Journal ofTesting and Evaluation

Amir Hossein Sheikhmotevali1 and Mahmoud Ameri2

DOI: 10.1520/JTE20130306

Ranking of EVA ModifiedBitumens Based on AASHTOM320 Performance RelatedParameters

VOL. 44 NO. 4 / JULY 2016

Amir Hossein Sheikhmotevali1 and Mahmoud Ameri2

Ranking of EVA Modified BitumensBased on AASHTO M320 PerformanceRelated Parameters

Reference

Sheikhmotevali, Amir Hossein and Ameri, Mahmoud, “Ranking of EVA Modified Bitumens

Based on AASHTO M320 Performance Related Parameters,” Journal of Testing and Evaluation, Vol. 44,

No. 4, 2016, pp. 1–10, doi:10.1520/JTE20130306. ISSN 0090-3973

ABSTRACT

The AASHTO M320-10 bitumen specifications, and the measurements upon which they are

based, are designed to provide performance-related properties that can be related in a

rational manner to pavement performance. Some reports suggest that the AASHTO M320

specifications are well-suited for dealing with unmodified bitumens. However, a number of

studies question the validity of the AASHTO M320 specifications for modified systems. This

paper investigates the use and suitability of AASHTO M320 bitumen parameters for ranking

of plastomeric polymer modified bitumens. Two methods were used for the ranking of a

series of ethylene vinyl acetate (EVA) polymer modified bitumens (PMBs) in terms of the

three main distress modes associated with flexible pavements of low temperature cracking,

permanent deformation (rutting), and fatigue damage. AASHTO M320 bitumen parameters,

practical mechanical asphalt mixture properties were used for ranking of EVA PMBs then the

rankings were compared. Results show that AASHTO M320 bitumen parameters are valid for

EVA PMBs only at low polymer contents. It is an important conclusion because the high cost

of polymers makes the commercial use of modified bitumens only attractive for road

construction if the amount of polymer is relatively small.

Keywords

ethylene vinyl acetate, AASHTO M320, fatigue, rutting, low temperature cracking

Introduction

Fundamental, performance-based tests are not always easy to implement for acceptance. Many

agencies have found surrogate “performance-related” tests to be more convenient. Performance-

Manuscript received November 30, 2013;

accepted for publication December 15,

2014; published online January 27, 2015.

1 School of Civil Engineering, Iran Univ. of

Science and Technology, Narmak, Tehran

16846, Iran (Corresponding author),

e-mail: sheikhmotevalli@civileng.iust.ac.ir

2 Head of Center of Excellence for PMS,

Transportation and Safety, School of

Civil Engineering, Iran Univ. of Science

and Technology, Narmak, Tehran 16846,

Iran, e-mail: ameri@iust.ac.ir

Copyright VC 2015 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 1

Journal of Testing and Evaluation

doi:10.1520/JTE20130306 Vol. 44 No. 4 / July 0000 / available online at www.astm.org

related tests and specifications closely simulate field conditions.

While not giving absolute answers, these performance-related

tests can be very effective at ranking materials and predicting

field failures. The AASHTO M320-10 [1] bitumen specifica-

tions, and the measurements upon which they are based, are

designed to provide performance-related properties that can be

related in a rational manner to pavement performance. Some

reports in the literature suggest that the AASHTO M320 specifi-

cations are well-suited for dealing with unmodified bitumens.

However, a number of studies question the validity of the

AASHTO M320 specifications for modified systems. Applica-

tion of polymers for bituminous pavement modification opens

new fields of application and research. The polymers that are

used for bitumen modification can be divided into two broad

categories, namely plastomers and elastomers. Despite consider-

able research about polymer modified bitumens (PMBs), plasto-

meric PMBs have still not been comprehensively characterized,

due to the complex nature and interaction of the bitumen and

polymer system. The literature on bitumen modification with

plastomeric polymers is quite scarce [2–6], especially with

respect to rheological properties. One of the principal plasto-

mers used in pavement applications is the semi-crystalline

copolymer, ethylene vinyl acetate (EVA). EVA polymers have

been used in road construction in order to improve both the

workability of the bitumen during construction and its defor-

mation resistance in service. This paper focuses on the use and

suitability of AASHTO M320 bitumen parameters for ranking

of polymer modified bitumens. The distress modes that are con-

sidered in this paper are rutting, load associated fatigue crack-

ing, and low temperature cracking.

