CN-116678714-B - Sliding formwork spreading concrete slidability assessment method based on digital image processing technology

Abstract

The invention relates to a slip form spreading concrete slidability assessment method based on a digital image processing technology, which belongs to the technical field of road engineering and comprises the steps of completing a molding experiment according to a mixing ratio of concrete, namely molding a concrete test piece in a cube mold, starting shooting after concrete slump is finished after demolding, sequentially shooting images of four sides of the molded concrete test piece by using a camera during shooting, respectively processing the obtained images of the four sides, including image preprocessing to obtain a concrete part in the image, then graying the preprocessed image by using MATLAB, calculating void size, void ratio, slump value and uniformity index of each side image, and quantitatively analyzing the slidability of the concrete under the mixing ratio. The invention changes the traditional qualitative analysis through naked eye observation into quantitative analysis and provides an evaluation index, thereby being capable of quickly and accurately quantifying the state of sliding form spreading concrete so as to guide actual construction.

Inventors

• LING YIFENG
• TanTai Wenyao
• Peng Juzhi
• SUN YANBING
• MA CHUANYI
• ZHANG HONGZHI
• GE ZHI
• ZHANG NING
• Dou Liuyang
• BAI YUANXIN
• LI JIAQI

Assignees

• 山东大学
• 山东高速集团有限公司

Dates

Publication Date

20260512

Application Date

20230606

Claims (6)

