influence of warm mix asphalt additive.pdf

8/10/2019 influence of warm mix asphalt additive.pdf

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INFLUENCE OF WARM MIX ASPHALT ADDITIVE AND DOSAGE RATE ON1

CONSTRUCTION AND PERFORMANCE OF BITUMINOUS PAVEMENTS2

3

Ashley Buss4Graduate Research Assistant (Corresponding Author)5

Iowa State University6

Civil Construction and Environmental Engineering Department7

174 Town Engineering Building, Ames, IA 500118Phone: 563-880-80989

[email protected]

11

Yu Kuang12

Graduate Research Assistant, Iowa State University13


394 Town Engineering Building, Ames, IA 5001115

[email protected]

17

R. Christopher Williams18Professor, Iowa State University19


Phone: 515-294-441921 [email protected]

23

Jason Bausano24

Research Engineer, MeadWestvaco25

5255 Virginia Avenue, North Charleston, SC 2940626

Phone: 843-740-229227

[email protected]

29

Andrew Cascione30Graduate Research Assistant, Iowa State University31



Phone: 520-481-412734

[email protected]

36

Scott Schram37Bituminous Engineer38

Materials Office39

Iowa Department of Transportation40

Ames, IA 5001041

Phone: 515-239-160442

[email protected]

44

45

Submitted on: August 1, 201346

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TEXT: 523748FIGURES and TABLES: 949

TOTAL WORDS: 748750

51

TRB 2014 Annual Meeting Paper revised from original submittal


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Buss, Kuang, Williams, Bausano, Cascione, and Schram 2

ABSTRACT1Warm mix asphalt (WMA) technology is an effective way to reduce emissions and save energy during asphalt2

paving by reducing production temperatures of hot mix asphalt (HMA). As development of WMA additives3

evolve, many owner-agencies do not know the effect WMA dosage rates have on moisture susceptibility, rutting4

resistance, and mixture compaction at different temperatures. The overall influence of time and temperature on5

mixture performance is also important. In this research, two versions of a commonly used WMA additive6

derived from the forest products industry are evaluated for performance during construction and traffic loading.7

Laboratory specimens with different additive contents (0%, 0.5%, and 1.0%) were compacted at different8

temperatures (115C, 130C, and 145C), to evaluate shear capability parameters. Statistical analyses of the9compaction force index (CFI) indicated the stability of asphalt mixtures at various compaction temperatures.10

Evaluation of moisture sensitivity and rutting performance was conducted using the indirect tensile strength test11

and Hamburg wheel tracking test. Improvements were realized at the 0.5% dosage level; therefore, no economic12

benefit is achieved by increasing the dosage level. Findings from the laboratory were tested in the field to13

evaluate the effect of curing time and temperature on WMA compared with HMA. A plant-produced mix14

included HMA and a WMA mixture produced for the same project. The WMA additive used in the plant project15

is the same additive used in the laboratory study. Loose mix was collected in order to evaluate the influence of16

curing time and temperature of a WMA mixture.17

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Keywords: warm mix asphalt, compaction, anti-strip, rutting19

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INTRODUCTION1WMA technology contributes to the construction of sustainable roadways by reducing plant mixing2

temperatures 20C to 55C (35F to 100F) lower than typical HMA ( 1). This not only reduces the emission of3

greenhouse gases that include carbon dioxide (CO2) and sulfur dioxide (SO2), but also lowers fuel consumption4

which saves energy and production costs. During jobsite placement of WMA, the lower temperatures reduce the5

amount of fumes and odors inherent when asphalt is produced and placed at high temperatures. Producing6

asphalt at lower temperatures also reduces binder oxidation, which can increase asphalt pavement cracking7

resistance and service life (1).8

There are three main types of WMA technologies. These include foaming, organic wax additives, and9chemical processes. According to a recent survey (2), Evotherm, Sasobit and Double Barrel Green are10

widely used WMA additives or processes used in the United States. Evotherm 3G is a chemical based additive.11

Evotherm does not contain any water but is in the form of a liquid additive which includes chemical agents12

derived from the forest products industry. Sasobit, an organic wax WMA additive, is a Fisher-Tropsch wax.13

