Method for determining reasonable construction temperature of foamed asphalt semi-warm mixtures

Abstract

The application discloses a method for determining reasonable construction temperature of foamed asphalt semi-warm mixed material, and belongs to the technical field of asphalt mixture mixing. W The method is as follows: foamed asphalt semi-warm mixed material and hot-mixed asphalt mixture are prepared; area calculation indexes and interval calculation indexes of the foamed asphalt semi-warm mixed material and area calculation indexes and interval calculation indexes of the hot-mixed asphalt mixture are obtained; and and are respectively calculated; the reasonable mixing temperature interval of the foamed asphalt semi-warm mixed material is determined by comparing and W The foamed asphalt semi-warm mixed material is mixed at a set temperature near the median value of the reasonable mixing temperature interval of the foamed asphalt semi-warm mixed material; Marshall test pieces are prepared by using different molding temperatures and volume indexes are tested; and the reasonable compaction temperature interval of the foamed asphalt semi-warm mixed material is determined by combining the volume index requirements of the hot-mixed asphalt mixture. The application determines the reasonable mixing temperature and compaction temperature interval of the foamed asphalt semi-warm mixed material based on the asphalt coating property of aggregate surfaces and the void ratio of the mixed material.

Description

Technical Field

[0001] This invention belongs to the field of asphalt mixture mixing technology, specifically relating to a method for determining the reasonable construction temperature of foamed asphalt semi-warm mix. Background Technology

[0002] The mixing and compaction temperatures of semi-warm-mix asphalt mixtures are significantly lower than those of traditional hot-mix asphalt mixtures, typically controlling the temperature between 70℃ and 100℃ during production, paving, and compaction. Foamed asphalt semi-warm-mix technology is based on semi-warm-mix asphalt mixtures. After foaming, the viscosity of the asphalt rapidly decreases in a short time, allowing for the coating of aggregates at lower temperatures (below 100℃). This further reduces energy consumption, greenhouse gas emissions, and harmful gas emissions. Simultaneously, it reduces asphalt aging during production, improving the durability and service life of asphalt pavements. It has positive implications for long-distance transportation, low-temperature construction, and extended construction time.

[0003] However, in actual engineering projects, variations in the type and composition of the base asphalt and aggregates used will result in different construction temperatures at which foamed asphalt semi-warm mixes achieve optimal performance. Currently, the engineering application of foamed asphalt semi-warm mixes is limited, and there are no corresponding standards specifying the mixing and compaction temperatures for foamed asphalt semi-warm mixes. Furthermore, the method of determining the construction temperature based on the viscosity-temperature curve for hot-mix asphalt mixtures is not applicable to semi-warm mixes using foamed asphalt. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a method for determining the reasonable construction temperature of foamed asphalt semi-warm mix. By preparing foamed asphalt semi-warm mixes at different mixing temperatures, and based on area and interval calculation indices, a calculation formula is proposed to characterize the asphalt coating rate on the aggregate surface in the foamed asphalt semi-warm mix. Using the asphalt coating rate of aggregates in hot-mix asphalt mixtures obtained by the same method as a control group, the optimal mixing temperature range is selected through performance comparison of aggregate surface asphalt coating rate. Combined with the volume index requirements of hot-mix asphalt mixtures, the reasonable compaction temperature range of foamed asphalt semi-warm mixes is determined. This invention determines the reasonable mixing and compaction temperature ranges of foamed asphalt semi-warm mixes based on aggregate surface asphalt coating and mixture porosity, providing a scientific basis for high-quality construction and performance improvement of foamed asphalt semi-warm mixes.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for determining the appropriate construction temperature of foamed asphalt semi-warm mix, comprising the following steps: S1: Foamed asphalt is prepared from base asphalt, and then foamed asphalt and aggregate are mixed at a series of mixing temperatures to obtain foamed asphalt semi-warm mix; base asphalt and aggregate are mixed at a set mixing temperature to obtain hot mix asphalt. S2: Obtain the area calculation index and interval calculation index for foamed asphalt semi-warm mix and hot mix asphalt mixture, and calculate the asphalt coating rate on the aggregate surface in the foamed asphalt semi-warm mix at a series of mixing temperatures. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture at a set mixing temperature ; S3: Asphalt coating rate on aggregate surface in foamed asphalt semi-warm mix at comparative mixing temperatures. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture at a set mixing temperature Determine the reasonable mixing temperature range for foamed asphalt semi-warm mix. W ; S4: Within the reasonable mixing temperature range of foamed asphalt semi-warm mix. W Foamed asphalt semi-warm mix was prepared at a set temperature near the median value. Marshall specimens were made at different molding temperatures and the volume index was tested. Based on the volume index requirements of hot mix asphalt, the reasonable compaction temperature range of foamed asphalt semi-warm mix was determined.