AASHTOM320 BITUMEN RUTTING PARAMETER

The high temperature specification parameter for evaluating rut-

ting resistance (permanent deformation) in asphalt pavements

developed during the AASHTO M320 is a ratio of the complex

modulus and the phase angle (G*/sin(d)). The ineffectiveness of

the AASHTOM320 specification parameter G*/sin(d) in captur-

ing the high temperature performance of paving asphalts for rat-

ing their rutting resistance has been a significant concern [7,8].

There have been suggestions for refinement of the AASHTO

M320 specification parameter for the bitumens using new tests

and parameters such as repeated creep and recovery test [8],

G*/(1� (1/tan(d)sin(d))) [9], the zero-shear viscosity [8] and

multi stress creep recovery (MSCR) in AASHTO TP70-09 [10].

The zero-shear viscosity and permanent strain after repeated

creep test are difficult to run and determine, and have a lot of

questions as regards the accuracy of the measurements [7]. On

the other hand, the parameter G*/(1� (1/tan(d)sin(d))) needs a

change in the criterion requirement from the conventional 1000

Pa for unaged and 2200 Pa for rolling thin film oven test

(RTFOT)-aged at 10 rad/s to some other lower value at a lower

frequency in order to make it effective.

AASHTOM320 BITUMEN FATIGUE PARAMETER

The AASHTO M320 fatigue parameter was chosen to reflect

the energy dissipated per load cycle, which can be calculated as

G*sind. The specification prescribed a relationship whereby a

reduction in G*sind at 10 rad/s corresponds to improved fatigue

resistance. Validation of the AASHTO M320 bitumen fatigue

parameter with pavement performance has shown that,

although the bitumen properties are important, pavement struc-

tural effects may be equally or more important [11]. Bahia et al.

[8] reported that there was strong correlation between the

fatigue life of bitumen and that of mixture at intermediate tem-

perature and proposed cyclic fatigue test to replace the fatigue

parameter in the AASHTO M320 bitumen specification [8].

However, the testing time required to obtain the parameter was

too long to be an efficient specification test. Also, concerns

about repeatability and possible failures at boundaries of speci-

mens were raised by users of the test. Recent work by Martono

et al. [12] verified the suitability of using the dynamic shear rhe-

ometer for performing fatigue testing on bitumens and intro-

duced the concept of using a stress sweep or a strain sweep as

accelerated bitumen fatigue tests. Recently, Johnson et al. [13]

introduced a new fatigue testing protocol for bitumen, the mon-

otonic constant shear-rate test, which was demonstrated to have

great potential to be a fatigue test.

AASHTOM320 BITUMEN THERMAL CRACKING

PARAMETERS

Thermal cracking is widely recognized as a major cause of dis-

tress in asphalt pavements located in colder temperature cli-

mates. For a given pavement, the cracking temperature of the

bitumen used is considered to be a good indicator of the low

temperature cracking resistance of the whole pavement [14].

For unmodified bitumens, determination of cracking tempera-

ture is based on results from AASHTO T313 [15] bending

beam rheometer (BBR) test. Two bitumen parameters, i.e., the

stiffness and the m-value, are determined based on the BBR test

results at a loading time of 60 s. The cracking temperature is

defined as the temperature at which the stiffness reaches the

value of 300MPa or the m-value reaches the value of 0.3, or

moreover, the temperature at which one of the specification

thresholds is reached as temperature is decreased. The cracking

temperatures determined using BBR were found to be predictive

of low-temperature cracking in asphalt pavements constructed

using unmodified bitumens. However, it grossly over predicted

low-temperature cracking performance for modified bitumens.

