CN104929010A - Method for designing mixing proportion of lower surface layer of asphalt pavement according to structure demands - Google Patents
Method for designing mixing proportion of lower surface layer of asphalt pavement according to structure demands Download PDFInfo
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- CN104929010A CN104929010A CN201510208493.2A CN201510208493A CN104929010A CN 104929010 A CN104929010 A CN 104929010A CN 201510208493 A CN201510208493 A CN 201510208493A CN 104929010 A CN104929010 A CN 104929010A
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Abstract
The invention discloses a method for designing the mixing proportion of the lower surface layer of an asphalt pavement according to structure demands. The method comprises the following steps: 1, performing an impact toughness test on a test specimen, and confirming an asphalt-aggregate ratio range when the ultimate flexural strain is greater than a certain value and an asphalt-aggregate ratio range when the impact toughness which is greater than a certain value is used as control standards; 2, determining an asphalt-aggregate ratio range meeting the fatigue life based on the analysis method of a fatigue fracture test of semicircular split; and 3, determining the asphalt-aggregate ratio ranges meeting the three requirements, and taking the average value as the best application amount of asphalt. The method provided by the invention is performed according to the mechanical state and functional demand standards of the material structure, and the design philosophy of optimal standards is highlighted, so that the good state of materials in working and the long service life of the materials are guaranteed.
Description
Technical field
The present invention relates to a kind of method for designing by topology requirement of asphalt pavement material.
Background technology
The quality requirement of highway in China pavement construction is more and more higher, and road construction person and society more pay close attention to the application life on road surface.Life-span and the design of material of flexible pavement are closely bound up, material property for the useful life longevity of total and functional performance most important.Ensure the using function that cutting optimal is good, be ensure structural integrity, improve structural union stress-bearing capability, strengthen the basic key element of the compatible deformation ability between deck.That is, make the function admirable of cutting optimal, and prior key problem in technology is: by the match ratio of the Demand Design cutting optimal of topology requirement.
Bottom cutting optimal under wheel load effect other position of institute's tension stress specific surface layer wheel approaching or after crossing produce tensile stress much bigger, easily produce fatigue cracking bottom surface layer; In addition, due to base material shrinkage character, determine basic unit and inevitably produce shrinkage crack, cutting optimal resists the forward of reflection crack as first floor, needs the ability having suitable absorption fracture propagation, possesses the ability resisting reflection stress.How to test, analyze, evaluate and determine these functional parameters, thus carry out the mix-design of material, just become very important.
Summary of the invention
The object of this invention is to provide a kind of mixing proportion design method solving the bituminous mixture cutting optimal (i.e. the 10cm lower part of asphalt pavement structure Asphalt Mixture part) related in existing road engineering design and implementation process.
The object of the invention is to be achieved through the following technical solutions:
One, impact ductility test is carried out to test specimen, determine that limit flexural-tensile strain is greater than the bitumen aggregate ratio scope of a certain numerical value (7000), and when being greater than a certain numerical value (0.75N.m) as control criterion using impact toughness, satisfied bitumen aggregate ratio scope;
Two, based on the Fatigue Cracking Test analytical method of semicircle splitting---semicircle splitting fatigue is tested, and determines the bitumen aggregate ratio scope meeting fatigue life (4000 times);
Three, determine the bitumen aggregate ratio scope meeting above-mentioned three index requests, average as asphalt optimum content.
Method for designing in the past does not take into full account difference and the performance requirement of road structure level, and match ratio all adopts identical method for designing, can not fully ensure the structural of material; The compound of design there will be a lot of problem.Method for designing provided by the invention is that the mechanical state that bears for material structure present position and functional requirement index are carried out, and highlights the design concept of index optimum, thus ensures material kilter at work and life-span.
Accompanying drawing explanation
Fig. 1 is delayed loop wire;
Fig. 2 is impact ductility test brittle fracture schematic diagram;
Fig. 3 is impact ductility test yield failure schematic graph;
Fig. 4 is the impact toughness of part test specimen;
Fig. 5 is the maximum flexural-tensile strain relation of bitumen aggregate ratio;
Fig. 6 is the relation of impact toughness and bitumen aggregate ratio;
Fig. 7 is SCB experimental rig;
Fig. 8 is AC25 semicircle splitting fatigue experimental result;
Fig. 9 is the determination schematic diagram of the cutting optimal bituminous mixture optimum oil-stone ratio based on function.
