FHWA-WFL/TD-09-002 January 2009

Federal Highway Administration

U.S. Department of Transportation
Technical Report Documentation Page

1. Report No.

 FHWA-WFL/TD-09-002

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Placement of Warm Mix Asphalt on the East Entrance Road of 

Yellowstone National Park

5. Report Date

 January 2009

6. Performing Organization Code

7. Author(s)

Brad Neitzke and Bruce Wasill

8. Performing Organization Report No.

9. Performing Organization Name and Address

 HK Contractors, Inc.

 P.O. Box 51450

 Idaho Falls, ID 83405

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

 Federal Highway Administration

 Western Federal Lands Highway Division

 610 East 5th St.

 Vancouver, WA 98661

 National Park Service

 Yellowstone National Park

 P.O. Box 168 

 Yellowstone National Park, WY 82190-0168

13. Type of Report and Period Covered

Final Report 2009

14. Sponsoring Agency Code

 HFL-17

15. Supplementary Notes

 This technology deployment was funded under the FHWA Federal Lands Highway Coordinated Technology 

Implementation Program (CTIP).

16. Abstract

In an eff ort to deploy the warm mix asphalt (WMA) technology to Federal Lands Highway (FLH) and cooperating 

agencies, a Coordinated Technology Implementation Program (CTIP) proposal was approved by agency representatives. 

This CTIP project allowed FLH to take the lead in working with our client agency and contractors to evaluate the viability of 

warm mix technology as a standard construction practice. The demonstration evaluated two diff erent WMA technologies 

(Advera and Sasobit) on a construction project on the East Entrance Road of Yellowstone National Park. The mixtures were 

placed in August/September 2007.

This report documents the results and summarizes the fi ndings of this technology deployment.

17. Key Words

WARM MIX ASPHALT (WMA), ADVERA, SASOBIT, 

YELLOWSTONE NATIONAL PARK, EAST ENTRANCE ROAD

18. Distribution Statement

 No restriction. This document is available to the 

 public from the sponsoring agency at the website 

 http://www.wfl .fhwa.dot.gov/td/.

19. Security Classif. (of this report)

Unclassifi ed

20. Security Classif. (of this page)

Unclassifi ed

21. No. of Pages

16

22. Price

$0.00

 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
Placement of Warm 

Mix Asphalt on the 

East Entrance Road of 

Yellowstone National 

Park

Report Number: FHWA-WFL/TD-09-002

Technology Deployment Program

Western Federal Lands Highway Division

Federal Highway Administration

610 East 5th St.

Vancouver, WA 98661

Technology Deployment Report
SI* (MODERN METRIC) CONVERSION FACTORS

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km

AREA

in2 square inches 645.2 square millimeters mm2 

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2 

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

VOLUME

fl oz fl uid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3

yd3 cubic yards 0.765 cubic meters m3

NOTE: volumes greater than 1000 L shall be shown in m3

MASS

oz ounces 28.35 grams g 

lb pounds 0.454 kilograms kg 

T short tons (2000 lb) 0.907 megagrams (or “metric ton”) Mg (or “t”)

TEMPERATURE (exact degrees)

°F Fahrenheit 5 (F-32)/9 Celsius °C

or (F-32)/1.8

ILLUMINATION 

fc foot-candles 10.76 lux lx 

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa

APPROXIMATE CONVERSIONS FROM SI UNITS

Symbol When You Know Multiply By To Find Symbol

LENGTH

mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2

 square millimeters 0.0016 square inches in2

m2 square meters 10.764 square feet ft2

m2 square meters 1.195 square yards yd2

ha hectares 2.47 acres ac 

km2

 square kilometers 0.386 square miles mi2 

VOLUME

mL milliliters 0.034 fl uid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3

m3 cubic meters 1.307 cubic yards yd3

MASS

g grams 0.035 ounces oz 

kg kilograms 2.202 pounds lb 

Mg (or “t”) megagrams (or “metric ton”) 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees)

°C Celsius 1.8C+32 Fahrenheit °F

ILLUMINATION

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl 

FORCE and PRESSURE or STRESS

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. 

