Rotating magnetic field assisted dispersed fiber concrete and method of making same

Abstract

This invention discloses a fiber-reinforced concrete with rotating magnetic field-assisted dispersion. The raw materials and their weight percentages include: 420-450 parts ordinary Portland cement, 500-560 parts sand, 1000-1200 parts aggregate, 25-40 parts silica fume, 10-15 parts magnetic component, 0.8-1.2 parts fiber, 4-8 parts accelerator, 7-10 parts water-reducing agent, and 160-165 parts water. A rotating magnetic field is introduced during the mixing process. This invention employs a formulation system based on ordinary Portland cement, silica fume, magnetic component, fiber, and dispersant, combined with a rotating magnetic field, which effectively promotes the uniform dispersion of fibers in concrete, achieving both good workability and mechanical properties. Furthermore, the preparation method is relatively simple, easy to operate, and suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a rotating magnetic field-assisted dispersion of fiber-reinforced concrete and its preparation method. Background Technology

[0002] Adding a certain amount of fiber during the concrete mixing process can effectively prevent early cracking and significantly improve concrete durability. However, fibers tend to aggregate in concrete, especially longer or larger fibers, which can lead to uneven fiber quantity and distribution, limiting the fiber's ability to improve concrete performance and causing problems such as inconsistent uniformity and mechanical properties. Furthermore, if fibers cannot be well dispersed in the concrete during construction, it can increase construction difficulty, such as fiber clogging of pipes or difficulty in evenly distributing bulky fibers within the mold.

[0003] To overcome the aforementioned problems, existing improvement measures include changing the type and size of fibers, optimizing the concrete mix proportions and construction methods, using concrete additives, and improving construction techniques. However, existing control measures usually affect the original components or expected properties of the concrete to some extent. Further exploration of fiber-reinforced concrete that can effectively preserve the original components and their properties, and improve the fiber dispersion effect, has significant research and application value. Summary of the Invention

[0004] The purpose of this invention is to address the problems and shortcomings of existing technologies by providing a fiber-reinforced concrete with a rotating magnetic field for dispersion. The invention employs a formulation system based on ordinary silicate cement, silica fume, magnetic components, fibers, and accelerators, combined with a rotating magnetic field. This effectively promotes the uniform dispersion of fibers in concrete, achieving good workability and mechanical properties. Furthermore, the preparation method is relatively simple, easy to operate, and suitable for widespread application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A type of fiber-reinforced concrete with rotating magnetic field-assisted dispersion comprises the following raw materials and their respective weight proportions: 420-450 parts cement, 500-560 parts sand, 1000-1200 parts aggregate, 20-40 parts silica fume, 10-15 parts magnetic components, 0.8-1.2 parts fiber, 4-8 parts accelerator, 7-10 parts polycarboxylate superplasticizer, and 160-165 parts water; the mixing process is carried out under rotating magnetic field conditions.

[0007] In the above scheme, the silica fume has a particle size of 0.1-0.3μm, which has good filling effect, and its SiO2 content is greater than 90%, which is beneficial to enhancing the antioxidant properties of carbonyl iron powder.

[0008] In the above scheme, the magnetic component is carbonyl iron powder with a particle size of 1-3 μm.

[0009] In the above scheme, the fiber is polypropylene fiber, with a length of 20-30mm and a diameter of 0.3-0.8mm.

[0010] In the above scheme, the accelerator is sodium orthosilicate, with a specific gravity of 1.3-1.5 and a specific surface area greater than 200 m². 2 / kg.

[0011] In the above scheme, the cement is ordinary Portland cement with a 28-day compressive strength greater than 42.5 MPa, a sieve residue of greater than 5% on a 45 μm square mesh sieve, and a specific surface area greater than 300 m². 2 / kg.

[0012] In the above scheme, the fineness modulus of the sand (preferably quartz sand) is 2.5-2.8, and it is medium sand in zone two; the stone (preferably quartz stone) has a continuous gradation of 5-16mm, a crushing value of ≤6%, and a needle-like and flaky content of less than 6%.

[0013] In the above scheme, the water-reducing agent has a water reduction rate of 12-20%.

