A design method for AC airport asphalt mixture based on high-temperature rut resistance

Abstract

The application discloses a kind of AC type airport asphalt mixture mix design methods based on high-temperature rut resistance, it relates to a kind of AC type airport asphalt mixture mix design methods.The purpose of the present application is to solve the problem that current design method cannot avoid rutting damage of pavement by the mix design of asphalt mixture.Method: step one, raw material selection;Step two, mineral aggregate gradation design;Step three, optimum gradation determination;Step four, test asphalt content selection;Step five: optimum asphalt content calculation;Step six, optimum asphalt content test;Step seven, performance verification.The high-temperature compressive strength used in the application can reflect the high-temperature performance of asphalt mixture, and the rutting resistance of pavement structure is targetedly improved in the mix design stage, and the designed asphalt mixture does not need high-temperature performance test in later period, thereby improving engineering efficiency.The application can obtain a kind of AC type airport asphalt mixture mix design methods based on high-temperature rut resistance.

Description

TECHNICAL FIELD

[0001] The application relates to an AC type airport asphalt mixture mix design method. BACKGROUND

[0002] An airport pavement is one of the most important infrastructures in an airport system, and the paving material is mainly an asphalt mixture. The asphalt pavement has a smooth surface, sufficient bearing capacity, and can realize non-stop construction during the construction period and rapid disease treatment during the operation period. The take-off, landing and taxiing of an airplane are all completed on a runway, so good pavement service performance is a safety guarantee for a series of operations of the airplane. However, as an external structure, the airport pavement is long-term affected by external environment and airplane loads, and the airplane loads have characteristics different from vehicle loads, such as multi-wheel group, high tire pressure, multiple running states and high-temperature wake flow. The typical characteristics of the airplane loads cause the airport asphalt pavement to be prone to rutting diseases. The rutting diseases seriously affect the flatness of the runway surface and are very unfavorable for the safe operation of the airport. For a multi-asphalt layer pavement structure, rutting deformation mainly occurs in the middle surface layer and the lower surface layer. At present, the two layer positions generally adopt asphalt concrete (AC), so the high-temperature performance of the AC type mixture in the middle and lower surface layers is crucial to the overall rutting resistance of the pavement structure.

[0003] The mix design of the asphalt mixture is an important factor affecting the service performance of the asphalt pavement structure. At present, the Marshall method is adopted for the design of the AC type asphalt mixture. The method takes the void ratio VTM and the asphalt saturation VFA as the main volume indexes, and the selection of the gradation and the determination of the asphalt content are excessively dependent on the volume characteristics of the asphalt mixture. In addition, the two mechanical indexes, namely the Marshall stability and the flow value, contained in the Marshall design method are empirical in nature and have weak correlation with the structural rutting resistance in the field, so the two indexes have limitations in representing the high-temperature performance of the asphalt mixture. Therefore, it is difficult to design the airport asphalt mixture with good rutting resistance by the Marshall design method, so as to realize effective control of the pavement rutting. SUMMARY

[0004] The application aims to solve the problem that the current design method cannot avoid the pavement rutting damage through the mix design of the asphalt mixture, and provides an AC type airport asphalt mixture mix design method based on high-temperature rutting resistance.

[0005] An AC type airport asphalt mixture mix design method based on high-temperature rutting resistance, characterized in that the method comprises the following steps:

[0006] Step one, raw material selection:

[0007] The raw materials are coarse aggregate, fine aggregate, mineral powder, asphalt and additive, wherein the coarse aggregate is graded according to particle size;

[0008] Step two, mineral aggregate grading design:

[0009] The coarse aggregate, fine aggregate and mineral powder selected in step one are used as the mineral aggregate, the proportion of the coarse aggregate, fine aggregate and mineral powder in the mineral aggregate is adjusted, three synthetic mineral aggregate gradings with different coarse and fine aggregates are designed, and the passing rate of the coarse aggregate grading boundary screen hole should be in the interval of the median value+5% to the median value-10% of the mineral aggregate grading range;

[0010] Step three, determination of the best grading:

[0011] The standard asphalt content of the AC type asphalt mixture of the similar projects built in the location of the airport is combined, the initial asphalt content is selected in the range of 3.5% to 5.0%, and the three synthetic mineral aggregate gradings designed in step two are used to form Marshall test pieces, then the uniaxial compression test is carried out, according to the results of the uniaxial compression test, the mineral aggregate grading used by the Marshall test piece with the maximum high-temperature compression strength is taken as the best grading;

[0012] Step four, selection of the test asphalt content:

[0013] (1) The initial asphalt content selected in step three is taken as the median value, and 2-3 asphalt contents are taken above and below the median value with an interval of 0.5%, so as to obtain 5-7 test asphalt contents;

[0014] (2) The best grading determined in step three is used to form 5-7 groups of Marshall test pieces, the volume index and high-temperature compression strength of the 5-7 groups of Marshall test pieces are tested; the volume index includes: bulk density ρ, void ratio VTM, asphalt saturation VFA and mineral aggregate interstitial void ratio VMA; the void ratios of the 5-7 groups of Marshall test pieces are compared, the smallest void ratio is recorded as VTM min , the largest void ratio is recorded as VTM max , and the data range value between VTM min and VTM max ; under the condition that VTM min ~ VTM max contains 3% to 5% and the peak value of the high-temperature compression strength appears, if the condition is met, the best asphalt content is calculated according to step five, if the condition is not met, the test asphalt content is reselected in step four (1), and then the operation is performed in turn according to the steps;

[0015] Step five: calculation of the best asphalt content:

[0016] (1), with high temperature compressive strength, bulk density p, void ratio VTM and asphalt saturation VFA as test indexes, according to the change of each test index with asphalt content, the asphalt content OAC1 is calculated by the following method:

[0017] ①, if the range value of asphalt saturation VFA in the curve of asphalt saturation VFA with asphalt content contains the required range of asphalt saturation of asphalt mixture, and the bulk density p in the curve of bulk density with asphalt content appears a peak value; find the asphalt content a1 corresponding to the peak value of high temperature compressive strength in the curve of high temperature compressive strength with asphalt content, select a certain value in the range of 3% ~ 5% as the target void ratio, find the asphalt content a2 corresponding to the target void ratio in the curve of void ratio VTM with asphalt content, find the asphalt content a3 corresponding to the peak value of bulk density in the curve of bulk density p with asphalt content, find the asphalt content a4 corresponding to the median value of asphalt saturation in the curve of asphalt saturation VFA with asphalt content, calculate the asphalt content OAC1 by the following formula:

[0018] OAC1 = (a1 x 0.4) + (a2 x 0.2) + (a3 x 0.2) + (a4 x 0.2);

[0019] ②, if the range value of asphalt saturation VFA in the curve of asphalt saturation VFA with asphalt content contains the required range of asphalt saturation of asphalt mixture, and the bulk density p in the curve of bulk density with asphalt content does not appear a peak value, then the asphalt content OAC1 is calculated by the following formula:

[0020] OAC1 = (a1 x 0.4) + (a2 x 0.3) + (a4 x 0.3);

[0021] ③, if the range value of asphalt saturation VFA in the curve of asphalt saturation VFA with asphalt content does not contain the required range of asphalt saturation of asphalt mixture, and the bulk density p in the curve of bulk density with asphalt content appears a peak value, then the asphalt content OAC1 is calculated by the following formula:

[0022] OAC1 = (a1 x 0.4) + (a2 x 0.3) + (a3 x 0.3);

[0023] ④, if the range value of asphalt saturation VFA in the curve of asphalt saturation VFA with asphalt content does not contain the required range of asphalt saturation of asphalt mixture, and the bulk density p in the curve of bulk density with asphalt content does not appear a peak value, then the asphalt content OAC1 is calculated by the following formula:

[0024] OAC1 = (a1 x 0.5) + (a2 x 0.5);

[0025] The asphalt saturation VFA of the asphalt mixture in steps five (1) (1) to (4) is required to be in the range of 55% to 70% if the asphalt mixture is AC-25, and in the range of 65% to 75% if the asphalt mixture is AC-16 or AC-20.

[0026] (2) The technical requirements are that the void ratio VTM is 3% to 5%, the asphalt saturation VFA is in the required range, and the high-temperature compressive strength meets the engineering indexes under the corresponding high-temperature climate zone and aviation traffic volume of the location of the airport; when the void ratio VTM is 3% to 5%, the corresponding asphalt content is OAC VTMmin to OAC VTMmax When the asphalt saturation VFA is in the required range, the corresponding asphalt content is OAC VFAmin to OAC VFAmax When the high-temperature compressive strength meets the engineering indexes under the corresponding high-temperature climate zone and aviation traffic volume of the location of the airport, the corresponding asphalt content is OAC Gmin to OAC Gmax The intersection of the above three asphalt contents is calculated, the lower limit of the intersection is OAC min , and the upper limit of the intersection is OAC max The asphalt content OAC2 is calculated by the following formula:

[0027] OAC2 = (OAC min + OAC max ) / 2;

[0028] The asphalt saturation VFA is required to be in the range of 55% to 70% if the asphalt mixture is AC-25, and in the range of 65% to 75% if the asphalt mixture is AC-16 or AC-20.

[0029] The requirement that the high-temperature compressive strength meets the engineering indexes under the corresponding high-temperature climate zone and aviation traffic volume of the location of the airport is specifically shown in Table 1.

[0030] Table 1

[0031]

[0032]

[0033] (3) The lower limit of the intersection of the three asphalt contents in step five (2) is OAC min , and the upper limit of the intersection of the three asphalt contents is OAC max The optimal asphalt content OAC is determined by the following method:

[0034] ①, if OAC1 is within OAC min ~ OAC max , then OAC1 is taken as the optimum asphalt content OAC;

[0035] ②, if OAC1 is outside OAC min ~ OAC max , but the average of OAC1 and OAC2 is within OAC min ~ OAC max , then the average of OAC1 and OAC2 is taken as the optimum asphalt content OAC;

[0036] ③, if both OAC1 and the average of OAC1 and OAC2 are outside OAC min ~ OAC max , then return to step one to reselect raw materials or step two to redesign the aggregate gradation, and then follow the steps in turn;

[0037] Step six: optimum asphalt content test:

[0038] According to the optimum asphalt content OAC calculated in step five and the optimum gradation determined in step three, the Marshall test piece is formed to test whether the volume index and high temperature compressive strength meet the technical requirements, wherein the void ratio VTM of the Marshall test piece is taken as the design void ratio, and the volume index and high temperature compressive strength requirements are shown in Table 2 and Table 3:

[0039] Table 2

[0040]

[0041] In Table 2, if the design void ratio is an integer, the corresponding aggregate void ratio VMA requirement value is selected according to the nominal maximum particle size and the type of asphalt mixture in the table; if the design void ratio is not an integer, for AC-25 type asphalt mixture with a nominal maximum particle size of 26.5mm, the aggregate void ratio VMA requirement value is the design void ratio + 8%; for AC-20 type asphalt mixture with a nominal maximum particle size of 19mm, the aggregate void ratio VMA requirement value is the design void ratio + 9%; for AC-16 type asphalt mixture with a nominal maximum particle size of 16mm, the aggregate void ratio VMA requirement value is the design void ratio + 9.5%;

[0042] Table 3

[0043]

[0044] If the volume index and high-temperature compressive strength of the formed Marshall test piece do not meet the technical requirements in Tables 2 and 3, the process returns to step one to reselect raw materials or step two to redesign the mineral aggregate gradation, and then the process is performed again in sequence; if the volume index and high-temperature compressive strength of the formed Marshall test piece meet the technical requirements in Tables 2 and 3, step seven is performed;

[0045] Step seven: performance verification

[0046] A test piece is formed according to the optimal asphalt content OAC calculated in step five and the optimal gradation determined in step three; the test piece meets the technical requirements in Tables 2 and 3; the test piece is subjected to low-temperature cracking resistance and water stability verification; the low-temperature cracking resistance is verified by a low-temperature bending test, and the index is the maximum bending tensile strain; the water stability is verified by a freeze-thaw splitting test, and the index is the residual strength ratio; if the verification results meet the technical requirements, the mix proportion design is completed, otherwise the process returns to step one to reselect raw materials or step two to redesign the mineral aggregate gradation, and then the process is performed again in sequence; the technical requirements are: the residual strength ratio is greater than or equal to 85%, and the maximum bending tensile strain is shown in Table 4:

[0047] Table 4

[0048]

[0049] Compared with the prior art, the present application has the following advantages:

[0050] (1) The present application uses high-temperature compressive strength instead of Marshall stability; compared with Marshall stability, high-temperature compressive strength is more sensitive to changes in the amount of asphalt, and can more accurately reflect the high-temperature rutting resistance of asphalt mixture; and in the key stages of asphalt mixture design, such as optimal gradation determination and optimal asphalt content calculation, the high-temperature performance of asphalt mixture is fully considered, rather than only using the volume index as a guide, so that the asphalt mixture designed has better rutting resistance;

[0051] (2) In the current airport asphalt mixture design method, the high-temperature performance of the finally designed asphalt mixture needs to be verified by a rutting test; the rutting test requires a plate-shaped test piece, which has a large volume and a complex molding method, and needs to be placed for 48 hours before testing; therefore, the whole process has a long cycle; the uniaxial compression test used in the present application can be performed using a Marshall test piece, and in the verification stage of the design process, the high-temperature performance of the asphalt mixture does not need to be tested again; this not only shortens the cycle of mix proportion design, but also reduces the workload of indoor tests, thereby significantly improving engineering efficiency;

[0052] The present application can obtain an AC-type airport asphalt mixture mix proportion design method based on high-temperature rutting resistance.

[0053] The mineral aggregate in the present application comprises 2 to 5 grades of coarse aggregate, fine aggregate and mineral powder; the asphalt content refers to the mass percentage of asphalt in the asphalt mixture, wherein the asphalt mixture comprises asphalt and mineral aggregate; the mineral aggregate comprises coarse aggregate, fine aggregate and mineral powder. The test sample comprises asphalt, mineral aggregate and additives. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 A flow chart of an AC airport asphalt mixture mix design method based on high-temperature rut resistance according to the present application;

[0055] Figure 2 A curve of high-temperature compressive strength versus asphalt content in Example 1;

[0056] Figure 3 A curve of void ratio VTM versus asphalt content in Example 1;

[0057] Figure 4 A curve of bulk density p versus asphalt content in Example 1;

[0058] Figure 5 A curve of asphalt saturation VFA versus asphalt content in Example 1;

[0059] Figure 6 A curve of mineral aggregate void ratio VMA versus asphalt content in Example 1. DETAILED DESCRIPTION

[0060] The following examples further illustrate the present application but should not be construed as limiting the present application. Modifications and substitutions to the methods, steps or conditions described herein can be made by one skilled in the art without departing from the spirit of the present application.

[0061] Specific embodiment one: the present embodiment is an AC airport asphalt mixture mix design method based on high-temperature rut resistance, comprising the following steps:

[0062] Step one, raw material selection:

[0063] Coarse aggregate, fine aggregate, mineral powder, asphalt and additives are used as raw materials, wherein the coarse aggregate is graded according to particle size;

[0064] Step two, mineral aggregate grading design:

[0065] The coarse aggregate, fine aggregate and mineral powder selected in step one are used as mineral aggregate, the proportions of coarse aggregate, fine aggregate and mineral powder in the mineral aggregate are adjusted, three different synthetic mineral aggregate gradings are designed, and the passing rate of the coarse aggregate grading boundary screen hole should be in the interval of median value+5% to median value-10% of the mineral aggregate grading range;

[0066] Step three, optimum gradation determination:

[0067] In combination with the standard asphalt dosage of AC type asphalt mixture of similar projects built in the airport location, select the initial asphalt dosage in the range of 3.5% to 5.0%, and use the three synthetic aggregate gradations designed in step two to respectively form Marshall test pieces, and then perform uniaxial compression test. According to the results of the uniaxial compression test, the aggregate gradation used by the Marshall test piece with the maximum high-temperature compression strength is taken as the optimum gradation;

[0068] Step four, test asphalt dosage selection:

[0069] (1) Take the initial asphalt dosage selected in step three as the median value, and take 2-3 asphalt dosages with an interval of 0.5% above and below the median value, thereby obtaining 5-7 test asphalt dosages;

[0070] (2) Use the optimum gradation determined in step three to respectively form 5-7 groups of Marshall test pieces, and test the volume index and high-temperature compression strength of the 5-7 groups of Marshall test pieces. The volume index includes: bulk density ρ, void ratio VTM, asphalt saturation VFA, and aggregate interstitial porosity VMA. Compare the void ratios of the 5-7 groups of Marshall test pieces, wherein the smallest void ratio is denoted as VTM min , and the largest void ratio is denoted as VTM max . The data range value is between VTM min and VTM max . VTM min ~ VTM max contains 3% to 5%, and the peak value of high-temperature compression strength appears. If the condition is met, calculate the optimum asphalt dosage according to step five. If the condition is not met, return to step four (1) to reselect the test asphalt dosage, and then perform the operation in turn according to the steps;

[0071] Step five: calculation of optimum asphalt dosage:

[0072] (1) Take high-temperature compression strength, bulk density ρ, void ratio VTM, and asphalt saturation VFA as test indexes, and calculate the asphalt dosage OAC1 according to the change of each test index with asphalt dosage by the following method:

[0073] ①, if the range value of the asphalt saturation VFA in the curve of the asphalt saturation VFA changing with the asphalt content contains the required range of the asphalt saturation of the asphalt mixture, and the bulk volume density ρ appears a peak value in the curve of the bulk volume density changing with the asphalt content; finding the asphalt content a1 corresponding to the peak value of the high-temperature compressive strength in the curve of the high-temperature compressive strength changing with the asphalt content, selecting a certain value in the range of 3% to 5% as the target air void, finding the asphalt content a2 corresponding to the target air void in the curve of the air void VTM changing with the asphalt content, finding the asphalt content a3 corresponding to the peak value of the bulk volume density in the curve of the bulk volume density ρ changing with the asphalt content, finding the asphalt content a4 corresponding to the median value of the asphalt saturation in the curve of the asphalt saturation VFA changing with the asphalt content, and calculating the asphalt content OAC1 by the following formula:

[0074] OAC1 = (a1 x 0.4) + (a2 x 0.2) + (a3 x 0.2) + (a4 x 0.2);

[0075] ②, if the range value of the asphalt saturation VFA in the curve of the asphalt saturation VFA changing with the asphalt content contains the required range of the asphalt saturation of the asphalt mixture, and the bulk volume density ρ does not appear a peak value in the curve of the bulk volume density changing with the asphalt content, then the asphalt content OAC1 is calculated by the following formula:

[0076] OAC1 = (a1 x 0.4) + (a2 x 0.3) + (a4 x 0.3);

[0077] ③, if the range value of the asphalt saturation VFA in the curve of the asphalt saturation VFA changing with the asphalt content does not contain the required range of the asphalt saturation of the asphalt mixture, and the bulk volume density ρ appears a peak value in the curve of the bulk volume density changing with the asphalt content, then the asphalt content OAC1 is calculated by the following formula:

[0078] OAC1 = (a1 x 0.4) + (a2 x 0.3) + (a3 x 0.3);

[0079] ④, if the range value of the asphalt saturation VFA in the curve of the asphalt saturation VFA changing with the asphalt content does not contain the required range of the asphalt saturation of the asphalt mixture, and the bulk volume density ρ does not appear a peak value in the curve of the bulk volume density changing with the asphalt content, then the asphalt content OAC1 is calculated by the following formula:

[0080] OAC1 = (a1 x 0.5) + (a2 x 0.5);

[0081] The asphalt saturation VFA of the asphalt mixture in steps five (1) ①-④ is required to be in the range of 55%-70% if the asphalt mixture is AC-25, or in the range of 65%-75% if the asphalt mixture is AC-16 or AC-20;

[0082] (2) The technical requirements are that the void ratio VTM is 3%-5%, the asphalt saturation VFA is in the required range, and the high-temperature compression strength meets the engineering indexes in the corresponding high-temperature climate zone and under the aviation traffic volume of the location of the airport; when the void ratio VTM is 3%-5%, the corresponding asphalt content is OAC VTMmin -OAC VTMmax When the asphalt saturation VFA is in the required range, the corresponding asphalt content is OAC VFAmin -OAC VFAmax When the high-temperature compression strength meets the engineering indexes in the corresponding high-temperature climate zone and under the aviation traffic volume of the location of the airport, the corresponding asphalt content is OAC Gmin -OAC Gmax The intersection of the above three asphalt contents is calculated, the lower limit of the intersection is OAC min , and the upper limit of the intersection is OAC max The asphalt content OAC2 is calculated by the following formula:

[0083] OAC2=(OAC min +OAC max ) / 2;

[0084] The asphalt saturation VFA is required to be in the range of 55%-70% if the asphalt mixture is AC-25, or in the range of 65%-75% if the asphalt mixture is AC-16 or AC-20;

[0085] The high-temperature compression strength meeting the engineering indexes in the corresponding high-temperature climate zone and under the aviation traffic volume of the location of the airport is specifically shown in Table 1;

[0086] Table 1

[0087]

[0088]

[0089] (3) The lower limit of the intersection of the three asphalt contents in step five (2) is OAC min , and the upper limit of the intersection of the three asphalt contents is OAC max The optimal asphalt content OAC is determined by the following method:

[0090] ① If OAC1 is in OACmin ~ OAC max If OAC1 is within OAC

[0091] If OAC1 is within OAC min ~ OAC max If OAC1 is outside OAC min ~ OAC max If OAC1 is within OAC

[0092] If OAC1 is outside OAC min ~ OAC max If OAC1 is outside OAC

[0093] Step six: verification of the optimum asphalt content:

[0094] According to the optimum asphalt content OAC calculated in step five and the optimum gradation determined in step three, Marshall specimens are formed to verify whether the volume index and high temperature compressive strength meet the technical requirements, wherein the void ratio VTM of the Marshall specimen is taken as the design void ratio, and the volume index and high temperature compressive strength requirements are shown in Table 2 and Table 3:

[0095] Table 2

[0096]

[0097] In Table 2, if the design void ratio is an integer, the corresponding mineral material gap ratio VMA requirement value is selected according to the nominal maximum particle size and the type of asphalt mixture in the table; if the design void ratio is not an integer, for AC-25 type asphalt mixture with a nominal maximum particle size of 26.5mm, the mineral material gap ratio VMA requirement value is the design void ratio + 8%; for AC-20 type asphalt mixture with a nominal maximum particle size of 19mm, the mineral material gap ratio VMA requirement value is the design void ratio + 9%; for AC-16 type asphalt mixture with a nominal maximum particle size of 16mm, the mineral material gap ratio VMA requirement value is the design void ratio + 9.5%;

[0098] Table 3

[0099]

[0100] If the volume index and high-temperature compressive strength of the formed Marshall test piece do not meet the technical requirements in Tables 2 and 3, return to step one to reselect raw materials or step two to redesign the mineral aggregate gradation, and then sequentially perform the steps; if the volume index and high-temperature compressive strength of the formed Marshall test piece meet the technical requirements in Tables 2 and 3, perform step seven;

[0101] Step seven: performance verification

[0102] Form the test piece according to the optimal asphalt content OAC calculated in step five and the optimal gradation determined in step three; the test piece meets the technical requirements in Tables 2 and 3; verify the low-temperature cracking resistance and water stability of the test piece; the low-temperature cracking resistance is verified by a low-temperature bending test, and the index is the maximum bending tensile strain; the water stability is verified by a freeze-thaw splitting test, and the index is the residual strength ratio; if the verification results meet the technical requirements, complete the mix proportion design, otherwise return to step one to reselect raw materials or step two to redesign the mineral aggregate gradation, and then sequentially perform the steps; the technical requirements are: residual strength ratio ≥ 85%, and the maximum bending tensile strain is shown in Table 4:

[0103] Table 4

[0104]

[0105] Specific implementation method two: the difference between this implementation method and specific implementation method one is that the additive is one or a mixture of several of anti-rutting agents, high-modulus agents, and high-viscosity agents. The other steps are the same as specific implementation method one.

[0106] Specific implementation method three: the difference between this implementation method and one of specific implementation methods one or two is that the additive accounts for 0.5% to 1.0% of the total mass of the coarse aggregate, fine aggregate, mineral powder, and asphalt. The other steps are the same as specific implementation methods one or two.

