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New asphalt binder alternative is less toxic, more sustainable than conventional blend

September 18, 2023

Bio-based patch from ASU will lead to safer travels and recreation

Asphalt is primarily known for use in roadways, but it's also used to pave playgrounds, bicycle paths, running tracks and tennis and basketball courts — all platforms for activities where breathing toxic fumes can be dangerous. Outdoor use on driveways, rooftops and parking lots, especially in the Arizona sun, also can lead to toxic fume exposure.

A team from Arizona State University, led by Associate Professor Ellie Fini in the School of Sustainable Engineering and the Built Environment (SSEBE), has developed AirDuo, a new, patent-pending asphalt binder that not only diminishes toxic fumes of the overall asphalt-surfaced area, but also increases sustainability. 

But perhaps most importantly for Fini, it reduces health hazards for those exposed to asphalt-surfaced areas, especially for those performing the installation.

AirDuo's first local trial was initiated in late August as a patch in ASU's Gammage Auditorium parking lot. Frank Castro, associate director of Facility Maintenance, helped get the research out of the lab and into the parkig lot, facilitating the lab-to-market transition. On the morning of the install, the Parking and Transit Services team, led by Assistant Manager David Triana, completed the patchwork in a few hours.

Attendees of a theater production at Gammage the same night gave the patch a workout as they arrived and departed, and Castro reported to Fini the next day that the patch had “held up great.”

Fini envisions the new low-carbon, bio-based binder will ultimately be used for all asphalt paving products, not just patches.

The U.S. Department of Labor’s Occupational Safety and Health Administration notes that about a half-million workers annually are exposed to fumes from asphalt, with health effects that include headache, skin rash, fatigue, throat and eye irritation, cough and skin cancer.

Asphalt binder is the glue that holds together the stones, sand, gravel and other aggregates in asphalt pavements. The AirDuo binding mixture is composed of low-carbon, bio-based materials that are an alternative to more toxic petroleum products, also known as bitumen. Moreover, AirDuo acts as a toxicity filter for the overall product.

After the traditional blend of aggregates and binder is laid on the roadways, the stress from heat, sun, weather and traffic causes the release of breakdown products — molecules that vaporize — some of which are odorous, highly toxic or both.

“We breathe 11,000 liters of air per day,” Fini said. “But our nose isn’t smart enough to know when the air may be dangerous for our health. That new-car smell people like? That may not be good for your lungs. We run away from a smelly trash can, but the pleasant smell or fumes from certain materials can be far more toxic.”

Fini and Judith Klein-Seetharaman, a professor in both ASU’s College of Health Solutions and School of Molecular Sciences, collaborated to review literature about the health effects of various asphalt mixtures and mapped the effects on a network of biomarkers. Citing specific contaminants present in asphalt, the team discovered that all are not created equal and that different formulas have different levels of toxicity — the majority of which have not been studied comprehensively.

According to Klein-Seetharaman, there have not been sufficient studies of the long-term effects of asphalt-related toxins on the body.

“To give justice to the complexity of the problem, we need a systems-level view of the interactions between asphalt fume components and their biological targets,” Klein-Seetharaman said. "There are thousands of molecules present in asphalt, as well as thousands of biomolecular targets inside the human body that can bind to these molecules and respond to their presence with downstream biological effects, some of which can lead to adverse health outcomes.”

Fini has conducted ongoing research to investigate alternative asphalt binders, including a study on how iron-rich biochar absorbs volatile organic compounds from asphalt surfaces, and how it is both an eco-friendly and cost-effective alternative to bitumen components.

“When we use algae to make AirDuo, as we did from last year’s November harvest from ASU’s Center for Algae Technology and Innovation (AzCATI), it can be carbon negative,” said Fini, who collaborated on the algal components of the project with Peter Lammers, a research professor in SSEBE; Taylor Weiss, a Polytechnic School assistant professor; and Shuguang Deng, a professor in the School for Engineering of Matter, Transport and Energy (SEMTE).

“The use of algae in the AirDuo binder provides a critically important environmental benefit,” Lammers said. “As algal photosynthesis removes carbon dioxide from the air, the AirDuo manufacturing process retains that carbon in an improved asphalt product relative to petroleum-derived binders.” 

“We plan to scale up the process by growing algae on wastewater, thus providing an additional ecosystem service," he said of future plans for substituting algae for petroleum products in other roadway projects.

Other bio-based materials the team has used include biochar from fire-reduction efforts in California and northern Arizona. Process sustainability depends on the feedstock sourcing and, in the case of AirDuo, the use of biomass waste from forest residue, according to Fini.

“This promotes resource conservation and waste valorization, as well as enhances public health and safety — all while providing a more sustainable pavement material.”

SSEBE Professor Mahour Parast oversaw sourcing and supply chain to enable scale-up for AirDuo. DPE Materials, the team’s partner based in Yuma, brought 10, 40-pound bags of AP1 (AirDuo Paving) for the patch at Gammage.

“AirDuo represents a complete sustainability package,” Fini explained. “We are using biomass as our feedstock — it has already pulled CO2 from the air prior to harvesting. The AP1 helps create a sustainable built environment and provides reduced health risks to both asphalt workers and those using asphalt-surfaced areas.”