1. 1. The method for evaluating the sliding formwork paving concrete slidability based on the digital image processing technology is characterized by comprising the following steps of: (1) Forming experiments are completed according to the mixing proportion of concrete, namely, concrete test pieces are formed in a cube mould, wherein the size of the cube mould is 300mm by 300mm; (2) Shooting can be started after demoulding and concrete slump is finished, and the camera is used for moving during shooting, so that images of four sides of a formed concrete test piece are sequentially shot; (3) Respectively processing the obtained images of the four sides, including image preprocessing to obtain a concrete part in the image, and then graying and binarizing the preprocessed image by utilizing MATLAB; (4) Calculating the void size, void ratio, collapse value and uniformity index of each side image, and quantitatively analyzing the slidability of the concrete in the mixing ratio; In the step (4): The process of calculating the void size is: Defining void diameter in MATLAB I.e. Respectively defining large gaps, medium gaps and small gaps, and respectively counting the number of the gaps of each grade; when a large gap with a gap diameter of 30mm or more appears, the slidability is directly judged to be unqualified; when the number of gaps with the diameters of 10-30 mm accounts for more than 15% of the total number of the gaps, the concrete is unqualified in slidability; The other conditions are regarded as qualified in slidability under the gap size index; The process of calculating the void fraction is as follows: Void fraction The calculation formula is that Wherein the void area is the void area, which is the void fraction The concrete is unqualified in terms of slidability when the void ratio When the concrete is in a slip condition under the void ratio index of the concrete; the process of calculating the collapse value is as follows: The collapse values include a top collapse value, defined as the vertical distance from the initial tip at the widest point of the top collapse, recorded as The bottom collapse value is defined as the vertical distance from the initial side edge at the widest point of the bottom after collapse, and is recorded as Measuring the initial height and width of the concrete test piece, the height and width after slump and the slump value by using MATLAB The calculation formula of (2) is as follows: Bottom collapse value: top collapse value: Taking out 、 Maximum value of (2) as a collapse value When the value of the collapse is When the concrete is not qualified in slip, when the concrete collapses When the concrete collapse value index is used, the slidability is qualified; the process of calculating uniformity is: dividing the whole image into 9 regions equally in the length and width directions, and obtaining the void ratio of each region And porosity of The calculation modes of (1) are consistent, and the void ratio in 9 areas To characterize the uniformity of the concrete over the entire picture, defining uniformity coefficients The calculation process is as follows: void fraction of 9 regions Wherein, the Represents the void fraction of the jth region, j is an integer of 1 to 9, Representation of Is selected from the group consisting of a maximum value of (c), Representation of Is the minimum value of (a); Uniformity coefficient The method comprises the following steps: When uniformity coefficient When the concrete is unqualified in slidability, the concrete is characterized by a uniformity coefficient When the slip is less than or equal to 30%, the slip is qualified under the uniformity index of the concrete; when the slidability of the concrete is qualified under a single index, carrying out overall comprehensive evaluation on the slidability of the concrete, and defining: Representing void diameter on a single side When the maximum value of (1) A is a score of 10; A score of 6; score A is 4; Void fraction Score B is 10, void fraction A score B of 6; value of sloughing Score C is 10, collapse value A score of 6; Uniformity coefficient Score D is 10, uniformity coefficient A score D of 6; Calculating concrete mass for single side The calculation formula is as follows: wherein 0.2 and 0.4 are importance coefficients, and represent the influence degree of the index on the sliding property of the sliding-mode paving concrete; Represent the first A, B, C, D respectively representing scores corresponding to the size of the gap, the void ratio, the collapse value and the uniformity; And (3) evaluating the slidability level of the whole concrete, namely solving the mass average of the concrete with four faces, wherein the calculation formula is as follows: When (when) When the concrete sample is more than or equal to 9, the grade of the concrete sample is better; at that time 6 is less than or equal to <9, When the concrete test piece grade is qualified And (6) the grade of the concrete test piece is unqualified.
2. 2. The method for evaluating the slidability of sliding form paving concrete based on a digital image processing technology as claimed in claim 1, wherein in the step (1), the cube mold consists of two equilateral L-shaped metal plates, a bottom plate and a rubber sleeve, and the concrete is mixed by being provided with a vibrating rod with the frequency of 12500r/min.
3. 3. The method for evaluating the slidability of sliding form paving concrete based on a digital image processing technology according to claim 1, wherein in the step (2), shooting is realized by means of a positioning image acquisition device, the positioning image acquisition device comprises a circular metal bottom plate positioned at the bottom, a groove is arranged at the center of the circular metal bottom plate, and the size of the groove is matched with that of a cube mold for placing the cube mold; The circular metal bottom plate is provided with an annular slide rail surrounding the groove, the annular slide rail, the groove and the center of the circular metal bottom plate are overlapped, the camera is fixed on the sliding block, and the sliding block can drive the camera to slide on the annular sliding rail.
4. 4. The method for evaluating the sliding formwork paving concrete slidability based on the digital image processing technology as claimed in claim 3, wherein positioning devices are arranged on the annular sliding rail at positions opposite to four side surfaces of the formed concrete test piece and used for positioning the sliding blocks; The middle part of the annular sliding rail is provided with a strip-shaped sliding groove, the section of the sliding groove is in a convex shape, the upper part of the sliding groove is narrow, the lower part of the sliding groove is wide, the bottom of the sliding block is provided with a convex strip matched with the sliding groove, and the convex strip is embedded into the strip-shaped sliding groove to realize sliding fit; the locating device comprises four locating pieces, the two locating pieces are respectively located on two sides of the sliding block and used for accurately locating the position of the sliding block, one end of each locating piece is hinged to one side of the annular sliding rail, the other end of each locating piece can rotate freely, a limiting block is arranged on each locating piece, and when the locating pieces rotate and are buckled on the annular sliding rail, the limiting blocks are just located in the sliding grooves to achieve locating of the sliding block.
5. 5. The method for evaluating the sliding formwork paving concrete slidability based on the digital image processing technology as claimed in claim 1, wherein in the step (2), when the images of four sides of the formed concrete test piece are shot, the distances between the cameras and the test sides are equal, and are 50cm; Before formal photographing, camera parameters, focus, exposure and pixels, are set.
6. 6. The method for evaluating slip form paving concrete slidability based on a digital image processing technology according to claim 1, wherein in the step (3), image preprocessing is performed by using ps software to extract a concrete part, then an image is subjected to gray scale processing and image partitioning by using MATLAB, a region with a gray scale value of 0 to 100 is a void region, a value is defined as 0, a gray scale value of 101 to 255 is a flat region, and a value is defined as 1.

