A hot-mixed asphalt mixture production mix proportion design method considering construction factors

Abstract

This invention relates to the field of transportation civil engineering technology, specifically to a method for designing the mix proportion of hot-mix asphalt mixtures considering construction factors. First, samples are taken from each hot aggregate bin and mixed according to the target mix proportion. Then, the passing rate of key sieve openings in the aggregate mixture is obtained through sieving tests, and the quality deviation P of each aggregate specification is calculated. i When P i If all values ​​are less than 5%, proceed to on-site simulation testing; otherwise, adjust the feeding speed of each cold material bin until P is reached. i All values ​​are less than 5%. On-site simulation testing involves compacting asphalt mixture samples in a specific mold, measuring the sample's compaction degree, texture depth, and permeability coefficient, and taking core samples to test the Marshall stability and profile uniformity coefficient of the core samples to ensure they meet technical requirements. If the requirements are not met, the proportions of each aggregate specification are adjusted at 1% intervals, and the test is repeated. This invention can improve the efficiency, accuracy, and reliability of asphalt mixture production mix design and also provides a basis for mix design correction.

Description

Technical Field

[0001] This invention relates to the field of transportation civil engineering technology, specifically to a method for designing the mix proportion of hot-mix asphalt mixtures that takes into account construction factors. Background Technology

[0002] Hot-mix asphalt mixture is the most widely used pavement material in my country and plays a crucial role in highway transportation construction. According to the relevant requirements of the current "Technical Specification for Construction of Highway Asphalt Pavement (JTGF40-2004)" in my country, the mix design of hot-mix asphalt mixture generally includes three stages: target mix design, production mix design, and production mix verification on test roads.

[0003] In the actual production and construction of hot-mix asphalt mixtures, the proportions of different aggregate sizes are determined based on the target mix design. Aggregates are supplied (loaded) from their respective storage bins (cold bins) and then heated before entering the corresponding hot bins. Due to factors such as moisture evaporation during heating, aggregate loading speed, and cross-contamination between different aggregate sizes during loading, the actual composition of different aggregate sizes in the hot bins deviates from their original composition in the cold bins. The purpose of the production mix design is to adjust the supply ratio of different aggregate sizes in the hot bins to address the difference in composition between the cold and hot bins, thereby reducing the discrepancy with the target mix design.

[0004] The "Technical Specification for Construction of Asphalt Pavement on Highways (JTGF40-2004)" states that the production mix design steps can refer to the target mix design steps. However, the purposes of production mix design and target mix design are different. If the same design steps are used for both, the production mix design will have the following shortcomings:

[0005] (1) Existing methods cannot take into account the uncertain influence of construction factors such as mixing equipment, construction technology, construction tools and construction environment on the mix proportion during the mixing and compaction of asphalt mixtures. This can easily lead to a large difference between the production mix proportion design results and the production mix proportion verification results. As a result, the mix proportion design process has to be restarted, which causes unnecessary waste of time, materials and personnel, and is not conducive to the control of project schedule and cost.

[0006] (2) The difference between the production mix proportion and the target mix proportion of asphalt mixture is mainly due to the process of feeding material from cold silos to hot silos. Existing methods have not been able to directly address this problem, making it difficult to effectively adjust the feeding ratio of each hot silo. This results in a large deviation between the final asphalt mixture mix proportion and the target mix proportion, leading to the invalidation of the production mix proportion design.

[0007] (3) Existing methods cannot determine whether asphalt mixtures have segregated.

[0008] Therefore, designing a mix design method for hot-mix asphalt mixtures that takes into account construction factors, in order to improve the efficiency, accuracy and reliability of mix design for asphalt mixtures, has become an urgent requirement. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for designing the mix proportion of hot-mix asphalt mixtures that takes into account the influence of construction factors, so as to improve the efficiency, accuracy and reliability of the mix proportion design for asphalt mixture production.

[0010] The technical solution to the technical problem to be solved by the present invention is: a method for designing the mix proportion of hot-mix asphalt mixtures considering construction factors, characterized by comprising the following steps:

[0011] Step 1: Take samples from each hot aggregate bin according to the target mix ratio and mix the aggregate mixture.

