CN103174075B - The method for designing of AC-25 bituminous mixture - Google Patents

Abstract

The invention discloses a design method of AC-25 asphalt mixture, which adopts the vertical vibration method to design, including the steps of raw material selection and testing, mineral material gradation design, determination of optimal asphalt ratio and performance inspection, etc. Verification shows that the asphalt mixture designed by this method has good road performance, less asphalt consumption and easy operation, and can save 8% to 10% of asphalt.

Description

Design method of AC-25 asphalt mixture

technical field

The invention belongs to the application technical field of traffic civil engineering, and in particular relates to a design method of AC-25 asphalt mixture. The method adopts the vertical vibration method (VVTM) design, which can reduce the amount of asphalt, improve the road performance of the asphalt mixture, and is easy to operate, suitable for large-scale popularization and application.

Background technique

At present, the design methods of AC-25 asphalt mixture mainly include Marshall method, GTM method and Hveem method. The expensive equipment used by the GTM method is not conducive to popularization; the design results of the Hveem method have poor correlation with the field. At present, the Marshall method is still the main method for asphalt mixture design in most countries.

my country's AC-25 asphalt mixture generally adopts the Marshall design method in "Technical Specifications for Construction of Highway Asphalt Pavement" (JTGF40-2004) (hereinafter referred to as JTGF40-2004), and the steps are as follows:

(1) According to the technical requirements of JTGF40-2004, select raw materials;

(2) The gradation range of AC-25 asphalt mixture meets the requirements of Table 1;

Table 1: Mineral grading range of AC-25 asphalt mixture

Mesh 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 Passing rate(%) 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) Take the estimated oil-stone ratio as the median value, expand to both sides at equal intervals (usually 0.3% to 0.5%), and take 5 or more different oil-stone ratios to form Marshall specimens respectively;

(4) Measure the density of the Marshall test piece, and calculate the volume parameters of the test piece such as porosity, asphalt saturation, and mineral material void ratio; use a Marshall tester to measure its Marshall stability and flow value;

(5) Take the oil-stone ratio as the abscissa, and take the various indicators of the Marshall test as the ordinate, put the test results into the graph, and connect them into a smooth curve; take the maximum density, maximum stability, and specified void ratio range The median value and the median value of the specified saturation range correspond to the asphalt ratio a ₁ , a ₂ , a ₃ , and a ₄ , and the average value is calculated as OAC ₁ ; all indicators are in line with AC-25 asphalt mixture in JTGF40-2004 The median value of the oil-aggregate ratio range OAC _min to OAC _max required by the Marshall test technical standard (excluding VMA) is taken as OAC ₂ ; the average value of OAC ₁ and OAC ₂ is taken as the optimum asphalt-aggregate ratio OAC;

(6) Make rutting plates and Marshall test pieces according to the best asphalt-stone ratio OAC, and conduct road performance inspections in accordance with the "Test Regulations for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011) (JTGE20-2011 for short): including rutting tests, Water immersion Marshall test and freeze-thaw splitting test; asphalt mixture that does not meet the requirements, the material must be replaced or the mix design must be re-designed.

The Marshall design method has the following limitations:

(1) The forming method of the Marshall design method cannot accurately simulate the compaction effect of the wheels on the road surface. There is no internal relationship between compaction work and traffic volume, and the density of the formed test piece cannot reflect the density of the road after it has been opened to traffic for many years, and the physical and mechanical properties of the test piece do not match the actual road surface;

(2) The Marshall design method is no longer suitable for the needs of modern transportation development. The various technical standards for the design of asphalt mixtures by the Marshall method were proposed based on the traffic volume in the early 1980s, but the current traffic conditions of arterial highways have undergone significant changes, showing the characteristics of "large flow and heavy axle load" Obviously, the various technical standards proposed by the Marshall Act can no longer meet the current traffic requirements for road surface performance.

Contents of the invention

In view of the defects or deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a design method of AC-25 asphalt mixture, the AC-25 asphalt mixture designed by the method has good performance, less asphalt consumption and easy operation .

