As Warm Mix Asphalt (WMA) moves into the mainstream, hear the latest research on WMA performance from the respected National Center for Asphalt Technology, which puts various pavement technologies to the test under live traffic on a test track in Alabama.

2. 2
Outline
Use of WMA in the USA
WMA Benefits/Challenges
NCHRP 9-47A- WMA vs. HMA
Projects Evaluated
Energy Usage, Emissions
Mix Design
Engineering Properties
Short Term Field Performance
Summary of Findings

3. 3
Warm Mix Asphalt
A process or additive designed to
reduce asphalt mix production
temperatures by 30 to 70°F and
maintain mix workability (non-
sanctioned definition)
A key part of the asphalt
industry’s strategy for
Sustainable Pavements
Categories: foaming, chemical
and organic additives

4. WMA Technologies Available in U.S.
In 2005: 3
In 2014: +30
6

5. 5
Estimated WMA Production
NAPA Surveys

6. 6
Economics of WMA
Water-Injection systems cost $30k to $80k.
Assuming $50k cost, 120,000 tons/yr., 5-year
depreciation, then foamed WMA cost about
8 /tonȼ
If only 1/3 of production is WMA, then cost is
25 /tonȼ
Popular WMA additives are reported to increase
cost by $2 - $3.5/ton of mix
Some costs may be offset by energy savings
and other benefits

7. 7
WMA Usage
NAPA Surveys

8. 8
WMA Benefits/Challenges
Benefits
Reduced energy consumption
Reduced emissions
Extended haul distance
Extended construction season
Better work environment
Challenges
Performance vs. HMA
Standardize Mix Design

9. 9
WMA vs. HMA
NCHRP 9-47A

10. Location Route WMA Technologies Date Const.
St. Louis, MO Hall Street Evotherm ET, Sasobit, Aspha-min May-2006
Iron Mtn., MI M95 Sasobit Sep-2006
Silverthorne, CO I-70 Advera, Sasobit, Evotherm DAT Aug-2007
Franklin, TN SR45 Astec DBG, Advera, Evotherm DAT, Sasobit Oct-2007
Graham, TX US 380 Astec DBG Jun-2008
George, WA I-90 Sasobit Jun-2008
Walla Walla, WA US-12 Maxam Aquablack Apr-2010
Centreville, VA I-66 Astec DBG Jun-2010
Rapid River, MI CR-513 Evotherm 3G, and Advera Jun-2010
Baker, MT Route 322 Evotherm DAT Aug-2010
Munster, IN Calumet Ave. Evotherm, Gencor foam, Heritage wax Sep-2010
Jeff. Co., FL, SR 30 Terex foaming system Oct-2010
Queens, NY Little Neck Pkwy Cecabase, SonneWarmix, BituTech PER Oct-2010
Case Grande, AZ SR 84 Sasobit Dec-2011
NCHRP 9-47A Projects

11. WMA &HMA Production Temperatures

12. 12
Energy Savings with WMA
Fuel savings for WMA is proportional
to the temperature reduction.
Most contractors report burner fuel
usage decrease of about 10 to 15%.
Decreasing mix production
temperature by 52°F resulted in an
average fuel savings of 21 % (NCHRP 9-
47A)

13. 13
Emissions and Worker Exposure with
WMA (NCHRP 9-47A)
 Stack emissions largely result of combusted fuel, reduced
fuel should result in reduced CO2 emissions
 A 52°F reduction in temperature (21% reduction in fuel) in
in a 20% reduction in CO2 emissions
 Worker exposures to respirable fumes during paving were
significantly reduced
 Reduction in application temperature resulted in an
average 36% reduction in TOM (total organic matter)

14. WMA Mix Design
Appendix to AASHTO R35:
Perform design with WMA additive or lab
foaming device
Mixing temp. based on coating, 95% coated,
min.
Compactability: SGC N92 at comp. temp. and 30°C
below the comp. temp., Ratio N92≤ 1.25
Moisture susceptibility-AASHTO T 283, TSR ≥
0.80
Rutting evaluation; Flow Number: AASHTO
TP79, criterion depends on traffic
None of the NCHRP 9-47A field projects were designed
with the Appendix to AASHTO R35

15. 15
WMA Mix Design (NCAT Recommendation
NCHRP 9-47 A)
Complete volumetric mix design without the WMA
technology/additive ( drop in approach) for selecting
optimum asphalt content
Check coating, compactability, moisture resistance and
rutting resistance ( if required) using laboratory produced
WMA