[0012] Step 2: Obtain the passing rate of the key sieve openings of the aggregate mixture through sieving tests, and calculate the mass deviations P1, P2, P3, P4, and P5 for each aggregate specification.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] In the formula: T 0.075 T 2.36 T 4.75 T 9.5 T 19 The values ​​represent the passing rates of the aggregate mixture through sieves with apertures of 0.075mm, 2.36mm, 4.75mm, 9.5mm, and 19mm, respectively, in percentage (%). 0.075 S 2.36 S 4.75 S 9.5 S 19 The values ​​are: passing rates of the target mix proportions at sieve openings of 0.075mm, 2.36mm, 4.75mm, 9.5mm, and 19mm, respectively, in percentage (%); P1, P2, P3, P4, and P5 are the quality deviations of mineral powder, 0-5mm aggregate, 5-10mm aggregate, 10-20mm aggregate, and 20-30mm aggregate, respectively, in percentage (%).

[0019] Step 3, when P iWhen the absolute values ​​are all less than 5%, proceed to step four; otherwise, use formula 6 to adjust the feeding speed of each cold material bin, and repeat steps one through three until P. i All less than 5%,

[0020] α i =-(1+w i )P i (6)

[0021] In the formula, α i This is a correction factor for the feeding speed of the cold silo corresponding to the i-th aggregate specification, expressed as a percentage. When it is positive, the feeding speed of the corresponding cold silo should be increased by α. i Conversely, it reduces α. i ;w i P represents the moisture content of the i-th aggregate specification, expressed in %. i The mass deviation of the i-th aggregate specification is expressed in %; i is a natural number less than or equal to 5.

[0022] Step 4: Place the test mold in a hardened, flat open space with the top of the test mold flush with the ground. Add m matching iron pads inside the test mold so that the height inside the test mold is the same as the thickness of the corresponding asphalt surface layer.

[0023] Step 5: Mix the aggregate mixture obtained in Step 3 with the target mix proportion and the optimal asphalt content to obtain an asphalt mixture. Pour the mixed asphalt mixture into the test mold described in Step 4 until the specified filling height H is reached. The filling height H is calculated according to Formula 7.

[0024] H=a×(h-10×m) (7)

[0025] In the formula, H is the filling height in mm; a is the loose paving coefficient used in actual construction; h is the height of the test mold in mm; and m is the number of pads in the test mold.

[0026] Step 6: Compact the asphalt mixture that has been loaded into the test mold as described in Step 5 according to the compaction equipment and compaction plan used in actual construction.

[0027] Step 7: Determine the compaction degree, texture depth, and permeability coefficient of the asphalt mixture sample after compaction, and take core samples to test whether the Marshall stability and profile uniformity coefficient of the core samples meet the technical requirements; if the technical requirements are met, complete the production mix design; if the technical requirements are not met, adjust the proportion of each aggregate specification at 1% intervals, and repeat steps 4 to 7 until the requirements are met.

[0028] Better still, in step two, the key sieve openings for asphalt mixtures with a maximum nominal particle size less than or equal to 26.5 mm are 0.075 mm, 2.36 mm, 4.75 mm, and 9.5 mm, corresponding to aggregate specifications of mineral powder, 0-5 mm aggregate, 5-10 mm aggregate, and 10-20 mm aggregate, respectively.

[0029] Better still, in step two, the key sieve openings for asphalt mixtures with a maximum nominal particle size greater than 26.5 mm are 0.075 mm, 2.36 mm, 4.75 mm, 9.5 mm, and 19 mm, corresponding to aggregate specifications of: mineral powder, 0-5 mm aggregate, 5-10 mm aggregate, 10-20 mm aggregate, and 20-30 mm aggregate, respectively.

[0030] Even better, in step four, the mold size for asphalt mixtures with a maximum nominal particle size of less than or equal to 26.5 mm is 500 mm × 500 mm × 80 mm, and the size of the iron pad is 499 mm × 499 mm × 10 mm.

