Method for determining effective depth of permeable formwork cloth for improving concrete based on hole fractal dimension

Abstract

The invention discloses a method for determining permeable template cloth to improve effective depth of concrete based on hole fractal dimension, which comprises the following steps of: firstly, cutting the concrete along a middle line perpendicular to the permeable template cloth, enhancing the hole recognition degree of a cutting surface by a method of painting ink and silica fume, and photographing; and drawing a curve of the hole fractal dimension of the concrete cutting surface changing along with the depth, and comparing the curve with the hole fractal dimension curve of the cutting surface which is not pasted with the water-permeable template cloth to determine the effective depth of the water-permeable template cloth for improving the concrete surface. Compared with a traditional measuring method, the method has the advantages of being convenient to test, high in recognition precision and capable of achieving quantitative analysis, and a new method is provided for evaluating the concrete surface depth improved by the permeable formwork cloth.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete surface improvement effect evaluation, and in particular relates to a method for determining the effective depth of concrete improved by a permeable template cloth based on pore fractal dimension. Background Art

[0002] During the vibration and curing process, large-volume concrete is prone to form defects such as holes and rough surfaces on the surface, which affects the appearance quality and durability of the concrete. The use of permeable formwork cloth can effectively improve the surface quality of concrete. However, the improvement effects of different permeable formwork cloths on the concrete surface vary greatly. Previous studies often evaluated the improvement effect by surface morphology characteristics, ignoring the quantification of the depth of concrete improvement by permeable formwork cloth. The improvement depth is crucial to improving the durability of concrete, and new testing methods are urgently needed.

[0003] In order to accurately identify the structures at different depths inside the concrete, a Chinese invention patent (authorization announcement number: CN103114514B) discloses a cement concrete pavement groove structure depth detection algorithm. The patent obtains the structure depth value of the image through image three-dimensional matrix, filtering processing, image block processing and block-by-block average structure depth; a Chinese invention patent (publication number: CN118209350A) discloses a concrete multi-point sampling machine and method. The patent adjusts and controls the spacing between the first sampling mechanism and the second sampling mechanism to achieve sampling at different positions of the concrete and research on structures at different depths; a Chinese invention patent (publication number: CN109444176A) discloses a method for detecting the void depth of concrete under a steel shell. The patent brings the thermal neutron count rate corresponding to the void area into the determined void depth calibration curve to obtain the void depth of the void area. It can be seen that the above-mentioned patents of concrete depth sampling and detection methods are complicated to operate, the data processing process is difficult, and at the same time, it is impossible to achieve quantitative analysis of the depth of the concrete surface improved by the permeable template cloth. Summary of the invention

[0004] In order to solve the quantitative problem of the effective depth of concrete improved by permeable formwork cloth, the present invention proposes a method for determining the effective depth of concrete improved by permeable formwork cloth based on the fractal dimension of the holes.

[0005] The technical solution adopted by the present invention is as follows: A method for determining the effective depth of concrete improved by permeable formwork cloth based on pore fractal dimension comprises the following steps: Step 1: prepare two identical concrete sample forming molds, one without a permeable formwork cloth as a control group; the other with a permeable formwork cloth pasted on one side of the mold as an experimental group; Step 2: Put the concrete raw materials into a mixer and mix them together, pour the evenly mixed concrete slurry into the mold of step 1, and take it out after curing; Step 3: Cut the concrete along the center line perpendicular to the permeable formwork cloth, and then put it into the oven to keep the cut surface of the concrete dry; Step 4: The cut surface of the sample obtained in step 3 is first treated with ink, and after the ink is naturally air-dried, microsilica powder is filled into the surface holes to enhance the recognition of the holes on the cut surface of the concrete; Step 5: Use a high-definition camera to take a photo of the concrete cutting surface in step 4; Step 6: Binarize the photo in step 5, and then cut off a certain width of the area from the surface of the concrete on which the permeable formwork cloth is pasted, calculate the hole fractal dimension of the area, and then drag the area to the other side of the concrete without intervals, so as to obtain the continuous hole fractal dimension of the entire concrete cut surface; Step 7: Draw the hole fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in step 6, determine the regional coordinates of the first intersection point of the hole fractal dimension curve of the experimental group concrete and the control group curve, and the final value of the regional coordinates is the surface depth h of the concrete improved by the permeable formwork cloth.

[0006] The length, width and height of the concrete sample forming mold in step one are not less than 100 mm; preferably, the length, width and height range are controlled between 100 mm and 150 mm. This size range can ensure that the permeable template cloth can play a role and that the sample is easy to cut.

[0007] The concrete raw materials in step 2 include cementitious materials, aggregates, admixtures, etc. The present invention is applicable to common concrete in the field, and the concrete formula is adjusted according to various factors such as engineering needs, material costs and availability of local materials.

