Aggregate gradation design method, asphalt mixture design method and pavement structure

Abstract

The present application relates to aggregate gradation design method, asphalt mixture design method and pavement structure, comprising the following steps: sequentially determining the optimum dosage of each aggregate, the dosage determination method of adjacent two aggregates is: determining the average particle size ratio of fine aggregate and coarse aggregate in adjacent two aggregates; when the average particle size ratio is not greater than the set value, the first void index under a plurality of different coarse aggregate volume contents is measured, the boundary effect model is determined according to the first void index, the second void index when the coarse aggregate volume content is 100% is measured, the non-interference effect model is determined according to the second void index, and the optimum coarse aggregate dosage is determined according to the boundary effect model and the non-interference effect model; when the average particle size ratio is greater than the set value, the CBR value under a plurality of different coarse aggregate contents is measured, and the coarse aggregate volume content corresponding to the maximum CBR value is taken as the optimum coarse aggregate dosage, the aggregate gradation obtained by the design method satisfies the mineral material gap rate requirement.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to aggregate gradation design methods, asphalt mixture design methods, and pavement structures. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Currently, basalt SMA-type asphalt concrete is widely used for the surface layer of high-grade pavements. Basalt SMA-type asphalt concrete has a dense, discontinuously gradable skeleton structure with a rough surface texture and excellent skid resistance. It also boasts high strength and strong rutting resistance, making it the preferred choice for the surface layer of high-grade pavements. However, the inventors have discovered that with the continued surge in the construction, maintenance, and expansion of high-grade highways, the demand for aggregates is gradually increasing. The production of basalt, required for the surface layer of high-grade highways, is severely insufficient. Many highways are forced to procure basalt from other regions due to this shortage, resulting in extended construction periods and increased construction costs. Limestone production is sufficient to meet the current needs of highway construction, maintenance, and expansion. However, when limestone aggregates are used in SMA-type asphalt concrete, the traditional gradation design method results in a void ratio (VMA) that fails to meet requirements due to boundary and interference effects. Therefore, how to design the gradation of limestone aggregates to meet the void ratio requirements is an urgent problem to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide an aggregate gradation design method that ensures that when limestone is used as aggregate in dense asphalt mixtures, its gradation meets the requirements for aggregate void ratio.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide an aggregate gradation design method, comprising the following steps:

[0007] The optimal dosage of each aggregate grade is determined according to its particle size from largest to smallest. The average particle size ratio of the lowest aggregate grade to the aggregate grade above it should not exceed a set value. The dosage of adjacent aggregate grades is determined as follows:

[0008] Determine the average particle size ratio of fine and coarse aggregates in two adjacent aggregate grades;

[0009] When the average particle size ratio is not greater than the set value, the first void index is measured at multiple different coarse aggregate volume contents. The boundary effect model is determined based on the first void index. The second void index is measured when the coarse aggregate volume contents are 100%. The non-interference effect model is determined based on the second void index. The optimal coarse aggregate dosage is determined based on the boundary effect model and the non-interference effect model.

[0010] When the average particle size ratio is greater than the set value, the CBR value is measured at multiple different coarse aggregate contents, and the coarse aggregate volume content corresponding to the largest CBR value is taken as the optimal coarse aggregate dosage.

[0011] Optionally, the first void index is determined at coarse aggregate volume contents of 0%, 10%, and 20%, and the boundary effect model is determined based on the three first void indices.

[0012] Optionally, the coarse aggregate volume content is taken at 10% intervals to measure the CBR value at different coarse aggregate volume contents.

[0013] Optionally, the setting value is 0.2.

[0014] Optionally, the optimal coarse aggregate dosage is the coarse aggregate volume content corresponding to the intersection of the straight lines of the non-interference effect model and the boundary effect model.

[0015] Optionally, after the optimal amount of coarse aggregate in the current two aggregate grades is determined, the current two aggregate grades are mixed according to the obtained optimal amount of coarse aggregate to form a new coarse aggregate, which is then used for gradation design with the next grade of aggregate, which is to be used as fine aggregate.

