Viscosity reduction type polycarboxylic acid water reducer suitable for high-strength concrete and preparation method of viscosity reduction type polycarboxylic acid water reducer

Abstract

The invention relates to the technical field of concrete admixtures in building materials, in particular to a viscosity reduction type polycarboxylic acid water reducer suitable for high-strength concrete and a preparation method of the viscosity reduction type polycarboxylic acid water reducer. The hydrophobic modified unsaturated double-chain polyether macromonomer is prepared from the following components in parts by mass: 20 to 30 parts of unsaturated acid, 200 to 300 parts of hydrophobic modified unsaturated double-chain polyether macromonomer, 10 to 15 parts of phosphate monomer, 2 to 4 parts of oxidizing agent, 1 to 2 parts of reducing agent, 1 to 2 parts of chain transfer agent, 5 to 10 parts of neutralizing agent and 120 to 180 parts of water. According to the invention, the polyether chain can unfold in a pore solution, the steric hindrance effect is further enhanced, cement particles are ensured to be effectively dispersed in a compact space, and meanwhile, the hydrophobic part of the side chain can effectively reduce the surface tension of the pore solution, so that the condition of overhigh viscosity is avoided, and the flowability and constructability of the concrete are improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures in building materials, in particular to a viscosity-reducing polycarboxylic acid-based water reducer suitable for high-strength concrete and a preparation method thereof. Background Art

[0002] The widespread use of high-strength concrete in construction projects, particularly in high-rise buildings, large-scale infrastructure, and bridges, has placed higher demands on concrete's strength and workability. High-strength concrete typically has a low water-cement ratio to ensure sufficient strength. However, while a low water-cement ratio improves concrete's strength, it also leads to poor workability. In particular, the increased viscosity of the concrete can lead to insufficient fluidity, which in turn affects the concrete's construction and placement processes.

[0003] In order to improve the working performance of high-strength concrete, water reducers are widely used in concrete production as an important admixture, especially under conditions of low water-cement ratio. However, traditional water reducers often cannot fully meet the requirements of high-strength concrete, especially in terms of maintaining good fluidity and workability while avoiding increasing viscosity. Existing polycarboxylate-based water reducers have become an important choice for improving concrete performance due to their excellent water-reducing properties and strong cement dispersibility. However, in some cases, traditional polycarboxylate-based water reducers, especially in concrete with high cement content or extremely low water-cement ratio, often face the problem of high viscosity, which affects the workability of concrete.

[0004] While traditional polycarboxylate-based water-reducing agents have made significant progress in water-reducing performance, they still face limitations when addressing the viscosity of high-strength concrete at low water-cement ratios. Therefore, developing a viscosity-reducing polycarboxylate-based water-reducing agent that maintains excellent water-reducing performance at low water-cement ratios while effectively reducing the viscosity of high-strength concrete and improving its workability is a key research direction in concrete admixture technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, so as to solve the problem that the viscosity of the existing high-strength concrete is too high and is not conducive to construction.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, comprising the following components by weight:

[0008]

[0009]

[0010] Furthermore, the unsaturated acid is acrylic acid or methacrylic acid.

[0011] Furthermore, the preparation steps of the hydrophobically modified unsaturated double-chain polyether macromonomer include:

[0012] 1) mixing isobutanol and sodium hydride at a molar ratio of 1:1.1 to react and generate a sodium alcoholate active intermediate;

[0013] 2) adding the intermediate obtained in step 1) to an autoclave, evacuating the autoclave and heating the autoclave to 120-130° C., then introducing ethylene oxide (EO) while controlling the temperature at 120-130° C. and the pressure at ≤0.4 MPa until the number of ethylene oxide additions reaches 5-10;

[0014] 3) Continue to introduce propylene oxide (PO), controlling the temperature at 120-130° C. and the pressure at ≤0.4 MPa, until the number of propylene oxide additions reaches 5-10;

[0015] 4) aging until the pressure drops below 0.1 MPa, and discharging to obtain a polyether segment containing a hydrophobic segment;

[0016] 5) adding the polyether segment, polymerization inhibitor, and catalyst into the reactor and mixing them uniformly, then adding maleic acid into the reactor at a molar ratio of maleic acid:polyether segment = 1:2 and mixing them uniformly;

[0017] 6) Control the reaction temperature to 80°C-120°C and the reaction time to 6-10h;

[0018] 7) After the reaction ends, the temperature is lowered to below 60° C. to prepare a hydrophobically modified unsaturated double-chain polyether macromonomer.

