CN115081058A - Method for estimating optimal asphalt dosage in Marshall mix proportion design - Google Patents

Method for estimating optimal asphalt dosage in Marshall mix proportion design Download PDF

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CN115081058A
CN115081058A CN202210555303.4A CN202210555303A CN115081058A CN 115081058 A CN115081058 A CN 115081058A CN 202210555303 A CN202210555303 A CN 202210555303A CN 115081058 A CN115081058 A CN 115081058A
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asphalt
oac
dosage
void ratio
interval
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马士杰
夏雨
王昊
韦金城
胡家波
李永振
杨永富
孙强
李广
孙岳
符东绪
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Shandong Hi Speed Co Ltd
Shandong Transportation Institute
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Shandong Hi Speed Co Ltd
Shandong Transportation Institute
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Abstract

The invention relates to the technical field of road engineering, in particular to a method for estimating the optimal asphalt dosage in Marshall mix proportion design, which comprises the steps of determining the design technical requirement of volume index values and calculating the basic parameters of asphalt mixtures according to the types, nominal maximum particle sizes and gradation of the asphalt mixtures, primarily determining asphalt dosage intervals, grouping the asphalt dosages and the void ratios in the intervals according to certain intervals, calculating the volume index values of different asphalt dosages under different void ratios, determining the intersection of asphalt dosage ranges of which the volume index values meet the design requirement under the condition of each void ratio according to a graphical method, calculating the interval of the optimal asphalt dosage according to the end values of the intersection, and then calculating the optimal asphalt dosage by combining key sieve pores and maximum particle size parameters. The method fills the blank that the prior standard Marshall mix proportion design has no optimal asphalt consumption estimation method, and solves the problem that the estimation is inaccurate because the prior mix proportion design can only be estimated through engineering experience.

Description

Method for estimating optimal asphalt dosage in Marshall mix proportion design
Technical Field
The invention relates to the technical field of road engineering, in particular to a method for estimating the optimal asphalt dosage in Marshall mix proportion design.
Background
The pavement surface layer of the highway mainly takes asphalt mixture as main material, and the consumption of asphalt in the asphalt mixture has great influence on the pavement performance of the asphalt pavement. When the amount of selected asphalt is small, the thickness of the asphalt film on the surface of the aggregate is too thin, and the mixture lacks of binding power, so that the mixture has poor durability, and is easy to have diseases such as water damage, asphalt aging and the like; however, with the increase of the asphalt dosage, the binding power of the mixture is gradually enhanced, the thickness of the asphalt film on the surface of the aggregate is increased, the free asphalt becomes more, and the free asphalt is like a lubricant among the aggregates after reaching a certain degree, so that the particles generate sliding displacement under the action of load, the mixture is oiled, rutted and the like, and the driving safety is influenced, so that the proper asphalt dosage is particularly important for the road performance of the asphalt pavement.
The mix proportion design of the asphalt mixture in China is mainly based on a Marshall method, the determination of the optimal asphalt dosage during the mix proportion design is to perform Marshall test on a plurality of groups of asphalt dosages, analyze and calculate the measured volume index value to determine the optimal asphalt dosage, usually 2-3 weeks are needed for the mix proportion design, the method is complex, and the test period is long. Meanwhile, the selection of the primarily selected asphalt dosage is estimated on the basis of local practical experience, no relevant test and estimation methods exist, in the American SHRP plan, the estimation of the primarily selected asphalt dosage in the superpave mix design method is only suitable for common dense-graded asphalt mixtures, and the determined asphalt dosage is often greatly different from the target mix asphalt dosage and is not suitable for the determination of the asphalt dosage in the Marshall mix design method, so that the method for estimating the optimal asphalt dosage by reasonable Marshall mix design is particularly critical.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a prediction method of the optimal asphalt usage amount in Marshall mix proportion design, provides estimation of the asphalt usage amount for the Marshall mix proportion design method of the asphalt mixture, has accurate prediction method, and can effectively shorten the design period.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for estimating optimal asphalt dosage in Marshall design method includes determining design technical requirement of volume index value and calculating basic parameters of asphalt mixture according to asphalt mixture type, nominal maximum particle size and grading, primarily determining asphalt dosage interval, grouping asphalt dosage and void ratio in interval according to certain interval, calculating volume index value of different asphalt dosages under different void ratios, determining intersection of asphalt dosage range of each volume index value meeting design requirement under each void ratio condition according to graphical method, calculating interval of optimal asphalt dosage according to end value of intersection, and calculating optimal asphalt dosage by combining key sieve mesh and maximum particle size parameters.
