Concrete mixing uniformity evaluation method and system based on fractal theory

Abstract

The invention relates to a fractal theory-based concrete mixing uniformity evaluation method and system, and the method comprises the steps: S10, collecting the surface contour data of to-be-evaluated newly mixed concrete; s20, generating a surface elevation map based on the surface contour data; s30, performing multi-fractal analysis on the surface elevation map based on a fractal theory, and determining a multi-fractal spectral width of the surface elevation map; the multi-fractal spectrum width is used for representing the fluctuation degree of the concrete surface of each area in the surface elevation map; the smaller the width of the multi-fractal spectrum is, the smaller the fluctuation degree of the surface of the concrete in each area in the elevation map is, and the better the stirring uniformity of the concrete is; and S40, evaluating the stirring uniformity of the concrete based on the multi-fractal spectrum width. According to the evaluation method, the accuracy of an evaluation result is improved, and the defects of a traditional method in the aspect of mixing uniformity evaluation are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete quality inspection, and particularly to a method and system for evaluating the mixing uniformity of concrete based on fractal theory. Background Art

[0002] With the continuous improvement of the quality requirements for concrete in the construction industry, the mixing uniformity of concrete has become a key factor affecting its physical properties and durability. Uniform concrete can ensure the mechanical properties, durability and crack resistance of structures, thus preventing problems such as insufficient strength, cracks and deformations caused by non-uniform materials. The lack of an effective uniformity assessment may lead to unstable construction quality, increase the risk of maintenance and reconstruction, and thus affect the safety and service life of the project. Therefore, accurate uniformity evaluation is a crucial step in ensuring project quality and building safety.

[0003] The prior art generally collects images of the concrete surface and evaluates the surface uniformity of the concrete by observing surface defects (such as bubbles and non-uniform distribution of ingredients).

[0004] For example, the prior art proposes a method for monitoring the mixing quality of concrete through machine vision technology. The system uses a CCD camera to capture images during the concrete mixing process and analyzes the mixing state of the concrete through image processing technology. Although this method can provide visual information during the mixing process and can detect obvious surface defects (such as bubbles and non-uniform distribution), it mainly depends on the image quality of the vision system and environmental lighting conditions, may be interfered, and it is difficult to deeply analyze the internal uniformity of the concrete.

[0005] Another prior art proposes a method for evaluating the mixing quality of concrete through gray-scale image analysis. The system uses image processing technology to scan the surface of the concrete and detect defects such as bubbles and non-uniform distribution. Although this method can identify surface defects, it does not conduct a detailed analysis of the internal uniformity of the concrete during the mixing process, limiting its comprehensive evaluation of the actual mixing quality.

[0006] Furthermore, the prior art proposes a real-time imaging system based on a sensitive electrode array, which detects the degree of impurity mixing by measuring the distribution of concrete through electrical signals. The system images the medium distribution through a linear back-projection algorithm. This system can monitor the impurity mixing situation in the concrete in real time, identify the position and degree of impurities, so as to conduct quality control. Although this system has advantages in real-time monitoring and identifying impurities, its detection principle depends on the change of electrical signals, mainly focuses on the impurities in the concrete, and cannot comprehensively evaluate the overall mixing uniformity of the concrete. In addition, the accuracy of the imaging system is limited by the arrangement of the electrode array and the processing accuracy of electrical signals.

[0007] There is also a prior art method for evaluating the workability of high-fluidity ultra-high performance concrete mixtures, which evaluates the performance by measuring the flow distance and segregation resistance of the concrete. Detailed evaluation methods for fluidity, segregation resistance, as well as steel fiber stability and distribution uniformity are provided, which are applicable to the characteristic analysis of high-fluidity concrete. This method mainly focuses on the fluidity and separation of the concrete mixture and fails to deeply analyze the mixing uniformity during the concrete mixing process. The method relies on static flow tests and fails to monitor the actual mixing situation of the concrete during the mixing process in real time.