[0006] In one embodiment, in S2, the process of obtaining the area calculation index and interval calculation index of foamed asphalt semi-warm mix asphalt and the area calculation index and interval calculation index of hot mix asphalt is as follows: S21: Obtain surface images of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture; S22: Perform inverse square inverse color transformation preprocessing on the surface images of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture to obtain the preprocessed images of the foamed asphalt semi-warm mix and / or the preprocessed images of the hot mix asphalt mixture. S23: Using Halcon software, the images of pre-processed foamed asphalt semi-warm mix and / or pre-processed hot mix asphalt mixture are processed. Based on the grayscale distribution histogram, a grayscale threshold in the range of 100-200 is selected. Global threshold segmentation is used to perform inverse binarization segmentation to obtain segmented images. In the segmented images, white areas represent aggregate areas not coated with asphalt, and black areas represent aggregate surfaces coated with asphalt. According to the area calculation index formula, the area index of each segmented image of a single sample is calculated, and the average value is taken as the area calculation index of each sample. S24: Use Python software to divide the pre-processed foamed asphalt semi-warm mix image and / or pre-processed hot mix asphalt image into gray levels. According to the interval calculation index formula, calculate the interval index of each pre-processed foamed asphalt semi-warm mix image and / or pre-processed hot mix asphalt image for a single sample, and take the average value as the interval calculation index for each sample.

[0007] In one embodiment, the formula for the inverse square color transformation preprocessing in S22 is as follows:

[0008] In the formula: x is the image pixel value (an integer from 0 to 255); x' is the pixel value after inverse square color transformation preprocessing; ε is a small constant to prevent division by zero, taken as 1e-6.

[0009] In one embodiment, the area calculation index formula is:

[0010] In the formula: For area calculation indicators; N w The total number of pixels in the white region of the segmented image; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0011] In one embodiment, the formula for calculating the interval index is:

[0012] In the formula: Indicators are calculated over an interval. α i For the first i The weights of each interval; N i For the first i The number of pixels in each interval; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0013] In one embodiment, in S21, the process of acquiring surface images of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture is as follows: Use a thermometer to measure the core temperature of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture. When the target mixing temperature is reached, fill the sample preparation bowl 4 with the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture and let it stand for a period of time to cool to room temperature. After cooling, the sample bowl 4 containing the foamed asphalt semi-warm mix and / or the hot mix asphalt is placed in the image capturing device, and the surface image of the foamed asphalt semi-warm mix and / or the hot mix asphalt is captured by the external photography device 1.

[0014] In one embodiment, in S24, the grayscale level division is specifically as follows: The grayscale value range of 0 to 255 is divided into 26 equal grayscale intervals. The lower the grayscale value, the more it represents the area where the aggregate is not coated with asphalt. Each grayscale interval is assigned a corresponding weight from 1 to 0 according to a linear decreasing rule, with the weight of the grayscale interval of 250 to 255 set to 0.

[0015] In one embodiment, in S2, the asphalt coating rate on the surface of the aggregates in the foamed asphalt semi-warm mix is... It is the arithmetic mean of the sum of the area calculation index and the interval calculation index of foamed asphalt semi-warm mix. In S2, the asphalt coating rate of the aggregate surface in the hot-mix asphalt mixture It is the arithmetic mean of the sum of the area calculation index and the interval calculation index of hot-mix asphalt mixture.