In order to realize above-mentioned task, the present invention takes following technical solution:

A kind of design method of AC-25 asphalt mixture, it is characterized in that, this method adopts vertical vibration method to design, specifically carry out according to the following steps:

1) Raw material selection and testing

Take representative samples from the materials actually used in the project, and test their technical indicators;

2) Design of mineral material gradation

According to the project gradation design scope and the screening test data of each component material, calculate the dosage ratio of each component material that meets the required gradation range;

3) Determination of the best oil-stone ratio

A. Fabrication of vertical vibration test piece

The asphalt-stone ratio P _a is estimated according to engineering experience, and five groups of test pieces with asphalt-stone ratios of P _a , P _a ± (0.3-0.5), and P _a ± (0.6-1.0) are produced respectively by vertical vibration method (VVTM); The forming steps are as follows:

(1) Wipe the inner side of the test mold with an inner diameter of 100mm x height of 180mm and the cushion block with cotton yarn dipped in an appropriate amount of butter, and heat it in an oven at 100°C for 1 hour;

(2) Determine the mixing temperature and compaction temperature of the asphalt mixture according to the viscosity curve, and heat the asphalt to the mixing temperature of the mixture according to the provisions of JTGE20-2011;

(3) According to the estimation of the compacted asphalt mixture density ρ _f based on engineering experience, the mass of a specimen is M=ρ _f ×π×5 ² ×6.35. According to the aggregate ratio of each specification and the mass M of the specimen, estimate the amount of aggregate M _k of each specification required for a specimen, (k=1, 2, 3, 4, 5), and the M ₁ , M ₂ , M ₃ , M ₄ , M ₅ and M ₆ respectively represent the quality of 19~31.5mm, 9.5~19mm, 4.75~9.5mm, 2.36~4.75mm, machine-made sand and mineral powder;

(4) Weigh one portion of aggregates of each specification as M _k × (1.1～1.2), (k=1, 2, 3, 4, 5), and mix them evenly; weigh one portion of mineral powder The dosage is M ₆ ×(1.1~1.2); respectively placed in an oven at the specified mixing temperature and heated for 4~5h;

(5) Take out the mixture in step (4) from the oven, place it in the asphalt mixture mixing pot preheated to the specified mixing temperature, and mix it properly with a spatula;

(6) Take out the heated asphalt from the oven, weigh the required asphalt mass m _i , add the asphalt mixture in step (5) into the mixing pot, and start the mixing pot to stir for 90 seconds; where:

$m_i=(1.1~1.2)\×\underset{k=1}{\overset{6}{\mathrm{\Σ}}}{m}_k[3.0+0.5(i-1)]\%,$ i refers to the oil-stone ratio of the i group, i=1, 2, 3, 4, 5;

(7) Take out the heated mineral powder from the oven, add the asphalt mixture mixing pot in step (6), start the mixing pot again and stir for 90 seconds;

(8) Take out the mixed asphalt mixture from the asphalt mixture mixing pot, weigh the amount of mixture required for one test piece, and put it into a metal pan preheated to 100°C;

(9) Take out the test mold and pads preheated to 100°C from the oven, and wipe the inside of the test mold, the pads and the bottom surface of the vibrating hammer with cotton yarn dipped in a little butter. Put the cushion block into the test mold and place a piece of circular paper with low oil absorption, and the bottom of the cushion block is required to be flat. Then put the asphalt mixture evenly into the test mold, insert and pound the asphalt mixture 15-20 times along the periphery with a large screwdriver, and 10-15 times in the middle. After inserting and tamping, the surface of the asphalt mixture is leveled into a convex arc surface;

(10) Insert a thermometer near the center of the installed asphalt mixture to measure whether the temperature of the asphalt mixture meets the compaction temperature required by JTGE20-2011;

(11) After the mixture reaches the required compaction temperature, place a piece of round paper with low oil absorption on the top surface of the installed mixture, then fix the test mold and pads on the vibratory compactor, and put down the vibratory hammer Make it contact with the asphalt mixture, and turn on the vibratory compactor to vibrate and compact for 60±5s.

The parameters of the vibratory compactor are configured as follows: vibration frequency: 37±2Hz, nominal amplitude: 1.4±0.2mm, weight of the boarding system: 1.2±0.2kN, weight of the boarding system: 1.8±0.2kN;

(12) After the vibration compaction is completed, remove the test mold and pads from the vibration compactor, remove the circular paper on the top surface of the test piece, and measure the height of the test piece. The standard height of the test piece is 63.5±1.3mm. If the standard height requirements are not met, the test piece is invalid, and the quality of the test piece mixture is adjusted according to formula ①, and the test piece is re-prepared according to steps (8) to (12) until the height meets the standard requirements;

(13) Cool the test mold with the formed test piece together with the pad to room temperature, take out the test piece, and remove the circular paper on the bottom of the test piece;

(14) Repeat steps (7) to (13) to make 6 test pieces;

(15) According to step (6) ~ step (14), make the VVTM specimen of the i-th group of oil-stone ratio.

