# Talking Tires: An Exploration into the World of 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 tire 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 this essential component of modern vehicles and heavy equipment. So, buckle up and join us for an informative and engaging journey into the world of tires.

Alright, 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. This conference takes place every two years. 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:** Vice president for asphalt products.

**Craig Hunter:** That would make sense, right? I have these podcasts as a platform for the industry to talk about new things, talk about themselves, just to 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. It came through my mother. She was a legislator for the state of Arizona and later became a lobbyist and then started working with tire legislation for the state. So became somewhat knowledgeable about scrap tire issues and eventually came to work for Craftco, which we heard them speak yesterday, right?

**Craig Hunter:** Okay.

**Doug Carlson:** Yeah. So this is their 50th year anniversary. She worked there 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 turned into the rubber pavements association. It represented tire recycling companies and asphalt paving contractors that were using tire rubber in the United States, but it ultimately turned into a worldwide organization.

**Craig Hunter:** Way back then.

**Doug Carlson:** Yeah. Yeah. So, we had huge interest in rubberized asphalt all around the world. Part of my job was just to develop a technical library for the association, kind of like the Dewey decimal system but for tires. We tried to categorize all the research by what problem is this tire rubber solving, what problem does the tire rubber solve in this highway report. So I 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?

**Craig Hunter:** It was tire recycling companies?

**Doug Carlson:** 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.

**Craig Hunter:** Yes. Okay.

**Doug Carlson:** So, I went from about, I don’t know, 10 tire recycling company members, member companies to, well, just about three because Liberty acquired a few. That’s how I came to work for Liberty though. I’ve been really blessed to be able to do some of the same type of passionate work on the technology.

**Craig Hunter:** That was my question. So, Liberty, they hired you and said, “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. So, I’ve been there 16 years now, and it’s been a really fun time.

**Craig Hunter:** Yeah, so some you obviously had some losses, had some wins. Asphalt, rubberized asphalt, rubber-modified asphalt has seen its own roadblocks, no pun intended, right? So, do you want to talk about some of that? I mean, it’s been a long battle.

**Doug Carlson:** Sure. Yeah, I’ve been at it 27 years now. And in the early days, we were 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 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.

**Craig Hunter:** Yeah, it’s kind of technical. So, you just can’t throw rubber into asphalt.

**Doug Carlson:** A lot of testing and proving. So, that ultimately caused a lot of heartburn in the country nationwide because a lot of contractors and states tried technologies that were not yet proven to work. So, they experienced a lot of early failures.

**Craig Hunter:** Any funny stories there? Any that you saw that you witnessed that might have been just totally bonkers?

**Doug Carlson:** Uh, well, you know, 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. So, one contractor used buffings from a retreading operation. When they put it in the road and paved it, come back the next day, and it looked like it needed to shave. All the buffings were sticking straight up in the air.

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

**Doug Carlson:** Yeah. So that was a bonkers kind of thing. And what we’ve heard from, you know, other presenters is that can be a real big oops. 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.

**Craig Hunter:** Yeah, that does happen. So, specifications are important. The size of the rubber particle that you use and put in the mix is important. So, people need to be aware of that and understand the relationship between the rubber and the asphalt in the hot mix especially.

**Doug Carlson:** Yes, for sure. So, we’re experiencing kind of a resurgence of what is called the dry process where rubber is added to the mix directly 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, and the technology has vastly improved over the early days of the dry process. So, now we use a real fine grind rubber, 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. That has been a technical advancement to the technology, which I call the next generation dry process.

**Craig Hunter:** Okay. All right. I like that. And there are a few technology providers that help create additives that make it more effective and more efficient.

**Doug Carlson:** Yes. With warm mix technology, trying to reduce the overall temperature of the asphalt paving material. You can compact it at a lower temperature, which reduces emissions and less oxidation of the asphalt. The more you cook asphalt, the worse it gets; you kind of cook all the good stuff out of it.

**Craig Hunter:** Yeah, and more fumes come off of it. That makes perfect sense.

**Doug Carlson:** Yes. Warm mix additives were big in the early 2000s and helped a lot with the next generation dry process. The additives have made using rubber easier for the contractor, solving problems specifically through warm mix processes. They help reduce the stiffness of the mix when compacting it, making it easier to roll and compact in place, enhancing the material quality as well.