[0031] Even better, in step four, the size of the iron test mold for asphalt mixtures with a maximum nominal particle size greater than 26.5 mm is 800 mm × 800 mm × 150 mm, and the size of the iron pad is 799 mm × 799 mm × 10 mm.

[0032] Better still, in step seven, the asphalt mixture sample after core drilling is laterally cut open, and five sections are randomly selected and arranged according to...

[0033] Equation 8 calculates the profile uniformity coefficient.

[0034]

[0035] In the formula: β is the profile uniformity coefficient; n k Let k be the number of coarse aggregates in the k-th representative profile, where k is a natural number less than or equal to 5. The average number of coarse aggregates in five representative cross-sections; the coarse aggregates refer to aggregates with a particle size greater than 4.75 mm.

[0036] Better yet, in step seven:

[0037] The technical requirements for the profile uniformity coefficient are: less than or equal to 0.20 for densely mixed asphalt mixtures and less than or equal to 0.15 for asphalt mastic macadam mixtures;

[0038] The technical requirements for the construction depth are: for both densely packed asphalt mixtures and asphalt mastic macadam mixtures, the depth should be greater than or equal to 1.0 mm and less than or equal to 1.2 mm.

[0039] The compaction degree, permeability coefficient, and core sample Marshall stability should meet the requirements of current specifications.

[0040] Even better, when the test mold is 500mm×500mm×80mm, the selected cross-sectional dimensions are 40mm×40mm.

[0041] Even better, when the test mold is 800mm×800mm×150mm, the selected cross-sectional dimensions are 80mm×80mm.

[0042] The beneficial effects of this invention are as follows: This invention can better characterize the influence of construction factors (feeding process, construction equipment, construction technology, etc.) on the mix proportion of asphalt mixture under the actual production and construction conditions of hot-mix asphalt mixture, and can test whether the asphalt mixture segregates, thereby improving the efficiency, accuracy and reliability of asphalt mixture production mix proportion design, and also providing a basis for mix proportion correction. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the process flow of one embodiment of the present invention.

[0044] In the figure: there are no attached labels or explanations. Detailed Implementation

[0045] To make the technical solution and beneficial effects of the present invention clearer, the embodiments of the present invention will be explained in further detail below.

[0046] A method for designing the mix proportions of hot-mix asphalt mixtures that takes construction factors into account, characterized by the following steps:

[0047] Step 1: Sample aggregates of different specifications from each hot aggregate bin, and mix them into an aggregate mixture according to the proportions of each specification determined by the target mix design results. The target mix design used in this embodiment is shown in Table 1.

[0048] Table 1 Target mix proportions of asphalt mixtures in the examples

[0049] Sieve aperture size / mm 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Quality pass rate / % 100 92 76 49 33.5 23.5 17 11 9.5 6

[0050] Step 2: The passing rate of the key sieve holes of the aggregate mixture described in Step 1 is obtained through sieving tests, as shown in Table 2.

[0051] Table 2 shows the key sieve aperture passing rates obtained from the aggregate mixture screening test in the example.

[0052] Sieve aperture size / mm 9.5 4.75 2.36 0.075 Quality pass rate / % 78 45 34.5 5.9

[0053] Sieve analysis of asphalt mixtures is used to determine the distribution of aggregates of different sizes within the asphalt mixture. In sieve analysis, the sieve pass rate refers to the proportion of aggregates of a specific size that can pass through the sieve, usually expressed as a percentage. It is one of the important parameters for evaluating aggregate distribution. For example, if 100g of aggregate passes through a 4.75mm sieve, and the total aggregate volume is 200g, then the 4.75mm sieve pass rate is 50%. The critical sieve pass rate refers to the pass rate of sieve openings that have a critical impact on the aggregate composition of the asphalt mixture. Its determination is crucial, as it provides mix design parameters to guide engineering design and quality control.

[0054] For asphalt mixtures with a maximum nominal particle size less than or equal to 26.5 mm, the key sieve openings are 9.5 mm, 4.75 mm, 2.36 mm, and 0.075 mm. The corresponding aggregate specifications are: 10-20 mm aggregate, 5-10 mm aggregate, 0-5 mm aggregate, and mineral powder.