[0016] In one embodiment, in S3, the optimal mixing temperature range for the foamed asphalt semi-warm mix is... W To comply with ≤ The mixing temperature range of foamed asphalt semi-warm mix under certain conditions.

[0017] In one embodiment, in S4, the reasonable compaction temperature range of the foamed asphalt semi-warm mix is ​​the molding temperature range that meets the volume index requirements of the hot mix asphalt mixture.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for determining the reasonable construction temperature of foamed asphalt semi-warm mix. It uses image processing technology to quantitatively evaluate the degree of asphalt coating on the aggregate surface, effectively reducing human error. By evaluating the degree of asphalt coating on the aggregate surface and the volumetric properties of the mixture as a whole, a reasonable construction temperature is determined. This method reflects the overall material properties of the semi-warm mix and is more consistent with actual road conditions, making the determined construction temperature more scientific and reasonable. Furthermore, this invention determines the reasonable mixing and compaction temperature ranges of foamed asphalt semi-warm mix based on the degree of asphalt coating on the aggregate surface and the porosity of the mixture, providing a scientific basis for high-quality construction and performance improvement of foamed asphalt semi-warm mix. Attached Figure Description

[0019] Figure 1 This is the image capturing device used in this invention; Among them: 1-Photography equipment; 2-LED light strip; 3-Asphalt mixture; 4-Sample bowl. Detailed Implementation

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a particular order.

[0021] This invention provides a method for determining the appropriate construction temperature of foamed asphalt semi-warm mix, comprising the following steps: Step 1: Prepare foamed asphalt from base asphalt, and then perform semi-warm mixing operation on foamed asphalt and aggregate under different mixing temperature conditions to obtain foamed asphalt semi-warm mixing mixture. Step 2: Use a thermometer to measure the center temperature of the foamed asphalt semi-warm mix. When the target mixing temperature is reached, fill the sample bowl 4 with the mixture and let it stand for a period of time to allow the mixture to cool to room temperature. After cooling, place the sample bowl 4 containing the foamed asphalt semi-warm mix in the image capturing device and use the external photography device 1 to obtain an image of the surface of the foamed asphalt semi-warm mix. Step 3: Use the professional image processing software Halcon to perform inverse square color transformation preprocessing on the image, and crop the edge of the container to fit the area of ​​the mixture, and obtain the area calculation index. and interval calculation index And calculate the area calculation index. and interval calculation index The arithmetic mean of the sum is used to characterize the asphalt coating rate on the aggregate surface in foamed asphalt semi-warm mix. ; Step 4: Using the base asphalt and aggregates prepared in Step 1, prepare a hot-mix asphalt mixture at a set mixing temperature. Samples are prepared and images are collected and analyzed using the same methods as in Steps 2 and 3 to obtain the asphalt coating rate on the aggregate surface of the hot-mix asphalt mixture at the set mixing temperature. ; Step 5: Asphalt coating rate on aggregate surface in foamed asphalt semi-warm mixes prepared under different mixing temperature conditions. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture at a set mixing temperature By comparing the results, the reasonable mixing temperature range for foamed asphalt semi-warm mix was determined. W ; Step Six: Mix the foamed asphalt semi-warm mix within a suitable temperature range. W A suitable temperature was selected within the range of the corresponding median temperature to prepare foamed asphalt semi-warm mix. Marshall specimens were then formed at different molding temperatures and their volumetric properties were measured. Based on the volumetric property requirements specified for hot mix asphalt, a reasonable compaction temperature range for foamed asphalt semi-warm mix was determined.

[0022] Preferably, the foamed asphalt semi-warm mix has a reasonable mixing temperature range. W Select the matching ≤ The required mixing temperature of the foamed asphalt semi-warm mix is ​​defined as the temperature range.

[0023] Preferably, the process of acquiring the surface image of the foamed asphalt semi-warm mix includes: Step 1: Place the small bowl containing the foamed asphalt semi-warm mix sample at the center of the bottom surface inside the image capturing device. Step 2: Using a 64-megapixel digital camera placed close to the circular opening at the top of the image capturing device, adjust the camera parameters (shutter speed 1 / 400, aperture F4.0, ISO 640) and take a photo. Keep the camera parameters consistent in subsequent experiments to ensure data comparability. Step 3: When taking images, manually adjust the position of the sample preparation bowl 4 locally, and take three images of the asphalt mixture for each sample.

