A kind of machine-made sand concrete water-retaining agent, preparation method and use method thereof

Abstract

This invention relates to a water-retaining agent for manufactured sand concrete, its preparation method, and its application method. By weight, it comprises 300-500 parts of methyl allyl polyoxyethylene ether, 100-200 parts of acrylamide, 1-2.5 parts of alkyl polyoxyethylene methacrylate, 10-15 parts of N,N-methylenebisacrylamide, 18-45 parts of acrylic acid, 10-25 parts of salt-resistant monomer, 2-8 parts of initiator, 0.5-8 parts of reducing agent, and 3000-5600 parts of deionized water. The design of this concrete water-retaining agent addresses the technical problems of existing domestically used water-retaining agents negatively impacting concrete fluidity, reducing workability, exhibiting poor stability in strongly alkaline concrete media, and failing to provide sustained improvement in the water retention performance of concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a water-retaining agent for manufactured sand concrete, its preparation method, and its application method. Background Technology

[0002] The limited mining of natural river sand has led to the increasingly widespread use of manufactured sand in concrete. Manufactured sand, produced by mechanically crushing and screening rocks, generally suffers from defects such as poor particle shape, numerous sharp edges, and large fluctuations in stone powder content, resulting in poor workability and a tendency for segregation and bleeding in concrete. Adding water-retaining agents to admixtures is a common technique for addressing the segregation and bleeding problems in manufactured sand concrete.

[0003] Currently, commonly used water-retaining agents in China include polyacrylamide, polyvinyl alcohol, cellulose ether, and maltodextrin. However, these agents also have shortcomings in application. First, they negatively impact the fluidity of concrete, reducing its workability. Second, they are prone to hydrolysis and have poor stability in the strongly alkaline medium of concrete, failing to provide sustained improvement in the water retention performance of concrete. Furthermore, they exhibit certain compatibility issues with commonly used polycarboxylate superplasticizers. Summary of the Invention

[0004] The purpose of this invention is to provide a water-retaining agent for manufactured sand concrete, its preparation method, and its application method. The design of the concrete water-retaining agent aims to solve the technical problems of commonly used water-retaining agents in China, which have a negative impact on the fluidity of concrete, resulting in reduced workability, easy hydrolysis in the strongly alkaline medium of concrete, poor stability, and inability to improve the water retention performance of concrete in a lasting manner.

[0005] The present invention provides a water-retaining agent for manufactured sand concrete, comprising, by weight, 300-500 parts of methyl allyl polyoxyethylene ether, 100-200 parts of acrylamide, 1-2.5 parts of alkyl polyoxyethylene methacrylate, 10-15 parts of N,N-methylenebisacrylamide, 18-45 parts of acrylic acid, 10-25 parts of salt-resistant monomer, 2-8 parts of initiator, 0.5-8 parts of reducing agent, and 3000-5600 parts of deionized water.

[0006] Preferably, the molecular formula of alkyl polyoxyethylene methacrylate is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 20-30, m = 18-22.

[0007] Preferably, the salt-resistant monomer is one or two of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid.

[0008] Preferably, the initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate.

[0009] Preferably, the reducing agent is one of sodium bisulfite and ascorbic acid.

[0010] Preferably, the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is (2-3):1.

[0011] The present invention also provides a method for preparing a water-retaining agent for manufactured sand concrete as described in any one of the above-mentioned methods, comprising the following steps:

[0012] Methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, initiator, and deionized water are mixed and stirred at a certain temperature to dissolve, thus obtaining the base solution.

[0013] Alkyl polyoxyethylene methacrylate and acrylic acid are dissolved in deionized water to obtain component A, and salt-resistant monomer and reducing agent are dissolved in deionized water to obtain component B.

[0014] Components A and B are added dropwise to the bottom liquid. After the addition is complete, the mixture is stirred for a certain period of time to obtain a water-retaining agent for manufactured sand concrete.

[0015] Preferably, methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, and initiator are mixed and stirred at 20-60°C for 1-2 hours.