[0055] For asphalt mixtures with a maximum nominal particle size greater than 26.5 mm, the key sieve openings are 19 mm, 9.5 mm, 4.75 mm, 2.36 mm, and 0.075 mm. The corresponding aggregate specifications are: 20–30 mm aggregate, 10–20 mm aggregate, 5–10 mm aggregate, 0–5 mm aggregate, and mineral powder.

[0056] According to Table 1, the maximum nominal particle size of the asphalt mixture involved in this embodiment is less than 26.5 mm, and the key sieve openings should be 0.075 mm, 2.36 mm, 4.75 mm, and 9.5 mm. The corresponding aggregate specifications are mineral powder, 0-5 mm aggregate, 5-10 mm aggregate, and 10-20 mm aggregate, respectively. P1, P2, P3, and P4 need to be calculated. Based on Tables 1 and 2, P1, P2, P3, and P4 are calculated as follows:

[0057]

[0058]

[0059]

[0060]

[0061] Step 3: According to the calculation results of P1, P2, P3 and P4 in this embodiment, the absolute value of P3 is greater than 5%. Therefore, it is necessary to calculate the correction coefficient α3 of the cold material hopper feeding speed of the aggregate corresponding to P3 (i.e., 5-10mm aggregate) (the moisture content of 5-10mm aggregate in this embodiment is 2.7%).

[0062] α3=-(1+w3)P3=-(1+2.7%)×(-8.1%)=8.3%

[0063] Since α3 is a positive value, the feeding speed of the 5-10mm aggregate cold hopper needs to be increased by 8.3%. After adjusting the feeding speed of the cold hopper, step two is repeated, and the passing rate of the key sieve holes of the aggregate mixture after the feeding speed correction is obtained through screening test, as shown in Table 3.

[0064] Table 3 shows the key sieve pass rates obtained from the aggregate mixture screening test after the feed rate was corrected in the example.

[0065] Sieve aperture size / mm 9.5 4.75 2.36 0.075 Quality pass rate / % 78 48.6 34.8 6

[0066] When the absolute values ​​of P1, P2, P3, and P4 are all found to be less than 5% after recalculation, proceed to step four.

[0067] Step 4: Place the precast iron test mold in a hardened, flat open space. The top of the test mold should be flush with the ground. Add m matching iron pads inside the test mold so that the height inside the test mold is the same as the thickness of the corresponding asphalt surface layer.

[0068] For asphalt mixtures with a maximum nominal particle size of less than or equal to 26.5 mm, the size of the iron test mold is 500 mm × 500 mm × 80 mm, and the size of the iron spacer is 499 mm × 499 mm × 10 mm.

[0069] For asphalt mixtures with a maximum nominal particle size greater than 26.5 mm, the iron test mold size is 800 mm × 800 mm × 150 mm, and the iron spacer size is 799 mm × 799 mm × 10 mm.

[0070] In this embodiment, the maximum nominal particle size of the asphalt mixture is less than 26.5mm. Therefore, the iron mold should be 500mm × 500mm × 80mm, and the iron spacer blocks should be 499mm × 499mm × 10mm. After determining the mold and spacer block specifications, the iron mold should be placed in a hardened, flat open space, with the top of the mold flush with the ground. Since the asphalt surface layer thickness in this embodiment is 5cm, m = 3 spacer blocks need to be added to the mold to ensure that the height inside the mold matches the corresponding asphalt surface layer thickness.

[0071] Step 5: Mix the aggregate mixture obtained in Step 3 with the target mix proportion and the optimal asphalt content to obtain the asphalt mixture. In this embodiment, the Matsuura coefficient is a = 1.1, the number of inner pads in the mold is m = 3, and the mold height is h = 80 mm. Therefore, the calculated loading height H is:

[0072] H=a×(h-10×m)=1.1×(80-10×3)=55(mm)

[0073] After determining H, fill the prepared asphalt mixture into the test mold described in step four until it reaches 55mm. During filling, avoid adding more material or manual compaction.

