Fatigue Behavior of Rubberized Asphalt Concrete
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Fatigue Behavior of Rubberized Asphalt Concrete Mixtures Containing Warm
Asphalt Additives
Feipeng Xiao1*
, Ph.D., P.E., Wenbin Zhao2, and Serji N. Amirkhanian
3, Ph.D.
1Research Assistant Professor, Asphalt Rubber Technology Service, Department of CivilEngineering, Clemson University, Clemson, SC 29634-0911 U.S.A., Tel: 001-864-6566799,
Fax: 001-864-6566186, E-mail: [email protected]
2Graduate Research Assistant, Department of Civil Engineering, Clemson University, Clemson,
SC 29634-0911
3Professor, Department of Civil Engineering, Clemson University, Clemson, SC 29634-0911
ABSTRACT:The long-term performance of pavement is associated with various factors such as pavementstructure, materials, traffic loading, and environmental conditions. Improving the understanding
of the fatigue behavior of the specific rubberized warm mix asphalt (WMA) is helpful in
recycling the scrap tires and saving energy. This study explores the utilization of theconventional fatigue analysis approach in investigating the fatigue life of rubberized asphalt
concrete mixtures containing the WMA additive. The fatigue beams were made with one rubber
type (-40 mesh ambient crumb rubber), two aggregate sources, two WMA additives(Asphamin and Sasobit), and tested at 20C. A total of 8 mixtures were performed and 29
fatigue beams were tested in this study. The test results indicated that the addition of crumb
rubber and WMA additive not only reduced the mixing and compaction temperatures of
rubberized asphalt mixtures offset by crumb rubber but also effectively extended the long-term
performance of pavement when compared with conventional asphalt pavement. In addition, theexponential function forms are efficient in achieving the correlations between the dissipated
energy and load cycle as well as mixture stiffness and load cycle.
Keywords: Rubberized asphalt concrete; Warm asphalt additive; Mixing and compaction
temperature; Stiffness; Dissipated energy; Fatigue Life.
*: Corresponding author
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INTRODUCTION
Fatigue cracking, called alligator cracking and associated with repetitive traffic loading, is
considered to be one of the most significant distress modes in flexible pavements. The fatigue
life of an asphalt pavement is directly related to various engineering properties of a typical hot
mix asphalt (HMA). The complicated microstructure of asphalt concrete is related to the
gradation of aggregate, the properties of aggregate-binder interface, the void size distribution,
and the interconnectivity of voids. As a result, the fatigue property of asphalt mixtures is very
complicated and sometimes difficult to predict (1-3).
Understanding the ability of an asphalt pavement to resist fractures from repeated loading
condition is essential for developing superior HMA pavement designs. Previous studies have
been conducted to understand the occurrence of fatigue and how to extend pavement life under
repetitive traffic loading (3-4). However, reaching a better understanding of fatigue behavior of
asphalt pavements continues to challenge researchers worldwide, particularly as newer materials
with more complex properties are being used in the field.
The recycling of scrap tires has been of interest to the domestic and international asphalt
industry for over 40 years. The utilization of crumb rubber modifier (CRM) in asphalt binders
has proven to be beneficial from many stand points. The use of CRM, expanded to HMA,
continues to evolve since the CRM binders enhance the performance of asphalt mixtures by
increasing the resistance of the pavements to permanent deformation and thermal and fatigue
cracking. Many researchers have found that utilizing crumb rubber in pavement construction is
both effective and economical (5-9).
Recently, the warm mix asphalt (WMA) is widely being used in the hot HMA industry as
a mean of reducing energy requirements and lowering emissions. WMA can significantly reduce
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the mixing and compacting temperatures of asphalt mixtures, by either lowering the viscosity of
asphalt binders, or causing foaming in the binders. Reduced mixing and paving temperatures
decreases the energy required to produce HMA, reduces emissions and odors from plants, and
makes for better working conditions at both the plant and the paving site (10-15).
