CN111961148A

CN111961148A - Reaction air-entraining type polycarboxylate superplasticizer and preparation method thereof

Info

Publication number: CN111961148A
Application number: CN202010891620.4A
Authority: CN
Inventors: 谭洪波; 郭文斌; 马保国; 李相国; 蹇守卫; 黄健
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2020-11-20
Anticipated expiration: 2040-08-31
Also published as: CN111961148B

Abstract

The invention discloses a reaction air-entraining type polycarboxylate superplasticizer and a preparation method thereof. The water reducer can release ammonia gas by utilizing the alkaline environment of cement hydration, has the effects of air entraining and water reducing, has good water reducing effect, has the water reducing rate of 20-40% and the air content increased by 1-4% when the mixing amount of the water reducer is 0.1-0.3%, can obviously improve the fluidity of concrete, can improve the anti-segregation and anti-bleeding capacity of the concrete, and improves the workability of the concrete.

Description

Reaction air-entraining type polycarboxylate superplasticizer and preparation method thereof

Technical Field

The invention belongs to the field of building materials, and particularly relates to a reaction air-entraining type polycarboxylate superplasticizer and a preparation method thereof.

Background

In recent years, with the increasing demand of building concrete, higher requirements are placed on the additive added into the concrete, and particularly, the development of high-strength self-compacting concrete in recent years pushes the concrete additive to develop towards the directions of high water reduction, high slump loss resistance and high adaptability to concrete materials. The polycarboxylic acid water reducing agent is a third-generation high-performance water reducing agent which is formed after a calcium water reducing agent and a naphthalene water reducing agent, generally, an unsaturated carboxylic acid compound and unsaturated modified polyether (such as 2-propenyl glycol ether and 2-methyl propenyl glycol ether) which can perform free radical copolymerization reaction are subjected to free radical copolymerization reaction to synthesize a product molecule with a comb-shaped structure, and the dispersibility of a concrete mixture is improved through the electrostatic repulsion effect and the steric hindrance effect, so that the rheological property of concrete is improved, the workability is improved, and the polycarboxylic acid water reducing agent has the characteristics of low mixing amount, high water reducing rate, good slump retaining property and the like, and has a good application prospect.

Patent 202010170935.X discloses a phenyl sulfonic block polymer modified polycarboxylic acid water reducing agent and a preparation method thereof, and the proposed water reducing agent comprises the following components: 348-365 parts of polyether macromonomer, 18-26 parts of acrylic acid, 10-14 parts of sulfonic acid monomer, 3-8 parts of benzene ring monomer, 3.2-4.3 parts of initiator, 1.1-1.5 parts of chain transfer agent, and the balance of water, wherein the total mass is 1000 parts, and the solid content is 40%. Compared with the common water reducing agent, the polycarboxylic acid water reducing agent prepared by the invention has better adsorption and dispersion effects, but the method has the defects of complicated steps, high raw material cost, great pollution in the production process and the like.

Patent 201911424855.6 discloses a polycarboxylic acid water reducing agent for lightweight concrete and a preparation method thereof, and the proposed water reducing agent comprises the following components: 30-38% of a macromonomer, 0.2-0.5% of hydrogen peroxide, 2.8-4.8% of acrylic acid, 1.0-3.0% of a modifier, 0.1-0.2% of mercaptopropionic acid, 0.05-0.12% of vitamin C, 0.3-0.8% of a regulator, 0.07-0.1% of sodium hydroxide and the balance of water. The water reducing agent of the invention enables the mother solution molecules to fully wrap cement particles by improving the dropping material, enables the wrapping performance of the lightweight concrete to adapt to the requirements of various materials, but has complex synthesis process and poor compatibility with other additives.

Patent 201911276458.9 discloses a method for synthesizing a polycarboxylic acid water reducing agent at normal temperature, and the proposed water reducing agent comprises the following components: 100 parts of unsaturated polyoxyethylene ether macromonomer, 0.6-0.8 part of hydrogen peroxide, 5-10 parts of unsaturated carboxylic acid, 0.1-0.3 part of reducing agent and 0.5-0.8 part of chain transfer agent. The unsaturated polyoxyethylene ether macromonomer is methyl allyl polyoxyethylene ether or isoamylol polyoxyethylene ether; the unsaturated carboxylic acid is acrylic acid or methacrylic acid; the reducing agent is vitamin C or sodium thiosulfate; the chain transfer agent is thioglycolic acid or mercaptopropionic acid. The water reducer has stable synthesis process, but has poor adaptability with cement and quick slump loss, and greatly reduces the using effect of the water reducer.