These are created by the treatment of hot coal with steam in the presence of a catalyst. Double barrel green is an14

asphalt foaming system that uses water to produce foamed WMA. All of the commonly used WMA products are15

designed to improve bitumen coating of aggregates, workability, and aggregate-binder adhesion.16

As use of WMA technology grows, owner/agencies are interested in knowing how the WMA additives17

affect the compactability of the asphalt mixture during lay down as well as the moisture susceptibility of the18

asphalt pavement. The addition of WMA additives will improve compaction of the asphalt mixture at lower19

temperatures but effectiveness as a compaction aid over a range of temperatures or dosage rates has not been20

widely studied. Compactability of WMA using variable dosage rates of Sasobit and Rediset were evaluated21

and compared with a 0.6% dosage rate of Evotherm 3G. Evotherm 3G was found to provide the best22compactability (3). Further study of dosage rates for surfactant-based chemical WMA additives is needed.23

Likewise, little research has been conducted on the dosage rate of WMA additives as it relates to the24

moisture sensitivity of an asphalt mixture as well. Traditionally, the moisture susceptibility of WMA has been a25

concern for pavement engineers due to the lower mixing temperatures, addition of water that is necessary for26

some WMA technologies, or the change in asphalt-water affinity caused by chemicals or waxes. In most27

chemical based WMA additives, the chemical additives are designed to improve aggregate-binder adhesion to28

improve the moisture susceptibility of the asphalt pavement. Moisture susceptibility improvement has been29

experimentally proven (4); however, it is not known whether dosage rate that optimizes the compactability of30

the asphalt mixture is the same dosage rate that optimizes its resistance to moisture damage. Moreover, little31

research has been conducted to determine if different dosage rates of a WMA additive have different effects on32

mixture compactability and performance. Curing time and temperature is also a factor that has shown to33

influence the performance of WMA (5-7). Recent studies have shown that the stiffness of asphalt mixtures is34

sensitive to curing temperature and temperature of WMA (5-7). The effect that the curing time and temperature35 has on the Hamburg Wheel Tracking Device (HWTD) results should be evaluated to determine if the reduced36

reheating temperature and/or curing time will cause mixes to fail the 14,000 stripping inflection point37

requirement for mixes with equivalent single axle load (ESAL) designs greater than 3 million ( 8).38

39

OBJECTIVES40This research addresses three main objectives. The first objective is to evaluate the effectiveness of additives A-41

1 and B-1 as compaction aids by using shear force index parameters obtained from the Superpave Gyratory42

Compactor (SGC). The second objective is to study how effective these two types of additives perform as liquid43

anti-strip agents by conducting the following two moisture sensitivity analyses:44

1.

Evaluate the indirect tensile strength of moisture conditioned and unconditioned specimens by45

following AASHTO T-283 Resistance of Compacted HMA to Moisture-Induced Damage.46

2.

Utilize the HWTD to test the mixtures susceptibility to moisture damage. 47

The third objective is to evaluate B1 additives effect oncuring time and temperature on a plant-produced WMA48

and HMA.49

50

MATERIALS51

The two WMA technologies used in this study are generically referred to as: WMA-A1 and WMA-B1. The52

properties of each material are listed in Table 1. The main difference between the materials is their viscosity53

with WMA-A1 having a higher viscosity than WMA-B1.54

55



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TABLE 1WMA additive properties1

WMA-B1 WMA-A1

Physical form Dark amber liquid Dark liquid

Specific gravity at 25C (77F) 0.97 0.999

Conductivity at 25C (77F) (S/cm) 2.2 4.3

Dielectric Constant at 25C (77F) 2 - 10 2 - 10

Viscosity (Pa S)

at 27C (80F) 0.280.56 1.051.90at 38C (100F) 0.150.30 0.470.85

at 49C (120F) 0.080.16 0.200.40

2

TABLE 2 Aggregates and combined gradation for lab produced mix and plant produced mix3