[0008] There is also a prior art device for evaluating the uniformity of bamboo aggregate cement concrete mixtures. The vibration device is used to make the concrete mixture move uniformly in the barrel body and flow out through multiple through holes in sequence for weighing analysis. This device can effectively evaluate the uniformity of bamboo aggregate cement concrete, is applicable to mixtures with different proportions, and provides a dynamic detection environment through vibration. However, this method mainly relies on vibration to promote the outflow of the mixture. Although multiple samples can be obtained for uniformity analysis, it fails to monitor the mixing uniformity in real time during the mixing process. Moreover, the evaluation of the microscopic uniformity and structural characteristics of different components in the concrete is relatively lacking, and it may not be able to comprehensively reflect the true quality of the mixture.

[0009] In summary, most of the existing evaluation methods for concrete mixing uniformity rely on physical sampling and laboratory analysis, often requiring offline detection after concrete pouring, resulting in the inability to reflect the actual state of the concrete during the construction process in real time. At the same time, the existing methods may be affected by insufficient sample representativeness and operational complexity, and cannot comprehensively capture all non-uniformity problems in the concrete, such as uneven aggregate distribution or slurry separation. In addition, some methods in the prior art may not be able to handle the special requirements of high-fluidity concrete, limiting their application scope, and having limitations in terms of real-time performance, comprehensiveness, and accuracy. The evaluation of the microscopic uniformity and structural characteristics of different components in the concrete is relatively lacking, and it cannot comprehensively reflect the true quality of the concrete mixture. Summary of the Invention

[0010] (1) Technical Problems to be Solved

[0011] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a method and system for evaluating concrete mixing uniformity based on fractal theory, which solves the technical problem that it is difficult to accurately evaluate the mixing uniformity of concrete in the prior art.

[0012] (2) Technical Solutions

[0013] To achieve the above object, the main technical solutions adopted by the present invention include:

[0014] In a first aspect, an embodiment of the present invention provides a method for evaluating the mixing uniformity of concrete based on fractal theory, including:

[0015] S10. For freshly mixed concrete to be evaluated, collect the surface profile data of the concrete;

[0016] S20. Generate a surface elevation map based on the surface profile data;

[0017] S30. Perform multifractal analysis on the surface elevation map based on fractal theory to determine the multifractal spectrum width of the surface elevation map;

[0018] The multifractal spectrum width is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; when the multifractal spectrum width is smaller, it indicates that the undulation degree of the concrete surface in each area of the elevation map is smaller, and the mixing uniformity of the concrete is better;

[0019] S40. Evaluate the mixing uniformity of the concrete based on the multifractal spectrum width.

[0020] Optionally, S10 includes:

[0021] Scan from directly above the freshly mixed concrete to be evaluated to obtain the surface profile data of the concrete;

[0022] The scanning resolution ≤ 0.5 mm, and the distance between the scanning device and the concrete surface ≥ 50 cm and ≤ 100 cm;

[0023] The freshly mixed concrete to be evaluated is: concrete that has been static for a preset duration during or after the mixing process.

[0024] Optionally, S20 includes:

[0025] Taking the horizontal plane where the point corresponding to the minimum value in the surface profile data is located as the reference plane, generate the surface elevation map so that the heights of all points in the surface elevation map are positive values.

[0026] Optionally, S30 includes:

[0027] S301. Use the box-counting method to square-grid the surface elevation map, with each grid corresponding to a box, so that several boxes cover all areas of the surface elevation map;

[0028] S302. Statistically analyze the distribution probability of the concrete surface height in each box;

[0029] S303. Substitute the distribution probability into a pre-constructed partition function;

[0030] S304. Calculate the multifractal spectrum by the Renyi transformation based on the scaling property of the partition function;

[0031] S305. Determine the multifractal spectrum width of the surface elevation map based on the multifractal spectrum.

[0032] Optionally, S302 includes: obtaining the sum of the concrete surface heights in each box, and calculating the distribution probability of the concrete surface heights in each box according to formula (1);

[0033] P ij (r) = S ij (r) / S T (r) (1);

[0034] where r refers to the side length of the box; P ij (r) refers to the distribution probability of the concrete surface height in the box at the i-th row and j-th column, S ij refers to the sum of the concrete surface heights in the box at the i-th row and j-th column, S T refers to the sum of the concrete surface heights in all boxes.

[0035] Optionally, in S303, substituting the distribution probability into the pre-constructed partition function includes:

[0036] The pre-constructed partition function χ(q,r) is:

[0037]

[0038] where N(r) refers to the total number of boxes, and the order q is any real number.