[0107] Specific implementation method four: the difference between this implementation method and one of specific implementation methods one to three is that the test temperature of the uniaxial compression test in step three is 60°C, and the loading rate is 2 mm / min. The other steps are the same as specific implementation methods one to three.

[0108] Specific implementation five: the difference between this embodiment and one of the first four specific implementations is that the hot summer area in Table 1 is that the average value of the daily maximum temperature in the hottest month is greater than 30℃, the hot summer area is that the average value of the daily maximum temperature in the hottest month is between 20℃ and 30℃, the cool summer area is that the average value of the daily maximum temperature in the hottest month is less than 20℃, the heavy traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are greater than 50,000 times, the medium traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are between 15,000 times and 50,000 times, and the light traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are less than 15,000 times. The other steps are the same as those of the first four specific implementations.

[0109] Specific implementation six: the difference between this embodiment and one of the first five specific implementations is that the hot summer area in Table 3 is that the average value of the daily maximum temperature in the hottest month is greater than 30℃, the hot summer area is that the average value of the daily maximum temperature in the hottest month is between 20℃ and 30℃, the cool summer area is that the average value of the daily maximum temperature in the hottest month is less than 20℃, the heavy traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are greater than 50,000 times, the medium traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are between 15,000 times and 50,000 times, and the light traffic is that the annual average take-off times of C and above aircraft models in a single runway design period are less than 15,000 times. The other steps are the same as those of the first five specific implementations.

[0110] Specific implementation seven: the difference between this embodiment and one of the first six specific implementations is that the winter severe cold area in Table 4 is that the winter extreme daily minimum temperature with 99% reliability is less than -37℃, the winter cold area is that the winter extreme daily minimum temperature with 99% reliability is between -37℃ and -21.5℃, the winter cold area is that the winter extreme daily minimum temperature with 99% reliability is between -21.5℃ and -9℃, and the winter warm area is that the winter extreme daily minimum temperature with 99% reliability is greater than -9℃. The other steps are the same as those of the first six specific implementations.

[0111] Example 1: combined Figures 1 to 6 This embodiment is a kind of AC type airport asphalt mixture mix proportion design method based on anti high temperature rut, including the following steps:

[0112] Step one, raw material selection:

[0113] Coarse aggregate, fine aggregate, mineral powder, asphalt and additive are used as raw materials, wherein coarse aggregate is graded according to particle size;

[0114] The coarse aggregate is limestone coarse aggregate;

[0115] The fine aggregate is limestone fine aggregate;

[0116] The mineral powder mentioned is limestone mineral powder;

[0117] The asphalt mentioned is a composite modified asphalt of SBS and lake asphalt;

[0118] The additives mentioned are anti-rutting agents and high-viscosity agents;

[0119] The technical specifications and corresponding technical requirements of the raw materials are shown in Tables 5-10;

[0120] Step 2: Mineral aggregate gradation design:

[0121] Using the coarse aggregate, fine aggregate and mineral powder selected in step one as the mineral materials, the proportions of coarse aggregate, fine aggregate and mineral powder in the mineral materials are adjusted to design three AC-20 gradations with different coarseness and fineness. The proportions of each type of mineral material and the corresponding synthetic mineral material gradations are shown in Table 11 and Table 12.

[0122] Step 3: Determining the optimal gradation:

[0123] Based on the standard asphalt content of AC-type asphalt mixtures in similar existing projects at the airport location, 4.5% was selected as the initial asphalt content within the range of 3.5% to 5.0%. Marshall specimens were formed using the three synthetic aggregate gradations designed in step two, and then uniaxial compression tests were conducted at a temperature of 60℃ and a loading rate of 2mm / min. According to the results of the uniaxial compression tests, as shown in Table 13, based on the gradation selection method, the mixture corresponding to gradation three has the highest high-temperature compressive strength. Therefore, gradation three was selected as the optimal gradation.

[0124] Step 4: Selection of Asphalt Dosage for the Test:

[0125] (1) Taking the initial asphalt dosage of 4.5% selected in step three as the median, and taking two asphalt dosages above and below the median at intervals of 0.5%, we obtained 3.5%, 4.0%, 4.5%, 5.0%, and 5.5% as the test asphalt dosages.

[0126] (2) Using the optimal gradation determined in step three, five groups of Marshall specimens were molded. The volumetric properties and high-temperature compressive strength of the five groups of Marshall specimens were tested, and the results are as follows: Figures 2 to 6 As shown; the volumetric indices include: bulk density ρ, void fraction VTM, bituminous saturation VFA, and aggregate void ratio VMA; the void fractions of the five groups of Marshall specimens were compared, and the smallest void fraction was denoted as VTM. min The maximum porosity is denoted as VTM. max VTM min To VTM max The values ​​between these ranges represent a data range; using VTM min ~VTMmax The asphalt content is 3% to 5%, and the peak value of high-temperature compressive strength appears; as shown in the figure, under the asphalt content of the five tests, the void ratio VTM covers 3% to 5%, and the peak value of high-temperature compressive strength appears;

[0127] Step five: calculate the optimal asphalt content:

[0128] According to the change of each test index with the asphalt content, the asphalt content OAC1 is calculated by the following method:

[0129] As shown in the figure, the asphalt content a1 corresponding to the peak value of high-temperature compressive strength is 4.0%, the asphalt content a2 corresponding to the target void ratio is 4.5%, the asphalt content a3 corresponding to the peak value of bulk density is 5.0%, and the asphalt content a4 corresponding to the median value of asphalt saturation degree range is 4.4%. The asphalt content OAC1 is calculated by the following formula:

[0130] OAC1=(a1×0.4)+(a2×0.2)+(a3×0.2)+(a4×0.2);

[0131] After calculation, the asphalt content OAC1 is 4.4%;