The estimation method provided by the invention does not need to carry out Marshall test, volume index prediction is carried out by dividing the asphalt dosage and the void ratio into a plurality of groups, the range of the optimal asphalt dosage is determined by using a graphical method, and the estimated optimal asphalt dosage can be calculated by combining key sieve pore parameters. The method fills the blank that the prior standard Marshall mix proportion design does not have the optimal asphalt usage estimation method, and solves the problem that the estimation is inaccurate because the estimation can only be carried out through engineering experience before the mix proportion design in the prior art. Meanwhile, the estimated optimal asphalt consumption of the method omits the previous complicated process of determining the actual optimal asphalt consumption by at least 5 Marshall tests, greatly shortens the design time and improves the design efficiency; compared with the estimation method for the asphalt use amount of superpave mix proportion design, the estimation method is based on the idea of the Marshall mix proportion design method, the estimated asphalt use amount meets the requirement of Marshall mix proportion design better, is closer to the target mix proportion, improves the design efficiency and ensures the design accuracy.
The estimation method comprises the following steps:
s1, determining Marshall mix proportion design technical requirements and basic parameters:
determining the design technical requirement of the volume index value and calculating the basic parameters of the asphalt mixture according to the type, the nominal maximum grain diameter and the gradation of the asphalt mixture;
s2, calculating and enumerating all volume index values according to the assumed asphalt usage and void fraction values:
preliminarily determining asphalt dosage interval according to engineering experience, and respectively recording asphalt dosage in interval as P 1 、P 2 ···P n In the interval VV determined in step S1, the void ratios VV in the interval are written as VV at regular intervals 1 、VV 2 ···VV m Calculating the amount P of different asphalts according to the basic parameters determined in step S1 n At different void ratios VV m Volume index values of: mineral aggregate void fraction VMA m(n) Asphalt saturation VFA m(n) Powder-to-gel ratio FB m(n) And thickness DA of asphalt film m(n) (ii) a Enumerating the asphalt usage and the corresponding volume index values under each void ratio condition:
void ratio VV 1 Each volume index value under the conditions:
Figure BDA0003654716150000031
void ratio VV 2 Each volume index value under the conditions:
Figure BDA0003654716150000032
……
void ratio VV m Each volume index value under the conditions:
Figure BDA0003654716150000033
s3, determining the asphalt dosage range OAC with each volume index meeting the design requirement of the step S1 under the condition of each void ratio determined by a graphical method min(m) ～OAC max(m) ；
S4, determining an optimal asphalt dosage interval:
according to the range of the using amount of the asphalt OAC under various void ratio conditions min(m) ～OAC max(m) Calculating its union range OAC min ～OAC max ，
OAC min ～OAC max ＝{OAC min(1) ～OAC max(1) }∪{…}U{OAC min(m) ～OAC max(m) }；
S5, determining the optimal asphalt using amount:
using the optimum asphalt dosage range OAC min ～OAC max And calculating the optimum asphalt dosage OAC by combining the key sieve pores and the related parameters of the maximum particle size, wherein the formula is as follows:
Figure BDA0003654716150000034
in the formula: p PCS Percent of the passing rate of key sieve pores in the synthetic grading; d pcs Is a key sieve pore in the synthetic grading, which is mm; p NAS The percentage of the maximum particle size passing rate in the synthetic grading is 100 percent; d NAS The maximum particle size in the synthetic grading, mm. The voids in the asphalt mixture are mainly beneficialAnd filling the asphalt with fine aggregates, wherein the content of the fine aggregates is a main factor influencing the optimal asphalt using amount, the using amount of the fine aggregates is mainly controlled through the key sieve pores, and the degree of deviation of the key sieve pore passing rate from the maximum density line is established, so that the calculated optimal asphalt using amount and the target mix proportion asphalt using amount have small error.
Preferably, in step S1, the design specification includes: void ratio VV, mineral aggregate void ratio VMA, asphalt saturation VFA, powder-to-gel ratio FB and asphalt film thickness DA; the basic parameters include: relative density of asphalt gamma b Synthetic mineral aggregate bulk relative density gamma sb Effective relative density of synthetic mineral aggregate gamma se The mass percentage P of the mineral aggregate absorbing the asphalt ba 0.075mm passage Rate P 0.075 Specific aggregate surface area SA and maximum particle diameter D NSA Key sieve mesh D PCS Synthetic grading key sieve mesh passing rate P PCS And the maximum particle size in the synthetic grading by percentage P NAS (ii) a Further preferably, the basic parameters are calculated according to technical Specification for construction of asphalt and asphalt mixtures for road engineering (JTG E20-2011).
