Method for evaluating comprehensive skid resistance of aggregate for asphalt mixture

Abstract

A method for evaluating the comprehensive skid resistance performance of aggregates used in asphalt mixtures is proposed. The purpose of this invention is to address the shortcomings of existing aggregate evaluation methods in reflecting the overall performance of aggregates. The evaluation method includes: 1. Testing the physical and mechanical properties of different aggregates; 2. Selecting polishing stability, crushing value, abrasion value, adhesion, and density as representative aggregate skid resistance performance indicators from step 1; 3. Normalizing the representative aggregate skid resistance performance indicators from step 2 and plotting a radar chart, which is divided into k regions; 4. Determining the characteristic vector U of different aggregates. i Finally, the comprehensive performance of different aggregates is evaluated. This invention, based on the comprehensive skid resistance performance evaluation method for asphalt mixture aggregates, can quickly evaluate the skid resistance performance of different aggregates, comprehensively evaluate the skid resistance performance of different aggregates, and distinguish the skid resistance ranges of different aggregates.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, and specifically relates to a method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures. Background Technology

[0002] As one of the most expensive parts of highway construction, the surface layer of asphalt pavement consists of approximately 95% natural materials (coarse and fine aggregates and mineral fillers) and 5% asphalt binder. For example, constructing a 1-kilometer-long highway requires 12 tons of aggregate to build a 10-meter-wide subgrade and a 45-centimeter-thick base course (base course and subbase). For the surface layer, a 20-centimeter-thick asphalt layer requires 250 tons of asphalt and 5.15 tons of aggregate. Aggregate is the most consumed raw material in asphalt pavement construction and is crucial to the performance of the asphalt mixture. Furthermore, as the medium in contact between tires and the road surface, aggregate directly bears vehicle loads; its performance, especially its long-term skid resistance, plays a dominant and decisive role in the skid resistance of asphalt pavement. Therefore, the selection of aggregate is particularly critical.

[0003] In recent years, the rapid development of road infrastructure has also led to a rapid decline in natural aggregate reserves, making it imperative to find suitable wear-resistant aggregates and determine their skid resistance range. Due to its good wear resistance, calcined bauxite aggregates are often used to improve the skid resistance of road surfaces. However, there are many types of calcined bauxite, with significant differences in performance between different grades, and the relationship between their properties and those of natural aggregates is unclear, leading to confusion in the application of calcined bauxite. Furthermore, different indicators correspond to different physical and mechanical properties; commonly used indicators for evaluating aggregate performance include crushing value, Los Angeles abrasion value, polishing value, adhesion, and density, but these indicators do not consider the long-term skid resistance of aggregates. Additionally, a single aggregate often exhibits superiority in one or more indicators, making it difficult to reflect the overall performance of the aggregate. Therefore, selecting an efficient and accurate method to evaluate the comprehensive skid resistance of aggregates is essential.

[0004] Radar charts, also known as comprehensive financial ratio analysis, are an early multi-factor analysis method used in the financial field. They were initially used for comprehensive analysis and evaluation of financial conditions. Radar charts are suitable for visually and graphically reflecting the changing patterns of multiple indicators on a two-dimensional plane, enabling comprehensive processing and statistical analysis of multiple variables. In recent years, scholars both domestically and internationally have applied them to the field of engineering construction, achieving good results. Therefore, this paper uses radar charts to comprehensively evaluate the skid resistance performance of aggregates, aiming to quickly select aggregates and improve the skid resistance and durability of road surfaces. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing aggregate evaluation methods are insufficient to reflect the comprehensive performance of aggregates, and to provide a method for evaluating the comprehensive skid resistance performance of aggregates used in asphalt mixtures.

[0006] The method for evaluating the comprehensive skid resistance of aggregates in asphalt mixtures based on radar charts, as described in this invention, is implemented according to the following steps:

[0007] 1. The physical and mechanical properties of different aggregates were tested. The physical and mechanical properties of each aggregate included polishing value, crushing value, abrasion value, adhesion, density and moisture content. Each aggregate was polished separately to obtain polishing stability value.

[0008] II. Select the polishing stability value, crushing value, abrasion value, adhesion, and density from step one as representative aggregate anti-skid performance indicators. j is the sequence number of the selected index, and there are k representative aggregate anti-skid performance indices.

[0009] III. Drawing radar charts:

[0010] a. Standardization: Normalize the representative aggregate anti-skid performance indicators from step two to obtain the standard values ​​of the representative aggregate anti-skid performance indicators. ;

[0011] b. Mapping: Draw a radar chart, which is divided into k regions. Calculate the standardized value (transformed value) r after linear transformation according to equation (3). ij The standardized values ​​after linear transformation are displayed in the radar image;

[0012] (3)

[0013] IV. Comprehensive performance evaluation of aggregates:

[0014] The characteristic vector U of different aggregates is determined according to equation (4). i A i and L i These are the area and perimeter of radar charts for different evaluation indicators.