[0132] (2) The technical requirements are that the void ratio VTM meets 3% to 5%, the asphalt saturation degree VFA meets the required range, and the high-temperature compressive strength meets the engineering index under the corresponding high-temperature climate division and aviation traffic volume of the airport location; when the void ratio VTM meets 3% to 5%, the corresponding asphalt content is OAC VTMmin ~OAC VTMmax When the asphalt saturation degree VFA of the asphalt mixture meets the required range, the corresponding asphalt content is OAC VFAmin ~OAC VFAmax When the high-temperature compressive strength meets the engineering index under the corresponding high-temperature climate division and aviation traffic volume of the airport location, the corresponding asphalt content is OAC Gmin ~OAC Gmax The intersection of the above three asphalt contents is calculated, the lower limit of the intersection is OAC min , and the upper limit of the intersection is OAC max After calculation, OAC min is 4.2%, and OAC max is 4.7%. The asphalt content OAC2 is calculated by the following formula:

[0133] OAC2=(OAC min +OAC max ) / 2;

[0134] After calculation, OAC2 is 4.45%, and because OAC1 is in OAC min ~OACmax Therefore, 4.4% is taken as the optimal asphalt content OAC;

[0135] Step six: verification of the optimal asphalt content:

[0136] According to the optimal asphalt content OAC (4.4%) calculated in step five and the optimal gradation (gradation three) determined in step three, Marshall test pieces are formed, and the volume index and high-temperature compressive strength are tested, and the results are shown in Table 14; the design air voids of the asphalt mixture is 4.1%, the nominal maximum particle size is 19 mm, the type of the asphalt mixture is AC-20, the high-temperature climate division of the engineering location is considered as the summer hot region, and the aviation traffic level is heavy traffic;

[0137] Verify whether each index meets the technical requirements, and the volume index and high-temperature compressive strength requirements are shown in Table 2 and Table 3:

[0138] Table 2

[0139]

[0140] Table 3

[0141]

[0142]

[0143] The summer hot region described in Table 3 is that the average value of the daily maximum temperature in the hottest month is greater than 30°C, the summer hot region is that the average value of the daily maximum temperature in the hottest month is between 20°C and 30°C, the summer cool hot region is that the average value of the daily maximum temperature in the hottest month is less than 20°C, the heavy traffic is that the annual average take-off cycles of C and above types of aircraft in a single runway design period is greater than 50,000 times, the medium traffic is that the annual average take-off cycles of C and above types of aircraft in a single runway design period is between 15,000 times and 50,000 times, and the light traffic is that the annual average take-off cycles of C and above types of aircraft in a single runway design period is less than 15,000 times;

[0144] By comparison with the technical requirements, each index meets the requirements;

[0145] Step seven: performance verification:

[0146] According to the optimal asphalt content OAC (4.4%) calculated in step five and the optimal gradation (gradation three) determined in step three, a test piece is formed, the test piece meets the technical requirements in Tables 2 and 3; the test piece is subjected to low-temperature crack resistance and water stability verification; the low-temperature crack resistance is verified by a low-temperature bending test, and the index is the maximum bending tensile strain; the water stability is verified by a freeze-thaw splitting test, and the index is the residual strength ratio; the results are shown in Table 15; if the verification results meet the technical requirements, the mix proportion design is completed; the low-temperature climate division of the project location is considered as the winter cold region; it can be known from Table 15 that the performance verification of the AC-20 asphalt mixture of the embodiment meets the technical requirements, which indicates that the low-temperature crack resistance and water stability are good, and therefore, the mix proportion design is completed.

[0147] The technical requirements are: the residual strength ratio is greater than or equal to 85%, and the maximum bending tensile strain is shown in Table 4:

[0148] Table 4

[0149]

[0150] The winter severe cold region in Table 4 is a winter extreme daily minimum temperature of 99% reliability less than -37℃, the winter cold region is a winter extreme daily minimum temperature of 99% reliability between -37℃ and -21.5℃, the winter cold region is a winter extreme daily minimum temperature of 99% reliability between -21.5℃ and -9℃, and the winter warm region is a winter extreme daily minimum temperature of 99% reliability greater than -9℃.

[0151] Table 5 Technical indexes and required values of coarse aggregate

[0152]

[0153]

[0154] Table 6 Technical indexes and required values of fine aggregate

[0155] Technical index Test index Required value Apparent relative density 2.773 ≥2.5 Firmness (portion greater than 0.3 mm) (%) 8.2 ≤12 Sand equivalent (%) 68 ≥60 Methylene blue value (g / kg) 0.6 ≤2.5 Angularity (flow time) (s) 43 ≥30

[0156] Table 7 Technical indexes and required values of mineral powder

[0157]

[0158]

[0159] Table 8 Technical indexes and required values of SBS and lake asphalt compound modified asphalt

[0160] Technical index Test index Required value Penetration at 25°C (0.1 mm) 39 30～50 Softening point (°C) 88.5 ≥80 Ductility (5 cm / min, 5°C) (cm) 18.5 ≥15 Elastic recovery (%) 98 ≥80

[0161] Table 9 Technical indexes and required values of anti-rutting agent

[0162]

[0163] Table 10 Technical index and requirement value of high viscosity agent

[0164] Test index Test result Technical requirement Unit particle mass (g) 0.027 ≤0.03 Density (g / cm 3 )]]> 0.9 ≤1 Melt index (g / 10 min) 2.71 ≥2 Ash content (%) 0.3 ≤1

[0165] Table 11 Mineral aggregate gradation and mix proportion

[0166]

[0167] Table 12 Synthetic gradation and specification limit value

[0168]

[0169] Table 13 High temperature compression strength and requirement value of candidate mix

[0170] Technical index Grading 1 Grading 2 Grading 3 Required value High-temperature compressive strength (MPa) 3.04 3.03 3.08 ＞3.0

[0171] Table 14 Test result and requirement value of each index under optimal asphalt content

[0172] Technical index Test result Required value Void ratio VTM (%) 4.1 3～5 Mineral aggregate interstitial ratio VMA (%) 13.8 ≥13.1 Asphalt saturation VFA (%) 70.1 65～75 High-temperature compressive strength (MPa) 3.12 ＞3.0

[0173] Table 15 Test result and requirement value of performance verification

[0174] Technical index Test result Required value Maximum bending tensile strain (με) 3210 ≥2500 Residual strength ratio (%) 89.3 ≥85

[0175] In Example 1, the mineral aggregate includes four grades of coarse aggregate, fine aggregate and mineral powder; the asphalt content refers to the mass percentage of asphalt in the asphalt mixture, wherein the asphalt mixture includes asphalt and mineral aggregate; the mineral aggregate includes aggregate, fine aggregate and mineral powder. The test piece includes asphalt, mineral aggregate and additive, and the mass fraction of the anti-rutting agent in the asphalt mixture is 0.5% and the mass fraction of the high viscosity agent in the asphalt mixture is 0.3% in Example 1.

