltrimethylammonium chloride and N-hydroxyethyl-N' -acryloylurea; the monomer with the functions of plastic and slump retention is as follows: methoxyethoxyethyl acrylate.
Formic acid and dimethylaminoethyl acrylate are raw materials for synthesizing formic acid and dimethylaminoethyl acrylate. Ammonium persulfate and hydrogen peroxide are used as an initiator of polymerization reaction, and vitamin C is used as a reducing agent of polymerization reaction, so that an oxidation-reduction system is formed. 3-mercaptopropionic acid is a molecular weight regulator of the polymerization reaction, and triethanolamine and triisopropanolamine are neutralizers after the polymerization reaction is finished.
The preparation process of the early-strength polycarboxylic acid water reducer comprises the following three steps:
the first step is as follows: formic acid-acrylic acid dimethylamino ethyl ester [ CH2＝CHCOOCH2CH2N+H(CH3)2HCOO-]Preparation of
The preparation method comprises the steps of adding 92g of deionized water and 92g of formic acid into a 1000mL four-neck flask, dripping 286g of dimethylaminoethyl acrylate with equal molar weight by using a peristaltic pump under stirring at constant temperature of 15 ℃, and finishing dripping within 2.0 h;
and continuously reacting for 1.5h at 15 ℃ after the dripping is finished, and adding 286g of deionized water to ensure that the solid content of the reaction product is 50 percent (by mass) to obtain the aqueous solution of the formic acid-dimethylaminoethyl acrylate.
The second step is as follows: preparation of dropping liquid
Liquid A: 4.5-6.0 percent (mass) of acrylic acid based on the mass of the prenyl alcohol polyoxyethylene ether and 1.5-2.5 percent (mass) of 3-allyloxy-1-hydroxy propane sulfonic acid based on the mass of the prenyl alcohol polyoxyethylene ether are prepared into 60 percent (mass) aqueous solution;
and liquid B: a 50% by mass aqueous solution prepared from 2.5-4.0% by mass of prenyl alcohol polyoxyethylene ether, dimethylaminoethyl formate and acrylate and 2.5-4.0% by mass of prenyl alcohol polyoxyethylene ether, 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride;
liquid C: a 50 mass percent aqueous solution prepared from N-hydroxyethyl-N '-acrylurea and methoxyethoxyethyl acrylate, wherein the mass percent of the N-hydroxyethyl-N' -acrylurea is 0.5 to 1.5 mass percent of the mass of the prenyl alcohol polyoxyethylene ether, and the mass percent of the methoxyethoxy ethyl acrylate is 2.5 to 4.0 mass percent of the mass of the prenyl alcohol polyoxyethylene ether;
liquid D: 0.2 percent (mass) of vitamin C and 0.4 percent (mass) of 3-mercaptopropionic acid are prepared into 5 percent (mass) of water solution, and the total mass of the monomers is the total mass of all monomers participating in polymerization;
fifthly, neutralizing liquid: and preparing a mixed solution by using 65% of triethanolamine and 35% of triisopropanolamine in the theoretical molar weight of acrylic acid.
The third step: preparation of early-strength polycarboxylic acid water reducer
The method comprises the steps of adding 700g of isopentenol polyoxyethylene ether macromonomer with the molecular weight of 5000 and 376.9g of deionized water into a 2000mL four-neck flask, heating to 30 ℃, and stirring to dissolve the isopentenol polyoxyethylene ether macromonomer;
and adding ammonium persulfate accounting for 0.8 percent (mass) of the total mass of the monomers and hydrogen peroxide accounting for 0.4 percent (mass) of the total mass of the monomers after the prenol polyoxyethylene ether macromonomer is dissolved, and stirring for 15min to be uniform. And respectively and simultaneously dripping the solution A, the solution B, the solution C and the solution D by using a peristaltic pump at 30 ℃, wherein the solution A, the solution B and the solution C are respectively dripped for 3.5 hours, and the solution D is dripped for 4.0 hours. Because the reaction is exothermic, the temperature rise phenomenon exists in the dropping process, and the temperature is not controlled; after all the dropwise adding is finished, continuously preserving the heat and reacting for 1.5h at the temperature of the end of the dropwise adding;
and thirdly, cooling the temperature to 30 ℃, adding 65% triethanolamine of the theoretical molar weight of the neutralized acrylic acid and 35% triisopropanolamine of the theoretical molar weight of the neutralized acrylic acid for neutralization, and supplementing deionized water to enable the solid content of the product to be 40% (by mass), thereby obtaining the early-strength polycarboxylic acid water reducer.