[0015] (4)

[0016] Where A i and L i They are calculated using the following formula (5);

[0017] (5)

[0018] The evaluation vector Z is defined using equation (6). i ,

[0019] (6)

[0020] In the formula: Z i1 Z i2Z represents the relative area and perimeter of the evaluation index, respectively. i1 and Z i2 The maximum value of A in equation (7) is calculated from equation (7). i The largest radar chart area represents the evaluation metric.

[0021] (7)

[0022] Finally, Equation (8) is used to evaluate the comprehensive performance of different aggregates, and the aggregate comprehensive performance index is calculated. The calculation formula is as follows:

[0023] (8).

[0024] Compared with existing technologies, the radar chart-based comprehensive skid resistance evaluation method for aggregates used in asphalt mixtures of this invention has the following beneficial effects: This invention, based on the comprehensive skid resistance evaluation method for aggregates used in asphalt mixtures, considers long-term performance and uses the polishing stability value after long-term polishing instead of the traditional polishing value as an indicator of aggregate polishing resistance. This allows for rapid evaluation of the skid resistance of different aggregates, which is of great significance for comprehensively evaluating the skid resistance of different aggregates, distinguishing the skid resistance ranges of different aggregates, and improving the skid resistance and durability of asphalt pavements. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for evaluating the comprehensive skid resistance of aggregates in asphalt mixtures based on radar charts, as per the present invention.

[0026] Figure 2 This is a bar chart showing the crushing values ​​of seven different aggregates in the example;

[0027] Figure 3 This is a bar chart showing the abrasion values ​​of seven different aggregates in the example;

[0028] Figure 4 This is a bar chart showing the polishing stability values ​​of seven different aggregates in the example;

[0029] Figure 5 The bar chart shows the water absorption rates of seven different aggregates in the example.

[0030] Figure 6 The bar chart shows the seven different aggregate densities in the example.

[0031] Figure 7 Radar graph showing the anti-slip properties of aggregates 88# calcined bauxite, basalt and limestone in the example;

[0032] Figure 8 Radar graph showing the anti-slip properties of aggregates of calcined bauxite, basalt and limestone No. 85 in the example;

[0033] Figure 9 Radar graph showing the anti-slip properties of aggregates of calcined bauxite, basalt and limestone in the example;

[0034] Figure 10 Radar graph showing the anti-slip properties of aggregates of calcined bauxite, basalt and limestone No. 75 in the example;

[0035] Figure 11 The radar image shows the anti-slip performance of aggregates 70# calcined bauxite, basalt, and limestone in the example. Detailed Implementation

[0036] Specific Implementation Method 1: This implementation method for evaluating the comprehensive skid resistance performance of aggregates in asphalt mixtures based on radar charts is carried out according to the following steps:

[0037] 1. The physical and mechanical properties of different aggregates were tested. The physical and mechanical properties of each aggregate included polishing value, crushing value, abrasion value, adhesion, density and moisture content. Each aggregate was polished separately to obtain polishing stability value.

[0038] II. Select the polishing stability value, crushing value, abrasion value, adhesion, and density from step one as representative aggregate anti-skid performance indicators. j is the sequence number of the selected index, and there are k representative aggregate anti-skid performance indices.

[0039] III. Drawing radar charts:

[0040] a. Standardization: Normalize the representative aggregate anti-skid performance indicators from step two to obtain the standard values ​​of the representative aggregate anti-skid performance indicators. ;

[0041] b. Mapping: Draw a radar chart, which is divided into k regions. Calculate the standardized value (transformed value) r after linear transformation according to equation (3). ij The standardized values ​​after linear transformation are displayed in the radar image;

[0042] (3)

[0043] IV. Comprehensive performance evaluation of aggregates:

[0044] The characteristic vector U of different aggregates is determined according to equation (4). i A i and L i These are the area and perimeter of radar charts for different evaluation indicators.

[0045] (4)

[0046] Where Ai and L i They are calculated using the following formula (5);

[0047] (5)

[0048] The evaluation vector Z is defined using equation (6). i ,

[0049] (6)

[0050] In the formula: Z i1 Z i2 Z represents the relative area and perimeter of the evaluation index, respectively. i1 and Z i2 The maximum value of A in equation (7) is calculated from equation (7). i The largest radar chart area represents the evaluation metric.

[0051] (7)

[0052] Finally, Equation (8) is used to evaluate the comprehensive performance of different aggregates, and the aggregate comprehensive performance index is calculated. The calculation formula is as follows:

[0053] (8).