However, the influence of crumb rubber and WMA additives mixed with virgin mixtures
together has not yet been identified clearly. The interaction of modified mixtures is not well
understood from the standpoint of binder properties and field performance. It has been shown
that the WMA additives reduce the mixing and compaction temperatures and achieve ideal
workability of HMA without significantly affecting the engineering properties of the mixtures
(10-13). While the addition of crumb rubber increases the demand of asphalt binder and
increases the mixing and compacting temperatures, it is helpful in resisting the high temperature
deformation and extending the long-term performance of HMA. Because of the complicated
relationships of these two materials in the modified mixtures, detailed information will be
beneficial to help obtain an optimum balance in the use of these materials. Very few fatigue
studies of modified asphalt mixtures, including crumb rubber and warm asphalt additives, have
been performed in recent years (16). However, the utilization of these materials will enable the
engineers to find an environmentally friendly method to deal with these materials, save money,
energy, and furthermore, protect the environment.
The objective of this study was to gain an improved understanding in the long-term
performance characteristics (fatigue behavior) of the rubberized asphalt concrete mixtures
containing WMA additives through a series of experimental tests. Experiments were carried out
to evaluate rheological properties of the modified binder (unaged and aged binders) as well as
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the engineering properties of the mixture, such as the stiffness and fatigue life performed by
HMA flexural testing.
BACKGROUND
The fatigue characteristics of asphalt mixtures are usually expressed as relationships
between the initial stress or strain and the number of load repetitions to failure-determined by
using repeated flexure, direct tension, or diametral tests performed at several stress or strain
levels. The fatigue behavior of a specific mixture, characterized by the slope and relative level of
the stress or strain versus the number of load repetitions to failure, may be defined using the
following equation (17).
cb
f SaN )/1()/1( 00 orcb
f SaN )/1()/1( 00 (1)
Where fN = number of load application or crack initiation, 00 , = tensile strain and stress,
respectively, So= initial mix stiffness, and a, b, c= experimentally determined coefficients.
In recent years, several researchers have used the energy approach for predicting the fatigue
behavior of the asphalt mixtures. The dissipated energy per cycle, Wi, for a linearly viscoelastic
material is given by the following equation (18-22):
1 1
sin( )n n
i i i i
i i
W W
(2)
Where, W= cumulative dissipated energy to failure,iW = dissipated energy at load cycle i,
i = stress amplitude at load cycle i, i = strain amplitude at load cycle i, and i = phase
shift between stress and strain at load cyclei.
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Research has shown that the dissipated energy approach makes it possible to predict the
fatigue behavior of mixtures in the laboratory over a wide range of conditions based on the
results of a few simple fatigue tests. Such a relationship can be characterized in the form of the
following equation (18-22):
Z
fNAW )( (3)
Where, Nf = fatigue life, W= cumulative dissipated energy to failure, and A, Z =
experimentally determined coefficients.
EXPERIMENTAL PROGRAM AND PROCEDURES
Materials
One virgin binder (PG 64-22) and one crumb rubber modified (CRM) binder (PG 64-22 +
10% -40 mesh rubber) were used in this study. The PG 64-22 binder was a mixture of several
sources that could not be identified by the supplier. One type of rubber, -40 mesh ambient rubber,
was used in this study. Previous research and field projects conducted in South Carolina
indicated that the -40 mesh ambient rubber is effective in improving the engineering properties
of rubberized mixtures.
Asphamin and Sasobit were used in this study as two WMA additives. Aspha-min is
SodiumAluminumSilicate which is hydro thermally crystallized as a very fine powder. It
contains approximately 21% crystalline water by weight. By adding it to an asphalt mix, the fine
water spray is created as all the crystalline water is released, which results in volume expansion
in the binder, therefore increasing the workability and compactability of the mix at lower
temperatures. Sasobit is a long chain of aliphatic hydrocarbons obtained from coal gasification
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using the Fischer-Tropsch process. After crystallization, it forms a lattice structure in the binder
which is the basis of the structural stability of the binder containing Sasobit (10-11).