(Revised March 2003)
Table of Contents

INTRODUCTION ......................................................................................................... 4

ENVIRONMENTAL DETAILS .......................................................................................... 4

PAVEMENT STRUCTURE ............................................................................................... 5

CONSTRUCTION PROCESS AND EQUIPMENT ...................................................................... 6

PAVING OPERATIONS ................................................................................................. 6

Control Mixture ............................................................................................................. 6

Advera Mixture .............................................................................................................. 7

Sasobit Mixture ............................................................................................................. 8

INFRARED IMAGING ................................................................................................... 9

MIX DESIGN AND MATERIAL PROPERTIES ..................................................................... 10

Mixture Properties ...................................................................................................... 10

Binder Properties ........................................................................................................ 11

PRODUCTION MIXTURE TESTING ................................................................................. 11

RECOVERED ASPHALT BINDER TESTING ........................................................................ 14

ADDITIONAL TESTING ............................................................................................... 14

FUEL REDUCTIONS .................................................................................................. 14

SUMMARY OF FINDINGS ........................................................................................... 15

CONCLUSIONS AND RECOMMENDATIONS ....................................................................... 15

ACKNOWLEDGEMENTS .............................................................................................. 16
INTRODUCTION

In an eff ort to deploy the warm mix 

asphalt (WMA) technology to Federal Lands 

Highway (FLH) and cooperating agencies, 

a Coordinated Technology Implementation 

Program (CTIP) proposal was approved by agency 

representatives. This CTIP project allowed FLH to 

take the lead in working with our client agency 

and contractors to evaluate the viability of warm 

mix technology as a standard construction 

practice. The demonstration evaluated two 

diff erent WMA technologies (Advera and Sasobit) 

on a construction project on the East Entrance 

Road of Yellowstone National Park. The mixtures 

were placed in August/September 2007.

The goals of this WMA project were to:

• Document the use, performance, and 

construction processes associated 

with WMA.

• Enhance FLH laboratory testing 

experience and testing methodologies 

necessary for the construction of 

WMA pavements.

• Document the economic impacts/

benefi ts of WMA.

• Develop understanding for inspection 

and monitoring processes needed for 

quality placement and compaction of 

WMA.

• Place a large enough 

quantity of material 

to be able to 

fully understand 

c o n s t r u c t i o n 

processes, issues, 

and possible fi eld 

adjustments.

The implementation of 

warm mix technology 

substantially reduces the 

temperatures at which asphalt 

mixtures are produced. This 

product has environmental, 

economic, and manufacturing 

benefi ts that would be realized by the agencies 

implementing this technology and the 

contracting community. Since the performance 

of this material is stated to be equal to or better 

than hot mix asphalt, there would be no concerns 

of using a product that has inferior performance 

characteristics.

The deliverables from this technology 

deployment eff ort are increased knowledge 

and experience in the construction of warm 

mix asphalt. This includes knowledge in the 

construction, manufacturing, placement, testing, 

and design of warm mix asphalt. By placing 

this material on a FLH construction project, 

FLH and client agencies are exposed to the use, 

construction practices, limitations, and overall 

benefi ts of using this product. The contracting 

community becomes more familiar with the 

technology and the means to provide this 

material to a construction project.

ENVIRONMENTAL DETAILS

The project was to reconstruct a portion of the 

East Entrance Road of Yellowstone National Park. 

The beginning of the project area was at Sylvan 

Pass and from there progressed to the east to the 

boundary of the national park with the Shoshone 

National Forest. The project was 6.93 miles 

4

Gran d

Loop Road

Yell owstone River

East E ntrance Road

Yellowstone National Park

Shoshone National Forest

End of Project

Beginning of Project

Yellowstone Lake

85 km to 

Cody, WY Route 13

N

Figure 1 ~ Map of project.
existing in-situ pavement structure. This material 

was placed and compacted to a depth of 

6 inches (150 mm). The subsequent layer was a 

crushed aggregate base that was treated with 1% 

emulsifi ed asphalt. This material was compacted 

to a fi nished depth of 8 inches (200 mm) and 

provided an excellent paving platform for the 

asphalt concrete pavement. The fi nal layer was 

4 inches (100 mm) of asphalt concrete pavement 

placed in two equal lifts. The plan quantity for the 

asphalt concrete was 31,300 tons (28,430 metric 

tons).

It was desired to have an approximately 

equal amount of asphalt concrete placed by 

the three diff erent methodologies: control 

(conventional hot mix), Advera WMA, and 

Sasobit WMA. A contract modifi cation was 

initiated to provide for minor hot plant 

modifi cations to allow for introduction of the 

additives into the mixture. This modifi cation 

covered the cost for delivery and support activities 

for the placement of the WMA mixtures. As part 

of the contract negotiations, it was desired that 

the change to the WMA mixtures would have 

minimal eff ect on the production. In other words, 

full and continuous production of the mixtures 

was desired, although not necessarily at the same 

production rate. Based on this criterion, the fi nal 

placed quantities were not equal but provided 

for an equal number of production days for the 

two warm asphalt mixtures. 

(11.15 km) long and ranged in elevation from 

8,500 feet (2,591 m) at the pass to 6,950 feet 

(2,118 m) at the east boundary. The project has a 

steady downhill grade that reaches a maximum 

grade of 7% in the most severe case. Figure 1 

provides the project location.