As a result, for modified bitumens, additional testing using the

direct tension test (DTT) was proposed to address the case of

bitumens with a stiffness higher than 300MPa and with an

m-value greater than 0.3 [16,17]. In order to use the test, sophis-

ticated equipment (DTT and BBR) and analysis software are

required. Concerns were already raised about the expensive na-

ture of the approach because its use has become prohibitive to

Journal of Testing and Evaluation2

many practitioners. Shenoy [18] presented results that sug-

gested that BBR data alone may be sufficient for predicting

cracking temperature without the use of DTT data. Because of

the aforementioned issues, several surrogate test methods for

predicting cracking temperatures (Tcr) were developed by vari-

ous investigators. Roy and Hesp [19] used the thermal stress

restrained specimen test (TSRST) for predicting cracking tem-

peratures in both notched and un-notched bitumens. Kim [20]

and Mogawer et al. [21] developed the asphalt binder cracking

device (ABCD) for predicting cracking temperatures. The

authors reported a strong correlation between the cracking tem-

perature values using the ABCD method and the BBR and DTT

approach. It was, however, noted that use of the strain gauge

based method was cumbersome. In addition, the test provides

a narrow characterization of the low-temperature bitumen

properties [14].

Materials

The properties of aggregate and bitumen used in this research

study were presented in Tables 1 and 2, respectively. The poly-

mer used was EVA copolymer, which had melt indices (MI) of

2.5 g/10min, specific gravity of 0.938 g/cm3, and with a melting

point of 84�C (melting point is the temperature at which the

crystalline fractions of the EVA copolymer are melted) and

vinyl acetate (VA) content of 18 % by mass. Three levels of

EVA content were investigated namely 2, 4, and 6 % by weight

of bitumen. The polymer modified bitumens were prepared

using a low shear mixer at 180�C at a speed of 125 rpm. The

mixing time was 2 h. Table 4 shows bitumen codes used for

identification of test specimens.

The viscosity of bitumens at high temperature is an impor-

tant property since it reflects the bitumen’s ability to be pumped

through an asphalt plant, thoroughly coat the aggregate in hot

mix asphalt (HMA) mixture, and be placed and compacted to

form a new pavement surface. Table 4 shows the rotational vis-

cosity at 135�C according to AASHTO T316 procedure for all

bitumens. All bitumens satisfied the maximum limit for viscos-

ity of bitumens at 135�C set forth by AASHTO M320 (i.e.,

3.0 Pa s).

The aggregate gradation of all asphalt mixtures used in this

paper was shown in Fig. 1 and Table 3 which is typical for a

asphalt mixture wearing course with a maximum nominal

aggregate size of 12.5mm. The mixture design procedure was in

accordance with standard Marshall mix design procedure

(ASTM D1559-89 [22]) with compaction of specimens at

TABLE 1 Aggregate properties.

Properties Test Method Result Requirements

Coarse Aggregate

Los Angeles abrasion (%) AASHTO T96 20 maximum 30

Angularity (%) ASTM D5821 100 minimum 90

Elongation BS-812 11

Flakiness BS-812 22 maximum 25

Bulk specificgravity (gram/cm3)

AASHTO T85 2.654

Apparent specificgravity (gram/cm3)

AASHTO T85 2.709

Water absorption (%) AASHTO T85 0.8 maximum 2.5

Fine Aggregate

Plasticity Index AASHTO T89, T90 Non-plastic Non-plastic

Sand Equivalent AASHTO T1769 38

Bulk specificgravity (gram/cm3)

AASHTO T84 2.617

Apparent specificgravity (gram/cm3)

AASHTO T84 2.719

Water absorption (%) AASHTO T84 1.4 maximum 2.5

Filler (crushed limestone)

Plasticity index AASHTO T89, T90 Non-plastic

Specific gravity (gram/cm3) AASHTO T100 2.702

TABLE 2 Properties of unmodified bitumen.

