Method for determining improvement of effective depth of concrete by water permeable formwork cloth based on pore fractal dimension

Abstract

This invention discloses a method for determining the effective depth of permeable formwork fabric in improving concrete surface quality based on pore fractal dimension. First, the concrete is cut along a line perpendicular to the centerline of the permeable formwork fabric. The porosity of the cut surface is enhanced by applying ink and microsilica powder, and photographs are taken. A curve showing the change of pore fractal dimension of the concrete cut surface with depth is plotted. By comparing this curve with the pore fractal dimension curve of a cut surface without permeable formwork fabric, the effective depth of the permeable formwork fabric in improving the concrete surface quality is determined. Compared to traditional measurement methods, this invention offers advantages such as convenient testing, high identification accuracy, and quantitative analysis, providing a new method for evaluating the depth of permeable formwork fabric in improving the concrete surface quality.

Description

Technical Field

[0001] This invention belongs to the technical field of concrete surface improvement effect evaluation, specifically involving a method for determining the effective depth of permeable template cloth to improve concrete based on the fractal dimension of the pores. Background Technology

[0002] Large-volume concrete is prone to surface defects such as voids and pitting during vibration and curing, affecting its appearance and durability. Using permeable formwork can effectively improve concrete surface quality. However, different permeable formwork fabrics have significantly different effects on improving concrete surface quality. Previous studies often evaluated the improvement effect based on surface morphology characteristics, neglecting the quantification of the depth of improvement achieved by the permeable formwork fabric. The depth of improvement is crucial for enhancing concrete durability, necessitating the development of new testing methods.

[0003] To accurately identify structures at different depths within concrete, Chinese invention patent (authorization announcement number: CN103114514B) discloses an algorithm for detecting the depth of grooved structures in cement concrete pavements. This patent obtains the structural depth value of the image through image 3D matrix processing, filtering, image block processing, and block-by-block averaging of structural depth. Chinese invention patent (publication number: CN118209350A) discloses a concrete multi-point sampling machine and method. This patent achieves sampling at different locations in the concrete by adjusting and controlling the distance between the first and second sampling mechanisms, enabling research on structures at different depths. Chinese invention patent (publication number: CN109444176A) discloses a method for detecting the depth of voids in concrete under a steel shell. This patent obtains the void depth of the voided area by inputting the thermal neutron count rate corresponding to the voided area into a determined void depth calibration curve. It can be seen that the above-mentioned concrete depth sampling and detection methods are complex to operate, difficult to process data, and cannot achieve quantitative analysis of the improvement of concrete surface depth by permeable template fabric. Summary of the Invention

[0004] To address the quantitative problem of how permeable formwork fabric improves the effective depth of concrete, this invention proposes a method for determining the effective depth of permeable formwork fabric in concrete based on the fractal dimension of the pores.

[0005] The technical solution adopted in this invention is as follows: A method for determining the effective depth of concrete using permeable formwork based on the fractal dimension of pores includes the following steps: Step 1: Prepare two identical concrete sample molding molds. One mold is not covered with permeable template fabric and serves as the control group; the other mold has permeable template fabric covered on one side inside and serves as the experimental group. Step 2: Put the concrete raw materials into the mixer and mix them. Pour the well-mixed concrete slurry into the mold from Step 1, and remove it after curing. Step 3: Cut the concrete along the center line perpendicular to the permeable formwork, and then put it in an oven to keep the cut surface of the concrete dry. Step 4: First, apply ink to the cut surface of the sample obtained in Step 3. After the ink dries naturally, fill the surface pores with microsilica powder to enhance the visibility of the pores on the concrete cut surface. Step 5: Take photos of the concrete cut surface from Step 4 using a high-definition camera; Step 6: Binarize the photo from Step 5, then starting from the concrete surface where the permeable template cloth is pasted, cut out an area of ​​a certain width and calculate the fractal dimension of the holes in that area. Then drag the area without interval to the other side of the concrete to obtain the continuous fractal dimension of the holes in the entire concrete cut surface. Step 7: Plot the pore fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in Step 6, and determine the coordinates of the region where the pore fractal dimension curve of the experimental group concrete first intersects the curve of the control group. The final value of the coordinates of this region is the surface depth h of the concrete improved by the permeable template cloth.

[0006] In step one, the dimensions of the concrete sample forming mold, including length, width, and height, should not be less than 100 mm; preferably, the length, width, and height should be controlled within the range of 100 mm to 150 mm. This size range ensures that the permeable template cloth can function effectively while also ensuring that the sample is easy to cut.

[0007] In step two, the concrete raw materials include cementitious materials, aggregates, admixtures, etc. This invention is applicable to common concretes in the field, and the concrete formula can be adjusted according to various factors such as project needs, material costs, and the availability of local materials.

[0008] In step three, the height of the concrete cut surface should be no less than half the height of the concrete sample, and the width should be no less than 40 mm.

[0009] In step three, the oven temperature range is 40℃~60℃, and the drying time is 6~12 hours. A further preferred oven temperature is 50℃, and the drying time is 6 hours.