[0074] Step Six: Compact the asphalt mixture that has been loaded into the test mold as described in Step Five according to the compaction equipment and compaction scheme used in actual construction.

[0075] Step 7: Determine the compaction degree, texture depth, and permeability coefficient of the rolled asphalt mixture sample, and take core samples to test the Marshall stability. Simultaneously, laterally cut open the cored asphalt mixture sample and randomly select five sections with dimensions of 40mm×40mm (corresponding to a 500mm×500mm×80mm mold) or 80mm×80mm (corresponding to an 800mm×800mm×150mm mold). Calculate the section uniformity coefficient to check for segregation. If all indicators meet the technical requirements, the production mix design is complete; if not, adjust the proportions of each aggregate specification at 1% intervals and repeat steps 4 to 7 until the requirements are met.

[0076] In this embodiment, since the mold used is 500mm×500mm×80mm, the selected cross-sectional dimensions are 40mm×40mm, and the number of coarse aggregates in the five cross-sections are 19, 16, 21, 18, and 19, respectively. The Marshall stability, compaction degree, texture depth, and permeability coefficient of the core samples can all be determined according to standard methods. The cross-sectional uniformity coefficient is calculated using the following formula:

[0077]

[0078] The technical requirements are shown in Table 4. The test results of the asphalt mixture samples involved in this embodiment are shown in Table 5. Comparing Table 4 and Table 5, it can be seen that all indicators of the asphalt mixture samples involved in this embodiment meet the technical requirements, and there is no need to adjust the proportion of aggregates of various specifications or repeat steps four to seven to complete the production mix design.

[0079] Table 4 Technical Requirements for Asphalt Mixture Samples

[0080]

[0081] Table 5. Test results of asphalt mixture samples in this embodiment.

[0082]

[0083] In summary, the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Based on the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of the present invention is not limited to the contents of the specification; all equivalent variations and modifications of the shape, structure, features, and spirit described within the scope of the claims should be included within the scope of the claims.

Claims

1. A method for designing the mix proportions of hot-mix asphalt mixtures considering construction factors, characterized in that... Includes the following steps: Step 1: Take samples from each hot aggregate bin according to the target mix ratio and mix the aggregate mixture. Step 2: Obtain the passing rate of key sieve openings in the aggregate mixture through sieving tests, and calculate the mass deviation of each aggregate specification. P 1. P 2. P 3. P 4. P 5, （1） （2） （3） （4） （5） In the formula: T 0.075 , T 2.36 , T 4.75 , T 9.5 , T 19 The values ​​represent the passing rates of the aggregate mixture through sieves with apertures of 0.075mm, 2.36mm, 4.75mm, 9.5mm, and 19mm, respectively, in percentage terms. S 0.075 , S 2.36 , S 4.75 , S 9.5 , S 19 The values ​​represent the passing rates of the target mix proportions at sieve openings of 0.075mm, 2.36mm, 4.75mm, 9.5mm, and 19mm, respectively, in percentage terms. P 1. P 2. P 3. P 4. P 5 represents the quality deviation of mineral powder, 0-5mm aggregate, 5-10mm aggregate, 10-20mm aggregate, and 20-30mm aggregate, respectively, in percentages (%). Step 3, when P i If the absolute values ​​are all less than 5%, proceed to step four; otherwise, use formula 6 to adjust the feeding speed of each cold material bin, and repeat steps one through three until... P i All less than 5%, （6） In the formula, α i For the first i The correction factor for the cold silo feeding speed corresponding to a certain aggregate specification, expressed as a percentage, indicates that when the value is positive, the corresponding cold silo feeding speed should be increased. α i Conversely, it decreases. α i ; w i For the first i Moisture content of aggregates of various specifications, in %. P i For the first i The mass deviation of aggregate of various specifications is expressed in % %. i It is a natural number less than or equal to 5; Step 4: Place the test mold in a hardened, flat open space with the top of the mold flush with the ground. Add [something] into the test mold. m The matching iron pads ensure that the height inside the test mold is the same as the corresponding thickness of the asphalt surface layer. Step 5: Mix the aggregate mixture obtained in Step 3 with the target mix ratio and the optimal asphalt content to obtain an asphalt mixture. Pour the mixed asphalt mixture into the test mold described in Step 4 until the specified filling height is reached. H Calculated according to Formula 7, （7） In the formula, H This refers to the loading height, in mm. a The loose paving coefficient used in actual construction; h This refers to the height of the trial mold, in mm. m This refers to the number of pads inside the trial mold; Step 6: Compact the asphalt mixture that has been loaded into the test mold as described in Step 5 according to the compaction equipment and compaction plan used in actual construction. Step 7: Determine the compaction degree, texture depth, and permeability coefficient of the asphalt mixture sample after compaction, and take core samples to test whether the Marshall stability and profile uniformity coefficient of the core samples meet the technical requirements; if the technical requirements are met, complete the production mix design; if the technical requirements are not met, adjust the proportion of each aggregate specification at 1% intervals, and repeat steps 4 to 7 until the requirements are met. In step seven, the asphalt mixture sample after core drilling is laterally cut open, five sections are randomly selected, and the section uniformity coefficient is calculated according to formula (8). （8） In the formula: β The coefficient for profile uniformity; n k For the first k The number of coarse aggregates in a representative profile k It is a natural number less than or equal to 5; The average number of coarse aggregates in five representative cross-sections; the coarse aggregates refer to aggregates with a particle size greater than 4.75 mm.

