Asphalt Pavement Magazine - July/August 2015 - (Page 42)

Improving the Longevity of POROUS FRICTION Course The importance of the interface bond on performance By Nam H. Tran, Ph.D., P.E., LEED GA O n average, nearly 1.3 million weather-related crashes occur each year, killing more than 6,000 people and injuring more than 480,000 people. The majority of these crashes - 74 percent -happen on wet pavement, and 46 percent happen during rainfall.1 To reduce the impact of wet weather conditions on road safety, transportation agencies, especially in the southern states, have used porous friction course (PFC), also known as open-graded friction course (OGFC), as the final riding surface. With a high air void content, PFC has the ability to quickly drain water through the surface to an impervious intermediate layer below, and then out to shoulders, which help improve friction, minimize hydroplaning, and improve visibility by reducing tire spray. In the field, the effectiveness of this strategy has been significant. After the Texas Department of Transportation placed a PFC as a safety measure on a 2-mile section of RM 1431 near Jonestown, the number of wet-weather accidents decreased by 93 percent compared to the multiple- 42 * View past issues online at year accident reports collected before the placement of PFC.2 NCAT Studies Over the past decades, the service life of PFC has been improved significantly with the use of polymer-modified asphalt binders, stabilizing fibers, and hydrated lime, which has proved beneficial for some asphalt/ aggregate combinations. However, there are concerns that PFC still does not perform as well as other asphalt mixtures with a greater incidence of raveling and cracking. To continue improving the longevity of PFC, the National Center for Asphalt Technology (NCAT) has conducted several studies at their pavement test track. Two of these studies, sponsored by the Florida Department of Transportation (FDOT), focused on the interface bond between the PFC and underlying layers. The first study was conducted on Sections N1 and N2 in the 2009 test cycle, and the second study was performed on Sections N1A, N1B and N2 in the 2012 cycle. The five test sections shared the same pavement cross-section, which consisted of four

Table of Contents for the Digital Edition of Asphalt Pavement Magazine - July/August 2015

President’s Perspective
Industry News
Roads Built to Last
Intelligent Compaction Today
Rejuvenators: Bringing Life Back to Aging Asphalt Binder
Improving the Longevity of Porous Friction Course
Good Roads, Healthy America
NAPA and the Industry Care
Index of Advertisers/

Asphalt Pavement Magazine - July/August 2015