[0024] Preferably, the inverse square color transformation preprocessing formula is as follows:

[0025] In the formula: x is the image pixel value (an integer from 0 to 255); x' is the pixel value after inverse square color transformation; ε is a small constant to prevent division by zero, taken as 1e-6.

[0026] Preferably, the asphalt coating rate The calculation steps are as follows: Step 1: Using Halcon software, the preprocessed image is inversely binarized and segmented based on a global thresholding method using a grayscale distribution histogram. The white areas of the segmented image represent uncoated aggregate areas in the mixture, and the black areas represent asphalt-coated areas. The grayscale threshold value ranges from 100 to 200. Then, the area calculation index for each sample is calculated using the area calculation index formula for the three segmented images, and the average value is taken as the area calculation index for each sample. ; Step 2: Using Python software, the preprocessed grayscale image is partitioned into 26 intervals based on grayscale values ​​from smallest to largest (0-255). (Grayscale values ​​closer to 0 are more likely to be areas where aggregate is not coated with asphalt). Weights are assigned to each interval in a linearly decreasing manner from 1 to 0. The last grayscale value interval is 250-255 and has a weight of 0. Then, the interval calculation index is calculated for the three grayscale images of each sample according to the interval calculation index formula, and the average value is taken as the interval calculation index for each sample. ; Step 3: Based on the calculations above... and ,pass and The arithmetic mean was used to calculate the asphalt coating rate on the aggregate surface in the foamed asphalt semi-warm mix. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture .

[0027] Preferably, the formula for calculating the area index is:

[0028] In the formula: N w The total number of pixels in the white region of the segmented image; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0029] Preferably, the formula for calculating the interval index is:

[0030] In the formula: α i For the firsti The weights of each interval; N i For the first i The number of pixels in each interval; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0031] Preferably, the sample preparation bowl 4 has a bottom diameter of 14cm, a mouth diameter of 16cm, and a height of 6cm. The mixed foamed asphalt semi-warm mix and / or hot mix asphalt is filled into the sample preparation bowl 4 with a shovel until the mixture overflows from the mouth of the bowl. Then, the surface of the mixture is leveled along the mouth of the bowl with a scraper so that the mixture on the surface of the bowl is evenly distributed.

[0032] Preferably, the hot-mix asphalt mixture uses the same base asphalt type, asphalt content, aggregate type and gradation as the foamed asphalt semi-warm mix. The base asphalt is heated to 160~165℃, the aggregate is heated to 170~180℃, and the hot-mix asphalt mixture is mixed at 160℃.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] This invention provides a method for determining the appropriate construction temperature of foamed asphalt semi-warm mix, comprising the following steps: Step 1: Prepare foamed asphalt from base asphalt. After foaming, the asphalt and aggregate are mixed under different mixing temperature conditions to obtain foamed asphalt semi-warm mix. The different mixing temperature conditions are usually selected as 70℃, 80℃, 85℃, 90℃, 95℃, and 100℃. Users can also determine the temperature range according to the material type.