For understanding the present invention, the preparation method provided by the present invention will be described in detail below with reference to specific embodiments.
Example 1
(1) Adding 32.7g of deionized water, 17.5g of 3-allyloxy-1-hydroxypropanesulfonic acid and 31.5g of acrylic acid into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid A;
(2) adding 35g of 50% dimethylaminoethyl formate and acrylate, 35g of 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride and 21g of deionized water into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid B;
(3) adding 35g of deionized water, 10.5g N-hydroxyethyl-N' -acrylurea and 24.5g of methoxyethoxyethyl acrylate into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid C;
(4) adding 94.62g of deionized water, 1.66g of vitamin C and 3.32g of 3-mercaptopropionic acid into a 250mL conical flask, and uniformly mixing to obtain a dropping liquid D;
(5) 700g of prenyl polyoxyethylene ether macromonomer and 376.9g of deionized water were placed in a 2000mL four-neck flask, and heated and stirred to be dissolved. After dissolving the prenyl polyoxyethylene ether macromonomer, adding 6.64g of ammonium persulfate and 3.32g of hydrogen peroxide, stirring uniformly, and respectively dropwise adding the solution A, the solution B, the solution C and the solution D at 30 ℃ by using a peristaltic pump. Wherein, the liquid A, the liquid B and the liquid C are respectively dripped at constant speed for 3.5h, and the liquid D is dripped at constant speed for 4.0 h. Because the reaction is exothermic, the temperature rise phenomenon exists in the dropping process, and the temperature is not controlled.
After the dropwise addition is finished, the reaction is continued for 1.5h at the temperature. And (3) cooling to 30 ℃, adding 49.85g of triethanolamine as an organic base and 34.41g of triisopropanolamine for neutralization, and supplementing deionized water to ensure that the solid content of the product is 40%. The obtained early strength type polycarboxylic acid water reducing agent is SK-ZQ-1.
Example 2
(1) Adding 34.1g of deionized water, 14.0g of 3-allyloxy-1-hydroxypropanesulfonic acid and 37.1g of acrylic acid into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid A;
(2) 42g of 50% dimethylaminoethyl formate-acrylate, 30.63g of 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride and 18.37g of deionized water are added into a 250mL conical flask and uniformly mixed to obtain dropwise added liquid B;
(3) adding 35g of deionized water, 7.0g of 7.0g N-hydroxyethyl-N' -acrylurea and 28.0g of methoxyethoxyethyl acrylate into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid C;
(4) adding 94.81g of deionized water, 1.66g of vitamin C and 3.33g of 3-mercaptopropionic acid into a 250mL conical flask, and uniformly mixing to obtain dropwise D liquid;
(5) 700g of prenyl polyoxyethylene ether macromonomer and 376.9g of deionized water were placed in a 2000mL four-neck flask, and heated and stirred to be dissolved. Dissolving the prenol polyoxyethylene ether macromonomer, adding 6.65g of ammonium persulfate and 3.33g of hydrogen peroxide, stirring uniformly, and respectively dropwise adding the solution A, the solution B, the solution C and the solution D at 30 ℃ by using a peristaltic pump. Wherein, the liquid A, the liquid B and the liquid C are respectively dripped at constant speed for 3.5h, and the liquid D is dripped at constant speed for 4.0 h. Because the reaction is exothermic, the temperature rise phenomenon exists in the dropping process, and the temperature is not controlled.
After the dropwise addition is finished, the reaction is continued for 1.5h at the temperature. Cooling to 30 ℃, adding 58.71g of organic alkali triethanolamine and 40.53g of triisopropanolamine for neutralization, and supplementing deionized water to ensure that the solid content of the product is 40%. The obtained early strength type polycarboxylic acid water reducing agent is SK-ZQ-2.