[0016] Preferably, the mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is (8-10):1:1.

[0017] The present invention also provides a method for using the water-retaining agent for manufactured sand concrete as described in any one of the above-mentioned methods, characterized in that:

[0018] The water-retaining agent for manufactured sand concrete is added to the concrete, or the water-retaining agent for manufactured sand concrete is compounded with polycarboxylate superplasticizer and then added to the concrete.

[0019] Preferably, when the water-retaining agent for manufactured sand concrete is used in combination with the polycarboxylate superplasticizer, the mass ratio of the water-retaining agent for manufactured sand concrete to the polycarboxylate superplasticizer is (0.01-0.02):1;

[0020] Alternatively, the water-retaining agent for manufactured sand concrete can be directly added to the cementitious material, with a mass ratio of (0.0001-0.0004):1 between the water-retaining agent and the cementitious material.

[0021] The water-retaining agent for manufactured sand concrete, its preparation method, and its application method provided by this invention have the following advantages compared with the prior art:

[0022] 1. The water-retaining agent for manufactured sand concrete provided by this invention can effectively solve the segregation and bleeding phenomena of manufactured sand concrete and provide excellent water retention performance.

[0023] 2. The water-retaining agent for manufactured sand concrete provided by the present invention uses alkyl polyoxyethylene methacrylate with a hydrophobic long chain structure. Through the hydrophobic association effect of the hydrophobic long chain structure of alkyl polyoxyethylene methacrylate, stable micro-nano bubbles can be introduced into the manufactured sand concrete. While enhancing the water retention effect of the water-retaining agent, it can also improve the fluidity of concrete through the "ball effect", so that the concrete has good workability.

[0024] 3. The water-retaining agent for manufactured sand concrete provided by this invention uses salt-resistant monomers. The sulfonic acid functional groups in the structure of the salt-resistant monomers have good salt resistance properties and can continuously exert good water retention effects in high-salt and high-alkali environments of concrete, making the water retention performance of concrete more durable.

[0025] 4. The water-retaining agent for manufactured sand concrete provided by the present invention limits the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether, ensuring a structure similar to that of polycarboxylate superplasticizer, which can provide a certain water-reducing effect while enhancing compatibility. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention provides a water-retaining agent for manufactured sand concrete, comprising, by weight, 300-500 parts of methyl allyl polyoxyethylene ether, 100-200 parts of acrylamide, 1-2.5 parts of alkyl polyoxyethylene methacrylate, 10-15 parts of N,N-methylenebisacrylamide, 18-45 parts of acrylic acid, 10-25 parts of salt-resistant monomer, 2-8 parts of initiator, 0.5-8 parts of reducing agent, and 3000-5600 parts of deionized water.

[0028] Specifically, the molecular formula of alkyl polyoxyethylene methacrylate is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 20-30, m = 18-22.

[0029] Specifically, the salt-resistant monomer is one or two of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid.

[0030] Specifically, the initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate.

[0031] Specifically, the reducing agent is one of sodium bisulfite or ascorbic acid.

[0032] Specifically, the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is (2-3):1.

[0033] The present invention also provides a method for preparing a water-retaining agent for manufactured sand concrete as described in any one of the above-mentioned methods, comprising the following steps:

[0034] S1) Mix methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, initiator, and deionized water, and stir to dissolve at a certain temperature to obtain the base solution;

[0035] S2) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve salt-resistant monomer and reducing agent in deionized water to obtain component B;

[0036] S3) Add components A and B dropwise to the bottom liquid. After the addition is complete, stir for a certain period of time to obtain the water-retaining agent for manufactured sand concrete.

[0037] Specifically, methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, and initiator are mixed and stirred at 20-60°C for 1-2 hours.

[0038] Specifically, the mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is (8-10):1:1.