Detailed description of the invention
Below in conjunction with accompanying drawing, technical scheme of the present invention is further described; but be not limited thereto; everyly technical solution of the present invention modified or equivalent to replace, and not departing from the spirit and scope of technical solution of the present invention, all should be encompassed in protection scope of the present invention.
The invention provides a kind of flexible pavement cutting optimal match ratio by the method for designing of topology requirement, can obtain by the following method:
One, stress absorption ability is reflected---impact ductility test
Impact ductility test principle: when load action is on material, material can produce stress and cause strain.In viscoelastic material test specimen, the stress-strain diagram of minute cells body will experience different paths in loading from during off-load and forms a ring-type curve, as shown in Figure 1.
The area of this ring-type curve represents energy savings total in each loading cyclic process usually, is referred to as delayed loop wire.In repetition loading process, with the energy of this delayed loop wire area representative, all or part of is changed into heat energy savings at material internal, heat energy savings makes material generate heat and causes material plasticity to be out of shape, and fatigue failure occurs.Can think, in cyclic loading, unloading process, the energy of store materials is fewer, and the ability that its resisting fatigue is destroyed is stronger.Fatigue life under reloading can represent with formula (1):
N
f＝a(1/W
0)
b(1)；
In formula: N
f---fatigue life, number of times;
A, b---fatigue of materials property coefficients;
W
0---the energy of savings in initial loading circulation, N.m.
Formula (1) shows, in original upload circulation, the energy of material savings is less, and fatigue life is longer.Determine the delayed loop wire of material in initial loading circulation by test, then set up with the fatigue life of material and contact, this is one of means of current fatigue of materials performance study.On the contrary, if do not measure the energy of each loaded cycle savings, but the total energy that mensuration material is put aside before fatigue failure, then the total energy of material savings is larger, and fatigue life is longer.
Wheel load acts on the road speed of time very short 60 ~ 65km/h that rigid pavement connects (splitting) seam relevant position, and to be equivalent to loading speed be 10Hz, and active force is larger, has the feature of obvious impact load.Therefore, if bituminous concrete test specimen can be determined under Impact Load until the load-deformation curve of fracture, so, area under load-deformation curve represent material rupture required for energy, by under Impact Load, the area that load-deformation curve surrounds is called impact toughness, represents, now N with I
f=1,
I＝G(W
0) (2)；
In formula: I---impact toughness, N.m;
G---material impact coefficient.
Formula (2) shows, impact toughness is the function of the energy of savings in original upload circulation, represent the energy put aside before fracture occurs material under Impact Load, be mainly used in Materials Fracture and produce energy required for new surface, the ability of notched bar impact strength larger material repels reflection crack is stronger.
As shown in figures 2-3, the area of dash area represents impact toughness to typical loading-displacement curve.Fig. 2 represents that material loading is ruptured suddenly to maximum load place, and this is the feature of typical brittle fracture.Fig. 3 shows material not fracture suddenly at maximum load place, but distortion continues to increase when unloading gradually, and then rupture, show material generation flow deformation, crackle in the loaded state subcritical expansion causes regional area to unload.Notched bar impact strength is larger, illustrates that the energy that bituminous mixture dissipates is more, and the ability that resisting fatigue is destroyed is stronger, and the ability of namely resisting the lower reflection crack that will cause of Repeated Loading is stronger.
Specific implementation method:
According to " highway engineering pitch and Asphalt Mixture Experiment code " JTJ052-2000, about the code requirement of bitumen mixture specimen preparation method (wheel milling process), make the plate-like test specimen of 300mm × 300mm × 50mm.Cutting machine is utilized by the test specimen of forming to cut into the prism test specimen of 250mm × 35mm × 35mm.For reducing testing error, often organizing test specimen and carrying out 3 parallel test specimens.Specify in specification: the prism test specimen using the compound test specimen cutting of roller-compaction, length is not less than 4 times of the maximum aggregate size of nominal, and width or thickness are not less than 1 ~ 1.5 times of nominal maximum particle diameter.The compound nominal maximum particle diameter that this test adopts is respectively 19mm, 26.5mm, meets code requirement.