[0054] In step two of this embodiment, in order to further evaluate the anti-slip performance, the traditional polishing value is not used as the standard when selecting the index. Instead, the polishing stability value after long-term polishing is used as the aggregate anti-polishing performance index to comprehensively evaluate the aggregate anti-slip performance.

[0055] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the aggregate mentioned in step one is artificial aggregate or natural aggregate.

[0056] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the artificial aggregate is calcined bauxite.

[0057] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the natural aggregate used is basalt or limestone.

[0058] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 3 in that the aggregate in step 1 is crushed and passed through a 75 µm sieve.

[0059] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One through Five in that the normalization formula in step a is:

[0060] (1)

[0061] In the formula, Let j be the maximum value of the selected indicators. The minimum value of j selected indicators.

[0062] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Five in that the normalization formula in step a is:

[0063] (2)

[0064] In the formula, Let j be the maximum value of the selected indicators. The minimum value of j selected indicators.

[0065] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that step one uses the Highway Engineering Aggregate Test Procedure (JTG E42-2005) to test the physical and mechanical properties of the aggregate.

[0066] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that step four... The higher the value, the higher the overall anti-skid performance of the aggregate.

[0067] Example: This example demonstrates a radar chart-based method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures, implemented according to the following steps:

[0068] First, seven different aggregates were crushed separately. The crushed aggregate samples were passed through a 75 µm sieve. Then, the physical and mechanical properties of the different aggregates were tested according to the Highway Engineering Aggregate Test Procedure (JTG E42-2005). The physical and mechanical properties of each aggregate included polishing value, crushing value, abrasion value, adhesion, density, and moisture content. Considering the long-term anti-skid performance of the aggregates, the aggregates were polished. The polishing value when the polishing rate of the aggregate tended to be gradual was taken as the polishing stability value.

[0069] II. Select the polishing stability value, crushing value, abrasion value, adhesion, and density from step one as representative aggregate anti-skid performance indicators. , where j is the sequence number of the selected index, and when j=1, 2, 3, 4, 5, they represent crushing value, abrasion value, polishing stability value, adhesion, density and moisture content, respectively; i is the sequence number of the object to be evaluated, and when i=1, 2, 3, 4, 5, 6, 7, they represent 88# calcined bauxite, 85# calcined bauxite, 80# calcined bauxite, 75# calcined bauxite, 70# calcined bauxite, basalt and limestone, respectively. There are a total of k representative aggregate anti-skid performance indices, k=5;

[0070] III. Drawing radar charts:

[0071] a. Standardization: Normalize the representative aggregate anti-skid performance indicators from step two. The normalization formula is as follows:

[0072] (1) or (2), where, Let j be the maximum value of the selected indicators. The minimum value of j selected indicators is used to obtain the standard value of the representative aggregate anti-skid performance index. The standard values ​​of polishing stability, adhesion and density are calculated using formula (1), and the standard values ​​of crushing value and abrasion value are calculated using formula (2), thus obtaining the standard values ​​of representative aggregate anti-skid performance indicators. ;

[0073] b. Mapping: Draw a radar chart, which is divided into k regions. Calculate the standardized value (transformed value) r after linear transformation according to equation (3). ij The standardized values ​​after linear transformation (the radius of the corresponding sector) are displayed in the radar image;

[0074] (3)

[0075] IV. Comprehensive performance evaluation of aggregates:

[0076] The characteristic vector U of different aggregates is determined according to equation (4). i A i and L i These are the area and perimeter of radar charts for different evaluation indicators.

[0077] (4)

[0078] Where A i and L i They are calculated using the following formula (5);

[0079] (5)

[0080] The evaluation vector Z is defined using equation (6). i ,

[0081] (6)

[0082] In the formula: Z i1 Z i2 Z represents the relative area and perimeter of the evaluation index, respectively. i1 and Z i2 The maximum value of A in equation (7) is calculated from equation (7). iThe largest radar chart area represents the evaluation metric.

[0083] (7)

[0084] Finally, Equation (8) is used to evaluate the comprehensive performance of different aggregates, and the aggregate comprehensive performance index is calculated. The calculation formula is as follows: The higher the value, the higher the overall anti-skid performance of the aggregate.

[0085] (8).

[0086] The physical and mechanical properties of the aggregates were tested.

[0087] In this embodiment, the seven different aggregates are five types of calcined bauxite artificial aggregates (88#, 85#, 80#, 75#, and 70#) and two types of natural aggregates (basalt and limestone).