Aggregate % in Mix Source Location Gsb %Abs FAA

1/2 Crushed Eagle City 32 Ames Mine/Martin Marietta 2.581 2.65 47.0

3/4 CL Chip Eagle City 5 Ames Mine/Martin Marietta 2.625 1.92 47.0

1/2 X 4 Quartzite 13 Dell Rapids E. Minnehaha Co/Everi. 2.641 0.14 47.5

3/8 CL Chip Lime Creek 8 Ames Mine/Martin Marietta 2.680 0.44 47.0

Manf. Sand Lime Creek 24 Ames Mine/Martin Marietta 2.659 0.78 45.0

Sand 17 Ames South/Hallett Materials Co. 2.594 1.35 40.0

Hydrated Lime 1 commercially produced

1/2 X 4 Quartzite

1/2 ACC Stone

Manf Sand

Concrete Sand

RAP

9.0%

31%

26%

17%

17%

New Ulm Quartzite Quarry

Greene Limestone- Warnholtz

Greene Limestone- Warnholtz

Greene LS- Cedar Acres Resorts

2RAP09-06 (4.63%)

2.620

2.606

2.705

2.606

2.635

0.72

2.45

1.41

0.76

1.65

45.0

45.0

45.0

38.0

42.4

Job Mix Formula- Combined Gradation

1" 3/4" 1/2" 3/8" #4 #8 #16 #30 #50 #100 #200

Upper Tolerance

100 100 100 91 63 43 18 5.0100 100 95 84 56 38 25 14 5.8 3.4 3.0

100 100 88 77 49 33 10 1.0

Lower Tolerance

Upper Tolerance

100 100 100 94 72 53 24 1.0

100 100 95 87 65 48 32 20 8.8 5.8 4.7

100 100 100 94 72 53 24 1.0

Lower Tolerance

4

The A-1 and B-1 additives were each blended with a PG 64-22 asphalt binder at 0%, 0.5%, and 1.0%5

by weight of binder.6A 12.5 mm (0.5 in.) nominal maximum aggregate size (NMAS) was developed using Superpave7

specifications for the 10 million ESAL level. The optimal binder content that met all Superpave volumetric8

criteria was 5.3%. All samples were compacted in the Superpave Gyratory compactor. The non-shaded portion9

of Table 2 shows the combined gradation for the laboratory mixture as well as each aggregate type, bulk specific10

gravity, percent absorption and fine aggregate angularity. The variable factors for the samples are the two types11

of WMA additive, (A1 and B1) with three different dosage contents (0%, 0.5%, 1%). Therefore, one control12



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and four experimental mixes were developed. The mixes are abbreviated as 0%, A1-0.5%, A1-1%, B1-0.5% and1

B1-1% for subsequent discussion.2

The laboratory study was expanded to include a plant produced (field) mixture in order to identify the3

effects of curing time and temperature on WMA compared with HMA. The field mixture included a control4

HMA mix (no additive) and a WMA (additive B1) mixture. The field mixture is a 12.5 mm (0.5 in.) NMAS and5

a 10 million ESAL level design. The shaded portion of Table 2 shows the combined gradation and aggregate6

properties. The mixture was produced in Floyd County Iowa on a section of US 218 near Charles City. Reduced7

plant temperatures were achieved on this project.8

9

TEST METHODOLOGY10To evaluate the performance of additives A1 and B1 as a compaction aid, the samples were compacted using a11

Superpave Gyratory Compactor at three different mixing/compaction temperatures: 160/145C (320/293F),12

145/130C (293/266F), and 130/115C (266/239F), respectively. The selected design number of gyrations13