[0010] In step four, black ink should be used, with an ink concentration controlled at 70% to 80%; the particle size range of the microsilica powder is 0.1 to 0.3 μm.

[0011] In step six, the height of the selected area should be consistent with the height of the concrete cut surface, and the width of the area should be between 1 and 5 mm to ensure the continuity and accuracy of the hole fractal dimension calculation; the hole fractal dimension is the fractal dimension of the hole structure in the area.

[0012] The photo binarization process in step six is ​​as follows: the photo is binarized using the OTSU method.

[0013] The method for calculating the fractal dimension of the aperture region described in step six is ​​one of the following: the double blanket covering method, the fractional Brownian random field model method, or the box dimension method.

[0014] In step seven, the fractal dimension curve of the hole is plotted with the depth of the concrete cutting surface as the horizontal axis and the fractal dimension as the vertical axis.

[0015] Beneficial effects

[0016] This invention discloses a method for determining the effective depth of permeable formwork fabric in improving concrete surface quality based on pore fractal dimension. First, the concrete is cut along a line perpendicular to the centerline of the permeable formwork fabric. The porosity of the cut surface is enhanced by applying ink and microsilica powder, and photographs are taken. A curve showing the change of pore fractal dimension of the concrete cut surface with depth is plotted. By comparing this curve with the pore fractal dimension curve of a cut surface without permeable formwork fabric, the effective depth of the permeable formwork fabric in improving the concrete surface quality is determined. Compared to traditional measurement methods, this invention offers advantages such as convenient testing, high identification accuracy, and quantitative analysis, providing a new method for evaluating the depth of permeable formwork fabric in improving the concrete surface quality. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram illustrating the method of attaching permeable template fabric. Figure 3 Images of ink and silica powder applied to a concrete cut surface; Figure 4 A binarized image of a concrete cut surface; Figure 5 A schematic diagram for calculating the fractal dimension of a hole; Figure 6 This is a graph showing the variation of the fractal dimension of the aperture with distance over a given region. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0019] Example 1

[0020] This embodiment provides a method for determining the effective depth of concrete using permeable formwork based on the fractal dimension of the pores. The steps for using this method are described below: Step 1: Prepare two identical concrete sample molding molds. One mold is not covered with permeable template fabric and serves as the control group; the other mold has permeable template fabric covered on one side inside and serves as the experimental group. Step 2: Put the concrete raw materials into the mixer and mix them. Pour the well-mixed concrete slurry into the mold from Step 1 and remove it after curing for 3 days. Step 3: Cut the concrete along the centerline perpendicular to the permeable formwork, and then place it in a 50°C oven for 6 hours to keep the cut surface of the concrete dry. Step 4: First, apply ink to the cut surface of the sample obtained in Step 3. After the ink dries naturally, fill the surface pores with microsilica powder to enhance the visibility of the pores on the concrete cut surface. Step 5: Take photos of the concrete cut surface from Step 4 using a high-definition camera; Step 6: Binarize the photo from Step 5, then starting from the concrete surface where the permeable template cloth is pasted, cut out an area of ​​a certain width and calculate the fractal dimension of the holes in that area. Then drag the area without interval to the other side of the concrete to obtain the continuous fractal dimension of the holes in the entire concrete cut surface. Step 7: Plot the pore fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in Step 6, and determine the coordinates of the region where the pore fractal dimension curve of the experimental group concrete first intersects the curve of the control group. The final value of the coordinates of this region is the surface depth h of the concrete improved by the permeable template cloth.

[0021] The dimensions of the concrete sample molding mold in step one, including length, width, and height, shall not be less than 100 mm.

[0022] In step three, the height of the concrete cut surface should be no less than half the height of the specimen, and the width should be no less than 40mm.

[0023] In step four, black ink should be used, with an ink concentration controlled at 70% to 80%; the particle size range of the microsilica powder is 0.1 to 0.3 μm.

[0024] In step six, the height of the selected area should be consistent with the height of the cutting surface, and the width should be controlled between 1 and 5 mm.

[0025] In step six, the image is binarized using the OTU method; the box counting method is used to calculate the fractal dimension of the holes. First, different scale parameters (box side length) r are set, and the number of boxes containing at least one hole N(r) under different r is calculated; then, the logarithm of different r and N(r) is taken to obtain a set of points (log(1 / r), logN(r)); finally, linear regression is performed on these points, and the slope of the fitted line is the fractal dimension; the scale parameter is controlled between 0.01μm and 10000μm.

[0026] Example 2

[0027] This embodiment uses the method in Embodiment 1 to determine the effective depth of the permeable template fabric to improve the concrete.

[0028] Step 1: Prepare two identical concrete sample molding molds, each 100×100×100mm in size; one mold without permeable template fabric serves as the control group. The other mold has permeable template fabric attached to one side inside, serving as the experimental group. Figure 2 As shown.

