**Welcome to Talking Tires**

**Craig Hunter:** Welcome to Talking Tires, the podcast that delves deep into the world of tires. Join us as we explore everything from the science behind the manufacturing to the latest innovations in tire recycling. Our aim is to provide you with a comprehensive understanding of tires, including how they work, how to maintain them, and how to dispose of them responsibly. Whether you’re a seasoned mechanic, curious car enthusiast, or an avid recycler, Talking Tires is the perfect podcast for anyone who wants to learn about the essential component of the modern vehicle and heavy equipment. So, buckle up and join us for an informative and engaging journey into the world of tires.

**Craig Hunter:** All right, welcome back to another episode of Talking Tires. I’m your host, Craig Hunter, president of Tire Reclaim, and we’re here at the 10th annual Tire Recycling Foundation Conference in Denver, Colorado. It’s every two-year conference. Two years ago, we were in Atlanta, Georgia. This year, we get to be in beautiful Denver, Colorado. And I’m here with Doug Carlson from Liberty Tire. Welcome, Doug.

**Doug Carlson:** Well, thank you, Craig. Nice to be here.

**Craig Hunter:** Doug, what is your official title? Because I know it’s asphalt and asphalt-based products, but what’s your official on that?

**Doug Carlson:** Uh, vice president for asphalt products.

**Craig Hunter:** Vice president for asphalt products. That would make sense, right? So I have these podcasts as a platform for the industry to talk about new things, talk about themselves, just kind of get to know the people that are in the industry, the comings and goings, if you will. So Doug, how did you get started in rubberized asphalt?

**Doug Carlson:** Yeah, well, I got started a long time ago, actually. Uh so uh it came through my mother. She was a legislator for the state of Arizona and later became a lobbyist and then started working with she worked on the tire legislation for the state. So became somewhat knowledgeable about scrap tire issues and uh eventually came to work for Craftco.

**Craig Hunter:** We heard them speak yesterday, right?

**Doug Carlson:** Yeah. So this is their 50th-year anniversary. So she worked there uh in ’86-87 that time frame and I was a college student so I became an intern for the association that she ended up managing which uh turned into the rubber pavements association. It represented tire recycling companies and asphalt paving contractors that were using tire rubber uh in the United States, but it ultimately turned into a worldwide organization.

**Craig Hunter:** Way back then.

**Doug Carlson:** Yeah. So, we had huge interest in rubberized asphalt around the world. Part of my job was just to develop a technical library for the association kinda like the Dewey decimal system um of tires.

**Craig Hunter:** I like it.

**Doug Carlson:** Yeah. So we try to categorize all the research by what problem is this tire rubber solving.

**Craig Hunter:** So you became really well-versed in a lot of the technical issues related to rubberized asphalt as a result of that early exposure and the members of that board. Tell me about that. Who were they?

**Doug Carlson:** It was tire recycling companies and the paving contractors that use tire rubber. That actually led me to Liberty because I became the director of that group and Liberty started buying all of my tire recycling member companies. So, I went from about I don’t know 10 tire recycling company members to just about three cuz Liberty acquired a few. That’s how I came to work for Liberty though. So, I’ve been really blessed to be able to do some of the same passionate work on the technology.

**Craig Hunter:** Liberty hired you and they say, “Hey, we want you to just keep doing what you’re doing, but just do it for us.” Is that fair?

**Doug Carlson:** My whole passion in life is to develop the rubberized asphalt market. To be able to do it for Liberty is a great thing and also Liberty’s open-minded, industry-minded, you know what’s good for the industry is good for Liberty and vice versa.

**Craig Hunter:** So, obviously, you had some losses, had some wins. Asphalt, rubberized asphalt, rubber modified asphalt has seen its own roadblocks, no pun intended, right? So you want to talk about some of that?

**Doug Carlson:** Sure. Yeah, I’ve been at it 27 years now. And in the early days, we’re overcoming a lot of industry challenges from what was called the intermodal surface transportation efficiency act. Some other people may have talked about that today, but it was a mandate, a federal mandate, but it didn’t provide any funding to the states on how to figure out how to do rubberized asphalt. And as you’ve come to know, it’s kind of technical. So, you just can’t throw rubber into asphalt. Lot of testing, lot of proving.

**Craig Hunter:** So, do you have any funny stories there? Like things that you saw that might have been totally bonkers?

