Warm Mix Asphalt and How it’s Revolutionizing the Industry
When you’re hot, you’re hot, and when you’re not, you’re likely to have quite a few advantages…when it comes to asphalt, that is.
The industry standard of hot mix asphalt (HMA) has had a good run, providing a mix that has enjoyed proven strength, workability, and longevity for decades. But as the industry continues to advance technologically—and with an eye on sustainability and environmental friendliness—warm mix asphalt (WMA) continues to show up strongly in testing and innovation.
What’s the scoop with WMA?
WMA has been around for quite some time. The concept was first introduced by Professor Csanyi at Iowa State University in 1956. It was then further studied in Europe and was first used in the US in 2004. As the desire to minimize energy usage grows, so does the popularity and innovation of the mix.
So what’s the difference between HMA and WMA?
The most obvious factor is temperature. Traditional HMA is mixed at around 275-350°F. WMA is approximately 100° lower, and with that temperature drop comes a trio of benefits:
- The energy savings of producing the lower temp mix is about 30%, which translates well both economically and environmentally.
- The health benefits to the workers and those in surrounding areas are notable due to the lower emissions produced when the asphalt is laid. The enhanced workability also makes the job easier, and let’s face it, a 100° drop in temperature is certainly welcome.
- A warm mix has proven to be more compatible with the integration of recycled materials. The most popular recycled material in asphalt is old asphalt that has been milled to a specific coarseness and is then added to the new mix. Traditional hot mix has a restricted threshold due to stiffness of the materials. In this way, a road can live many lives and, in fact, is the most recycled material in the country. Warm mix, however, plays well with a higher percentage of recycled asphalt material. Another growing use for recycled materials in asphalt is plastics. Discarded plastics, many of which are not typically easy to reclaim for other uses, are able to be melted down into polymer pellets which are added to the mix.
An added bonus is that WMA isn’t as weather sensitive. This is important, as the temperature differential between cold air and hot asphalt is often prohibitive in the winter in many parts of the country. The shorter cooling time also means traffic can return to the surface more quickly.
As with any advancements in technology and process, but especially in a material that is expected to stand the test of time, there is a lot of research, development, and testing that goes on to ensure WMA is able to withstand the rigors of use and adds value. The industry as a whole continues to explore, refine, and improve the materials with a strong dedication to being environmentally friendly and efficient. We are happy to be a part of the latest in all that is great about asphalt and continue to study and implement best practices for our customers.