Download - AAPA 2010 Study Tour – Warm Mix Asphalt Warm Mix Asphalt Warren Carter | Cassandra Simpson Andrew Bethune.

AAPA 2010 Study Tour – Warm Mix Asphalt

Warm Mix Asphalt

Warren Carter | Cassandra SimpsonAndrew Bethune


IntroductionIntroduction

• WMA represents a group of technologies which allow a reduction in the temperatures at which asphalt mixes are produced and placed

• WMA is produced at temperatures that are 20°C - 50°C below that of hot mix

www.aapa.asn.au


Emissions and Energy


Benefits of WMA• Improved working conditions• Less fumes and emissions• Less energy consumption• Decreased binder aging during production• Early site opening• Cool weather paving• Compaction aid for stiff mixes• Longer haul distances• Improved and more consistent compaction


HMATemp = 160oC

WMATemp = 132oC


Warm Mix Hot Mix


WMA Technologies

• Free water systems (mechanical foaming by water injection) – 130°C - 140°C

• Water carrying chemical additives (additives introduce moisture e.g. synthetic zeolites) – 115°C - 135°C

• Water carrying non-chemical additives (LEA process) – 95°C - 110°C

• Chemical additives (reduce internal friction e.g. Cecabase RT, Evotherm 3G, HyperTherm, etc) – 110°C - 135°C

• Rheological modifiers (reduce binder viscosity during mixing e.g. Sasobit, Rediset WMX, etc ) – 115°C - 135°C


WMA Production TemperaturesWMA Production Temperatures


WMA Technologies


US Experience - Evaluation

• European scan/study tours (2002 and 2007)• Growth has been rapid

o Technologies: 3 (2005) – 23 (2010)o Trials: 15 states (2007) - 45 states (2010)oMarket: 2% (2007) – 10% (2010) – 50% (2015?)

• Key properties being evaluatedo Deformation resistance/ruttingo Cracking/fatigueoMoisture sensitivity


Warm Mix Demonstration Projects in the U.S. as of Jan. 2007

Warm Mix Demos


Warm Mix Demonstration Projects in the U.S.

Warm Mix Demos


US Experience - Implementation

• Initial client desires were that WMA provides equal or better performance compared to hotmix

• The various states have approached implementation differentlyo collaborative trials o permissive specifications o lengthy approval processes with laboratory and field

evaluationo list of approved technologies/productso maximum production temperatures (non-attainment

areas, over crack sealing, etc)


US Experience - WMA

• Dense graded asphalt• Open graded asphalt• Stone mastic asphalt• Crumbed rubber asphalt• Conventional bitumens and polymer modified

binders


US Experience - Concerns

• Rutting• Strength issues• Stripping• Water injection technologies in freeze climates

(ravelling)• Production issues – ensuring the aggregate is

dry• Plant addition of WMA additives vs terminal

blending


US Experience – WMA Mix Designs

• Mix designs are generally the hotmix design with the warm mix technology applied

• Some minor allowance is made to WMA containing Advera and Asphamin as these become an inert filler (once the water is remove)

• Lower voids of a WMA mix design compared to the hotmix design (but binder content isn’t adjusted)


Warm Mix Hot Mix


Questions?