CHIP SEAL
Chip Seal
Chip Seal

Chip seals are an effective maintenance tool for restoring a wearing course to a pavement. As a preventive maintenance tool, chip sealing prevents ingress of moisture into a pavement or base course and can prevent deterioration due to oxidative aging of a pavement. Emulsions for chip sealing include cationic polymer-modified formulations. Because many different geologic types and gradations of cover aggregate are used for chip sealing (single size, graded, hard, porous) the emulsion should be selected to accommodate the aggregate in a performance system.

Ideally, chip seals should be applied when a road is still in good condition, with only minor surface problems, such as loss of friction, drying surface or very minor cracking.  They may also be applied as a wearing surface over a prepared base on rural roads.  Chip seals are an excellent choice for keeping good pavements in good condition. The Strategic Highway Research Program found chip seals, which are a relative low cost treatment, to be one of the most cost-effective pavement preservation treatments
 

Equipment: Chip sealing utilizes Bitumen emulsion distributor trucks, chip spreaders designed and calibrated to deliver accurate quantities of chip, pneumatic rollers, and brooms for removal of excess chip. Steel wheeled rollers may be used on multiple application chip seals to “rack-in” aggregate.
 
Chip seals have been successfully applied on all types of bituminous pavements, from low volume rural roads over a prepared base to heavily trafficked superhighways over hot mix asphalt.  The road should be structurally sound with only minor surface defects.
Chip Seal
Estimated life extension: 6-8 years over pavements in good condition; 4-6 years on pavements in fair condition; 3-4 years for pavements in poor condition.
 
Aggregate: Aggregate gradation and size are important to the success of Chip Seal. Aggregates typically used include natural gravel or crushed stone. These must be clean and dust free, hard, and uniform. This is to provide a durable surface for traffic. It is common to limit the percent of material passing the No. 200 sieve (0.075 mm) to about 1 percent or less. Aggregate containing dust must ‘‘not’’ be used for Chip Seal. Dust will prevent the aggregate from bonding to the bitumen binder and will create problems with excessive chip loss.