B. Testing of physical and mechanical indicators of vertical vibration specimens

Test the physical and mechanical indicators of vertical vibration specimens with different asphalt ratios, including: bulk density ρ _f , Marshall stability MS and flow value FL, and calculate the void ratio VV, mineral void ratio VMA, asphalt saturation VFA, etc.

C. Drawing of the relationship between oil-stone ratio and physical and mechanical indicators

According to the test results of the physical and mechanical indicators of the specimen, with the asphalt ratio as the abscissa and the bulk density, porosity, saturation, stability, and flow as the ordinate, the test results are drawn as a relationship curve between the asphalt ratio and various indicators .

D. Determine the best oil-stone ratio

(1) Determination of OAC ₁

According to the relationship curve between the asphalt ratio and various indicators, the asphalt ratios corresponding to the maximum density, maximum stability, median value of the specified porosity range, and median value of the specified saturation range are taken as a ₁ , a ₂ , a ₃ , a ₄ , calculate the average value according to the following formula ② as the initial value of the optimal oil-stone ratio OAC ₁ :

OAC ₁ = (a ₁ +a ₂ +a ₃ +a ₄ )/4②

(2) Determination of OAC ₂

According to the VVTM design technical standard (see Table 2), the oil-stone ratio range OAC _min ~ OAC _max median value in which all indicators meet the requirements of the vertical vibration method (VVTM) design technical standard (excluding VMA) in Table 2, use the following formula ③ Obtain, as the initial value of the optimal oil-stone ratio OAC ₂ :

OAC ₂ = (OAC _min +OAC _max )/2③

Table 2 AC-25 Asphalt Mixture VVTM Design Technical Standards

Test piece size (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 the best oil-stone ratio OAC

Take the average value of OAC ₁ and OAC ₂ as the optimal asphalt ratio OAC of asphalt mixture, see formula ④;

OAC=(OAC ₁ +OAC ₂ )/2

④

4) Performance inspection

For the mix ratio determined above, the high temperature stability performance, low temperature crack resistance performance and water stability performance inspection shall be carried out according to the requirements of JTGE20-2011.

The asphalt mixture designed by the invention has good road performance and can save 8% to 10% of asphalt.

Description of drawings

Figure 1 is a graph of the relationship between oil-stone ratio and density;

Figure 2 is a graph showing the relationship between oil-stone ratio and Marshall stability;

Figure 3 is a graph showing the relationship between oil-stone ratio and void ratio;

Figure 4 is a graph showing the relationship between asphalt ratio and asphalt saturation;

Fig. 5 is a public range map of asphalt-stone ratio.

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Detailed ways

Referring to Figures 1, 2, 3, 4 and 5, this example presents a design method for AC-25 asphalt mixture, which adopts the vertical vibration method (VVTM) design, and specifically follows the following steps:

1. Raw material selection and testing

Xinjiang Karamay A grade 70# asphalt, limestone gravel, machine-made sand and slag from Shanxi Liulin are used. The test results of its technical properties are shown in Table 3 to Table 6.

Table 3: Bitumen technical properties

Table 4: Technical Properties of Coarse Aggregate

Table 5: Technical Properties of Fine Aggregate

Apparent density (g/cm ³ ) Robustness (%) Mud content (%) Sand equivalent (%) Methylene blue value (g/kg) Angularity(s) 2.720 7.0 7.2 72.0 10.1 33.0

Table 6: Technical Properties of Mineral Powder

Apparent density (g/cm ³ ) Moisture content (%) Hydrophilic coefficient Heat stability 2.687 0.5 0.83 No significant change before and after heating

After testing, all technical indicators of raw materials meet the technical requirements of JTGF40-2004.

2. Design of mineral material gradation

See Table 7 for mineral mixture gradation requirements, and see Table 8 for the proportion of each component material that meets the required gradation range.

Table 7: Requirements for grading range of mineral materials

Mesh 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 Passing rate(%) 100 97.3 84.2 74 66.8 55.5 76.3 29.6 twenty three 16.8 11.2 8.6 5.1

Table 8: The dosage ratio of aggregates of various specifications

aggregate size (mm) 19～31.5 9.5～19 4.75～9.5 2.36～4.75 Machine-made sand mineral powder percentage(%) 8 26 twenty four 12 26.5 3.5

3. Determination of the best oil-stone ratio

3.1 Preparation of test piece

According to engineering experience, the ratio of asphalt to Pa ₌ 4.0%, and five groups of mixture specimens with asphalt ratio of 3.0%, 3.5%, 4.0%, 4.5% and 5.0% were produced by vertical vibration method (VVTM). 6 pieces. Proceed as follows:

(1) Wipe the inner side of the test mold and the pad with cotton yarn dipped in a little butter, and heat it in an oven at 100°C for 1 hour for later use. The inner diameter of the test mold is 100mm×height 180mm, the thickness of the pad is 40mm, and the diameter is 150mm;

(2) Determine the mixing temperature of the asphalt mixture from 160°C to 175°C and the compaction temperature from 140°C to 170°C according to the viscosity curve, and heat the asphalt to 170°C according to the regulations of JTGE20-2011;

(3) According to engineering experience, the density of asphalt mixture after compaction is estimated to be ρ _f =2.50g/cm ³ , so the mass of a specimen is M=ρ _f ×π×5 ² ×6.35=1246g. According to the proportion of aggregates of each specification, it is estimated that the amount of aggregates of each specification required for a specimen is M _k , (k=1, 2, 3, 4, 5, 6), and the M ₁ , M ₂ , M ₃ , M ₄ , M ₅ and M ₆ respectively represent the quality of 19~31.5mm, 9.5~19mm, 4.75~9.5mm, 2.36~4.75, machine-made sand and mineral powder;

(4) Weigh one portion of aggregates of each specification with an amount of 1.1M _k (k=1, 2, 3, 4, 5), see Table 9, and mix evenly; weigh one portion of mineral powder with an amount of 1.1M ₆ , see Table 9; heat in an oven above the mixing temperature for 4 to 5 hours;

Table 9: Amount of each component material

aggregate size (mm) 19～31..5 9.5～19 4.75～9.5 2.36～4.75 Machine-made sand mineral powder mass (g) 112 364 336 168 371 49

(5) Take out the mixture heated in step (4) from the oven, place it in the asphalt mixture mixing pot preheated to 175°C, and mix it properly with a spatula;

(6) Take out the heated asphalt from the oven, weigh the required asphalt mass m ₁ , add the asphalt mixture in step (5) into the mixing pot, and start the mixing pot to stir for 90 seconds; $m_i=1.1\×\underset{k=1}{\overset{6}{\mathrm{\Σ}}}{m}_k[3.0+0.5(i-1)]\%,$ i refers to the oil-stone ratio of the i group, i=1, 2, 3, 4, 5;

(7) Take out 50g of the heated mineral powder from the oven, add the asphalt mixture mixing pot in step (6), start the stirring pot again and stir for 90s;

(8) Take out the mixed asphalt mixture from the asphalt mixture mixing pot, weigh the amount of mixture m _j1 (about 1380g) required for one test piece, and put it into a metal pan preheated to 100°C;

(9) Take out the test mold and pads preheated to 100°C from the oven, and wipe the bottom surface of the test mold, pads and vibrating hammer with cotton yarn dipped in a little butter. Then put the cushion block into the test mold and place a piece of circular paper with low oil absorption, and the bottom of the cushion block is required to be flat. Then put the asphalt mixture evenly into the test mold, insert and pound the asphalt mixture 15 times along the periphery and 10 times in the middle with a large screwdriver. After inserting and tamping, the surface of the asphalt mixture is leveled into a convex arc surface;

(10) Insert a thermometer near the center of the installed asphalt mixture, and measure the temperature of the asphalt mixture at 145°C, which meets the compaction temperature required by JTGE20-2011;

(11) Place a piece of round paper with low oil absorption on the top surface of the installed mixture, then fix the test mold together with the cushion block on the vibratory compactor, put down the vibratory hammer to make it contact with the asphalt mixture, and turn on the vibratory compactor. The compactor vibrates and compacts for 60s. The parameters of the vibration compactor are configured as vibration frequency 37±2Hz, nominal amplitude 1.4±0.2mm, weight of the boarding system 1.2±0.2kN, and weight of the boarding system 1.8±0.2kN;

(12) After the vibration compaction is completed, remove the test mold and pads from the vibration compactor, immediately remove the round paper on the top surface of the test piece, and use a vernier caliper to measure the height of 65.4mm, which does not meet the standard height of the test piece It is the requirement of 63.5±1.3mm; according to the formula ①, the amount of asphalt mixture required for readjusting a test piece is m _j2 :

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 63.5</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1380</span>}}{\mathrm{<span\; class="notranslate">\; 65.4</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1340</span>}$

Form the test piece according to steps (8) to (12), measure the height of the test piece to be 63.5mm, which meets the requirement of the standard height of the test piece is 63.5±1.3mm;

(13) Cool the test mold with the formed test piece together with the pad to room temperature, take out the test piece, and remove the circular paper on the bottom of the test piece;

(14) Repeat steps (7) to (13) to make 6 test pieces;

(15) According to step (6) ~ step (14), make the test piece of the i-th group of asphalt-stone ratio.

