The method for designing of AC-25 bituminous mixture
Technical field
The invention belongs to Transportation and Civil Engineering applied technical field, be specifically related to a kind of method for designing of AC-25 bituminous mixture.The method adopts vertical vibration method (VVTM) design, can reduce asphalt content, improves the pavement performance of bituminous mixture, and easy and simple to handle, is applicable to large-scale promotion application.
Background technology
The method for designing of current AC-25 bituminous mixture mainly contains marshall's method, GTM method, Hveem method.The apparatus expensive that GTM method adopts is unfavorable for promoting employing; Hveem method design result and the on-the-spot degree of association poor.Current marshall's method is still the main method that most countries carries out Asphalt Mixture Design.
China's AC-25 bituminous mixture generally adopts the Marshall design method in " standard specification for construction and acceptance of highway asphalt pavement " (JTGF40-2004) (hereinafter referred to as JTGF40-2004), and its step is as follows:
(1) according to JTGF40-2004 technical requirements, raw material are selected;
(2) grading limit of AC-25 bituminous mixture meets the requirement of table 1;
Table 1:AC-25 bituminous mixture mineral aggregate gradation scope
Screen size (mm) |
31.5 |
26.5 |
19 |
16 |
13.2 |
9.5 |
4.75 |
2.36 |
1.18 |
0.6 |
0.3 |
0.15 |
0.075 |
Percent of pass (%) |
100 |
90~100 |
75~90 |
65~83 |
57~76 |
45~65 |
24~52 |
16~42 |
12~33 |
8~24 |
5~17 |
4~13 |
3~7 |
(3) with the bitumen aggregate ratio estimated for intermediate value, (to be generally 0.3% ~ 0.5%) at regular intervals equally spaced to both sides expansion, gets more than 5 or 5 different bitumen aggregate ratios and distinguish shaping marshal piece;
(4) density of marshal piece is measured, and the void content of calculation testing piece, pitch saturation ratio, void in mineral aggregate equal-volume parameter; Adopt Marshall tester, survey its Marshall stability and flow valuve;
(5) take bitumen aggregate ratio as abscissa, with the indices of Marshall Test for ordinate, result of the test is clicked and entered in figure, be linked to be round and smooth curve; Get the bitumen aggregate ratio a corresponding to intermediate value of density maxima, stability maximum value, the intermediate value of void rate scope, regulation saturation ratio scope
1, a
2, a
3, a
4, averaged is as OAC
1; The bitumen aggregate ratio scope OAC that AC-25 bituminous mixture Marshall Test technical standard in JTGF40-2004 requires (not containing VMA) is all met with indices
min~ OAC
maxintermediate value is as OAC
2; Get OAC
1with OAC
2average as optimum oil-stone ratio OAC;
(6) make rut plate and marshal piece according to optimum oil-stone ratio OAC, carry out pavement performance inspection according to " highway engineering pitch and Asphalt Mixture Experiment code " (JTGE20-2011) (being called for short JTGE20-2011): comprise wheel tracking test, immersion Marshall test and indirect tensile test on frozen-thaw; Undesirable bituminous mixture, must more conversion materials or re-start mix-design.
Marshall' mechanic characteristic value has following limitation:
(1) molding mode of Marshall design method can not the compaction of accurate simulation wheel road pavement.Do not have inner link between compactive effort and traffic volume size, shaping test piece density cannot reflect the area densities for many years that is open to traffic, and its test specimen physical and mechanical property and actual road surface are not inconsistent;
(2) Marshall design method has been not suitable with Modern Traffic development need.Every technical standard of existing marshall's method designing asphalt mixture is all propose according to the traffic volume of early 1980s, and the traffic of arterial highway there occurs significant change at present, present " large discharge, solid axle carry " feature, every technical standard that obvious marshall's method proposes can not meet the requirement of prevailing traffic road pavement performance.
Summary of the invention
The defect existed for above-mentioned prior art or deficiency, the object of the invention is to, and provides a kind of method for designing of AC-25 bituminous mixture, and the AC-25 performance of asphalt mixture of the method design is good, asphalt content is few and easy and simple to handle.