Example 3
(1) Adding 35.0g of deionized water, 10.5g of 3-allyloxy-1-hydroxypropanesulfonic acid and 42.0g of acrylic acid into a 250mL conical flask, and uniformly mixing to obtain dropwise A liquid;
(2) 56.0g of 50% dimethylaminoethyl formate-acrylate, 21.88g of 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride and 13.12g of deionized water are added into a 250mL conical flask and uniformly mixed to obtain dropwise added liquid B;
(3) adding 21.0g of deionized water, 3.5g N-hydroxyethyl-N' -acrylurea and 17.5g of methoxyethoxyethyl acrylate into a 250mL conical flask, and uniformly mixing to obtain dropwise liquid C;
(4) adding 93.48g of deionized water, 1.64g of vitamin C and 3.28g of 3-mercaptopropionic acid into a 250mL conical flask, and uniformly mixing to obtain dropwise D liquid;
(5) 700g of prenyl polyoxyethylene ether macromonomer and 376.9g of deionized water were placed in a 2000mL four-neck flask, and heated and stirred to be dissolved. Dissolving the prenol polyoxyethylene ether macromonomer, adding 6.55g of ammonium persulfate and 3.28g of hydrogen peroxide, stirring uniformly, and respectively dropwise adding the solution A, the solution B, the solution C and the solution D at 30 ℃ by using a peristaltic pump. Wherein, the liquid A, the liquid B and the liquid C are respectively dripped at constant speed for 3.5h, and the liquid D is dripped at constant speed for 4.0 h. Because the reaction is exothermic, the temperature rise phenomenon exists in the dropping process, and the temperature is not controlled.
After the dropwise addition is finished, the reaction is continued for 1.5h at the temperature. When the temperature is reduced to 30 ℃, 66.47g of triethanolamine as an organic base and 45.88g of triisopropanolamine are added for neutralization, and deionized water is supplemented to ensure that the solid content of the product is 40%. The obtained early strength type polycarboxylic acid water reducing agent is SK-ZQ-3.
In order to verify the performance of the product, the product is compared with the common polycarboxylic acid water reducing agent product and foreign products of the company. SK-ZQ-1, SK-ZQ-2, SK-ZQ-3 are the early strength type polycarboxylic acids water reducing agent synthesized by the invention, SK-JD-9 is the ordinary polycarboxylic acids water reducing agent, the foreign product is also the early strength type polycarboxylic acids water reducing agent.
The concrete experiment is compared and tested according to GB 8076 + 2008 concrete admixture, GB/T50080-2011 Standard test method for common concrete mixture Performance, GB/T50081-2011 Standard test method for common concrete mechanical Performance. P.O 42.5.5 kumquat cement, I-grade fly ash, washed medium sand (fineness modulus 2.5), washed small crushed stones (particle size 5-10 mm, continuous size fraction), washed large crushed stones (particle size 10-25 mm, continuous size fraction) and drinking water are adopted. The experiment is carried out by referring to the mix proportion of the concrete of the subway segments in the urban traffic track segment factory, and the mix proportion of the concrete is shown in table 1.
TABLE 1 concrete mix proportion
| Cement | Fly ash | Medium sand | Large crushed stone | Small crushed stone | Water (W) |
| 400 | 50 | 682 | 797 | 341 | 144 |
Note: water cement ratio of 0.32, sand ratio of 0.37, and crushed stone ratio of 70%/30%
When the concrete is mixed, the mixing amount of the additive is adjusted according to the state of the concrete, so that the machine-out slump of the concrete is 60-80 mm, the machine-out slump of the concrete is measured, then, the mold filling is carried out, and the compressive strength of steam curing (50 ℃,4h), normal-temperature curing (20 ℃,7h), 1d, 3d, 7d and 28d is measured. The concrete test results are shown in table 2.
TABLE 2 test results of concrete experiments
Note: 1. the mixing amount is the folding and fixing mixing amount of the total amount of the cementing material; 2. curing at normal temperature, namely naturally curing in a concrete chamber; 3.1 d, 3d, 7d and 28d are maintained in a standard curing chamber; 4. the steam curing is carried out after the mold is filled and the standing is carried out for 2 hours.
As can be seen from table 2, in the design of the molecular structure of the synthetic water reducer, the introduced compounds respectively play different roles in concrete due to the use of monomer high molecular weight (molecular weight M ═ 5000) prenol polyoxyethylene ether having a water reducing function, 3-allyloxy-1-hydroxypropanesulfonic acid, and monomer dimethylaminoethyl formate/acrylate having an early strength function, 3-acryloxy-2-hydroxypropyltrimethylammonium chloride, N-hydroxyethyl-N' -acryloylurea, and monomer methoxyethoxyethyl acrylate having a slump retention function. The polymer uses large-molecular-weight macromonomer, namely long-chain macromonomer, and can form a thicker three-dimensional surrounding layer on the surface of cement particles, thereby being beneficial to fast dispersion and high dispersion of cement materials, accelerating hydration of cement and advancing the setting time. Sulfonic acid group and ureide compounds, namely 3-allyloxy-1-hydroxypropanesulfonic acid and N-hydroxyethyl-N' -acrylurea, introduced into the polymer can improve the high dispersibility of the polymer and promote the hydration reaction of minerals in cement. The cationic monomers of formic acid-dimethylaminoethyl acrylate and 3-acryloxy-2-hydroxypropyl trimethyl ammonium chloride are introduced into polymer molecules, can be adsorbed on electronegative cement minerals, can promote the hydration process of cement, shorten the setting time of the cement, and are beneficial to quick setting and early strength; the methoxy ethoxy ethyl acrylate is introduced to play a role in plastic retention and slump loss reduction, and the repeated plastering and light collection during the standing waiting period after the concrete of the component is poured and molded can be ensured. After the reaction is finished, organic alkali triethanolamine and triisopropanolamine are adopted for neutralization, so that the alkali content of the product can be reduced, and the early and later strength of the concrete can be improved. Therefore, in the design of the molecular structure of the synthetic water reducing agent, the types, functions and characteristics of the comonomers and the component proportion of each block chain link are considered so as to endow the water reducing agent with new functions and excellent performance.