[0039] Optionally, in S304,

[0040] The scaling property of the partition function is:

[0041] χ(q,r) ~ r -τ(q) (3);

[0042] where r refers to the side length of the box; τ(q) refers to the mass exponent;

[0043] Calculating the multifractal spectrum by the Renyi transformation includes:

[0044] Solving the multifractal spectrum of the surface elevation map according to formula (4);

[0045]

[0046] where α refers to the singularity; f(α) refers to the multifractal spectrum.

[0047] Optionally, S305 includes:

[0048] Determine the left endpoint value α of α according to the function image of the multifractal spectrum min and the right endpoint value α max ; Determine the multifractal spectrum width of the surface elevation map according to formula (5);

[0049] Δα = α max -α min (5);

[0050] where Δα refers to the multifractal spectrum width; α min refers to the left endpoint value of α in the function image of the multifractal spectrum; α max refers to the right endpoint value of α in the function image of the multifractal spectrum.

[0051] Optionally, S40 includes:

[0052] When Δα < 0.926, it is determined that the mixing uniformity of the concrete is excellent;

[0053] When 0.926 ≤ Δα < 1.081, it is determined that the mixing uniformity of the concrete is good;

[0054] When Δα ≥ 1.081, it is determined that the mixing uniformity of the concrete is poor.

[0055] In a second aspect, an embodiment of the present invention provides a concrete mixing uniformity evaluation system based on fractal theory, including:

[0056] A surface profile acquisition device for collecting surface profile data of freshly mixed concrete to be evaluated;

[0057] An analysis device for generating a surface elevation map based on the surface profile data; performing multifractal analysis on the surface elevation map using fractal theory to determine the multifractal spectrum width of the surface elevation map; the multifractal spectrum width is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; and evaluating the mixing uniformity of the concrete based on the multifractal spectrum width.

[0058] (III) Advantageous Effects

[0059] The concrete mixing uniformity evaluation method based on the fractal theory proposed by the present invention, for the freshly mixed concrete to be evaluated, collects the surface profile data of the concrete and generates a surface elevation map; performs multifractal analysis on the surface elevation map based on the fractal theory to determine the multifractal spectrum width of the surface elevation map; and evaluates the mixing uniformity of the concrete based on the multifractal spectrum width. The multifractal spectrum width is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; when the multifractal spectrum width is smaller, it indicates that the undulation degree of the concrete surface in each area of the elevation map is smaller, and the mixing uniformity of the concrete is better.

[0060] Based on the fractal theory, the evaluation method proposed by the present invention can deeply explore the microscopic structural characteristics of concrete and reveal the complexity in the mixing process. The fractal theory can better analyze the distribution of particles in concrete and its influence on the overall uniformity. By comparing the multifractal spectrum widths through the surface elevation map to reflect the undulation degree of the concrete surface, and then comparing the mixing uniformity of the concrete, it improves the accuracy of the evaluation results, makes up for the deficiencies of traditional methods in the evaluation of mixing uniformity, meets the high requirements of modern construction for the evaluation of concrete uniformity, and ensures the stability of project quality and the long-term performance of the structure. Description of the Drawings

[0061] Figure 1 The flow chart of a concrete mixing uniformity evaluation method based on the fractal theory provided for the embodiment;

[0062] Figure 2 The schematic diagram of the scanning area of the laser three-dimensional scanner provided for the embodiment;

[0063] Figure 3 The schematic diagram of the three-dimensional surface model of the freshly mixed concrete provided in the embodiment;

[0064] Figure 4 The surface elevation map of the concrete provided in the embodiment;

[0065] Figure 5 The multifractal spectrum provided in the embodiment;

[0066] Figure 6 The multifractal spectra of the concrete corresponding to the mixing times of 30 seconds, 45 seconds, 60 seconds, 75 seconds, and 90 seconds provided for the embodiment;

[0067] Figure 7 The schematic diagram of the relationship between the multifractal spectrum width and the mixing time of the concrete corresponding to the mixing times of 30 seconds, 45 seconds, 60 seconds, 75 seconds, and 90 seconds provided for the embodiment;

[0068] Figure 8Schematic diagram of the relationship between the multifractal spectrum width of concrete corresponding to stirring times of 20 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds, and 120 seconds provided for the examples and the stirring time. Detailed implementation manners

[0069] To better explain the present invention for easy understanding, the present invention will be described in detail below with reference to the accompanying drawings through specific implementation manners.