Two aggregate sources (A and B) were used for preparing the samples (Table 1). Aggregate
A, a type of granite, is predominantly composed of quartz and potassium feldspar while
aggregate B (schist) is a metamorphic rock. Hydrated lime, used as an anti-strip additive, was
added at a rate of 1% by dry mass of aggregate. A total number of eight mixtures were evaluated
in this research. In this paper, the mixtures made from aggregates A and B without rubber and
WMA additive are referred to as ACO and BCO; and the mixtures with rubber but no WMA
additive are referred to as ARO and BRO. In addition, the mixtures with rubber and Asphamin
are designated as ARA and BRA, and the mixtures with rubber and Sasobit are labeled as ARS
and BRS, respectively.
Superpave mix design
The combined aggregate gradations for the 12.5 mm mixtures were selected in accordance
with the specification set by the South Carolina Department of Transportation (SCDOT). The
gradations for each aggregate source (A and B) are shown in Figure 1, which shows that the
design aggregate gradations for each aggregate source are the same when using different WMA
additives (Asphamin and Sasobit ) at the same percentages of rubber (0% or 10% rubber),
while the gradations are similar when comparing mixtures from both aggregate sources.
Superpave mix design defines that the laboratory mixing and compaction temperatures can
be determined by using a plot of viscosity versus temperature. While there are no previous
specifications available regarding the mixing and compaction temperatures for rubberized
mixture containing WMA additives, some researchers have developed guidelines for mixing and
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compaction temperatures when using either WMA or rubber (10-11, 23-24). The temperatures,
shown in Table 3, were determined in accordance with previous research projects (16, 24).
Though the mixing and compaction temperatures increase as the percentage of crumb rubber
increases, these can be reduced by adding either Asphamin or Sasobit.
Fatigue beam fabrication and test procedures
Fatigue beams were made in the laboratory and two-four beams of each mixture were tested
for this study (Figure 2). All tests were performed in a temperature-controlled chamber at 20
0.5C. In this study, a repeated sinusoidal loading at a frequency of 10 Hz was used; in addition,
the controlled strain mode was employed. The control and data acquisition software measured
the deflection of the beam specimen, computed the strain in the specimen and adjusted the load
applied by the loading device (AASHTO T321).
The test apparatus also recorded load cycles, applied load, and beam deflections. Failure is
assumed to occur when the stiffness reaches half of its initial value, which is determined from
the load at approximately 50 repetitions; the test is terminated automatically when this load has
diminished by 50 percent. The flexural stiffness and dissipated energy of fatigue beam are
determined as follows (AASHTO T321):
1. Flexural stiffness (Pa):
2 2
3
(3 4 )/
4
aP l aS
b h
(4)
Where, = tensile stress, in Pa; = maximum tensile stain, in m/m;P= applied peak-
to-peak load, in Newton; a= space between inside clamps, in meters; b= average beam
width, in meters; h = average beam height, in meters;= beam deflection at neutral axis,
in meters; and l = length of beam between outside clamps, in meters.
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2. Dissipated energy (J/m3) per cycle:
)360sin( fD (5)
Where,f = load frequency, in Hz; and = time lag betweenmax
P and max , in second
3. Cumulative dissipated energy (J/m3):
W=
ni
i
iD1
(6)
Where,Di =Dfor the ith
load cycle
ANALYSIS OF TEST RESULTS
Statistical considerations
Results of the stiffness, cumulative dissipated energy, and fatigue life values were
statistically analyzed with 5% level of significance (0.05 probability of a Type I error) with
respect to the effects of aggregate sources and WMA additive types. For these comparisons, it
should be noted that all specimens were produced at optimum binder content.
Binder analysis
Table 3 shows that the viscosity of rubberized asphalt binder decreases while the high
temperature performance (G*/sin) of overall binders increase with the addition of WMA
additive. The unaged binder test result shows that the Asphamin and Sasobit can improve
the workability (viscosity) and rutting resistance (G*/sin) of mixtures. While the aged
rubberized binders show that the G*sin values decrease with the addition of rubber, these values
increase slightly as the WMA additives are added. It also can be seen that the stiffness values of
binders have similar trends with G*sin values due to the addition of these materials. Aged
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binder properties show that the WMA additives produce a slightly effect on the long-term
performance of asphalt binder.