[0016] Secondly, embodiments of the present invention provide an asphalt mixture design method, comprising the following steps:

[0017] The proportion of each grade of aggregate in the aggregate is determined by the aggregate gradation design method described in the first aspect;

[0018] Select the initial asphalt dosage and multiple mineral powder dosages, and prepare multiple sets of first Marshall specimens corresponding to different mineral powder dosages in combination with aggregates;

[0019] Density tests were conducted using the first Marshall specimen to obtain the mineral void ratio of multiple sets of the first Marshall specimens;

[0020] The ratio of mineral powder to aggregate is determined based on the obtained mineral void ratio;

[0021] Multiple sets of asphalt dosages were set, and multiple sets of second Marshall specimens were prepared in combination with the determined ratio of mineral powder to aggregate.

[0022] Density and Marshall tests were conducted using the second Marshall specimen. The optimal asphalt content was determined based on the obtained void ratio, aggregate void ratio, coarse aggregate skeleton void ratio, asphalt saturation, and stability.

[0023] Thirdly, embodiments of the present invention provide a road structure comprising, from top to bottom, an asphalt concrete upper layer, an asphalt concrete lower layer, a stress-absorbing layer, and a water-stabilized base course, wherein the proportions of aggregates, mineral powder, and asphalt used in the asphalt concrete upper layer are obtained using the asphalt mixture design method described in the second aspect.

[0024] Optionally, in the asphalt concrete lower layer, the mass ratio of coarse aggregate, medium aggregate, fine aggregate, and mineral powder is 34-38:25-29:33-37:1-3, preferably 36:27:35:2, with the remainder being asphalt. The mass of asphalt accounts for 4%-5% of the total mass of the asphalt concrete lower layer, preferably 4.3%.

[0025] Furthermore, in the asphalt concrete lower layer, the coarse aggregate has a particle size range of 10-20mm, excluding the 10mm endpoint; the medium aggregate has a particle size range of 5-10mm, excluding the 5mm endpoint; and the fine aggregate has a particle size range of 0-5mm, excluding the 0mm endpoint.

[0026] Optionally, in the stress-absorbing layer, the mass ratio of coarse aggregate, fine aggregate, and mineral powder is 13-15:80-82:4-6, preferably 14:81:5, with the remainder being asphalt, and the asphalt mass accounting for 8%-10% of the total mass of the stress-absorbing layer, preferably 9.0%.

[0027] Furthermore, in the stress-absorbing layer, the coarse aggregate has a particle size range of 3-5 mm, excluding the 3 mm endpoint, and the fine aggregate has a particle size range of 0-3 mm, excluding the 0 mm endpoint.

[0028] Optionally, the water-stabilized base course is a cement-stabilized crushed stone base course determined by the vertical vibration molding method.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. The gradation design method of the present invention, since the particle size ratio of the two smallest aggregate grades is less than the set value, determines the optimal amount of coarse aggregate based on the boundary effect model and the non-interference effect model, thereby eliminating the influence of interference effect on the aggregate void ratio, and thus forming a dense interlocking skeleton structure. The asphalt mixture formed by the aggregate prepared according to the designed gradation with mineral powder and asphalt meets the requirements of aggregate void ratio, and has the characteristics of high density, high stiffness modulus, good fatigue resistance and good skid resistance. It is suitable for limestone to be used in asphalt mixtures, which helps to improve the service life of asphalt pavement and reduce the raw material cost of pavement construction.

[0031] 2. The pavement structure of the present invention, wherein the asphalt concrete surface layer is designed using the gradation design method of the present invention, and together with the asphalt concrete base layer, stress-absorbing layer, and water-stabilized base course, can effectively prevent the generation of rutting on the pavement. The water-stabilized base course uses cement-stabilized crushed stone base course, which can reduce the generation of base course cracks and improve base course performance. The stress-absorbing layer can effectively prevent base course cracks from extending to the surface layer and reduce the generation of pavement reflective cracks. This pavement structure combination specifically solves pavement defects and improves pavement performance. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 This is a flowchart of the aggregate gradation design method in Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram illustrating the principle of determining the optimal amount of coarse aggregate in the gradation design method of Embodiment 1 of the present invention.

