Warm Mix Asphalt for Roads
Warm-mix asphalt is a process derived from the hot-mix method of creating paving asphalt. Paving asphalt material is composed of approximately 5% asphalt/bitumen and 95% aggregates, which are primarily stone, sand or a composite of different materials.
In order for the asphalt to bind over the road base, it must be heated and poured. This results in a homogenous finish that dries smooth and is more durable than its cold-mix counterpart.
Warm-mix asphalt technology allows asphalt paving at a lower temperature than its hot-mix counterpart. In general, it helps to reduce the overall installation costs of paving. Hot-mix also prevents transport of paving from RAP centers, because of the difficulty in sustaining the high temperatures. For many contractors, this is a logistical challenge that needs to be overcome as hot-mix asphalt is a requirement for stronger roads. However, it costs more to make and unless made on-site, can cost plenty to move from the factory to the road site.
WMA allows this binding at lower temperatures by “melting” the binder at lower temperatures, allowing them to coat the aggregates. This is similar to adding chocolate chips to a dough mixture. The softer the dough, the easier it is to add the chips. WMA allows the dough to soften at a lower temperature to make it easier to handle and compact.
Lowered temps allow contractors to cover longer distances during paving season. Hot asphalt mixes cool faster in low temperatures which can cause damage and structural breakage. This is why asphalting usually takes place during high temperature days. However, warm-mix asphalt has a lower cooling point, extending paving days to cooler climes and making night work feasible.
Warm-mix also has a beneficial impact for workers. The process emits less fumes and fuel emissions, and has a less offensive odor than hot-mix asphalt. This results in environmentally friendly construction areas and improved working conditions for asphalt workers. Workers are less exposed to smoke and dust. This is exceptionally important for underground working conditions. Better conditions also mean more working days, as WMA improves air quality around the site.
The process also uses 20% less fuel than hot-mix, which lowers the consumption impact on the environment. Labor and time are also reduced because WMA makes compaction easier and allows for better returns with less labor.
WMA results in dense, compact roads that meet and exceed safety standards. Compacted, dense roads need less repair, as they do not crack, rut or ravel as often. Furthermore, warm-mix can be used for different types of asphalt concrete and allow for a variety of thicknesses and uses. WMA is proven safe and used in a variety of roads, from high-traffic highways to inner-city roadways.