The selection of test temperature:
Table 1 lists the temperature statistics (choosing of temperature being described as example) in China somewhere:
Type area's temperature statistics, table 1 somewhere (DEG C)
| Place name | The hottest monthly mean temperature | The coldest monthly mean temperature | Average temperature of the whole year |
| A | 24.2 | -7.7 | 10.6 |
| B | 22.0 | -15.4 | 5.0 |
| C | 26.3 | -10.0 | 10.1 |
| D | 25.7 | -4.1 | 12.9 |
| E | 25.4 | -5.0 | 11.9 |
| F | 27.9 | -7.2 | 12.0 |
| G | 23.3 | -10.0 | 7.7 |
| H | 32.3 | -6.4 | 15.0 |
| I | 23.9 | -12.4 | 7.4 |
| J | 23.4 | -11.0 | 8.9 |
| K | 23.4 | -8.3 | 9.4 |
Known, the average of the hottest monthly mean temperature in each department is 25 DEG C, and the coldest monthly mean temperature average in each department is-8.7 DEG C, and each department average temperature of the whole year average is 10 DEG C.In view of the feature that low-temperature impact destroys, suggestion is got test temperature and is-5 DEG C.
Test procedure:
The bituminous concrete prism test specimen (girder) made is positioned over maintenance 2 ~ 4h in the Water Tank with Temp.-controlled reaching set point of temperature.Should have interval between test specimen, bottom should pave, and distance container bottom is not less than 5cm; Adjustment forcing press, setting loading speed is 500mm/min; From environmental cabinet, take out test specimen, do three point bending test and rupture to test specimen.It should be noted that whole process must complete rapidly, can not more than 1min from taking-up test specimen to off-test, after avoiding girder to take out from curing box, temperature changes as far as possible.
Example: test with the material of certain engineering, adopt 90# pitch, breeze is that unit in charge of construction is self-produced, the confession of building stones factory, and grating adopts AC-25 grating intermediate value.
Fig. 4 lists the result of the test of impact toughness, as can be seen from Figure 4 the difference of the impact toughness of the different oil mass of AC-25.
Visible, the analysis of impact toughness is suitable for the pattern of the brittle fracture of impact toughness curve map 2.
Result of the test gathers in table 2:
The impact ductility test result of table 2 different pitches consumption gathers
Fig. 5 analyzes bitumen aggregate ratio and fracture strength, maximum displacement and maximum flexural-tensile strain relation.
As shown in Figure 5, for AC-25 grating, the experimental result under this temperature, loading velocity and sample dimensions condition is large compared with conventional maximum flexural-tensile strain.In view of the impact of sample dimensions effect, adopt this size carry out testing more reasonable.As considered, limit flexural-tensile strain standard is taken as 7000, then the compound of 4.0 ~ 4.5% scopes meets the demands.
The relation of On Impact Toughness and bitumen aggregate ratio is analyzed, and as shown in Figure 6, the relation of impact toughness and bitumen aggregate ratio is that peak state distributes.Peak point can be found, about between 4.3 ~ 4.4% on curve; If get 0.75Nm, then the bitumen aggregate ratio scope met is 4.1 ~ 4.6%.
Two, based on the Fatigue Cracking Test analytical method of semicircle splitting---semicircle splitting fatigue is tested
In recent years, in Europe with the U.S. is a kind of adopts semicircle test specimen to carry out the curved method tested such as to draw (to be referred to as Semi-Circular Bending Test abroad, be called for short SCB test) more and more attract much attention, this test method can carry out analysis and inspection to the bituminous mixture of multiple forming method.Semi-circular bending test is more suitable for evaluating the curved of bituminous mixture than Indirect Tensile Tests and draws performance, and semi-circular bending test can replace Indirect Tensile Tests completely.
Semi-circular bending test device is (0≤a < R) as shown in Figure 7, and in figure, each parameter meaning is as follows:
P---load, unit N;
R---test specimen radius, unit mm;
A---notch depth, unit mm;
S---length of support, unit mm.
Asphalt Mixtures Fatigue Properties occupies critical role in the performance evaluation of bituminous mixture, in laboratory test, have several evaluation methods and evaluation criterion to the fatigue behaviour of bituminous mixture at present, it is more and more extensive that Method of Fracture Mechanics is applied in highway construction.
Semicircle splitting fatigue is tested: test temperature, its total fracture by fatigue energy when total fracture by fatigue of bituminous mixture can be greater than 15 DEG C when 0 DEG C, this is corresponding with its maximum fatigue life, fatigue life and total fracture by fatigue can have good corresponding relation, the fatigue life that larger total fracture by fatigue can be corresponding longer.In view of mechanism, the thermal climate feature of fatigue failure, test temperature is taken as 15 DEG C.
