Journal of Wuhan University of Technology-Mater. Sci. Ed. Oct.2010 871

DOI 10.1007/s11595-010-0111-2

Design Method and Performance for Large Stone

Porous Asphalt Mixtures

ZHAO Yongli, HUANG Xiaoming*

(School of Transportation, Southeast University, Nanjing 210096, China)

Abstract: Design method for large stone porous asphalt mixtures (LSPM) was analyzed to

avoid the early distresses of semi-rigid asphalt pavements. Based on stone-to-stone skeleton structure

concept, processes of LSPM gradation design was given. The gradation composite design for LSPM

shows that the LSPM nominal maximum size （ ）NMS should be larger than 26.5 mm, and the NMS

sieve passing percentage should be greater than 50%. Through experiments and calculations on the

volume properties of the aggregate, the range of aggregate gradation curve of LSPM was given. In

terms of asphalt binder’s normalized test results, MAC-70 and SBS modified asphalt were selected as

the asphalt binders. The applicability of large scale Marshall Method and gyratory compaction method

to shape specimens was investigated. Based on the asphalt mixture performance evaluation, the op-

timum asphalt content range (3.1%-3.6%), the bitumen film’s thickness range (13-16 µm) and the air

void range ％(13 - ％18 )were recommended. Finally, LSPM was tested by the laboratory performance

tests including rutting resistance test, fatigue test and water stability test. The theoretic and practical

analysis shows that LSPM has a good performance on water permeability, rutting resistance and re-

flection crack resistance.

Key words: large stone porous asphalt mixtures (LSPM); mixture design; performance; ag-

gregate gradation; optimum asphalt content

1 Introduction

Premature rutting of heavy duty asphalt pavements

has been increasingly experienced in recent years, pri-

marily due to high pressure truck tires and increased

wheel loads. The increased stress on asphalt pavement

with semi-rigid base always leads to large area dis-

tresses，such as cracks and water-damage. Although

various measures were adopted to prevent the pavement

from those early distresses, this problem has not been

solved thoroughly[1]

.

Numerous researches on asphalt mixtures design

methods and shaping of test specimens (such as Super-

paveTM, GTM) still can not meet the cracking resistance

and waterproof requirements[2, 3]

. The large stone asphalt

mixtures mainly including coarse-graded asphalt con-

crete (AC), asphalt treated base (ATB) and asphalt treated

porous base (ATPB) can ultimately overcome these diffi-

culties by rational composite design[4]

.

2 Gradation Composite Design

Large stone porous asphalt mixtures belong to

“Single-diameter particles skeleton structure with con-

nected pore”. The gradation composite design consists of

two processes: the first process is to determine the pro-

portion of coarse aggregates through the experiment and

calculation on the volume conditions of the aggregate;

the second is to determine amount of the fine aggregates

and bitumen in terms of the air void ratio and the ratio of

mineral powder.

2.1 Control parameter of aggregate

gradation

CA ratio is put forward to control the segregation

and compacting stability of asphalt mixture. Given the

fine aggregates do not contribute to the stone-stone in-

terlock in asphalt mixture, CA ratio does not restrict the

fine aggregate. And the CA ratio formula is given as

follows:

(1)

Where: P(NMPS/2) is the passing percentage of the aggre-

gates whose size was half of nominal maximum particle

size (NMPS); P(PCS) is the passing percentage of critical

ratio (NMPS/2) (PCS) (100%) (NMPS/2)) / ( )CA P P P P− −＝(

©Wuhan University of Technology and Springer-Verlag Berlin Heidelberg 2010

(Received: July 23, 2009; Accepted: June 19, 2010)

ZHAO Yongl 赵赵赵i ( ): Assoc. Prof.; Ph D; E-mail: yl.zhao@seu.edu. cn.

*Corresponding author: HUANG Xiaom 黄黄黄ing ( ): Prof.; Ph D;

E-mail: huangxm@seu.edu.cn

Vol.25 No.5 ZHAO Yongli et al: Design Method and Performance… 872

aggregates size distinguishing the coarse aggregate from

the fine aggregate. (PCS, the critical aggregates size, is

0.22 times of the nominal maximum aggregate size

(NMAS). PCS is the critical point of skeleton formation,

and P(PCS) will directly affect the formation of the skele-

ton structure. So the determination of PCS point is a key

step of aggregate gradation composite design. The CA

ratio also affects the voids in mineral aggregates (VMA)

and the segregation of asphalt mixtures. It can control the

stability and quality of the construction. The CA ratio of

LSPM ranges from 0.5 to 0.8 (Table 1), and the recom-

mended gradations for LSPM are given in Table 2, the

aggregate gradation curves of LSPM-25 and AC-25 are

given in Fig.1.