[0014] The above-mentioned method for preparing fiber-reinforced concrete with rotating magnetic field-assisted dispersion includes the following steps:

[0015] 1) Weigh the raw materials according to the proportions. The raw materials and their weight percentages are as follows: 420-450 parts cement, 500-560 parts sand, 1000-1200 parts stone, 20-40 parts silica fume, 10-15 parts magnetic material, 0.8-1.2 parts fiber, 4-8 parts accelerator, 7-10 parts water-reducing agent, and 160-165 parts water.

[0016] 2) The weighed silica fume, magnetic components, and fibers are mixed once to obtain the functional dry material component; the sand, stone, and cement are mixed evenly to obtain the matrix dry material component.

[0017] 3) Under rotating magnetic field conditions, functional dry material components are added to the matrix dry material components, and a second stirring treatment is performed. Then, a mixture of water, accelerator and water-reducing agent is added, and a third stirring treatment is performed to obtain the mixture.

[0018] 4) Continue to vibrate the resulting mixture under rotating magnetic field conditions to obtain the self-dispersing concrete.

[0019] In the above scheme, the time for the first stirring treatment is 2-3 minutes; the time for the second stirring treatment is 1-2 minutes; and the time for the third stirring treatment is 3-5 minutes.

[0020] In the above scheme, the rotating magnetic field is formed by passing a balanced three-phase current through three-phase symmetrical windings, with a rotation speed of 2000-3000 r / min, a frequency of 50-200 Hz, and the three sets of spatial phases differing by 120° electrical angle, and the number of pole pairs is 2.

[0021] In the above scheme, the vibration mode step uses a frequency of 6-10 alternating left and right movements, once per second, with an amplitude of 3-5cm.

[0022] The fiber-reinforced concrete prepared according to the above scheme has an initial slump of over 200 mm. Relevant tests on the hardened concrete revealed that the internal fibers are relatively uniformly dispersed, and the mechanical properties at 28 days are improved by more than 10% compared with conventional methods, which can effectively improve the performance and service life of concrete.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1) The carbonyl iron powder incorporated in this invention can be uniformly adsorbed onto polypropylene fibers. Under the magnetic field generated by the applied alternating current, the carbonyl iron powder will be magnetized and, under the action of the rotating magnetic field, will drive the polypropylene fibers to be uniformly dispersed in the concrete.

[0025] 2) During the growth of concrete structures, when uneven growth occurs, under the influence of entropy increase, the combined self-agglomeration effect of carbonyl iron powder and silica fume can drive polypropylene fibers to migrate to the "uneven growth zone" and promote the improvement of the compactness of concrete structures.

[0026] 3) The introduced silica fume is small in size, which can fill the micropores and defects on the surface of carbonyl iron powder and form a uniform, continuous and dense coating layer. The coating layer can significantly improve the oxidation resistance of carbonyl iron powder, which is beneficial to improving the stability of carbonyl iron powder in concrete and making the concrete structure more stable.

[0027] 4) The silica fume and carbonyl iron powder introduced in this invention can effectively reduce the porosity of concrete, improve the homogeneity of the structure, and enhance the durability of concrete.

[0028] 5) The sodium orthosilicate introduced in this invention can form an ionic state with a strong negative charge in concrete solution and can be uniformly dispersed in the solution. Under the action of an alternating magnetic field, the alternating magnetic field applies an electrodynamic force to the charged particles. The charged ions move under the action of the alternating magnetic field and can further contact and magnetize the carbonyl iron powder attached to the polypropylene fiber, thereby playing a role in promoting dispersion and further enhancing the dispersion effect of the fiber. Detailed Implementation

[0029] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. These descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0030] In the following examples, the silicate cement used is Huaxin PO 42.5 ordinary silicate cement, with a 28-day strength of 52.9 MPa, a sieve residue of 6.9% on a 45 μm square mesh sieve, and a specific surface area of ​​368 m². 2 / kg; Silica fume is from Henan Yixiang New Material Technology Co., Ltd., with a particle size of 0.1-0.3μm and a SiO2 mass fraction of 92.4%; Carbonyl iron powder is from Chengdu Jiachi Technology Co., Ltd., model JCM-1, with a particle size of 1-3μm, of which 97.3% are smaller than 3μm; Polypropylene fiber is from Shandong Guangtong Engineering Materials Co., Ltd., with a density of 0.92g / cm³. 3 The elastic modulus is 3550MPa, the length is between 20-30mm, and the diameter is between 0.3-0.8mm;

[0031] The sand used is quartz sand with a fineness modulus of 2.6, classified as medium sand in zone two; the stone used is quartz stone with a continuous gradation of 5-16mm, a crushing value of ≤6%, a mud content of ≤0.5%, and a needle-like and flaky content of 0.6%.