Trial load: load application is 1800N → 180N, adopts continuous semisinusoidal to load, loading frequency 10Hz.
Experiment material is the same.
Experimental result as shown in Figure 8.
Visible, along with bitumen aggregate ratio increases, fatigue life improves.The cohesion of the compound of the increase of bitumen aggregate ratio increases, and the ability that material absorbs load action increases, from the initial period of curve, and linear approximate relationship; When bitumen aggregate ratio is higher, contracting deformation increases, and the life-span increases upper trend and slows down, and turning point is about positioned at bitumen aggregate ratio 4.5% place.If get fatigue life > 50000 times as control criterion, then bitumen aggregate ratio > 4.24% all meets the demands; In view of bitumen aggregate ratio increases the contribution for fatigue life, get 4.5%+0.15%=4.65% when considering economy, that is, turning point+0.15%, as upper control limit.The bitumen aggregate ratio scope so meeting fatigue life is 4.24 ~ 4.65%.
Three, cutting optimal is according to the mixing proportion design method analysis of functional requirement
Analyzed from These parameters, meet the bitumen aggregate ratio scope of a certain numerical value of limit flexural-tensile strain; When a certain numerical value of impact toughness is as control criterion, satisfied bitumen aggregate ratio scope; The bitumen aggregate ratio scope meeting fatigue life is.
Example is defined as, as shown in Figure 9 with the asphalt optimum content of AC-25.
The bitumen aggregate ratio scope meeting above-mentioned three index requests is between 4.24 ~ 4.5%, averages 4.37% as asphalt optimum content.
Four, the application note of method of testing:
1, above-mentioned steps " ~ bis-" be experimental technique and experimental design method explanation and test index analysis.
2, " three " is experimental data and experimental index analytic process and method, based on the defining method of the cutting optimal optimum oil-stone ratio of " one, two " analysis result to above-mentioned steps.
3, step " two " in conjunction with local damage of bituminous pavement typical disease, can choose design objective, and then determines bitumen aggregate ratio (or asphalt content) scope.
4, for " determination of cutting optimal optimum oil-stone ratio (or asphalt content) " of a concrete engineering, the temperature condition of test can be determined in conjunction with actual needs, and the weight of evaluation index.Whole process with reference to illustrating, according to: test-analyze-process determined carries out.
Claims (4)
1. flexible pavement cutting optimal match ratio is by a method for designing for topology requirement, it is characterized in that described method step is as follows:
One, impact ductility test is carried out to test specimen, determine that limit flexural-tensile strain is greater than the bitumen aggregate ratio scope of a certain numerical value, and be greater than a certain numerical value as the bitumen aggregate ratio scope met during control criterion using impact toughness;
Two, based on the Fatigue Cracking Test analytical method of semicircle splitting, the bitumen aggregate ratio scope meeting fatigue life is determined;
Three, determine the bitumen aggregate ratio scope meeting above-mentioned three index requests, average as asphalt optimum content.
2. flexible pavement cutting optimal match ratio according to claim 1 is by the method for designing of topology requirement, it is characterized in that described limit flexural-tensile strain is greater than 7000.
3. flexible pavement cutting optimal match ratio according to claim 1 is by the method for designing of topology requirement, it is characterized in that described impact toughness is greater than 0.75N.m.
4. flexible pavement cutting optimal match ratio according to claim 1 is by the method for designing of topology requirement, it is characterized in that described fatigue life is greater than 4000 times.
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| CN1932153A (en) * | 2006-09-28 | 2007-03-21 | 贵州省交通科学研究所 | Asphalt proportion ratio design method |
| JP5126082B2 (en) * | 2009-01-17 | 2013-01-23 | Ｊｆｅスチール株式会社 | How to select materials with roadbed material suitability |
| KR101151832B1 (en) * | 2010-08-17 | 2012-06-01 | 주식회사 한국종합기술 | A reducing noise-drainage pavement for improving permanence and paving method thereof |
| CN102839587A (en) * | 2011-06-20 | 2012-12-26 | 山西省交通科学研究院 | Marshall design method of Evotherm warm-mix asphalt mixture |
| CN102432229A (en) * | 2011-09-05 | 2012-05-02 | 天津市国腾公路咨询监理有限公司 | Asphalt mixture mixed ratio design method based on shearing resistance performance |
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