16. 16
In Place Densities
TSR
FN
Engineering Properties HMA vs. WMA

17. In Place Densities (=)
After ~2 YearsAfter Construction

18. TSR-AASHTO M323 (= or ↓)

19. FN Test Results- WMA vs. HMA
Statistical Comparison
9 cases FN WMA lower than HMA
5 cases no statistical differences

20. 20
FN Criteria HMA&WMA
Included in AASHTO TP 79-13
Traffic Level, Million
ESALs
Minimum FN (HMA) Minimum FN (WMA)
<3 NA NA
3 to<10 50 30
10 to <30 190 105
≥30 740 415

21. HMA Flow Number Results
Traffic,
MESALs
Min.
Flow
No.
<3 NA
3 to <10 50
10 to <30 190
> 30 740
Project Route Mix Heating FN
Baker, MT Route 322 Reheated 98
Rapid River, MI CR-513 Reheated 199
Casa Grande, AZ SR 84 No 61
Jefferson Co., FL SR 30
No 414
Reheated 231
Queens, NY Little Neck Pkwy No 291
Munster, IN Calumet Ave. No 561
Walla Walla, WA US-12
No 332
Reheated 426
Centreville, VA I-66 Reheated 1855
HMA Fn Criteria

22. WMA Flow Number Results
Traffic,
MESALs
Min.
Flow
No.
<3 NA
3 to <10 30
10 to <30 105
> 30 415
Project Route Mix Heating WMA Additive FN
Baker, MT Route 322 RH Evotherm DAT 58
Rapid River, MI CR-513
RH Advera 60
RH Evotherm 3G 65
Casa Grande, AZ SR 84 No Sasobit 46
Jefferson Co., FL SR 30
RH Terex Foam 127
No Terex Foam 157
Queens, NY
Little Neck
Pkwy
No Cecabase 115
No SonneWarmix 123
No BituTech PER 128
Munster, IN Calumet Ave.
No Evotherm 3G 177
No Gencor Foam 217
No Heritage Wax 314
Walla Walla, WA US-12
No Maxam Aquablack 200
RH Maxam Aquablack 227
Centreville, VA I-66 RH Astec DBG 439
NCHRP 9-43 Mix
Design Criteria

23. 23
Field Performance of WMA vs. HMA

24. 24
Field Performance Evaluation
Procedure
Three 200-foot sections per mix
Three 6” dia. cores from in right wheelpath, and
four 6” dia cores from in between wheelpaths
Cores used to determine the in-place density
indirect tensile strengths, specific gravity,
gradation, asphalt content, and the true binder
grade for each mix.

25. Field Performance-New Projects
Project Mix Rutting (mm) Cracking (m)
Walla Walla, WA
HMA 5 1
Maxam Aquablack 0 0
Centreville, VA
HMA 3 1
Astec DBG 3 1
Rapid River, MI
HMA 0 0
Evotherm 3G 0 0
Advera 0 0
Baker, MT
HMA 1 0
Evotherm DAT 0 0
Munster, IN
HMA 0 4
Gencor Foam 0 36
Evotherm 3G 0 0
Heritage Wax 0 0
Jeff. Co., FL,
HMA 3 0
Terex Foam 3 0
Queens, NY
HMA - 9
Cecabase <1 20
SonneWarmix - 5
BituTech PER - 5
Casagrande, AZ
HMA 3 NA
Sasobit 0 NA

26. 26
Summary Laboratory Performance
Statistically equivalent as-constructed densities for WMA
mixes compared to the corresponding HMA
TSR -82% of mixes passed 0.8 minimum criterion; 6 mixes
failed: 4 WMA and 2 HMA. Since all of the field projects
performed well; adjusting the TSR criterion on plant mix
samples should be considered
FN results for WMA mixes lower than HMA ( 2/3 of the
comparisons)
FN criteria recommended in NCHRP Report 673 for HMA
and NCHRP Report 691 for WMA seem appropriate for
evaluating plant produced mixes.

27. 27
Summary Short Term Field
Performance
WMA and HMA had no significant difference in rutting
No observed moisture damage in any HMA or in WMA
section
No apparent differences in density between HMA and WMA
WMA and HMA cracking after to years- none or low severity
and extend
No significant differences in surface texture between HMA
and WMA

28. NCHRP Project 9-47A
NCHRP Report 779