[0035] Step 2: Use a thermometer to measure the center temperature of the foamed asphalt semi-warm mix. When the target mixing temperature is reached, fill the sample bowl 4 with the mixture and let it stand for a period of time to allow the mixture to cool to room temperature. After cooling, place the sample bowl 4 containing the foamed asphalt semi-warm mix in the image capturing device and use the external photography device 1 to obtain an image of the surface of the foamed asphalt semi-warm mix. Step 3: Use the professional image processing software Halcon to perform inverse square color transformation preprocessing on the image, and crop the edge of the container to fit the area of ​​the mixture, and propose area calculation indicators. and interval calculation index The arithmetic mean of and is calculated to characterize the asphalt coating rate on the aggregate surface in foamed asphalt semi-warm mix. ; Step 4: Using the base asphalt and aggregates prepared in Step 1, prepare hot-mix asphalt mixtures. Samples are prepared and images are collected and analyzed using the same methods as in Steps 2 and 3 to obtain the asphalt coating rate on the aggregate surface of the hot-mix asphalt mixture. ; Step 5: Asphalt coating rate on aggregate surface in foamed asphalt semi-warm mixes prepared under different mixing temperature conditions. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture By comparing the results, the reasonable mixing temperature range for foamed asphalt semi-warm mix was determined. W ; Step Six: Mix the foamed asphalt semi-warm mix within a suitable temperature range. W A suitable temperature was selected within the range of the corresponding median temperature to prepare foamed asphalt semi-warm mix. Marshall specimens were then formed at different molding temperatures and their volumetric properties were measured. Based on the volumetric property requirements specified for hot mix asphalt, a reasonable compaction temperature range for foamed asphalt semi-warm mix was determined.

[0036] In this embodiment, the optimal mixing temperature range for the foamed asphalt semi-warm mix is... W Select the matching ≤ The required mixing temperature of the foamed asphalt semi-warm mix is ​​defined as the temperature range.

[0037] The present invention will be further described in detail below with reference to specific embodiments.

[0038] Step 1: The experiment used Zhenhai 90# asphalt, and both coarse and fine aggregates were limestone. The technical indicators of the asphalt and coarse and fine aggregates are shown in Table 1, Table 2 and Table 3, respectively.

[0039] Table 1 Technical Specifications of Zhenhai 90# Asphalt

[0040] Table 2 Coarse aggregate technical specifications

[0041] Table 3 Fine aggregate technical indicators

[0042] As shown in Table 1, the technical indicators of Zhenhai 90# asphalt and coarse and fine aggregates all meet the relevant technical requirements in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0043] Step 2: A foaming test was conducted on Zhenhai 90# asphalt using a Wirtgen WLB10S foaming machine. The base asphalt was heated at 2-3 different temperatures within the range of 150-170℃. Foaming water was added to the heated asphalt at a rate of 1%-4% of the asphalt mass. Based on the technical requirements for asphalt foaming characteristics specified in the "Technical Specification for Recycling Asphalt Pavement of Highways" (JTG / T 5521-2019), the optimal foaming conditions for Zhenhai 90# asphalt, including the optimal asphalt heating temperature and the amount of foaming water, were finally determined, as shown in Table 4.

[0044] Table 4 Optimal foaming conditions and foaming characteristics of Zhenhai 90# asphalt

[0045] Step 3: The aggregate gradation type of the foamed asphalt semi-warm mix is ​​AC. The gradation composition of 20 is shown in Table 5. The optimal foamed asphalt content was determined to be 3.5% through Marshall testing.

[0046] Table 5 Foamed asphalt semi-warm mix aggregate gradation composition

[0047] Step 4: Dry each grade of aggregate in an oven at 105℃±5℃ until constant weight, then remix each grade of aggregate according to the design gradation in Table 5. Heat the prepared coarse and fine aggregates to 105℃, put them into a mixing pot, and mix them evenly at the planned mixing temperature. Then, spray the foamed asphalt prepared under the optimal foaming conditions into the aggregates, mix and stir for 60 seconds, and finally add mineral powder and mix for 60 seconds to obtain foamed asphalt semi-warm mix under different mixing temperature conditions. When mixing hot mix asphalt, heat the dried aggregates to 170℃, add 3.5% of Zhenhai 90# asphalt heated to 160℃, and the mixing temperature of the mixture is 160℃. The remaining test conditions are the same as those for foamed asphalt semi-warm mix.

[0048] Step 5: Use a thermometer to measure the core temperature of the mixture. Once the target mixing temperature is reached, fill the sample preparation bowl 4 with the mixture. Use a scraper to smooth the surface of the mixture along the rim of the bowl. Let it stand for a period of time until the mixture cools to room temperature. Then, place the sample preparation bowl 4 in the attached... Figure 1The image capturing device shown is positioned at the center of the bottom surface inside the device. A 64-megapixel digital camera is placed close to the circular opening at the top of the device. The camera parameters (shutter speed 1 / 400, aperture F4.0, ISO 640) are adjusted, and the tray position is manually adjusted locally. A total of three high-resolution images of the surface of the mixture sample are captured.

