Study of Long-Term Field Performance of Chip Seal in Washington State

Chip seal is a pavement preservation treatment that is usually used on lower-volume routes by States and local agencies. Chip seal provides a low-cost surface treatment, improves skid resistance, and reduces the deterioration of the existing underlying pavement. Chip seals consist of a layer of aggregate (chip) spread evenly on top of an emulsion that is sprayed onto the deteriorated surface. The performance of chip seals is significantly affected by the existing conditions and pretreatment carried out before the chip seal is applied. A study was conducted by retrieving long-term performance of chip seals from the Washington pavement management system (WSPMS). In collaboration with Washington State Department of Transportation (WSDOT), twelve (12) road sections previously paved with hot mix asphalt (HMA) or chip seal and later maintained with chip seal were selected, and their performance was analyzed in terms of cracking, rutting, and roughness index (IRI). It was found that chip seal greatly reduced the cracking and slowed down the crack growth when compared to HMA overlay. However, no improvement in rutting or international roughness index (IRI) caused by the chip seal was found.