Welcome to Mixing Materials, a podcast that is dedicated to professionals in the construction materials industry! Whether you work in a construction materials testing lab, as a civil engineer, or in materials production, this podcast connects you with experts who share valuable industry knowledge and personal experiences.
Our interviews go beyond technical discussions—while we cover topics that impact your daily work, we also dive into the stories, career journeys, and perspectives of the people shaping the industry. Mixing knowledge with personality, we bring the construction materials community closer together.
Caltrans Specs: RAP, Asphalt Rubber, and What’s Next
In this episode of Mixing Materials, Dan Ridolfi sits down with Brandon Milar, Director of Technical Services for the California Asphalt Pavement Association, for a wide-ranging conversation on the rapid evolution of California’s asphalt specifications. Brandon breaks down major changes coming from Caltrans—including post-plant gradation, increased use of RAP, recycled shingles, asphalt rubber innovations, and the move toward percent-within-limits and balanced mix design.
They also dive into the growing focus on sustainability, shifts in material supply, and how agencies and contractors are adapting to a faster pace of specification development. Beyond the technical side, Brandon shares stories from his career, reflections on industry mentors, and even the theme song he thinks best represents CalAPA.
If you want insight into where asphalt specifications, materials, and industry innovation are heading in California, this is a conversation you won’t want to miss.
WAPA Connections: Learning, Networking, and Growing the Industry
WAPA’s 65th Annual Conference & Business Meeting, Winter 2025
The Mixing Materials Podcast hit the road for the Wisconsin Asphalt Pavement Association Annual Meeting—and we left energized by the conversations. Host Dan Ridolfi sat down with WAPA members to dig into why they attend, what makes this industry so unique, and how the relationships formed here continue to strengthen the work we all do.
From industry advocacy to big-picture trends, the insights shared were a powerful reminder of what truly drives this industry.
Don’t just take our word for it—hear directly from Rebecca Burkel and other WAPA members in their own words.
Building Better Roads: California’s New Asphalt Specs
In this episode of Mixing Materials, host Dan Ridofli sits down with Cameron Richardson, Director of Technical Affairs and Asphalt Advocacy for the California Construction and Industrial Materials Association (CalCIMA). Cameron brings over 20 years of asphalt and quality control experience to the table, and in this conversation, he helps break down some of the most important specification changes happening in California’s paving industry — and what they mean for producers, engineers, and local agencies.
Topics Covered:
00:04 Post-Plant Gradation: What it means, how it changes quality control, and why it matters.
17:05 Rubberized Asphalt with RAP: How Caltrans and CalCIMA are integrating recycled pavement and ground tire rubber for more sustainable roads.
22:28 Balanced Mix Design (BMD): The future of performance-based specifications in California.
27:43 Industry Collaboration: The role of CalCIMA, Caltrans, and research institutions like UC Davis Pavement Research Center.
29:15 Personal Insights: Cameron’s journey in the materials industry, mentors who shaped his career, and what makes CalCIMA such a unique organization.
High Levels of Safety Equals High Levels of Quality
Interview at Petersen Asphalt Research Conference
Annual Meeting, Summer 2025
We’re coming to you from the Petersen Asphalt Research Conference in beautiful Laramie, Wyoming — cowboy hats, sunshine, and all.
Stacy, Ann, and Matthias dive into one of the most important and often overlooked topics in the construction materials industry: laboratory safety. From solvent handling to automation and PPE, they explore how innovation, training, and communication can help protect technicians and improve asphalt quality worldwide.
Attending with Purpose: Taking AAPT Ideas Back Home
Interview at Association of Asphalt Paving Technologists (AAPT)
Annual Meeting, Winter 2025
On this episode of the Mixing Materials Podcast, we sit down with Elizabeth Pastuszka from the Asphalt Pavement Association of Indiana (APAI) and Debbie Schwarman from the Wisconsin Asphalt Pavement Association (WAPA) for a candid and insightful conversation about leadership, innovation, and collaboration in the asphalt industry.
From the impact of highly modified asphalt (HiMA) to the value of practical research, we explore how these industry leaders are bringing cutting-edge ideas back to their states. They also share what drives their passion for pavement, how they stay connected in a close-knit industry, and what they'd like to see more of at future meetings.
Whether you're in the field, the lab, or just asphalt-curious, this episode is full of experience, energy, and great stories.
Interview at Association of Asphalt Paving Technologists (AAPT)
Annual Meeting, Winter 2025
Ever think, "I can't believe this is my job"?
In this episode, Yogesh Kumbargeri, Lead Research Engineer at Western Research Institute, shares what it’s like to lead the Petersen Asphalt Research Conference, from in-depth technical planning to choosing the wine for the welcome reception. He reflects on the conference’s rich history, its uniquely welcoming atmosphere, and how it brings the entire asphalt industry together in Laramie, Wyoming.
Yogesh also shares who he’d most like to grab a coffee, beer, or hike with—from current colleagues to industry legends.
The 2025 conference takes place July 14–17—don’t forget your hiking shoes!
Interview at Association of Asphalt Paving Technologists (AAPT)
Annual Meeting, Winter 2025
In this episode, we dig into the future of asphalt—yes, really. Yogesh Kumbargeri joins us to unpack a surprisingly urgent and fascinating topic: alternative binders. As we transition away from fossil fuels, what happens to the oil-derived asphalt we rely on for roads, roofs, and runways?
Kumbargeriexplainswhat alternative binders are (spoiler: they’re often bio-based), why they matter in 2025 and beyond, and what his early research reveals about how these new materials behave. From chemistry surprises to the surprising lack of that familiar "asphalt smell," we explore why simply swapping in new materials isn’t so simple—and why getting it right matters for both the planet and the people working in the asphalt industry.
We also discuss the challenges of scaling from lab to road, the need for new specifications, and the social side of sustainable innovation. Oh, and yes, there’s a quote instead of a theme song: "Don’t judge a book by its cover."
If you're into climate tech, infrastructure, or just love a good "it looks like asphalt but isn't" story, this one’s for you.