In order to realize above-mentioned task, the present invention takes following technical solution:
A method for designing for AC-25 bituminous mixture, is characterized in that, the method adopts the design of vertical vibration method, specifically carries out according to following steps:
1) raw material are selected and test
From the material of the actual use of engineering, get representative sample, its technical indicator is tested;
2) design of mineral aggregate gradation
According to engineering gradation design scope and each composition material sieve test data, calculate each composition material usage ratio of the grading limit that meets the requirements;
3) determination of optimum oil-stone ratio
The making of A, vertical vibration test specimen
Bitumen aggregate ratio P is estimated according to engineering experience
a, and to adopt vertical vibration method (VVTM) to make bitumen aggregate ratio be respectively P
a, P
a± (0.3 ~ 0.5), P
a5 groups of test specimens of ± (0.6 ~ 1.0); Specimen molding step is as follows:
(1) be moistened with appropriate butter cotton yarn wiping internal diameter 100mm × height 180mm die trial inside and cushion block, and be placed in 100 DEG C of baking ovens and heat 1h;
(2) mix and stir temperature, compacting temperature according to viscograph determination bituminous mixture, and by JTGE20-2011 regulation by asphalt heating to compound mix temperature;
(3) asphalt mixture density ρ after compacting is estimated according to engineering experience
f, then a test specimen quality is M=ρ
f× π × 5
2× 6.35.To gather materials ratio and test specimen mass M according to each specification, estimate the consumption M that each specification needed for a test specimen is gathered materials
k, (k=1,2,3,4,5), described M
1, M
2, M
3, M
4, M
5and M
6represent the quality of 19 ~ 31.5mm, 9.5 ~ 19mm, 4.75 ~ 9.5mm, 2.36 ~ 4.75mm, Machine-made Sand and breeze respectively;
(4) taking the consumption that a each specification gathers materials is M
k× (1.1 ~ 1.2), (k=1,2,3,4,5), and by even for its mix; The consumption taking a breeze is M
6× (1.1 ~ 1.2); Be placed in baking oven heating 4 ~ 5h that regulation mixes and stirs temperature respectively;
(5) compound taken out from baking oven in step (4) is placed in and is preheated to the bituminous mixture that regulation mixes and stirs temperature and mixes and stirs in pot, and suitably mixes and stirs with scuppit;
(6) from baking oven, take out the pitch heated, take required asphalt quality m
i, the bituminous mixture added in step (5) mixes and stirs in pot, starts to mix and stir pot and mix and stir 90s; Wherein:
I refers to i-th group of bitumen aggregate ratio, i=1,2,3,4,5;
(7) from baking oven, take out the breeze heated, add step (6) Asphalt Mixture and mix and stir in pot, again start and mix and stir pot and mix and stir 90s;
(8) mix and stir pot from bituminous mixture the bituminous mixture taking out and mixed and stirred, and take compound consumption needed for 1 test specimen, put into the metal dish being preheated to 100 DEG C;
(9) take out from baking oven and be preheated to die trial and the cushion block of 100 DEG C, and with inside the cotton yarn wiping die trial being moistened with a little butter, cushion block and vibrating hammer bottom surface.Cushion block to be loaded in die trial and to be encased inside the little circular paper of an oil absorption, requiring bottom cushion block smooth.Then evenly loaded in die trial by bituminous mixture, king bolt cutter used for asphalt mixture peripherally plugs and pounds 15 ~ 20 times, middle 10 ~ 15 times.After plugging and pounding, bituminous mixture surface evening is become convex arc surface;
(10) insert thermometer to the bituminous mixture immediate vicinity installed, measure the compacting temperature whether bituminous mixture temperature meets JTGE20-2011 requirement;
(11) after material to be mixed meets the requirements of compacting temperature, at the round paper that the compound end face pad oil absorption installed is little, then die trial is fixed on vibratory compaction instrument together with cushion block, puts down vibrating hammer and make it contact with bituminous mixture, open vibratory compaction instrument vibratory compaction 60 ± 5s.
Vibratory compaction instrument parameter is configured to: vibration frequency: 37 ± 2Hz, nominal amplitude: 1.4 ± 0.2mm, system weight of getting on the bus: 1.2 ± 0.2kN, system weight of getting off: 1.8 ± 0.2kN;
(12) after vibratory compaction terminates, die trial is taken off from vibratory compaction instrument together with cushion block, take down the circular paper of test specimen end face, measure height of specimen.Test specimen calibrated altitude is 63.5 ± 1.3mm.During as do not met calibrated altitude requirement, test specimen cancels, and 1. adjusts test specimen mixture quality by formula, and again prepares test specimen until highly meet standard-required by step (8) ~ (12);
(13) die trial that shaping test piece is housed is cooled to room temperature together with cushion block, deviates from test specimen, and take down the circular paper of test specimen bottom surface;
(14) repeat step (7) ~ step (13), make 6 test specimens;
(15) the VVTM test specimen of i-th group of bitumen aggregate ratio is made by step (6) ~ step (14).