Preferably, in the step S1, when the asphalt mixture type is a dense-graded asphalt mixture, the design requirement range of the porosity VV is 3% to 6%; the powder-to-gel ratio FB is required to be 0.8-1.6; the design requirement of the thickness DA of the asphalt film is not less than 6 μm; the asphalt saturation VFA root is selected as the nominal maximum particle size: when D is NMAS When the diameter is 4.75mm and 9.5mm, the VFA is 70-85 percent, and when the diameter is D NMAS VFA of between 65 and 75 percent when the diameter is 13.2mm, 16mm and 19mm, and D is NMAS When the diameter is 26.5mm, 31.5mm and 37.5mm, the VFA is 55 to 70 percent; the mineral aggregate void ratio VMA is calculated according to the void ratio VV range according to the following formula:
VMA＝VV-2.925ln(D NMAS )+17.531
in the formula, VMA is the mineral aggregate clearance rate,%, and 1 decimal place is taken; VV is void fraction,%; d NMAS Is the nominal maximum particle size, mm.
Specifically, in the step S1, when the asphalt mixture type is a dense-graded asphalt mixture, the volume index values are as follows:
TABLE 1 volume index value of dense-graded asphalt mixture
Figure BDA0003654716150000041
Figure BDA0003654716150000051
Preferably, in step S1, when the asphalt mixture type is an SMA asphalt mixture, the design requirement range of the void ratio VV is 3% to 4.5%, the design requirement range of the mineral aggregate void ratio VMA is 17% to 18.5%, the design requirement range of the asphalt saturation VFA is 75% to 85%, and the design requirement ranges are not set for the powder-to-gel ratio FB and the asphalt film thickness DA.
Preferably, in the step S2, in order to ensure the accuracy of the estimation of the asphalt usage amount, the interval of the asphalt usage amount is 0.1%; the interval of the void ratio is 0.1 to 0.5 percent; preferably, when the difference between the estimated asphalt usage and the target mix proportion asphalt usage is acceptable within the range of +/-0.25%, the interval of the void ratio can be selected to be 0.5%, so that the overall calculated amount is reduced, and the estimation efficiency of the estimation method is further improved.
Preferably, in the step S2, the asphalt dosage P is n And a void ratio VV m Under the condition, each volume index value calculation method is as follows:
Figure BDA0003654716150000052
Figure BDA0003654716150000053
Figure BDA0003654716150000054
Figure BDA0003654716150000055
in the above formula, VMA m(n) Mineral void fraction; gamma ray n Theoretical maximum relative density, dimensionless; VV m Void fraction; gamma ray sb The volume relative density of the synthetic mineral aggregate wool is dimensionless; p m The amount of asphalt used; VFA m(n) The asphalt saturation; FB (full Fall Back) m(n) Powder-to-gel ratio; p is 0.075 0.075mm pass rate; p ba The mass percentage of the mineral aggregate absorbing the asphalt; DA m(n) Thickness of asphalt film, μm; rho b Asphalt relative density, dimensionless; SV, aggregate specific surface area, m 2 /Kg。
Preferably, in step S3, the specific steps are as follows:
a. firstly, under the condition of each porosity, calculating the asphalt using amount and the volume index interval of which the volume index meets the design technical requirement of the step S1:
void ratio VV 1 Each volume index value under the conditions:
Figure BDA0003654716150000061
void ratio VV 2 Each volume index value under the conditions:
Figure BDA0003654716150000062
……
void ratio VV m Each volume index value under the condition:
Figure BDA0003654716150000063
b. calculating the range of the asphalt dosage union under each void ratio condition, wherein the asphalt dosage is bound to be in the range under the condition of certain void ratio and meeting the design index,
void ratio VV 1 The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(1) ～OAC max(1) ＝{P 1a ～P 1b }∩{P 1c ～P 1d }∩{P 1e ～P 1f }∩{P 1g ～P 1h }
void ratio VV 2 The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(2) ～OAC max(2) ＝{P 2a ～P 2b }∩{P 2c ～P 2d }∩{P 2e ～P 2f }∩{P 2g ～P 2h }
……
void ratio VV m The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(m) ～OAC max (m)＝{P ma ～P mb }∩{P mc ～P md }∩{P me ～P mf }∩{P mg ～P mh }。
preferably, in step S3, OAC min(m) All the numerical values in the asphalt mixture are larger than the lower limit value P of the use amount of the selected asphalt 1 And OAC max(m) All the numerical values in the asphalt mixture are less than the upper limit value P of the use amount of the selected asphalt n Otherwise, the asphalt using amount interval is reselected, and the calculation of the step S2 is carried out again until the requirement is met; it is further preferred that when the interval of asphalt dosage is re-selected, if OAC is used min(m) In which a number is equal to P 1 The lower limit of the asphalt using amount interval is enlarged according to the interval value in step S1, and if OAC is used max(m) In which a number is equal to P n Expanding the upper limit of the asphalt using amount interval according to the interval value in the step S1 until OAC appears min(m) All the numerical values are greater than the lower limit value P of the selected asphalt dosage 1 And OAC max(m) All the numerical values are less than the upper limit value P of the selected asphalt dosage n Until now.
