Concrete steel fiber gradient orientation method

Abstract

The invention discloses a concrete steel fiber gradient orientation method. The method comprises the following steps: (1) measuring the length-diameter ratio and magnetic conductivity of steel fibers and the plastic viscosity and density of cement paste; (2) adjusting the magnetic field intensity to 100mT, changing the direction of the magnetic field, and carrying out first single-direction orientation on the steel fiber reinforced concrete; (3) setting an orientation angle according to orientation requirements and calculating required magnetic field intensity, so that gradient orientation of the steel fibers is realized; (4) detecting the orientation result of the fiber; and (5) judging whether the steel fiber is oriented to a target angle, and if not, repeating the steps (3)-(4) until the steel fiber is oriented to the target angle. The method is simple in theory, gradient orientation of the steel fibers is achieved by applying proper magnetic field intensity, the situation that the steel fibers are distributed in the single direction is avoided, the steel fibers in the concrete are distributed in the specific direction through the method, the utilization rate of the steel fibers is increased to the maximum extent, and the tensile property of a concrete structure is improved.

Description

Technical Field

[0001] The invention relates to a method for gradient orientation of concrete steel fibers. Background Art

[0002] Steel fiber reinforced concrete (SFRC) is widely used in construction, bridges, and other fields due to its excellent mechanical properties. The distribution of steel fibers is crucial to the performance of concrete beams, especially in bending areas. Properly distributed steel fibers can significantly improve the beam's bending and crack resistance. However, the distribution of steel fibers in concrete is often haphazard, which impairs its performance.

[0003] In recent years, magnetic field orientation technology has become a new way to optimize the distribution of steel fibers. By guiding the directional distribution of steel fibers through the magnetic field, the overall performance of concrete can be improved. However, existing magnetic field orientation technologies are often limited to a single direction, lack precise control and verification methods, or only change the angle between the component and the magnetic field direction, but this method is not very effective for large and complex components. Therefore, the use of two-stage magnetic field orientation has become an effective way to solve this problem. After completing the initial single-direction orientation, the steel fiber is rotated by a certain angle by applying a gradient magnetic field of appropriate size and then stops rotating to achieve precise orientation. This technology can not only achieve precise orientation of steel fibers, but also improve the mechanical properties and durability of steel fiber concrete components, provide new technical support for its application, and minimize the loss of steel fibers. Summary of the Invention

[0004] This patent provides a method for gradient orientation of concrete steel fibers, which is used to solve the problem that the magnetic field can only have a single orientation and the orientation is inaccurate. The specific steps are as follows:

[0005] (1) Measure the aspect ratio and magnetic permeability of steel fibers and the plastic viscosity and density of cement slurry;

[0006] (2) Adjust the magnetic field intensity to 100 mT to orient the steel fiber concrete for the first time;

[0007] (3) According to the orientation requirements, the rotation target angle is set and the required magnetic field strength is calculated to enable the steel fiber to achieve gradient orientation. The specific calculation formula for the magnetic field strength is:

[0008]

[0009] Where B is the magnetic induction intensity of the magnetic field; η is the plastic viscosity of the cement paste; ρ is the density of the cement paste; μ is the relative magnetic permeability of the fiber; θ is the rotation target angle; μ0 is the vacuum magnetic permeability; Ψ is the aspect ratio of the steel fiber; L is the length of the steel fiber;

[0010] (4) Detection of fiber orientation results;

[0011] (5) Determine whether the steel fiber is oriented to the target angle. If not, repeat steps (3) to (4) until it is oriented to the target angle. The judgment is based on the deviation rate. To determine, where Δθ is the difference between the actual angle and the target angle. If the difference with the target angle is less than 5%, the orientation is completed. If it is greater than 5%, the magnetic field strength is applied again. Regarding the direction of the applied magnetic field, if the actual angle is greater than the target angle, a magnetic field in the opposite direction to the initial one is applied; if the actual angle is less than the target angle, the same magnetic field as the initial one is applied.

[0012] The primary orientation is to orient the steel fiber concrete from a three-dimensional random distribution to a unidirectional distribution along the direction of the magnetic field.

[0013] The gradient orientation is to generate a magnetic field perpendicular to the initially oriented steel fibers, the magnitude of which can be precisely adjusted by controlling the current.

