Chip seals, also known as seal coats or surface treatments, are a valuable preservation treatment for roads which receive light to medium traffic; they have also performed well on higher-volume roadways and are usually placed on an existing asphalt pavement.
Chip seals are placed by spraying the pavement with a binder, either an asphalt emulsion or a hot applied binder, from a distributor truck, and then immediately applying a uniform application of a cover aggregate (chips or screening) using a self-propelled chip spreader. The aggregate is rolled as soon as possible to ensure embedment and adhesion of the aggregate to the fresh binder.
Chip seals can be placed in single or multiple layers, usually using 1/4 to 1/2 inch aggregates. On multiple chip seals, the binder and aggregate application process is repeated, with the aggregate size declining with each application. Only clean and well-crushed aggregates should be used in chip seals. They should only be placed in warm weather, and traffic needs to be controlled until the chips are well adhered to the pavement surface. Excess loose aggregate should be swept after placement in order to avoid windshield and vehicle damage.
This report presents the best practices for construction of chip seals, including scrub and Geosynthetic Reinforced Chip Seals (GRCS), and also includes guides for troubleshooting problems. It also includes information on the design of chip seals as well as guide specifications for both emulsion and hot applied chip seals.
R. GARY HICKS, PhD, PE
Dr. Hicks is currently program manager for the CP2 Center at CSU Chico. Prior to joining the Center, he taught at Georgia Tech and Oregon State University for 30 years, rising to the positions of Distinguished Professor of Civil Engineering and Associate Dean for Research for the College of Engineering. He retired from OSU in 1997, and upon retirement embarked on a consulting career with MACTEC Engineering (now Wood LLC), providing on-call consulting services to the California Department of Transportation and other organizations. As a part of this consulting project, he led the development of the MTAG and helped set up the CP2 Center in 2006. He is a registered Civil Engineer in the states of California, Oregon, and Alaska.
DINGXIN CHENG, PhD, PE (TEXAS), PROFESSOR AT CSU CHICO
Dr. DingXin (Ding) Cheng is a professor of the department of civil engineering at the California State University, Chico, director of the California Pavement Preservation (CP2) Center, and the director of the Tire Derived Aggregate Technology Center. He has worked actively with the CP2 Center since he joined the department of civil engineering of CSU Chico in 2006. He obtained his PhD in the areas of pavement materials and transportation from Texas A&M University in College Station, Texas in 2002. He worked in private industry for Parsons Brinckerhoff in Houston, TX before joining Chico State University. He has extensive experience in Hot Mix Asphalt (HMA) materials and pavement preservation on both asphalt and concrete pavements. He has more than 55 peer-reviewed publications related to pavement materials and preservation in Transportation Research Board, AAPT, ASCE, and other conferences. Ding has co-managed or managed more than $7 million research projects funded by California Department of Transportation (Caltrans), California Department of Resources Recycling and Recovery (CalRecycle), Metropolitan Transportation Commissions (MTC) of San Francisco Bay Area, and other agencies and industry leaders. He is a registered professional engineer in the State of Texas.
LEROSE LANE, PE, SENIOR PAVEMENT PRESERVATION ENGINEER
Lerose Lane, PE, is a Senior Pavement Preservation Engineer who has worked for the California Pavement Preservation Center (CP2C) since August 2010. Her work includes observing pilot project construction for a wide variety of preservation strategies including Rubberized Chip Seals, Scrub Seals, Reconstruction with Rubberized Hot Mix Asphalt Concrete, and Double Chip Seals. Besides observing and evaluating construction and long-term performance of this wide variety of preservation strategies, she co-authors many of the technical reports regarding the construction phases and the follow up inspection reports. Most of these projects are Caltrans projects on California State Highways or Interstate Routes. She graduated from CSU, Chico, in 1970 with a B.S. degree in Civil Engineering. Since that time, she has worked for UCD, City of Marysville, County of Tehama, and Caltrans in various capacities, including: District Materials Engineer, Office Chief in Design, Senior Construction Engineer, as well as Resident Engineer for a wide variety of projects. She has been a Professional Engineer in the State of California since 1975.