3.2 Testing of physical and mechanical indicators of VVTM specimens

Test the bulk density ρ _f , Marshall stability MS and flow value FL of the specimens with different asphalt ratios, and calculate the void ratio VV, mineral void ratio VMA, and asphalt saturation VFA. The test results are shown in Table 10.

Table 10: Physical-mechanical indicators of AC-25 asphalt mixture VVTM specimens

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 indicators - - 2.5～4.0 ≥10 65～75 ≥12.5 1.5～4

3.3 Drawing of relationship diagram between oil-stone ratio and physical and mechanical indexes

According to the physical and mechanical index test results of the asphalt mixture VVTM specimen in Table 10, with the asphalt ratio as the abscissa and the gross bulk density, void ratio, saturation, stability, and flow as the ordinate, the test results are plotted as the asphalt ratio and The relationship curves of various indicators are shown in Figures 1 to 5.

3.4 Determination of OAC ₁

It can be seen from Figure 1 that the asphalt ratio a ₁ =4.12% corresponds to the maximum density;

It can be seen from Fig. 2 that the oil-stone ratio a ₂ =3.98% corresponding to the maximum value of Marshall's stability;

It can be seen from Figure 3 that the oil-stone ratio a ₃ corresponding to the median value of the specified porosity range = 3.42%;

It can be seen from Figure 4 that the oil-stone ratio a ₄ corresponding to the median value of the specified saturation range = 3.63%

Optimum initial value of oil-stone ratio OAC ₁ :

${\mathrm{<span\; class="notranslate">\; OAC</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4.12</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3.98</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3.42</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; 3</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; 6</span><span\; class="notranslate">\; 3</span><span\; class="notranslate">\; \%</span>}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 3.79</span>}<span\; class="notranslate">\; \%</span>$

3.5 Determination of OAC ₂

It can be seen from Figure 5 that the public range of oil-stone ratio is:

OAC _min =3.26%

_OACmax =3.84%

Optimum initial value of oil-stone ratio OAC ₂ :

OAC ₂ ＝(OAC _min +OAC _max )/2＝(3.26%+3.84%)/2＝3.55%

3.6 Determination of the best oil-stone ratio OAC

According to the formula ④ to calculate the optimal oil-stone ratio OAC

OAC＝(OAC ₁ +OAC ₂ )/2＝(3.79%+3.55%)/2＝3.67%

4. Inspection of asphalt mixture performance

According to the best asphalt ratio determined in step 3.6 of 3.67%, rutting plate specimens and VVTM specimens were made. The dynamic stability was 4993 times/mm, the residual stability was 91.2%, the residual strength ratio was 90.6%, and the failure strength was 14.94. MPa, all meet the engineering requirements.

The above content is a further detailed description of the present invention in conjunction with specific embodiments. The present invention is not limited to this embodiment. For those of ordinary skill in the technical field of the present invention, they can also do Any simple deduction or replacement should belong to the protection scope of the present invention.

Claims (1)

1. 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 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 a little 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 " highway engineering pitch and Asphalt Mixture Experiment code " (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), wherein, 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:

$m_i=(1.1~1.2)\&times;\underset{k=1}{\overset{6}{\mathrm{\&Sigma;}}}{M}_k[3.0+0.5(i-1)]\%,$ 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, bituminous 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, and during as do not met calibrated altitude requirement, test specimen cancels, and 1. adjust test specimen mixture quality by formula, and again prepare 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) test specimen of i-th group of bitumen aggregate ratio is made by step (6) ~ step (14);

The test of B, test specimen mechanics index of physics

Test the mechanics index of physics of the VVTM 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;

The drafting of C, bitumen aggregate ratio and mechanics index of physics graph of a relation

According to the mechanics index of physics test result of test specimen, 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;

The determination of D, 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 vertical vibration method designing technique standard, all meet the technical standards the bitumen aggregate ratio scope OAC of requirement with indices _min~ OAC _maxintermediate value, 3. asks for as follows as optimum oil-stone ratio initial value OAC ₂:

OAC ₂＝(OAC _min+OAC _max)/2③

The vertical vibration designing technique standard of AC-25 bituminous mixture is:

Sample dimensions: Φ 101mm × h63.5mm, VV=2.5% ~ 4.0%, VFA=65% ~ 75%, VMA >=10%, MS >=12.5kN, FL=1.5 ~ 4mm;

(3) determination of optimum oil-stone ratio OAC

Get OAC ₁with OAC ₂average, 4. ask for the optimum oil-stone ratio OAC as bituminous mixture as follows:

OAC＝(OAC ₁+OAC ₂)/2④

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.