The test of B, vertical vibration test specimen mechanics index of physics
Test the mechanics index of physics of the vertical vibration test specimen of different bitumen aggregate ratio, comprising: bulk density ρ
f, Marshall stability MS and flow valuve FL, calculate its void content VV, void in mineral aggregate VMA, pitch saturation ratio VFA etc.
The drafting of C, bitumen aggregate ratio and mechanics index of physics graph of a relation
According to test specimen mechanics index of physics test result, take bitumen aggregate ratio as abscissa, with bulk density, void content, saturation ratio, stability, flow valuve for ordinate, result of the test is depicted as the relation curve of bitumen aggregate ratio and indices.
D, determine optimum oil-stone ratio
(1) OAC
1determination
According to the graph of relation of bitumen aggregate ratio and indices, get density maxima, stability maximum value, the intermediate value of void rate scope, the bitumen aggregate ratio corresponding to intermediate value of regulation saturation ratio scope be a
1, a
2, a
3, a
4, as follows 2. averaged as optimum oil-stone ratio initial value OAC
1:
OAC
1=(a
1+a
2+a
3+a
4)/4②
(2) OAC
2determination
According to VVTM designing technique standard (see table 2), all meet the bitumen aggregate ratio scope OAC of vertical vibration method (VVTM) designing technique standard-required in table 2 (not containing VMA) with indices
min~ OAC
maxintermediate value, 3. asks for following formula, as optimum oil-stone ratio initial value OAC
2:
OAC
2=(OAC
min+OAC
max)/2③
Table 2AC-25 bituminous mixture VVTM designing technique standard
Test specimen chi (mm) |
VV(%) |
VFA(%) |
VMA(%) |
MS(kN) |
FL(mm) |
Φ101×h63.5 |
2.5~4.0 |
65~75 |
≥10 |
≥12.5 |
1.5~4 |
(3) determination of optimum oil-stone ratio OAC
Get OAC
1with OAC
2average as the optimum oil-stone ratio OAC of bituminous mixture, see that formula is 4.;
OAC=(OAC
1+OAC
2)/2
④
4) inspection of performance
The above-mentioned match ratio determined is carried out to the inspection of high temperature stability performance, crack resistance at low-temperature and water stabilizing by JTGE20-2011 requirement.
Adopt the Asphalt Mixture Performance of the present invention's design good, and pitch 8% ~ 10% can be saved.
Accompanying drawing explanation
Fig. 1 is bitumen aggregate ratio ~ density relationship curve map;
Fig. 2 is bitumen aggregate ratio ~ Marshall stability graph of relation;
Fig. 3 is bitumen aggregate ratio ~ void content graph of relation;
Fig. 4 is bitumen aggregate ratio ~ pitch saturation ratio graph of relation;
Fig. 5 is bitumen aggregate ratio common range figure.
Below in conjunction with drawings and Examples, the present invention is described in further detail.
Detailed description of the invention
See Fig. 1,2,3,4 and 5, the present embodiment provides a kind of method for designing of AC-25 bituminous mixture, adopts vertical vibration method (VVTM) design, specifically carries out according to following steps:
1, raw material are selected and test
Adopt Karamay, Xinjiang A level 70# pitch, the limestone gravel of Liulin County, Shanxi Province, Machine-made Sand, breeze.Its technological property result of the test is in table 3 ~ table 6.
Table 3: bitumen technology character
Table 4: the technological property of coarse aggregate
Table 5: the technological property of fine aggregate
Apparent density (g/cm
3)
|
Soundness (%) |
Mud content (%) |
Sand equivalent (%) |
Methylene blue number (g/kg) |
Corner angle (s) |
2.720 |
7.0 |
7.2 |
72.0 |
10.1 |
33.0 |
Table 6: breeze technological property
Apparent density (g/cm
3)
|
Water content (%) |
Hydrophilic coefficient |
Add thermostability |
2.687 |
0.5 |
0.83 |
Significant change is not had before and after heating |
After testing, raw material all technical all meets JTGF40-2004 technical requirements.
2, the design of mineral aggregate gradation
Mineral Aggregate grating will ask for an interview to table 7, calculates each composition material usage ratio of the grading limit that meets the requirements in table 8.
