As Spring, 2019 hits and the asphalt plants start firing-up and getting into production, it’s a great time for all of us to hit the Refresh button and get ready for HMA – Oh wait, did I mean WMA…???
Welcome to the Green New Deal for hot mix asphalt.
This past week, I had the good fortune of spending some time in an Illinois State Toll Highway Authority (ISTHA) training session on Warm Mix Asphalt (WMA). If you’re like me, an ever-aging codger who is having trouble keeping up with all the industry, managerial and technological advances. Although WMA has been around for a while, 2019 will be the first construction season where I will be introduced & active to the new way of paving.
What’s the Difference between Warm Mix and Hot Mix Asphalt?
I must say, when I heard my boss signed me up for the ISTHA seminar, I thought I was going to be inundated with new terminology, mix design theory, installation methods and a whole lot more.
I was pleasantly surprised to find out that I was wrong.
Pretty-much everything that I’ve learned about asphalt over the past few decades remains the same. Thank God for that.
What has changed is the introduction of Warm Mixes, instead of Hot Mixes. What’s the difference, you ask? Here’s the Cliff Notes:
1. Temperature
Obviously, just by the nomenclature, the normal 300-350 degree mix temperatures of HMA are reduced to the 200-250 degree range for WMA’s. The temperature reduction introduces benefits like reduced energy input & fuel requirements to produce the mix, reduced environmental heat exposure, as well as allows for longer transportation distances between mix yard and job site.
2. Foaming Agents
As you could probably deduce, the temperature reduction between HMA and WMA requires some sort of material adjustment to allow the mix to be produced, tranported, placed & compacted without causing reductions in pavement performance & lifespan. How is the mix adjusted? There are actually several ways.
Manufacturers and producers have developed various chemically and organically-based products that can be introduced to modify the asphalt to perform at lower temperatures. “Foaming agents” are introduced.
What’s a foaming agent?
Full Disclosure – I have no idea….
There are foaming additives. And there is water-based foam injection. You got me – It’s beyond my grasp. If you are interested in it, dive into the topic and then drop me a line on what you found.
The long-and-short: By modifying the mixes, they can be shipped, placed & compacted at lower temperatures.
3. What Else Did We Learn.
You guys know that I am constantly banging the drum about our need to train. To continuously educate ourselves. To never stop learning.
I LOVE TRAINING!!!
I love going to seminars. My Refresh button has a broken spring from me hitting it so many times.
The guys did a great job in walking through the various steps taken to produce, deliver, place & compact and asphalt pavement. I made several notes to myself on a variety of subjects that hit home with me.
KEEP TRAINING!!!
Be the first to comment