[0035] Figure 3 This is a schematic diagram of the road surface structure in Embodiment 3 of the present invention; Detailed Implementation

[0036] For ease of description, the use of the words "upper" and "lower" in this invention only indicates that they are consistent with the upper and lower directions of the accompanying drawings and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Example 1

[0038] This embodiment provides a method for aggregate gradation design, wherein the aggregate is limestone. During the design process, as follows... Figure 1 As shown, according to particle size d 50（i） The aggregates are divided into n grades from largest to smallest, namely grade 1, grade 2... grade n, where the average particle size d of grade n aggregates is... 50（n） Minimum, average particle size d of grade 1 aggregate 50（1） The maximum, where the average particle size ratio d of aggregates in grades n and n-1 is the largest. 50（n） / d 50（n-1） It should not exceed a set value; in this embodiment, the set value is 0.2.

[0039] The specific design method includes the following steps:

[0040] Step 1: First, determine the proportion of grade 1 and grade 2 aggregates, where grade 1 aggregate is used as coarse aggregate and grade 2 aggregate is used as fine aggregate. This includes the following steps:

[0041] Step a: Obtain the average particle size d of grade 1 and grade 2 aggregates. 50（1） and d 50（2） The average particle size ratio of grade 2 aggregate and grade 1 aggregate is calculated. In this embodiment, the average particle size of grade 1 aggregate and grade 2 aggregate can be obtained by existing screening test methods, which will not be described in detail here.

[0042] Step b: Based on the average particle size ratio obtained in step a, obtain the volume content ratio of grade 1 aggregate and grade 2 aggregate.

[0043] b. 1: When the average particle size ratio of grade 1 aggregate and grade 2 aggregate is not greater than 0.2, the optimal dosage of grade 1 aggregate shall be obtained according to the following method:

[0044] Step (1): The void index of coarse aggregate at different volume contents is determined by rotary compaction test. The volume content of coarse aggregate refers to the ratio of the volume of grade 1 aggregate to the total volume of grade 1 and grade 2 aggregates. In this embodiment, three samples are selected, and the volume contents of coarse aggregate (grade 1 aggregate) in the three samples are 0%, 10%, and 20%, respectively. The three volume contents of 0%, 10%, and 20% are selected to ensure that all three volume contents are less than the optimal volume content of coarse aggregate. Rotary compaction test is performed on the three groups of samples to obtain the void index e of the three samples, and then the boundary effect model is determined. The boundary effect model is as follows:

[0045]

[0046] Where e is the measured void index, F is the void index of fine aggregate (i.e., grade 2 aggregate), D is the boundary effect coefficient, and p is the volume content of coarse aggregate. In this embodiment, F and D can be obtained by measuring the three void indices e and their corresponding coarse aggregate content p, and then the boundary effect model can be obtained.

[0047] Step (2): Using a rotary compaction test, the void index e is determined when the coarse aggregate volume content is 100%, and then the interference-free effect model is obtained, specifically:

[0048]

[0049] Where e is the void index measured in step (2), p is the volume content of coarse aggregate, and thus the void index C of coarse aggregate can be obtained, and thus the interference-free model can be obtained.

[0050] The purpose of determining the void index when the coarse aggregate content is 100% is to ensure that the coarse aggregate content of the specimen used to measure the void index is definitely greater than the optimal coarse aggregate content.

[0051] Step (3): Obtain the optimal amount of coarse aggregate, i.e., grade 1 aggregate, through the boundary effect model and the non-interference effect model, i.e., the optimal volume content.

[0052] like Figure 2 As shown in this embodiment, the volume content of coarse aggregate corresponding to the intersection of the straight lines of the non-interference effect model and the boundary effect model is the optimal amount of coarse aggregate.

[0053] Right now

[0054] Where P t This represents the optimal dosage of coarse aggregate, i.e., the optimal volume content.

[0055] b.2: When the average particle size ratio of grade 1 aggregate to grade 2 aggregate is greater than 0.2, the aggregate cannot satisfy the interference-free effect model and the boundary effect model. The optimal amount of grade 1 aggregate should be obtained according to the following method:

[0056] Multiple aggregate samples with different coarse aggregate volume contents were prepared, with the coarse aggregate volume contents being prepared at 10% intervals. Then, a bearing ratio test (CBR) was conducted on multiple aggregate samples, and a fitting curve between aggregate content and CBR was established. The coarse aggregate volume contents corresponding to the maximum CBR value were taken as the optimal amount of coarse aggregate.

[0057] By using steps a and b, the optimal volume content of grade 1 aggregate can be determined, which means the ratio of grade 1 aggregate to grade 2 aggregate can be determined.