The climate in the project area is moderately 

dry with cool summers and cold winters. During 

the summertime average high temperatures 

are in the 70s (25 °C), and nights are cool with 

temperatures in the upper 30s to low 40s (5 to 

10 °C). Winter temperatures often hover near zero 

(-20 °C) throughout the day, and nighttime lows 

are subzero. Yellowstone typically experiences 

periods of bitter cold weather. Annual snowfall 

averages near 150 inches (380 cm) in most of 

the park; however, 200 to 400 inches (5 to 10 m) 

have been recorded at higher elevations such as 

Sylvan Pass.

PAVEMENT STRUCTURE

The pavement structure was determined 

utilizing the DARWin pavement structure design 

program. The traffi c loadings for a 20-year design 

life were estimated at 1,000,000 equivalent single 

axle loads (ESALs).

The pavement structure consisted of three 

layers. The subbase was constructed using 

recycled aggregates and pavement from the 

5

Figure 2 ~ Control mix placement.

Figure 3 ~ Depositing control mix in windrow.
The roller pattern was established during the 

construction of a control strip. The specifi cations 

required that a control strip be placed and 

evaluated prior to full scale production. The 

evaluation of the control strip ensured that 

the plant was producing mixture within the 

tolerances of the mix design and the roller 

pattern used provided suffi cient density. Upon 

completion and evaluation of the control strip, 

it was determined that the established roller 

pattern presented above would provide the 

necessary compactive eff ort. The control strip 

was placed and evaluated on August 21, 2007.

PAVING OPERATIONS

Control Mixture

Production paving of the control mix began 

on August 22, 2007 and continued for four 

days. The plant was located in Cody, Wyoming 

approximately 53 miles (85 km) from the project. 

The distance provided for a 90 minute one-way 

haul primarily uphill. 

In general, mixture laydown temperatures 

ranged from 300 to 325 °F (149 to 160 °C). Paving 

weather was favorable for this time of year in 

Yellowstone National Park therefore only minimal 

heat loss occurred during the transportation 

of the mix. Morning temperatures were in 

the mid 40s (7 °C) with daytime temperatures 

CONSTRUCTION PROCESS AND EQUIPMENT

The contractor utilized the same equipment 

and construction process for the placement of 

the three diff erent mixtures. Additionally all three 

of the mixtures were placed and compacted in an 

identical manner. Paving was accomplished by 

belly dumps depositing mixture in a windrow and 

a pick-up machine depositing the mix into the 

paver hopper. This is the conventional method 

that is typically done throughout this region. The 

paver was a Caterpillar model AP-1055B that used 

a sonic ski and slope control device to provide 

grade and slope control. The pick-up machine 

was a Barber Green BG-650.

Compaction was accomplished using two 

Ingersoll Rand vibratory steel drum rollers, model 

number DD-130HF, working in echelon as the 

breakdown rollers. Seven vibratory passes (a pass 

is defi ned as one trip of a roller in one direction) 

were needed to compact the mixture above the 

minimum density specifi cation of 91 percent 

of maximum theoretical density. Finish rolling 

was provided by three passes of an Ingersoll 

Rand single steel wheel roller model SD-77DA. 

Based on nuclear gage readings, a small increase 

in density was provided by the fi nish rolling; 

however, the majority of the compaction eff ort 

was accomplished during breakdown rolling. 

No intermediate rolling was needed or provided 

during construction.

6

Figure 5 ~ Control mix laydown.

Figure 4 ~ Control mix paving operation.
reaching highs in the upper 70s (25 °C). The days 

were primarily sunny with some scattered clouds 

in the afternoon. 

During these 4 days of paving, approximately 

9,200 tons (8,350 metric tons) of the control 

mixture were placed. Aside from a few minor 

mechanical breakdown issues, the paving 

operations were smooth and uneventful.

Typical paving operations for the control mix 

are shown in Figures 2, 3, 4, and 5.

Advera Mixture

Placement of the Advera WMA began on 

August 26, 2007 and continued for four days. 

The Advera was added at a rate of 0.3% by 

weight of mix and was introduced at the plant 

via a port located just below the asphalt binder 

port (Figure 6). This allowed the zeolite powder 

additive to be blown into the binder during mix 

production thereby preventing any additive from 

escaping through the exhaust.

The placement of the mixture followed the 

same process as for the control mixture, as 

shown in Figures 7 & 8. The roller pattern was the 

same as the one that was established during the 

construction of the control strip.

The weather for the paving of the Advera 

WMA was similar to that for the control mix. The 

mornings were cool but clear, and the days were 

primarily sunny with some build up of clouds in 

the afternoon. For this time of year in Yellowstone 

National Park, the paving conditions were near 

ideal.

