This document summarizes a presentation on warm mix asphalt (WMA) given at the 2016 Florida Public Works Expo in Tampa. The presentation covered an overview of WMA, its usage nationally and in Florida, and experiences with WMA from the Florida Department of Transportation and a contractor. WMA allows asphalt to be produced and placed at lower temperatures than conventional mixes through the use of additives. This can provide benefits like reduced emissions and fuel usage while still meeting mixture requirements. However, some argue hotter mixtures are still better and savings may not be as large as advertised.

1. Florida Public Works Expo 2016
Tampa, Florida
Jim Warren, Asphalt Contractors
Association of Florida, Inc.
jwarren@acaf.org

2.  JimWarren – Overview ofWMA and
Industry’s perspective of its usage –
nationally and in Florida (20 min)
 Wayne Rilko – FDOT experiences withWMA
(15 min)
 Kelly Brock – Castleberry’s experiences with
WMA (15 min)
 Q & A: (10 min)

3.  What is it?
 Which isWarm mix?
 How long has it been around?
 Advantages - Disadvantages?
 What are the technologies?
 Resources

4.  Conventional asphalt mix designs
(Superpave, Friction Course) produced and
placed at lower temperatures by addition of
warm mix additive.
 Very small amounts of additive are used
during the production.

5.  WMA technologies reduce the viscosity (the
thickness) of the asphalt binder so that
asphalt aggregates can be coated at lower
temperatures.
 Warm mix meets the same mixture
requirements as Superpave or Friction
Courses.
 Reductions of 50 to 100 degrees F have been
documented. 25-50F is common.

6.  FHWA Definition: WMA is a general term for
technologies that reduce the temperature
needed to produce and compact asphalt
mixtures for the construction of pavements.
WithWMA, temperatures generally start 30 °F
to 70°F lower during mixing and remain lower
during trucking, placement, and compaction.
The mixture cools after compaction to form the
asphalt pavement.
 FDOT: 285 F or less and use a warm mix additive

7.  Research in Europe in Mid 1990’s
 US Scan tour in 2002.
 2004World of Asphalt Demo in Nashville,TN
 Demos and conferences since.
 Implementation nationwide

9.  Reduction inTemperature
 ReducedAging of Binder
 Reduction in Fuel needed to make Mix
 Lower emissions
 Increased workability
 Longer Haul distances
 Expanded paving season.

10. Warm Mix Asphalt
Temp = 320º F
Temp = 245º F

11.  Reduced Emissions at Plant
Conventional Mix Warm Mix

12. Temp Drop vs. Time
y = -0.0195x2
+ 2.3228x + 66.012
R2
= 0.9719
y = -0.1236x2
+ 8.147x + 17.182
R2
= 0.9746
30
50
70
90
110
130
150
0 10 20 30 40 50 60 70
Time (minutes)
TempDrop(°F)
Poly. (AsphaMin) Poly. (Conventional)
Graph courtesy of Chris Nesmith – FDOT Turnpike

14.  Not everyone sees the benefits ofWMA.
 Conventional wisdom of “Hotter is Better”
 Many customers – different wants.
 Savings not as advertised.
 Difficult for asphalt plant to make Hot Mix
andWarm Mix together.
 High moisture contents (Agg and RAP) take
high temperatures to dry and heat.
 Potential tenderness in field.

15.  “Warm Mix” hasn’t caught on to the extent as
other states as defined by FHWA/FDOT.
 Running warm mix technologies at not so
warm mix temperatures. (above 275F) as a
compaction aid:
 Maintain recycle contents and temperatures.
 Might be a option to help change culture over
time.
 Aggregate specific issues with high moisture
conditions in FL.

16.  Foamed Asphalt Mixtures
 Additive added to the Binder
 Additive added to the Mixture
 Wet Aggregate Mixtures

17.  Warm mix is just not so hot Hot MixAsphalt
 Warm mix is another tool in the tool box.
 Don’t mandate use ofWMA or specific
products. Let the market sort it out.
 Focus on the putting the right mix
(type/thickness) in the right place (condition)
at the right time (LCC).

18. Google: Warm Mix Asphalt
Official Site: http://www.warmmixasphalt.com/
FHWAWeb site:
https://www.fhwa.dot.gov/innovation/everyd
aycounts/edc-1/wma.cfm
ComprehensiveArticle:
 http://www.nxtbook.com/nxtbooks/naylor/N
APS0112/index.php
 2013 Nova Award:
https://youtu.be/q47p1SAy4g4