Analysis of fatigue test results
Testing data were analyzed using Equations 4-6 presented earlier to compute the stress,
strain, stiffness, phase angle, the dissipated energy per cycle as the function of the number of
load cycles, and the cumulative dissipated energy to a given load cycle. In this study, fatigue life
was defined as the number of repeated cycles corresponding to a 50 percent reduction in initial
stiffness, which was measured at the 50
th
load cycle. Several fatigue beam specimens were
utilized to characterize the fatigue behavior of a mixture in order to avoid too much or too little
loss in stiffness. This procedure involved testing control specimens (ACO and BCO samples) at
a 500 micro strain level with the controlled strain mode of loading at a frequency of 10 Hz.
Table 4 presents a typical analyzed fatigue test results which were computed at various
cycles from the raw data. It can be seen that the stress value and dissipated energy per cycle
generally decrease as the number of cycle increases. That is, at the same strain level, the greater
stress is needed to reach the desired strain values at the beginning of fatigue test than at the end
of the test. At the same time, the dissipated energy per cycle during the first thousands of cycles
is remarkably greater than those during the final cycles (50% loss of initial stiffness). As
expected, the asphalt pavement in the field rapidly releases the potential energy within the first
several years, followed by the further reduction of pavement performance caused by micro-
cracking under repeated traffic loading conditions. Previous research also presents this similar
long-term performance process (3-4, 21, 22).
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The test results presented in Figure 3(a) show that the fatigue life of fatigue beams made
from aggregate A has a greater value than those made from aggregate B, though the aggregate B
has a lower LA abrasion loss and absorption values. Conversely, the standard deviations of the
fatigue test results for each mixture are large since the variability of fatigue life is generally
based upon the micro-structure of beams (e.g. the aggregate-binder interface, the void size
distribution, the interconnectivity of voids, distribution of aggregate particles, film thickness and
the aged status of binder). Through previous research, which also determined that large
variabilities exist in the fatigue test results, the authors found that increasing the number of the
repeated specimens reduced the variability (24). Moreover, in comparison with the control
fatigue beam (without rubber and WMA additive), the rubberized fatigue beam without WMA
additive or with Sasobit additive has a slightly greater fatigue life while the rubberized fatigue
beam with Asphamin additive has a slightly lower fatigue life, regardless of aggregate sources.
Figure 3(a) shows that the addition of crumb rubber and/or Sasobit slightly benefits the long-
term performance of asphalt pavement while the Asphamin results in a slight decrease of the
fatigue life, though these additives are critical in reducing the mixing and compaction
temperatures of mixture. In addition, the statistical analysis (t-statistics) in Table 5 indicates that,
with respect to the effect of aggregate source, there is a significant different fatigue life value
between any two aggregate sources regardless of mix types. As shown in Table 6, the influence
of a WMA additive on the fatigue life is generally not significant (p-value > 0.05) for overall
mixtures
The flexural stiffness of an asphalt pavement, associated with repetitive traffic loading
and pavement thickness, is related to the various aspects of HMA, such as rutting, resilient
modulus, and fatigue life. In this study, the fatigue beams were made with a height of
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approximate 50 mm and the values were competed from Equation (3), defined as the ratio of
tensile stress-to-tensile strain. The test results shown in Figure 3(b) show that the aggregate A
mixture has greater stiffness values since under the repeated loading the induced micro-strain of
the mixture from aggregate A is smaller. This greater stiffness may be the result of different
aggregate sources producing different interfaces among the binder, voids, and aggregate, thus,
affecting the corresponding fatigue behavior of the pavement. Previous research indicates that
while the initial stiffness of rubberized mixture is less than the conventional mixture (19), the
initial stiffness values of mixtures in this study showed no obvious trend when the additional
crumb rubber and WMA additive were blended together. Moreover, the statistical analysis in
Tables 5 and 6 indicates that aggregate source has a significant influence on the stiffness values
generally while the effects of rubber and WMA additive is not significant for all four types of
mixtures.
The dissipated energy, computed from Equations 5 and 6 was used as an indicator of
fatigue cracking in the asphalt layer (19-22). As shown in Figure 3(c), the cumulative dissipated
energy of mixture made from aggregate B is slightly higher than that of mixture from aggregate
A. However, the statistical results in Table 5 indicate that, except for the mixture with Sasobit
additive, other mixtures from two aggregate sources have no significant different cumulative
dissipated energy values. With respect to the effect of rubber and WMA additive, Table 6 shows
that there is a significant different value between control and rubberized mixture in general, but
the influence of WMA additive on cumulative dissipated energy is not significant for all
rubberized mixture.