Test Method

Parameters Unit ASTM AASHTO Results

Specific gravity gram/cm3 D70 T228 1.011

Penetration 0.1mm D5 T49 55

Softening point �C D36 T53 51

Ductility cm D113 T51 >100 cm

Solubility (%) D2042 T44 99.5

Flash point (Cleveland) �C D92 T48 303

Kinematic viscosity @ 120�C centistokes D2170 T201 1051

Kinematic viscosity @ 135�C centistokes D2170 T201 361

Kinematic viscosity @ 160�C centistokes D2170 T201 170

Heating loss — D1754 T179 �0.002Penetration after heating loss 0.1mm — — 47

Penetration after heatingloss to original penetration

% — — 85.4

Ductility after heating loss cm — — >50 cm

Penetration index — — — �0.73PVN (25–135) — — — �0.39

FIG. 1 Aggregate gradation of asphalt mixtures.

SHEIKHMOTEVALI AND AMERI ON PAVEMENT PERFORMANCE 3

75 blows on each side of cylindrical samples (10.16 cm in diam-

eter and 6.35 cm thick). Samples were prepared with bitumen

contents of 4.0, 4.5, 5.0, 5.5, 6.0, and 6.5 % by weight of the total

mix. The optimum bitumen content was found to be 5.6 % by

total weight of mixture for the asphalt mixture containing origi-

nal base bitumen. An optimum bitumen content of 5.6 % was

chosen for all mixtures so that the amount of bitumen would

not influence the analysis of the test data. For the dynamic

creep, creep compliance, and indirect tensile fatigue tests, the

specimens were compacted in a similar way. Table 4 shows mix-

ture codes used for identification of test specimens.

Methods

AASHTOM320 BITUMEN TESTS

In this research study, the properties of bitumens were eval-

uated using AASHTO M320 bitumen tests including the BBR

test (AASHTO T313) and the dynamic shear rheometer (DSR)

test (AASHTO T315-09 [23]). Three duplicate samples were

tested and the results were reported as the average of these tests.

In the DSR rutting test, the bitumens were tested at 58�C and a

frequency of 10 rad per second. In the DSR fatigue test, the bitu-

mens were tested using an 8mm parallel plate at 25�C. The

BBR test was conducted using each beam (125 by 6.35 by

12.7mm) at�12�C, and creep stiffness (S) and creep rate (m) of

the bitumens were measured at a loading time of 60 s.

ASPHALT MIXTURE PERFORMANCE TESTS

Dynamic Creep Rutting Test

For evaluating rutting resistance of asphalt mixtures, a dynamic

creep test under haversine shape load pulse was conducted for

all mixtures in accordance with NCHRP 9–19 [24]. In this

research study, dynamic creep test consists of 10 000 load cycles

with 0.1 s duration followed by a 0.9 s rest period and maximum

axial stress of 210 KPa at a test temperature of 54�C.

Indirect Tensile Fatigue Test

The indirect tensile fatigue test (ITFT) was used as a practical

method to estimate the resistance to cracking [25]. The test was

carried out at 250, 350, and 450 KPa stress levels in controlled

stress mode at 20�C with haversine wave shape. The load was

applied for 0.25 s followed by a rest period of 1.25 s. The failure

was established as the complete fracture of the specimen.

Creep Compliance Test at Low Temperature

Based on NCHRP-Report 530 [26], compliance values as deter-

mined using the indirect tensile procedure tend to agree very well

with those determined in uniaxial compression but not with val-

ues determined using uniaxial tension. Uniaxial compression is

suitable for determining creep compliance for research purposes;

thus, in this research study, a creep compliance test was per-

formed in uniaxial compression at �10�C. During this test, the

specimen was loaded with a constant load for 1000 s.

Results

RANKING OF POLYMER MODIFIED BITUMENS BASED

ON AASHTO M320 BITUMEN PARAMETERS

Result of DSR Rutting Test

The AASHTO M320 specifications specify minimum values of

1.0 and 2.2 KPa for the G*/sind of unaged and RTFOT-aged bitu-

mens, respectively, at the high performance grade temperature.

In general, the higher G*/sind values indicate that the bitumens

will be less susceptible to permanent deformation at high

pavement temperatures. The rutting resistance parameter, the

TABLE 3 Aggregate blending and gradation.

AggregateGravel

12–19 in.Gravel6–12 in.