Along with the development of commercial concrete, people have higher and higher requirements on the fluidity and the loss of fluidity over time of the polycarboxylic acid water reducing agent and the frost resistance and durability of the concrete. Therefore, the concrete polycarboxylate superplasticizer with high water reducing rate and high freezing resistance and durability is synthesized, the application range of the polycarboxylate superplasticizer can be further widened, and the industrial application with high efficiency and multiple functions is realized.

Disclosure of Invention

Based on the above, one of the purposes of the invention is to provide a reaction air-entraining type polycarboxylate water reducer, which improves the fluidity of concrete and simultaneously introduces uniformly closed micro-bubbles to improve the frost resistance and durability of the concrete, wherein 0.1-0.3% (based on a cementing material) of the water reducer is added into the concrete, the water reducing rate reaches 20-40%, and the gas content is increased by 1-4%.

In order to realize the purpose of the invention, the specific technical scheme is as follows:

the reaction air entraining type polycarboxylate superplasticizer mainly comprises a random copolymer prepared by carrying out aqueous solution free radical polymerization on polyethylene glycol ether and acrylic acid, and has a molecular structural formula as follows:

wherein a: b is 1: 3 to 5, n is 9 to 20, and the number average molecular weight of the random copolymer is 10000 to 100000.

According to the scheme, the number average molecular weight of the polyethylene glycol ether is 500-1000.

According to the scheme, the molar ratio of the polyethylene glycol ether to the acrylic acid is 1: 1 to 2.

The second purpose of the invention is to provide a preparation method of the reaction air-entraining type polycarboxylate superplasticizer, which comprises the following specific steps:

firstly, weighing raw materials in proportion for later use;

secondly, adding polyethylene glycol ether into water, stirring and dissolving to obtain a solution, then adding acrylic acid into the obtained solution, stirring and mixing uniformly, adding an initiator and a chain transfer agent into the obtained mixed solution, and carrying out free radical polymerization reaction to obtain a reaction solution, wherein the reaction formula is as follows:

thirdly, slowly dropwise adding ammonia water (the mass concentration is 25-30%) into the reaction liquid prepared in the second step, and adjusting the pH value of the reaction liquid to be 5-6 to obtain the reaction air entraining type polycarboxylate superplasticizer, wherein the reaction formula of the ammonia water is as follows:

according to the scheme, in the second step, the polyethylene glycol ether is added into water, stirred and dissolved to obtain a solution, and the mass concentration of the polyethylene glycol ether in the solution is 35-45%.

According to the scheme, the initiator in the second step is ammonium persulfate, and the addition amount of the initiator is 0.2-0.7% of the total mass of the polyethylene glycol ether and the acrylic acid.

According to the scheme, the chain transfer agent in the second step is one or a mixture of 2-mercaptoethanol and 3-mercapto-1-propanol, and the addition amount of the chain transfer agent is 0.2-0.5% of the total mass of the polyglycol ether and the acrylic acid.

According to the scheme, the free radical polymerization reaction conditions in the second step are as follows: reacting for 4.5-5 h at 60-65 ℃.

The third purpose of the invention is to provide concrete containing the reaction air-entraining type polycarboxylate superplasticizer, when the doping amount of the reaction air-entraining type polycarboxylate superplasticizer in the concrete is 0.1-0.3% (based on the mass of the cementing material), the water reducing rate is 20-40%, the air content is increased by 1-4%, the frost resistance and durability of the concrete can be effectively improved, and the fluidity of cement paste can be remarkably improved by the water reducing agent.

The invention has the beneficial effects that: 1. compared with the existing similar carboxylic acid water reducing agent, the water reducing agent has obvious water reducing effect, is not influenced by other chemical components, and has good dispersibility, low mixing amount and good adsorption effect in concrete. Can be used as an auxiliary material to be widely applied to the field of concrete admixtures; 2. the preparation process is simple, heating is not needed, the reaction period is short, the environment is not polluted, and the preparation cost is low.

The specific implementation mode is as follows:

in order to verify the experimental effect of the present invention, the applicant performed specific examples to verify the beneficial effects of the present invention. The examples are given by way of illustration and are in no way limiting to the present invention. The protection scope of the invention is subject to the claims.