Preferably, in the step S5, the maximum particle size and the key sieve pore corresponding to each nominal maximum particle size are selected according to "technical specification for constructing asphalt road surface for road" (JTG F40-2004), and specifically, the values are as shown in the following table:
TABLE 2 maximum particle size and Key Sieve mesh for each nominal maximum particle size
Figure BDA0003654716150000071
The invention has the beneficial effects that:
1. the estimation method provided by the invention does not need to carry out Marshall test, volume index value calculation is carried out by dividing the asphalt dosage and the void ratio into a plurality of groups, the range of the optimal asphalt dosage is determined by using a graphical method, and the estimated optimal asphalt dosage can be calculated by combining key sieve pore parameters. The method fills the blank that the prior standard Marshall mix proportion design does not have the optimal asphalt usage estimation method, and solves the problem that the estimation is inaccurate because the estimation can only be carried out through engineering experience before the mix proportion design in the prior art. Meanwhile, the estimated optimal asphalt consumption of the method omits the previous complicated process of determining the actual optimal asphalt consumption by at least 5 Marshall tests, greatly shortens the design time and improves the design efficiency; compared with the estimation method for the asphalt use amount of superpave mix proportion design, the estimation method is based on the idea of the Marshall mix proportion design method, the estimated asphalt use amount meets the requirement of Marshall mix proportion design better, is closer to the target mix proportion, improves the design efficiency and ensures the design accuracy.
2. According to the invention, the asphalt usage and the corresponding volume index value under each void ratio are calculated and enumerated at certain intervals according to the asphalt usage and the void ratio, the asphalt usage interval meeting the design requirement under each void ratio condition is calculated through a graphical method, then all the asphalt usage intervals are calculated, the optimal asphalt usage is necessarily in the range, and when the asphalt usage exceeding the range is not necessarily in accordance with the design requirement, the selection range of the optimal asphalt usage is greatly shortened, and the estimation accuracy is improved.
3. After the optimal asphalt dosage range is determined, the degree of deviation of the key sieve pore passing rate from the maximum density line is established, and the OAC can be in the optimal asphalt dosage range min ～OAC max And the optimal asphalt dosage OAC is calculated, so that the accuracy of predicting the optimal asphalt dosage is effectively improved.