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Correlation analysis of fatigue test factors
G*sin, strongly associated with fatigue life of the mixture, has become a basic parameter
used to describe fatigue characteristics of asphalt binder. Thus, the study of G*sin is beneficial
for researchers and engineers to analyze fatigue behavior of asphalt pavements. Table 3 indicates
the effect of rubber and WMA additive on G*sin of binder. In Figure 4(a), it can been seen that
the fatigue life decreases remarkably with a corresponding increase of G*sin regardless of
aggregate source. Figure 4 indicates that the binder aging process, for the materials used in this
research, does shorten the fatigue life of asphalt pavement. However, the addition of crumb
rubber enhances the long-term performance of asphalt pavement.
The correlations between the stiffness of the beam and binder are shown in Figure 4(b).
Similar to Figure 4(a), it can be seen that the stiffness values of the beam do not have a large
alteration with an increase in binder stiffness. Table 3 shows that the rubberized binders have
lower stiffness values than original asphalt binder. However, the stiffness values of the
rubberized mixture do not exhibit a similar trend. In addition, as shown in Figure 4(b), two
aggregate sources also show the different effects on mixture stiffness in terms of binder stiffness
in this study.
AASHTO T321 assumes that the fatigue life depends on the accumulation of dissipated
energy from each load cycle. Thus, the dissipated energy may be plotted against load cycles for
the particular load cycles where the data was collected. As shown in Figure 5, the correlations
between the dissipated energy per cycles with load cycles indicate that the dissipated energy
increases at a negative exponential growth as the number of load cycles increase, in other words,
the dissipated energy decreases insignificantly initially and then it reduces rapid prior to reaching
the 50% stiffness. For example, as shown in Figure 5(a), the dissipated energy of three fatigue
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beams exhibits a slightly decrease before the number of the repeated loads is less than 10,000
cycles, after that, the dissipated energy decreases quickly until the final load cycle accomplishes.
Figure 5 indicates that the individual fatigue beam from each mixture has different
dissipated energy values per load cycle, regardless of the mixture types (i.e. ACO, ARO, etc) and
these values are greater when using aggregate B. The results in Figure 5 also show that the
crumb rubber and WMA additive do not affect the dissipated energy per cycle.
The initial stiffness of fatigue beam, determined by the initial tensile stress and strain, can
be plotted using stiffness (S) against load cycles (n) and best fitting the data to exponential
function of the form shown below:
bnS A e
(7)
Where, e = natural logarithm to the base e, and A, b = experimentally determined
coefficients.
As shown in Figure 6, it can be noted that, in most cases, the stiffness values of various fatigue
beams from same mixture present similar results, and the mixture from aggregate B has a greater
stiffness value. However, the addition of crumb rubber and WMA additive do not exhibit a
significant effect on the stiffness values regardless of aggregate sources.
The correlations between the repetition number of fatigue beam and cumulative
dissipated energy are shown in Figure 7(a). Although these two linear models can be used to
determine the predicted values, it was hard to obtain accurate results due to the limited test
specimens and variability of materials. Similarly, as shown in Figure 7(b), the loss of stiffness
under repeated loading, as expected, is also related to the cumulative dissipated energy though
they are not highly correlated with each other.
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CONCLUSIONS
The following conclusions were determined based upon the limited experimental data
presented regarding the fatigue life of the modified binder and mixtures for the materials tested
for this research project:
The combination of the crumb rubber and WMA additive in asphalt binder is beneficial
for improving the rheological properties of both the unaged and aged binders (e.g.
increase G*sin and reduce G*/sin values), The increase in the mixing and
compaction temperatures due to the addition of crumb rubber can be offset by adding the
warm asphalt additives, which lowers the mixing and compaction temperatures of
rubberized mixtures comparable to conventional HMA.