[0039] The present invention also provides a method for using the water-retaining agent for manufactured sand concrete as described in any one of the above-mentioned methods, characterized in that:

[0040] The water-retaining agent for manufactured sand concrete is added to the concrete, or the water-retaining agent for manufactured sand concrete is compounded with polycarboxylate superplasticizer and then added to the concrete.

[0041] Preferably, when the water-retaining agent for manufactured sand concrete is used in combination with the polycarboxylate superplasticizer, the mass ratio of the water-retaining agent for manufactured sand concrete to the polycarboxylate superplasticizer is (0.01-0.02):1; or the water-retaining agent for manufactured sand concrete is directly added to the cementitious material, and the mass ratio of the water-retaining agent for manufactured sand concrete to the cementitious material is (0.0001-0.0004):1.

[0042] 1. The water-retaining agent for manufactured sand concrete provided by this invention utilizes alkyl polyoxyethylene methacrylate with a hydrophobic long-chain structure, introducing hydrophobic groups into the molecular structure of the water-retaining agent. Due to hydrophobic interactions, the hydrophobic groups on the water-retaining agent molecular chains cluster, causing intermolecular and intramolecular associations in the macromolecular chains, increasing the hydrodynamic volume and exhibiting good viscosity-enhancing properties. In the pore fluid of concrete, the increased solution polarity enhances the hydrophobic association effect, exhibiting good salt resistance. Furthermore, the microbubbles introduced during mixing can be stabilized by the association of the hydrophobic long chains, introducing microbubbles into the manufactured sand concrete. This enhances the water-retaining effect of the agent and improves the fluidity of the concrete through the "ball effect."

[0043] 2. The water-retaining agent for manufactured sand concrete provided by the present invention uses salt-resistant monomers. The sulfonic acid functional groups in the structure of the salt-resistant monomers have good salt resistance properties and can continuously exert good water retention effects in high-salt and high-alkali environments of concrete.

[0044] 3. The water-retaining agent for manufactured sand concrete provided by the present invention limits the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether, ensuring a structure similar to that of polycarboxylate superplasticizer, which can provide a certain water-reducing effect while enhancing compatibility.

[0045] 4. The mass ratio of the water-retaining agent for manufactured sand concrete to the cementitious material of the present invention is (0.0001-0.0004):1. A very small amount can improve the fluidity of concrete without affecting the mechanical properties of concrete such as compressive strength and flexural strength.

[0046] Example 1

[0047] Preparation of water-retaining agent for manufactured sand concrete (sample 1)

[0048] By weight, it includes 300 parts of methyl allyl polyoxyethylene ether, 100 parts of acrylamide, 1 part of alkyl polyoxyethylene methacrylate, 15 parts of N,N-methylenebisacrylamide, 18 parts of acrylic acid, 25 parts of sodium propylene sulfonate, 8 parts of potassium persulfate, 8 parts of sodium bisulfite, and 3000 parts of deionized water.

[0049] 101) Add methyl allyl polyoxyethylene ether, propylene, amide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 50°C until completely dissolved to obtain the bottom liquid;

[0050] 102) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve sodium propylene sulfonate and sodium bisulfite in deionized water to obtain component B.

[0051] 103) Add components A and B dropwise to the bottom liquid. The addition is completed in 2 hours. After stirring for 1 hour, the water-retaining agent for manufactured sand concrete (sample 1) is obtained. The water-retaining agent for manufactured sand concrete is a light blue liquid.

[0052] The molecular formula of the alkyl polyoxyethylene methacrylate in this embodiment is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 30 and m = 18.

[0053] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 8:1:1.

[0054] Example 2

[0055] Preparation of water-retaining agent for manufactured sand concrete (sample 2)

[0056] By weight, it includes 440 parts of methyl allyl polyoxyethylene ether, 160 parts of acrylamide, 2 parts of alkyl polyoxyethylene methacrylate, 10 parts of N,N-methylenebisacrylamide, 33 parts of acrylic acid, 15 parts of sodium styrene sulfonate, 4 parts of ammonium persulfate, 2 parts of sodium bisulfite, and 3500 parts of deionized water.

