This is the first in a series of technical presentations the Association of Modified Asphalt Producers is releasing for public viewing.
These presentations were made at the 2018 AMAP Conference and are normally only available to conference attendees and AMAP members. View 2018 list of presentations. To access presentations, log into your account or become an AMAP member.
“Roofing Asphalt Characterization” Presentation by John Casola
Although the history of the scientific study of the flow of matter is replete with names of our greatest thinkers, from Aristotle, Galileo, and Newton to Maxwell, Edison, and Einstein, the term “rheology,” like the science itself, was arguably born in the early twentieth century. The English-speaking world attributes the creation of the term, “rheology,” to E.C. Bingham and J. R. Crawford in 1929, although the word had been in use in German scientific literature as early as 1901 (the French limnologist, Francois Alphonse Forel, used the term casually in a journal article, suggesting its meaning was commonly understood then).
The theoretical foundations laid by these brilliant minds of the past notwithstanding, it is the development of highly advanced and affordable rheometric analytical instrumentation that has given engineers and scientists the penetrating insights and understanding we enjoy today of the indisputable links between the molecular-level physical chemistry of bituminous materials and their multifarious viscoelastic behavior under static and dynamic stresses and deformations. Longer-lived, more durable, and increasingly cost-effective pavements and roofing materials are the direct products of these advanced rheometric capabilities.
John Casola, life-time member of AMAP and rheologist for Malvern Panalytical, Inc., gave a presentation on advancements in the rheological characterization of modified bitumen both to the AMAP conference audience as well as to the workshop attendees. His seminars were so well received that Mike Andersen, Director of Research and Laboratory Services at the Asphalt Institute, invited John to present at this past Spring’s Asphalt Institute meeting in Savannah, and Reed Hitchcock, Executive Vice President of the Asphalt Roofing Manufacturers Association, has requested John for a presentation at their meeting next week in Tampa.
“Arizona DOTs use of Modified Binders”
Presentation by Julie Kliewer
Arizona Department of Transportation (DOT) is one of the country’s largest users of ground tire rubber (GTR)- modified asphalt. That fact is easily understood given that many asphalt technologists today attribute the origins of modern GTR-modified asphalt to Charles MacDonald, an engineer from the city of Phoenix, who developed easy-to-produce and long-lasting rubber-modified bitumen formulations in the 1960’s.
Today, according to Asphalt, the Magazine of the Asphalt Institute, “the Arizona DOT started using an asphalt rubber (AR) program in 1988. They have used more than 4.2 million tons of AR in their paving projects since 1988, valued at $225 million and resulting in the recycling of 15 million old tires.”
At the 19th Annual AMAP conference in Phoenix, February 2018, Julie Kliewer, State Construction and Materials Engineer at Arizona DOT, presented our audience with a very thorough overview of the development and current state of GTR usage in Arizona. She covered two predominant formulations: CRA and TR+ (the latter being a hybrid of wet-processed GTR and SBS). She described current levels of rubber-modified bitumen production, the different mixture designs that the DOT specifies for Arizona’s hot and cold climates, and the future perspective for this proven modified bitumen technology.
According to the U.S. Census Bureau in 2017, Phoenix was the fastest growing city in the USA. Heavy traffic and temperature extremes (from 46-49°F average lows in January and February to 104-106°F as average highs in July and August) combine to be the true judges of a pavement performance.
Julie’s presentation highlighted many of the proven benefits of rubber-modified bitumen in Arizona, such as improved rutting resistance, ride quality, lower noise and higher skid resistance, to name a few. If you would like to learn more about how highly durable pavements can be designed and constructed using the sustainable and proven technology of rubber-modified asphalt, please see Julie’s presentation.