[0019] Furthermore, the molecular weight of the hydrophobically modified unsaturated double-chain polyether macromonomer ethylene glycol monoalkyl ether is 1300-1900.

[0020] Furthermore, the phosphate monomer is blocked amide phosphate, triisopropyl phosphite or 2-hydroxyethyl methacrylate phosphate.

[0021] Furthermore, the oxidant is hydrogen peroxide or ammonium persulfate.

[0022] Furthermore, the reducing agent is one or more of ferrous sulfate, L-ascorbic acid and sodium formaldehyde sulfoxylate.

[0023] Furthermore, the chain transfer agent is one or more of thioglycolic acid, mercaptopropionic acid and mercaptoethanol.

[0024] Furthermore, the neutralizing agent is sodium hydroxide solution or potassium hydroxide solution.

[0025] A method for preparing a viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete comprises the following steps:

[0026] Dissolving the hydrophobically modified unsaturated double-chain polyether macromonomer in deionized water to prepare a base material;

[0027] Dissolve the unsaturated acid and functional monomer in deionized water to prepare the drop material A. Mix the chain transfer agent, reducing agent and deionized water to prepare the drop material B. Add the oxidant to the base material 5 minutes before the dropwise addition. Then, add the A and B materials to the base material at room temperature for 2-3 hours. After the dropwise addition is completed, keep warm for 1 hour. Then add the neutralizer to adjust the pH to neutral.

[0028] The beneficial effects of adopting the technical solution of the present invention are:

[0029] 1) Traditional polycarboxylate-based water reducers rely primarily on the adsorption of carboxylic acid groups onto cement particles, but their adsorption capacity is often insufficient at low water-cement ratios, resulting in poor dispersion between cement particles and high viscosity, which affects the fluidity of concrete. The present invention introduces a phosphate monomer, in which the phosphate group has a stronger adsorption capacity. This allows for stronger adsorption on the surface of cement particles, effectively dispersing the cement particles, significantly reducing the viscosity of high-strength concrete and improving its performance.

[0030] 2) The hydrophobically modified unsaturated double-chain polyether macromonomer used in the present invention has two polyether chains, which can provide strong steric hindrance to prevent aggregation between cement particles. Under low water-cement ratio conditions, the distance between cement particles is small, and traditional water reducers have difficulty in exerting a good dispersing effect. However, the polyether chains of the present invention can stretch out in the pore solution, further enhancing the steric hindrance effect and ensuring that the cement particles are effectively dispersed in a tight space. At the same time, the hydrophobic part of its side chain can effectively reduce the surface tension of the pore solution, thereby avoiding excessive viscosity and improving the fluidity and workability of the concrete.

[0031] 3) Conventional polycarboxylate water reducers can easily lead to excessively high viscosity at low water-cement ratios, affecting the workability of concrete. The viscosity-reducing polycarboxylate water reducer of the present invention optimizes its molecular structure, enabling it to not only maintain a good water-reducing effect in high-strength concrete but also significantly reduce the viscosity of the concrete, ensuring good fluidity and workability during pouring, thus resolving the difficulty in concrete construction at low water-cement ratios. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the invention in conjunction with the specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] A viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, comprising the following components by weight:

[0034]

[0035] Wherein, the unsaturated acid is acrylic acid or methacrylic acid.

