ISSAEST, Fairbanks, AK, USA, August 2-5, 2015

L. Huang, A.M. Sha*, F. Ma, Z.Z. Liu and X.L. Zou

Chang’an University, China

August 3, 2015

The national or local standards of the asphalt stabilized

aggregates just provides a simple climate zone and

specifications of construction.

The application and construction in this area are facing with

unprecedented problems .

The applications in cold and high altitude region (Qinghai-Tibet

Plateau) reported can obviously provide a useful experience

to make sure the pavement with high service levels.

The practice could be also very helpful to improve the

national or local standards related with this issue.

This section is from the southern of the Bayan Har Mountains， ended at the north Qinghe.

Location Maduo County Qingshui

River Chengduo

County Yushu County

Average air pressure 605.1 593.7 650.2

Annual mean air temperature(°C) -3.8 -4.8 -1.7 3.2

Annual mean highest air temperature (°C) 3.5 3.3 11.7

Annual mean lowest air temperature (C) -10.3 -11.5 -3.2

Extreme maximum temperature (°C) 22.4 20.4 24.0 28.5

Extreme minimum temperature (°C) -48.1 -42.9 -33.0 -27.6

Long year average precipitation (mm) 321.6 511.1 388 485.9

Daily maximum precipitation (mm) 54.2 64.5 38.8

Long term average evaporation (mm) 1322.5 1127.4 1448 1302.9

Most large snow depth (cm) 16 22 14

Most large freezing depth (m) 2.77 2.52 1.04

Average wind speed (m/s) 3.2 2.9 2.5 1.0

Monthly mean wind speed in winter (m/s) 2.7 2.8 1.0

Most wind speed (m/s) 30.0 24 26

Dominant wind direction NE WNW W

Meteorological data of the main counties nearby the test section

Origin-

destination K629+800~

K630+800 K630+800~ K632+000

K632+000~ K633+200

K633+200~ K634+200

Upper layer AC-13C, 4cm AC-13C, 4cm AC-13C, 4cm AC-13C, 4cm

Lower layer AC-16C, 5cm AC-16C, 5cm AC-16C, 5cm AC-16C, 5cm

Base ATB-25, 12cm ATB-25, 18cm ATB-25, 18cm ATB-25, 18cm

Sub-base

4% cement treated crushed

aggregates, 24cm

2% cement treated crushed

aggregates, 18cm,

graded crushed aggregates, 18cm

geocell reinforced

graded crushed aggregates,

18cm

Cushion graded gravel,

20cm graded gravel,

20cm graded crushed

aggregates, 20cm

graded crushed

aggregates,

20cm

Length/m 1000 1200 1200 1000

Pavement Structure of the test section

Raw materials： Asphalt binder The binder used in this test section is Karamay110# asphalt, whose

technique properties is detailed in Table .

The results of asphalt

Test items unit Test results Specificatio

n Penetration 25°C, 100g, 5s 0.1mm 113.2 T0604-2011

Ductility 15°C, 5cm/min cm ＞100 T0605-2011

Softening point (Ring ball) °C 44.4 T0606-2011

Relative density (15°C) - 0.978 T0603-2011

Viscosity (135°C) Pa·s 0.525 T0625-2011

Viscosity (175°C) Pa·s 0.105 T0625-2011

Raw materials： Aggregate Four types of aggregated (provided by Zhalongqiong Quarries)

with a gradation of 0~3mm, 3~5mm, 5~10mm, 10~30mm were

used in the test sections. .

Test results of aggregate

Test items Test values Requirements Specification

Crushing value (%) 16.0 ≤30 T0316-2005 Needle and plate particle content (particle diameter> 9.5mm) (%) 10.2 ≤20 T0312-2005 Needle and plate particle content (particle diameter<9.5mm) (%) 9.2 ≤20 T0312-2005

Particle, ＜0.6mm Liquid limit (%) 21.5 ＜28 T0118-2007

Plasticity index 5.6 ＜9 T0118-2007

Raw materials： Mineral filler

The mineral filler used in this study was produced in Huashixia, and

the Table shows the main technique properties of the filler.