[0029] Step 2: In this embodiment, the concrete raw materials include cementitious materials, aggregates, and admixtures. The cementitious materials are medium-heat cement and Class II fly ash (F grade), and the aggregates are artificial sand with a maximum particle size of 5mm. The ratio of cement:fly ash:water:aggregate:water-reducing agent:air-entraining agent = 53:18:10:132:1:8 is added to a mixer and mixed. The uniformly mixed concrete slurry is then poured into the mold from Step 1 and cured for 3 days before being removed.

[0030] Step 3: Cut the concrete along the centerline perpendicular to the permeable template fabric. The height of the concrete cut surface is 50mm, and the cutting depth (i.e., the width of the cut surface) is 40mm. Then, place it in a 50℃ oven for 6 hours to keep the concrete cut surface dry.

[0031] Step 4: Apply 80% black ink to the cut surface of the sample obtained in Step 3. After the ink dries naturally, fill the surface pores with SF90 micro silica powder with a particle size of 0.2μm to enhance the visibility of the pores on the concrete cut surface. Figure 3 As shown.

[0032] Step 5: Take photos of the concrete cut surface from Step 5 using a high-definition camera (ORDRO type).

[0033] Step Six: Binarize the photo from Step Five using the OTU method, such as... Figure 4 As shown, after selecting a threshold of 180~200, starting from the concrete surface where the permeable template fabric is pasted, a region with a height of 50mm and a width of 5mm is cut out. Then, the box counting method is used to calculate the fractal dimension of the holes. The scale parameter (box side length) r is set to range from 0.1μm to 2000μm, and the number of boxes containing at least one hole N(r) under different r is calculated. Then, the logarithm of different r and N(r) is taken to obtain a set of points (log(1 / r), logN(r)). Finally, linear regression is performed on these points, and the slope of the fitted line is the fractal dimension. Then, the region is dragged without interval to the other side of the concrete to obtain the fractal dimension of the holes on the entire concrete cut surface, as shown. Figure 5 As shown.

[0034] Step 7: Plot the pore fractal dimension curves of the two types of concrete sample cut surfaces obtained in Step 6, and determine the region where the pore fractal dimension of the experimental group concrete intersects with that of the control group concrete, such as... Figure 6 As shown. By Figure 6 It can be seen that the final value of the region coordinates of the first intersection point between the pore fractal dimension of the experimental group and the control group is 20mm, so the improvement depth of the permeable template cloth in the experimental group is 20mm.

Claims

1. A method for determining the effective depth of concrete using permeable template fabric based on the fractal dimension of the pores, characterized in that, Includes the following steps: Step 1: Prepare two identical concrete sample molding molds. One mold is not covered with permeable template fabric and serves as the control group; the other mold has permeable template fabric covered on one side inside and serves as the experimental group. Step 2: Put the concrete raw materials into the mixer and mix them. Pour the well-mixed concrete slurry into the mold from Step 1, and remove it after curing. Step 3: Cut the concrete along the center line perpendicular to the permeable formwork, and then put it in an oven to keep the cut surface of the concrete dry. Step 4: First, apply 80% black ink to the cut surface of the sample obtained in Step 3. After the ink dries naturally, fill the surface pores with SF90 micro silica powder with a particle size of 0.2 μm to enhance the recognition of the pores on the concrete cut surface. Step 5: Take photos of the concrete cut surface from Step 4 using a high-definition camera; Step Six: Binarize the photos from Step Five, selecting a binarization threshold of 180-200. Then, starting from the concrete surface where the permeable template fabric is pasted, cut out a region of a certain width and calculate the fractal dimension of the holes in that region using the box counting method. The box counting method is as follows: set the box side length r to a range of 0.1 μm-2000 μm, calculate the number N(r) of boxes containing at least one hole under different box side lengths r, and perform linear regression fitting on log(1 / r) and logN(r). The slope of the fitted line is the fractal dimension of the holes in that region. Subsequently, move the calculation region along the concrete depth direction to the other side of the concrete without interval, and calculate the fractal dimension of the holes in each calculation region in turn, thereby obtaining the continuous fractal dimension of the holes in the entire concrete cut surface. Step 7: Plot the pore fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in Step 6, and determine the coordinates of the region where the pore fractal dimension curve of the experimental group concrete first intersects the curve of the control group. The final value of the coordinates of this region is the surface depth h of the concrete improved by the permeable template cloth. In step six, the height of the selected area is consistent with the height of the cut surface, and the width of the area is between 1 and 5 mm.

2. The method for determining the effective depth of concrete based on the fractal dimension of the pores using permeable template fabric, as described in claim 1, is characterized in that: The dimensions of the concrete sample molding mold in step one, including length, width, and height, shall not be less than 100 mm.

3. The method for determining the effective depth of concrete based on the fractal dimension of the pores using permeable template fabric, as described in claim 1, is characterized in that: In step three, the height of the cut surface should be no less than half the height of the concrete sample, and the width should be no less than 40mm.

4. The method for determining the effective depth of concrete based on the fractal dimension of the pores using permeable template fabric, as described in claim 1, is characterized in that: In step three, the oven temperature is controlled at 40℃~60℃, and the drying time is 6~12 hours.

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