Notes

1.Technologies For WMA:
Organic additives, which are described as “intelligent fillers”, provide reduced viscosity at mixing temperatures and increased viscosity at service temperatures of WMAs [17] . At temperatures above the melting point of the organic additives, the viscosity of the binder is reduced to facilitate lower mix production temperatures, whereas at temperatures below the melting point of the additives, the stiffness of the binder is increased [23] . Hence, organic additives with melting points higher than the expected in-service pavement temperatures are selected to prevent permanent deformation [12] .
Chemical additives, on the other hand, do not reduce the viscosity of asphalt binder; rather they are surfactants added to the binder in a typical concentration of 0.30% by mass of the asphalt binder to improve the coating capability of the binder at lower mixing temperatures. This enables placement of the mix at temperatures about 20˚C - 30˚C below that of conventional HMA [16] [17] . Examples include Evotherm, HyperTherm, and REVIX.
When foaming techniques are used in WMA production, controlled amounts of water are introduced to heated asphalt binder to cause a rapid expansion of the water, and accordingly the asphalt binder. This results in a temporary reduction in the viscosity of the binder which facilitates aggregate coating and improved workability at reduced temperatures. At pavement service temperature, the binder viscosity becomes normal.
2.Sustainability Benefits:
Low energy use for production and placement,・ Low emission of greenhouse gases,・ Conservation of natural resources,・ Increased reuse of old asphalt in new asphalt mixes.
3.Economic Benefits:
Reduced Fuel Use
Potential for Increased RAP in WMA
Extension of Paving Season(in Germany, paving was completed at ambient temperatures between −3˚C and 4˚C)
4.Performance:
In all these applications, WMA exhibited similar or better performance, including improved compaction, similar stiffness and rutting resistance, improved resistance to fatigue and thermal cracking, similar or less moisture damage and greater durability compared with HMA
5.Limitations:
higher costs because
lack of data concerning their long-term performance.
greater moisture
susceptibility due to lower temperatures
coating and bonding problems.