Description

Sliding formwork spreading concrete slidability assessment method based on digital image processing technology Technical Field The invention relates to a sliding mode paving concrete slidability evaluation method based on a digital image processing technology, and belongs to the technical field of road engineering. Background The slipform paving is a construction process for paving a concrete pavement by adopting a slipform paver, and can finish the functions of cloth paving, vibrating compaction, extrusion forming, plastering finishing and the like at one time because an edge fixing template is not required to be erected, and the slipform paving has the advantages of good construction continuity, fast progress, high efficiency and the like, and is a common construction process in modern road construction. The concrete suitable for slipform paving should have good slidability (uniformity, formwork erection and other construction performances), so the design choice of the mixing ratio is very important. In practical engineering, it is very necessary to evaluate the slidability of fresh concrete. However, the existing specifications generally only adopt slump as an evaluation index of the working performance of the slip form spread concrete, and neglect the influence of vibration on the slip form spread concrete and important slip indexes such as uniformity, formwork erection and the like. At present, a rapid and effective test and evaluation method for the slidability is not available. The digital image processing technology has the advantages of high processing precision, strong comprehensiveness and the like, and is a common analysis method in engineering analysis. Therefore, it is necessary to propose an evaluation method for analyzing the slidability of slip-form paving concrete based on a digital image processing technique. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a slip form paving concrete slip property evaluation method based on a digital image processing technology, which is changed from traditional qualitative analysis through naked eye observation to quantitative analysis and provides evaluation indexes, so that the condition of slip form paving concrete can be rapidly and accurately quantified to guide actual construction. The invention adopts the following technical scheme: A slip form paving concrete slidability assessment method based on a digital image processing technology comprises the following steps: (1) Completing a molding experiment according to the mixing proportion of the concrete, namely molding a concrete test piece in a cube mold; (2) Shooting can be started after demoulding and concrete slump is finished, and the camera is used for moving during shooting, so that images of four sides of a formed concrete test piece are sequentially shot; (3) Respectively processing the obtained images of the four sides, including image preprocessing to obtain a concrete part in the image, and then graying and binarizing the preprocessed image by utilizing MATLAB; (4) And calculating the void size, void ratio, collapse value and uniformity index of each side image, and quantitatively analyzing the slidability of the concrete in the mixing ratio. Preferably, in the step (1), the concrete of the invention is newly mixed concrete, the size of the cube mould is 300 x 300mm, the concrete is formed by two equilateral L-shaped metal plates, a bottom plate and a rubber sleeve, no top cover exists, the two L-shaped metal plates and the bottom plate are combined together, and the outer side is fixed by the rubber sleeve, so that the concrete is formed. In order to reduce the gaps in the pouring process and improve the compactness of concrete, a vibrating rod is arranged when the concrete is mixed, and the frequency is 12500r/min. The process of casting concrete into a cube mold is referred to as a "molding test". The concrete process of the molding test comprises the steps of assembling a mold, sleeving a rubber sleeve on the outside, mixing concrete according to a pre-designed mixing ratio, brushing oil on the inner side of the mold so as to facilitate demolding, pouring the mixed concrete into the mold, quickly inserting a vibrating rod into the middle lower part of the concrete, vibrating for 20-30 seconds, slowly taking out the concrete after vibrating, wherein the distance between the height of the concrete and the top surface is not more than 5cm, taking down the rubber sleeve, taking down two L-shaped metal plates vertically upwards, and avoiding disturbance to the side surfaces as much as possible in the demolding process, thereby obtaining the required test piece. Preferably, in the step (2), in order to quickly and conveniently collect the surface image of the concrete, shooting is realized by means of a positioning image collecting device, wherein the positioning image collecting device comprises a circular metal bottom plate positioned at the bottom,