2.2 Condition verification for aggregate

gradation After gradation design, the skeleton condition veri-

fication of aggregate gradation is needed to inspect

whether the coarse aggregates have formed

stone-to-stone skeleton structure. There are two pa-

rameters for the condition verification, one is the void in

the coarse aggregate (VCA) to determine the actual con-

dition of the gradation. Determine VCA mix of the as-

phalt mixture specimen and VCADRC of the coarse

aggregate in the standard compaction level. VCA mix ＜

VCADRC is the precondition of the skeleton structure

formation; the other parameter is stone-to-stone contact

degree (SSC) used to estimate the contact condition be-

tween large stones. When SSC＞90%, it is believed that

the coarse aggregate in asphalt mixture can form skeleton

structure.

2.3 Processes of LSPM gradation design The procedure and experimental process of large

stone porous asphalt mixture are described as follows:

Based on the determined thickness of pavement, the

NMAS of asphalt mixture is chosen and then the PCS

which distinguishes the coarse aggregate from fine ag-

gregate is calculated. Then measure the physical proper-

ties of aggregate such as apparent density, bulk density

and water absorption rate. The appropriate skeleton

structure was determined in view of the traffic volume,

the compaction condition and the climate. According to

common conditions, the bigger volume of traffic are

presented, the larger VCA and tighter skeleton structure

are needed. The loose density, compaction density and

vibrating compaction density were measured. The loose

density is defined as the weight of the aggregate per unit

volume when the aggregate in the bucket is placed in a

standard loose condition; the compaction density is de-

fined as the weight of the aggregate per unit volume when

the aggregate in the bucket is compacted to a standard

compaction level; the vibrating compaction density is

defined as the weight of the aggregate per unit volume

when aggregate in the bucket is vibrating compacted to a

standard compaction level. All density calculation proc-

ess should consider the cross–over and interference con-

ditions among the coarse and fine aggregates.

All kinds of coarse and fine aggregates’ initial den-

sity were input to the calculating program. LSPM be-

longs to skeleton-gap structure, and the fine aggregates

should not interfere with the skeleton structure formed by

coarse aggregate, so the initial density of coarse aggre-

gates is approximate to its vibrating compaction density

or even bigger than it. And the initial density of fine

aggregate is approximate to its loose density. It is nec-

essary to determine an initial weight proportion of coarse

aggregate to fine aggregate. An initial rate of NMAS in

the calculating program is 90% or 95%. The size pro-

portion of particles forming skeleton structure ranges

from 0.25 to 0.28.

The chosen density was adjusted on the basis of the

initial grading curve. In addition, input technical speci-

fications for asphalt mixture, such as the proportion of

mineral powder to bitumen and air void. CA ratio gained

from the adjusted gradation was verified. If the CA ratio

does not satisfy the requirements, the proportion of

coarse aggregates to fine aggregates should be adjusted to

meet the design requirements. At the same time, the air

void also should meet those requirements.

Since fillers are not commonly applied in LSPM

mixtures, 1% raw lime powder and anti-stripping agent

can be added to the mixtures to enhance the water stabil-

ity of asphalt mixtures. The grading proportion calcu-

Table 1 Requirements of CA ratio for coarse aggregate

Control parameter of

aggregate gradation

Extension re-

quirements

Dense-graded asphalt

mixture

CA ratio 0.5-0.8 0.4-0.8

Table 2 Recommended aggregate gradation for LSPM

Size of sieve/mm 52 37.5 31.5 26.5 19 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075

LSPM-25 100 100 100 70-98 50-85 32-62 20-45 6-29 6-18 3-15 2-10 1-7 1-6 1-4

LSPM-30 100 100 90-100 70-95 40-76 28-58 19-39 6-29 6-18 3-15 2-10 1-7 1-6 1-4

LSPM-35 100 75-98 67-96 50-80 25-60 15-40 10-35 6-25 6-18 3-15 2-10 1-7 1-6 1-4

Fig.1 Typical gradation curves for LSPM

Journal of Wuhan University of Technology-Mater. Sci. Ed. Oct.2010 873

Table 3 Indices of three kinds of asphalt binder

Test item unit AH-70 SBS MAC

Penetration

(25 ℃, 100 g, 5 s)0.1 mm 67 61 53

Ductility

(5 cm/min,5 ℃) cm 4 35 5

Softening point

(TR&B)(minimum) ℃ 48.5 64 84

Quality loss (maxi-

mum) % －0.070 －0.090 －0.093

Penetration in-

dex(PI) 25 ℃，

(minimum)