[0036] The phosphate group in the phosphate ester monomer has stronger adsorption capacity and can form stronger adsorption force on the surface of cement particles, thereby effectively dispersing cement particles, significantly reducing the viscosity of high-strength concrete, and improving its working performance.

[0037] The hydrophobically modified unsaturated double-chain polyether macromonomer has two polyether chains, which provide strong steric hindrance and prevent aggregation of cement particles. At low water-cement ratios, cement particles are closely spaced, making it difficult for traditional water reducers to effectively disperse them. However, the polyether chains of this invention can expand in the pore solution, further enhancing the steric hindrance effect and ensuring effective dispersion of cement particles in a tight space. Furthermore, the hydrophobic side chains effectively reduce the surface tension of the pore solution, thereby preventing excessive viscosity and improving the fluidity and workability of the concrete.

[0038] The preparation method of the above hydrophobically modified unsaturated double-chain polyether macromonomer comprises the following steps:

[0039] 1) mixing isobutanol and sodium hydride at a molar ratio of 1:1.1 to react and generate a sodium alcoholate active intermediate;

[0040] 2) adding the intermediate obtained in step 1) to an autoclave, evacuating the autoclave and heating the autoclave to 120° C., then introducing ethylene oxide (EO) while maintaining the temperature at 120° C. and the pressure at 0.4 MPa until the number of ethylene oxide additions reaches 5-10;

[0041] 3) Continue to introduce propylene oxide (PO), controlling the temperature at 120-130° C. and the pressure at ≤0.4 MPa, until the number of propylene oxide additions reaches 5-10;

[0042] 4) aging until the pressure drops below 0.1 MPa, and discharging to obtain a polyether segment containing a hydrophobic segment;

[0043] 5) adding the polyether segment, polymerization inhibitor, and catalyst into the reactor and mixing them uniformly, then adding maleic acid into the reactor at a molar ratio of maleic acid:polyether segment = 1:2 and mixing them uniformly;

[0044] 6) Control the reaction temperature to 90°C and the reaction time to 8h;

[0045] 7) After the reaction ends, the temperature is lowered to below 60° C. to prepare a hydrophobically modified unsaturated double-chain polyether macromonomer.

[0046] A method for preparing a viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete comprises the following steps:

[0047] Dissolving the hydrophobically modified unsaturated double-chain polyether macromonomer in deionized water to prepare a base material;

[0048] Dissolve the unsaturated acid and functional monomer in deionized water to prepare the drop material A. Mix the chain transfer agent, reducing agent and deionized water to prepare the drop material B. Add the oxidant to the base material 5 minutes before the dropwise addition. Then, add the A and B materials to the base material at room temperature for 2-3 hours. After the dropwise addition is completed, keep warm for 1 hour. Then add the neutralizer to adjust the pH to neutral.

[0049] The following examples further illustrate the above embodiments, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples, where specific conditions are not specified, were performed according to conventional methods and conditions, or according to the product specifications. Reagents, raw materials, and equipment not otherwise specified were all commercially available.

[0050] Example 1:

[0051] A viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, comprising the following components:

[0052]

[0053] The molecular weight of the hydrophobically modified unsaturated double-chain polyether macromonomer is 1300.

[0054] The preparation method of the viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete in this embodiment includes the following steps:

[0055] Dissolve 200g of unsaturated double-chain polyether macromonomer in 100g of deionized water to prepare a base material;

[0056] 20g of acrylic acid and 10g of blocked amide phosphate were dissolved in 20g of deionized water to prepare drop material A, 1g of chain transfer agent, 1g of reducing agent were mixed with 20g of deionized water to prepare drop material B, 2g of oxidant was added to the base material 5min before dropwise addition, and then materials A and B were added dropwise to the base material at room temperature for 2-3h. After the dropwise addition was completed, the mixture was kept warm for 1h, and then a neutralizer was added to adjust the pH to neutral to obtain a viscosity-reducing water-reducing agent.