[0057] 201) Add methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 30°C until completely dissolved to obtain the bottom liquid;

[0058] 202) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve sodium styrene sulfonate and sodium bisulfite in deionized water to obtain component B;

[0059] 203) Components A and B were added dropwise to the bottom liquid. The addition was completed in 1 hour. After stirring for 1 hour, a light blue liquid water-retaining agent for manufactured sand concrete (sample 2) was obtained.

[0060] The molecular formula of the alkyl polyoxyethylene methacrylate in this embodiment is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 25 and m = 18.

[0061] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 9:1:1.

[0062] Example 3

[0063] Preparation of water-retaining agent for manufactured sand concrete (sample 3)

[0064] By weight, it includes 380 parts of methyl allyl polyoxyethylene ether, 175 parts of acrylamide, 1.4 parts of alkyl polyoxyethylene methacrylate, 12 parts of N,N-methylenebisacrylamide, 34 parts of acrylic acid, 10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2 parts of ammonium persulfate, 2 parts of ascorbic acid, and 4200 parts of deionized water.

[0065] 301) Add methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 60°C until completely dissolved to obtain the bottom liquid;

[0066] 302) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve 2-acrylamide-2-methylpropanesulfonic acid and ascorbic acid in deionized water to obtain component B;

[0067] 303) Components A and B were added dropwise to the bottom liquid. The addition was completed in 1.5 hours. After stirring for 1 hour, a light blue liquid water-retaining agent for manufactured sand concrete (sample 3) was obtained.

[0068] The molecular formula of the alkyl polyoxyethylene methacrylate in this embodiment is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 20 and m = 20.

[0069] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 10:1:1.

[0070] Example 4

[0071] Preparation of water-retaining agent for manufactured sand concrete (sample 4)

[0072] The product comprises, by weight, 500 parts of methyl allyl polyoxyethylene ether, 200 parts of acrylamide, 2.5 parts of alkyl polyoxyethylene methacrylate, 15 parts of N,N-methylenebisacrylamide, 45 parts of acrylic acid, 20 parts of sodium methacrylate sulfonate, 2 parts of ammonium persulfate, 0.5 parts of ascorbic acid, and 5600 parts of deionized water.

[0073] 401) Add methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 20°C until completely dissolved to obtain the bottom liquid;

[0074] 402) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve sodium methacrylate sulfonate and ascorbic acid in deionized water to obtain component B;

[0075] 403) Components A and B were added dropwise to the bottom liquid. The addition was completed in 2 hours. After stirring for 1 hour, a light blue liquid water-retaining agent for manufactured sand concrete (sample 4) was obtained.

[0076] The molecular formula of the alkyl polyoxyethylene methacrylate in this embodiment is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 20 and m = 22.

[0077] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 10:1:1.

[0078] Compare with Example 1

[0079] Preparation of Control Example 1 (Sample 5)

[0080] By weight, it includes 300 parts of methyl allyl polyoxyethylene ether, 100 parts of acrylamide, 15 parts of N,N-methylenebisacrylamide, 18 parts of acrylic acid, 25 parts of sodium propylene sulfonate, 8 parts of potassium persulfate, 8 parts of sodium bisulfite, and 3000 parts of deionized water.

[0081] 501) Add methyl allyl polyoxyethylene ether, propylene, amide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 50°C until completely dissolved to obtain the bottom liquid;

[0082] 502) Dissolve acrylic acid in deionized water to obtain component A, and dissolve sodium propylene sulfonate and sodium bisulfite in deionized water to obtain component B.

[0083] 503) Add components A and B dropwise to the bottom liquid. The addition is completed in 2 hours. After stirring for 1 hour, a colorless and transparent control sample 1 (sample 5) is obtained.

[0084] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 8:1:1.