The initial target laydown temperature for the 

Advera WMA was 275 °F (135 °C). The laydown 

temperatures for the fi rst day of paving ranged 

between 265 to 275 °F (130 to 135 °C). Because 

of the success in laydown and compaction of 

this mix, it was determined to lower the mix 

temperature in subsequent days. Eventually the 

mix was placed at a temperature of 250°F (121°C).

7

Figure 6 ~ Injection ports at the end of the drum: top port — 

asphalt binder, bottom port — warm mix additive.

Figure 7 ~ Advera WMA deposited in windrow.

Figure 8 ~ Advera laydown operation.
Compared to the control mix, the major 

diff erence was the lack of visible smoke and 

fumes. Although no worker exposure testing 

was conducted during these trials, anecdotal 

information from the paving crew suggested 

better working conditions with the Advera WMA.

A total of 9,650 tons (8,750 metric tons) of 

Advera WMA were placed.

Sasobit Mixture

Placement of the Sasobit WMA (Figures 

10 & 11) began on August 30, 2007 and was 

completed on September 7, 2007. There were 

four days of production paving during this 

interval with time off for the Labor Day holiday 

as well as one day of heavy rain on September 6. 

The weather for paving was similar to that of the 

control mix and Advera WMA; however, one of 

the days was cut short due to an afternoon rain 

storm.

The Sasobit wax prills were added to the 

mixture using the same drum port that the Advera 

product used with the exception of the port size. 

A reduction collar was needed to change the port 

connection from a 4-inch line used for the Advera 

to a 2-inch line for the Sasobit. This was needed 

due to the addition rate for the Sasobit being 

much lower than the rate for Advera. To produce 

the Sasobit WMA, Sasobit was added at a rate of 

1.5% by weight of binder. 

The biggest issue in regard to the laydown 

temperature was obtaining consistency. During 

the production of the Advera WMA, it was 

diffi cult to maintain a constant production 

temperature. The cause of this was not defi nitively 

determined. Needing higher temperatures due 

to moisture in the aggregate or the burner not 

being properly adjusted to function properly at 

lower temperatures may have been contributing 

factors.

The workers noticed no handling diff erences 

using the Advera WMA compared to the 

control mix. The mixture was still easy to rake 

and manipulate when required and handled 

similarly to hot mix even at the lowest placement 

temperatures. The roller operators stated that the 

mix did not seem as tender as the hot mix and 

compaction was easily obtainable. 

8

Figure 9 ~ Sasobit deposited in windrow.

Figure 10 ~ Sasobit laydown operation. Figure 11 ~ Sasobit laydown operation.
and fumes. No worker exposure testing was 

conducted as part of this evaluation.

A total of 8,210 tons (7,450 metric tons) of 

Sasobit WMA was placed.

INFRARED IMAGING

During the laydown operations, thermal 

images were taken of the three mixtures (Figures 

12 & 13). These images can be used to detect 

thermal segregation in the windrow or in the 

placed mat. 

From a review of these images, both of 

the warm mixes exhibited a more uniform 

temperature in the placed mat than the control 

hot mix. This is potentially an advantage of using 

these particular warm mix additives because they 

provided a more uniform product upon remixing 

and laydown.

Manufacturing conditions at the plant were 

similar to those of the Advera WMA. The plant 

initially established a target temperature of 

275 °F (135 °C). After the fi rst round of trucks, 

which provided approximately 600 tons 

(545 metric tons), the temperature was reduced 

to 250 °F (121 °C). Similar to the Advera WMA, 

the production temperatures fl uctuated 

between 250 and 275 °F (121 and 135 °C), and 

it was diffi cult to maintain a consistent lower 

production temperature.

The workers noticed no handling diff erences 

between the Sasobit WMA and the control mix, 

even at temperatures as low as 230 °F (110 °C). 

The mix could be easily raked and leveled and 

had the same handling characteristics as hot mix 

even in the most diffi cult circumstances such 

as barrier wall tapers. The roller operator noted 

that density was easily achieved and felt that the 

mixture behaved similar to the Advera WMA. The 

roller pattern was the same as that used for the 

other two mixtures.

Again the major diff erence from a worker 

perspective was the reduced visible smoke 

9

Control Mix Advera Mix Sasobit Mix

Control Mix Advera Mix Sasobit Mix

Figure 13 ~ Thermal images of mixture immediately behind the paver.

Figure 12 ~ Thermal images of mixes in the windrow.
air voids and a slightly reduced amount (12.4%) 

of voids in mineral aggregate (VMA).

In addition, 75-gyration Superpave specimens 

were manufactured using the two warm mix 

additives. The mix design procedure was 

modifi ed to accommodate the lower mixing 

and compaction temperatures. In order to 

manufacture these specimens, the aggregate 

was heated to a temperature of 275 °F (135 °C). 