[0058] Step 2: Determine the mix ratio of grade 3 aggregate and grade 1 and 2 aggregate. Mix grade 1 and 2 aggregate according to the mix ratio obtained in step b, and then use it as the new coarse aggregate. Then determine the mix ratio of grade 3 aggregate as fine aggregate.

[0059] In this embodiment, the aggregate resulting from the mixture of grade 1 and grade 2 aggregates is defined as grade A aggregate, which is used as coarse aggregate, and grade 3 aggregate is used as fine aggregate. The method for determining the optimal dosage of grade 3 aggregate includes the following steps:

[0060] Step A: Obtain the average particle size of the three aggregate grades; any existing method can be used. Then, obtain the average particle size ratio between the three aggregate grades and the two aggregate grades.

[0061] Step B: Based on the average particle size ratio obtained in Step A, obtain the volume content ratio of grade 3 aggregate and grade A aggregate.

[0062] Step B.1: When the average particle size ratio of grade 3 aggregate and grade 2 aggregate is not greater than 0.2, obtain the optimal amount of grade A aggregate according to the method steps in b.1, and then obtain the volume content of grade A aggregate and grade 3 aggregate. Since the volume content of grade 1 aggregate and grade 2 aggregate in grade A aggregate is determined, the volume content of grade 1, 2 and 3 aggregate can be obtained.

[0063] Step B.2 When the average particle size ratio of grade 3 aggregate and grade 2 aggregate is greater than 0.2, obtain the optimal amount of grade A aggregate according to the method steps in b.2, and then obtain the volume content of grade A aggregate and grade 3 aggregate. Since the volume content of grade 1 aggregate and grade 2 aggregate in grade A aggregate is determined, the volume content of grade 1, 2 and 3 aggregate can be obtained.

[0064] For example, if the volume ratio of grade 1 aggregate to grade 2 aggregate obtained through step 1 is 7:3, and the volume ratio of grade A aggregate to grade 3 aggregate obtained through step 2 is 8:2, then the volume ratio of grade 1 aggregate, grade 2 aggregate, and grade 3 aggregate is 5.6:2.4:2.

[0065] Step 3: Mix aggregates of grades 1, 2, and 3 according to the volume content obtained in step 2 to form coarse aggregates, and aggregate grade 4 as fine aggregates. Use the same method to determine the volume content of aggregate grade 4, and then iterate through the above steps to obtain the optimal amount of each aggregate grade.

[0066] In this embodiment, since the average particle size ratio of aggregates in grade n and grade n-1 is not greater than 0.2, the method described in b.1 is definitely used to determine the optimal amount of aggregate in grade n. Therefore, the final gradation design determines the optimal amount of coarse aggregate based on the boundary effect model and the non-interference effect model, thereby eliminating the influence of interference effect and boundary effect on the aggregate void ratio, and thus forming a dense and interlocked skeleton structure. The asphalt mixture formed by the aggregate prepared according to the gradation design of this embodiment with mineral powder and asphalt meets the requirements of aggregate void ratio, and has the characteristics of high density, high stiffness modulus, good fatigue resistance and good skid resistance. It is suitable for limestone to be used in asphalt mixtures, which helps to improve the service life of asphalt pavement and reduce the raw material cost of pavement construction.

[0067] Using the gradation design method of this embodiment, limestone can be used instead of basalt to prepare asphalt mixtures with performance comparable to basalt SMA asphalt mixtures. The price difference between limestone and high-quality basalt is about 120 yuan per ton, which means that 100,800 yuan can be saved per kilometer for a two-way four-lane road.

[0068] Example 2

[0069] This embodiment provides a design method for asphalt mixtures, wherein the asphalt mixture is composed of aggregates, mineral powder, and asphalt, and the aggregates used are limestone aggregates. The method includes the following steps:

[0070] Step 1: Obtain the aggregate gradation. In this embodiment, the method of Example 1 is used to obtain the amount of each grade of aggregate.

[0071] Step 2: Obtain the mass ratio of aggregate to mineral powder. The mineral powder used is finely ground limestone powder, including the following steps:

[0072] Step 2.1: Weigh the set mass of aggregate, wherein the aggregate is a mixture of multiple aggregates according to the proportion obtained by the method in Example 1.