Drawings
FIG. 1 is the result of enumeration of volume index values in example 1;
FIG. 2 is a graph of the range analysis of the amount of pitch at 3.5% void in example 1;
FIG. 3 is a graph of the range of asphalt usage at 4.0% void fraction in example 1;
FIG. 4 is a plot of the range of asphalt loading at 4.5% void fraction for example 1;
FIG. 5 is a plot of the range of asphalt loading at 5.0% void fraction for example 1;
fig. 6 is a flow chart of the steps of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Example 1:
estimating the optimal asphalt dosage value of the AC-20 asphalt mixture, determining the design technical requirement of volume index values and calculating the basic parameters of the asphalt mixture according to the type, the nominal maximum particle size and the grading of the asphalt mixture, primarily determining an asphalt dosage interval, grouping the asphalt dosage and the void fraction in the interval at certain intervals, calculating the volume index values of different asphalt dosages under different void fractions, determining the intersection of asphalt dosage ranges of which the volume index values meet the design requirement under each void fraction condition according to a graphical method, calculating the interval of the optimal asphalt dosage according to the end value of the intersection, and then calculating the optimal asphalt dosage by combining key sieve pores and the maximum particle size parameters,
as shown in fig. 6, the specific estimation steps are as follows:
s1, determining the technical requirements and basic parameters of Marshall mix proportion design of AC-20 asphalt mixture
In this example, the AC-20 asphalt mixture is calculated, and the basic parameters and the design technical requirements are as follows:
TABLE 3 AC-20 asphalt mixture design technical requirements
VV(％) VMA(％) VFA(％) FB DA(μm)
3～6 12～15 65～75 0.8～1.6 ≥6
Relative density of asphalt gamma b Synthetic mineral aggregate bulk relative density gamma sb Effective relative density of synthetic mineral aggregate gamma se The mass percentage P of the mineral aggregate absorbing the asphalt ba 0.075mm passage Rate P 0.075 Specific aggregate surface area SA and maximum particle diameter D NSA Key sieve mesh D PCS Synthetic grading key sieve mesh passing rate P PCS ；
TABLE 4 basic parameters of AC-20 asphalt mixture
Figure BDA0003654716150000091
S2, calculating and enumerating all volume index values according to the assumed asphalt usage and void fraction values:
according to past engineering experience, the asphalt dosage interval P n 3.0% -6.0% of the initial selection is carried out, and the asphalt usage in the interval is spaced according to 0.1%, which respectively comprises the following steps: 3.0%, 3.1%, 3.2%, … 6.0.0%; void ratio VV m 3.0-6.0% is selected according to the design requirement interval, and the acceptable error range of the estimation result is +/-0.25%Therefore, to reduce the amount of calculation, at 0.5% intervals, are: 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%; respectively calculating and enumerating volume index values corresponding to the asphalt usage under the void ratio conditions, wherein the calculation formula is as follows:
Figure BDA0003654716150000092
Figure BDA0003654716150000093
Figure BDA0003654716150000094
Figure BDA0003654716150000095
in the above formula, VMA m(n) Mineral void fraction; theoretical maximum relative density gamma n No dimension; VV m Void fraction; gamma ray sb The volume relative density of the synthetic mineral aggregate wool is dimensionless; p m The amount of asphalt used; VFA m(n) The asphalt saturation; FB (full Fall Back) m(n) Powder-to-gel ratio; p 0.075 0.075mm pass rate; p ba The mass percentage of the mineral aggregate absorbing the asphalt; DA m(n) Thickness of asphalt film, μm; rho b Asphalt relative density, dimensionless; SA, aggregate specific surface area, m 2 /Kg；
The asphalt usage and the corresponding volume index values under each void ratio condition are enumerated as shown in FIG. 1:
the index value of each volume under the condition of 3.0 percent of void ratio is as follows:
Figure BDA0003654716150000101
the index value of each volume under the condition of 3.5 percent of void ratio:
Figure BDA0003654716150000102
······
the index value of each volume under the condition of 6.0 percent of void ratio is as follows:
Figure BDA0003654716150000103
s3, determining the asphalt dosage range OAC with each volume index meeting the design requirement of the step S1 under the condition of each void ratio by a graphical method according to the following steps min(m) ～OAC max(m) ，
a. Firstly, calculating the asphalt usage and volume index interval with the volume index meeting the design technical requirement of step S1 under each void ratio condition, as indicated by the filling shadow indicated by the numerical value shown in fig. 1:
void ratio VV 1 Each volume index value under the conditions:
Figure BDA0003654716150000104
void ratio VV 2 Each volume index value under the conditions:
Figure BDA0003654716150000105
……
void ratio VV m Each volume index value under the conditions:
Figure BDA0003654716150000106
b, calculating the range of the union set of the asphalt use amounts under each porosity condition, wherein the asphalt use amount is bound to be within the range under the condition that the porosity is certain, the graphical method is shown as figures 2-5, wherein the abscissa in each figure is the asphalt use amount (%), and the abscissa in each figure sequentially comprises VMA, DA, FB and VFA from top to bottom, and the range of the asphalt use amount meeting the design requirement (i.e. the overlapping part of four horizontal lines parallel to the abscissa in figures 2-5) under each porosity condition is calculated as follows:
TABLE 5 range of asphalt dosage satisfying design requirements under each void fraction condition
VV m (％) OAC min(m) (％) OAC max(m) (％)
3.0 — —
3.5 4.1 4.9
4.0 3.9 5.1
4.5 4.1 4.9
5.0 4.5 4.7
5.5 — —
6.0 — —
；
S4, determining an optimal asphalt dosage interval:
according to the range of the using amount of the asphalt OAC under various void ratio conditions min(m) ～OAC max(m) Calculating its union range OAC min ～OAC max Namely, the optimum asphalt dosage interval, and the interval range must be all asphalt dosage intervals meeting the design requirements:
OAC min ～OAC max ＝{4.1～4.9}U{3.9～5.1}U{4.1～4.9}U{4.5～4.7}＝3.9％～5.1％；
s5, determining the optimal asphalt using amount:
the gaps of the asphalt mixture are mainly filled by fine aggregates, the content of the fine aggregates is a main factor influencing the optimal asphalt dosage, the dosage of the fine aggregates is mainly controlled by the key sieve pores, the degree of deviation of the key sieve pore passing rate from the maximum density line is established, and the OAC can be in the optimal asphalt dosage interval min ～OAC max The optimal asphalt dosage OAC is given priority, and the formula is as follows:
Figure BDA0003654716150000111
Figure BDA0003654716150000112
in the formula: p PCS Percent of the passing rate of key sieve pores in the synthetic grading; d pcs Is a key sieve pore in the synthetic grading, which is mm; p NAS The percentage of the maximum particle size passing rate in the synthetic grading is 100 percent; d NAS The maximum particle size in the synthetic grading, mm.