(Ndes) was 96 and the maximum number of gyrations (Nmax) was 152. Three replicate samples for each14

mixing/compaction temperature combination were compacted to Nmax.15

The Superpave Gyratory Compactor used in this research was equipped with several advanced16

functions that include measurement of the force and shear capability applied to the specimen. From this data,17

resistive effort curves can be constructed to analyze the stability of the asphalt mixtures at the three different18

mixing/compaction temperature combinations. The resistive effort represents the work done by the SGC per19

unit volume per gyration, assuming the material is perfectly viscous or plastic ( 9). From the resistive effort20

curve, the compaction force index (CFI) and the traffic force index (TFI) are developed to estimate the shear21

force effect from compaction and traffic on asphalt pavements.22The resistive effort curve is separated at 92% of the asphalt mixture maximum theoretical specific23

gravity (Gmm) into a construction effect zone and a traffic effect zone. The CFI refers to the construction side24

and relates to the area under the resistive effort curve below 92% Gmm. For the traffic effect zone, the TFI is25

measured by the area between 92% and 98% Gmmunder the resistive effort curve. In essence, low resistive effort26

is desirable for a contractor to easily compact an asphalt pavement, saving compaction time/effort and reducing27

cost. Therefore, asphalt mixtures with lower CFI values are desired for improved constructability. Inversely,28

higher TFI values are desired for asphalt mixtures as they indicate a greater resistance to stress from traffic29

loading and a reduction in pavement rutting, ultimately extending the pavements service life (10).30

31

Moisture Sensitivity32

In order to evaluate the contribution of the WMA additives as an anti-strip and to determine which type has the33

ability to mitigate moisture sensitivity at the optimum dosage rate, Indirect Tensile Strength (IDT) testing and34

HWTD were conducted. For the laboratory produced mixes, six replicate samples for each test were compacted35to 7%0.5 air voids using the Superpave Gyratory Compactor. Dimensions for AASHTO T-283 cylindrical36

samples are 100 mm (4 in.) diameter and 63.2 2.5 mm (2.5.1in.) in height. Mixing and compaction37

temperatures were 155C (311F) and 145C (293F), respectively. Samples for each test were randomly38

assigned into two subsets of three samples. Moisture conditioning of the samples was conducted according to39

AASTHO T-283.40

One of two subsets was randomly selected to be tested under the dry condition. The dry samples were41

conditioned to a temperature of 25 0.5C (771F) for two hours prior to testing. The moisture-conditioned42

specimens underwent vacuum saturation. The degree of saturation was between 70 and 80 percent for the tested43

specimens and they were each wrapped with a plastic film and then placed in a plastic bag which contained 10 44

0.5 ml of water and sealed. Afterwards, the sealed samples were stored in a freezer at a temperature of -18 3C45

(0 5F). After a minimum of 16 hours, all of samples were removed from the freezer, unwrapped, and46

submerged in a water bath at 60 1C (1402F) with 25mm (1in.) of water above their surface for 24 147

hours. For the last step, before testing is same as control group samples as all of conditioned samples were48 placed in a 25 0.5C (771F) water bath for two hours prior to testing.49

The laboratory evaluation of optimum dosage rate and compactability will ultimately be tested in the field50

where moisture susceptibility requirements are important. Therefore, the influence of curing time and51

temperature was studied for a plant-produced/laboratory-compacted mixture. The curing of WMA field samples52

is currently performed at the reduced compaction temperatures. This portion of the study focuses on how HMA53

and WMA performance results in the HWTD change due to different curing times and temperatures. The intent54

is to determine how long curing should take place and at which temperature in order to have comparable test55



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results in the HWTD between HMA and WMA as well as determine which temperature and time combination1

best simulates the field core HWTD test results. The curing durations chosen were 2 and 4 hours with curing2

temperatures of 120C (248F), 135C (275F), and 150C (302F). A curing time of greater than four hours is3

not generally practical in industry. The cured samples were tested in the HWTD. Only WMA samples were4

cured at reduced temperatures. Table 3 shows the Hamburg pairs that were tested. Each X represents a sample5

that was paired and tested in the HWTD. Cores taken from the field two years after construction were also6

tested.7

8

TABLE 3 Plan of study for investigating curing time and temperature in the HWTD9

Mixes120C (248F) 135C (275F) 150C (302F)

2 Hours 4 Hours 2 Hours 4 Hours 2 Hours 4 Hours

Field Mix HMA --* -- -- -- XXXXXX XXXX

Field Mix WMA XXXXXX XX XXXXXX XXXX XXXXXX XX

*-- indicates no samples were tested for this category10

11

Indirect Tensile Strength12The IDT test was conducted according to AASHTO T-283 to evaluate the mixtures resistance to stripping.13

