As defined by the International Slurry Surfacing Association (ISSA), Chip seal is an application of a bituminous binder covered with an application of clean graded aggregate to an existing asphalt surface. It is also known as armor coat, bituminous sealing or seal coat, to name a few. The binders may be versions of each being modified with various polymers such as latex, tire and natural rubbers. The aggregates commonly vary in size from a maximum of 5/8 of an inch to a minimum of 1/4 of an inch with less than 5% passing the No. 4 screen. Aggregate must be durable with the use of crushed stone, gravels or manufactured aggregates.
Chip seal has been used in various forms since at least the early 1900′s. The quality has improved over the years with better binder technology, cleaner aggregates, and improved equipment and a better understanding of how the materials perform together. It is worth noting, that the advent of polymer modified emulsion has increased the adhesion properties of the chip seals.
There is virtually an unlimited number of chip seal combinations depending on what type of binder and aggregate are available. Chip seal is normally one application but can be applied in double or even triple applications if needed. Multiple applications commonly use different sizes of aggregates to help “lock” the applications together.
When the owner agency requires a smoother wearing course on an existing surface treated road, a thin slurry or micro surfacing can be applied to the top of existing surface treated road. This process is referred to as a Cape Seal.
Chip seal is a comparatively low cost method of maintaining an asphalt surface indefinitely that can make use of local materials, and be performed by contract or by using local maintenance personnel. Traffic can be back on the road in minutes. A finished chip seal is very pleasing in appearance and traffic markings show up very well.
State route being chip sealed
Emulsion being applied prior to chip spreading
Applying a second coat of emulsion
Chip application
