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Warm Mix Asphalt

Warm Mix Asphalt. Warren Carter | Cassandra Simpson Andrew Bethune. Introduction. 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.

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Warm Mix Asphalt

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  1. Warm Mix Asphalt Warren Carter | Cassandra SimpsonAndrew Bethune

  2. Introduction • 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

  3. Emissions and Energy

  4. 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

  5. HMA Temp = 160oC WMA Temp = 132oC

  6. Warm Mix Hot Mix

  7. 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

  8. WMA Production Temperatures

  9. WMA Technologies

  10. US Experience - Evaluation European scan/study tours (2002 and 2007) Growth has been rapid Technologies: 3 (2005) – 23 (2010) Trials: 15 states (2007) - 45 states (2010) Market: 2% (2007) – 10% (2010) – 50% (2015?) Key properties being evaluated Deformation resistance/rutting Cracking/fatigue Moisture sensitivity

  11. US Experience - Implementation Initial client desires were that WMA provides equal or better performance compared to hotmix The various states have approached implementation differently collaborative trials permissive specifications lengthy approval processes with laboratory and field evaluation list of approved technologies/products maximum production temperatures (non-attainment areas, over crack sealing, etc)

  12. US Experience - WMA Dense graded asphalt Open graded asphalt Stone mastic asphalt Crumbed rubber asphalt Conventional bitumens and polymer modified binders

  13. 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

  14. 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)

  15. Warm Mix Hot Mix

  16. Questions?

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