Moisture damage in asphalt can be influenced by the presence of moisture in the asphalt mixture and will result14

in a loss of strength through the weakening of the bond between the asphalt cement and the aggregate (11). The15

loss of strength due to moisture in the asphalt mixture can be reflected from the tensile strength ratio (TSR). The16

TSR is a numerical index that expresses an HMA pavement s resistance to moisture damage as the ratio of17

retained strength after freeze-thaw conditioning to that of its original strength.18

For testing, the samples were placed between steel loading strips in a hydraulic universal testing19

machine (UTM) within an environmental chamber set at 25C (77F). A load was applied to the specimen at a20

constant rate of 50 mm/min (2 in/min). The maximum compressive load was recorded from which the tensile21

strength can be calculated. The average tensile strength of the moisture conditioned subset group was divided by22

the dry subset group to calculate the TSR.23

24

Hamburg Wheel Track Test25The HWTD is one of several wheel tracking tests used in the United States. It was developed in the 1970s by26

Esso A.G of Hamburg, Germany, (12). The HWTD is used to test an asphalt mixtures susceptibility to moisture27

damage and its resistance to permanent deformation.28

AASHTO T-324 followed for specimen preparation and test setup. Mixing and compaction29

temperatures were 155C (311F) and 145C (293F), respectively. Two cylindrical specimens 150 mm (6 in.)30in diameter and 611 mm (2.40.04 in.) in height were butted into molds and placed under water at 50C31

(122F). Two solid steel wheels with 0.73 MPa (145 psi) contact stress were loaded on the samples and repeated32

20,000 times at 1.1km/h wheel passes for about 6.5 hours or until failure. The test ends automatically when 5033

mm (1.6 in.) rut depth occurs or the preset number of 20,000 wheel cycles is reached (11).34

An important indication moisture damage measured by the HWTD is called the stripping inflection35

point (SIP). The SIP is the number of wheel passes at the intersection of the creep slope and the stripping slope.36

After the number of wheel passes at that point, the moisture damage tends to dominate performance. The37

Colorado Department of Transportation (CDOT) points out that any inflection point below 10,000 wheel passes38

is an indication of moisture susceptibility (13). The HWTD rutting result is defined as the rut depth at 20,00039

wheel passes. Currently, there is no AASHTO specification to limit the maximum rut depth for the HWTD40

testing in the U.S.; however, the Texas Department of Transportation (TxDOT) uses 12.5 mm (0.5 in.) after41

10,000 passes for mixes with a PG 64-22 and the Colorado Department of Transportation (CDOT) suggested42

that a rut depth of 10 mm (0.4 in.) after 20,000 passes as the criterion ( 14).4344

TEST RESULTS AND DISCUSSION45Test results were evaluated based upon how the additive types, A1 and B1, contribute to both the stability of the46

asphalt mixtures and the results for IDT and HWTD, while taking into consideration the various additive dosage47

levels as well as the mixing and compaction temperature combinations. Statistical analysis was conducted using48

JMP statistical software (15).49



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Figure 1 displays the average values of the compaction force index (CFI) shown with 95% confidence1

intervals. The error bars in Figure 1 and Figure 2 show little difference between the additive dosage levels for2

both CFI and TFI. ANOVA testing confirmed there are no statistically significant differences in additive type3

and no interaction effects for dosage rate and temperature among additive types A1/B1 at an =0.05 level.4

However, for A1 and B1, there are the same significant differences in temperature when Tukey honestly5

significant difference (HSD) multiple comparison testing was performed. The compaction temperature of 145C6