Therefore, in the embodiment, the optimal asphalt usage amount of the AC-20 asphalt mixture is estimated to be 4.4%, the target mix proportion asphalt usage amount is 4.4%, and the estimated value is consistent with the target mix proportion asphalt usage amount.
Verification example 1:
the accuracy of the method in the AC type dense-graded asphalt mixture is verified, the estimation method of the asphalt using amount is carried out in the same way as example 1, and the statistical result is as follows in AASHTO R35 appendix X1 in the American standard of the superpave estimation method:
Figure BDA0003654716150000121
compared with the asphalt using amount determined by the target mix proportion design, the estimated asphalt using amount of the method is equivalent to the asphalt using amount determined by the target mix proportion, the maximum difference is only 0.12%, and the maximum difference between the estimated asphalt using amount and the determined asphalt using amount is-0.58% and is far larger than the difference of the estimated value of the method, so that the estimation of the method is accurate in AC type dense-graded asphalt mixture compared with the conventional superpave method.
Verification example 2:
the accuracy of the method in ATB asphalt stabilized macadam is verified, the estimation method of the asphalt using amount is carried out in the same way as example 1, and the statistical result is as follows in AASHTO R35 appendix X1 in the American standard of superpave estimation method:
Figure BDA0003654716150000122
compared with the asphalt using amount determined by the target mix proportion design, the estimated asphalt using amount of the method is equivalent to the asphalt using amount determined by the target mix proportion, the maximum difference is only 0.08%, the maximum difference between the estimated asphalt using amount and the determined asphalt using amount is 0.18%, and the estimation of the method in the ATB dense-graded asphalt mixture is accurate compared with the conventional superpave method.
Verification example 3:
the accuracy of the method in the SMA asphalt mixture is verified, the estimation method of the asphalt amount is carried out in the same way as example 1, and the statistical result is as follows in AASHTO R35 appendix X1 in the American standard of superpave estimation method:
Figure BDA0003654716150000131
compared with the asphalt using amount determined by the target mixing proportion design, the estimated asphalt using amount of the method is equivalent to the asphalt using amount determined by the target mixing proportion, the maximum difference is only 0.23 percent, the maximum difference between the estimated asphalt using amount and the determined asphalt using amount is-1.34 percent, the deviation is extremely large, the method is not suitable for the estimation of the asphalt using amount of the SMA asphalt mixture, and the method for estimating the asphalt using amount is accurate.

Claims (10)

1. A method for estimating optimal asphalt dosage in Marshall design method is characterized in that according to asphalt mixture type, nominal maximum grain diameter and grading, the design technical requirement of volume index value is determined and the basic parameters of asphalt mixture are calculated, the asphalt dosage interval is primarily determined, the asphalt dosage and void ratio in the interval are respectively grouped according to certain intervals, the volume index value of different asphalt dosages under different void ratios is calculated, the intersection of asphalt dosage ranges of which the volume index values meet the design requirement under each void ratio condition is determined according to a graphical method, the interval of optimal asphalt dosage is calculated according to the end value of the intersection, and then the optimal asphalt dosage is calculated by combining key sieve pores and maximum grain diameter parameters.