**Doug Carlson:** Well, the retread business was still pretty relevant as a source of crumb in the early days. Whole tire processing wasn’t a thing in the early ’90s. One contractor used buffings from a retreading operation.

**Craig Hunter:** very familiar.

**Doug Carlson:** So when they put it on the road and paved it, they came back the next day, and it looked like it needed to shave. All the buffings were sticking straight up in the air.

**Craig Hunter:** That almost looked like the little nubs on the tires sticking out. Right.

**Doug Carlson:** Yeah. So that was bonkers.

**Craig Hunter:** That is a bonkers. That’s kind of one of those things. It might only cost them a little bit more to use the rubberized asphalt, but if they got to rip it out, now you’re really talking about some big costs and issues.

**Doug Carlson:** Yeah, that does happen. Specifications are important. The size of the rubber that you use and put it in the mix is important. People need to be aware of that and understand the relationship between the rubber and the asphalt in the hot mix.

**Craig Hunter:** All right. Well, that’s some of the losses. What about some of the wins? Like, we’ve obviously seen some big advancements very recently.

**Doug Carlson:** Yeah, for sure. Uh, we’re experiencing kind of a resurgence of what is called the dry process where rubber is added to the mix directly. So, instead of being added to the liquid, that’s a wet process. It’s added to the liquid, the rubber gets wet. Added to the mix, the rubber stays dry. Until it gets mixed in with the regular asphalt there. But the rubber is handled dry. The technology has vastly improved. Now we use a real fine grind rubber and a lower dosage that’s more attuned to modifying the binder, the liquid, to make the liquid more like rubber instead of the mix more like rubber.

**Craig Hunter:** I like that. And there’s a few technology providers that help create additives that make it more effective, more efficient.

**Doug Carlson:** And I’ve noticed that additives are a big part of asphalt. Some companies are dedicated just to that, international companies. It’s a partnership that needs to happen as well, right? Getting everybody on the same recipe. How does that come about? Are you going to the pavement engineer and kind of designing it from there?

**Doug Carlson:** Sure. Yeah. A lot of the interest in additives came recently with what’s called warm mix technology. So trying to reduce the overall temperature of the asphalt paving material. Lower temperatures reduce the emissions and allow for emissions control and less oxidation of the asphalt. Warm Mix additives have helped make using rubber easier for the contractor.

**Craig Hunter:** Okay, so the benefit of that is emissions. Gotcha. That makes perfect sense.

**Doug Carlson:** Warm Mix additives were big in the early 2000s and a lot of them were used in this next-generation dry process. The additives have helped make using rubber easier for the contractor, solving problems with the contractor. Specifically, warm mix helps reduce the stiffness of the mix when you’re compacting it. It’s nice and easy to roll and compact in place and you end up with a better quality material as well.

**Craig Hunter:** So it’s been 16 years, huh? What about some of the wins? We’ve obviously seen some big advancements.

**Doug Carlson:** We’re experiencing kind of a resurgence of what is called the dry process where rubber is added to the mix directly. The technology has vastly improved over the early days. Now we use a fine grind rubber at a lower dosage to modify the binder. So the rubber is handled dry. The technology has improved exponentially.

**Craig Hunter:** That dry process still requires enough rubber to move the needle, right?

**Doug Carlson:** Yes. So, I grew up in the wet process industry, which can use three times more rubber than the dry process. But it has a lot more complications in the supply chain. The dry process is advantageous because it can go into just about any standard mix. So while it uses less rubber, you have more opportunities to use rubber everywhere.

**Craig Hunter:** Well, we covered a lot today. What’s next for rubber-modified asphalt?

**Doug Carlson:** There is a buzz towards more use of rubber in roads. The cost to do it has actually come down. The dry process is very easy to do and very low cost, making it easy for departments of transportation to deploy the technology. The cost of doing business with rubber is dropping.

**Craig Hunter:** Are you excited about the future?

**Doug Carlson:** Absolutely. The future for rubber-modified asphalt is very bright. There’s a lot of momentum from different areas pushing toward more use of rubber in roads. It’s becoming a major consumer of scrap tires in the U.S., and the environmental benefits make it worthwhile for both commercial and public projects.

**Craig Hunter:** Well, Doug, we appreciate you coming on. Thanks for your insights and expertise in rubberized asphalt.

**Doug Carlson:** Thanks for having me, Craig. Have a good day.

**Craig Hunter:** Take care.