[0070] To better understand the above technical solution, the exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and the scope of the present invention can be fully conveyed to those skilled in the art.

[0071] Embodiment 1

[0072] As Figure 1 shown, this embodiment provides a method for evaluating the mixing uniformity of concrete based on the fractal theory, including steps S10 to S40:

[0073] S10. For the freshly mixed concrete to be evaluated, collect the surface profile data of the concrete.

[0074] Specifically, a laser three-dimensional scanner can be used to scan from directly above the freshly mixed concrete to be evaluated to obtain the surface profile data of the concrete; the surface profile data can also be referred to as three-dimensional lattice coordinate data or point cloud data.

[0075] The laser three-dimensional scanner can be a high-precision laser three-dimensional scanner with a scanning resolution of 0.01 to 0.5 mm. The distance between the laser three-dimensional scanner and the concrete surface is 50 to 100 cm, and the scanning speed can be 1000 to 900000 points / second; more preferably, the scanning speed can be 1000 to 2000 points / second. To ensure the accuracy of the surface profile data, the scanning environment of the laser three-dimensional scanner can also be ensured to be free of strong light interference by setting obstacles, etc.

[0076] The freshly mixed concrete to be evaluated is: the concrete that has been static for a preset duration during or after the mixing process. Preferably, the preset duration is 1 to 2 minutes.

[0077] S20. Generate a surface elevation map based on the surface profile data.

[0078] Specifically, a 3D modeling tool, Geomagic software, can be used to import the surface profile data to construct a 3D surface model of the fresh concrete. Based on the 3D surface model, a surface elevation map is generated, and pseudo-color mapping is applied to visualize the height differences.

[0079] Preferably, the horizontal plane corresponding to the point with the minimum value in the surface profile data can be used as the reference plane to generate the surface elevation map, so that the heights of all points in the surface elevation map are positive values.

[0080] S30. Perform multifractal analysis on the surface elevation map based on fractal theory to determine the multifractal spectrum width of the surface elevation map.

[0081] The multifractal spectrum width is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; when the multifractal spectrum width is smaller, it indicates that the undulation degree of the concrete surface in each area of the elevation map is smaller, and the mixing uniformity of the concrete is better.

[0082] S40. Evaluate the mixing uniformity of the concrete based on the multifractal spectrum width Δα.

[0083] Specifically, the evaluation criteria for S40 are specifically as follows

[0084] When Δα < 0.926, it is determined that the mixing uniformity of the concrete is excellent;

[0085] When 0.926 ≤ Δα < 1.081, it is determined that the mixing uniformity of the concrete is good;

[0086] When Δα ≥ 1.081, it is determined that the mixing uniformity of the concrete is poor.

[0087] The method for evaluating the mixing uniformity of concrete based on fractal theory proposed in this embodiment is directed to the fresh concrete to be evaluated, collects the surface profile data of the concrete and generates a surface elevation map; performs multifractal analysis on the surface elevation map based on fractal theory to determine the multifractal spectrum width of the surface elevation map; and evaluates the mixing uniformity of the concrete based on the multifractal spectrum width. The multifractal spectrum width is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; when the multifractal spectrum width is smaller, it indicates that the undulation degree of the concrete surface in each area of the elevation map is smaller, and the mixing uniformity of the concrete is better.

[0088] Based on fractal theory, the evaluation method proposed by the present invention can deeply explore the microscopic structural characteristics of concrete and reveal the complexity during the mixing process. Fractal theory can better analyze the particle distribution in concrete and its influence on the overall uniformity. By comparing the width of the multifractal spectrum through the surface elevation map to reflect the undulation degree of the concrete surface, and then comparing the mixing uniformity of concrete, the accuracy of the evaluation results is improved, making up for the deficiencies of traditional methods in evaluating mixing uniformity.