[0057] The viscosity-reducing polycarboxylic acid water-reducing agent was added to a cement paste with a water-cement ratio of 0.20. The fluidity of the water-reducing polycarboxylic acid water-reducing agent after being added to the cement paste was measured with reference to GB / T8077-2012 Test method for homogeneity of concrete admixtures. At the same time, the plastic viscosity of the cement paste was measured using a TMR-IR rheometer produced by Shanghai Tongrui Instrument Equipment Co., Ltd.

[0058] Example 2:

[0059] A viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, comprising the following components:

[0060]

[0061] The molecular weight of the hydrophobically modified unsaturated double-chain polyether macromonomer is 1600.

[0062] The viscosity-reducing polycarboxylic acid water-reducing agent suitable for high-strength concrete in this embodiment is prepared by the following steps:

[0063] 240g of unsaturated double-chain polyether macromonomer was dissolved in 100g of deionized water to prepare a base material; 15g of acrylic acid and 15g of triisopropyl phosphite were dissolved in 20g of deionized water and mixed to prepare dropwise addition material A; 1g of chain transfer agent and 1g of reducing agent were mixed with 20g of deionized water to prepare dropwise addition material B; 2g of oxidant was added to the base material 5min before dropwise addition; then materials A and B were dropwise added to the base material at room temperature for 2-3h; after the dropwise addition was completed, the material was kept warm for 1h; then a neutralizer was added to adjust the pH to neutral to obtain a viscosity-reducing water-reducing agent.

[0064] The viscosity-reducing polycarboxylic acid water-reducing agent was added to a cement paste with a water-cement ratio of 0.20. The fluidity of the water-reducing polycarboxylic acid water-reducing agent after being added to the cement paste was measured with reference to GB / T8077-2012 Test method for homogeneity of concrete admixtures. At the same time, the plastic viscosity of the cement paste was measured using a TMR-IR rheometer produced by Shanghai Tongrui Instrument Equipment Co., Ltd.

[0065] Example 3:

[0066] A viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete, comprising the following components:

[0067]

[0068] The molecular weight of the hydrophobically modified unsaturated double-chain polyether macromonomer is 1900.

[0069] The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete in this embodiment has a preparation method comprising: dissolving 240 g of an unsaturated double-chain polyether macromonomer in 100 g of deionized water to prepare a base material; dissolving 15 g of acrylic acid and 25 g of 2-hydroxyethyl methacrylate phosphate in 20 g of deionized water and mixing the mixture to prepare a drop material A; mixing 1 g of a chain transfer agent and 1 g of a reducing agent with 20 g of deionized water to prepare a drop material B; adding 2 g of an oxidant to the base material 5 minutes before dropwise addition; then dropwise adding materials A and B to the base material at room temperature for 2-3 hours; keeping the temperature for 1 hour after the dropwise addition is completed; and finally adding a neutralizer to adjust the pH to neutral to obtain the viscosity-reducing water-reducing agent.

[0070] The viscosity-reducing polycarboxylic acid water-reducing agent was added to a cement paste with a water-cement ratio of 0.20. The fluidity of the water-reducing polycarboxylic acid water-reducing agent after being added to the cement paste was measured with reference to GB / T8077-2012 Test method for homogeneity of concrete admixtures. At the same time, the plastic viscosity of the cement paste was measured using a TMR-IR rheometer produced by Shanghai Tongrui Instrument Equipment Co., Ltd.

[0071] Comparative Example 1:

[0072] A common commercially available polycarboxylic acid-based water reducer with a water reduction rate of 30%.

[0073] The conventional polycarboxylic acid-based water reducer was added to a cement paste with a water-cement ratio of 0.20. The fluidity of the water reducer after addition to the cement paste was measured with reference to GB / T8077-2012 Test method for homogeneity of concrete admixtures. The plastic viscosity of the cement paste was measured using a TMR-IR rheometer produced by Shanghai Tongrui Instruments Co., Ltd.