Sand0–6 in. Filler

Blending (%) 8 23 68 1

SieveSize (mm) Percent Passing (%)

Job MixFormula

19 100 100

12.5 28 100 94

9 0 86 100

4.75 2 97 67

2.4 0 60 100 41

0.3 14 77 10

0.075 9 51 6.3

0.02 19

0.005 8

0.002 5

FIG. 2 Result of DSR rutting test at 58�C (unaged bitumens).

TABLE 4 Mixture and bitumen codes and compositions.

BitumenCode

Polymer Content byWeight of Base Bitumen (%)

Brookfield ViscosityPass @ 135�C

MixtureCode

O.B. 0 0.348 Control

EVA2 2 0.511 MEVA2

EVA4 4 1.04 MEVA4

EVA6 6 1.934 MEVA6

Journal of Testing and Evaluation4

G*/sind, of all bitumens, was measured at 58�C and the results

were shown in Figs. 2 and 3. For all bitumens, there is an increase

in G*/sind with an increase in EVA content. Therefore, the rut-

ting resistance is in the order EVA6>EVA4>EVA2>O.B.

Result of DSR Fatigue Test

In the AASHTO M320 bitumen specification, the product of

the complex shear modulus, G*, and the sine of the phase angle,

d, is used to help control the fatigue of flexible pavements. The

AASHTO M320 bitumen specification has a maximum value of

5000 KPa for G*sind and lower G*sind values are generally con-

sidered desirable attributes from the standpoint of resistance to

fatigue cracking. The G*sind values of all bitumens were

depicted in Fig. 4. This trend shows fatigue resistance is in the

order EVA4>EVA6>EVA2>O.B.

Result of BBR Test

The creep stiffness modulus (S) and creep rate (m) of all bitu-

mens were determined by the BBR software at 60 s loading time

and shown in Figs. 5 and 6, respectively. Stiffness modulus and

m-value of all bitumens in this research study meet AASHTO

M320 requirements. The S-value is no more than 300MPa and

m-value is larger than 0.3. Figure 5 indicates that the values of

stiffness modulus (S) of bitumens decrease with the increase of

EVA content, whereas the m-values shows its respective change

law (Fig. 6). As the stiffness modulus (S) increases, the thermal

stresses developed in the pavement due to thermal shrinking

also increase, and thermal cracking becomes more likely. On

the other hand, as the m-value decreases, the rate of stress relax-

ation decreases and the ability of the flexible pavement to relieve

thermal stresses by flow decreases. Therefore, bitumens with the

smaller stiffness modulus and the larger m-value have a good

low temperature anti-cracking property. The smaller the S/m,

the better the low temperature performance is. The relationship

between S/m and EVA content (Fig. 7) shows low temperature

cracking resistance is in the order of EVA4>EVA2>O.B.

>EVA6.

RANKING OF POLYMER MODIFIED BITUMENS BASED

ONMECHANICAL TESTING OF MIXTURES

Because the same aggregate gradation was used for all mixtures,

the test results could directly represent the effects of bitumens

used in the mixtures on their performance and rank them.

Result of Dynamic Creep Test

Figure 8 shows the relationship between the number of cycles

and the axial accumulated permanent deformation for the

tested groups. The relationship between the accumulated

FIG. 3 Result of DSR rutting test at 58�C (RTFOT aged bitumens).

FIG. 4 Result of DSR fatigue test at 20�C (PAV aged bitumens).

FIG. 5 Result of BBR test S-value variation at �12�C (PAV aged bitumens).

FIG. 6 Result of BBR test m-value variation at �12�C (PAV aged bitumens).

SHEIKHMOTEVALI AND AMERI ON PAVEMENT PERFORMANCE 5

permanent strain and the number of load repetitions are

expressed generally in the form:

e ¼ a Nð Þb(1)

where:

e¼ the accumulated permanent strain due to dynamic ver-

tical loading,

N¼ the number of load applications that produced e, and

a and b¼ regression constants that depend on the material

and stress state conditions.

Analyses from laboratory tests were successful in identify-

ing parameters that could be considered suitable indicators of

mixture sensitivity to permanent deformation. For repeated

loading compression tests, they include the coefficients a and b

from the best-fit line on the log–log plot of accumulated strain

versus load repetitions and the flow number. The b and a values

were obtained for all mixtures and presented in Figs. 9 and 10,

respectively. Lower b values suggest mixes with lower rutting

susceptibility; hence the rutting resistance is in the order

MEVA4>MEVA6>MEVA2>Control.

