A self-compacting concrete and a method for producing the same

Abstract

This invention relates to a self-compacting concrete and its preparation method, belonging to the field of concrete technology. The raw materials for the self-compacting concrete provided by this invention include cement, fly ash, slag powder, sand, crushed stone, a high-performance water-reducing agent, an air-entraining agent, and water. The high-performance water-reducing agent is obtained by blending a polycarboxylate water-reducing agent, an organosilicon-modified hyperbranched star polymer, and a polyether-modified organosilicon polymer. The air-entraining agent is obtained by compounding sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate. The self-compacting concrete prepared by this invention has a high water reduction rate, low slump loss, and high stability, resulting in a significant improvement in overall performance.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology and relates to a self-compacting concrete and its preparation method. Background Technology

[0002] The core characteristic of self-compacting concrete is that it can fully fill complex formwork spaces and tightly wrap reinforcing bars under its own weight without mechanical vibration. To achieve this high fluidity, the internal friction of the mixture must be reduced. Adding an appropriate amount of water-reducing agent can effectively disperse cement particles and release the trapped water, significantly improving the fluidity of concrete without increasing water consumption, maintaining a low water-cement ratio, and ensuring the strength and structural density of the hardened concrete, thereby significantly improving construction efficiency. Common water-reducing agents include ordinary water-reducing agents based on lignin sulfonates, high-efficiency water-reducing agents based on naphthalene and melamine, and high-performance water-reducing agents based on polycarboxylate. However, different water-reducing agents still have some limitations in use. For example, ordinary water-reducing agents have few hydrophilic groups and cannot effectively reduce the surface tension of water, easily causing air bubbles; high-efficiency water-reducing agents often have poor compatibility with cement or admixtures, resulting in rapid slump loss over time; high-performance water-reducing agents tend to have excessive viscosity, increasing construction difficulty and leading to weakened concrete performance. Summary of the Invention

[0003] The purpose of this invention is to provide a self-compacting concrete and its preparation method, which improves the overall performance of the self-compacting concrete by introducing high-performance water-reducing agents and air-entraining agents in a synergistic manner.

[0004] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a self-compacting concrete, the self-compacting concrete comprising the following raw materials in parts by weight: 350-450 parts cement, 80-150 parts fly ash, 50-100 parts slag powder, 700-850 parts sand, 800-950 parts crushed stone, 8-15 parts high-performance water-reducing agent, 0.01-0.05 parts air-entraining agent, and 130-150 parts water, wherein the high-performance water-reducing agent is obtained by blending polycarboxylate water-reducing agent, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer, and the air-entraining agent is obtained by compounding sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate.

[0005] Preferably, the high-performance water-reducing agent comprises the following raw materials in parts by weight: 300-600 parts unsaturated polyether macromonomer, 30-50 parts unsaturated carboxylic acid, 1-1.4 parts organosilicon-modified hyperbranched star polymer, 0.1-0.7 parts polyether-modified organosilicon polymer, 2.5-3.5 parts oxidant, 0.8-1.2 parts reducing agent, 1-3 parts chain transfer agent, 10-20 parts neutralizing agent, and 450-550 parts water.

[0006] Preferably, the unsaturated polyether macromonomer is selected from allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, or isopentenyl polyoxyethylene ether.

[0007] Preferably, the unsaturated carboxylic acid is selected from acrylic acid or methacrylic acid.

[0008] Preferably, the organosilicon-modified hyperbranched star polymer is BASF FoamStar ST A38.

[0009] Preferably, the polyether-modified organosilicon polymer is BASF FoamStar SI 2210.

[0010] Preferably, the mass ratio of sodium dodecylbenzenesulfonate to sodium fatty alcohol polyoxyethylene sulfonate is 1.2-2:1.

[0011] In a second aspect, the present invention provides a method for preparing the high-performance water-reducing agent described in the first aspect, comprising the following steps: S11. Mix the unsaturated polyether macromonomer, oxidant, and water evenly to obtain the first solution; S12. Mix unsaturated carboxylic acid and water thoroughly to obtain a second solution; S13. Mix the reducing agent, chain transfer agent and water evenly to obtain the third solution; S14. Under stirring at 45℃ and 120-180 rpm, the second and third solutions are simultaneously added dropwise to the first solution. After the addition is complete, keep warm for 3 hours, then add the neutralizing agent and mix evenly to obtain the polycarboxylate superplasticizer. S15. Mix the polycarboxylate superplasticizer, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer evenly to obtain a high-performance superplasticizer.