Claims

1. A mix design method for AC-type airport asphalt mixtures based on high-temperature rutting resistance, characterized in that... The method includes the following steps: Step 1: Raw material selection: The raw materials are coarse aggregate, fine aggregate, mineral powder, asphalt and additives, with the coarse aggregate being graded according to particle size; Step 2: Mineral aggregate gradation design: Using the coarse aggregate, fine aggregate, and mineral powder selected in step one as the mineral materials, adjust the proportion of coarse aggregate, fine aggregate, and mineral powder in the mineral materials, design three synthetic mineral gradations with different coarseness, and the passing rate of the coarse aggregate dividing screen should be within the range of the median value +5% to the median value -10% of the mineral gradation range. Step 3: Determining the optimal gradation: Based on the standard asphalt content of AC-type asphalt mixtures in similar projects already built at the airport location, the initial asphalt content was selected within the range of 3.5% to 5.0%. Marshall specimens were formed using the three synthetic aggregate gradations designed in step two, and then uniaxial compression tests were conducted. Based on the results of the uniaxial compression tests, the aggregate gradation used in the Marshall specimen with the highest high-temperature compressive strength was taken as the optimal gradation. Step 4: Selection of Asphalt Dosage for the Test: (1) Taking the initial asphalt dosage selected in step three as the median, and taking 2 to 3 asphalt dosages above and below the median at intervals of 0.5%, so as to obtain 5 to 7 test asphalt dosages; (2) Using the optimal gradation determined in step three, 5 to 7 groups of Marshall specimens were formed, and the volumetric properties and high-temperature compressive strength of the 5 to 7 groups of Marshall specimens were tested. The volumetric properties included: bulk density ρ, void fraction VTM, asphalt saturation VFA, and aggregate void ratio VMA. The void fractions of the 5 to 7 groups of Marshall specimens were compared, and the smallest void fraction was recorded as VTM. min The maximum porosity is denoted as VTM. max VTM min To VTM max The values ​​between these ranges represent a data range; using VTM min ~VTM max The condition is that the asphalt content is 3% to 5% and the high temperature compressive strength reaches its peak. If the condition is met, the optimal asphalt content is calculated according to step five. If the condition is not met, return to step four (1) to reselect the test asphalt content, and then proceed with the operation step by step. Step 5: Calculate the optimal amount of asphalt: (1) Using high-temperature compressive strength, bulk density ρ, porosity VTM, and asphalt saturation VFA as test indicators, the asphalt content OAC1 is calculated according to the following method based on the changes of each test indicator with asphalt content: ① If the range of asphalt saturation VFA values ​​in the curve of asphalt saturation versus asphalt dosage includes the required range of asphalt saturation for asphalt mixtures, and the bulk density ρ shows a peak value in the curve of bulk density versus asphalt dosage; find the asphalt dosage a1 corresponding to the peak value of high-temperature compressive strength in the curve of high-temperature compressive strength versus asphalt dosage, select a certain value within the range of 3% to 5% as the target void ratio, find the asphalt dosage a2 corresponding to the target void ratio in the curve of void ratio VTM versus asphalt dosage, find the asphalt dosage a3 corresponding to the peak value of bulk density ρ in the curve of bulk density versus asphalt dosage, and find the asphalt dosage a4 corresponding to the median value of asphalt saturation in the curve of asphalt saturation VFA versus asphalt dosage, and calculate the asphalt dosage OAC1 using the following formula: OAC1=(a1×0.4)+(a2×0.2)+(a3×0.2)+(a4×0.2); ② If the range of asphalt saturation VFA values ​​in the curve of asphalt saturation versus asphalt dosage includes the required range of asphalt saturation for asphalt mixtures, and the bulk density ρ does not show a peak value in the curve of bulk density versus asphalt dosage, then the asphalt dosage OAC1 can be calculated using the following formula: OAC1=(a1×0.4)+(a2×0.3)+(a4×0.3); ③ If the range of asphalt saturation VFA values ​​in the curve of asphalt saturation versus asphalt dosage does not include the required range of asphalt saturation for the asphalt mixture, and the bulk density ρ shows a peak value in the curve of bulk density versus asphalt dosage, then the asphalt dosage OAC1 should be calculated using the following formula: OAC1=(a1×0.4)+(a2×0.3)+(a3×0.3); ④ If the range of asphalt saturation VFA values ​​in the curve of asphalt saturation VFA versus asphalt dosage does not include the required range of asphalt saturation for asphalt mixtures, and the bulk density ρ does not show a peak value in the curve of bulk density versus asphalt dosage, then the asphalt dosage OAC1 should be calculated using the following formula: OAC1 = (a1 × 0.5) + (a2 × 0.5); The specific range of the asphalt saturation VFA requirement for asphalt mixtures in steps 5 (1) ①~④ is as follows: if the asphalt mixture is AC-25, the required range of asphalt saturation VFA is 55%~70%; if the asphalt mixture is AC-16 or AC-20, the required range of asphalt saturation VFA is 65%~75%. (2) The technical requirements are: a void ratio (VTM) of 3% to 5%, an asphalt saturation (VFA) within the required range, and a high-temperature compressive strength that meets the engineering indicators for the corresponding high-temperature climate zone and air traffic volume of the airport location; when the void ratio (VTM) is 3% to 5%, the corresponding asphalt dosage is OAC. VTMmin ~OAC VTMmax When the asphalt saturation VFA meets the required range, the corresponding asphalt dosage is OAC. VFAmin ~OAC VFAmax When the high-temperature compressive strength meets the engineering indicators for the corresponding high-temperature climate zone and air traffic volume of the airport location, the corresponding asphalt dosage is OAC. Gmin ~OAC Gmax Calculate the intersection of the three asphalt dosages mentioned above, using the lower bound of the intersection as OAC. min The upper limit of the intersection is OAC. max The asphalt content OAC2 is calculated using the following formula: OAC2=(OAC min +OAC max ) / 2; The required range for asphalt saturation VFA is as follows: if the asphalt mixture is AC-25, the required range for asphalt saturation VFA is 55% to 70%; if the asphalt mixture is AC-16 or AC-20, the required range for asphalt saturation VFA is 65% to 75%. The high-temperature compressive strength meets the engineering requirements of the corresponding high-temperature climate zone and air traffic volume of the airport location, as detailed in Table 1. Table 1 (3) The lower limit of the intersection of the three asphalt dosages in step five (2) is the OAC. min The upper limit of the intersection of the three asphalt usage amounts is OAC. max The optimal asphalt content (OAC) is determined using the following method; ① If OAC1 is in OAC min ~OAC max Within this range, OAC1 is considered the optimal asphalt content (OAC). ② If OAC1 is in OAC min ~OAC max In addition, the average values ​​of OAC1 and OAC2 in OAC min ~OAC max Within this range, the average value of OAC1 and OAC2 is taken as the optimal asphalt content OAC. ③ If OAC1 and the average of OAC1 and OAC2 are both within OAC... min ~OAC max Otherwise, return to step one to reselect raw materials or step two to redesign the ore gradation, and then proceed with the steps in sequence. Step Six: Optimal Asphalt Dosage Verification Based on the optimal asphalt content (OAC) calculated in step five and the optimal gradation determined in step three, Marshall specimens were molded to verify whether the volumetric properties and high-temperature compressive strength met the technical requirements. The void fraction (VTM) of the Marshall specimen was used as the design void fraction. The volumetric properties and high-temperature compressive strength requirements are shown in Tables 2 and 3. Table 2 In Table 2, if the design void ratio is an integer, select the corresponding aggregate void ratio VMA requirement value from the table based on the nominal maximum particle size and the asphalt mixture type. If the design void ratio is not an integer, for AC-25 type asphalt mixture with a nominal maximum particle size of 26.5mm, the aggregate void ratio VMA requirement value is design void ratio + 8%; for AC-20 type asphalt mixture with a nominal maximum particle size of 19mm, the aggregate void ratio VMA requirement value is design void ratio + 9%; and for AC-16 type asphalt mixture with a nominal maximum particle size of 16mm, the aggregate void ratio VMA requirement value is design void ratio + 9.5%. Table 3 If the volumetric properties and high-temperature compressive strength of the formed Marshall specimen do not meet the technical requirements in Tables 2 and 3, return to step one to reselect raw materials or redesign the aggregate gradation in step two, and then proceed with the steps in sequence; if the volumetric properties and high-temperature compressive strength of the formed Marshall specimen meet the technical requirements in Tables 2 and 3, proceed to step seven. Step 7: Performance Verification Based on the optimal asphalt content (OAC) calculated in step five and the optimal gradation determined in step three, specimens are molded. The specimens must meet the technical requirements in Tables 2 and 3. Low-temperature crack resistance and water stability are verified on the specimens. Low-temperature crack resistance is verified through a low-temperature bending test, with the maximum flexural strain as the indicator. Water stability is verified through a freeze-thaw splitting test, with the residual strength ratio as the indicator. If the verification results meet the technical requirements, the mix design is completed; otherwise, return to step one to reselect raw materials or step two to redesign the aggregate gradation, and then proceed with the steps sequentially. The technical requirements are: residual strength ratio ≥ 85%, and maximum flexural strain is shown in Table 4. Table 4 2. The method for designing the mix proportion of AC-type airport asphalt mixture based on high-temperature rutting resistance as described in claim 1, characterized in that... The additive is one or a mixture of several of the following: anti-rutting agent, high modulus agent, and high viscosity agent.