[0014] The present invention demonstrates the following benefits: This method utilizes a two-stage magnetic field orientation. After initial orientation, a gradient magnetic field of appropriate magnitude is applied to rotate the steel fibers to a certain angle before stopping, achieving precise orientation and allowing for continuous correction thereafter. This technology not only achieves precise orientation of steel fibers, improving the mechanical properties and durability of steel fiber reinforced concrete beams, but also minimizes energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the process of the present invention

[0016] Figure 2 Schematic diagram of steel fiber distribution after initial orientation

[0017] Figure 3 Schematic diagram of steel fiber distribution after gradient orientation

[0018] Figure 4 Schematic diagram of steel fiber distribution after gradient orientation of beam components DETAILED DESCRIPTION

[0019] The following is a detailed description of the specific implementation of the present invention with reference to examples, so that those skilled in the art can accurately understand and implement the present invention. Step 1: Measure the basic parameters of cement paste and steel fiber

[0020] Basic parameters of cement paste

[0021] Plastic viscosity η 68.8 Pa·s Density ρ <![CDATA[2.5g / cm 3 ]]>

[0022] Basic parameters of steel fiber

[0023] Fiber relative magnetic permeability μ 3000 Steel fiber diameter d 0.54mm Steel fiber length L 20mm

[0024] Step 2: Initial orientation of steel fiber concrete

[0025] According to the conservative situation, the initial orientation magnetic field strength was selected as 100mT. After the orientation was completed, the ultrasonic detection showed that all the steel fibers had been oriented, so that the steel fibers were oriented from three-dimensional random distribution to unidirectional distribution along the magnetic field direction.

[0026] Step 3: Select the orientation angle of 30°, 45°, or 60° according to the different stress conditions of the structure.

[0027] Substitute into the formula Calculate the required magnetic field strength

[0028] Angle (°) Magnetic field size (mT) 30 29.208 45 32.125 60 38.203

[0029] Step 4: Check whether the requirements are met and make corresponding adjustments based on actual conditions.

[0030] (1) Test the steel fiber reinforced concrete with an inclination of 30°. The actual value is 38°. The deviation rate is 16.7%, which is greater than the error requirement of 5%. Therefore, it is necessary to apply the magnetic field in the opposite direction to the first time again. The magnitude of the magnetic field is as follows: Calculation, calculated B new After the re-orientation was completed at 31.55mT, it was tested and met the error requirements, so the orientation was completed.

[0031] (2) The steel fiber reinforced concrete with an inclination of 45° was tested. The test found that the orientation angle was 43°, and the deviation from the target value was 4.4%, which was less than 5% and met the error requirement. Therefore, the orientation was completed.

[0032] (3) Test the steel fiber reinforced concrete with an inclination of 60°. The actual value is 55°. The deviation rate is 8.3%, which does not meet the 5% error requirement. Therefore, the magnetic field should be applied again in the same direction as the first time. The magnetic field size should be based on Calculation, calculated B new The value is 39.77 mT. After the re-orientation is completed, it is tested and the error requirement is met, so the orientation is completed.

Claims

1. A method for gradient orientation of concrete steel fibers, characterized in that: The following steps are involved: (1) Measure the aspect ratio and magnetic permeability of steel fibers and the plastic viscosity and density of cement slurry; (2) Adjust the magnetic field intensity to 100 mT, change the magnetic field direction, and perform the first single-direction orientation on the steel fiber concrete; (3) Setting the orientation angle according to the orientation requirements and calculating the required magnetic field strength to achieve gradient orientation of the steel fiber; (4) Detection of fiber orientation results; (5) Determine whether the steel fiber is oriented to the target angle. If not, repeat steps (3) to (4) until the steel fiber is oriented to the target angle.

2. A method for gradient orientation of concrete steel fibers according to claim 1, characterized in that The magnetic field intensity in step (2) is adjusted to 100 mT to orient the steel fiber concrete from a three-dimensional random distribution to a unidirectional distribution along the direction of the magnetic field.

3. The method for gradient orientation of concrete steel fibers according to claim 1, characterized in that The gradient orientation in step (3) is that the orientation angle θ starts from the horizontal direction and rotates counterclockwise to the orientation position, and the value of θ ranges from 0 degrees to 90 degrees.

4. A method for gradient orientation of concrete steel fibers according to claim 1, characterized in that The formula for calculating the magnetic field strength in step (3) is specifically: Where B is the magnetic induction intensity of the magnetic field; η is the plastic viscosity of the cement slurry; ρ is the density of the cement slurry; μ is the relative magnetic permeability of the fiber; θ is the orientation angle; μ0 is the vacuum magnetic permeability; Ψ is the aspect ratio of the steel fiber; and L is the length of the steel fiber.

5. A method for gradient orientation of concrete steel fibers according to claim 1, characterized in that In the step (4), an ultrasonic detector is used to non-destructively detect the orientation result.

6. A method for gradient orientation of concrete steel fibers according to claim 1, characterized in that The determination of whether the magnetic field intensity is directed to the target angle in step (5) is based on the deviation rate is determined by, where Δθ is the difference between the actual angle and the target angle. If the difference with the target angle is greater than 5%, the magnetic field strength applied again is Regarding the direction of the applied magnetic field, if the actual angle is greater than the target angle, a magnetic field in the opposite direction to the initial one is applied; if the actual angle is less than the target angle, the same magnetic field as the initial one is applied.

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