2. The prediction method of claim 1, comprising the steps of:
s1, determining Marshall mix proportion design technical requirements and basic parameters:
according to the type of the asphalt mixture and the nominal maximum grain diameter D NMAS Grading, determining the design technical requirement of the volume index value and calculating the basic parameters of the asphalt mixture;
s2, calculating and enumerating all volume index values according to the assumed asphalt usage and void fraction values:
preliminarily determining asphalt dosage interval according to engineering experience, and dividing the asphalt dosage in the interval into a plurality of sections according to certain intervalsRespectively recorded as P 1 、P 2 ···P n In the interval VV determined in step S1, the void ratios VV in the interval are written as VV at regular intervals 1 、VV 2 ···VV m Calculating the amount P of different asphalts according to the basic parameters determined in step S1 n At different void ratios VV m Volume index values of: mineral aggregate void fraction VMA m(n) Asphalt saturation VFA m(n) Powder-to-gel ratio FB m(n) And thickness DA of asphalt film m(n) (ii) a Enumerating the asphalt usage and the corresponding volume index values under each void ratio condition:
void ratio VV 1 Each volume index value under the conditions:
Figure FDA0003654716140000011
void ratio VV 2 Each volume index value under the conditions:
Figure FDA0003654716140000012
……
void ratio VV m Each volume index value under the conditions:
Figure FDA0003654716140000021
s3, determining the asphalt dosage range OAC with each volume index meeting the design requirement of the step S1 under the condition of each void ratio determined by a graphical method min(m) ～OAC max(m) ；
S4, determining an optimal asphalt dosage interval:
according to the range of the using amount of the asphalt OAC under various void ratio conditions min(m) ～OAC max(m) Calculating its union range OAC min ～OAC max ，
OAC min ～OAC max ＝OAC min(1) ～OAC max(1) }∪{…}∪{OAC min(m) ～OAC max(m) }；
S5, determining the optimal asphalt using amount:
using the mostOAC in the interval of optimum asphalt dosage min ～OAC max And calculating the optimum asphalt dosage OAC by combining the key sieve pores and the related parameters of the maximum particle size, wherein the formula is as follows:
Figure FDA0003654716140000022
in the formula: p PCS Percent of the passing rate of key sieve pores in the synthetic grading; d pcs Is a key sieve pore in the synthetic grading, which is mm; p NAS The percentage of the maximum particle size passing rate in the synthetic grading is 100 percent; d NAS The maximum particle size in the synthetic grading, mm.
3. The estimation method as claimed in claim 2, wherein in the step S1, designing the technical requirement includes: void ratio VV, mineral aggregate void ratio VMA, asphalt saturation VFA, powder-to-gel ratio FB and asphalt film thickness DA; the basic parameters include: relative density of asphalt gamma b Synthetic mineral aggregate bulk relative density gamma sb Effective relative density of synthetic mineral aggregate gamma se The mass percentage P of the mineral aggregate absorbing the asphalt ba 0.075mm passage Rate P 0.075 Specific aggregate surface area SA and maximum particle diameter D NSA Key sieve mesh D PCS Synthetic grading key sieve mesh passing rate P PCS And the maximum particle size in the synthetic grading by percentage P NAS (ii) a Further preferably, the basic parameters are calculated according to technical Specification for construction of asphalt and asphalt mixtures for road engineering (JTG E20-2011).
4. The estimation method as claimed in claim 2, wherein in the step S1, when the asphalt mixture type is a dense-graded asphalt mixture, the design requirement range of the void ratio VV is 3% to 6%; the powder-to-gel ratio FB is required to be 0.8-1.6; the design requirement of the thickness DA of the asphalt film is not less than 6 μm; the asphalt saturation VFA root is selected as the nominal maximum particle size: when D is present NMAS When the diameter is 4.75mm and 9.5mm, the VFA is 70-85 percent, and when the diameter is D NMAS VFA is 65%. E.E.E. at 13.2mm, 16mm, 19mm75% when D NMAS When the diameter is 26.5mm, 31.5mm and 37.5mm, the VFA is 55 to 70 percent; the mineral aggregate void ratio VMA is calculated according to the void ratio VV range according to the following formula:
VMA＝VV-2.925ln(D NMAS )+17.531
in the formula, VMA is the mineral aggregate clearance rate,%, and 1 decimal place is taken; VV is void fraction,%; d NMAS Is the nominal maximum particle size, mm.
5. The estimation method as claimed in claim 2, wherein in the step S1, when the asphalt mixture type is SMA asphalt mixture, the design requirement range of the void ratio VV is 3% -4.5%, the design requirement range of the mineral aggregate void ratio VMA is 17% -18.5%, the design requirement range of the asphalt saturation VFA is 75% -85%, and the design requirement ranges of the powder-to-rubber ratio FB and the asphalt film thickness DA are not set.