[0049] Step 6: Use the professional image processing software Halcon to perform inverse square inverse color transformation preprocessing on the image, and crop the container edges to fit the area of ​​the mixture. Then, based on the gray-level distribution histogram, use the global threshold segmentation method to perform inverse binarization segmentation on the preprocessed image to distinguish between asphalt-coated and uncoated mixture areas, and calculate the area calculation index of the segmented images in the same batch. Using Python software, the cropped image was divided into 26 grayscale intervals in ascending order (0-255). Weights were then assigned to each interval in a linearly decreasing manner from 1 to 0, and an interval index was calculated for each sample. Further calculations and Arithmetic mean It is used to characterize the asphalt coating rate on the aggregate surface in foamed asphalt semi-warm mix, and to classify the foamed asphalt semi-warm mix... Value and hot-mix asphalt mixture The values ​​were compared and analyzed to determine the reasonable mixing temperature range for foamed asphalt semi-warm mix. Specific test results are shown in Table 6.

[0050] As shown in Table 6, the asphalt coating rate on the surface of the hot-mix asphalt mixture samples... The value was 0.050%, compared to the surface of foamed asphalt semi-warm mix samples under different mixing temperatures. The measurement results are as follows: ≤ Based on this standard, the reasonable mixing temperature range for foamed asphalt semi-warm mix is ​​85–100℃.

[0051] Table 6 Asphalt coating rate on aggregate surface in foamed asphalt semi-warm mix at different mixing temperatures

[0052] Step 7: Based on the determined reasonable mixing temperature range, a mixing temperature of 95℃ was selected for mixing the foamed asphalt semi-warm mix. Marshall specimens were then formed at varying compaction temperatures to further determine the porosity of the specimens. Specific test results are shown in Table 7. In accordance with the 3%~6% porosity range requirement specified in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004), the reasonable compaction temperature range for the foamed asphalt semi-warm mix was determined to be 75~90℃.

[0053] Table 7 Porosity of foamed asphalt semi-warm mix under different compaction temperatures

[0054] The above embodiments are merely exemplary and are not intended to limit the present invention. In actual production processes, when the asphalt and coarse and fine aggregate materials change, the temperature can be determined using the methods described in the above embodiments.

[0055] This invention provides a method for determining the appropriate construction temperature of foamed asphalt semi-warm mix. By utilizing image processing technology, the degree of asphalt coating on the aggregate surface can be quickly and quantitatively evaluated, effectively reducing human error. The method evaluates the asphalt coating on the aggregate surface and the volumetric properties of the mixture as a whole, thereby determining the appropriate construction temperature. This method reflects the overall material properties of the mixture and is more consistent with the actual road conditions. The construction temperature determined accordingly is more scientific and reasonable.

[0056] This invention determines the reasonable mixing and compaction temperature ranges for foamed asphalt semi-warm mix based on the asphalt coating on the aggregate surface and the porosity of the mixture, which can provide a scientific basis for high-quality construction and performance improvement of foamed asphalt semi-warm mix.

[0057] As a preferred embodiment of this invention, the process of acquiring the surface image of the foamed asphalt semi-warm mix includes: Step 1: Place the small bowl containing the foamed asphalt semi-warm mix sample at the center of the bottom surface inside the image capturing device. Step 2: Using a 64-megapixel digital camera placed close to the circular opening at the top of the image capturing device, adjust the camera parameters (shutter speed 1 / 400, aperture F4.0, ISO 640) and take a photo. Keep the camera parameters consistent in subsequent experiments to ensure data comparability. Step 3: When taking images, manually adjust the position of the sample preparation bowl 4 locally, and take three images of the asphalt mixture for each sample.