[0032] The polycarboxylate superplasticizer used was manufactured by China Construction Western Construction New Materials Technology Co., Ltd., model ZJC-01, with a solid content of 10.2% and a concrete water reduction rate of 29%.

[0033] Example 1

[0034] A rotating magnetic field-assisted dispersed fiber-reinforced concrete is prepared by the following steps:

[0035] 1) Weighing of raw materials: the raw materials and their weight percentages are as follows: 430 parts ordinary silicate cement, 520 parts quartz sand, 1050 parts quartz stone, 30 parts silica fume, 12 parts carbonyl iron powder, 6 parts sodium orthosilicate, 0.9 parts polypropylene fiber, 8 parts polycarboxylate superplasticizer, and 160 parts water.

[0036] 2) Stir the weighed silica fume, magnetic components and fibers evenly (2 min) to obtain functional dry material components. Stir the quartz sand, quartz stone and cement evenly (2 min) to obtain matrix dry material components.

[0037] 3) In a rotating magnetic field, add functional dry material components to the matrix dry material components and stir for 1 min. Then add a mixed solution of water-reducing agent, water and accelerator and stir for 3 min to obtain the mixture.

[0038] 4) Continue to vibrate the obtained mixture under the rotating magnetic field condition to obtain the fiber-reinforced concrete after auxiliary dispersion;

[0039] The rotating magnetic field is formed by passing a balanced three-phase current through three-phase symmetrical windings. The three sets of spatial phases differ by 120° electrical angles, and the number of pole pairs is 2. The vibration mode frequency is 8 times on each side, once per second, and the amplitude is 3-5cm.

[0040] Example 2

[0041] A rotating magnetic field-assisted dispersion fiber concrete and its preparation method are disclosed. The preparation method is generally the same as that in Example 1, except that the raw materials and their weight proportions are as follows: 420 parts of ordinary silicate cement, 540 parts of quartz sand, 1030 parts of quartz stone, 40 parts of silica fume, 10 parts of carbonyl iron powder, 5 parts of sodium orthosilicate, 0.8 parts of polypropylene fiber, 8 parts of polycarboxylate superplasticizer, and 160 parts of water.

[0042] Example 3

[0043] A rotating magnetic field-assisted dispersion fiber concrete and its preparation method are disclosed. The preparation method is generally the same as that in Example 1, except that the raw materials and their weight proportions are as follows: 440 parts of ordinary silicate cement, 500 parts of quartz sand, 1070 parts of quartz stone, 20 parts of silica fume, 14 parts of carbonyl iron powder, 8 parts of sodium orthosilicate, 1.1 parts of polypropylene fiber, 8 parts of polycarboxylate superplasticizer, and 160 parts of water.

[0044] Comparative Example 1

[0045] A self-dispersing concrete based on a rotating magnetic field is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 430 parts ordinary silicate cement, 526 parts quartz sand, 1056 parts quartz stone, 30 parts admixture, 0.9 parts polypropylene fiber, 6 parts sodium orthosilicate, 8 parts polycarboxylate superplasticizer, and 160 parts water.

[0046] Comparative Example 2

[0047] A self-dispersing concrete based on a rotating magnetic field is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 430 parts of ordinary silicate cement, 523 parts of quartz sand, 1053 parts of quartz stone, 30 parts of admixture, 0.9 parts of polypropylene fiber, 12 parts of carbonyl iron powder, 8 parts of polycarboxylate superplasticizer, and 160 parts of water.

[0048] Comparative Example 3

[0049] A self-dispersing concrete based on a rotating magnetic field is prepared in a manner similar to that of Example 1, except that the raw materials and their weight percentages are as follows: 432 parts ordinary silicate cement, 526 parts quartz sand, 1056 parts quartz stone, 34 parts admixture, 0.9 parts polypropylene fiber, 8 parts polycarboxylate superplasticizer, and 160 parts water.

[0050] Comparative Example 4

[0051] A self-dispersing concrete based on a rotating magnetic field is prepared in a manner similar to that of Example 1, except that the mixing steps are as follows: the admixtures (cement, silica fume), magnetic components, aggregates (sand, stone), and fibers are mixed evenly, and then a mixture of water, sodium orthosilicate, and polycarboxylate superplasticizer is added and mixed evenly.