[0073] Step 2.2: Based on the aggregate quality in Step 2.1 and the mass ratio of multiple sets of mineral powder, one set of preliminary asphalt to aggregate set set by the user, weigh multiple sets of mineral powder and one set of preliminary asphalt.

[0074] The quality of mineral powder and initial test asphalt is determined manually based on experience. In this embodiment, three different qualities of mineral powder are selected.

[0075] Step 2.3: Prepare three sets of first Marshall specimens with the three different qualities of mineral powder, the corresponding aggregates, and the initial test asphalt. The only difference between the three sets of first Marshall specimens is the quality of the mineral powder.

[0076] Step 2.4: Density tests were conducted using three sets of first Marshall specimens to obtain the void ratio (VMA) of the aggregate in the three sets of first Marshall specimens.

[0077] Step 2.5: Compare the aggregate void ratio VMA obtained in Step 2.4 with the set aggregate void ratio VMA. * Compare and select the one with VMA greater than VMA. * The corresponding mineral powder quality is taken as the optimal mineral powder quality, and thus the mass ratio of mineral powder to aggregate can be obtained.

[0078] Among them, the mineral aggregate void ratio VMA * The ratio R of the passing rates of adjacent particle sizes can be calculated using the following steps:

[0079] 1. Calculate and determine the passing rate of different particle sizes based on different amounts of ore and screening results.

[0080] 2. Starting from the largest particle size, calculate the ratio Ri of the throughput of the larger particle size to the throughput of the smaller particle size among all adjacent particle sizes.

[0081] 3. Determine the interference coefficient Fa for different R values ​​according to the table below. If the R value is not in the table, determine the interference coefficient value by linear interpolation.

[0082] 4. Calculate the void ratio VMA of the aggregate according to formula (2).* .

[0083] (2)

[0084] Where: VMA0—the gap ratio of a single-size mineral material in its most compact state, taken as 26%;

[0085] Fa – Interference coefficient;

[0086] n – Total number of levels, which is the number of mineral particle sizes minus 1.

[0087]

[0088] The above steps can be performed using existing methods, and their detailed technical features will not be described in detail here.

[0089] Step 3: Determine the optimal amount of asphalt to use.

[0090] Specifically, based on the aggregate void ratio results obtained in step 2, with an interval of 0.2%-0.4%, multiple asphalt contents are adjusted to prepare multiple sets of second Marshall specimens. Then, density tests and Marshall tests are conducted. Based on the obtained void ratio, aggregate gap ratio, coarse aggregate skeleton gap ratio, asphalt saturation, and stability, the mass ratio of asphalt to aggregate and mineral powder is determined.

[0091] The optimal quality of asphalt should meet the following requirements:

[0092]

[0093] Among them, VCA DRC The loose packing gap ratio of coarse aggregate under compacted conditions is a known quantity obtained in advance.

[0094] The asphalt quality that meets the requirements of the table above is selected as the optimal asphalt quality, and then the mass ratio of aggregate, mineral powder and asphalt is determined.

[0095] The asphalt mixture prepared using the proportions designed in this embodiment meets the following technical requirements:

[0096]

[0097] Example 3

[0098] This embodiment provides a road surface structure, such as Figure 3 As shown, it includes, from top to bottom, an asphalt concrete top layer, an asphalt concrete bottom layer, a stress-absorbing layer, and a water-stabilized base layer.

[0099] The mass ratio of limestone aggregate, mineral powder and asphalt in the asphalt concrete surface layer was obtained using the method shown in Example 2.

[0100] The asphalt concrete lower layer shown uses AC-20 mixture. According to the requirements of the "Technical Specification for Construction of Highway Asphalt Pavement" (JTGF40-2004) on the gradation range of AC-20 aggregate, the aggregate gradation composition is designed.

[0101] Specifically, AC-20 mixture was used in accordance with the requirements of the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004), with 5 asphalt-aggregate ratios set at 0.3% intervals, and the optimal asphalt content was determined according to the Marshall method.

[0102] The above method can be achieved using existing methods, and its specific steps will not be described in detail here.

[0103] Furthermore, the mix design technical requirements and mixture performance test indicators for the AC-20 asphalt concrete lower layer are as follows:

[0104]

[0105]

[0106] In this embodiment, the mix proportions of the lower layer of asphalt concrete are as follows:

[0107] In the asphalt concrete base course, the mass ratio of coarse aggregate, medium aggregate, fine aggregate, and mineral powder is 34-38:25-29:33-37:1-3, preferably 36:27:35:2, with the remainder being asphalt. The asphalt mass accounts for 4%-5% of the total mass of the asphalt concrete base course, preferably 4.3%.