[0085] Compare with Example 2

[0086] Preparation of Control Example 2 (Sample 6)

[0087] By weight, it includes 300 parts of methyl allyl polyoxyethylene ether, 100 parts of acrylamide, 4 parts of alkyl polyoxyethylene methacrylate, 15 parts of N,N-methylenebisacrylamide, 18 parts of acrylic acid, 25 parts of sodium propylene sulfonate, 8 parts of potassium persulfate, 8 parts of sodium bisulfite, and 3000 parts of deionized water.

[0088] 601) Add methyl allyl polyoxyethylene ether, propylene, amide, N,N-methylenebisacrylamide, potassium persulfate and deionized water into a four-necked flask, mix, and stir at 50°C until completely dissolved to obtain the bottom liquid;

[0089] 602) Dissolve alkyl polyoxyethylene methacrylate and acrylic acid in deionized water to obtain component A, and dissolve sodium propylene sulfonate and sodium bisulfite in deionized water to obtain component B.

[0090] 603) Add components A and B dropwise to the bottom liquid. The addition is completed in 2 hours. After stirring for 1 hour, a milky white control sample 2 (sample 6) is obtained.

[0091] The molecular formula of the alkyl polyoxyethylene methacrylate in this embodiment is H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 30 and m = 18.

[0092] The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is 8:1:1.

[0093] Control group, test sample 1, test sample 2, test sample 3, test sample 4, test sample 5, test sample 6, and test sample 7 were prepared to study the water retention performance, workability, compatibility with polycarboxylate superplasticizer, and mechanical strength of the above test samples.

[0094] The control group consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%.

[0095] Test sample 1 is composed of cement: fly ash: sand: stone, with a mass ratio of 250:80:960:950. The sand used is manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 1 with a mass concentration of 10% is added. The mass ratio of sample 1 to gel material (total mass of cement and fly ash) is 0.0001:1.

[0096] Test sample 2 consists of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used is manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 2 with a mass concentration of 10% is added. The mass ratio of sample 2 to gel material (total mass of cement and fly ash) is 0.0001:1.

[0097] Test sample 3 consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 3 was added at a mass concentration of 10%. The mass ratio of sample 3 to gel material (total mass of cement and fly ash) was 0.0004:1.

[0098] Test sample 4 consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 4 was also added at a mass concentration of 10%. The mass ratio of sample 4 to the gel material (total mass of cement and fly ash) was 0.0004:1.

[0099] Test sample 5 consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 5 was also added at a mass concentration of 10%. The mass ratio of sample 5 to gelling material (total mass of cement and fly ash) was 0.0001:1.

[0100] Test sample 6 consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. Sample 6 was also added at a mass concentration of 10%. The mass ratio of sample 6 to the gelling material (total mass of cement and fly ash) was 0.0001:1.

[0101] Test sample 7 consisted of cement, fly ash, sand, and stone in a mass ratio of 250:80:960:950. The sand used was manufactured sand with a fineness modulus of 3.2 and a stone powder content of 4%. A compound water-retaining agent with a mass concentration of 10% was added. The compound water-retaining agent was a mixture of sample 1 and polycarboxylate superplasticizer, with a mass ratio of sample 1 to polycarboxylate superplasticizer of 0.02:1. The mass ratio of the compound water-retaining agent to the gelling material (total mass of cement and fly ash) was 0.02:1.

[0102] The test results are shown in Table 1. The test method was carried out in accordance with the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T50080-2016), and the water retention performance of the obtained concrete water-retaining agent was judged by the bleeding rate.

[0103] Table 1. Effects of Concrete Water Retaining Agent Implementation

[0104]

[0105] As shown in Table 1, the concrete in the control group had a spread of 530 mm, a bleeding rate of 10% after 1 hour, and exhibited segregation and bleeding after leaving the mixer, resulting in poor workability.

[0106] When samples 1, 2, 3, and 4, and test samples 1, 2, 3, 4, and 7 containing the compounded water-retaining agent were added, no segregation was observed in the concrete mixtures. The concrete paste was rich, with good cohesion, and the spread was greater than 500 mm. The 1-hour bleeding rate was less than 6%, and the 28-day strength was not significantly lower than the control group. These results indicate that the workability and water retention of concrete are significantly improved by incorporating the water-retaining agent obtained in this invention. Furthermore, the compressive strength test results show that the incorporation of the water-retaining agent of this invention has no significant effect on the strength of the concrete.

