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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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    Hossain, M., Swartz, S., and Hoque, E. (1999) Fracture and Tensile Characteris tics of

    Asphalt Rubber Concrete. Journal of Materials in Civil Engineering, Vol. 11, 287-294.

    21.Birgisson, B., Soranakom, C., Napier, J. A. L., and Roque, R. (2004) Microstructure and

    Facture in Asphalt Mixtures Using a Boundary Element Approach. Journalof Materials

    in Civil Engineering, Vol. 16, 116-121.

    22.Shen S. and Carpenter S., (2005) Application of the dissipated energy concept in fatigue

    endurance limit testing, Transportation Research Record: Journal of the Transportation

    Research Board, No. 21929, pp. 165-173

    23.

    Xiao F.P., Amirkhanian S.N., Shen J.N., and Putman B.J. (2008) Influences of Crumb

    Rubber Size and Type on Reclaimed Asphalt Pavement (RAP) Mixtures Construction

    and Building Materials, (In press)

    24.Xiao, F.P. (2006) Development of Fatigue Predictive Models of Rubberized Asphalt

    Concrete (RAC) Containing Reclaimed Asphalt Pavement (RAP) Mixtures. Ph. Ddissertation, Clemson University.

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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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    20

    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