**Craig Hunter:** You mentioned the dry process using a little less rubber. Does that turn off Liberty or some of these other folks, or is it still enough volume to make it worth it?

**Doug Carlson:** Yes. The dry process still requires enough rubber to move the needle. I grew up in the wet process industry, which can use three times more rubber than the dry process. However, it has a lot of complications in the supply chain. You have to work with blenders and terminals and create a modified liquid that you have to keep heated and agitated, making it very complicated. But it still makes a premium product.

**Craig Hunter:** Gotcha. But it’s still making the mix producers use a special type of mix. They have to change their aggregate stock piles.

**Doug Carlson:** Yep. Mix plants do the same thing with aggregate. When you require changing aggregate stock piles, mix producers aren’t very happy about that approach. The advantage of the new dry process is that it can go into just about any standard mix, meaning even though you’re using less rubber, you have more opportunity to use rubber everywhere. Instead of going to one plant only with a special mix, you can go to every plant in the country and use their standard mixtures. The potential upside with the new dry process is enormous, which is what attracted Liberty to support it.

**Craig Hunter:** A little detour here—my kids would call them dad jokes—but the chip seal program, we have tons of it going on in Idaho. How does rubberized chip seal work, and what are the recent developments?

**Doug Carlson:** Chipsel is where rubberized asphalt, or asphalt rubber, started. It was the first widely adopted pavement system in the country and worldwide. Hot applied asphalt rubber binder uses blenders and special distributor trucks to spray the liquid membrane on the ground. It creates a real thick membrane about 6/10 of a gallon per square yard, almost half a jug of milk per square yard.

**Craig Hunter:** And it also is thick in terms of viscosity so it doesn’t run away. It stays where you spray.

**Doug Carlson:** Exactly. That’s why it creates an awesome pavement sealant. The chip part is dropping stone rocks on the top of the membrane while it’s still hot. It embeds the stone chips to create a driving surface that’s not slick. You have stone aggregate that gives you better friction characteristics with the tire rubber and also keeps the tires off the membrane, riding on the rocks.

**Craig Hunter:** Rollers have to go on immediately after that, right?

**Doug Carlson:** Yes, to seat the aggregate. So the hot applied asphalt rubber chip seal cures very quickly. As soon as it cools down, it becomes a very firm and hardened material, which is very appealing due to its thickness and durability. It offers at least double the life compared to conventional material and sometimes even five times the life cycle.

**Craig Hunter:** So you’re standing in front of the decision-makers. Are those the things you’re talking about—the life cycle cost?

**Doug Carlson:** Yes, absolutely. You’re going to save money by not having to maintain that roadway year after year. With a rubberized chip seal, you extend to a longer life cycle, like ten years. It really stretches and saves your pavement maintenance budget. The other benefit is these membranes can go onto pavements in much worse condition, which standard chip seals can’t handle.

**Craig Hunter:** You’re able to save roads that might have been viewed as ready to be milled or even returned to gravel roads. That’s great for rural communities with budget constraints.

**Doug Carlson:** Exactly. Rural communities can benefit greatly, allowing them to maintain roads without converting back to gravel. It’s noisy and creates a lot of dust, so maintaining paved roads is not only a cost-saving measure but also a way to improve the quality of life for the people living and traveling on those roads.

**Craig Hunter:** What’s the future hold for rubber-modified asphalt?

**Doug Carlson:** There’s a lot of momentum pushing toward more use of rubber in roads, driven by cost reductions and improvements in technology. The commercial paving side of the business is growing with rubber-modified asphalt because of its environmental benefits and extended lifespan. Many commercial enterprises are now more interested in maintaining their pavement since they own the properties.

**Craig Hunter:** Right, there’s a lot of commercial asphalt with large parking lots like Walmarts, Home Depots, Lowe’s…

**Doug Carlson:** Yes, those big parking lots can benefit significantly from rubberized asphalt. They can use over 20,000 scrap tires in a thin surface treatment, which not only moves a lot of rubber but also promotes environmental stewardship.

**Craig Hunter:** Anything else you’d like to add?

**Doug Carlson:** I think we covered it pretty well. Thank you for having me on Talking Tires. It’s been great sharing about the advancements and potential of rubberized asphalt.

**Craig Hunter:** Thank you, Doug, for the insights. I’m really excited about the future, and Liberty Tire will continue to play a crucial role. Thanks for being here.

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

**Craig Hunter:** Take care.