[0012] Preferably, the mass ratio of water in steps S11, S12, and S13 is 5-7:2-3:1; the dropping rate of the second solution in step S14 is 1.5-2.5 mL / min, and the dropping rate of the third solution is 0.4-0.8 mL / min; the stirring speed in step S15 is 200-300 rpm.

[0013] Thirdly, the present invention provides a method for preparing the self-compacting concrete described in the first aspect, comprising the following steps: S21. At a stirring speed of 50-80 rpm, fly ash, sand, and crushed stone are mixed evenly. Cement is added and mixed evenly. Slag powder is added and mixed evenly. Finally, high-performance water-reducing agent, air-entraining agent, and water are added and mixed evenly to obtain the self-compacting concrete.

[0014] The beneficial effects of this invention are: (1) This invention provides a self-compacting concrete, wherein the high-performance water-reducing agent is obtained by blending polycarboxylate water-reducing agent, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer; wherein the organosilicon-modified hyperbranched star polymer (BASF FoamStar ST A38) has a unique star-shaped branched structure and organosilicon functional groups, and its star-shaped multi-arm skeleton produces a "multi-tooth adsorption" effect on the surface of cement particles, and the synergistic effect of multiple adsorption sites makes the water-reducing agent molecules more firmly anchored; the polyether-modified organosilicon polymer (BASF FoamStar SI 2210) has good molecular chain flexibility and small steric hindrance, and can quickly migrate to the surface of the bubble liquid film, reduce the surface tension, and thus inhibit foam generation, and is compatible with the organosilicon-modified hyperbranched star polymer (BASF FoamStar ST A38). A38) forms a dual defoaming system that combines rigidity and flexibility, avoiding the steric hindrance effect that may be caused by the introduction of star-shaped structure, and ensuring the migration and dispersion of defoaming components in the concrete system; the three are used together to effectively improve water reduction, reduce slump loss over time, and take into account both high fluidity and plasticity retention.

[0015] (2) In this invention, an air-entraining agent composed of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate is added to self-compacting concrete. Sodium dodecylbenzene sulfonate, as an anionic surfactant, imparts a certain rigidity to the bubbles with its benzene ring structure, making the bubbles less prone to breakage during concrete mixing and transportation. The polyoxyethylene segments in sodium fatty alcohol polyoxyethylene sulfonate impart good flexibility and stability to the bubbles, enabling them to be evenly dispersed in the concrete system. The two work synergistically to introduce a large number of uniform and stable microbubbles during concrete mixing, thereby improving the fluidity and filling properties of self-compacting concrete. In addition, the air-entraining agent forms a "defoaming-air-entraining synergistic regulation system" with organosilicon-modified hyperbranched star polymer and polyether-modified organosilicon polymer. The organosilicon-modified hyperbranched star polymer and polyether-modified organosilicon polymer eliminate the uneven large bubbles introduced by polycarboxylate superplasticizer at high speed and efficiency, preventing harmful large bubbles from causing concrete strength loss. The air-entraining agent introduces beneficial microbubbles, improving fluidity and durability. The two work synergistically to improve the overall performance of self-compacting concrete. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0017] Unless otherwise specified, all other materials, reagents, etc. used in all embodiments and comparative examples of this invention are commercially available.

[0018] The method for preparing self-compacting concrete described in all embodiments of the present invention includes the following steps: S21. At a stirring speed of 65 rpm, fly ash, sand, and crushed stone are mixed evenly, cement is added and mixed evenly, slag powder is added and mixed evenly, and finally high-performance water-reducing agent, air-entraining agent, and water are added and mixed evenly to obtain the self-compacting concrete. The preparation of the high-performance water-reducing agent includes the following steps: S11. Mix the unsaturated polyether macromonomer, oxidant (i.e., ammonium persulfate), and water evenly to obtain the first solution; S12. Mix unsaturated carboxylic acid and water thoroughly to obtain a second solution; S13. Mix the reducing agent (i.e., ascorbic acid), chain transfer agent (i.e., mercaptopropionic acid), and water evenly to obtain the third solution; S14. Under stirring at 45℃ and 150rpm, the second and third solutions are simultaneously added dropwise to the first solution. After the addition is complete, keep the temperature for 3 hours, then add the neutralizing agent (i.e., 30wt% sodium hydroxide solution), mix well, and obtain the polycarboxylate superplasticizer. S15. Mix the polycarboxylate superplasticizer, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer evenly to obtain a high-performance superplasticizer. In step S11, step S12, and step S13, the mass ratio of water is 6:2.5:1; in step S14, the dropping rate of the second solution is 2 mL / min, and the dropping rate of the third solution is 0.6 mL / min; in step S15, the stirring speed is 250 rpm.