(293F) is not significantly different with 130C (266F) and 115C (239F), but 115C (239F) is significantly7

different with 130C (266F). The statistical difference between 115C (239F) and 130C (266F) indicates8

the compaction temperature of 115C (239F) may be too low for this mixture and better compaction is9achieved at 130C (266F). The CFI at 115C (239F) also has the highest average for each mixture tested. The10

largest average reduction in the CFI values occurred for B1-1% followed by A1-0.5% but variability in the CFI11

parameter does not allow for statistical conclusions at an -level of 0.05. An ANOVA analysis of CFI data12

confirmed that there are no statistically significant differences in the variable dosage levels and no interaction13

effects between additive type and compaction temperature exist. The ANOVA analysis suggests some statistical14

differences between compaction temperatures but no overall trend applies to all dosage rates and temperatures.15

These differences can be observed by the overlapping of confidence intervals in Figure 1.16

17

18FIGURE 1Effects of different additives and dosage levels on the CFI.19

20

Figure 2 shows the TFI values with error bars that represent 95% confidence interval. The average TFI21

for the control shows the largest sensitivity to temperature, on average. The ANOVA analysis showed no22

significant differences in additive type or dosage level and no significant interactions between factors.23

A comparison between A1-0.5% and B1-0.5%, showed no statistically significant differences in24

additive type and no interactions between additive and temperature. The highest mean TFI was measured at25

115C (239F) compaction temperature and is statistically different from the mean TFI at 130C (266F). On26

average, the control samples had a higher TFI at the lower temperatures of 130C (266F) and 115C (239F).27

Comparing between A1-1% and B1-1% TFI, there are no statistically significant differences in the28

factors of additive type, temperature and the interaction between additive and temperature.29

30

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

CFI

145 C

130 C

115 C

Control B1- 0.5% B1-1% A1-0.5% A1-1%



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1FIGURE 2Effects of different additives and dosage levels on the TFI.2

3

The TSR and indirect strength values with 95% confidence intervals are shown in Figure 3. The TSR4

ratio was calculated by using the conditioned mix strength with an additive as the numerator and the5 unconditioned mix strength without additive as the denominator. The denominator of the TSR ratio is always the6

dry strength of the 0% additive content mix. By keeping a consistent denominator, the data does not add a7

confounding factor. This method accurately reflects the difference in TSR values.8

All TSR values meet the required 80% minimum. The ANOVA analysis shows no statistical difference9

between additive type and content; however, on average the 0.5% dosage rate has the highest average TSR10

values.11

12

13FIGURE 3Iowa DOT TSR values for the control and treatment conditions.14

15

The mixes were evaluated using the HWTD test using laboratory compacted specimens which contain16

two types of additives (A1, B1) and three content level (0%, 0.5% and 1%) organized as a full factorial design.17

Three replicates were prepared at each combination of factor levels, which required a total of 36 specimens.18

0.0

500.0

1000.0

1500.0

2000.02500.0

3000.0

3500.0

4000.0

4500.0

5000.0

TFI

145 C

130 C

115 C

Control B1- 0.5% B1-1% A1-0.5% A1-1%

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0

200

400

600

800

1000

1200

1400

IowaDOTTSR

IndirectTensileStrength,

kPa

IDT Ratio

IDT Strength



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Mixing and compaction temperatures were 155C (311F) and 145C (293F), respectively. The laboratory mix1

samples were cured for 2 hours at the compaction temperature.2

According to the literature review, it is not inevitable that HWTD results will show all three3

characteristic variables: creep slope, stripping slope and SIP. For the result of the HWTD test, no stripping4

deformation occurred. Therefore, only the creep slope and the maximum rut depth at 20,000 passes were used to5

analyze the data.6

Based on the data comparison, adding either additives, A1 or B1, can reduce the rutting depth when7

mixed and compacted at the same temperature. The mix types with the WMA additive (A1 or B1) present better8

rutting resistance with a reduced creep slope as compared to the HMA samples. The A1-0.5% and A1-1.0%9performed almost same as the B1-0.5% and B1-1%, respectively.10

With respect to the creep slope, the ANOVA analysis indicates statistical differences in additive type11

and dosage rate. The B1 additive has the lowest mean creep slope and is statistically different than A1.12

Moreover, the 0%-control specimens show the highest mean creep slope and is significantly different from other13

mixes containing WMA additives at all dosage rates (0.5%, 1.0%), as shown in Figure 4.14