The experimental results indicated that fatigue life and stiffness of the rubberized WMA
mixture from aggregate A is greater than aggregate B while the cumulative dissipated
energy of mixtures made from aggregate A is slightly lower. Moreover, the fatigue life
of the mixtures made with crumb rubber and WMA additive is greater than the control
mixtures (no rubber and WMA additive), except the mixtures containing Asphamin
additive.
Statistical analysis results illustrated that there are no significant differences in the
stiffness and cumulative dissipated energy values for overall mixtures (control,
rubberized, or WMA mixtures) while fatigue life values from control mixtures are
significantly different with other rubberized mixtures. In addition, statistical results
presented the aggregate sources play a key role in determining fatigue life, stiffness and
cumulative dissipated energy values of mixtures.
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There are good correlations between the fatigue life and G*sin as well as mixture and
binder stiffness values. The exponential function forms are efficient in achieving the
correlations between the dissipated energy and load cycle as well as mixture stiffness
and load cycles.
ACKNOWLEDGMENTS
The financial support of South Carolina Department of Health and Environmental
Control (SC DHEC) is greatly appreciated. However, the results and opinions presented in this
paper do not necessarily reflect the view and policy of the SC DHEC.
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Table 1 Aggregate property of mixtures
Aggregate
Source
LA
Abrasion
Loss (%)
Absorption
(%)
Sand
Equivalent
Hardness
Dry
(BLK)
SSD
(BLK) Apparent
11/2
to3/4 3/4 to3/8 3/8 to #4
A 51 0.80 2.740 2.770 2.800 0.2 0.1 0.1 - 5
B 34 0.60 2.780 2.800 2.830 0.4 0.6 0.9 35 5
Specific Gravity Soundness % Loss at 5 Cycles
Table 2 Mixing and compaction temperatures of mixtures
Mixing temperature Compaction temperature
(C) (C)
ACO/BCO 152-158 132-138ARO/BRO 170-176 152-158
ARA/BRA 155-165 155-165
ARS/BRS 155-165 155-165 Note: ACO/BCO; ARO/BRO; ARA/BRA; and ARS/BRS-control; rubberized; rubberized
Asphamin ; and rubberized Sasobit from aggregates A and B, respectively
Table 3 Binder properties
Viscosity Std. G*/sin Std. G*sin Std. Stiffness Std.
PG 64-22 0.41 0.0 1.2 212.1 2970.0 572.8 221.0 20.5
PG 64-22R
1.60 0.0 3.7 60.8 1705.6 66.1 128.5 2.5
PG 64-22RA
1.48 0.1 4.7 631.9 2042.1 3.9 148.0 1.2
PG 64-22RS
1.44 0.1 5.2 469.4 2160.3 170.2 150.5 0.6
Mpa (-12C)kPa (25C)kPa (64C)Pa.s (135C)
Aged binder (RTFO+PAV)Unaged binder
Note: R-rubberized; A-Asphamin ; S-Sasobit
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Table 4 Typical analyzed fatigue test results (BCO-B)
Period Number Stress Strain Dynamic Stiffness Phase Angle Dissipated Energy Cumulative Engergy
Cycles Pa m/m Pa Degree J/m3
J/m3
50 1860.89 1.42E-04 1.31E+07 72 0.21 63.70
100 2110.50 1.53E-04 1.37E+07 72 0.26 130.03
250 2050.47 1.73E-04 1.19E+07 72 0.28 207.84
500 1706.07 1.25E-04 1.36E+07 72 0.17 308.91