Test items Unit Test value Specificatio

n

Density g/cm3 2.705 T0352-2000

Moisture content % 0.4 T0332-2005

Hydrophilic coefficient —— 0.77 T0353-2000

Technique properties of the mineral filler

The passing rate of the aggregate used in this study is shown in the

Table . Passing rate of the aggregates

Mineral

aggregate

Passing proportion (%)

37.

5 31.5 26.5 19 16 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15

0.0

75 1#(10-30mm) 100 97.3 82.7 47.6 31.6 16.6 1.6 0.6 0.5 0.5 0.5 0.4 0.2 0.2 2#(5-10mm) 100 100 100 100 100 100 95.2 7.8 1.6 1.1 0.9 0.8 0.7 0.4 3#(3-5mm) 100 100 100 100 100 100 100 88.9 6.5 2.8 1.8 1.5 1.3 0.9 4#(0-3mm) 100 100 100 100 100 100 100 100 77.5 55.9 39.2 27.6 19.8 9.9

Mineral

powder 100 100 100 100 100 100 100 100 100 100 100 100 97.4 78

Raw materials： Aggregate

Raw materials： Asphalt stabilized aggregates

The gradation of the asphalt stabilized aggregates used in this

study is shown in the Table .

Gradation of the asphalt treated crushed aggregate

Gradation type

Passing proportion (%)

37.5 31.5 26.5 19 16 13.2 9.5 4.75 2.36 1.1

8 0.6 0.3 0.15

0.0

75

Upper limitation 100 100 100 80 68 60 50 42 34 28 20 17 12 6

Lower limitation 100 100 90 62 52 42 36 28 22 16 10 7 4 2

Mean value 100 100 95 71 60 51 43 35 28 22 15 12 8 4

Composite

gradation 100 98.5 90.1

70.

1 61 52.5

43.

5 35.3 24

18.

1 13.7 10.6 8.3 5.1

To obtain the best engineering performance of the asphalt stabilized aggregates, the

optimal asphalt content (OAC) was determined by the large scale Marshall test, in

which the cylinder specimens (Φ152.4×95.3mm) were measured.

Results of the large-scale Marshall test

Test items Unit Requirements

construction criterion design criterion Nominal maximum

aggregate size mm 26.5 ≥31.5 ≥26.5

Specimen size mm Φ101.6×63.5 Φ152.4×95.3 Φ152×95.3 Double-sided beat

numbers number 75 112 112

Porosity % 3~6 3~6 4~6 Stability, ≮ KN 7.5 15 18 Flow value mm 1.5~4 measured measured

Asphalt saturation % 55~70 55~70 55~70

Voids in mineral

aggregate, ≮ %

design air voids ATB-40 nominal maximum

aggregate size requirement

4 11 26.5 12.5 5 12 31.5 12 6 13 37.5 11.5

The OAC could be determined based on the data in the Table in

which five asphalt contents were investigated.

Test results of large scale Marshall test

Asphalt-

aggregate

ratio(%)

Theory

relative

density

Integrated

relative

density VV (%) VFA(%) VMA (%) MS (kN)

FL

(0.1mm）

2.5 2.597 2.310 11.0 40.1 18.4 9.71 17.50

3.0 2.576 2.430 5.7 61.2 14.6 11.66 12.30

3.5 2.556 2.443 4.4 69.6 14.6 16.13 6.60

4.0 2.536 2.471 2.6 81.8 14.0 13.43 19.20

4.5 2.517 2.488 1.1 91.8 13.8 11.76 15.50

As a result, the optimal asphalt content (OAC) and corresponding

technical targets are concluded, as shown in the Tables.

Asphalt-

aggregate

ratio (%)

Theory relative

density (g/cm3)

Integrated

relative density

(g/cm3)

VV

(%) VFA

(%) VMA

(%) MS

(kN) FL

(0.1mm)

3.4 2.560 2.452 4.2 70.2 14.2 15.3 6.30

Optimal asphalt content and density

Aggregate mix proportion optimal asphalt content

Mixture

type

Proportion (%) Asphalt-

aggregate ratio

(%) 1# 2# 3# 4# Mineral powder

ATB-25 57 8 6 26 3 3.4

Practice and application

Construction preparation

Mechanical debugging

Mixture mixing

Mixture transportation

Mixture spreading Roller-Compaction.

Acceptance monitoring

♦ main procedures

During the construction of the asphalt stabilized aggregates in the

test section, the machinery allocation is as detailed as Table.