Result of Indirect Tensile Fatigue Test

Figure 11 shows the number of cycles to failure in the force

(stress)-controlled mode. Figure 12 shows the constants of the

regression equations relating the fatigue life to stress levels. The

general equation for the relationship is in the form of Eq 1:

Nf ¼ k1 rð Þ�k2(2)

where:

Nf¼ the fatigue life of the asphalt mixture,

r¼ the tensile stress, and

k1, k2¼ the fatigue coefficients.

There is an increasing trend in the resistance to fatigue

damage with increasing EVA content so the fatigue resistance is

in the order MEVA6>MEVA4>MEVA2>Control.

Result of Creep Compliance Test

In rheological theory, the Burger model is a classical four-unit

mode (two spring components and two dashpot components)

and very suitable to describe the viscoelasticity of bituminous

material. Equation 3 shows the relationship between creep com-

pliance and four Burgers model parameters at time t.

DðtÞ ¼ 1E1þ t

g1þ 1E2

1� e�E2g2t

� �(3)

FIG. 7 S/m-value variation at �12�C (PAV aged bitumens).

FIG. 8 Result of dynamic creep test at 54�C.

FIG. 9 Creep strain slope of all mixtures at 54�C.

FIG. 10 Intercept of creep curves of all mixtures at 54�C.

Journal of Testing and Evaluation6

where:

D(t)¼ creep compliance, 1/MPa,

E1 and E2¼ instantaneous and delayed elastic modulus,

MPa, respectively, and

g1 and g2¼ both viscous coefficient, MPa s.

The four Burgers’ parameters in Eq 3, relaxation time

(k1 ¼ E1=g1), and delay time (k2 ¼ E2=g2) were calculated

based on the results of creep compliance test (Fig. 13). The

results were shown in Table 5.

For viscoelastic materials, the external work can transform

into the energy of the following forms: elastic strain energy

stored in materials, dissipation energy caused by the material

flow, and surface energy caused by crack occurrence and devel-

opment [27]. During the creep test, the load applied to the spec-

imen is constant and small, and the specimen cannot be broken

until test time is over. Therefore, the external work can be trans-

formed as stored energy and dissipation energy, which mainly

makes the material flow. Considering the nature of Burger’s

model components, springs are associated with storage and

dashpots with dissipation of deformation energy; therefore, the

Burger’s model parameters are used to calculate dissipated and

stored energy. The energy per volume, W, is integrated for each

spring and dashpot in the model with the general relation

W ¼Ð

rde, which is based on the definition of mechanical

work as force times path. For stored and dissipated energy, Eq 4

and Eq 5 are obtained [27]:

Wstored tð Þ ¼ r20

1E1þ 12E2

1� 2e�E2g2t þ e�

2E2g2t

� �� �(4)

Wdissipated tð Þ ¼ r20

tg1þ 12E2

1� e�2E2g2t

� �� �(5)

In order to fully investigate the influence of EVA on the low tem-

perature performance, the concept of dissipation energy ratio

(DER), which is defined as a ratio between dissipation energy

and stored energy, was used in the analysis. The larger dissipation

energy or DER implies the material has a good internal flow, i.e.,

material has a good ability to relax the stresses in material [27].

DER ¼

tg1þ 12E2

1� e�2E2g2t

� �1E1þ 12E2

1� 2e�E2g2t þ e�

2E2g2t

� �(6)

The DERs of control and EVA modified mixtures were calculated

by Eq 6 (t¼ 60 s) according to Ref. [27]. Change of DERs with

EVA content was plotted in Fig. 14 so the low temperature cracking

resistance is in the order MEVA4>MEVA2>Control>MEVA6.

COMPARISON OF BITUMEN RANKING METHODS

G*/sin d— b Value Diagram

The bitumen high temperature parameter, G*/sind was plotted

against rutting parameter, b value. As seen in Figs. 15 and 16, the

FIG. 11 Result of indirect tensile fatigue test of all mixtures.