[0089] In addition, the evaluation method proposed in this embodiment obtains the three-dimensional structure data of concrete through laser three-dimensional scanning technology. It can not only monitor the surface condition of concrete in real time, but also deeply analyze the internal structure of concrete. Compared with the existing image processing and electrical signal measurement technologies, this method can provide more comprehensive and accurate mixing uniformity data. This method is not only applicable to the evaluation of the mixing uniformity of general concrete, but also can effectively analyze special proportioning and high-fluidity concrete, with strong versatility and practical application value.

[0090] Embodiment Two

[0091] To better understand the evaluation method provided in Embodiment One, this embodiment details the multifractal analysis method involved in step S30.

[0092] Specifically, embodiment S30 includes sub-steps S301 to S305:

[0093] S301. Using the box-counting method, square grid the surface elevation map, with each grid corresponding to a box, so that a number of boxes cover all areas of the surface elevation map.

[0094] Specifically, the surface elevation map can be gridded multiple times to obtain a sufficient number of boxes. For example, for a surface elevation map of 1024 pixels × 2048 pixels, using boxes with side length r for k traversal coverages, where r = L / 2 k , and the total number of boxes obtained is N(r);

[0095] When k = 1, r = 1024, N(r) = 2;

[0096] The total number of boxes N(r) obtained from the k-th traversal coverage is N(r) = 2 k .

[0097] The number of traversals, that is, the value range of the power value k, is [1, 10]. More preferably, the value range of the power value k is [6, 8].

[0098] It should be noted that each traversal obtains 2 kAfter a certain number of boxes, subsequent steps S302 to S305 need to be carried out. Each traversal will obtain a multifractal spectrum. As the number of traversals increases, the more points there are on the multifractal spectrum curve obtained, and the higher the curve accuracy of the drawn multifractal spectrum, and the more accurate the result.

[0099] S302. Statistically calculate the distribution probability P ij (r) of the concrete surface height in each box.

[0100] Specifically, obtain the sum of the concrete surface heights in each box, and calculate the distribution probability of the concrete surface height in each box according to formula (1);

[0101] P ij (r) = S ij (r) / S T (r) (1);

[0102] Among them, r refers to the side length of the box; P ij (r) refers to the distribution probability of the concrete surface height in the box at the i-th row and j-th column, S ij refers to the sum of the concrete surface heights in the box at the i-th row and j-th column, S T refers to the sum of the concrete surface heights in all boxes.

[0103] S303. Substitute the said distribution probability into the pre-constructed partition function χ(q, r).

[0104] Specifically, the pre-constructed partition function χ(q, r) is:

[0105]

[0106] Among them, N(r) refers to the total number of boxes, and the order q is an arbitrary real number.

[0107] Preferably, the value range of q is [-15, 15].

[0108] S304. Based on the scaling property of the partition function, calculate the multifractal spectrum by the Renyi transformation.

[0109] The scaling property of the said partition function is:

[0110] χ(q, r) ~ r -τ(q) (3);

[0111] Among them, r refers to the side length of the box; τ(q) refers to the mass exponent;

[0112] The calculation of the multifractal spectrum by the Renyi transformation includes:

[0113] Solve the multifractal spectrum for the surface elevation map according to formula (4);

[0114]

[0115] where α refers to the singularity; f(α) refers to the multifractal spectrum.

[0116] S305. Determine the multifractal spectrum width of the surface elevation map based on the multifractal spectrum.

[0117] Specifically, determine the left endpoint value α min and the right endpoint value α max of α according to the function image of the multifractal spectrum; determine the multifractal spectrum width of the surface elevation map according to formula (5);

[0118] Δα = α max - α min (5);

[0119] where Δα refers to the multifractal spectrum width; α min refers to the left endpoint value of α in the function image of the multifractal spectrum; α max refers to the right endpoint value of α in the function image of the multifractal spectrum.

[0120] Δα represents the width of the multifractal spectrum. When the height distribution of the concrete surface is more uniform, it indicates that the distribution of each phase of the material in the mixing process is more consistent, showing lower surface complexity. In fractal theory, a narrower spectrum width Δα usually indicates a higher self-similarity and uniformity of the concrete surface height distribution. This is because when Δα is larger, it indicates that there are large height differences on the surface, which usually means uneven mixing. On the contrary, when Δα is smaller, it means that the difference in elevation distribution is smaller, the surface is flatter, and the mixing of the concrete is more uniform.