Machinery allocation

Equipment Number Remark

Intermittent mixing Plant 1 possessing production capacity Asphalt paver 3

Bitumen-spraying car 1

Tandem steel wheel vibrator roller (13t) 2

Wheel roller(26t) 2 Dump truck 13 charging about 40t per car

Synchronous surface dressing machine 1

Practice and application

♦ Mixture producing and transportation

►The mixtures (ATB-25 asphalt mixtures) were mixed for 45s.

► Generally, it takes about 30 minutes to produce asphalt stabilized

aggregates to fill a dump truck under a normal condition

► the distance was about 6.3 ~ 10.7 km, which needs about 25 ~ 30

minutes to transport the mixtures.

Heating temperature of asphalt 150°C~155°C

Heating temperature of mineral aggregate 180°C~185°C

Factory temperature of mixture 165°C~170°C

Storage temperature of mixture ≤10°C

Discarded temperature of mixture >185°C

Temperature requirement of asphalt stabilized aggregates

Practice and application

♦ Paving procedure

The field paving equipment is showed below

Tandem steel-wheel

vibrator roller Rubber-wheel

roller

Asphalt paver

Practice and application

♦ Paving procedure The rolling strategy of machines, temperature controlling is

detailed in Tables Rolling strategy of machines and temperature controlling

Rollin

g

proces

s

Type of roller Running

speed(km/h)

Rollin

g

cycles

Rolling

tempera

ture(°C)

Initial

pressur

e

two 13t tandem steel

wheel vibrator roller

(static pressure) 2 to 3 2 ≥150

Repres

s two 26t wheel

roller(vibration) 3 to 5 8 to 9 ≥140

Final

pressur

e

two 13t tandem steel

wheel vibrator roller

(static pressure) 3 to 6 2 to 3 ≥120

Producing and mixing temperature

(°C)

165°C

~170°C

Arriving temperature (°C), ≥ 160

Spreading temperature (°C), ≥ 155

Initial compacting temperature

(°C), ≥ 150

Re-compacting temperature (°C),

≥ 140

Final compacting temperature

(°C), ≥ 120

Final temperature

of the surface

(°C), ≥

Wheel roller 115

Tire roller 105

Requirement of rolling temperature

Field measurements ♦ Compactness The core samples were taken from the field test sections, as shown in Figs. The thickness and compactness of core samples can be found in Table .

Coring samples in the field

Detection results of compactness

Base type Thick

ness Requir

ement Compa

ctness

Requir

ement

K629+800~K630+800(12cmATB）

9.57 ≥11.4 92.64

≥92

K630+800~K632+000(18cmATB)

14.08

≥17.1

91.47

K632+000~K633+200(18cmATB)

15.75 91.47

K633+200~K634+200(18cmATB)

16.76 94.53

Field measurements

♦ Deflection

Detection results of deflection

Base type K629+800~K630

+800 K630+800~K632

+000 K632+000~K633

+200 K633+200~K634

+200

Deflection 39.3 26.9 40.2 55.8

Field measurements ♦Test conclusion and analysis

1) Insufficient and uneven thickness

►The smoothness of sub-base is inadequate.

►the edge of the asphalt stabilized aggregates may be

thin.

►The differences of compaction thickness.

2) Insufficient and uneven compactness

►the segregate during charging, moving, discharging and paving.

►Temperature reducing because the roller did not compact in

time.

►The limitation of roller machines caused the rolling speed could

not keep up with the paving speed.

Existing problems

► Temperature caused segregation

►Gradation caused segregation

Un-compacted core sample Surface segregations after compaction

Strategies

The low temperature, great temperature difference, severe freeze-

thaw cycles and short construction period in cold and high altitude

regions affect the construction of asphalt stabilized aggregates.

This case study provides a reasonable guidance for asphalt stabilized

aggregates in cold and high altitude regions.

It suggests that the asphalt stabilized aggregates should obtain

suitable compositions and structures based on the material

optimization and optimal mixture design. Besides, effective and

efficient temperature control, construction technology and organizing

manage could guarantee the engineering performance of mixtures.

Feng Ma PH D, Associate Professor Vice Chair of Highway Engineering Department, Highway School, Chang'an University, China (+86)15829939683 E-mail,mafeng@chd.edu.cn