6. The estimation method according to claim 2, wherein in step S2, in order to ensure the accuracy of estimation of the asphalt dosage, the interval of asphalt dosage is 0.1%; the interval of the void ratio is 0.1 to 0.5 percent; further preferably, when the difference between the predicted asphalt amount and the target mix ratio asphalt amount is acceptable within a range of ± 0.25%, the interval of the void ratio is selected to be 0.5%.
7. The estimation method as claimed in claim 2, wherein, in the step S2, the asphalt dosage P is n And a void ratio VV m Under the condition, each volume index value calculation method is as follows:
Figure FDA0003654716140000031
Figure FDA0003654716140000032
Figure FDA0003654716140000033
Figure FDA0003654716140000034
in the above formula, VMA m(n) Mineral void fraction; gamma ray n Theoretical maximum relative density, dimensionless; VV m Void fraction; gamma ray sb The volume relative density of the synthetic mineral aggregate wool is dimensionless; p is m The amount of asphalt used; VFA m(n) The asphalt saturation; FB (FB) m(n) Powder-to-gel ratio; p 0.075 0.075mm pass rate; p ba The mass percentage of the mineral aggregate absorbing the asphalt; DA m(n) Asphalt film thickness, μm; rho b Asphalt relative density, dimensionless; SA, aggregate specific surface area, m 2 /Kg。
8. The estimation method as claimed in claim 2, wherein in the step S3, the specific steps are as follows:
a. firstly, under the condition of each porosity, calculating the asphalt using amount and the volume index interval of which the volume index meets the design technical requirement of the step S1:
void ratio VV 1 Each volume index value under the conditions:
Figure FDA0003654716140000041
void ratio VV 2 Each volume index value under the conditions:
Figure FDA0003654716140000042
……
void ratio VV m Each volume index value under the conditions:
Figure FDA0003654716140000043
b. calculating the range of the asphalt dosage union set under each void ratio condition,
void ratio VV 1 The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(1) ～OAC max(1) ＝{P 1a ～P 1b }∩{P 1c ～P 1d }∩{P 1e ～P 1f }∩{P 1g ～P 1h }
void ratio VV 2 The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(2) ～OAC max(2) ＝{P 2a ～P 2b }∩{P 2c ～P 2d }∩{P 2e ～P 2f }∩{P 2g ～P 2h }
……
void ratio VV m The intersection range of the use amount of each asphalt under the condition is as follows:
OAC min(m) ～OAC max(m) ＝{P ma ～P mb }∩{P mc ～P md }∩{P me ～P mf }∩{P mg ～P mh }。
9. the estimation method as claimed in claim 2, wherein, in the step S3, OAC min(m) All the numerical values in the asphalt mixture are larger than the lower limit value P of the use amount of the selected asphalt 1 And OAC max(m) All the numerical values in the asphalt mixture are less than the upper limit value P of the dosage of the selected asphalt n Otherwise, the asphalt using amount interval is reselected, and the calculation of the step S2 is carried out again until the requirement is met; it is further preferred that when the interval of asphalt dosage is re-selected, if OAC is used min(m) In which a number is equal to P 1 Expanding the lower limit of the asphalt dosage interval according to the interval value in step S1, and if OAC is adopted max(m) In which a number is equal to P n Expanding the upper limit of the asphalt using amount interval according to the interval value in the step S1 until OAC appears min(m) All the numerical values are greater than the lower limit value P of the selected asphalt dosage 1 And OAC max(m) All the numerical values are less than the upper limit value P of the selected asphalt dosage n Until now.
10. The estimation method as claimed in claim 2, wherein in the step S5, the maximum grain size and the critical sieve aperture corresponding to each nominal maximum grain size are selected according to technical specification for road asphalt pavement construction (JTG F40-2004).
CN202210555303.4A 2022-05-20 2022-05-20 Method for estimating optimal asphalt dosage in Marshall mix proportion design Pending CN115081058A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117010220A (en) * 2023-10-08 2023-11-07 湖南省交通科学研究院有限公司 Determination method for optimal asphalt dosage of steel slag asphalt mixture

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117010220A (en) * 2023-10-08 2023-11-07 湖南省交通科学研究院有限公司 Determination method for optimal asphalt dosage of steel slag asphalt mixture
CN117010220B (en) * 2023-10-08 2023-12-26 湖南省交通科学研究院有限公司 Determination method for optimal asphalt dosage of steel slag asphalt mixture

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