Claims (3)
1. An early strength type polycarboxylic acid water reducing agent is characterized in that: in the synthesis process, monomer isopentenol polyoxyethylene ether with molecular weight M being 5000 large molecular weight and having water reducing function, 3-allyloxy-1-hydroxypropanesulfonic acid and monomer formic acid with early strength function are introduced·And after the reaction is finished, neutralizing by using triethanolamine which is an organic base with early strength and triisopropanolamine which is an organic base with later strength to synthesize the early-strength polycarboxylic acid water reducer.
2. A preparation method of an early-strength polycarboxylic acid water reducer comprises the following steps:
the first step is as follows: formic acid·Preparation of dimethylaminoethyl acrylate
Adding quantitative formic acid and deionized water with equal mass into a 1000mL four-neck flask, and dripping dimethylaminoethyl acrylate with equal molar quantity with formic acid by using a peristaltic pump under the stirring at the constant temperature of 15 ℃; after reacting for 1.5h at 15 ℃, deionized water is added to ensure that the solid content is 50 percent (mass) to obtain formic acid·Acrylic acid dimethylamino groupEthyl ester aqueous solution;
the second step is that: preparation of early-strength polycarboxylic acid water reducer
Adding a certain amount of prenyl polyoxyethylene ether macromonomer with the molecular weight of 5000 and a certain amount of deionized water into a 2000mL four-neck flask, heating to 30 ℃, and stirring for dissolving. Dissolving prenol polyoxyethylene ether, adding ammonium persulfate with the total mass of 0.8% (mass) of the monomer and hydrogen peroxide with the total mass of 0.4% (mass) of the monomer, and uniformly stirring; respectively dripping the solution A, the solution B, the solution C and the solution D by using a peristaltic pump at the temperature of 30 ℃, wherein the solution A, the solution B and the solution C are respectively dripped for 3.5 hours, and the solution D is dripped for 4.0 hours; the temperature is not controlled in the dripping process, and after the dripping is finished completely, the heat preservation reaction is continued for 1.5h at the finishing temperature of the dripping; cooling to 30 ℃, adding organic alkali triethanolamine and triisopropanolamine for neutralization, and supplementing deionized water to ensure that the solid content of the product is 40% (by mass), thereby obtaining the early-strength polycarboxylic acid water reducer; the solution A is a 60 mass percent aqueous solution consisting of 4.5 to 6.0 mass percent of acrylic acid and 1.5 to 2.5 mass percent of 3-allyloxy-1-hydroxypropanesulfonic acid based on the mass of the prenol polyoxyethylene ether; the solution B is a 50 mass% aqueous solution consisting of 2.5-4.0 mass% of prenyl alcohol polyoxyethylene ether, namely dimethylaminoethyl formate and acrylate, and 2.5-4.0 mass% of 3-acryloyloxy-2-hydroxypropyl trimethyl ammonium chloride; the solution C is a 50 mass percent aqueous solution consisting of 0.5 to 1.5 mass percent of N-hydroxyethyl-N' -acrylurea and 2.5 to 4.0 mass percent of methoxyethoxyethyl acrylate based on the mass of the prenyl alcohol polyoxyethylene ether; the solution D is a 5 mass percent aqueous solution consisting of 0.2 mass percent of vitamin C and 0.4 mass percent of 3-mercaptopropionic acid based on the total mass of the monomers.
3. The method for preparing the early strength type polycarboxylic acid water reducing agent according to claim 2, characterized in that: the addition amount of the organic alkali triethanolamine is 65% of the theoretical molar amount of acrylic acid, and the addition amount of the triisopropanolamine is 35% of the theoretical molar amount of acrylic acid.
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