1000 1864.05 1.72E-04 1.08E+07 72 0.26 361.95
1600 2074.17 1.74E-04 1.19E+07 72 0.29 382.90
2500 1875.11 1.65E-04 1.14E+07 72 0.25 445.51
5000 1750.30 1.66E-04 1.06E+07 72 0.23 484.11
10000 1728.18 1.79E-04 9.68E+06 72 0.25 537.07
15850 1497.53 1.91E-04 7.84E+06 72 0.23 567.47
19954 1289.00 1.66E-04 7.78E+06 72 0.17 581.37
25120 980.96 1.56E-04 6.29E+06 72 0.12 594.70
Table 5 Statistical analysis of mechanical properties in terms of aggregate sources
Cumulative energy Stiffness Fatigue life
Control 0.431 0.059 0.048
Rubberized 0.297 0.011 0.030
Rubberized+Asphmin 0.293 0.005 0.002
Rubberized+Sasobit 0.036 0.205 0.033
P-value Test properties (Agg. A & B)
Note: P-value < = 0.05 (significant difference); P-value > = 0.05 (No significant difference)
Table 6 Statistical analysis of mechanical properties in terms of mixture types
0~1 0~2 0~3 1~2 1~3 2~3
Cumulative energy 0.017 0.065 0.036 0.149 0.346 0.141
Stiffness 0.372 0.073 0.236 0.129 0.394 0.163
Fatigue life 0.194 0.194 0.226 0.125 0.145 0.308
P-value Mixture type (0-control, 1-rubberized, 2-rubberized+Asphmin, 3-rubberized+Sasobit)
Note: P-value < = 0.05 (significant difference); P-value > = 0.05 (No significant difference)
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0
20
40
60
80
100
Percentpassing
(%)
Sieve size (mm)
Agg. A
Agg. B
Low Range
Up Range
0.075 0.60 2.36 4.750.15 9.5 12.5 19.0
Figure 1 Gradations of aggregate A and B
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Figure 2 Fatigue beam and testing
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0
200000
400000
600000
800000
CO RO RA RS
Fatiguelife(cycle)
Mixture type
Aggregate A Aggregate B
2x105
0
4x105
8x105
6x105
(a)
0
5000000
10000000
15000000
20000000
CO RO RA RS
Stiffness(kPa)
Mixture type
Aggregate A Aggregate B2.0x107
0.5x107
1.5x107
1.0x107
0
(b)
0
200
400
600
800
1,000
CO RO RA RSCumulativedissipatedenergy(
J/m
3)
Mixture type
Aggregate A Aggregate B
(c)
Figure 3 Mechanical properties (a) Fatigue life; (b) Stiffness; (c) cumulative energy
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yA = -141.59x + 562241
yB = -19.604x + 96617
1
10
100
1000
10000
100000
000000
1000 2000 3000 4000
Fatiguelife
(cycle)
G*sin (kPa)
Aggregate A Aggregate B
104
10
103
102
0
106
105
(a)
yA = 4095.5x + 8E+06
yB = -15759x + 2E+07
100000
000000
000000
000000
100 150 200 250
Stiffness(kPa
)
Binder stiffness (MPa)
Aggregate A Aggregate B
108
105
106
107
(b)
Figure 4 Correlations, (a) fatigue life and G*sin; (b) mixture stiffnes and binder stiffness
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yA = 0.1508e-7E-06x
yB = 0.1468e-4E-06x
yC = 0.1249e-2E-06x
0.0
0.1
0.2
0.3
10 100 1000 100001000001000
Dissipatedenergy(J/m3)
Cycles
ACO-A
ACO-B
ACO-C
10 104103102 106105
yA = 0.1108e-6E-06x
yB = 0.117e-5E-06x
yD = 0.1499e-2E-06x
yC = 0.1372e-2E-06x
0.0
0.1
0.2
0.3
10 100 1000 1000010000010000
Cycles
ARO-A
ARO-B
ARO-C
ARO-D
10 104103102 106105
yA= 0.1454e-4E-06x
yB = 0.1647e-8E-06x
0.0
0.1
0.2
0.3
10 100 1000 1000010000010000
Cycles