[0074] The following table shows the test results:

[0075] Sample Flowability (mm) Plastic viscosity (Pa*s) Example 1 220 1.244 Example 2 245 1.186 Example 3 225 1.232 Comparative Example 1 210 1.411

[0076] The results show that the viscosity-reducing polycarboxylic acid water-reducing agent suitable for high-strength concrete significantly improves the flow properties of cement paste with a low water-cement ratio, and the polycarboxylic acid water-reducing agent synthesized in Example 2 has the best dispersion effect. At the same time, the plastic viscosity of the cement paste in the example is significantly lower than that in the comparative example added with a conventional water-reducing agent, indicating that the unsaturated double-chain polyether macromonomer used in the example effectively exerts a steric hindrance effect, thereby optimizing the working performance of the cement paste.

[0077] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent claim scheme. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A viscosity-reducing polycarboxylate water-reducing agent suitable for high-strength concrete, characterized by: Its mass composition is as follows: 20-30 parts of unsaturated acid, 200~300 parts of hydrophobically modified unsaturated double-chain polyether macromonomer, 10-15 parts of phosphate monomer, 2-4 parts of oxidant, 1-2 parts of reducing agent, 1-2 parts of chain transfer agent, 5-10 parts of neutralizer, 120-180 parts of water.

2. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The unsaturated acid is acrylic acid or methacrylic acid.

3. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The preparation steps of the hydrophobically modified unsaturated double-chain polyether macromonomer include: 1) Mix isobutanol and sodium hydride at a molar ratio of 1:1.1 to react and generate a sodium alcoholate active intermediate; 2) The intermediate obtained in step 1) is added to a high-pressure reactor, evacuated, and heated to 120-130°C. Ethylene oxide is then introduced while maintaining the temperature at 120-130°C and the pressure at ≤0.4 MPa until the number of ethylene oxide additions reaches 5-10. 3) Continue to introduce propylene oxide, controlling the temperature at 120-130°C and the pressure at ≤0.4 MPa, until the number of propylene oxide additions reaches 5-10; 4) Aging until the pressure drops below 0.1 MPa, and discharging to obtain a polyether segment containing a hydrophobic segment; 5) Add the polyether segment, polymerization inhibitor, and catalyst to the reactor and mix them evenly. Then, add maleic acid to the reactor at a molar ratio of maleic acid:polyether segment = 1:2 and mix evenly. 6) Control the reaction temperature to 80-120°C and the reaction time to 6-10 h; 7) After the reaction ends, the temperature is lowered to below 60°C to prepare the hydrophobically modified unsaturated double-chain polyether macromonomer.

4. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The molecular weight of the hydrophobically modified unsaturated double-chain polyether macromonomer ethylene glycol monoalkyl ether is 1300-1900.

5. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The phosphate monomer is end-capped amide phosphate, triisopropyl phosphite or 2-hydroxyethyl methacrylate phosphate.

6. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The oxidant is hydrogen peroxide or ammonium persulfate.

7. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The reducing agent is one or more of ferrous sulfate, L-ascorbic acid and sodium formaldehyde sulfoxylate.

8. The viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The chain transfer agent is one or more of mercaptoacetic acid, mercaptopropionic acid and mercaptoethanol.

9. The viscosity-reducing polycarboxylate water-reducing agent suitable for high-strength concrete according to claim 1, characterized in that: The neutralizing agent is sodium hydroxide solution or potassium hydroxide solution.

10. The method for preparing a viscosity-reducing polycarboxylic acid-based water-reducing agent suitable for high-strength concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: Dissolving the hydrophobically modified unsaturated double-chain polyether macromonomer in deionized water to prepare a base material; Dissolve the unsaturated acid and functional monomer in deionized water to prepare the drop material A. Mix the chain transfer agent, reducing agent and deionized water to prepare the drop material B. Add the oxidant to the base material 5 minutes before the dropwise addition. Then, add the A and B materials to the base material at room temperature for 2-3 hours. After the dropwise addition is completed, keep warm for 1 hour. Finally, add the neutralizer to adjust the pH to neutral.

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