Table 7: mineral aggregate gradation area requirement
Screen size (mm) |
31.5 |
26.5 |
19 |
16 |
13.2 |
9.5 |
4.75 |
2.36 |
1.18 |
0.6 |
0.3 |
0.15 |
0.075 |
Percent of pass (%) |
100 |
97.3 |
84.2 |
74 |
66.8 |
55.5 |
76.3 |
29.6 |
23 |
16.8 |
11.2 |
8.6 |
5.1 |
Table 8: the usage ratio that each specification is gathered materials
Aggregate size (mm) |
19~31.5 |
9.5~19 |
4.75~9.5 |
2.36~4.75 |
Machine-made Sand |
Breeze |
Percentage (%) |
8 |
26 |
24 |
12 |
26.5 |
3.5 |
3, the determination of optimum oil-stone ratio
The making of 3.1 test specimens
Bitumen aggregate ratio P is estimated according to engineering experience
a=4.0%, adopt vertical vibration method (VVTM) to make 5 groups of compound test specimens that bitumen aggregate ratio is 3.0%, 3.5%, 4.0%, 4.5% and 5.0% respectively, often organize test specimen 6.Step is as follows:
(1) with inside the cotton yarn wiping die trial being moistened with a little butter and cushion block, and being placed in 100 DEG C of baking ovens, to heat 1h for subsequent use, described die trial internal diameter 100mm × height 180mm, and pad thickness is 40mm, diameter is 150mm;
(2) that determines this bituminous mixture according to viscograph mixes and stirs that temperature is 160 DEG C ~ 175 DEG C, compacting temperature is 140 DEG C ~ 170 DEG C, by JTGE20-2011 regulation by pitch with being heated to 170 DEG C;
(3) asphalt mixture density ρ after compacting is estimated according to engineering experience
f=2.50g/cm
3, then a test specimen quality is M=ρ
f× π × 5
2× 6.35=1246g.To gather materials ratio according to each specification, each specification estimated needed for the test specimen consumption that gathers materials is M
k, (k=1,2,3,4,5,6), described M
1, M
2, M
3, M
4, M
5and M
6represent respectively 19 ~ 31.5mm, 9.5 ~ 19mm, 4.75 ~ 9.5mm, 2.36 ~ 4.75, the quality of Machine-made Sand and breeze;
(4) consumption that gathers materials taking a each specification is 1.1M
k, (k=1,2,3,4,5), in table 9, and mix is even; The consumption taking a breeze is 1.1M
6, in table 9; Be placed in the baking oven heating 4 ~ 5h being greater than and mixing and stirring temperature respectively;
Table 9: each composition material consumption
Aggregate size (mm) |
19~31..5 |
9.5~19 |
4.75~9.5 |
2.36~4.75 |
Machine-made Sand |
Breeze |
Quality (g) |
112 |
364 |
336 |
168 |
371 |
49 |
(5) from baking oven, take out the compound heated in step (4) be placed in and be preheated to 175 DEG C of bituminous mixtures and mix and stir pot, and suitably mix and stir with scuppit;
(6) from baking oven, take out the pitch heated, take required asphalt quality m
1, the bituminous mixture added in step (5) mixes and stirs in pot, starts to mix and stir pot and mix and stir 90s;
I refers to i-th group of bitumen aggregate ratio, i=1,2,3,4,5;
(7) from baking oven, take out the breeze 50g heated, add step (6) Asphalt Mixture and mix and stir in pot, again start and mix and stir pot and mix and stir 90s;
(8) mix and stir pot from bituminous mixture the bituminous mixture taking out and mixed and stirred, and take compound consumption m needed for 1 test specimen
j1(about 1380g), puts into the metal dish being preheated to 100 DEG C;
(9) take out from baking oven and be preheated to die trial and the cushion block of 100 DEG C, and with being moistened with the cotton yarn wiping die trial of a little butter, cushion block and vibrating hammer bottom surface.Then cushion block to be loaded in die trial and to be encased inside the little circular paper of an oil absorption, requiring bottom cushion block smooth.Then evenly loaded in die trial by bituminous mixture, bituminous mixture all peripherally plugs and pounds 15 times, middle 10 times with king bolt cutter.After plugging and pounding, bituminous mixture surface evening is become convex arc surface;
(10) insert thermometer to the bituminous mixture immediate vicinity installed, measure bituminous mixture temperature 145 DEG C, meet the compacting temperature that JTGE20-2011 requires;
(11) at the round paper that the compound end face pad oil absorption installed is little, then die trial is fixed on vibratory compaction instrument together with cushion block, puts down vibrating hammer and make it contact with bituminous mixture, open vibratory compaction instrument vibratory compaction 60s.Vibratory compaction instrument parameter is configured to vibration frequency 37 ± 2Hz, nominal amplitude 1.4 ± 0.2mm, the system weight 1.2 ± 0.2kN that gets on the bus, get off system weight 1.8 ± 0.2kN;
(12) after vibratory compaction terminates, die trial is taken off from vibratory compaction instrument together with cushion block, take down the round scraps of paper of test specimen end face immediately, measure height 65.4mm with slide measure, do not meet the requirement that test specimen calibrated altitude is 63.5 ± 1.3mm; Be m according to the formula bituminous mixture consumption 1. readjusted needed for a test specimen
j2:
By step (8) ~ step (12) shaping test piece, measuring height of specimen is 63.5mm, meets the requirement that test specimen calibrated altitude is 63.5 ± 1.3mm;
(13) die trial that shaping test piece is housed is cooled to room temperature together with cushion block, deviates from test specimen, and take down the circular paper of test specimen bottom surface;
(14) repeat step (7) ~ step (13), make 6 test specimens;
(15) test specimen of i-th group of bitumen aggregate ratio is made by step (6) ~ step (14).