[0019] Example 1 The self-compacting concrete comprises the following raw materials in parts by weight: 400 parts cement, 115 parts fly ash, 75 parts slag powder, 775 parts sand, 875 parts crushed stone, 11.5 parts high-performance water-reducing agent, 0.03 parts air-entraining agent, and 140 parts water. The high-performance water-reducing agent comprises the following raw materials in parts by weight: 450 parts unsaturated polyether macromonomer (i.e., allyl polyoxyethylene ether), 40 parts unsaturated carboxylic acid (i.e., methacrylic acid), 1.2 parts organosilicon-modified hyperbranched star polymer (i.e., BASF FoamStar ST A38), 0.4 parts polyether-modified organosilicon polymer (i.e., BASF FoamStar SI 2210), 3 parts oxidant, 1 part reducing agent, 2 parts chain transfer agent, 15 parts neutralizing agent, and 500 parts water; The air-entraining agent is prepared by compounding sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate (product abbreviation: AESO, purchased from Wuhan Jiayehe New Material Technology Co., Ltd.) in a mass ratio of 1.6:1.

[0020] Example 2 Compared with Example 1, the only difference is that the high-performance water-reducing agent in Example 2 includes the following raw materials in parts by weight: 300 parts of unsaturated polyether macromonomer (i.e., methyl allyl polyoxyethylene ether), 30 parts of unsaturated carboxylic acid (i.e., acrylic acid), 1 part of silicone-modified hyperbranched star polymer (i.e., BASF FoamStar ST A38), 0.1 parts of polyether-modified silicone polymer (i.e., BASF FoamStar SI 2210), 2.5 parts of oxidant, 0.8 parts of reducing agent, 1 part of chain transfer agent, 10 parts of neutralizing agent, and 450 parts of water, with other conditions remaining the same as in Example 1.

[0021] Example 3 Compared with Example 1, the only difference is that the high-performance water-reducing agent in Example 3 includes the following raw materials in parts by weight: 600 parts of unsaturated polyether macromonomer (i.e., isopentenyl alcohol polyoxyethylene ether), 50 parts of unsaturated carboxylic acid (i.e., methacrylic acid), 1.4 parts of organosilicon-modified hyperbranched star polymer (i.e., BASF FoamStar ST A38), 0.7 parts of polyether-modified organosilicon polymer (i.e., BASF FoamStar SI 2210), 3.5 parts of oxidant, 1.2 parts of reducing agent, 3 parts of chain transfer agent, 20 parts of neutralizing agent, and 550 parts of water, with other conditions remaining the same as in Example 1.

[0022] Example 4 Compared with Example 1, the only difference is that the air-entraining agent in Example 4 is a compound of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate (product abbreviation: AESO, purchased from Wuhan Jiayehe New Material Technology Co., Ltd.) in a mass ratio of 1.2:1, and other conditions are the same as in Example 1.

[0023] Example 5 Compared with Example 1, the only difference is that the air-entraining agent in Example 5 is a compound of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate (product abbreviation: AESO, purchased from Wuhan Jiayehe New Material Technology Co., Ltd.) in a mass ratio of 2:1, and other conditions are the same as in Example 1.

[0024] Example 6 Compared with Example 1, the only difference is that the self-compacting concrete in Example 6 includes the following raw materials by weight: 350 parts cement, 80 parts fly ash, 50 parts slag powder, 700 parts sand, 800 parts crushed stone, 8 parts high-performance water-reducing agent, 0.01 parts air-entraining agent, and 130 parts water, while other conditions remain the same as in Example 1.

[0025] Example 7 Compared with Example 1, the only difference is that the self-compacting concrete in Example 7 includes the following raw materials by weight: 450 parts cement, 150 parts fly ash, 100 parts slag powder, 850 parts sand, 950 parts crushed stone, 15 parts high-performance water-reducing agent, 0.05 parts air-entraining agent, and 150 parts water, while other conditions remain the same as in Example 1.

[0026] Comparative Example 1 Compared with Example 1, the only difference is that the silicone-modified hyperbranched star polymer (i.e., BASF FoamStar ST A38) was omitted in Comparative Example 1, and the missing amount was made up with an equal weight of polyether-modified silicone polymer (i.e., BASF FoamStar SI2210), while other conditions remained the same as in Example 1.

[0027] Comparative Example 2 Compared with Example 1, the only difference is that the polyether-modified silicone polymer (i.e., BASF FoamStar SI 2210) was omitted in Comparative Example 2, and the missing amount was made up with an equal weight of silicone-modified hyperbranched star polymer (i.e., BASF FoamStar ST A38), while other conditions remained the same as in Example 1.