% 77.6 82 79.2

PG grade — PG 64-22 PG 76-28 PG 76-22

lated by computer program is always decimal value and

needs to be converted into integer, and the sum of the

grading proportion should be equal to 100%. Another

two grading curves on the basis of different requirements

need to be computed by the described procedure. These

two grading curves would be used as contrastive curves

in next process. A rational gradation curve can be de-

termined by adopting Marshall design method. On the

basis of calculated volumetric parameters including air

void and VMA, the ranges of volumetric properties used

for Marshall design and the ranges for gradation control

can be adjusted. Meanwhile, skeleton structure condition

need to be examined to make sure the gradation of LSPM

does form a skeleton structure.

3 Determination

Because NMAS of LSPM is larger than 26.5 mm,

traditional Marshall’s specimen shaping method can not

meet the requirement for relationship between the parti-

cles’ size and diameter of cylinder; meanwhile, the

volumetric parameters can not be determined by tradi-

tional Marshall method, because the optimum range of

LSPM air void is from 13% to 18%. By researching the

composite design of LSPM, the choosing criteria for

binder material and measuring method of volumetric

parameters were put forward, and some new methods

were proposed to determine the asphalt content consid-

ering rational bitumen film thickness, air void, segrega-

tion and scattering of asphalt mixtures.

3.1 Determination of initial asphalt con-tent The chief factor influencing the specific surface area

of aggregate is the total percentage of mineral powder

passing through 0.075 mm sieve, and the secondary

factor is the percentage of aggregate passing through 0.15

mm, 0.3 mm, 0.6 mm, 1.18 mm, 2.36 mm and 4.75 mm

sieves. Numerous researches indicated that the aggregate

with particle size larger than 4.75 mm do not signifi-

cantly affect the specific surface area of aggregate. The

estimation for aggregate specific surface area is given as

Formula 2:

Area＝0.41＋0.41a＋0.82b＋1.64c＋2.87d＋

6.14e＋12.29f＋32.77g(m2/kg) (2)

Where: Area is the aggregate specific surface area ,

and a, b, c, d, e, f, and g mean the passing percentage of

4.75 mm, 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, 0.15

mm and 0.075 mm sieves respectively.

Estimated Asphalt Content

＝Assumed Bitumen Film Thickness×Aggregate

Specific Surface Area (3)

Bitumen film thickness is asphalt content adhered to

aggregate each specific surface unit area. Commonly, if

bitumen film is too thin to cover the aggregate particles,

the performance of asphalt mixture such as the water

stability and fatigue performance would decline evi-

dently. However, if bitumen film is too thick, it would

hasten relative slippage between aggregate particles.

Traditionally, the bitumen film thickness of porous as-

phalt mixture ranges from 12 μm to 14 μm, while

6 μm to 8 μm for dense-graded asphalt mixtures. So

the bitumen film thickness of LSPM should meet the

requirement of performance balance.

3.2 Selection for Asphalt Binders LSPM should provide not only good drainage per-

formance but also good high temperature performance and

fatigue resistance. For these reasons, AH-70# asphalt binder,

SBS modified asphalt binder and MAC-70# modified as-

phalt binder were tested to choose an appropriate asphalt

binder for LSPM and test results are shown in Table 3.

On the basis of SHRP performance grading meas-

urement, the PG grades of MAC-70# modified asphalt

and SBS modified asphalt binder are higher than con-

ventional asphalt binder, and the high pavement tem-

perature for both of the two modified asphalt binders are

76 ℃. While the softening point of MAC-70 asphalt

binder is 84 . ℃ In order to determine the appropriate

bitumen film thickness for LSPM mixture, the thickness

of LSPM should be big, but not too big to drain, and the

drainage test results for all three asphalt binders are il-

lustrated in Fig.2 According to the typical gradation

curve provided in Fig.2 and requirements for minimum

bitumen film thickness, the recommended minimum

asphalt content should range from 2.8% to 2.9%, and the

discrete loss should be less than 0.2% (while requirement

of the discrete loss of SMA is less than 0.1%). Conclu-

sion can be drawn that the discrete loss of AH-70# has

exceeded the recommended range and MAC-70 modified

asphalt binder and SBS modified asphalt binder could

meet these two requirements, thus, modified asphalt

binders should be adopted for LSPM.