[0052] The concrete samples formed in Examples 1-3 and Comparative Examples 1-4 were tested for workability, mechanical properties, and cross-sectional characteristics. Specifically, the initial flowability and spread of the fresh concrete were measured. The concrete was molded into 150mm×150mm×150mm molds to test the compressive strength and into 150mm diameter and 300mm height molds to test the tensile strength. After curing under standard conditions for 3 days and 28 days, the compressive and tensile strengths of the specimens were tested. At the same time, the 28-day specimens were cut open to observe the fiber dispersion in the concrete cross-section. This method was used to evaluate the effect achieved by each group of specimens. The specific test data indicators are shown in Table 1 below.

[0053] Table 1. Performance test results of self-dispersible concrete obtained from the examples and comparative examples.

[0054]

[0055] The test results above show that the concrete obtained by this invention has excellent workability and mechanical properties, and its crack resistance is significantly improved. From the internal cross-section of the concrete, the fiber dispersion is relatively uniform and good.

[0056] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A type of fiber-reinforced concrete dispersed with the aid of a rotating magnetic field, characterized in that, The raw materials and their respective weight percentages include: 420-450 parts cement, 500-560 parts sand, 1000-1200 parts stone, 20-40 parts silica fume, 10-15 parts magnetic components, 0.8-1.2 parts fiber, 4-8 parts accelerator, 7-10 parts water-reducing agent, and 160-165 parts water; a rotating magnetic field is introduced during the mixing process. The magnetic component is carbonyl iron powder; the fiber is polypropylene fiber.

2. The fiber-reinforced concrete according to claim 1, characterized in that, The silica fume has a particle size of 0.1-0.3 μm and a SiO2 content greater than 90 wt%.

3. The fiber-reinforced concrete according to claim 1, characterized in that, The particle size of the magnetic component is 1-3 μm.

4. The fiber-reinforced concrete according to claim 1, characterized in that, The fiber has a length of 20-30 mm and a diameter of 0.3-0.8 mm.

5. The fiber-reinforced concrete according to claim 1, characterized in that, The accelerator is sodium orthosilicate.

6. The fiber-reinforced concrete according to claim 1, characterized in that, The cement is ordinary Portland cement with a 28-day compressive strength greater than 42.5 MPa, a sieve residue greater than 5% on a 45 μm square mesh sieve, and a specific surface area greater than 300 m². 2 / kg.

7. The fiber-reinforced concrete according to claim 1, characterized in that, The fineness modulus of the sand is 2.5-2.8, which is medium sand in Zone II; the stone has a continuous gradation of 5-16mm, a crushing value of ≤6%, and a needle-like and flaky content of less than 6%.

8. The fiber-reinforced concrete according to claim 1, characterized in that, The water-reducing agent has a water reduction rate of 12-30%.

9. The method for preparing fiber-reinforced concrete with rotating magnetic field-assisted dispersion according to any one of claims 1 to 8, characterized in that, Includes the following steps: 1) Weigh the raw materials according to the proportions. The raw materials and their weight percentages are as follows: 420-450 parts cement, 500-560 parts sand, 1000-1200 parts stone, 20-40 parts silica fume, 10-15 parts magnetic material, 0.8-1.2 parts fiber, 4-8 parts accelerator, 7-10 parts water-reducing agent, and 160-165 parts water. 2) The weighed silica fume, magnetic components and fibers are mixed once to obtain the functional dry material component; the sand, stone and cement are mixed evenly to obtain the matrix dry material component. 3) Under rotating magnetic field conditions, functional dry material components are added to the matrix dry material components, and a second stirring treatment is performed. Then, a mixture of water, accelerator and water-reducing agent is added, and a third stirring treatment is performed to obtain the mixture. 4) Continue to vibrate the obtained mixture under the rotating magnetic field condition to obtain the fiber concrete with rotating magnetic field-assisted dispersion.

10. The preparation method according to claim 9, characterized in that, The rotating magnetic field is formed by passing a balanced three-phase current through three-phase symmetrical windings. The rotation speed is 2000-3000 r / min, the frequency is 50-200 Hz, the three sets of spatial phases differ by 120° electrical angle, and the number of pole pairs is 2.

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