Fini’s lab studies showed a nearly 70% reduction in emission when AirDuo was used. While not a one-to-one translation to the field, according to Fini, it clearly illustrates toxic fume reduction. The mix also had notably less smell than any other mix made in the plant. 

The research on bitumen asphalt binder alternatives began with a 2019 grant from the National Science Foundation on algae-derived products. A grant from the U.S. Department of Agriculture with a focus on emission reduction and environmental health supported the research and also helped with the lab-to-market transition.

“Our next steps are larger projects on the ASU campus, and then perhaps in Flagstaff and Tucson. Our team invites other states and institutions to join the AP1 (AirDuo Paving) campaign and test it on their sites, too,” Fini said.

But Fini and her team are delighted ASU is leading the effort. 

“It is an Arizona-born technology inspired by Arizona’s sun and heat,” Fini said. “Arizona is ideal for growing our feedstock algae, and also a great testbed for AirDuo. With 320 days of sun in the Valley, the smell of asphalt-surfaced areas never stops.

“You can verify this the next time you get out of your car in an open parking lot in summer.”

SSEBE students and postdocs engaged with AirDuo research include Sand A A Aldagari, Abdullah Aloraini, Mohammadjavad Kazemi, Anna Melis, Masoumeh Mousavi, Albert Hung and Farideh Pahlavan.

Top photo: ASU’s Ellie Fini surveys the ASU Gammage Auditorium parking lot site where the first trial of AirDuo, a low-carbon asphalt binder, was used for a recent patch. AirDuo has the potential to be used for many asphalt paving processes, not just patches. Photo by Bobbi Ramirez/ASU

ASU’s Institute for Humanities Research announces 2023 book award winner

Professor Patrick Bixby's ‘License to Travel’ examines what passports reveal about identity, mobility, citizenship and state authority

September 18, 2023

Arizona State University’s Institute for Humanities Research (IHR) has announced “License to Travel: A Cultural History of the Passport” (University of California Press, 2022) by Patrick Bixby as the 2023 IHR Book Award winner. Bixby is a professor at ASU’s School of Humanities, Arts and Cultural Studies. 

Established in 2008, the annual award celebrates outstanding writers whose contributions to the humanities change the conversation by fostering new directions for their discipline. The nonfiction humanities-based books are judged by the IHR committee. Every odd-numbered year, the IHR Book Award is presented to an ASU faculty member who has published a work in the last two years. On alternate years, the award goes to a national, non-ASU-authored book.   Cover of the book "License to Travel" next to a black-and-white portrait of ASU Professor Patrick Bixby. Download Full Image

“We are thrilled to give this award to Professor Bixby,” said IHR Director Ron Broglio. “The committee looks for a book that is accessible to a wide audience, works across humanities disciplines, shows strong research and provides new ways of seeing a topic. ‘License to Travel’ is that book, and the IHR is proud to present the award to Professor Bixby for his gifted storytelling through the cross-cultural lens of the passport.”

Bixby’s scholarly interests span a variety of related fields, including mobility studies, modernist studies, Irish studies, and postcolonial theory and criticism. He teaches courses in these areas and in the history of the novel, the history of film, the history of literary criticism, contemporary critical theories, and methods of interdisciplinary research. In “License to Travel,” Bixby examines the passports of artists and intellectuals, ancient messengers and modern migrants to reveal how these seemingly humble documents implicate us in larger narratives about identity, mobility, citizenship and state authority.

This cultural history takes the reader on a captivating journey from pharaonic Egypt and Han Dynasty China to the passport controls and crowded refugee camps of today. Along the way, the book connects intimate stories of vulnerability and desire with vivid examples drawn from world cinema, literature, art, philosophy and politics, highlighting the control that travel documents have over our bodies as we move around the globe.

Ranging broadly through time and space, Bixby explores archives, works of literature, films and even internet myths in this engaging work that insists we contemplate how passports generate and foreclose possibilities. As Bixby writes, “Now, more than ever, we are our documents: They tell the world who we are, where we come from, and where we can go.” With unexpected discoveries at every turn, "License to Travel" exposes the passport as both an instrument of personal freedom and a tool of government surveillance powerful enough to define our very humanity.

The two shortlisted titles this year are "Sonic Overload” (Oxford University Press) by Peter J. Schmelz, professor, School of Music, Dance and Theatre, and "Unshaved: Resistance and Revolution in Women's Body Hair Politics” (University of Washington Press) by Breanne Fahs, professor, School of Humanities, Arts and Cultural Studies.

The annual IHR Book Award Ceremony will take place from 4 to 6 p.m. Thursday, Oct. 12, at Ross-Blakley Hall on the Tempe campus.

>>LEARN MORE: Read The Wall Street Journal’s review of “License to Travel,” listen to Bixby’s interviews on KJZZ and KQED, watch his Tedx Talk and read previous coverage on ASU News.

Mina Lajevardi

Marketing and Communications Specialist, Sr., Institute for Humanities Research