[0028] Comparative Example 3 Compared with Example 1, the only difference is that the amount of silicone-modified hyperbranched star polymer added to the high-performance water-reducing agent of Comparative Example 3 is 0.4 parts by weight and the amount of polyether-modified silicone polymer added is 1.2 parts by weight. Other conditions are the same as in Example 1.

[0029] Comparative Example 4 Compared with Example 1, the only difference is that the silicone-modified hyperbranched star polymer (BASF FoamStar ST A38) was omitted in Comparative Example 4, and the missing amount was made up with an equal weight of hyperbranched star polymer (BASF FoamStar ST A10), while other conditions remained the same as in Example 1.

[0030] Comparative Example 5 Compared with Example 1, the only difference is that the polyether-modified silicone polymer (i.e., BASF FoamStar SI 2210) was omitted in Comparative Example 5, and the missing amount was made up with an equal weight of modified silicone defoamer (product name: water-reducing defoamer, brand: Jinling New Materials). All other conditions were the same as in Example 1.

[0031] Comparative Example 6 Compared with Example 1, the only difference is that the silicone-modified hyperbranched star polymer and the polyether-modified silicone polymer were omitted in Comparative Example 6, and the missing amounts were made up with an equal weight of BJ0188 defoamer (brand name Baiju). All other conditions were the same as in Example 1.

[0032] Comparative Example 7 Compared with Example 1, the only difference is that sodium fatty alcohol polyoxyethylene sulfonate in Comparative Example 7 was omitted from the air-entraining agent, and the missing amount was made up with an equal weight of sodium dodecylbenzene sulfonate. All other conditions were the same as in Example 1.

[0033] Comparative Example 8 Compared with Example 1, the only difference is that sodium dodecylbenzene sulfonate in Comparative Example 8 was omitted from the air-entraining agent, and the missing amount was made up with an equal weight of sodium fatty alcohol polyoxyethylene sulfonate (product abbreviation: AESO, purchased from Wuhan Jiayehe New Material Technology Co., Ltd.), while other conditions remained the same as in Example 1.

[0034] Comparative Example 9 Compared with Example 1, the only difference is that the air-entraining agent in Comparative Example 9 was prepared by compounding sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate (product abbreviation: AESO, purchased from Wuhan Jiayehe New Material Technology Co., Ltd.) in a mass ratio of 1:1.6.

[0035] The self-compacting concretes prepared in Examples 1-7 and Comparative Examples 1-9 were used as samples, and their performance was tested as follows: Referring to GB / T50080-2002 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the slump and air content of the samples were tested. Referring to JTS / T 226-2021 "Technical Specification for Self-Compacting Concrete in Water Transport Engineering", the V-shaped funnel passage time of the test specimen was measured. Refer to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" to test the compressive strength of the specimens; Three parallel tests were performed on each group of samples, and the average test results were recorded as shown in Table 1 below.

[0036]

[0037] As shown in Table 1, the self-compacting concrete prepared by this invention has high water reduction rate, low slump loss and high stability, and its overall performance is significantly improved.

[0038] Compared to Example 1, Comparative Example 1 did not add silicone-modified hyperbranched star polymer, Comparative Example 2 did not add polyether-modified silicone polymer, Comparative Example 3 adjusted the amount or compounding ratio of silicone-modified hyperbranched star polymer and polyether-modified silicone polymer, Comparative Example 4 used a hyperbranched star polymer without silicone functional groups to replace the silicone-modified hyperbranched star polymer (BASF FoamStar ST A38), and Comparative Example 5 used a common modified silicone defoamer to replace the polyether-modified silicone polymer (BASF FoamStar SI). In Comparative Example 6, a common defoamer (BJ0188) was used to completely replace the silicone-modified hyperbranched star polymer and the polyether-modified silicone polymer. The resulting performance indicators, such as slump and compressive strength, all decreased significantly. This indicates that the silicone-modified hyperbranched star polymer and the polyether-modified silicone polymer play irreplaceable multiple roles in the system. Moreover, the selection and weight ratio of the two are special. Arbitrarily replacing their composition or changing their ratio, or using a conventional defoamer to replace the silicone-modified hyperbranched star polymer and the polyether-modified silicone polymer in this invention, will not achieve the expected effect of this invention. This invention employs a specific ratio of organosilicon-modified hyperbranched star-shaped polymer (BASF FoamStar ST A38) and polyether-modified organosilicon polymer (BASF FoamStar SI 2210) in combination with polycarboxylate superplasticizer to form a dual defoaming system that combines rigidity and flexibility. This avoids the steric hindrance effect that may be introduced by the star-shaped structure, ensuring the migration and dispersion of defoaming components in the concrete system. On this basis, an air-entraining agent obtained from the compound is introduced, which synergistically lays the foundation for the high water reduction rate, low slump loss and high stability of self-compacting concrete.