The specific implementation process is as follows: firstly adding polyethylene glycol ether (with the number average molecular weight of 1000) into water, stirring and dissolving to obtain a polyethylene glycol ether solution, then adding acrylic acid into the solution, stirring and mixing uniformly, finally adding ammonium persulfate and a chain transfer agent into the obtained mixed solution to carry out free radical polymerization reaction, wherein the reaction temperature is 65 ℃, the reaction time is 4.5h, finally slowly dropwise adding ammonia water with the mass concentration of 30% into the obtained reaction solution, and adjusting the pH value of the reaction solution to 5-6 to obtain the reaction air-entraining type polycarboxylic acid water reducer. The raw material component ratios and the parameters of the random copolymer obtained in comparative example 1 and examples 1 to 5 are shown in Table 1.

TABLE 1

The application example is as follows:

the products of comparative example 1 and examples 1 to 5 above were subjected to performance evaluation. The air content and the water reducing rate are tested according to GB8076-2008 concrete admixture, the fluidity of the cement paste is tested according to GB/T8077-2000 concrete admixture homogeneity test method and the water-cement ratio of 0.29, and the initial fluidity of the freshly mixed cement paste and the time-lapse fluidity of 2h of the paste. The cement used in the test is Huaxin cement PO 42.5 grade. The admixture ratio of the cement paste is shown in Table 2, and the concrete test results after the water reducing agent of comparative example 1 and examples 1 to 5 was shown in Table 3 below (the increase in the gas content in Table 3 is a value of percentage increase in the gas content relative to that of comparative example 1).

TABLE 2 Cement paste mixing ratio

Cement/g	Water/g
		300	87

TABLE 3 test results

As can be seen from Table 2, when 0.1-0.3% (based on the cementing material) of the reaction air-entraining type polycarboxylate water reducing agent prepared in the embodiments 1-5 is added into concrete, the water reducing rate is 20-40%, the air content is increased by 1-4%, the frost resistance and durability of the concrete can be effectively improved, and the water reducing agent can remarkably improve the fluidity of cement paste.

Claims

1. The reaction air entraining type polycarboxylate superplasticizer is characterized in that the main component of the reaction air entraining type polycarboxylate superplasticizer is a random copolymer prepared by polyethylene glycol ether and acrylic acid through aqueous solution free radical polymerization, and the molecular structural formula of the random copolymer is as follows:

2. The reactive air entraining type polycarboxylate superplasticizer according to claim 1, characterized in that the number average molecular weight of the polyglycol ether is 500-1000.

3. The reactive air entraining type polycarboxylate superplasticizer according to claim 1, characterized in that the molar ratio of the polyethylene glycol ether to the acrylic acid is 1: 1 to 2.

4. The preparation method of the reaction air-entraining type polycarboxylate superplasticizer according to any one of claims 1 to 3, which is characterized by comprising the following specific steps:

firstly, weighing raw materials in proportion for later use;

secondly, adding polyethylene glycol ether into water, stirring and dissolving to obtain a solution, then adding acrylic acid into the obtained solution, stirring and mixing uniformly, and then adding an initiator and a chain transfer agent into the obtained mixed solution to carry out free radical polymerization reaction to obtain a reaction solution;

and thirdly, slowly dropwise adding ammonia water into the reaction liquid prepared in the second step, and adjusting the pH value of the reaction liquid to 5-6 to obtain the reaction air entraining type polycarboxylate superplasticizer.

5. The preparation method of the reactive air-entraining type polycarboxylate superplasticizer according to claim 4, characterized by adding polyglycol ether into water in the second step, stirring and dissolving to obtain a solution, wherein the mass concentration of the polyglycol ether in the solution is 35-45%.

6. The preparation method of the reactive air-entraining type polycarboxylate superplasticizer according to claim 4, characterized in that the initiator in the second step is ammonium persulfate, and the addition amount is 0.2-0.7% of the total mass of the polyglycol ether and the acrylic acid.

7. The preparation method of the reactive air-entraining type polycarboxylate superplasticizer according to claim 4, wherein the chain transfer agent in the second step is one or a mixture of 2-mercaptoethanol and 3-mercapto-1-propanol, and the addition amount of the chain transfer agent is 0.2-0.5% of the total mass of the polyglycol ether and the acrylic acid.

8. The preparation method of the reactive air-entraining type polycarboxylate superplasticizer according to claim 4, characterized in that the conditions of the radical polymerization reaction in the second step are as follows: reacting for 4.5-5 h at 60-65 ℃.

9. The concrete containing the reaction air-entraining type polycarboxylate water reducer as defined in any one of claims 1 to 3, wherein the reaction air-entraining type polycarboxylate water reducer is incorporated in the concrete in an amount of 0.1 to 0.3%.