[0108] In the asphalt concrete lower layer, the coarse aggregate has a particle size range of 10-20mm, excluding the 10mm endpoint; the medium aggregate has a particle size range of 5-10mm, excluding the 5mm endpoint; and the fine aggregate has a particle size range of 0-5mm, excluding the 0mm endpoint.

[0109] The stress-absorbing layer mixture adopts an AC-5 gradation design and should meet the requirements of the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0110] Furthermore, based on engineering experience, the stress-absorbing asphalt mixture AC-5 is selected with an appropriate asphalt content range, generally 8.0%~9.5%, and 4~5 different asphalt contents are selected at intervals of 0.3%~0.5% to form specimens using a rotary compactor.

[0111] The above test methods can be achieved using existing test methods, and the specific steps will not be described in detail here.

[0112] Furthermore, the mix design technical requirements for stress-absorbing asphalt mixture AC-5 are as follows:

[0113]

[0114] In this embodiment, the mass ratio of coarse aggregate, fine aggregate, and mineral powder in the stress-absorbing layer is 13-15:80-82:4-6, preferably 14:81:5, and the remainder is asphalt, with the asphalt mass accounting for 8%-10% of the total mass of the stress-absorbing layer, preferably 9.0%.

[0115] Furthermore, in the stress-absorbing layer, the coarse aggregate has a particle size range of 3-5 mm, excluding the 3 mm endpoint, and the fine aggregate has a particle size range of 0-3 mm, excluding the 0 mm endpoint.

[0116] The water-stabilized base course uses cement-stabilized crushed stone base course and adopts a vertical vibration molding method to reduce the amount of cement used, thereby effectively reducing the generation of base course cracks. The compressive strength is increased by more than 30% compared with traditional water-stabilized crushed stone, and the amount of cement used is reduced by about 25%.

[0117] In this embodiment, during the construction of the pavement structure, the thickness of the asphalt concrete surface layer is 2cm-4cm, and the dynamic stability of the mixture is not less than 3500 cycles / mm. The thickness of the asphalt concrete base layer is 12cm-14cm, and the dynamic stability is not less than 5000 cycles / mm. The thickness of the stress-absorbing layer is 2cm, and the porosity is 0.5%~3%. The thickness of the water-stabilized base course is 40cm-50cm.

[0118] During construction, the depth of foundation treatment shall be determined based on the current foundation conditions, traffic volume and preliminary pavement structure calculations. The subgrade construction shall meet the requirements of the "Technical Specification for Highway Subgrade Construction" (JTG / T 3610-2019).

[0119] The construction of the asphalt concrete surface layer shall be carried out in accordance with the requirements for SMA asphalt mixture in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0120] The construction of the lower layer of asphalt concrete shall be carried out in accordance with the requirements for modified asphalt mixtures in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0121] The construction of the stress-absorbing layer shall be carried out in accordance with the requirements for the lower sealing layer in the "Technical Specification for Construction of Asphalt Pavement of Highway" (JTG F40-2004).

[0122] The construction of water-stabilized base courses shall be carried out in accordance with the relevant requirements of the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / T F20-2015).

[0123] Before paving the road surface structure, the subgrade should be reinforced to increase the resilient modulus of the top surface of the subgrade. If the subgrade strength is insufficient, an additional granular layer can be added to its top surface.

[0124] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An aggregate gradation design method, characterized in that, Includes the following steps: The optimal dosage of each aggregate grade is determined according to its particle size from largest to smallest. The average particle size ratio of the lowest aggregate grade to the aggregate grade above it should not exceed a set value. The dosage of adjacent aggregate grades is determined as follows: Determine the average particle size ratio of fine and coarse aggregates in two adjacent aggregate grades; When the average particle size ratio is not greater than the set value, the first void index is measured at multiple different coarse aggregate volume contents. The boundary effect model is determined based on the first void index. The second void index is measured when the coarse aggregate volume contents are 100%. The non-interference effect model is determined based on the second void index. The optimal coarse aggregate dosage is determined based on the boundary effect model and the non-interference effect model. When the average particle size ratio is greater than the set value, the CBR value is measured at multiple different coarse aggregate contents, and the coarse aggregate volume content corresponding to the largest CBR value is taken as the optimal coarse aggregate dosage.