[0121] The multifractal analysis method using box counting provided in this embodiment grids the surface elevation map of the concrete, so that the data statistically counted by each box corresponding to each grid can reflect the microscopic height distribution of the concrete surface in that grid, that is, the distribution probability P ij (r) of the concrete surface height in each box, so that the subsequent multifractal spectrum obtained based on this distribution probability P ij (r) can capture more detailed microscopic structural characteristics of the concrete, improve the feedback ability of the multifractal analysis result to the true quality of the freshly mixed concrete, and further improve the accuracy of the evaluation result of the mixing uniformity of the concrete in this embodiment.

[0122] Embodiment III

[0123] In this embodiment, combined with the actual application scenario, the method for evaluating the mixing uniformity of concrete provided in the first and second embodiments based on the fractal theory is described in detail.

[0124] Specifically, the method provided in this embodiment can be implemented as an evaluation device integrated on the host computer. This evaluation device directly receives the surface profile data of the concrete and implements steps S20 to S40 through a computer program. A laser three-dimensional scanner can also be set up to collect the surface profile data of the concrete and upload it to the above evaluation device for analysis and evaluation. For a mixing station with an open top, the three-dimensional laser scanner can be located directly above the opening of the mixing station; for a closed concrete mixing device, the three-dimensional laser scanner can also be set inside the top of the concrete mixing device.

[0125] The method provided in this embodiment can be used for remote data collection and statistics, and can also be directly applied to the concrete mixing site to perform real-time evaluation on the concrete during or just after the mixing process, so as to assist the staff on the mixing site to decide in real time whether to perform secondary mixing or adjust the equipment parameters during the mixing process according to the evaluation results, so as to improve the final mixing uniformity of the concrete.

[0126] In a specific implementation scheme of this embodiment, if a mixing pot with an open setting is used to mix concrete, the laser three-dimensional scanner can be erected through a bracket. The bracket is used to adjust the angle and position of the laser three-dimensional scanner to ensure that the distance and angle between the laser and the concrete surface are constant during the scanning process. The scanning resolution of the laser three-dimensional scanner is 0.01 mm, and the scanning speed is 900,000 times per second, ensuring the accurate capture of the minute unevenness on the concrete surface.

[0127] Based on the above settings, the method for evaluating the mixing uniformity of concrete based on the fractal theory provided in this embodiment specifically includes:

[0128] S00. Add cement, sand, gravel and water into the mixing pot in proportion. Start the mixer, and the mixer runs at a rate of 1440 r / min until the set time, then turn off the mixer and keep it static for 1 to 2 minutes to make the surface flat and naturally dissipate part of the bubbles.

[0129] S10. Surface profile data collection: Start the laser three-dimensional scanner and perform full-coverage scanning on the static surface of the concrete to collect its surface profile point cloud data. After each scan is completed, the data is transmitted to the computer for storage to ensure the integrity of the data. The schematic diagram of the scanning area of the laser three-dimensional scanner is as Figure 2 shown.

[0130] S20. Data processing: Use the 3D modeling tool Geomagic software to import the point cloud data and construct as Figure 3The three-dimensional surface model of the fresh concrete shown. Based on the three-dimensional surface model, a surface elevation map is generated, its size is cropped to 1024×2048 pixels, and pseudo-color mapping is applied to visualize the height differences. The surface elevation map of the concrete is as shown in Figure 4 shown.

[0131] S30. Perform multifractal analysis on the surface elevation map based on the fractal theory to determine the multifractal spectrum width of the surface elevation map. The specific steps of the multifractal analysis are the same as those in Embodiment 1 and Embodiment 2, and the obtained multifractal spectrum f(α) is as shown in Figure 5 shown.

[0132] According to the function image of the multifractal spectrum, determine the left endpoint value α min and the right endpoint value α max ; determine the multifractal spectrum width of the surface elevation map according to formula (5);

[0133] Δα = α max -α min (5);

[0134] where Δα refers to the multifractal spectrum width; α min refers to the left endpoint value of α in the function image of the multifractal spectrum; α max refers to the right endpoint value of α in the function image of the multifractal spectrum.