3. A mix design method for AC-type airport asphalt mixture based on high-temperature rutting resistance, as described in claim 1 or 2, characterized in that... The additives comprise 0.5% to 1.0% of the total mass of coarse aggregate, fine aggregate, mineral powder, and asphalt.

4. The method for designing the mix proportion of AC-type airport asphalt mixture based on high-temperature rutting resistance as described in claim 1, characterized in that... The uniaxial compression test described in step three is conducted at a temperature of 60°C and a loading rate of 2 mm / min.

5. The method for designing the mix proportion of AC-type airport asphalt mixture based on high-temperature rutting resistance as described in claim 1, characterized in that... Table 1 shows that in the hot summer areas, the average daily maximum temperature of the hottest month is greater than 30℃; in the hot summer areas, the average daily maximum temperature of the hottest month is between 20℃ and 30℃; and in the cool summer areas, the average daily maximum temperature of the hottest month is less than 20℃. Heavy transportation is defined as having an average annual number of takeoffs greater than 50,000 for Category C and above aircraft types within the design life of a single runway; medium transportation is defined as having an average annual number of takeoffs between 15,000 and 50,000 for Category C and above aircraft types within the design life of a single runway; and light transportation is defined as having an average annual number of takeoffs less than 15,000 for Category C and above aircraft types within the design life of a single runway.

6. The method for designing the mix proportion of AC-type airport asphalt mixture based on high-temperature rutting resistance as described in claim 1, characterized in that... Table 3 shows that in the hot summer areas, the average daily maximum temperature of the hottest month is greater than 30℃; in the hot summer areas, the average daily maximum temperature of the hottest month is between 20℃ and 30℃; and in the cool summer areas, the average daily maximum temperature of the hottest month is less than 20℃. For heavy transportation, the average annual number of takeoffs for Category C and above aircraft types within the design life of a single runway is greater than 50,000; for medium transportation, the average annual number of takeoffs for Category C and above aircraft types within the design life of a single runway is between 15,000 and 50,000; and for light transportation, the average annual number of takeoffs for Category C and above aircraft types within the design life of a single runway is less than 15,000.

7. The method for designing the mix proportion of AC-type airport asphalt mixture based on high-temperature rutting resistance according to claim 1, characterized in that... Table 4 shows that the minimum daily extreme temperature in winter with 99% reliability is less than -37℃ in the severe winter region, between -37℃ and -21.5℃ in the cold winter region, between -21.5℃ and -9℃ in the frigid winter region, and greater than -9℃ in the temperate winter region.

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