2. The method for designing the mix proportion of hot-mix asphalt mixture production considering construction factors according to claim 1, characterized in that: In step two, the key sieve openings for asphalt mixtures with a maximum nominal particle size less than or equal to 26.5 mm are 0.075 mm, 2.36 mm, 4.75 mm, and 9.5 mm, corresponding to aggregate specifications of mineral powder, 0-5 mm aggregate, 5-10 mm aggregate, and 10-20 mm aggregate, respectively.

3. The method for designing the mix proportion of hot-mix asphalt mixtures considering construction factors according to claim 1, characterized in that: In step two, the key sieve openings for asphalt mixtures with a maximum nominal particle size greater than 26.5 mm are 0.075 mm, 2.36 mm, 4.75 mm, 9.5 mm, and 19 mm, corresponding to aggregate specifications of mineral powder, 0-5 mm aggregate, 5-10 mm aggregate, 10-20 mm aggregate, and 20-30 mm aggregate, respectively.

4. The method for designing the mix proportion of hot-mix asphalt mixture considering construction factors according to claim 1, characterized in that: In step four, the mold size for asphalt mixtures with a maximum nominal particle size of less than or equal to 26.5 mm is 500 mm × 500 mm × 80 mm, and the size of the iron pad is 499 mm × 499 mm × 10 mm.

5. The method for designing the mix proportion of hot-mix asphalt mixture production considering construction factors according to claim 1, characterized in that: In step four, the iron mold size for asphalt mixtures with a maximum nominal particle size greater than 26.5 mm is 800 mm × 800 mm × 150 mm, and the iron pad size is 799 mm × 799 mm × 10 mm.

6. The method for designing the mix proportion of hot-mix asphalt mixture considering construction factors according to claim 1, characterized in that: In step seven: The technical requirements for the profile uniformity coefficient are: less than or equal to 0.20 for densely mixed asphalt mixtures and less than or equal to 0.15 for asphalt mastic macadam mixtures; The technical requirements for the construction depth are: for both densely packed asphalt mixtures and asphalt mastic macadam mixtures, the depth should be greater than or equal to 1.0 mm and less than or equal to 1.2 mm.

7. The method for designing the mix proportion of hot-mix asphalt mixture production considering construction factors according to claim 1, characterized in that: When the test mold is 500mm×500mm×80mm, the selected cross-sectional dimensions are 40mm×40mm.

8. The method for designing the mix proportion of hot-mix asphalt mixture production considering construction factors according to claim 1, characterized in that: When the test mold is 800mm×800mm×150mm, the selected cross-sectional dimensions are 80mm×80mm.

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