[0135] S40. Based on the multifractal spectrum width, judge the mixing uniformity of the concrete according to the following indicators:

[0136] When Δα < 0.926, it is determined that the mixing uniformity of the concrete is excellent;

[0137] When 0.926 ≤ Δα < 1.081, it is determined that the mixing uniformity of the concrete is good;

[0138] When Δα ≥ 1.081, it is determined that the mixing uniformity of the concrete is poor.

[0139] Based on the above specific embodiments, the inventors also carried out example verifications in the laboratory and at the mixing site respectively.

[0140] In the laboratory, based on the above steps S00 to S40, the set times of the mixer in S00 are set to 30 seconds, 45 seconds, 60 seconds, 75 seconds, and 90 seconds respectively. After each set mixing time, let it stand for 1 to 2 minutes, and respectively collect the corresponding concrete surface contour data through steps S10 to S40 and conduct analysis. The obtained multifractal spectra are as shown in Figure 6 shown, and the relationship between the corresponding multifractal spectrum width and the mixing time is as shown in Figure 7 shown. From Figure 7It can be seen that as the stirring time gradually increases, the width of the multifractal spectrum gradually decreases, indicating that the uniformity of the concrete gradually increases, which is also consistent with the actual experience.

[0141] At the construction site, based on the above steps S00 to S40, the set times of the mixer in S00 are set to 20 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds, and 120 seconds respectively. After each set stirring time, let it stand for 1 to 2 minutes, and collect the corresponding concrete surface profile data through steps S10 to S40 and analyze it. The relationship between the width of the multifractal spectrum and the stirring time is as Figure 8 shown. From Figure 8 It can be seen that this method can accurately capture the characteristics of the concrete surface height distribution, and through multifractal analysis, it provides a more consistent or even better evaluation result of the mixing uniformity than the traditional method. Moreover, this method can still accurately capture the characteristics of the concrete surface height distribution in a complex construction environment, and through multifractal analysis, it provides an evaluation result of the mixing uniformity that is close to that in the laboratory, significantly improving the efficiency and accuracy of construction quality control.

[0142] Example 4

[0143] Based on the evaluation methods provided in Examples 1 to 3, an embodiment of the present invention provides a concrete mixing uniformity evaluation system based on fractal theory, including a surface profile acquisition device and an analysis device:

[0144] The surface profile acquisition device is used to collect the surface profile data of the freshly mixed concrete to be evaluated. Specifically, the surface profile acquisition device can be a laser three-dimensional scanner.

[0145] The analysis device is used to generate a surface elevation map based on the surface profile data; perform multifractal analysis on the surface elevation map using fractal theory to determine the width of the multifractal spectrum of the surface elevation map; the width of the multifractal spectrum is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; based on the width of the multifractal spectrum, evaluate the mixing uniformity of the concrete.

[0146] The concrete mixing uniformity evaluation method based on fractal theory proposed in this embodiment, for the freshly mixed concrete to be evaluated, collects the surface profile data of the concrete and generates a surface elevation map; performs multifractal analysis on the surface elevation map based on fractal theory to determine the width of the multifractal spectrum of the surface elevation map; based on the width of the multifractal spectrum, evaluate the mixing uniformity of the concrete. The width of the multifractal spectrum is used to characterize the undulation degree of the concrete surface in each area of the surface elevation map; when the width of the multifractal spectrum is smaller, it indicates that the undulation degree of the concrete surface in each area of the elevation map is smaller, and the mixing uniformity of the concrete is better.

[0147] It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention can be implemented by means of hardware including several different elements and by means of a suitably programmed computer. In a claim listing several means, several of these means can be embodied by the same hardware. The use of the terms first, second, third, etc. is for convenience only and does not denote any order. These terms can be construed as part of the name of the element.

[0148] In addition, it should be noted that in the description of this specification, the descriptions of the terms "an embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0149] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications after learning the basic creative concept. Therefore, the claims should be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0150] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention should also include these modifications and variations.