FIG. 12 Constants of asphalt mixtures fatigue life equation.

FIG. 13 Creep compliance curve of all mixtures at �10�C.

TABLE 5 Variation of burger model parameters with polymer

content.

Control MEVA2 MEVA4 MEVA6

E1 (MPa) 132 110 370 231

E2 (MPa) 111 141 672 1133

g1 (MPass) 3833 1318 3912 14 124

g2 (MPass) 178 137 157 198

Relaxtion time (s) 29 12 11 61

Delay time (s) 1.61 0.97 0.23 0.17

SHEIKHMOTEVALI AND AMERI ON PAVEMENT PERFORMANCE 7

relationship is linear except at 6 % polymer. This indicates that

the current AASHTO M320 high temperature bitumen specifi-

cation is valid for low polymer contents and does not capture

the complete performance characteristics of the modified sys-

tems at high polymer contents.

G*sin d—K2 Diagram

Using the hypothesis that a reduction in G*sind will correspond

to improved fatigue resistance, the G*sind values were com-

pared with the K2 values (Fig. 17). It is observed that with the

increase in EVA content, the fatigue resistance is improved,

while the G*sind values of corresponding bitumens is decreased

except at 6 % polymer and so AASHTO M320 intermediate

temperature bitumen specification is valid for low polymer con-

tents and it is not possible to use AASHTO M320 for fatigue

evaluation of EVA PMBs at high polymer contents.

S/m—DER Diagram

The ranking as a function of the mixture DER parameter and

bitumen S/m value was presented in Fig. 18. It is observed that

FIG. 14 Variation of DER parameter with polymer content at �10�C.

FIG. 15 Comparison of bitumen G*/sin(d) ranking and mixture b value

ranking (unaged).

FIG. 16 Comparison of bitumen G*/sin(d) ranking and mixture b value

ranking (RTFOT aged).

FIG. 17 Comparison of bitumen G*sin(d) ranking with mixture fatigue K2

ranking.

FIG. 18 Comparison of bitumen S/m ranking with mixture DER ranking.

Journal of Testing and Evaluation8

except at 6 % EVA, by decreasing S/m-value, the mixture DER

parameter is increased. From the above analysis, one can con-

clude that thermal cracking performance of EVA PMBs at high

polymer contents is mixture-dependent and cannot be pre-

dicted from bitumen properties.

Conclusions

In present paper, two methods were used for performance rank-

ing of a series of EVA PMBs in terms of the three main distress

modes associated with flexible pavements of low temperature

cracking, permanent deformation (rutting), and fatigue damage.

AASHTO M320 bitumen parameters, practical mechanical

asphalt mixture properties were used for the ranking of EVA

PMBs, and then the rankings were compared. The following

conclusions were obtained:

• AASHTO M320 bitumen parameters, G*/sind andG*sind, give a good indication of relative rutting andfatigue resistance for polymer modified bitumens at lowpolymer contents; however, it is not possible to evaluatefatigue and rutting resistance of PMBs at high polymercontents from the bitumen properties correctly.

• AASHTO M320 bitumen parameters, S- and m-values,show good relation to thermal cracking performance ofPMBs at low polymer contents. Mixture characteristicsmay have a significant effect on the thermal cracking per-formance of polymer modified bitumens at high polymercontents.

• AASHTO M320 bitumen parameters are valid for PMBsonly at low polymer contents. It is an important conclu-sion because the high cost of polymers makes the com-mercial use of modified bitumens only attractive for roadconstruction if the amount of polymer is relatively small.For evaluation of polymer modified bitumens at highpolymer contents, tests should be conducted on mixturesto provide a reasonable expectation of the performance ofthe polymer in the mixture, and AASHTO M320 bitumenparameters may result in misleading ranking.

References

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[2] Ameri, M., Mansourian, A., and Sheikhmotevali, A. H.,“Investigating Effects of Ethylene Vinyl Acetate and Gil-sonite Modifiers Upon Performance of Base BitumenUsing Superpave Tests Methodology,” Constr. Build.Mater., Vol. 36, 2012, pp. 1001–1007.

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