[0058] In this embodiment, the sample preparation bowl 4 has a bottom diameter of 14cm, a mouth diameter of 16cm, and a height of 6cm. The mixed foamed asphalt semi-warm mix is ​​filled into the sample preparation bowl 4 with a shovel until the mixture overflows from the mouth of the bowl. Then, the surface of the asphalt mixture 3 is smoothed along the mouth of the bowl with a scraper so that the mixture on the surface of the bowl is evenly distributed. In this embodiment, the image capturing device is a self-designed and constructed dedicated image capturing device. The image capturing device is 60cm long, 60cm wide, and 60cm high. A circular hole with a diameter of 11cm is set in the center of the top surface for installing external photography equipment 1 to obtain images of the mixture. The image capturing device has four LED light strips 2 on the top surface and the left and right sides. The LED light strips 2 on the left and right sides are 25cm away from the bottom surface. All six sides inside are equipped with milky white PC (polycarbonate) light-diffusing plates to provide uniform and stable lighting conditions inside the device, thereby ensuring image clarity and data reliability.

[0059] In a preferred embodiment of this invention, the inverse square color transformation can reduce reflective interference on the surface of the mixture and improve the contrast between the asphalt-coated and uncoated areas of the mixture surface; the calculation formula for the inverse square color transformation is as follows:

[0060] In the formula: Image pixel values ​​(integers from 0 to 255); These are the pixel values ​​after performing the inverse square color transformation; To prevent small constants from being divided by 0, we take 1e-6.

[0061] As a preferred embodiment of this example, the asphalt coating rate The calculation steps are as follows: Step 1: Using Halcon software, the preprocessed image is inversely binarized and segmented based on the grayscale distribution histogram using a global thresholding method. The white areas of the segmented image represent uncoated aggregate areas in the mixture, and the black areas represent asphalt-coated areas. The grayscale threshold value ranges from 100 to 200. Then, the area calculation index of the three segmented images for each sample is calculated according to Formula 2, and the average value is taken as the area calculation index for each sample. ;

[0062] In the formula: N w The total number of pixels in the white region of the segmented image; N tThis represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0063] Step 2: Using Python software, the preprocessed grayscale image is partitioned into 26 intervals based on grayscale values ​​from smallest to largest (0-255). (Grayscale values ​​closer to 0 are more likely to be areas where aggregate is not coated with asphalt). Weights are assigned to each interval in a linearly decreasing manner from 1 to 0. The last grayscale value interval is 250-255 and has a weight of 0. Then, the interval calculation index of the three grayscale images for each sample is calculated according to Formula 3, and the average value is taken as the interval calculation index for each sample. ;

[0064] In the formula: For the first i The weights of each interval; For the first i The number of pixels in each interval; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

[0065] Step 3: Based on the calculations above... and Calculate the asphalt coating rate on the aggregate surface in foamed asphalt semi-warm mix according to Formula 4. 。 in, The smaller the value, the better the asphalt coating on the aggregate surface in the foamed asphalt semi-warm mix.

[0066]

[0067] Adopted and The calculations are performed in the same manner.

[0068] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A method for determining the appropriate construction temperature of foamed asphalt semi-warm mix, characterized in that, Includes the following steps: S1: Foamed asphalt is prepared from base asphalt, and then foamed asphalt and aggregate are mixed at a series of mixing temperatures to obtain foamed asphalt semi-warm mix; base asphalt and aggregate are mixed at a set mixing temperature to obtain hot mix asphalt. S2: Obtain the area calculation index and interval calculation index for foamed asphalt semi-warm mix and hot mix asphalt mixture, and calculate the asphalt coating rate on the aggregate surface in the foamed asphalt semi-warm mix at a series of mixing temperatures. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture at a set mixing temperature ; S3: Asphalt coating rate on aggregate surface in foamed asphalt semi-warm mix at comparative mixing temperatures. Asphalt coating rate on aggregate surface in hot-mix asphalt mixture at a set mixing temperature Determine the reasonable mixing temperature range for foamed asphalt semi-warm mix. W ; S4: Within the reasonable mixing temperature range of foamed asphalt semi-warm mix. W Foamed asphalt semi-warm mix was prepared at a set temperature near the median value. Marshall specimens were made at different molding temperatures and the volume index was tested. Based on the volume index requirements of hot mix asphalt, the reasonable compaction temperature range of foamed asphalt semi-warm mix was determined.

2. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 1, characterized in that, In S2, the process of obtaining the area calculation index and interval calculation index of foamed asphalt semi-warm mix asphalt and the area calculation index and interval calculation index of hot mix asphalt is as follows: S21: Obtain surface images of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture; S22: Perform inverse square inverse color transformation preprocessing on the surface images of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture to obtain the preprocessed images of the foamed asphalt semi-warm mix and / or the preprocessed images of the hot mix asphalt mixture. S23: Using Halcon software, the images of pre-processed foamed asphalt semi-warm mix and / or pre-processed hot mix asphalt mixture are processed. Based on the grayscale distribution histogram, a grayscale threshold in the range of 100-200 is selected. Global threshold segmentation is used to perform inverse binarization segmentation to obtain segmented images. In the segmented images, white areas represent aggregate areas not coated with asphalt, and black areas represent aggregate surfaces coated with asphalt. According to the area calculation index formula, the area index of each segmented image of a single sample is calculated, and the average value is taken as the area calculation index of each sample. S24: Use Python software to divide the pre-processed foamed asphalt semi-warm mix image and / or pre-processed hot mix asphalt image into gray levels. According to the interval calculation index formula, calculate the interval index of each pre-processed foamed asphalt semi-warm mix image and / or pre-processed hot mix asphalt image for a single sample, and take the average value as the interval calculation index for each sample.

3. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 2, characterized in that, In S22, the formula for the inverse square color transformation preprocessing is as follows: In the formula: x is the image pixel value (an integer from 0 to 255); x' is the pixel value after inverse square color transformation preprocessing; ε is a small constant to prevent division by zero, taken as 1e-6.

4. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 2, characterized in that, The formula for calculating the area index is as follows: In the formula: For area calculation indicators; N w The total number of pixels in the white region of the segmented image; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

5. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 2, characterized in that, The formula for calculating the interval index is as follows: In the formula: Indicators are calculated over an interval. α i For the first i The weights of each interval; N i For the first i The number of pixels in each interval; N t This represents the total number of pixels in the pre-processed foamed asphalt semi-warm mix image and / or the pre-processed hot mix asphalt image.

6. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 2, characterized in that, In S24, the grayscale levels are specifically divided as follows: The grayscale value range of 0 to 255 is divided into 26 equal grayscale intervals. The lower the grayscale value, the more it represents the area where the aggregate is not coated with asphalt. Each grayscale interval is assigned a corresponding weight from 1 to 0 according to a linear decreasing rule, with the weight of the grayscale interval of 250 to 255 set to 0.

7. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 2, characterized in that, In S21, the process of obtaining the surface image of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture is as follows: Use a thermometer to measure the core temperature of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture. When the target mixing temperature is reached, fill the sample preparation bowl with the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture and let it stand for a period of time to cool to room temperature. After cooling, the sample bowl containing the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture is placed in an image capturing device, and the surface image of the foamed asphalt semi-warm mix and / or the hot mix asphalt mixture is captured by an external photographic device.

8. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 1, characterized in that, In S2, the asphalt coating rate on the aggregate surface of the foamed asphalt semi-warm mix is... It is the arithmetic mean of the sum of the area calculation index and the interval calculation index of foamed asphalt semi-warm mix. In S2, the asphalt coating rate of the aggregate surface in the hot-mix asphalt mixture It is the arithmetic mean of the sum of the area calculation index and the interval calculation index of hot-mix asphalt mixture.

9. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 1, characterized in that, In S3, the reasonable mixing temperature range of the foamed asphalt semi-warm mix is... W To comply with ≤ The mixing temperature range of foamed asphalt semi-warm mix under certain conditions.

10. The method for determining the reasonable construction temperature of foamed asphalt semi-warm mix as described in claim 1, characterized in that, In S4, the reasonable compaction temperature range of the foamed asphalt semi-warm mix is ​​the molding temperature range that meets the volume index requirements of the hot mix asphalt mixture.

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