Figure 4 shows the rut depth at 20,000 passes. By examining the rut depths, a comparison of dosage15

level demonstrates the impact the additives have on rutting performance in the asphalt mixes. The mixes with16

the WMA additive exhibited statistically lower amounts of rutting than the mix with no WMA additive. There17

were no differences in rutting performance between the 0.5% and 1.0% dosage rate or between the A1 and B118

additives. Therefore, adding at least 0.5% of the A1 or B1 additives will improve an asphalt mixtures resistance19

to rutting.20

21

22FIGURE 4Average rut depth at 20,000 passes and creep slope for control and treatment samples.23

24

The curing study was performed on plant produced mixes using the HWTD to investigate the impact of25

time and temperature on the SIP results. The curing times were either 2 or 4 hours and the temperatures were26

120C (248F), 135C (275F) and 150C (302F). All of the mixes included in this study used the same WMA27additive. The HWTD sample dimensions were 150mm (6 in.) diameter and 60.3 mm (2.374 in.) in height.28

Cores were sawn to the test sample height.29

The HWTD test results for the cured-lab compacted samples were compared against the cores taken30

from the roadway. Figure 5 shows the comparisons for all samples including WMA and HMA. The dash lines31

represent only 2 hours of curing. The WMA and HMA cores performed well with no evidence of stripping. The32

HMA mixes are denoted in the graph as red or orange lines. The WMA is shown in blue or green lines. The33

WMA samples with 2 hours of curing at 120C (248F) and 135C (275F) were the poorest performing mixes.34

0.0E+00

2.0E-05

4.0E-05

6.0E-05

8.0E-05

1.0E-04

1.2E-04

1.4E-04

1.6E-04

1.8E-04

0

1

2

3

4

5

6

0% A1-0.5% A1-1% B1-0.5% B1-1%

Cr

eepSlope(mm/pass)

RutDept

hat20000Passes(mm)

Rutting Depth

Creep Slope



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Buss, Kuang, Williams, Bausano, Cascione, and Schram

10

HMA and WMA samples cured for 2 hours at 150C (302F) displayed similar test results. Increased1

conditioning time of 4 hours also increased performance in the HWTD. The HMA and WMA both showed2

similar rutting depths when cured at 4 hours at 150C (302F) and this was similar with the rutting depths of the3

tested cores. The data for the WMA samples cured for four hours at 150C (302F) showed some noise in the4

data but there was not significant rutting or signs of stripping. The SIP values are shown in Figure 6. The HMA5

samples cured for 2 hours at 150C (302F) showed similar values to the WMA samples cured for 4 hours at6

120C (248F). Samples conditioned for the two hour curing time at 120C (248F) and 135C (275F) showed7

low stripping inflection points and would not pass the 14,000 SIP requirement for this 10 million ESAL mix but8longer curing times or higher temperatures would increase the SIP values so that the required minimum SIP9

would be met.10

11

12

FIGURE 5Hamburg results comparing curing temperature and time.13

14

15FIGURE 6 SIP comparing HMA/WMA, curing time and temperature.16

17

-16.0

-14.0

-12.0

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

0 5,000 10,000 15,000 20,000

RutDepth

,mm.

Pass Number

WMA Core HMA Core WMA 2 hrs 120CWMA 2 hrs 135C WMA 2 hrs 150C HMA 2 hrs 150WMA 4hrs 120C WMA 4 hrs 135C WMA 4 hrs 150CHMA 4 hrs 150C

0

2000

4000

6000

8000

10000

12000

14000

16000

1800020000

NumberofPasses



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Buss, Kuang, Williams, Bausano, Cascione, and Schram

12

REFERENCES11.

D'Angelo, J., E. Harm, J. Bartoszek, G. Baumgardner, M. Corrigan, J. Cowsert, T. Harman, M.2

Jamshidi, W. Jones, D. Newcomb, B. Prowell, R. Sines, B. Yeaton, Warm-Mix Asphalt: European3

Practice, Report No.FHWA-PL-08-007, U.S. Department of Transportation, February 2008.4

2. Mogawer, W. A., A. Austerman, E. Kassem, and E. Masad. Moisture Damage Characteristics of5

Warm Mix Asphalt Mixtures. Journal of theAssociation of Asphalt Paving Technologists, Vol 80,6

2011, pp.368-402.7

3.