Asphalt binder along with the warm mix additive 

was then added and properly mixed. The 

mixture was then short-term aged according to 

AASHTO R 30 but at a reduced temperature. The 

specimens were then compacted. A comparison 

of the mix design data is shown in Table 3. 

From the comparison of the Superpave 

gyratory data, the warm mix additives provide 

a compaction benefi t even at the reduced 

temperatures. This data indicates that some type 

of modifi ed procedure will be needed in order to 

design mixtures using warm mix additives of this 

type. If the method is not modifi ed, there would 

be a reduction in asphalt content for mixtures 

that use these types of additives which could 

lead to pavement durability issues.

MIX DESIGN AND MATERIAL PROPERTIES

Mixture Properties

The contract specifi ed that a Hveem mix 

design be performed by the contractor and 

verifi ed by the Government. The contractor had 

the responsibility of selecting the aggregate 

gradation and proper asphalt content to ensure 

compliance with the mix design criteria. As part 

of the mix design process, it was determined that 

the aggregate source was moisture sensitive and 

required treatment to meet the retained strength 

requirement. The contract required that hydrated 

lime, added at a rate of 1.0%, be used as the antistrip additive. The specifi cations for the approved 

gradation and mix design of the control mixture 

are shown in Tables 1 & 2. The two WMA mixtures 

were designed using the same gradation target 

values. 

After completion of the Hveem mix design, 

75-gyration Superpave specimens were 

manufactured and analyzed. Based on the data 

obtained from the Superpave specimens, the 

asphalt content (AC) would have been reduced 

to 5.2% by weight of mix. This would yield 4.0% 

10

Sieve Size Target Value

1” (25 mm) 100

3⁄4” (19 mm) 99

1⁄2” (12.5 mm) 85

3/8” (9.5 mm) 71

#4 (4.75 mm) 46

#8 (2.36 mm) 30

#40 (425 μm) 12

#200 (75 μm) 6.0

Table 1 ~ Control mix gradation.

Asphalt Content by Weight of Mix 5.3%

Air Voids 4.0%

Voids in Mineral Aggregate 12.6%

Stabilometer Value 36

Dust / Asphalt Ratio 1.1

Immersion-Compression (1% lime added) 91.0%

Table 2 ~ Hveem control mix design.

Control Mix Advera Mix Sasobit Mix

5.2% AC by Mix 5.2% AC by Mix 5.2% AC by Mix

4.0% Air voids 3.4% Air voids 3.2% Air voids

12.4% VMA 12.1% VMA 12.0% VMA

Table 3 ~ 75-gyration Superpave mix design comparison.

Property No Additive With 1.5% 

Sasobit

Rotational Viscosity 0.535 Pa•s 0.480 Pa•s

Mass Change -0.387% -0.364%

DSR, Original 1.316 kPa 2.468 kPa

DSR RTFO 2.551 kPa 4.719 kPa

DSR PAV 1,414 kPa 1,917 kPa

BBR, Stiff ness, S 265 MPa 287 MPa

BBR, Slope, m-value 0.318 0.275

Table 4 ~ Comparison of binder characteristics.
windrow. One sample was taken at random for 

every 770 tons (700 metric tons). These samples 

were shipped from the project to the Western 

Federal Lands Highway Division (WFLHD) 

laboratory in Vancouver, Washington for testing. 

Based on the produced quantities for the project, 

12 mixture samples were obtained for the control 

mixture, 12 samples were obtained from the 

Advera mixture, and 10 samples were obtained 

from the Sasobit mixture. The sand equivalent 

(SE), percent fracture, and core density values 

were determined from samples obtained by the 

contractor as part of the quality control/quality 

assurance process established in the contract.

Once these samples arrived at the laboratory 

in Vancouver, they were tested for asphalt 

content and gradation. Additionally specimens 

were fabricated for Superpave volumetric 

testing. Table 5 summarizes the conventional mix 

Binder Properties

The asphalt binder 

for the project was a 

PG 58-34 as specifi ed 

in AASHTO M 320. This 

binder met the 98% 

reliability as stated in 

the LTPPBind asphalt 

binder selection program 

for this extremely cold 

environment. The binder 

supplied to the project 

met the requirements for 

the specifi ed grade.

It had been reported 

that the addition of Sasobit 

can have an eff ect on the binder properties. For 

this project, the asphalt binder supplied for the 

mix design was tested with and without the 

additive to determine the extent of stiff ening, 

if any, on the binder. The results of the test are 

shown in Table 4. 

From the data, it can be seen that in this 

case the Sasobit additive did stiff en the binder. 

It would no longer meet a PG 58-34 grade, but 

would be at higher temperatures at both the 

upper and lower values. Additional testing was 

not performed to determine the actual binder 

grade.