[0008] The height of the concrete cutting surface in step 3 shall not be less than half the height of the concrete sample, and the width shall not be less than 40 mm.

[0009] In step 3, the oven temperature ranges from 40°C to 60°C, and the drying time is 6 to 12 hours. A further preferred oven temperature is 50°C, and the drying time is 6 hours.

[0010] In step 4, black ink should be used, and the ink concentration should be controlled at 70%~80%; the particle size range of microsilica powder is 0.1~0.3μm.

[0011] The height of the area selected in step 6 is consistent with the height of the concrete cutting surface, and the width of the area is between 1 and 5 mm to ensure the continuity and accuracy of the calculation of the pore fractal dimension; the pore fractal dimension is the fractal dimension of the regional pore structure.

[0012] The method for binarizing the photo in step six is: binarizing the photo using the OTSU method.

[0013] The method for calculating the regional hole fractal dimension described in step six is ​​a method of double blanket covering, a method based on a fractional Brownian random field model, or a box dimension method.

[0014] The hole fractal dimension curve drawn in step seven is drawn with the depth of the concrete cutting surface as the horizontal coordinate and the fractal dimension as the vertical coordinate.

[0015] Beneficial Effects

[0016] The present invention discloses a method for determining the effective depth of concrete improved by permeable formwork cloth based on the pore fractal dimension. First, the concrete is cut along the center line perpendicular to the permeable formwork cloth, the pore recognition of the cut surface is enhanced by brushing ink and microsilica powder, and a photo is taken. A curve of the pore fractal dimension of the concrete cut surface changing with depth is drawn, and the effective depth of the concrete surface improved by the permeable formwork cloth is determined by comparing it with the pore fractal dimension curve of the cut surface without the permeable formwork cloth. Compared with the traditional measurement method, the present invention has the advantages of convenient testing, high recognition accuracy, and quantitative analysis, and provides a new method for evaluating the depth of concrete surface improved by the permeable formwork cloth. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the present invention; Figure 2 This is a schematic diagram of the pasting method of the permeable template cloth; Figure 3 Pictures of applying ink and microsilica powder to cut concrete surfaces; Figure 4 Binarized image of the concrete cut surface; Figure 5 This is a schematic diagram of hole fractal dimension calculation; Figure 6 This is a graph showing the variation of the hole fractal dimension with the distance area. DETAILED DESCRIPTION

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

[0019] Example 1

[0020] This embodiment provides a method for determining the effective depth of concrete improved by permeable formwork cloth based on the fractal dimension of the holes. The steps of using this method are described below: Step 1: prepare two identical concrete sample forming molds, one without a permeable formwork cloth as a control group; the other with a permeable formwork cloth pasted on one side of the mold as an experimental group; Step 2: Put the concrete raw materials into a mixer and mix them together, pour the evenly mixed concrete slurry into the mold of step 1, and take it out after curing for 3 days; Step 3: Cut the concrete along the center line perpendicular to the permeable formwork cloth, and then put it in a 50°C oven for 6 hours to keep the cut surface of the concrete dry; Step 4: The cut surface of the sample obtained in step 3 is first treated with ink, and after the ink is naturally air-dried, microsilica powder is filled into the surface holes to enhance the recognition of the holes on the cut surface of the concrete; Step 5: Use a high-definition camera to take a photo of the concrete cutting surface in step 4; Step 6: Binarize the photo in step 5, and then cut off a certain width of the area from the surface of the concrete on which the permeable formwork cloth is pasted, calculate the hole fractal dimension of the area, and then drag the area to the other side of the concrete without intervals, so as to obtain the continuous hole fractal dimension of the entire concrete cut surface; Step 7: Draw the hole fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in step 6, determine the regional coordinates of the first intersection point of the hole fractal dimension curve of the experimental group concrete and the control group curve, and the final value of the regional coordinates is the surface depth h of the concrete improved by the permeable formwork cloth.

[0021] The length, width and height of the concrete sample forming mold in step 1 shall not be less than 100 mm.

[0022] The height of the concrete cutting surface in step 3 shall not be less than half of the specimen height, and the width shall not be less than 40 mm.

[0023] In step 4, black ink should be used, and the ink concentration should be controlled at 70%~80%; the particle size range of microsilica powder is 0.1~0.3μm.

[0024] The height of the area selected in step 6 should be consistent with the height of the cutting surface, and the width should be controlled within 1~5mm.

[0025] In step 6, the photos are binarized by the OSTU method; the box counting method is used to calculate the fractal dimension of the holes. First, different scale parameters (box side lengths) 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, these points are linearly regressed and fitted, and the slope of the fitting line is the fractal dimension; the scale parameter is controlled between 0.01μm and 10000μm.

[0026] Example 2

[0027] This example uses the method in Example 1 to determine the effective depth of concrete improved by the permeable formwork cloth.

