Asphalt surface seals are defined herein as slurry seals, micro-surfacings, and chip seals (seal coats). The objective of this study is to estimate, by laboratory testing, the relative aging abatement effects of surface seals on the upper 13 mm of an asphalt pavement.

A surface seal can retard oxidative hardening of an underlying asphalt concrete layer by 0 to 2 years, depending on the situation. However, most of the oxidative aging in the upper stratum of an asphalt concrete pavement occurs during the first 4 years after construction. Therefore, in order for a surface seal to significantly delay oxidative hardening of the underlying pavement, it must be placed during the first two years (approximately) of the pavement's life. Ultraviolet (actinic) light penetrates asphalt cement only a few microns and, therefore, does not contribute materially to hardening of the uppermost 13 mm of an asphalt concrete pavement. For practical purposes, these three surface seals will protect the top 13 mm of an underlying pavement from oxidation as if they were impermeable to air and water.