PRODUCTION MIXTURE TESTING

During the production of the three mixtures, 

samples were taken periodically from the 

11

Control Advera Sasobit

Average Std. Dev. Average Std. Dev. Average Std. Dev.

1" 100.0 0.00 100.0 0.00 100.0 0.00

1/2" 85.8 2.15 83.2 2.09 85.0 1.92

3/8" 69.2 2.47 67.1 2.54 68.5 2.45

#4 42.8 2.10 43.6 2.22 43.0 2.11

#8 27.6 1.41 28.9 1.56 28.9 1.68

#40 10.5 0.76 11.3 0.86 11.8 0.72

#200 4.6 0.40 5.1 0.44 5.4 0.22

AC Content 5.28 0.296 5.16 0.219 4.88 0.188

SE 66 3.99 66 2.92 65 2.20

% Fracture 99.8 0.24 99.8 0.31 99.9 0.18

Core Density 93.2 1.07 93.9 1.39 93.4 1.20

Moisture Content 0.35 0.16 0.41 0.06 0.53 0.10

Table 5 ~ Conventional mix properties.

Control Advera Sasobit

Average Std. Dev. Average Std. Dev. Average Std. Dev.

Gmb 2.298 0.0147 2.315 0.0160 2.311 0.0159

Gmm 2.438 0.0080 2.440 0.0092 2.452 0.0071

Va 5.8 0.78 5.1 0.92 5.7 0.69

VMA 15.0 0.54 14.3 0.53 14.2 0.60

VFA 61.7 4.22 64.3 5.27 59.8 3.56

Table 6 ~ Superpave mix properties.
in the fi nal placed mat. The standard deviation of 

the core density values was higher for the Advera 

and Sasobit, but the average is only marginally 

higher than the control mixture. Based on the 

data, the range was greater for the warm mixes 

than the control mix. Despite lower average 

asphalt contents, the highest in-place density 

values were from cores taken from the warm mix 

sections. Since the same compactive eff ort was 

applied in each case, this would suggest that the 

warm mix additives enhance the compaction of 

the mixture.

Additional specimens were fabricated for 

moisture sensitivity testing including tensile 

strength ratio (TSR), Hamburg rut testing, and 

Asphalt Pavement Analyzer (APA) rut testing. In 

order to provide suffi cient material for specimens 

properties and Table 6 depicts the Superpave 

volumetric properties.

The gradations for the three diff erent mixtures 

were fairly consistent. The most signifi cant 

diff erence was that the asphalt content was 

below the targeted value of 5.3%. There was 

also higher than normal amounts of moisture 

content. During production the contractor 

obtained lower moisture content values due to 

an oven malfunction and insuffi cient heating; 

this unfortunately led to lower asphalt contents. 

The low asphalt contents also contributed to the 

high air voids and VMA values that were obtained 

from the Superpave specimens.

In spite of the low asphalt contents, the core 

density values indicate that density was achieved 

12

Advera Mixture

Specimen # Air voids Strength (kPa) Specimen # Air voids Strength (kPa)

Dry

1 8.0 441

Dry

1 7.1 469

2 7.7 455 4 6.6 531

4 7.6 476 6 7.6 476

Wet

3 7.9 359

Wet

2 7.2 400

5 7.6 352 3 6.7 428

6 8.0 372 5 7.2 420

Average Dry 457 Average Dry 492

Average Wet 361 Average Wet 416

TSR 0.79 TSR 0.85

Table 8 ~ Tensile strength ratio data for the Advera Mix.

Control Mixture

Specimen # Air voids Strength (kPa) Specimen # Air voids Strength (kPa)

Dry

2 9.6 434

Dry

2 7.6 490

4 8.8 428 5 7.1 510

6 9.9 421 6 7.4 490

Wet

1 9.8 338

Wet

1 7.6 400

3 9.4 365 3 7.1 448

5 9.3 372 4 7.2 414

Average Dry 428 Average Dry 497

Average Wet 358 Average Wet 421

TSR 0.84 TSR 0.85

Table 7 ~ Tensile strength ratio data for the control mix.
rut limits as the maximum rut value observed 

was 4.00 mm. The plots of all of the rutting data 

also indicate that stripping is not occurring in any 

of the mixtures tested. This may be due to the 1% 

hydrated lime that was a necessary additive in 

all of the mixtures as an anti-stripping agent as 

indicated from the mix design. 

The Sasobit WMA did show an average 

rut depth almost 1 mm less than the control; 

however, with the limited number of samples 

tested it is diffi cult to determine the statistical 

signifi cance. This lower rutting may be attributed 

to a stiff ening of the asphalt binder that was 

noted earlier. Table 10 provides the data from the 

Hamburg rut tests.

to be fabricated for various moisture sensitivity 

tests, material was combined from individual 

samples.