3.3 Selection for specimens’ shaping method

Because the maximum aggregate size of LSPM is

Fig.2 Drainage test results of three kinds of asphalt binder

Vol.25 No.5 ZHAO Yongli et al: Design Method and Performance… 874

Table 7 Differences of air void and density between two speci-

men shaping methods

Asphalt

content

/%

Marshall

density

/(g/cm3)

SGC

den-

sity

/(g/cm3)

The

maximum

specific

density

/(g/cm3)

Marshall

air

void/%

SGC

air

void

/%

3.0 2.182 2.209 2.615 16.6 15.5

3.5 2.195 2.233 2.594 15.3 13.9

4.0 2.204 2.240 2.574 14.4 13.0

Table 5 Large scale marshall method test results

Beat numbers Bulk density/(g/cm3) Air void/％

75 2.078 19.9

97 2.141 17.5

112 2.198 15.3

127 2.195 15.4

Table 4 Compaction parameters for large scale Marshall

and conventional Marshall

Parameters Conventional Mar-

shall Large scale Marshall

Specimen diameter

/mm 101.6 152.4

Standard specimen

height/mm 63.5 95.25

Hammer weight/kg 4.53 10.2

Hammer dropping

height/mm 457 457

Beat number 75 112

Unit surface work

per beat/(N.m/mm2) 0.0025037 0.0025055

larger than 26.5 mm, conventional Marshall cylinder

with 101.6 mm diameter can not meet the requirement for

relationship between the particles’ size and cylinder di-

ameter. New specimen shaping method for LSPM was

proposed by contrasting large scale Marshall Compaction

method and the gyratory compaction method. The com-

paction parameters for large scale Marshall Compaction

method and conventional Marshall Compaction method

are shown in Table 4.

Both the large scale Marshall Method and gyratory

compaction method with different beat numbers were

adopted to make comparison, and test results are provided

in Table 5 and Table 6. The CoreLok density tester was

used to determine the density and air void of the com-

pacted specimens, and test results are given in Table 7.

The asphalt mixture have reached the optimum

dense state when beat number equals to 112, as shown in

Table 5, and the added beat above 112 will cause exterior

perturbance resulting in crack of aggregates. So, the beat

of 112 is recommended as the standard beat number for

large scale Marshall’s specimen shaping method.

The data from Table 6 indicates that air void

gradually decreases with the increase of beat number, but

the decreased range of air void reduces as the asphalt

mixtures have been in condition of compaction. Ac-

cording to the requirement for heavy traffic in Super pave

criteria, the beat number of 100 is recommended as de-

sign beat number.

Table 7 shows that the two shaping methods are both

rational according to the measured air void and density.

So the selection for specimen preparing should base on

equipments conditions of construction enterprises.

3.4 Binder drainage test and canter test The drainage test and the canter test are two abso-

lutely necessary tests to determine optimum asphalt

content for porous asphalt mixtures. The drainage test

determines the maximum asphalt content which does not

drift for a large scale. The canter test determines the

minimum asphalt content to make sure the asphalt mix-

ture does not scatter. As the test results provided in Table

8, the maximum permissible drainage loss value is 0.2%,

the corresponding maximum asphalt content is 3.6%; the

maximum permissible scatter loss value is 25%, and the

corresponding maximum asphalt content is 2.9%. So the

appropriate asphalt content ranges from 2.9% to 3.6%

according to the drainage tests and canter tests. Tests

results also indicate that MAC modified asphalt binder is

the appropriate for LSPM to promote the water stability.

3.5 Determination for optimum bitumen film thickness and asphalt content

As the existence of free water in LSPM during rainy

season, there should be adequate bitumen film thickness

for this new asphalt mixture. Meanwhile, a rational

thickness of bitumen film and viscosity of asphalt binder

can ensure good durability of LSPM to meet the re-

quirements of water stability.

The appropriate asphalt content ranges from 2.9% to

3.6% according to results of the drainage tests and canter

tests, and according to large scale Marshall Design

method, the appropriate asphalt content is 3.1%. So the

optimum asphalt content is from 3.1% to 3.6%, and the

optimum thickness of bitumen film ranges from 13 μ

m-16 μm.

