Pub. 1 2018-2019 Issue 1

WARM MIX ASPHALT • WMA is versatile. For example, it can be used to create a variety of differ- ent road thicknesses, so it is useful for construction of arterial roads, high- ways, and preservation of the freeway system. In some states, it is used to construct runways. It is also useful for filling potholes. • WMA saves fuel. Fuel savings depend on factors such as aggregate mois- ture content, plant settings, and mix design. Lower mixing temperatures can save between 20–35 percent because less fuel is needed. • Warm mix technology improves working conditions, at the production plant and on the construction site, by reducing exposure to fuel emis- sions, fumes, and odors. More spe- cifically, it affects emission reduction mix design criteria such as moisture content, chemical additives, aggre- gate size, plant settings, percentage of recycled asphalt pavements, and production temperature. • In recent years, energy shortages and climate change have become critical issues and many states have By Craig A. Ide, P.E., Pavement Engineer, Utah Aeronautics Division, UDOT Warm mix asphalt (WMA) is produced at lower temperatures that are 30 to 120 degrees Fahren- heit lower than the temperatures needed to pro- duce hot mix asphalt (HMA). Its first use was in Europe, in 1995, but was not acknowledged in the U.S. until 2004. Today, the asphalt industry has become increasingly interested in WMA because of the following advantages: committed to reducing emissions. WMA has a lower environmental impact and may be placed during bad air quality days when HMA would exceed emission standards. • WMA has the potential for improved compaction and for extending the pavement season. Research is demon- strating that WMA design mixes with highly modified binders, such as PG 70, can use WMA methodologies added to them in order to get better field densities. WMA makes compac- tion easier due to the asphalt mix holding the working temperature longer. This also allows for longer hauling distances. Lab testing of WMA mixes using modified binders, such as PG 70, can use WMA admix meth- odologies to improve field densi- ties. Research comparing Air Void Distribution (VMA) for WMA and HMA found the WMA to be comparable. • Pavement quality improves. Domestic and international research projects have evaluated rutting, cracking and moisture resistance of WMA (with 12