Bennert, T., G. Reinke, W. Mogawer, and K. Mooney. Assessment of Workability and Compactability8of Warm-Mix Asphalt. In Transportation Research Record: Journal of the Transportation Research9

Board, No 2180, Transportation Research Board of the National Academies, Washington, D.C., 2010,10

pp. 36-47.11

4.

Mogawer, W.S., A.J. Austerman and H.U. Bahia. Evaluating the Effect of Warm-Mix Asphalt12

Technologies on Moisture Characteristics of Asphalt Binders and Mixtures. In Transportation13

Research Record: Journal of the Transportation Research Board, No 2209, Transportation Research14

Board of the National Academies, Washington, D.C., 2011, pp. 52-60.15

5.

Bennert, T., A. Maher, and R. Sauber. Influence of Production Temperature and Aggregate Moisture16

Content on the Initial Performance of Warm-Mix Asphalt. In Transportation Research Record: Journal17

of the Transportation Research Board, No 2208, Transportation Research Board of the National18

Academies, Washington, D.C., 2011, pp. 97-107.19

6. Yin, F., L., Garcia Cucalon, A. Epps Martin, E. Arambula, A. Chowdhury, E.S. Park. Laboratory20

conditioning protocols for warm-mix asphalt. Journal of the Association of Asphalt Paving21Technologists, Vol 82, 2013, pp.115-133.22

7. Al-Qadi, I.L., Z. Leng , J. Baek, H. Wang, M. Doyen, and S.L. Gillen. Short-Term Performance of23

Plant-Mixes Warm Stone Mastic Asphalt Laboratory Testing and Field Evaluation. In Transportation24

Research Record: Journal of the Transportation Research Board, No 2306, Transportation Research25

Board of the National Academies, Washington, D.C., 2012, pp. 86-94.26

8.

Iowa Department of Transportation. Standard Specifications with GS-12002 Revisions. Section 2303:27

Flexible Pavements. Last updated 03/18/2013. Retrieved from Iowa Department of Transportation28

Electronic Reference Library on 7/29/2013 from:29

http://www.iowadot.gov/erl/current/GS/content/2303.pdf30

9.

Faheem, A., and H. Bahia. Estimating Results of a Proposed Simple Performance Test for Hot-Mix31

Asphalt from Superpave Gyratory Compactor Results. In Transportation Research Record: Journal of32

the Transportation Research Board, No 1929, Transportation Research Board of the National33

Academies, Washington, D.C., 2005, pp.104- 113.34 10. Abed, D. A. Enhanced Aggregate-Asphalt Adhesion and Stability of Local Hot Mix Asphalt.35

Engineering & Technology Journal. Vol. 29 No.10, 2011 pp. 2044-pp. 2059.36

11.

Roberts, F. E., P. Kandhal, D. Lee, and T. Kennedy. Hot Mix Asphalt Materials, Mixture Design, and37

Construction. National Asphalt Pavememnt Association Research and Education Foundation,38

Lanham, Maryland, 1996.39

12.

Aschenbrener, T. Comparison of Several Moisture Susceptibility Tests to Pavements of Known Field40

Performance. Journal of the Association of Asphalt Paving Technologists, Vol 64, 1995, pp.163-41

pp.208.42

13.

Aschenbrener, T., R.L. Terrel, R.A. Zamora. Comparison of the Hamburg Wheel-Tracking Device and43

the Environmental Conditioning System to Pavements of Known Stripping Performance. Publication44

No. CDOT-DTD-R-94-1. Colorado Department of Transportation, 1994.45

14.

Lu, Q. Investigation of Conditions for Moisture Damage in Asphalt Concrete and Appropriate46

Laboratory Test Methods.Ph. D. Dissertation. University of California, Berkeley, 2005.47

15.

SAS Institute Inc., JMP, Version 9.0., Cary, NC, 1989-2009.48

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