4 Balanced Performance De-sign for LSPM

Since asphalt binder types and rational bitumen film

thickness range are determined, a number of performance

tests are adopted to determine asphalt content, such as

Table 8 Results of binder drainage tests and canter tests

Asphalt

content/%

Distress

loss/%

Scatter

loss/%

Bitumen film

thickness/μm

3.0 0.073 23.88 14.1

3.5 0.136 19.26 16.5

4.0 0.441 16.62 18.8

Table 6 Gyratory compaction method test results

Beat numbers Bulk density/(g/cm3) Air void/％

20 2.043 21.2

50 2.101 19.0

75 2.152 17.3

100 2.163 16.6

Journal of Wuhan University of Technology-Mater. Sci. Ed. Oct.2010 875

permeability test, dynamic stability test, fatigue test and

other design parameter tests.

4.1 High temperature performance of LSPM

The results of dynamic stability test with different

gradations, asphalt contents and plate depths are shown in

Fig.3 and Fig.4 Results indicate that the skeleton struc-

ture can not be formed by coarse aggregate without a

stone-stone contact and transverse distortion may be

brought out when the depth of plate is less than 4 cm

under the action of wheel load. Further research shows

that the dynamic stability test with plate depth of COM is

more suitable to represent the high temperature per-

formance of LSPM. Thus, the plate depth recommended

should be 2.5-3 times of the NMAS.

The high temperature performance of LSPM is en-

hanced greatly to meet the requirement for heavy traffic

by optimum gradation and appropriate modified asphalt

binder. The rutting resistance of LSPM is 5 to 7 times of

the conventional asphalt concrete, and the rutting depth

of LSPM is only 70% of that of conventional asphalt

concrete. So the rutting resistance of LSPM is much

better than those asphalt mixtures deigned by super pave.

The test results also indicate that the dynamic sta-

bility decreases with the increase of asphalt binder con-

tent. Therefore, content of asphalt binder can be in-

creased properly to meet the requirements for fatigue

properties and water stability of LSPM.

Hamburg wheel tracking device was introduced to

estimate the high temperature performance of LSPM. A

steel wheel with certain weight and shape rolls plate of

asphalt mixture for 20 000 times in water bath of 45 ℃

or 50 ℃. Then, the wheel track depth and deformation

curve are measured to judge the water stability and rut-

ting resistance of the mixture. Hamburg wheel tracking

test is the most severe experiment to evaluate the water

sensibility and high temperature performance of asphalt

mixture. The test result is consistent with the filed per-

formance of compacted asphalt mixture.

Contrastive tests were conducted for LSPM with

MAC modified asphalt binder, OGFC and SMA with

SBS modified asphalt binder and fiber stabilizer, and

AC-25 with 70# asphalt binder. The test results show that

the deformation rate of LSPM reduces gradually (Fig.5),

a large proportion of deformation appeared in forepart of

test, and the deformation of 4 000 times under rolling

load is half of the total deformation. But the deformation

curve of AC-25 develops approaching to linear. So the

“Single-diameter particles skeleton structure with con-

nected pores” including LSPM can provide much better

high temperature performance and reach the require-

ments of rutting resistance.

4.2 Fatigue performance of LSPM During asphalt pavement service life, when the

stress in pavement structure exceeds the structural fatigue

resistance strength under a certain times of load action,

the pavement will crack from bottom to pavement surface

layer, and finally to the top of the pavement surface.

A shorter duration and inexpensive laboratory fa-

tigue test was adopted to evaluate the fatigue properties

of LSPM. The tester is TUMS made by Australia. The

rolling compacted specimens are cut into small beams

with 63.5 mm height, 50 mm width and 381 mm length,

the distance between two fulcrum positions is 355.5 mm.

The loading mode is three-dividing point loading with

strain control, and the distance between two dividing

points is 118.5 mm. The loading wave and frequency is

10Hz continuous haversine wave load, the test content is

given in Table 9, the result was given in Fig.6.

The test results shown in Fig.6 indicate that the

flexural fatigue curves of the five kinds of asphalt mix-

tures are approximately parallel. According to fatigue

Fig.4 COM plate depth dynamic stability test with different gradation

Fig.5 LSPM deformation curve in Hamburg wheel tracking test

Table 9 Contents of fatigue tests

GradationAsphalt

type

Asphalt

Con-

tent/%

Strain level

(με) Remark

AC－20 70＃ 4.4 200，400, 600

ATB－25 70＃ 3.4 200, 400, 600

ATB－30

70＃

2.8 200, 400, 600

3.4 200, 400, 600 0 ℃, 15 ℃, 25 ℃

4.0 200, 400, 600

MAC 3.4 200, 400, 600

LSPM－25 MAC 4.4 200, 400, 600

ATPB Not capable for fatigue test

Fig.3 Dynamic stability of LSPM with different thickness of slab

Vol.25 No.5 ZHAO Yongli et al: Design Method and Performance… 876

formula: ( ) nf tN K ε=, the variety ranges from －3.2

to －4.0 of n value is quite small, and it consists with the

research result abroad as the n value in AI design method

equals to －3.291, and －4.0 in shell design method. So

the fatigue criteria for LSPM with MAC modified asphalt

binder is established upon research described above:

The K value shows the position of the fatigue curve,

so it can represent the advantages and disadvantages of

the fatigue properties in an intuitive way. The rank of

these five asphalt mixture fatigue properties from the best

to the worst is: AC20→ATB25→ATB30→LSPM25→

LSPM30. Further more, it can be concluded from the

discussion that the MAC modified asphalt binder and the

appropriate bitumen film thickness can ensure the good

integrity and pavement fatigue performance for LSPM.

4.3 Permeability of LSPM

Non-lateral confined permeability tester was used to

evaluate the permeability of compacted LSPM, and the

connection between air voids and permeability coeffi-

cients is presented in Fig.7. As shown, permeability co-

efficients increase sharply as the air voids increase from

13% to 17%, but when the air voids are bigger than 18%,

the permeability coefficients trend to level off. The air

void can meet the need for free drainage when it is bigger

than 13%, and the corresponding permeability coefficient

is 0.01 cm/s. The permeability coefficients of different

asphalt mixtures are shown in Table 10. It can be con-

cluded that permeability does not only depend on air void

but on the connected pores. So the optimum range for air

void of LSPM is from 13% to 18%.

4.4 Criteria for LSPM designed by large

scale marshall design method

Based on the balanced requirement for high tem-

perature performance, fatigue properties and water per-

meability of asphalt mixtures, the criteria for LSPM de-

signed by large scale Marshall Design method is given in

Table 11.

5 Conclusions

The LSPM composite design method was proposed

on the basis of balanced comparison of high temperature

performance, fatigue properties and water permeability,

and the conclusions are shown as follows:

a) The aggregate gradation range for LSPM was

determined. The nominal maximum size of LSPM should

be larger than 26.5 mm and the passing percentage of the

maximum size sieve should be greater than 50%.

b) Polymer modified asphalt binder such as MAC is

recommended for LSPM.

c) Both the large scale Marshall method and gyratory

compaction method can be used for LSPM specimen shaping.

d) Through a number of performance examinations,

the recommendation range of air void is ％13 - ％18 , the

range of optimum asphalt binder content is ％3.1 -3.6%, and

optimum thickness of bitumen film is 13 μm-16 μm.

References [1] N Paul Khosla, Glen A Malpass. Use of Large Stone Asphalt

Concrete Overlays of Flexible Pavements[R]. Research

Project No.23241-94-7

[2] Asphalt Institute. Asphalt Overlays for Highway and Street

Rehabilitation[M]. KY: Asphalt Institute, 1983

[3] Prithvi S Kandal. Large Stone Asphalt Mixes: Design and

Construction[C]. Annual Meeting of the Association of As-

phalt Paving Technologists, Albuquerque, 1990

[4] Texas Transportation Institute. Design and Evaluation of

Large Stone Asphalt Mixes[R]. NCHRP REPORT 386, 1990

[5] Prithvi S, Kandal. Design Stone Asphalt Mixes to Minimize

Rutting[C]. National Center For Asphalt Technology, 1990

Table 10 Osmotic coefficients to different mixture

Type of

mixture LSPM OGFC AC-25 AC-20 AK-13

Air void 17.3 22 10.2 8.45 9.5

Osmotic coeffi-

cient

/(cm/s)

0.130 0.079 8.6×10－5 3.7×10

－53.3×10－5

6 0.027 0.006 3.6

1.2 10 ( )VFA E

tN e ε

− − −

= ×

Table 11 LSPM large Marshall Design criteria

Test index LSPM

NMAS/mm Equal or bigger than 26

Specimen diameter/mm φ152×95

Beat numbers(both sides)/times 112

Air void VV/% 13-18

Bitumen film thickness/µm 13-16

Distress loss/% No bigger than 0.2

Scatter loss/% No bigger than 20

Asphalt binder content/% 3.1-3.6

Fig.6 LSPM fatigue curve with different gradations

Fig.7 Connection between air void and osmotic coefficients