The tensile strength ratio test results were 

very similar, although one of the Advera WMA 

results would not pass the nationally established 

minimum ratio of 0.80. All of the dry strength 

values were fairly low, averaging approximately 

70 psi (480 kPa) primarily due to the relatively 

soft grade of binder that was used on the project. 

Tables 7, 8, & 9 contain the data for this testing.

The Hamburg rut testing also provided very 

similar performance results between the three 

mixtures. The specimens were tested at 40 °C 

in a wet condition. The data indicates that all 

mixtures would meet current agency maximum 

13

Sasobit Mixture

Specimen # Air voids Strength (kPa) Specimen # Air voids Strength (kPa)

Dry

2 7.1 517

Dry

Only one data set was run.

4 7.2 538

6 7.6 517

Wet

1 7.3 428

3 7.3 441 Wet

5 7.3 448

Average Dry 524

Average Wet 439

TSR 0.84

Table 9 ~ Tensile strength ratio data for the Sasobit mix.

Mixture Specimens Air Void 

Content

Rut Depth 

@ 5,000 

Passes (mm)

Rut Depth 

@ 10,000 

Passes (mm)

Rut Depth 

@ 15,000 

Passes (mm)

Rut Depth 

@ 20,000 

Passes (mm)

Control C-1 & C-2 6.6 & 6.2 2.30 2.90 3.61 3.82

Control C-3 & C-4 8.0 & 7.8 2.50 3.00 3.62 4.00

Control Average = 2.40 2.95 3.62 3.91

Advera A-1 & A-2 8.0 & 8.2 2.70 3.00 3.62 3.80

Advera A-3 & A-4 6.1 & 6.4 2.20 2.50 2.90 3.25

Advera Average = 2.45 2.75 3.26 3.53

Sasobit S-1 & S-2 7.4 & 7.4 2.20 2.80 2.97 3.28

Sasobit S-3 & S-4 6.8 & 6.6 1.90 2.50 2.59 2.60

Sasobit Average = 2.05 2.65 2.78 2.94

Table 10 ~ Wet Hamburg rut test at 40 °C.
The data indicates that the binder from both of 

the warm mixes experienced a reduced amount 

of aging and stiff ening. One of the inconsistencies 

noted is that the Sasobit recovered binder did not 

show the same stiff ening eff ect that was noted in 

testing of the original binder sample with 1.5% 

Sasobit added. However, the results do indicate 

that the warm mixtures did experience less aging 

during the manufacturing process due to the 

reduced hot plant temperatures. For the location 

of this project, less aging of the binder could be a 

signifi cant benefi t in pavement performance by 

reducing thermal cracking potential.

ADDITIONAL TESTING

Additional samples were tested by the Federal 

Highway Administration (FHWA) Offi ce of 

Pavement Technology’s Mobile Asphalt Mixture 

Testing Laboratory (MAMTL) and also by Western 

Research Institute. The results and analysis of 

this testing is not part of this report but will be 

published independently.

FUEL REDUCTIONS

As part of the contract modifi cation, the 

contractor monitored the fuel usage at the 

hot plant for the three diff erent mixtures. 

The Advera WMA and the Sasobit WMA both 

exhibited a reduction in fuel consumption by 

24% and 15%, respectively. It should be noted 

that the aggregate condition for the last day of 

paving with the Sasobit WMA was substantially 

wetter than the previous days of production 

Rut testing was also performed using the 

Asphalt Pavement Analyzer (APA) rut testing 

device. The testing was performed in a dry 

condition and at the temperature of 58 °C in 

accordance with the binder grade selected for 

the project.

The rut data parallels the results of the 

Hamburg rut testing. The Sasobit WMA indicated 

the best rutting resistance, but none of the mixes 

performed poorly in the test. All rutting values 

were low. The fact that the Sasobit WMA provided 

the best results may again be indicative of the 

stiff ening eff ect of the binder. The APA rut data is 

provided in Table 11.

RECOVERED ASPHALT BINDER TESTING

Asphalt binder was recovered from the 

mixture samples that were obtained during the 

production of the mixtures. In order to provide 

suffi cient material for 

the extraction and 

recovery, mixture 

samples needed to be 

combined. The binder 

was recovered using the 

centrifuge extraction 

and rotovapor recovery 

methods (ASTM D2172 

and ASTM D5404). The 

results of the recovery 

are listed in Table 12.

14

Mixture Specimens Average Air 

Void Content

Average 

Rut Depth 

Control C-1 to C-6 7.0% 2.6 mm

Control C-7 to C-12 7.4% 2.4 mm

Control Average = 7.2% 2.5 mm

Advera A-1 to A-6 7.8% 2.8 mm

Advera A-7 to A-12 6.4% 2.7 mm

Advera Average = 7.1% 2.8 mm

Sasobit S-1 to S-6 8.0% 2.1 mm

Sasobit S-7 to S-12 6.9% 1.7 mm

Sasobit Average = 7.5% 1.9 mm

Table 11 ~ Asphalt Pavement Analyzer rut test at 58 °C.