The test of 3.2VVTM test specimen mechanics index of physics
Test the bulk density ρ of the test specimen of different bitumen aggregate ratio
f, Marshall stability MS and flow valuve FL, calculate its void content VV, void in mineral aggregate VMA, pitch saturation ratio VFA, result of the test is in table 10.
Table 10:AC-25 bituminous mixture VVTM test specimen physics-mechanical index
Test specimen group number |
Pa(%) |
ρ
f(g/cm
3)
|
VV(%) |
VMA(%) |
VFA(%) |
MS(%) |
FL(mm) |
1 |
3.0 |
2.458 |
4.3 |
12.8 |
61 |
24.81 |
2.26 |
2 |
3.5 |
2.474 |
3.1 |
11.9 |
68.6 |
28.26 |
2.54 |
3 |
4.0 |
2.487 |
2.3 |
11.7 |
75.9 |
30.83 |
3.17 |
4 |
4.5 |
2.484 |
1.9 |
12.5 |
81.5 |
27.17 |
3.58 |
5 |
5.0 |
2.475 |
1.7 |
13.1 |
84.9 |
21.54 |
3.91 |
Technical indicator |
- |
- |
2.5~4.0 |
≥10 |
65~75 |
≥12.5 |
1.5~4 |
The drafting of 3.3 bitumen aggregate ratios and mechanics index of physics graph of a relation
According to table 10 bituminous mixture VVTM test specimen mechanics index of physics test result, take bitumen aggregate ratio as abscissa, with bulk density, void content, saturation ratio, stability, flow valuve for ordinate, result of the test is depicted as the relation curve of bitumen aggregate ratio and indices, as Fig. 1 ~ Fig. 5.
3.4OAC
1determination
As shown in Figure 1, the bitumen aggregate ratio a that density maxima is corresponding
1=4.12%;
As shown in Figure 2, the bitumen aggregate ratio a that Marshall stability maximum value is corresponding
2=3.98%;
As shown in Figure 3, the bitumen aggregate ratio a that void rate scope intermediate value is corresponding
3=3.42%;
As shown in Figure 4, the bitumen aggregate ratio a that saturation ratio scope intermediate value is corresponding is specified
4=3.63%
Optimum oil-stone ratio initial value OAC
1:
3.5OAC
2determination
As shown in Figure 5, the common range of bitumen aggregate ratio is:
OAC
min=3.26%
OAC
max=3.84%
Optimum oil-stone ratio initial value OAC
2:
OAC
2=(OAC
min+OAC
max)/2=(3.26%+3.84%)/2=3.55%
The determination of 3.6 optimum oil-stone ratio OAC
4. good bitumen aggregate ratio OAC is calculated according to formula
OAC=(OAC
1+OAC
2)/2=(3.79%+3.55%)/2=3.67%
4, the inspection of performance of asphalt mixture
The optimum oil-stone ratio determined by step 3.6 3.67% makes rut plate test specimen and VVTM test specimen, tests that its dynamic stability is 4993 times/mm, residual stability is 91.2%, retained strength ratio is 90.6%, fracture strength is 14.94MPa, equal engineering demands.
Above content is in conjunction with concrete embodiment further description made for the present invention; the invention is not restricted to this embodiment; for general technical staff of the technical field of the invention; without departing from the inventive concept of the premise; some simple deduction or replace can also be made, all should belong to protection scope of the present invention.