[0028] Step 1: Prepare two identical concrete sample forming molds with dimensions of 100×100×100mm; one is not pasted with a permeable template cloth, which serves as the control group. The other is pasted with a permeable template cloth on one side of the mold, which serves as the experimental group. Figure 2 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 F II fly ash. The aggregate is artificial sand with a maximum aggregate particle size of 5 mm. Cement: fly ash: water: aggregate: water reducer: air entraining agent = 53:18:10:132:1:8 are put into a mixer in a mass ratio for stirring. The evenly stirred concrete slurry is poured into the mold of step 1 and taken out after curing for 3 days.

[0030] Step 3: Cut the concrete along the center line perpendicular to the permeable formwork cloth. The height of the concrete cutting surface is 50mm, and the cutting depth, i.e. the cutting surface width, is 40mm. Then put it in an oven at 50℃ for 6 hours to keep the concrete cutting surface dry.

[0031] Step 4: Paint the cut surface of the sample obtained in step 3 with 80% black ink. After the ink dries naturally, fill the surface holes with SF90 microsilica powder with a particle size of 0.2 μm to enhance the recognition of the holes on the cut surface of the concrete. Figure 3 shown.

[0032] Step 5. Use a high-definition camera (ORDRO model) to take a photo of the concrete cutting surface in step 5.

[0033] Step 6: Binarize the photo in step 5 using the OSTU method. Figure 4 As shown in the figure, after selecting a threshold of 180~200, starting from the surface of one side of the concrete where the permeable formwork cloth is pasted, an area with a height of 50mm and a width of 5mm is intercepted, and then the box counting method is used to calculate the fractal dimension of the hole. The scale parameter (box side length) r is set in the range of 0.1μm~2000μm, and the number of boxes N(r) containing at least one hole 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, a linear regression fit is performed on these points, and the slope of the fitting line is the fractal dimension. Then drag the area to the other side of the concrete without interval to obtain the fractal dimension of the holes on the entire concrete cut surface, as shown in Figure 5 shown.

[0034] Step 7: Draw the hole fractal dimension curves of the cut surfaces of the two concrete samples obtained in step 6, and determine the area where the fractal dimension of the holes in the experimental group concrete intersects with the fractal dimension of the holes in the contrast group concrete, such as Figure 6 As shown. Figure 6 It can be seen that the final value of the regional coordinates of the initial intersection point of the hole fractal dimension of the experimental group and the control group is 20mm, so the improvement depth of the permeable template cloth of the experimental group is 20mm.

Claims

1. A method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension, characterized in that: The following steps are involved: Step 1: prepare two identical concrete sample forming molds, one without a permeable formwork cloth as a control group; the other with a permeable formwork cloth pasted on one side of the mold as an experimental group; Step 2: Put the concrete raw materials into a mixer and mix them together, pour the evenly mixed concrete slurry into the mold of step 1, and take it out after curing; Step 3: Cut the concrete along the center line perpendicular to the permeable formwork cloth, and then put it into the oven to keep the cut surface of the concrete dry; Step 4: The cut surface of the sample obtained in step 3 is first treated with ink, and after the ink is naturally air-dried, microsilica powder is filled into the surface holes to enhance the recognition of the holes on the cut surface of the concrete; Step 5: Use a high-definition camera to take a photo of the concrete cutting surface in step 4; Step 6: Binarize the photo in step 5, and then cut off a certain width of the area from the surface of the concrete on which the permeable formwork cloth is pasted, calculate the hole fractal dimension of the area, and then drag the area to the other side of the concrete without intervals, so as to obtain the continuous hole fractal dimension of the entire concrete cut surface; Step 7: Draw the hole fractal dimension curves of the cut surfaces of the control group and experimental group concrete samples obtained in step 6, determine the regional coordinates of the first intersection point of the hole fractal dimension curve of the experimental group concrete and the control group curve, and the final value of the regional coordinates is the surface depth h of the concrete improved by the permeable formwork cloth.

2. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: The length, width and height of the concrete sample forming mold in step 1 shall not be less than 100 mm.

3. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: In step 3, the height of the cutting surface shall not be less than half of the height of the concrete sample, and the width shall not be less than 40 mm.

4. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: In step 3, the oven temperature is controlled at 40°C to 60°C and dried for 6 to 12 hours.

5. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: In step 4, black ink should be used, and the ink concentration should be controlled at 70%~80%.

6. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: The particle size range of the microsilica powder in step 4 is 0.1~0.3μm.

7. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: The size height of the area selected in step 6 is consistent with the height of the cutting surface, and the area width is between 1 and 5 mm.

8. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: The method for calculating the regional hole fractal dimension described in step six is ​​a method of double blanket covering, a method based on a fractional Brownian random field model, or a box dimension method.

9. The method for determining the effective depth of concrete improved by permeable formwork based on pore fractal dimension according to claim 1, characterized in that: In step six, the photo binarization processing method is to binarize the photo using the OTSU method.

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