A new technique of pavement design

1. Warm Mix Asphalt Pavement
Design
Submitted by:
Janmejaya Barik
Roll no- 12010008
Branch- Civil

2. OVERVIEW
 Introduction
 What is Warm mix asphalt?
 Mechanisms involved in temperature reduction
 Laboratory design of warm asphalt mixes
 Mechanical performance of warm asphalt mixes
 Guidance on mixing, laying and compaction of warm asphalt mixes
 Benefits and drawbacks of WMA
 Comparison between life-cycle cost analysis of WMA and HMA
 conclusions

3. INTRODUCTION
Over the last two decades, the production and appliance of asphalt
mixtures have been improving, particularly to achieve economic and
environmental objectives. Recently, the improvement has paid more
attention to the reduction of energy consumption throughout the
process, without changing the in-service mechanical performance of
these asphalt mixtures.
There is a growing international pressure on the reduction of fossil
fuels consumption and the emission of greenhouse effect gases (GHG),
such as CO2 (carbon dioxide).
If a significant temperature decrease could be achieved within the
production practice of asphalt mixtures, while the workability of the
material is adequate and mechanical performance attained is the same
as or even better than HMA, the gain for the environment and the
society in general would be significant.

4. What is warm mix asphalt?
 Hot Mix Asphalt (HMA) is a result of drying and heating mineral
aggregates, and bitumen at temperatures above 140oC.
 If a significant temperature decrease could be achieved within
the production practice of asphalt mixtures, while the
workability of the material is adequate and mechanical
performance attained is the same as or even better than HMA,
the gain for the environment and the society in general would
be significant.
 From this concept Warm Mix Asphalt (WMA) developed which
require lower production temperature.

5. Mechanisms Involved in Temperature Reduction
 Organic additives
 Chemical additives
 Foamed bitumen technologies

6. ORGANIC ADDITIVES
 Addition of an organic wax to bitumen or blending to asphalt
concrete mixtures, reducing the viscosity of the binder.
 When the asphalt cools, the additive crystallizes forming a lattice
structure of microscopic particles.
 Sasobit- produced from natural gas using the Fisher–Tropsch(FT)
process
 Asphaltan-B- blend of wax obtained by solvent extraction from lignite
or brown coal (Montan wax) and fatty-acid amides
 Thiopave™- a technology that uses a Sulphur-enhanced additive.

7. CHEMICAL ADDITIVES
 Chemical additives may reduce the mix and compaction temperatures
around 30oC
 Aggregates are heated before mixing, the water within the emulsion
vaporizes during the production process and the binder covers the
aggregate particles
 Package of products such as surfactants, emulsification agents, aggregate
coating enhancers and anti-stripping additives
 Rediset™ WMX and Cecabase RT- surfactant and adhesion agents
 Evotherm™ - emulsification agent

8. FOAMED BITUMEN TECHNOLOGIES
 Bitumen foam is generally obtained by adding a small amount of cold
pulverized water into preheated bitumen
 Foamed bitumen is obtained mixed together with aggregate at an
ambient temperature or previously heated at a moderate temperature
(under 100oC)
 Subcategorised - water based & water containing
 Water mixing technologies-
-Low Energy Asphalt (LEA)
-Warm Asphalt Mixes foam (WAM-foam™ )

9. Laboratory design of warm asphalt mixes
 Superpave (AASHTO R 35) -in the USA
 Marshall method (EN 12697-34:2004 + A1 and EN 13108-
1:2006), among other European methods, such as the French
one - in Europe
 Based on gyratory compaction
 Foaming plant - Wirtgen WLB10

10. Recommended amount of some available WMA
additives
Additive Addition rate range Typical addition rate
Organic additives:
Astec PER 0.5–0.75% by total weight of
RAP (only for high levels of
RAP)
__
Asphaltan-B 2–4% by weight of the total
binder
2.5% by weight of binder
Sasobit 0.8–4% by weight of the total
binder
1.5% by weight of the total
binder
SonneWarmix™ 0.5–1.5% by weight of the
total binder
0.75% – maximum
recommended for
unmodified, virgin mixes
Chemical additives:
Cecabase RT 0.3–0.5% by weight of binder __
Rediset™ WMX 1.5–2.5% by weight of binder __
Evotherm™ About 5% of diluted chemical
package by weight of binder
__

11. Mechanical performance of warm
asphalt mixes
 Vary in a large range depending on the specific WMA technique
applied as well as the type of material fabricated
 Temperature and loading characteristics plays significant influence on
performance
 Affected properties :
-Water sensitivity
-Stiffness modulus
-Resistance to fatigue
-Resistance to low temperature fracture
-Resistance to permanent deformation