Claims

1. A method for evaluating concrete mixing uniformity based on fractal theory, characterized in that: include: S10, collecting surface profile data of the freshly mixed concrete to be evaluated; S20, generating a surface elevation map based on the surface profile data; S30, performing multifractal analysis on the surface elevation map based on fractal theory to determine the multifractal spectrum width of the surface elevation map; The multifractal spectrum width is used to characterize the degree of undulation of the concrete surface in each area in the surface elevation map; when the multifractal spectrum width is smaller, it means that the degree of undulation of the concrete surface in each area in the elevation map is smaller, and the mixing uniformity of the concrete is better; S40. Evaluate mixing uniformity of concrete based on the multifractal spectrum width.

2. The evaluation method according to claim 1, characterized in that: The S10 includes: Scanning from directly above the freshly mixed concrete to be evaluated to obtain surface profile data of the concrete; The scanning resolution is ≤ 0.5 mm, and the distance between the scanning device and the concrete surface is ≥ 50 cm and ≤ 100 cm; The freshly mixed concrete to be evaluated is: concrete that is in the mixing process or has been left to stand for a preset time after the mixing is completed.

3. The evaluation method according to claim 1, characterized in that: The S20 includes: The surface elevation map is generated by taking the horizontal plane where the point corresponding to the minimum value in the surface profile data is located as the reference plane, so that the heights of all the points in the surface elevation map are positive values.

4. The evaluation method according to claim 1, wherein S30 comprises: S301, using a box counting method to square grid the surface elevation map, each grid corresponds to a box, so that a plurality of boxes cover all areas of the surface elevation map; S302, counting the distribution probability of the concrete surface height in each box; S303, substituting the distribution probability into a pre-constructed partition function; S304, calculating the multifractal spectrum by Gendler transformation based on the scaling property of the partition function; S305 . Determine a multifractal spectrum width of the surface elevation map based on the multifractal spectrum.

5. The evaluation method according to claim 4, characterized in that: The step S302 includes: obtaining the sum of the heights of the concrete surfaces in each box, and calculating the distribution probability of the heights of the concrete surfaces in each box according to formula (1); P ij (r)=S ij (r) / S T (r) (1); Among them, r refers to the side length of the box; P ij (r) refers to the distribution probability of the height of the concrete surface in the box at row i and column j, S ij refers to the sum of the heights of the concrete surfaces in the boxes in the i-th row and j-th column, S T Refers to the sum of the heights of the concrete surfaces in all boxes.

6. The evaluation method according to claim 5, characterized in that: In S303, the distribution probability is substituted into a pre-constructed partition function, including: The pre-built partition function χ(q,r) is: Here, N(r) refers to the total number of boxes and the order q is an arbitrary real number.

7. The evaluation method according to claim 6, characterized in that: In S304, The scaling property of the partition function is: x(q,r)~r -τ(q) (3); Where r refers to the side length of the box; τ(q) refers to the quality index; The method of calculating the multifractal spectrum by using the Gendler transform comprises: According to formula (4), the multifractal spectrum of the surface elevation map is solved; Here, α refers to the singularity; f(α) refers to the multifractal spectrum.

8. The evaluation method according to claim 7, characterized in that: The S305 includes: According to the function graph of the multifractal spectrum, determine the left endpoint value α of α min and the right endpoint value α max ; Determine the multifractal spectrum width of the surface elevation map according to formula (5); Dα=α max -a min (5); Among them, Δα refers to the multifractal spectrum width; α min Refers to the left endpoint value of α in the function graph of the multifractal spectrum; α max Refers to the right endpoint value of α in the function graph of the multifractal spectrum.

9. The evaluation method according to claim 8, characterized in that: The S40 includes: When Δα<0.926, it is determined that the mixing uniformity of the concrete is excellent; When 0.926≤Δα<1.081, it is determined that the mixing uniformity of the concrete is good; When Δα≥1.081, it is determined that the mixing uniformity of the concrete is poor.

10. A concrete mixing uniformity evaluation system based on fractal theory, characterized in that: include: A surface profile acquisition device, used for collecting surface profile data of the freshly mixed concrete to be evaluated; An analysis device is used to generate a surface elevation map based on the surface profile data; perform multifractal analysis on the surface elevation map using fractal theory to determine the multifractal spectrum width of the surface elevation map; The multifractal spectrum width is used to characterize the degree of undulation of the concrete surface in each area of ​​the surface elevation map; Based on the multifractal spectrum width, the mixing uniformity of the concrete is evaluated.

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