Property Control Mixture 

(avg. of 4 samples)

Advera Mixture 

(avg. of 4 samples)

Sasobit Mixture 

(avg. of 3 samples)

DSR, G*/sin δ 

@ 58 °C 5.495 kPa 3.786 kPa 4.202 kPa

DSR after PAV, 

G* (sin δ) @ 16 °C 3,252 kPa 2,770 kPa 2,848 kPa

BBR, Stiff ness, 

@ -24 °C 280 MPa 246 MPa 254 MPa

BBR, Slope, 

m-value @ -24°C .302 .310 .313

Table 12 ~ Recovered binder properties.
Based on these results, none of 

the mixtures exhibited stripping 

characteristics. The results also 

indicate that the addition of 1% 

hydrated lime as an anti-strip agent in 

all of the mixes proved to be eff ective.

• The Hamburg rutting results indicate 

generally good performance by all of 

the mixtures; however, it was noted 

that the Sasobit mixture had the 

lowest rutting depths.

• Similar to the Hamburg results, the APA 

rutting results indicated good rut 

resistance for all of the mixtures with 

the Sasobit mixture having the lowest 

rut depth.

• There is defi nite fuel savings realized 

when using Advera and Sasobit as 

warm mix additives due to a reduction 

in the fuel used to heat the aggregates. 

Additional factors such as construction 

processes, hot plant operations, plant 

modifi cations, and location of project 

will certainly have an impact on the 

cost benefi t analysis of using these 

additives. A complete cost benefi t 

analysis was not performed on this 

project.

CONCLUSIONS AND RECOMMENDATIONS

This technology deployment eff ort provided 

knowledge and experience in the placement and 

evaluation of warm mix asphalt. In doing so, it 

provided specifi c information to the agency and 

construction industry in the potential for this 

technology to be used in future FLH construction 

projects. This roadway will be monitored to 

evaluate the performance of these mixtures in 

order to evaluate the long-term performance 

of the warm mix asphalt when compared to 

conventional hot mix.

It was benefi cial to provide an opportunity for 

the contractor to be in “full production” mode for 

the placement of these materials as this provided 

a valuable evaluation of this technology. This 

of the control and Advera WMA due to a heavy 

rainstorm. The increased moisture content of the 

aggregate stockpiles would have increased the 

fuel consumption for this last day of paving.

SUMMARY OF FINDINGS

• Visible smoke and fumes were 

substantially reduced in both of the 

warm asphalt mixes. Workers noted 

no handling diffi culties of the warm 

asphalt mixtures at the reduced 

temperatures.

• Temperatures at the hot plant were 

diffi cult to regulate at the lower warm 

mix asphalt temperatures. Hot plant 

operators may need to make specifi c 

burner adjustments when producing 

mixtures at reduced temperatures.

• From a review of infrared thermal images, 

both of the warm mixes exhibited 

a more uniform windrow and mat 

temperature when compared to the 

control mix.

• Both warm mix additives examined in 

this technology deployment aided in 

the compaction process of the mix. 

This was exhibited both in mix design 

specimens that exhibited lower air 

void content than the control, as 

well as the as constructed pavement 

with average core densities higher 

than the control. All mixtures met the 

density requirement established in 

the contract with the warm asphalt 

mixtures providing the highest 

density values.

• Tests of the virgin binder that was 

modifi ed with 1.5% Sasobit indicated 

a stiff ening of the binder both on the 

upper and lower temperature values. 

This was not consistent with the results 

from the testing of the recovered 

binder from produced mix which did 

not indicate signifi cant stiff ening.

• The TSR testing provided consistent 

results with all three of the mixtures. 

15
technology shows promise and could have a 

large impact in the paving industry.

At this point in time it is premature to advance 

to a standard specifi cation; however, FLH will 

continue to pursue the placement and evaluation 

of warm mix technologies. As these evaluations 

continue, FLH will use this information to develop 

a standard specifi cation for use.

ACKNOWLEDGEMENTS

This technology deployment would not have 

been possible without the support of the WFLHD 

construction staff assigned to the project, the 

cooperation of the National Park Service, and the 

eff orts of HK Contractors, Inc.

16

Technical Report published by

Technology Deployment Program

Western Federal Lands Highway Division

Federal Highway Administration

610 East 5th St.

Vancouver, WA 98661

For more information or additional copies 

contact:

Amit Armstrong, Ph.D., P.E. 

Phone: 360.619.7668

Fax: 360.619.7846

Amit.Armstrong@fhwa.dot.gov