[0107] When test samples 5 and 6 (comparison samples 5 and 6) were added, the concrete exhibited segregation and bleeding, with no significant improvement in cohesiveness and workability, and a marked decrease in spread. Test sample 6, in particular, had excessively high air content, which negatively impacted the concrete strength. These results indicate that the content of alkyl polyoxyethylene methacrylate is a crucial factor affecting the effectiveness of this water-retaining agent.

[0108] Furthermore, manufactured sand concrete water-retaining agents can be compounded with polycarboxylate superplasticizers, which can significantly improve the cohesiveness of the paste, give the concrete good workability, reduce the concrete bleeding rate, and not affect the mechanical properties of the concrete.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-retaining agent for manufactured sand concrete, characterized in that: The product, by weight, comprises 300-500 parts of methyl allyl polyoxyethylene ether, 100-200 parts of acrylamide, 1-2.5 parts of alkyl polyoxyethylene methacrylate, 10-15 parts of N,N-methylenebisacrylamide, 18-45 parts of acrylic acid, 10-25 parts of salt-resistant monomer, 2-8 parts of initiator, 0.5-8 parts of reducing agent, and 3000-5600 parts of deionized water; the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is (2-3):

1. The specific preparation steps are as follows: Methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide, initiator, and deionized water are mixed and stirred at a certain temperature to dissolve, thus obtaining the base solution. Alkyl polyoxyethylene methacrylate and acrylic acid are dissolved in deionized water to obtain component A, and salt-resistant monomer and reducing agent are dissolved in deionized water to obtain component B. Components A and B are added dropwise to the bottom liquid. After the addition is complete, the mixture is stirred for a certain period of time to obtain a water-retaining agent for manufactured sand concrete.

2. The water-retaining agent for manufactured sand concrete according to claim 1, characterized in that: The alkyl polyoxyethylene methacrylate has the molecular formula H2C=C(CH3)CO2(CH2CH2O). n (CH2) m CH3, where n = 20-30, m = 18-22.

3. The water-retaining agent for manufactured sand concrete according to claim 1, characterized in that: The salt-resistant monomer is one or two of sodium propylene sulfonate, sodium methpropylene sulfonate, sodium styrene sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid.

4. The water-retaining agent for manufactured sand concrete according to claim 1, characterized in that: The initiator is one of potassium persulfate, ammonium persulfate, or sodium persulfate, and the reducing agent is one of sodium bisulfite or ascorbic acid.

5. The water-retaining agent for manufactured sand concrete according to claim 1, characterized in that: In the preparation step, methyl allyl polyoxyethylene ether, acrylamide, N,N-methylenebisacrylamide and initiator are mixed and stirred at 20-60℃, and the addition time is 1-2 hours.

6. The water-retaining agent for manufactured sand concrete according to claim 1, characterized in that: The mass ratio of deionized water in the base solution, deionized water in component A, and deionized water in component B is (8-10):1:

1.

7. A method of using a water-retaining agent for manufactured sand concrete as described in any one of claims 1-6, characterized in that: The water-retaining agent for manufactured sand concrete is added to the concrete, or the water-retaining agent for manufactured sand concrete is compounded with polycarboxylate superplasticizer and then added to the concrete.

8. The method of use according to claim 7, characterized in that: When using a combination of manufactured sand concrete water-retaining agent and polycarboxylate superplasticizer, the mass ratio of manufactured sand concrete water-retaining agent to polycarboxylate superplasticizer is (0.01-0.02):1; Alternatively, the water-retaining agent for manufactured sand concrete can be directly added to the cementitious material, with a mass ratio of (0.0001-0.0004):1 between the water-retaining agent and the cementitious material.

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