2. The aggregate gradation design method as described in claim 1, characterized in that, The first void index was determined when the volume content of coarse aggregate was 0%, 10%, and 20%, and the boundary effect model was determined based on the three first void indices.

3. The aggregate gradation design method as described in claim 1, characterized in that, The CBR value was measured at 10% intervals for the coarse aggregate volume content.

4. The aggregate gradation design method as described in claim 1, characterized in that, The set value is 0.

2.

5. The aggregate gradation design method as described in claim 1, characterized in that, The optimal amount of coarse aggregate is the coarse aggregate content corresponding to the intersection of the straight lines in the non-interference effect model and the boundary effect model.

6. The aggregate gradation design method as described in claim 1, characterized in that, Once the optimal amount of coarse aggregate for the two current aggregate grades is determined, the two current aggregate grades are mixed according to the obtained optimal amount of coarse aggregate to form a new coarse aggregate, which is then used for gradation design with the next grade of aggregate, which is to be used as fine aggregate.

7. A method for designing asphalt mixtures, characterized in that, Includes the following steps: The proportion of each grade of aggregate in the aggregate is determined by the aggregate gradation design method according to any one of claims 1-6; Select the initial asphalt dosage and multiple mineral powder dosages, and prepare multiple sets of first Marshall specimens corresponding to different mineral powder dosages in combination with aggregates; Density tests were conducted using the first Marshall specimen to obtain the mineral void ratio of multiple sets of the first Marshall specimens; The ratio of mineral powder to aggregate is determined based on the obtained mineral void ratio; Multiple sets of asphalt dosages were set, and multiple sets of second Marshall specimens were prepared in combination with the determined ratio of mineral powder to aggregate. Density and Marshall tests were conducted using the second Marshall specimen. Based on the obtained void ratio, aggregate void ratio, coarse aggregate skeleton void ratio, asphalt saturation, and stability, the optimal asphalt content was determined.

8. A road surface structure, characterized in that, It includes, from top to bottom, an asphalt concrete surface layer, an asphalt concrete bottom layer, a stress-absorbing layer, and a water-stabilized base layer, wherein the proportions of aggregates, mineral powder, and asphalt used in the asphalt concrete surface layer are obtained using the asphalt mixture design method described in claim 7.

9. A road surface structure as described in claim 8, characterized in that, In the asphalt concrete lower layer, the mass ratio of coarse aggregate, medium aggregate, fine aggregate, and mineral powder is 34-38:25-29:33-37:1-3, with the remainder being asphalt. The mass of asphalt accounts for 4%-5% of the total mass of the asphalt concrete lower layer. Furthermore, in the asphalt concrete lower layer, the coarse aggregate has a particle size range of 10-20mm, excluding the 10mm endpoint; the medium aggregate has a particle size range of 5-10mm, excluding the 5mm endpoint; and the fine aggregate has a particle size range of 0-5mm, excluding the 0mm endpoint.

10. A road surface structure as described in claim 9, characterized in that, In the asphalt concrete lower layer, the mass ratio of coarse aggregate, medium aggregate, fine aggregate and mineral powder is 36:27:35:2, and the remainder is asphalt. The mass of asphalt accounts for 4.3% of the total mass of the asphalt concrete lower layer.

11. A road surface structure as described in claim 8, characterized in that, In the stress-absorbing layer, the mass ratio of coarse aggregate, fine aggregate, and mineral powder is 13-15:80-82:4-6, and the remainder is asphalt, with the asphalt mass accounting for 8%-10% of the total mass of the stress-absorbing layer. Furthermore, in the stress-absorbing layer, the coarse aggregate has a particle size range of 3-5 mm, excluding the 3 mm endpoint, and the fine aggregate has a particle size range of 0-3 mm, excluding the 0 mm endpoint.

12. A road surface structure as described in claim 11, characterized in that, In the stress-absorbing layer, the mass ratio of coarse aggregate, fine aggregate and mineral powder is 14:81:5, and the remainder is asphalt, with the asphalt mass accounting for 9.0% of the total mass of the stress-absorbing layer.

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