[0088] Depend on Figure 2 It can be seen that as the grade decreases, the crushing value of calcined bauxite gradually increases, indicating that its compressive strength gradually decreases; however, it still meets the specifications and can be used as road surface aggregate. At the same time, the crushing value of calcined bauxite aggregate is quite different from that of natural aggregate. The compressive strength of different grades of calcined bauxite is about 10%-65% higher than that of limestone; while the performance of basalt is basically equivalent to that of 80# calcined bauxite.

[0089] Los Angeles abrasion values ​​of different aggregates, such as Figure 3 As shown, similar to the crushing value, the Los Angeles abrasion values, from smallest to largest, are: 88# calcined bauxite > 85# calcined bauxite > 80# calcined bauxite > 75# calcined bauxite > 70# calcined bauxite, which also meets the specifications. Compared with limestone, the abrasion values ​​of different grades of calcined bauxite aggregates decrease by about 20%-50%, and the wear resistance is significantly improved, while the wear resistance of basalt is basically equivalent to that of 80# calcined bauxite.

[0090] Figure 4 The graph shows the variation of polished stability values ​​of calcined bauxite aggregates of different grades. As can be seen from the graph, the polished value of calcined bauxite aggregates decreases with decreasing grade. When the grade is less than 80#, its polished value is less than 42, making it unsuitable for use as surface aggregate for road surfaces, but still about 10% higher than that of limestone aggregates.

[0091] Figures 5-6 The graph shows the water absorption rate and density of calcined bauxite aggregates. As can be seen from the graph, 75# and 70# calcined bauxite have excessively high water absorption rates, requiring careful consideration during application.

[0092] Using radar charts to comprehensively evaluate the anti-skid performance of aggregates:

[0093] The radar chart method was used to determine the ranking of the comprehensive performance of different types of aggregates. According to formula (3), r can be obtained. ij As shown in Table 1, the results indicate that calcined bauxite #88 has the best overall performance, while limestone has the worst. Tables Z1-Z5 represent five types of calcined bauxite-based artificial aggregates: #88, #85, #80, #75, and #70. Z6 represents basalt, and Z7 represents limestone.

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[0108] Table 1 r ij result

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Claims

1. A method for evaluating the comprehensive skid resistance performance of aggregates used in asphalt mixtures, characterized in that... The method for evaluating the comprehensive anti-skid performance of aggregates is implemented according to the following steps:

1. Test the physical and mechanical properties of different aggregates. The physical and mechanical properties of each aggregate include polishing value, crushing value, abrasion value, adhesion, density and moisture content. Then, polish each aggregate separately to obtain polishing stability value. II. Select the polishing stability value, crushing value, abrasion value, adhesion, and density from step one as representative aggregate anti-skid performance indicators. j is the serial number of the selected anti-skid performance index, and there are k representative anti-skid performance indices for aggregates. III. Drawing radar charts: a. Standardization: Normalize the representative aggregate anti-skid performance indicators from step two to obtain the standard values ​​of the representative aggregate anti-skid performance indicators. ; b. Mapping: Draw a radar chart, which is divided into k regions. Calculate the standardized value r after linear transformation according to equation (3). ij The standardized values ​​after linear transformation are displayed in the radar image; (3) IV. Comprehensive performance evaluation of aggregates: The characteristic vector U of different aggregates is determined according to equation (4). i A i and L i These are the area and perimeter of radar charts for different evaluation indicators. (4) Where A i and L i They are calculated using the following formula (5); (5) The evaluation vector Z is defined using equation (6). i , (6) In the formula: Z i1 Z i2 Z represents the relative area and perimeter of the evaluation index, respectively. i1 and Z i2 The maximum value of A in equation (7) is calculated from equation (7). i The largest radar chart area represents the evaluation metric. (7) Finally, Equation (8) is used to evaluate the comprehensive performance of different aggregates, and the aggregate comprehensive performance index is calculated. The calculation formula is as follows: (8)。 2. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... The aggregate mentioned in step one is either artificial or natural aggregate.

3. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 2, characterized in that... The artificial aggregate is calcined bauxite.

4. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 2, characterized in that... The natural aggregates mentioned are basalt or limestone.

5. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... In step one, the aggregate is crushed and passed through a 75 µm sieve.

6. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... The normalization formula in step a is: (1) In the formula, Let j be the maximum value of the selected indicators. The minimum value of j selected indicators.

7. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... The normalization formula in step a is: (2) In the formula, Let j be the maximum value of the selected indicators. The minimum value of j selected indicators.

8. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... In step one, the physical and mechanical properties of the aggregates are tested using the Highway Engineering Aggregate Test Procedure.

9. The method for evaluating the comprehensive skid resistance of aggregates used in asphalt mixtures according to claim 1, characterized in that... In step four The higher the value, the higher the overall anti-skid performance of the aggregate.

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