12. Water Sensitivity
 Water sensitivity or water damage - suffering a substantial
reduction of resistance of some asphalt mixtures over the years in
the presence of water
 Causes rutting and/or cracking development.
 Failure of the binder aggregate interface and/or the cohesion within
the binder–filler mastic
 Moisture left behind during the construction process can also increase
the water susceptibility of asphalt mixtures.
 Surfactants - bridge between the asphalt binder and the aggregate
surface, promoting adhesion and resisting the action of water
 Non-limestone fine aggregates, by adding 2% of hydrated lime powder
as anti-striping agent.
 BY increasing slightly the production temperature

13. Stiffness modulus
 Stiffness (stress/strain ratio) decreases as manufacturing temperature
decreases as coating of coarse aggregates particles and bonds between
them improve
 Stiffness modulus depends on the type of additive, compaction method
and temperature
 WMA mixes had higher stiffness moduli than HMA
 Crystallisation due to wax additives can ensure good stiffness values for
WMA dense-graded asphalt
 Mixes with wax additives had consistently higher modulus values than the
other types of WMA

14. Resistance to fatigue
 Fatigue tests induces continuous damage on the specimen until
failure occurs
 WMA usually suffer more fatigue damage at lower strain levels
than HMA
 So, WMA preferred in heavy duty pavements
 For Sasobit WMA mixes fatigue performance decreases 22% as
compared to HMA

15. Resistance to low temperature fracture
 Very important in very cold climates
 In WMA the bonding at the interface binder-coated aggregate is
still in doubt at low in-service temperature
 Differential thermal contraction within asphalt mixes at very low
temperatures thermal cracking micro-cracks development
 WMA with wax additives or Evotherm™ at 200C exhibit similar or
better performance than the HMA

16. Resistance to permanent deformation
 Essential in hot climates
 Mixture resistance to permanent deformation decreases as
production temperature decreases
 At high temperature(around 50 or 600C), the rut depth induced
on the material increases as the number of wheel passes raises
 WMA with wax additives (Sasobit) has a improved resistance to
rutting at higher in-service temperature

17. Guidance on mixing, laying and compaction of
warm asphalt mixes
 Products added in form of pellets or pastilles are preferably added by means
of a pneumatic feeder
 In batch plants additives are introduced directly into the mixer
 Thiopave™: conveyor belt system used directly feeding the mixing drum or
the pug mill
 Liquid additives: injected from a heated container into the plant’s binder
line by means of a dosing pump, or pre-blended into the binder
 Zeolite(powdered): added by means of a com- pressed air system. In drum
plants

18. Benefits of WMA
POLLUTANTS REDUCTION IN
PERCENTAGE
CO2(carbon dioxide) 30–40%
SO2(sulfur dioxide) 30–40%
VOC (volatile organic compounds) 50%
CO (carbon monoxide) 10–30%
NOx (nitrous oxides) 60–70%
dust 25–55%
for asphalt aerosols/fumes 30% to 50%
polycyclic aromatic hydrocarbons (PAHs) 30% to 50%
 Significant reduction on pollutant and GHG
emissions
 Doesn’t need curing time before opening up to
traffic and does not require a sealing layer
 As operating temperature and emissions are
lower, easier for plants to be allowed in the
proximity of urban areas
 Viscosity of the stiff binder decreases and the
drop of temperature with time is less  allows
higher haulage distances reduces the risk of
compaction troubles  requires less time to
cool the laid  Better workability
 Reduction of the energy consumption up to 35%

19. Drawbacks of wma
 High initial production cost
 Carbon emissions related to the production of additives
may be higher
 On long-term performance may face some struggle
 In-service moisture susceptibility of WMA is sometimes
higher

20. Comparison between life-cycle cost
analysis of WMA and HMA
production
of raw
materials,
construction
maintenance
and repair
demolition
 Except WMA additives, constituent materials is approximately the same for WMA and
HMA
 Emissions associated with additives can balance the general reduction of by-product
 Temperature reduction in WMA leads to significant decreasing on fuel consumption and
CO2 emissions
 Maintenance and repair would be more or less the same in both cases
 Deposit or recycling for both types of technology is also same

21. conclusions
WMA have a significant number of advantages comparing to HMA,
basically associated with energy saving which lead to a major reduction
of GHG emissions and pollutants. Laying and compaction operations are
generally improved, as workability of WMA is adequate and the release
of fumes and odours for workers is much lower.
But operation and maintenance of plants used for WMA production
require additional care.
Even though some drawbacks have also been pointed out, benefits
of WMA in a whole seem to surmount their drawbacks.

22. REFERENCES:
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23. THANK YOU