[0039] Compared with Example 1, Comparative Examples 7 and 8 replaced the air-entraining agent with a single-component air-entraining agent, respectively. Comparative Example 10 adjusted the weight ratio of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate. The air content and slump loss over time increased significantly, and the compressive strength decreased significantly. This indicates that the compounding of sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate has a synergistic effect. The benzene ring structure of the former gives the bubbles rigidity, making them less likely to break during mixing and transportation. The polyoxyethylene segments of the latter give the bubbles flexibility and stability, enabling the bubbles to be evenly dispersed. That is, the compounding ratio range of each component in the air-entraining agent has its own particularity and irreplaceability. Only within this ratio range can the two form the best "bubble rigidity-flexibility balance". When within this range, the two can work together to introduce beneficial microbubbles without losing the workability and mechanical properties of concrete.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A self-compacting concrete, characterized in that, The self-compacting concrete comprises the following raw materials in parts by weight: 350-450 parts cement, 80-150 parts fly ash, 50-100 parts slag powder, 700-850 parts sand, 800-950 parts crushed stone, 8-15 parts high-performance water-reducing agent, 0.01-0.05 parts air-entraining agent, and 130-150 parts water. The high-performance water-reducing agent is obtained by blending polycarboxylate water-reducing agent, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer. The air-entraining agent is obtained by compounding sodium dodecylbenzene sulfonate and sodium fatty alcohol polyoxyethylene sulfonate.

2. The self-compacting concrete according to claim 1, characterized in that, The high-performance water-reducing agent comprises the following raw materials in parts by weight: 300-600 parts unsaturated polyether macromonomer, 30-50 parts unsaturated carboxylic acid, 1-1.4 parts organosilicon-modified hyperbranched star polymer, 0.1-0.7 parts polyether-modified organosilicon polymer, 2.5-3.5 parts oxidant, 0.8-1.2 parts reducing agent, 1-3 parts chain transfer agent, 10-20 parts neutralizing agent, and 450-550 parts water.

3. The self-compacting concrete according to claim 2, characterized in that, The unsaturated polyether macromonomer is selected from allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, or isopentenyl polyoxyethylene ether.

4. The self-compacting concrete according to claim 2, characterized in that, The unsaturated carboxylic acid is selected from acrylic acid or methacrylic acid.

5. The self-compacting concrete according to claim 2, characterized in that, The organosilicon-modified hyperbranched star polymer is BASF FoamStar ST A38.

6. The self-compacting concrete according to claim 2, characterized in that, The polyether-modified organosilicon polymer is BASF FoamStar SI 2210.

7. The self-compacting concrete according to claim 1, characterized in that, The mass ratio of sodium dodecylbenzenesulfonate to sodium fatty alcohol polyoxyethylene sulfonate is 1.2-2:

1.

8. The self-compacting concrete according to any one of claims 1-6, characterized in that, The preparation of the high-performance water-reducing agent includes the following steps: S11. Mix the unsaturated polyether macromonomer, oxidant, and water evenly to obtain the first solution; S12. Mix unsaturated carboxylic acid and water thoroughly to obtain a second solution; S13. Mix the reducing agent, chain transfer agent and water evenly to obtain the third solution; S14. Under stirring at 45℃ and 120-180 rpm, the second and third solutions are simultaneously added dropwise to the first solution. After the addition is complete, keep warm for 3 hours, then add the neutralizing agent and mix evenly to obtain the polycarboxylate superplasticizer. S15. Mix the polycarboxylate superplasticizer, organosilicon-modified hyperbranched star polymer, and polyether-modified organosilicon polymer evenly to obtain a high-performance superplasticizer.

9. The self-compacting concrete according to claim 8, characterized in that, The mass ratio of water in steps S11, S12, and S13 is 5-7:2-3:1; the dropping rate of the second solution in step S14 is 1.5-2.5 mL / min, and the dropping rate of the third solution is 0.4-0.8 mL / min; the stirring speed in step S15 is 200-300 rpm.

10. A method for preparing self-compacting concrete according to any one of claims 1-9, characterized in that, The method for preparing the self-compacting concrete includes the following steps: S21. At a stirring speed of 50-80 rpm, fly ash, sand, and crushed stone are mixed evenly. Cement is added and mixed evenly. Slag powder is added and mixed evenly. Finally, high-performance water-reducing agent, air-entraining agent, and water are added and mixed evenly to obtain the self-compacting concrete.

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