ARA-A ARA-B
10 104103102 10 610 5
yA = 0.1663e-3E-06x
yB = 0.1776e-8E-06x
0.0
0.1
0.2
0.3
10 100 1000 100001000001000
Cycles
ARS-A ARS-B
10 104103102 106105
(a) (b) (c) (d)
yA = 0.1566e-1E-05x
yB = 0.2253e-1E-05x
0.0
0.1
0.2
0.3
1 0 1 00 1 00 0 1 00 00 1 00 0
Dissipatedenergy(J/m3)
Cycles
BCO-A BCO-B
10 104103102 106105
yA = 0.1726e-1E-05x
yB= 0.1912e-2E-05x
yC = 0.2157e-1E-05x
yD = 0.2639e-4E-05x
0.0
0.1
0.2
0.3
0.4
10 100 1000 1000010000010000
Cycles
BRO-A
BRO-B
BRO-C
BRO-D
10 104103102 106105
yA = 0.2175e-4E-05x
y B= 0.2378e-1E-05x
0.0
0.1
0.2
0.3
0.4
1 0 1 00 1 00 0 1 00 00 1 00 0
Cycles
BRA-A BRA-B
10 104103102 106105
yA = 0.2516e-2E-05x
yB = 0.2455e-6E-06x
0.0
0.1
0.2
0.3
0.4
10 100 1000 1000010000010000
Cycles
BRS-A BRS-B
10 104103102 106105
(e) (f) (g) (h)
Figure 5 Dissipated energy versus load cycles (repeatition) (a),(e) control beam (aggregate A
and B); (b),(f) rubberized beam (aggregate A and B); (c),(g) rubberized Asphamin beam(aggregate A and B); (d),(h) rubberized Sasobit beam (aggregate A and B)
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yA = 9E+06e-6E-06x
yB = 8E+06e-4E-06x
yC = 8E+06e-2E-06x
E+06
E+07
E+08
10 100 1000 1000010000010000
Stiffness(kPa)
Cycles
ACO-AACO-B
ACO-C106
10 104
108
103102
107
106105
yA = 9E+06e-6E-06x
yD = 9E+06e-6E-06xyC = 8E+06e
-1E-06x
yB = 8E+06e-5E-06x
06
07
08
10 100 1000 1000010000010000
Cycles
ARO-A
ARO-B
ARO-C
ARO-D106
10 104
108
103102
107
106105
yA = 9E+06e-5E-06x
yB = 8E+06e-7E-06x
06
07
08
10 100 1000 100001000001000
Cycles
ARA-A ARA-B
106
10 104
108
103102
107
106105
yA = 1E+07e-3E-06x
yB = 9E+06e-5E-06x
06
07
08
10 100 1000 1000010000010000
Cycles
ARS-A ARS-B
106
10 104
108
103102
107
106105
(a) (b) (c) (d)
yA = 1E+07e-1E-05x
yB = 1E+07e-3E-05x
0E+06
0E+07
0E+08
1 0 1 00 1 00 0 1 00 00 1 00 0
Stiffness(kPa)
Cycles
BCO-A BCO-B
106
10 104
108
103102
107
106105
yA = 8E+06e-7E-06x
yB = 1E+07e-3E-05x
yC = 1E+07e-9E-06x
yD = 2E+07e-3E-05x
6
7
8
10 100 1000 1000010000010000
Cycles
BRO-A
BRO-B
BRO-C
BRO-D106
10 104
108
103102
107
106105
yA = 1E+07e-6E-05x
yB = 2E+07e-2E-05x
6
7
8
10 10 0 1 00 0 1 000 0 1 00 0
Cycles
BRA-A BRA-B
106
10 104
108
103102
107
106105
yA = 1E+07e-2E-05x
yB = 1E+07e-7E-06x
06
07
08
10 100 1000 1000010000010000
Cycles
BRS-A BRS-B
106
10 104
108
103102
107
106105
(e) (f) (g) (h)
Figure 6 Stiffness versus load cycles (repeatition) (a),(e) control beam (aggregate A and B);
(b),(f) rubberized beam (aggregate A and B); (c),(g) rubberized Asphamin beam (aggregate Aand B); (d),(h) rubberized Sasobit beam (aggregate A and B)
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yA = 63.372x + 243145yB = 163.28x - 40713
1000
10000
100000
00000
100 600 1100
Repe
tition(cycle)
Cumula tive disspated energy (J/m3)
Aggregate A Aggregate B
104
103
106
105
(a)
yB = 2121.7x + 3E+06yA = 11.92x + 7E+06
100000
000000
000000
100 600 1100
Lossofstiffness(kPa)
Cumulat ive dissipated energy (J/m3)
Aggregate A Aggregate B
105
106
107
(b)
Figure 7 Cumulative dissipated energy versus (a) repetition and (b) stiffness